Final report to the Office of Scientific Authority of the US Fish and Wildlife Service
Dr. Daniel Gagnon
Groupe de recherche en écologie forestière Université du Québec á Montréal
10 May 1999
2. American ginseng population dynamics
3. Impact of harvesting on ginseng populations
4. Biological reasons why the harvest of wild ginseng is probably not sustainable
5. Socio-economic reasons why the harvest of wild ginseng is probably not sustainable
6. Sustainability? Evidence available and evidence needed
7. Recommendations for action
7.2. Inventory and monitoring
7.7. Genetic and other types of markers
7.8. Somatic embryogenesis
8. Monitoring wild ginseng populations
8.1. Two levels of monitoring intensity for two different purposes
8.2. Monitoring for general population trends
8.3. Monitoring for population dynamics information
8.3.1. Study population selection
8.3.2. Study population site and vegetation description
8.3.3. Demographic data sampling
188.8.131.52. Locating individual plants
184.108.40.206. Data collected for individual plants
220.127.116.11. Sampling date and frequency, and study duration
8.3.4. Field and laboratory seed germination trials
8.4. Overview of demographic analysis methods
Appendix 1: "Site and ecological data" field form
Appendix 2: "Vegetation data" field form
Appendix 3: "Ginseng data" field form
Figure 1: Example of a location map of individual ginseng plants within an intensively monitored population
Figure 2: Diagram of ginseng plant showing types of measurements needed for demographic analysis
Among species of concern to conservationists, American ginseng (Panax quinquefolius L.) is one of the few plant "flagship" species known internationally, and it is usually the only plant species mentioned in the company of tigers, rhinoceroses and whales. The species is listed in CITES Appendix II and global trade in its roots and rhizomes is regulated. American ginseng is designated as Threatened in Canada (COSEWIC) and no exportation of wild-harvested ginseng roots is allowed. The United States regulates American ginseng harvest and export under a national program established by the US CITES Authority, the US Fish and Wildlife Service.
The current knowledge about the population dynamics of American ginseng is briefly reviewed in this report, along with studies on the impact of harvesting on ginseng populations. There are no population dynamics data available for American ginseng in the core of its range, the central Appalachians. Only one study, done in Canada, has realistically analyzed the impact of harvesting on ginseng populations.
Although ginseng is harvested in the wild in the US, there is no systematic monitoring of wild populations. There are biological reasons, which are common to all slow growing forest understory herbs like ginseng, as well as present day socio-economic reasons, that raise some doubt about the sustainability of harvesting wild ginseng roots. These built-in impediments to sustainability are reviewed in this report. There is a multi-million dollar ginseng agricultural industry which may suffer future losses if natural populations, the gene pool of the species, were to disappear.
In spite of good indications that the reality of the field situation may be poor, accurate and detailed information is lacking in order to provide conclusive evidence of sustainability or lack of sustainability for wild ginseng root harvesting. Recommendations for action are provided in this report along the lines of possible regulations, monitoring, conservation, agriculture, partnerships and research, in order to improve the situation of American ginseng.
The major part of this report describes a two-tiered wild ginseng population monitoring program, and relevant field protocols, which should provide most of the answers needed to manage the ginseng resource for conservation, and perhaps continued harvesting. The monitoring program will yield population dynamics information from the high intensity monitoring of a smaller number of populations, and general population trends from the low intensity monitoring of a larger number of populations. Hopefully, this monitoring program will be implemented in partnership with the states and the US Fish and Wildlife Service, as well as other partners. A similar monitoring program is now being implemented in Canada (Quebec and Ontario) by A. Nault and the author.
Among species of concern to conservationists, American ginseng (Panax quinquefolius L.) is one of the few plant "flagship" species known internationally, and it is usually the only plant species mentioned in the company of tigers, rhinoceroses and whales. The species is listed in CITES Appendix II and global trade in its roots and rhizomes is regulated. American ginseng is designated as Threatened in Canada (COSEWIC), and in Quebec the species will soon be designated as Threatened under the Province's law on the Protection of Threatened and Vulnerable species. No exportation of wild-harvested ginseng roots has been allowed from Quebec since 1975, and from Ontario since 1989. The United States regulates American ginseng harvest and export under a national program established by the US CITES Authority, the US Fish and Wildlife Service.
The sustainability of American ginseng harvest in the United States is mostly evaluated through quantity of roots harvested each year and reported by the States. It can be generally observed that the average size of the roots is decreasing. However, there is no systematic monitoring of wild populations. Furthermore, although harvesting is allowed on many state lands, poaching of ginseng roots is widely reported in protected areas, such as the Great Smoky Mountains National Park. This illegal activity is a clear indication that protected areas are rapidly becoming the last refuge of appreciable populations of American ginseng, and this over its entire distribution range (evidence from GSMNP in Tennessee and North Carolina, also from Missouri, and Ontario and Quebec in Canada).
The population dynamics of the species are poorly known over most of its US range, even though such knowledge is the common basis for the management of any harvested wild species (for example, all big game and sports fishing species). Detailed population dynamics data for American ginseng are available for southern Quebec in Canada (Charron and Gagnon 1991) and a few Midwest States (Lewis and Zenger 1982, Carpenter and Cottam 1982).
The purpose of this report is to offer the benefit of my understanding of the American ginseng harvesting issue to the Office of Scientific Authority of the US Fish and Wildlife Service. This report is a review of what is known of the population dynamics of ginseng and of the impact of harvesting on the species. It is also an analytical review of the sustainability of harvesting wild ginseng, followed by recommendations for the monitoring and the conservation of the wild ginseng resource. The review analyzes all of the available information that is pertinent to the question of the sustainability of harvesting American ginseng from the wild in the US. The report also identifies the types of information that are still lacking in order to provide conclusive evidence of sustainability or unsustainability. Furthermore, recommendations for action are made along the lines of regulations, monitoring, conservation, agriculture, partnerships and research.
A two-tiered wild ginseng population monitoring program, and relevant protocols, is described in this report. This monitoring program will yield population dynamics information from the high intensity monitoring of a smaller number of populations, and general population trends from the low intensity monitoring of a larger number of populations. Hopefully, it will be implemented in partnership with the states and the US Fish and Wildlife Service, as well as other partners. A monitoring program of this type is now being implemented in Canada (Quebec and Ontario) by A. Nault and D. Gagnon.
A recent literature search of the last eleven years (1988 - 1998) revealed 336 references using the key word "ginseng". The vast majority of these references had a medical or clinical theme (many dealt with only Asian ginseng, or with individual ginseng chemical compounds), few were horticultural in nature, and even less where related to the topic of this report (i.e. genetics, ecology). The very few pertinent references found where already known to me (some of my own papers). It is therefore with high confidence that I propose this report as the complete current state of knowledge on American ginseng population ecology, harvesting impacts and monitoring.2. American ginseng population dynamics
American ginseng (Panax quinquefolius L.), is a herbaceous perennial endemic to North America, occurring exclusively in the Eastern Deciduous Forest (Greller 1988). This forest understory herb is long-lived, with a life expectancy of at least 60 years (Charron 1989). Large individuals will usually have several thick taproots, often forked, distributed along a narrow rhizome, with the largest taproot situated at its end. The rhizome is characterized by scars formed as a result of the annual abscission of the aerial stem. One aerial stem is produced per rhizome per year. Occasionally, two stems are produced (Lewis and Zenger 1982). This aerial stem appears after the forest canopy has closed in late spring, and varies in height between 7 cm and 40 cm. The mature plant has a whorl of leaves at its summit; each leaf consists of a petiole and three to five palmately compounds leaflets. The seedlings have only one leaf with three leaflets. Size and number of leaves increase with age and the plant does not flower until it has grown large enough to produce two leaves (Schlessman 1985, 1987). After a pre-reproductive period of 3 years and more (Charron 1989), they develop a solitary umbel. The flowers are small, hermaphroditic and autogamous (Schlessman 1985), and each can produce one to three seeds, enclosed in a pericarp which turns bright red when ripe. Fruits are mature beginning in August, and are likely dispersed by birds, although most fall to the ground near the parent plant. Seeds remain dormant in the soil for approximately 12 months before germinating, but the seedling will emerge only after another 8 months, in the spring. Vegetative propagation is possible through rhizome fragmentation, although this has rarely been observed (Lewis 1984).
All demographic studies of American ginseng have used the total number of leaves as the size variable (Carpenter and Cottam 1982; Lewis and Zenger 1982; Charron and Gagnon 1991). This variable is easy to measure in the field, even when total leaf herbivory has occurred. Anderson et al. (1984, 1993) showed that the number of leaves is a good estimator of the biomass of the underground structures, and therefore of the size of a ginseng plant.
Lewis (1988) inferred that ginseng may form a seed bank, although the number of seeds involved is probably small and viability is of short duration. A garden germination experiment failed to detect any dormancy exceeding 20 months in a sample of 180 seeds (Charron 1989). This experiment confirmed the normal 20 month dormancy of ginseng seeds, between dispersal and the first appearance of the seedlings. However, wild leek (or ramp, Allium tricoccum) has a very similar seed germination pattern, and some extended dormancy was observed under certain conditions (Nault and Gagnon 1993). For example, a summer drought, drying up the humus layer where the dormant seeds are located, extended dormancy for another 12 months (seedlings appeared one year later than expected). A few seeds had their dormancy extended 24 months. Each additional year of dormancy in the soil adds to the probability of mortality of the seeds. Extended seed dormancy (past the normal period) is thus expected to be a rare occurrence in American ginseng.
When the plants in a population are represented in a size structure diagram (number of plants per size-class), a pattern typical of most populations is observed (White 1988; Charron and Gagnon 1991). In undisturbed populations, the size-class 3 individuals (three-leaved plants) will be the most abundant, followed next in abundance by seedlings, and some size-class 4 plants (four-leaved) are always present. Overall, there is a net dominance of individuals of reproductive size (size classes 2, 3 and 4) over non-reproductive individuals. Also observable from size structures is the large annual variation in seedling recruitment. The classic size structure is modified by harvesting, and therefore becomes a good indicator of this type of disturbance. Populations that have suffered harvesting have no size-class 4 plants (the obvious target of all harvesters), and few or no plants of size-class 3. Only small plants are left (seedlings, one-leaved and two-leaved plants). This pattern is evident in all harvested ginseng populations seen in Quebec (Nault and Gagnon 1998) and in Ontario (Nault et al. 1998).
Annual mortality for seedlings varied in the Quebec populations from 69% to 92%, but the larger individuals (size-classes 3 and 4) had lower than 10% annual mortality (Charron and Gagnon 1991). Flowering occurred in most individuals of size-classes 3 and 4, whereas only half of size-class 2 plants flowered. Individuals of size-class 1 and seedlings do not flower (with rare exceptions). Seed production is almost entirely limited to size-classes 3 and 4 (Charron and Gagnon 1991).
The growth rates of four Quebec populations were calculated using transition matrices. Three of the populations had annual growth rates of 0.99 to 1.19, and were stable or growing. One of the populations was in decline, with a growth rate of 0.88 (Charron and Gagnon 1991). The analysis of elasticity matrices showed that the most significant transitions, in terms of contribution to the population growth rate, were size-class 3 to size-class 3, and size-class 4 to size-class 4 (Charron and Gagnon 1991), indicating that the survival of large plants, one year to the next, has the greatest impact on American ginseng population growth rate. These long-lived large plants, with very low mortality, produce a large amount of seeds each year, which is clearly important in a species that has no means of vegetative propagation (Charron and Gagnon 1991). The smaller importance of seed production and seedling recruitment in elasticity matrices, and thus in contribution to the population growth rate, is due to the high mortality associated with these transitions.
The low seedling recruitment and establishment rates (documented for the Quebec populations; Charron and Gagnon 1991), the presence of a relatively long pre-reproductive period (3 years or more), slow individual growth rate (under forest cover), greater longevity of established individuals, relatively stable population growth rate near 1.00: all these demographic characteristics indicate that American ginseng is a species of stable habitats, such as the understory of mid-successional to late-successional deciduous forests.
As with most other plants (Caswell 1986), American ginseng has size-dependent mortality, and the most vulnerable stages of the life cycle appear to be the periods of seed germination and seedling establishment. The combined analysis of the population age structures of four Quebec populations (Charron 1989) shows some evident gaps which may have been caused by a low seedling recruitment during some periods in the past. This low recruitment did not occur every year, however. The possible causes of low seedling recruitment may be fruit crop failure due to drought, predation or pathogens. Results from Missouri populations are apparently different according to Lewis and Zenger (1982), who report that the mortality rate of seedlings contributed little to the overall mortality rate of the population. Once the crucial step of seedling establishment is achieved, a ginseng individual has a high life expectancy (over 20 years; maximum age of 60 recorded by Charron and Gagnon, 1991). The importance of the establishment period for ginseng seedlings in Quebec populations may be a reflection of the marginal nature of these populations, situated at the northernmost limit of the species' distribution range. However, the lack of data from large central areas of the species range does not allow us to conclude with confidence on the difficulty (or ease) of seedling recruitment in ginseng populations in general.
Even though seedling mortality is always high in Quebec populations, it seems that the stability of a population is more sensitive to a decrease in the survival of large individuals than to a reduction in the production of seeds, or in the establishment of seedlings. Thus, the elasticity analysis clearly shows that individuals of size-classes 3 and 4 constitute the most critical life-history stages, once establishment is assured. Size-class 3 individuals contribute much more to the population growth rate if they remain in that same size-class the following year, rather than growing on to size-class 4 (Charron and Gagnon 1991). However, individuals of size-classes 1 and 2 contribute much more to the population growth rate if they grow on to a higher size-class, rather than remaining in the same one. Therefore, the optimal life-history strategy for ginseng appears to be to grow as rapidly as possible to attain size-class 3. It would be very interesting to compare these results, obtained from northern populations, with some obtained from ginseng populations situated at different locations in the east-central and south-eastern US (i.e. Tennessee, North Carolina, Kentucky, Virginia, West Virginia, Ohio). An American ginseng population dynamics study initiated in the Great Smoky Mountains National Park in 1998 should provide some of this data in the next few years (Gagnon and Rock, unpublished data).3. Impact of harvesting on ginseng populations
A far as I know there have been only two attempts to investigate the impact of harvesting on wild American ginseng populations. There is the recent work of Nantel et al. (1996), based on stochastic computer simulations using the transition matrices of Charron and Gagnon (1991), and one calculation made by Sverdlove (1981).
Sverdlove's (1981) result is based on a transition matrix calculated from data of a Wisconsin ginseng population obtained by Carpenter (1980). The transition matrix produced had a growth rate of 1.20, which was reduced to 0.95 when the impact of harvesting was included. I have no further details on what this impact was (percentage of plants harvested, from which size-classes, etc.).
Charron and Gagnon (1991) looked at how many ginseng plants could be harvested without threatening the populations they studied. The method of Enright and Ogden (1979) was used to calculate a percentage of harvestable plants for each transition matrix. Results varied from 0% up to 16%. However, these theoretical harvest levels varied from year to year (in response to the year to year variation in the population growth rate), meaning that a 16% harvest would only be possible in the population that was growing the best in that given year, as a result of a very good growing season. Another important consideration in this calculation is that the harvest level must be spread over each size-class. For example, a harvest rate of 5%, would mean that only 5% of size-class 4 plants are harvested, only 5% of size-class 3 plants are harvested, and so on. The problem is that no harvester would ever behave in this manner. Usually, a harvester will harvest all plants (100%) of size-classes 4 and 3, and if he is conservation minded, will leave most size-class 2 plants and all smaller plants. He may even sow the seeds of the plants he has harvested. Therefore, the percent of plants harvested must vary from size-class to size-class in order to be realistic, such as 0% for all small plants and a certain level of harvesting for the larger plants (3- and 4-leaved plants).
Obviously, all of the above estimates also lack an adequate assessment of the effect of year to year variations in population growth rate, which is caused by variations in the environment (climate, browsing, pathogens, competition, disturbance, etc.). Even large populations that are growing well are very likely to experience a poor growing season once in a while, or even regularly. A harvest rate that is normally tolerable for such a population, will depress the population growth rate below 1.00 during a poor growing season. Two poor growing seasons in a row (highly possible), while also under harvest pressure, may be enough to start a decline from which a population may only slowly recover, if it is not wiped out.
Nantel et al. (1996) used the transition matrices of the four ginseng populations studied by Charron and Gagnon (1991) to make stochastic population projections. With this method, time simulation series are constructed by randomly selecting one of the four matrices to represent each year in the time series. Several time series can be constructed in this way, with each series being different from another because its ordering of matrices is different. From four matrices, one per population, of Charron and Gagnon (1991), several 200-year projections were made. The average population growth rate obtained from these simulations is 1.045 (Nantel et al. 1996). A yearly simulated harvest, using the same 200-year time series, produces a population growth rate that falls below 1.00 when less than 8% of plants of size-classes 3 and 4 are harvested.
In order to understand how a 8% harvest of size-class 3 and 4 plants would be unrealistic to enforce in natural populations, we can use the minimum viable ginseng population size of 172 plants, calculated for Quebec populations by Nantel et al. (1996). This number includes plants of all size-classes, distributed among the different size-classes according to a normal (stable) size-distribution pattern. Therefore, in a population of 172 plants (size-classes 0 to 4), there would normally be 55 plants of size-classes 3 and 4. A harvest of 8% of these plants would yield 4.4 plants per year! No harvester encountering 55 ginseng plants of large size would restrict himself to harvesting only four.
Rotating the harvest every three or five years, allows a larger harvest to be made (approximately 20% and 30% respectively, or 11 and 16.5 plants) (Nantel et al. 1996). However, the few more plants that can be harvested with these longer rotations is negligible when compared to the sum of yearly harvests. For a rotation strategy to be viable for a harvester, he has to know many populations, so that he can visit some each year, while he lets others recover for a number of years. This strategy is fine assuming only one harvester is visiting any given population, which is unlikely to be true nowadays. A harvester, when discovering a new population, may well decide to harvest all large plants. If he does decide to limit his harvesting to a reasonable (sustainable) percentage, the next harvester may decide otherwise. Therefore, the "sustainability" minded harvester may find himself the loser, and his population wiped out by the less careful, or less conservation-minded harvesters that follow him.
Important goals for the near future would be to identify the minimum viable ginseng population size and sustainable harvest levels in various parts of the range of American ginseng. Although both numbers are likely to be different from Quebec populations (lower MVP number, higher sustainable harvest rate), especially for more central and southern populations, the same reasoning will apply as to the behavior of harvesters. Calculating a sustainable harvest is relevant and important for management of the species in US. The demographic data collected in populations closer to the core of the species' range may also demonstrate that the harvesting of roots from wild ginseng populations may no longer be sustainable in most of the US. The major reason being the very different social and environmental situation of today, compared to pioneer times, with its vastly greater number of harvesters, fewer and smaller ginseng populations, and decreasing suitable habitat for the species.
4. Biological reasons why the harvest of wild ginseng is probably not sustainable
American ginseng is a forest understory herb. The forest understory is a relatively stable environment (small changes or variations from year to year) where the plants are adapted to growing in the shade (except of course the spring flowering plants), and face competition for soil nutrients and water from other understory plants (herbs, shrubs and tree seedlings) as well as from the overstory trees. These plants may preyed upon by herbivores (insects, mammals) which periodically eat their leaves (partially or entirely) and fruit/seeds. Some plants are even dug up by animals which consume the roots (although I have not seen or read about any evidence of this for ginseng).
It stands to reason that in such an environment (light stress, high competition), no plant would be able to produce large quantities of biomass. The first requirement for building plant biomass is sunlight. Deciduous forest understories are notoriously dark, allowing only 5 to 15 % of sunlight to reach the forest floor. Conversely, ginseng growers use 75 % artificial shading over their crop, which therefore receives 25 % of the sunlight. Anything above that amount, and leaf chlorosis would occur, as ginseng leaves are not adapted to grow in full sun. However, the increase in available light (from 5-15 % to 25 %) boosts productivity. Similarly, even though ginseng occurs in soils that are nutrient rich (for forest soils) and moist (except during occasional extended periods without rain), the soils are fertilized in the agricultural situation and may be irrigated in periods of drought. These soil factors again boost productivity. Growers also eliminate most herbivores (certainly deer) and control fungal pathogens (although their fungal problems stem mostly from the extremely high density of their plantings). Agriculture can produce a marketable ginseng root in three years. A ginseng plant growing in the wild will require at least four to five times that amount of time to produce a root of equivalent size, and this is assuming optimal forest growing conditions. In most cases, the time required is greater. The proponents of woodsgrown or "simulated wild" ginseng can produce a marketable root in 6 to 8 years. However, they add fertilizers (organic or chemical), remove understory competitors, increase light (overstory thinning) and protect plants from herbivores. They also control recruitment by germinating seeds in a garden and by planting the seedlings.
The natural populations of American ginseng have far slower growing individuals. These populations rely on their seed production to recruit new plants in the population. The seed germination rate may be low, as well as the seedling survival rate (first year) (see section 2). The populations succeed in maintaining themselves, and growing, because of the longevity and low mortality of established plants. These established plants will produce enough seeds over a span of years, even allowing for the occasional poor seed production year, to produce a few new plants that will join the ranks of the established plants. Harvesting targets the largest seed producing plants. Although it is required in many states that pickers plant on site the seeds of the plants they have harvested, it should not be assumed that they do so. Some may choose to sell the seeds or plant them in their own woodlot. A population that has been harvested will retain only its small plants (2-leaved, one-leaved, seedlings), the seeds that are already in the soil, and perhaps the current year's seeds (if a conscientious digger has sown them on site). In this reduced state, the population may have difficulty rebounding if it incurs several poor growing seasons in a row, or if herbivore pressure increases. At best, it will take many years before a number of three-leaved plants equivalent to the pre-harvest number is found. If a population is visited by diggers on a regular basis, it may never have any four-leaved plants (which produce on average twice the amount of seed a three-leaved plant would).
American ginseng is not the only slow growing forest perennial herb. Other studies have reported population growth rates near equilibrium (1.00) for many perennial understory plants. Examples are Chamaelirium luteum (fairy wand), with a population growth rate varying between 0.99 and 1.06, Arisaema triphyllum (jack-in-the-pulpit) with a growth rate varying between 0.85 and 1.32, Arisaema serratum (a Japanese jack-in-the-pulpit) with a growth rate of 0.99, and Allium tricoccum (wild leek or ramp) with a growth rate varying between 1.02 and 1.13 (Meagher 1982; Bierzychudek 1982; Kinoshita 1987; Nault and Gagnon 1993). Conversely, studies of herbs from non-forested habitats have reported extremely variable population growth rates: 0.58 - 1.81 in Pedicularis furbishiae; 0.28 - 2.61 in Dipsacus sylvestris (teasel); 0.77 - 1.65 in Eriophorum vaginatum; and 0.60 - 1.43 in Danthonia sericea (Menges 1990; Werner and Caswell 1977; Fetcher and Shaver 1983; Moloney 1988). It would appear that this high variability is associated with open and disturbed habitats, where the potential for fast growth is present when the habitat has just been disturbed (much light, soil nutrients and few competitors). We then see these plants, such as the field weed teasel, having huge population growth rates (i.e. 2.61). However, after a few years, when exceptional initial conditions have changed (encroachment by other plant competitors), the growth rates fall much below 1.00 and the populations are fast declining to extinction.
As mentioned before, American ginseng is a plant that grows in a relatively stable forest understory habitat. It has a population growth rate that varies relatively little, above and below 1.00 (population stability or maintenance). The surplus growth above 1.00, translatable in individual plants, represents the harvestable proportion of the population (but spread over all size-classes!). Any harvest that removes more than this "surplus" number of plants basically eats into the "capital" of the population. The "surplus" in some years may also be necessary to compensate for losses that occur in "bad" years (poor growing season, seed crop failure).
Biologically, harvesting of wild ginseng makes little sense. The root of the plant is harvested, effectively killing it (not at all like harvesting wild fruit, such as blueberries, or even leaves, such as those of the fiddlehead fern Matteucia struthiopteris). A ginseng plant of the same size will not have regrown in that population for 10 to 15 years, assuming that some small plants are left at all. A yearly harvest is evidently not sustainable. But how can it be prevented, when more than one digger is likely to encounter the same population? Poachers in the Great Smoky Mountains National Park have recently been caught with incredibly small ginseng plants (J. Rock, personal comm.). Wild ginseng roots exported are also known to be decreasing in size (more roots per pound). Lewis (1984) reports from experience that harvesters collect all the large plants they can find. Perhaps in the past, a harvester would follow a route known only to him between numerous populations, and harvest just enough to allow each population to recover. Nowadays, such behavior is likely to be counter-productive if another (or several) less scrupulous harvester finds the populations and removes all large plants, or worse all plants regardless of size. There are no signs that wild ginseng is becoming easier to find, more to the contrary. Exportation figures appear relatively stable over the years (OSA data for 1996; Robbins 1998), but it is possible that a decline in recent years has been masked by more and more roots that are woodsgrown and sold as wild. This brings us to the change in socio-economic factors, which may have, at some point in the past, been appropriate to sustain a harvest of wild ginseng.
5. Socio-economic reasons why the harvest of wild ginseng is probably not sustainable
The socio-economic fabric of areas where wild ginseng is still harvested has changed dramatically from that of pioneer days, when ginseng harvesting was one of many subsistence activities done over vast tracks of virgin forests by a small human population. The story of the careful harvester (because he left behind still healthy populations that he intended to return to) who did large circuits every fall to several large populations in the Appalachians, not even visiting all the ones he knew every year, is definitely a thing of the past. This idealized vision of the past harvester may also not be true. Perhaps there simply was not enough people digging ginseng in the past to deplete the resource. Or maybe the income produced was not sufficient to support a family, and time was better devoted to other activities, such as hunting and agriculture. The value of ginseng roots was not always as high as it is today, and cultivated roots were initially of proportionally higher value. Recent socio-economic data suggests that a majority of West Virginia diggers are people whose primary revenue is social welfare (Bailey et al. 1996).
Past examples of a depletion of ginseng populations exist. American ginseng was discovered in Montreal by a Jesuit (Father Lafitau) in 1716. A rapid trade with China ensued, through the French India Company. For a brief period, ginseng trade generated a large revenue, second only to the fur trade. Farmers abandoned their cultivated fields to seek ginseng in the woods. This intense harvesting persisted only for a few decades. In 1751, large shipments of small and poor quality roots were refused by the Chinese merchants (Haber 1990). This was the end of the Canadian wild ginseng trade. After the Revolution, Americans succeeded in establishing with China an independent commerce based on high quality roots. In the mid 1800s, up to 300 tons of wild ginseng roots per year were exported from the US, representing perhaps 6 to 10 million roots. It is reported that Daniel Boone had collected 15 tons of ginseng in 1787. When he lost his cargo on the Ohio River, he merely returned to get another load of roots (L. Moist, personal comm.).
Nowadays, the harvest of wild ginseng roots has decreased. It is no longer legal to export wild ginseng roots from Canada (in 1989 in Ontario, and in 1975 in Quebec when the species was added to the CITES Appendix II list). However, the US has been exporting close to 65 tons a year of wild ginseng roots in recent years. According to Haber (1990), this quantity is equivalent to more than 12 million individual plants, more than the number of plants in the 1800s, as the size of harvested roots has decreased considerably. Actually, using 1995 data, the number of roots now harvested annually can be estimated to perhaps exceed 28 million.
Harvesting ginseng from the wild in the early 1800s was not an activity for the faint of heart. The risks were numerous. Today, harvesters drive to a trail head and return at the end of the day to drive back to the comfort of their home. However, nobody can earn a living harvesting ginseng. Populations are too few and far between, and they contain few plants. At best, ginseng harvesting provides only pocket money to most diggers (Bailey et al. 1996). The money actually made by the diggers is relatively small, as compared with the dealers and wholesalers who export the roots. Ending US exports of ginseng would cause only minor revenue losses to many diggers, but would perhaps cause large exporters and many other middlemen some financial losses.
The harvest of wild ginseng is not really sustainable in a biological sense, unless harvested populations are not entirely decimated and are left to recover for numerous years (see section 4). We know that such a scenario is very unlikely. Nowadays, most populations are harvested in their entirety when found; small plants are not spared. Only plants that are at the periphery of a population sometimes escape the harvest. There are nowadays more people who know of the high value of ginseng and who are out looking for it, even as a weekend activity. Accessibility is certainly not a problem, with vehicles, and a large network of roads and trails. Suitable habitat may also be decreasing because of recent increases in logging. Habitat fragmentation may prevent ginseng from recolonizing sites where it used to grow (the small number and large size of ginseng seed do not make it an efficient disperser).
The whole socio-economic picture can be summarized by the statement that an increasing number of people (increase in collecting permits; Robbins 1998) are seeking an ever decreasing resource. That the resource is actually decreasing can be inferred from the high level of poaching observed in Great Smoky Mountains National Park, although harvesting is allowed on many adjacent state lands. This illegal activity is a clear indication that protected areas are rapidly becoming the last refuge of appreciable populations of American ginseng, and that finding it outside of these protected areas is becoming very difficult. This disturbing pattern has been reported over the entire distribution range of ginseng (GSMNP in Tennessee and North Carolina, Shenandoah National Park in Virginia, also from Missouri, and Ontario and Quebec in Canada). Field verification is necessary to support these indirect data. Perhaps when field investigators see monitored populations disappear one after the other, will a clear and scientifically valid verdict on the sustainability of ginseng harvesting from the wild be reached. Dr. Lewis, who wrote several papers on ginseng population ecology in the early 1980s has been reported as saying that he still was interested in ginseng, but that he had abandoned studying the plant because too many of his study populations had been wiped out (D. Drees, personal comm.).
What about limits and regulations? These can be valuable only if they can be enforced. For example, if it becomes illegal to harvest small roots, the control can be made by dealers (with spot verifications by wildlife officers or game wardens). A size limit rule can be enforced, as it will become illegal to be in possession of roots smaller than the minimum size. Personal limits on how much ginseng any individual can have in his possession at any one time can also be enforced (with good record keeping), but they can also be circumvented by having relatives sell some roots. On the other hand, all regulations and limits pertaining to harvesting populations are clearly impossible to enforce, and therefore useless. It would be impossible to prove that a digger had harvested all of the large plants in each population he visited.
A last element of discussion in this issue is the number of people whose livelihood truly depends in large part on the trade of wild ginseng roots. This should be verified by others, but my educated guess is that these people are relatively few. Diggers make little money at it. Dealers sell many other things. Exporters are wealthy businessmen who have diversified interests, or who can easily develop them.6. Sustainability? Evidence available and evidence needed
Clearly, the evidence that wild ginseng harvesting will not be a sustainable activity in the United States of the 21st century is largely theoretical, circumstantial or indirect. Direct, empirical data are lacking to clearly demonstrate that harvesting is not sustainable. However, the fact that the same evidence is also lacking to clearly demonstrate that the practice is presently sustainable is far more worrisome.Ecological data and theory indicate that ginseng, a slow growing forest understory perennial herb, does not have a population growth that is sufficient to withstand, over the long term, more than a small harvesting pressure. The only recent demographic data that can be brought to bear on this issue comes from southern Quebec (Charron and Gagnon 1991; Nantel et al. 1996), at the northern limit of the range of the species. These results clearly show that only a small percentage of plants (3- and 4-leaved only) could be harvested annually from wild populations. Such small percentages would be unacceptable by any self-respecting digger, but worse, they would be impossible to enforce. The demographic results obtained from Quebec populations are probably not representative of the entire range of the species. Populations situated near the center of the species' range (central Appalachians) may possess population dynamics characteristics that would make them less vulnerable to harvesting. Such features could be a faster individual growth rate, higher individual survival rates (particularly for seedlings), a higher germination rate, and a larger seed production per individual. The cause for such enhancement could be a longer growing season. The soils are probably not significantly richer, and the plants are equally subjected to high competition from plant neighbors in the center of their range as they are on its margins. Problems caused by deer browsing are more serious in southern Ontario, than in Quebec, and one would suspect that it would also be a problem in many states (Pennsylvania, Virginia, West Virginia). Perhaps only well established ginseng plants are at an advantage over northern plants in the center of the range. Seedlings may have equal difficulty being recruited into populations, throughout the species's range. Population dynamics data is thus required from populations located more centrally in respect to American ginseng's range, in order to confirm or refute these hypotheses.
American ginseng populations, spread over the species' range, but with particular emphasis on the central and southern regions, need to be monitored to acquire basic regional population dynamics data.
This high intensity monitoring requires the monitoring of the demographic fates of marked individuals.
These data are necessary for the management of ginseng, whether for harvesting or for conservation. We could verify if the minimum viable population size established for Quebec populations (n = 172) is valid for more southern populations, of if it may not be lower (therefore lowering the risks of population extinction from harvesting). We could see if population growth rates are high enough to be able to tolerate harvesting, and at what level. The data could be used in computer modeling to simulate the impact on populations of various harvesting regimes, and calculate probabilities of recovery from severe harvests.
Increasing poaching in Great Smoky Mountains National Park is indirect evidence that ginseng is getting scarce in the surrounding areas where harvesting is legal. To my knowledge, there is little field data now being collected on ginseng in the US, except in Kentucky (T. Jones, pers. comm.). A past exception was the monitoring program of Sutter (1982) in North Carolina, where seven out of 21 monitored ginseng populations were harvested (33 %). Out of the seven harvested populations, two were extirpated (all plants harvested) during the three year duration of the program (a 9.5 % extinction rate). Several ginseng populations, over its entire range, need to be monitored for changes in plant numbers, caused by harvests or other factors. The data collected would provide real evidence of recovery time following harvests, or whether recovery occurs more or less often than decline after a harvest. The occurrence of population extirpation could also be quantified.
Numerous American ginseng populations, spread over the species' range, need to be monitored to detect general population trends, frequency and level of harvesting, and frequency and rapidity of recovery following harvest. This low intensity monitoring requires the recording of the numbers of ginseng plants, by size-classes, in each monitored population. Fruit and seed production data should also be recorded.
Real field data from natural ginseng populations should rapidly show if there is cause for alarm or not. The numbers will tell the story.
The average size of roots harvested has also been reported to have declined. This needs to be verified accurately. However, the roots weighed must strictly be wild grown, not woodsgrown mixed in with only a few wild grown roots. No accurate and trustworthy data can be acquired until wild roots are clearly separated from any other type of root.
Measurements of the weight of harvested wild ginseng roots must be made from samples taken from dealers or exporters. In order for accurate data to be recorded, it must be made illegal to report as wild ginseng any kind of root that has not been taken from wild populations. Increasing quantities of woodsgrown ginseng may otherwise hide very real declines in true wild ginseng harvests.
Implementing a two-tiered ginseng population monitoring program throughout the species range (or minimally within the states where harvest is allowed) will provide an accurate picture of American ginseng's real status in the wild. The more intensive population dynamics monitoring needs to be done, on a smaller subset of populations, in order to provide an understanding of the regional population dynamics of ginseng. The resulting data can be used to model population growth, simulate the impacts of various levels of harvesting, and help suggest management methods to augment population numbers or mitigate the adverse effects of harvesting. The low intensity monitoring of a large number of populations will give clear indications of what is really happening in the wild. Finally, monitoring harvested root size accurately should give a good indication of resource depletion, if the issue of woodsgrown ginseng sold as wild ginseng can be resolved.7. Recommendations for action
Robbins' (1998) document on ginseng contains several useful recommendations. The recommendations below are suggested to reduce negative impacts of harvesting on wild ginseng populations, to increase knowledge about the population ecology and actual field status of ginseng in the US, to enhance conservation of ginseng, and to even suggest novel sustainable ways to use this resource.
· Make a rule on the minimum size allowable for a harvested ginseng root (could be based on the average size of a two-leaved plant, so that harvesters would only harvest three-leaved plants or larger).
· Make it illegal to represent (sell) woodsgrown ginseng as wild ginseng.
· Make it illegal to possess wild ginseng seed (except by special permit for research).
· Make it illegal to report (or sell) wild ginseng as coming from one state when it actually comes from another (develop enforcement, see 7.7 below).
· Consider a moratorium on ginseng exports from the US if monitoring reveals declining trends (or even now, while studies are being done).
7.2. Inventory and monitoring
· Instigate a two-tiered wild ginseng population monitoring program.
· Instigate an extensive, low intensity population trend monitoring program.
· Instigate an intensive, high intensity population dynamics monitoring program.
· Require participation in the monitoring program of all states where wild ginseng harvest is allowed.
· Solicit and encourage participation in the monitoring program, on a reduced scale, from all states where ginseng occurs, but where it is not legal to harvest.
· Suggest targets of 5 to 10 high intensity monitored populations, and 10 to 20 low intensity monitored populations for each state (actual number of monitored populations may be at the minimum for various practical reasons, and monitoring may be established over two years).
· Create a reporting structure (from a maximum level of state involvement, including data analysis, to minimum involvement, field work and data compilation; this last option would require analysis by a USFWS ecologist).
· An inventory of most existing known ginseng populations should be made as a baseline from which to select populations to be monitored (will occur automatically if monitoring program implemented).7.3. Conservation
· Create a network of protected American ginseng populations. Through contacts, create a network of known ginseng populations that are legally protected from harvesting (national parks, state parks, Nature Conservancy properties, other private conservation areas). Choose some of these protected areas for at least half of all monitored populations. Involve local staff in monitoring efforts.7.4. Restoration
· Restore small ginseng populations. This can be done by visiting the small populations and planting in situ the seeds produced by its own plants. Population size can also be augmented by sowing pre-stratified seeds in small populations to be restored, using seeds collected in large populations within the region.
· Target populations that are just below the minimum viable population size (use 172 MVP size found for Quebec, or use regional MVP sizes as they become available), in order to bring their size above this threshold.7.5. Agriculture
· Promote genetic improvement work for cultivated American ginseng. Bai et al. (1997) have shown high genetic variability in cultivated ginseng plants, which would enable effective selection work to be done for crop improvement. Crop improvements could be to increase ginsenoside content, or increase resistance to fungal pathogens.
· Promote the idea that wild American ginseng populations are a very valuable genetic pool for future improvement of the agricultural crop (solicit partnerships with growers).
· Experiment with increasing ginsenoside content in leaves, in order to harvest leaves instead of roots (no replanting necessary).
· Develop partnerships for monitoring and conservation actions between federal and state governments, with conservation NGOs, universities, field biology stations, private conservation areas, and with private ginseng growers and grower associations.
· Establish two-tiered ginseng population monitoring program partnership between government agencies (federal and state), conservation NGOs, universities and all other interested participants.
· Establish seed gardens (for restoration and research) of genotypes of wild American ginseng populations, in many regions, in partnership with ginseng growers or their associations (they have the necessary site security). Payback for the growers would be part of the seed produced, for use in their plantings or for improved crop development.
7.7. Genetic and other types of markers
· Genetic markers could be developed for crop improvement purposes, but also for purposes of keeping track of the source (wild population) of the material. Uses in law enforcement are also foreseeable.
· Develop for ginseng roots the same tool used for identifying where monarch butterflies did their larval development. This method uses natural isotope ratios in the buterfly's body to identify where its larva grew. The county in which a ginseng root grew could thus be identified. Plants coming from protected areas may also be identifiable. This technology does not require the long development time of genetic analysis.
7.8. Somatic embryogenesis
· Tissue culture (in vitro) should be investigated as a means of mass production of plantlets for restoration purposes, or of cultivars with high ginsenoside content for agriculture. There has already been considerable preliminary research in this field (on Asian ginseng in China, Vietnam and Japan, but also on American ginseng by Dr. Sylvie Laliberte at Universite du Quebec, Montreal).
8. Monitoring wild ginseng populations
8.1. Two levels of monitoring intensity for two different purposes
Monitoring can mean very different things to different people, or require very different things depending on what we would like to demonstrate or achieve with its results. A good framework is provided by a recent paper by Menges and Gordon (1996), entitled "Three levels of monitoring intensity for rare plant species". The authors list four general goals to monitoring biological resources: (1) detecting significant changes in abundance; (2) understanding the reasons for these changes; (3) determining the effects of management practices (including harvesting) on population dynamics; and (4) suggesting key applied research questions (Menges and Gordon 1996).
American ginseng is beyond doubt a very valuable biological resource. It is the most sought after plant in the entire US and its harvest from the wild brings in considerable revenue. Its survival in the wild (for the conservation of its gene pool) is also vital to an equally important agricultural industry. It should therefore be a common concern to all involved with ginseng that its status in the wild be accurately assessed. Are wild populations of ginseng declining? In numbers of populations? In numbers of plants? Or are they maintaining their numbers? Is this picture the same everywhere in the US? Nothing can replace actual field verifications for these types of data. No wildlife biologist would accept making hunting harvest quotas without some field surveys to assess abundance, and without knowledge of the regional demographic characteristics of the population he or she has to manage.
Acquiring knowledge about abundance and about demographic characteristics requires two different levels of field monitoring, the second and third level described by Menges and Gordon (1996). Their first level requires only the recording of the presence of a population, and reveals nothing about the state of each population, until it is no longer there. The second level of monitoring requires a quantitative assessment of abundance. In the case of ginseng this could be a count, by leaf number size-classes, of all the plants in all the populations monitored at this level (see section 8.2 below). This level of monitoring allows the analysis of population trends. It answers questions about the numbers of populations and plants, and after a number of years of monitoring, general or individual population trends can be detected (increase, decline, overall stability). The third level of monitoring, which is the most intensive, requires the monitoring of marked individuals for several years, usually over 100 in each study population (see section 8.3 below). This level of monitoring provides quantitative information about demographic parameters. The data can be used for calculating population growth rates, for making population viability analyses, for modeling the effects of harvesting or management practices, etc. Demographic mechanisms underlying population trends can then be identified.
A particular characteristic of ginseng population monitoring is the level of confidentiality, or even secrecy, involved in the record keeping of accurate locations of the existing or monitored populations. Populations identified on maps left in sight of unscrupulous people (in an office, in the field) may disappear very rapidly. Because of this, private land owners and even public servants may be very reluctant to divulge the location of the populations they know. Therefore, good security and very limited access to precise site information is essential for success. Otherwise, the monitoring process may itself cause the demise of ginseng in an entire area.8.2. Monitoring for general population trends
A maximum number of ginseng populations should be monitored for basic population trends. Assuming each state agrees to support the intensive monitoring of 5 to 10 ginseng populations, at a level necessary for population dynamics information (see section 8.3 below), an additional 10 to 20 ginseng populations should be monitored for general population trends. Because the data of intensively monitored populations can be used as well for general population trends, each state would then have general population trend information for 15 to 30 populations.As the population selection guidelines are identical for both types of monitored populations, these are given in the following section (8.3.1). Similarly, site data and vegetation data for each monitored population are required, in order to be able to determine if the intensively monitored populations are representative of the majority of ginseng populations in the state (see section 8.3.2, and field forms in appendices 1 and 2).
The only difference between the two types of monitoring, is that the less intensive population trend monitoring does not require the year to year precise identification of individual plants. Initial sampling is thus much less time consuming, as no precise mapping is required for individual plants (a general mapping of patches of plants within the population is however useful for subsequent monitoring). Similarly, when the populations are revisited, no time is required to verify the identity (number and position on map) of each individual plant. All that is required, every year as the population is monitored, is recording the number of plants found in each size-class category. The number of seedlings and larger one-leaved plants may vary quite a bit from year to year, depending on yearly environmental variations, but also because of the varying thoroughness of each investigator (especially if they change from year to year). However, this lack of precision in recording plants in the smaller size-classes is not a serious problem, as all investigators are likely to record all ginseng plants found in the size-classes with two leaves or more. These larger plants are those targeted by harvesters. The year to year comparison of the size-class structure (a graph of how many plants are found in each size-class) of a population will reveal a large amount of information, such as population growth (increase in number of plants) and evidence of harvesting events (sudden disappearance of all four-leaved plants, and most or all three-leaved plants). Following a harvesting event, it will be very useful to continue monitoring the population to record its regrowth, or perhaps its eventual decline to extirpation.
Soon (within a few years), an extremely valuable baseline of information will have been acquired on how many populations have been harvested, how frequently, and how many have regained their numbers, or declined to smaller population size, or even declined to extinction. A record should be kept of all known populations and their size (an inventory), and their continued existence should be verified every few years (i.e. all are revisited within three to five years). This is equivalent to the level 1 monitoring of Menges and Gordon (1996). It can send a coarse warning signal if suddenly a large percentage of known populations are no longer found. Some of these populations may be monitored for general population size trend in the future, in replacement of previously monitored populations that have since disappeared.
On top of recording the number of plants per size-class, general population monitoring would benefit from a recording of each plant's fruit production, and even the number of seeds. The same field form as for intensive monitoring can be used to record this data (appendix 3), the only difference being that each ginseng plant is not identified precisely (saving considerable time). The time required to complete this low intensity monitoring is approximately half of what is required for the high intensity monitoring (described in section 8.3). The time difference is not greater simply because monitored populations are not expected to be located just next to each other, and that some car travel and hiking time will be required in between populations. Therefore, it is expected that a team of two field investigators should be able to record all of the necessary data for each population in half a day. There should be no difference in this estimate between the first year and subsequent years, because site and vegetation data can be recorded in about half an hour (during the first visit). A field team should be able to monitor 10 to 20 populations in 5 to 10 working days, with no allowances for inclement weather, as data forms are uncomplicated and fast to complete. The optimal time of year for this type of monitoring is identical to that of the more intensive monitoring, but because it not so critical to accurately record fruit and seed production (the numbers of plants in each size-class are the most important data), this monitoring could be carried out before and after the optimal period for demographic monitoring. In fact, population trend monitoring could start in the last week of July and serve to decide when the more intensive demographic monitoring could start (by observing daily the state of fruit ripening). When close to half the fruit on each fruit-bearing plant have turned red, the intensively monitored populations could be all sampled (5 to 10 in a one to three weeks period, by one sampling team of two, or in less time by two sampling teams). Afterwards, the low intensity monitoring could be resumed.
In all, 20 low intensity monitoring populations and up to 10 high intensity monitoring populations could be sampled in 5 weeks (from the last week of July to the end of August) by a two person sampling team, during the first year of the monitoring program. Two sampling teams may be required in the first year if distances are large, and if populations are not already precisely located. This sample size should be ideally acquired in each state. However, time constraints, budget constraints and lack of adequately trained personnel may force some states to initially aim for the minimum number of monitored populations (5 high intensity + 10 low intensity), or spread tthe initial sampling over two years. A sufficient number of populations may also not be known to state officials. This monitoring program should at least extend to those states where ginseng harvesting is permitted, but the participation of states where ginseng is not harvested or rare would also be very useful and should be solicited and encouraged.
8.3. Monitoring for population dynamics information
8.3.1. Study population selection and time required
The study of the population dynamics of American ginseng should be based on the study of as many populations, of over 100 individuals each, as possible. The limitation will be the resources available to do the annual monitoring. The first year effort will undoubtedly be greater because the precise mapping of all individuals is required. More time will be required also if a search is necessary to locate study populations. However, the staff of national parks, state parks, national and state forests, as well as owners of private land or protected areas may know of some populations that meet the criteria for this level of monitoring. The field data collecting itself should be done by two person teams (one assessing each plant, and one taking notes and mapping). A team is expected to sample at least a population per field day, with allowances for driving and hiking to the site.
Assuming a state has the responsibility of monitoring 5 populations for population dynamics data, this should easily be accomplished by a two-person team in 5 to 10 working days (to allow for inclement weather, as data recording requires meticulous work difficult in pouring rain). The initial sampling, requiring more effort (i.e. precise mapping), is estimated to take the sampling team the full 10 working days. These estimates are based on the assumption that the sampling team can easily locate each study population. Either they have precise location maps, or are met on site each day by local experts or staff and led to the study population. This needs to be done only once, as the sampling team should carefully document the location of each study population (GPS data if possible, or precise position on large scale map). A state could choose to have two sampling teams in the field at the same time, each would share in monitoring population dynamics in some populations, but could also share in the more extensive population size and structure monitoring (see section 8.2.). The justification of two teams is to be able to visit monitored populations at an optimal time during the growing season. The optimal time is when the fruit are still partly green and turning red. This optimal time will vary from state to state, due to normal climate differences, and from year to year, due to annual variations in climate. However, in general and over most of the species' range, August is certainly the best month to conduct field work on ginseng. Earlier, the fruit may be under-developed and the seed they contain impossible to count (by visual inspection). Later, the fruit may have begun falling and smaller plants may have started their fall senescence. Even by August, it is possible that seedlings of the year may have already senesced or died (especially during a hot and dry summer). One or two populations could be visited earlier in the summer to quantify this phenomenon. However, the overall impact of this less accurate seedling data on population level results is expected to be slight, as opposed to large plant survival and seed production data, which are accurately measured by a single late summer (August) visit to each study population.
Populations selected for study must meet a maximum of the following criteria:
For each studied population, a site description and a vegetation description should be produced. The data needed for these descriptions can be collected on two field data forms, the "Site and ecological data" sheet (Appendix 1) and the "Vegetation data" sheet (Appendix 2). The first data form is used for recording all site and ecological data measured or estimated in the field. The information it contains is completed with the analysis of a soil sample. This soil sample, of approximately 500 ml in volume, is taken from a 5 to 15 cm depth in the mineral soil (after removing litter). This depth corresponds to the average rooting depth of mature ginseng plants. Soil data is necessary to confirm that the site has good potential for ginseng growth, in order to eliminate the possibility that if poor growth is observed that it is caused by a nutrient-poor soil.
Soil samples will be air dried, and passed through a 2 mm sieve before analysis. The soil analysis should include: pH, % organic matter (loss on ignition), NO3, NH4, available P, Ca, Mg, K and Mn. Textural analysis (soil particle size distribution) is also useful.
The vegetation data collected will consist of the estimation of the total percent cover of each vegetation strata (tree, shrub, herb, moss), and of the estimated individual percent cover for tree species, shrub species and herb species. No specific limits will be laid out for these percent cover visual estimates, but the estimate should be representative of the vegetation associated with the ginseng study population.
8.3.3. Demographic data sampling
Locating individual plants
In each studied ginseng population, we should be aiming at precisely locating a minimum of 100 plants with two leaves or more. This number is to insure that each studied population is well above the minimum viable population size, established at 172 ginseng plants (including first year seedlings and one-leaved plants) for populations at the northern limit of the species' range (Nantel et al. 1996).
Using recognizable permanent landmarks (boulder, large tree), patches of ginseng plants will be mapped, using as many patches as necessary to achieve the required minimum number. The mapping method will involve measuring and mapping a perimeter for each patch, using measuring tapes or topofil (surveyor measuring thread) and compass bearings, which will be reproduced to scale on a grid paper (Fig. 1). Mapping can be facilitated by temporarily placing colored plastic tapes on some trees and temporarily flagging each ginseng plant encountered (all tapes and flags to be removed after mapping is completed). The exact location of each ginseng plant with two leaves or more will also be transferred on this map. Each of these plants will be attributed a sequential number.
Within each patch, particular care will be given to locating first year seedlings (small one leaf plants with three leaflets) and larger one-leaved plants (large three-leaflet plants and five-leaflet plants). Care must be exercised in order not to trample these small plants, which are difficult to locate in the understory. Each of these will be attributed a sequential number as well, and their position mapped in relation to larger plants on the patch map, or in relation to larger plants but on a specific enlarged map section (Fig. 1). Details of standing trees, logs or boulders should be added to the maps whenever possible in order to insure that individual plants can be relocated as easily as possible (Fig. 1). As details about the size and number of leaves of each plant will be noted, relocation problems should be minimal the following year (as ginseng plants will generally look the same from year to year).
An additional method of identifying individual plants would be to insert engraved aluminum nails (2 inches long) into the soil beside each plant. Sequential numbers would be pre-engraved on the heads of these nails (with a common electric hand-held metal engraver), which could be relocated using a small metal detector. This method was suggested by Dan Drees, who uses it in his monitoring of ginseng plants in Meramec State Park in Missouri. This method was also used in 1998 when establishing two demographic study populations in the Great Smoky Mountains National Park (Gagnon and Rock, unpublished data)18.104.22.168. Data collected for individual plants
It is crucial that the data collected from each individual plant be as accurate as possible, as it will be measured again on each individual plant for many years, and will be the basis of all population dynamics analyses. After each individual plant's location is mapped, its demographic data in recorded on a field form ("Ginseng data", Appendix 3).
The information recorded for each plant includes: Individual sequential number, height in cm, number of leaves (or prongs) and percent of leaf area browsed [and for one-leaved plants, the number of leaflets is also recorded], the number of flowers (by counting the number of pedicels), the number of fruit (determine if fruit has fallen or was removed [ex. by birds or small mammals] before sampling, or aborted [never formed]; this can be ascertained by the color of the pedicel, which is red for those fertile, and green for those aborted), and number of seeds (the shape of the fruit reveals if it contains one, two or three seeds). For some plants with very large clusters of fruit, these counts can be difficult. Marking each fruit with the tip of a marker helps in keeping track as they are counted. Fortunately, such plants are usually few in each population (see Figure 2 for an illustration of information to be recorded for each plant).22.214.171.124. Sampling date and frequency and study duration
The studied populations should be revisited in one year's time, in early August, to record demographic data for all mapped and numbered individual ginseng plants. The same will be repeated in subsequent years.
Each year, extreme care will be taken to locate and record any new recruits to the population (first year seedlings). These recruits will be numbered and incorporated in the monitoring. Also, the mortality of individuals must be recorded, after a thorough search, and preferably including the locating of remaining dead structures (i.e. dead rhizome). This is particularly important in the light of evidence that some individuals may lie dormant for a year (perhaps following a trauma). Objective recorded evidence of this dormancy phenomenon is presently lacking.
8.3.4. Field and laboratory seed germination trials
Ideally, seed germination rates should be estimated for each study population. In each studied population, 75 healthy seeds should be collected from large plants that are not being monitored (outside of mapped patches). Seeds should be removed from the fruit pulp and washed. A group of 50 seeds will be sown in situ in order to measure percent seedling emergence (two summers later) in each population. This information is important for the demographic analysis. The seeds should be sown at 1 cm depth in the mineral soil and covered with a thin layer of leaf litter. A 20 cm by 25 cm wire cage should be put on top of each seed germination trial (one per studied population), in order to prevent seed predation by small mammals. Stiff wire pegs should be inserted through the cage and into the soil in order to firmly anchor it.
The remaining 25 seeds per population should be taken to headquarters to be placed in moist sand, in marked 10 by 10 cm nylon mesh bags (one per population), buried 2 cm deep in a shaded outdoor garden where the soil is kept moist. In November, 5 cm of leaf litter should be placed on top of the soil. Soil moisture should be maintained throughout spring and summer. In October of the year following sowing, nylon seed bags should be removed in order to record signs of seed germination. Afterwards, all seeds can be sown (no bags) in a common shaded outdoor garden. Appearance of seedlings should be monitored in the following spring (May to June).
Seed germination and seedling emergence data from a controlled environment are important in accurately assessing natural seed mortality rates. However, the taking of seeds implies that a good seed crop has occurred, and that unsampled plants with seeds are available nearby. The seed of monitored plants should not be harvested, as this will affect future seedling recruitment in the study population.
8.4. Overview of demographic analysis methods
Demographic analysis in plants (as in any group of organisms) is based on data recorded on the fate of individuals. It is therefore extremely important to identify individuals precisely, at each time step (August to August), in order to record their demographic state at that time. This is the reason for mapping the precise location of each studied individual plant within each study population.
Demographic fates are thus recorded each year for each individual. First, we verify that the individual has survived, or if it has died. Size is then measured to assess growth, lack of growth (stasis), or decrease in size (a possibility in plants). Finally, reproductive output is measured for each individual. This is simply measured by the number of seeds produced. Other variables, such as number of flowers and fruits, and the cause of a low fruit crop (if evident), are not strictly necessary for demographic analysis, but are useful in identifying the causes of low seed production. Also, each year, the studied population must be searched for the appearance of seedlings, recruiting into the population. In the case of ginseng, the seeds produced in the fall will germinate the following fall, 12 months later, and appear as seedlings the second spring following their production (20 months after being dispersed). Thus a seed crop produced in a given fall will not be reflected in the following spring's seedling crop. It is therefore very important to have a good estimate of field germination - seedling emergence rates. These data are obtained experimentally by in situ germination trials.
In order to proceed with the demographic analysis, it is necessary to group all the individuals studied into a small number of categories, which hopefully will contain individuals that display very similar demographic characteristics. In population studies of animals, such categories have usually been based on age (obtained through tooth sections, growth rings on fish or turtle scales, etc.). However, apart from trees growing in temperate and cold regions (annual growth rings), most plants cannot be aged accurately. A conceptual breakthrough was made by Harper (1977), in proposing that size was always better correlated with demographic rates in plants, as opposed to age. This opened the field of population biology to plants, the population dynamics of which could now be studied in populations of individuals grouped in categories of size.
Because age can be determined on ginseng plants, by counting annual bud scars left on the rhizome (after carefully removing, and replacing, the soil over the rhizome), it is one of the few herb species in which the greater importance of size, rather than age, can be tested. It has been shown in ginseng that size is a better predictor of demographic rates (ex. fruit production) than age (Charron and Gagnon 1991). In other words, a large ginseng plant will produce a lot of fruit, regardless of its age. It may be large because it is old, or only because it has grown in very favorable conditions (ex. under cultivation). Similarly, small plants have higher mortality rates and produce few or no fruit. This may be because the plants are young, or it may be equally true that they are old but still small because they have grown under difficult conditions.
The boundaries of size-class categories can be determined objectively, using a computer algorithm. Or they can be determined more subjectively, based on size features easily recognizable in the field, and closely related to demographic fates. In the case of ginseng, size-class categories can easily be based on the number of leaves a plant has. Seedlings and young plants have one leaf, with 3 (for seedlings) to 5 leaflets. As they grow, they can produce, two, three or four leaves. Very large individuals with five or even six leaves are sometimes found, but they are rare and can be grouped with the four-leaved plants. Seeds are a put in a separate demographic class. Thus for ginseng, we obtain a seed category (a state class) and five size-classes based on the number of leaves: 0 = seedlings (one leaf with 3 leaflets), 1 = one-leaved plants (more than 3 leaflets, or older than a year), 2 = two-leaved plants, 3 = three-leaved plants, 4 = four-leaved plants.
The demographic analysis consists partly in comparing the various demographic rates for each size-class (i.e. mortality rate, growth rate, flower production, seed production). However, in order to obtain a clear picture of the growth of an entire studied population, the use of size-classified transition matrices, or projection matrices, is recommended (see paper by Charron and Gagnon, 1991). A transition matrix is made up of cells, each of which represents the probability of a certain fate occurring during the matrix's time step (one year in this case). The cells represent all of the transitions from one demographic state to another, or the stasis in the same state (ex. seed to seedling, class 1 to class 2, or class 3 to class 3). Of course, some transitions are frequent, some are rare, and some others are impossible (ex. going from seedling to seed). The number of cells in a transition matrix depends on the number of size-classes (or combination of state- [ex. seeds] and size-classes) used. With ginseng we have six state/size-classes, and we obtain a matrix with 36 cells (6 x 6).
The state of individuals at time t of the study (1st year of study) is represented by the size-classes positioned at the top of the matrix. The state of individuals at time t+1 of the study (2nd year of study) is represented by the size-classes positioned at the left-hand of the matrix. The transition matrix is separated in two halves by a diagonal of cells running from the top left-hand corner to the bottom right-hand corner. This diagonal is made up of "stasis" cells, for individuals which remain in the same size-class during the time step represented by the matrix. This is the most frequent transition for most ginseng individuals with two leaves or more. Most ginseng plants remain in their size-class from one year to the next, which implies that growth is slow in this species. In some cases, stasis is not allowed by the matrix; all seedlings (class 0) move on to size-class 1 or die, and we assume that all seeds germinate or die (no persistent seed bank). In the lower half of the matrix, below the diagonal, the cells represent growth transitions (passage from size-class 1 to 2, or size-class 1 to 3, etc.). In the upper half of the matrix, above the diagonal, the cells represent a decrease in size transitions (passage from size-class 3 to 2), which are not frequent, but still possible.
The top row of cells of the matrix represents the average seed contribution per individual for each of the size-classes. Charron and Gagnon (1991) reported an average production of seeds per individual of 18 to 34 seeds for size-class 4 plants, and of 6 to 22 seeds for size-class 3 plants, in four Quebec populations. Size-class 2 plants rarely produced seed, and size-class 1 plants never did. The sum of all transition probabilities in each ginseng matrix column, omitting the seed number cell, is equal to one when the mortality probability is added. The mortality probability for each size-class is sometimes added as an independent row at the bottom of transition matrices. If it is not directly written, it can be easily calculated as the difference between one (1) and the sum of all transition probabilities in a given column. A "right eigenvector" of the matrix is also sometimes displayed as a column on the right-hand side of the matrix. This represents the stable size distribution vector of the matrix. By multiplying each number associated to a size-class in this vector by the total number of plants in the population, we can obtain the number of plants in each state- or size-class at stable size distribution.
A transition matrix is extremely easy to produce, once the difficult task of acquiring the field data has been accomplished. Each transition matrix represents a particular studied population, and the fate of its individuals from one year to the following year. Therefore, each transition matrix is necessarily constructed from two years of data, data from year one (ex. 1999) and data from year two (ex. 2000). With three years of field data, we can construct two transition matrices (1999 to 2000, and 2000 to 2001) for each studied population. To calculate the transition probability cells within a matrix, one has to proceed column by column, using the total number of individuals in the size-class corresponding to the column in year "one" (time t), for example 50 individual plants of size-class 2 in 1999, in order to divide the numbers of these same individuals in each size-class or state (i.e. death) they have transited to in year "two" (time t+1, or 2000). For example, of the 50 size-class 2 individuals of 1999, 35 may have remained size-class 2 plants in 2000 (35/50 = 0.70), 11 may have grown to size-class 3 plants (11/50 = 0.22), and 4 may have died (4/50 = 0.08). These transition probabilities complete the column of size-class 2 (0.70 in the 2-2 transition cell; 0.22 in the 2-3 transition cell; all other cells are 0.00; mortality rate is 0.08). The seed production for that column is the average seed production for 1999 of individuals plants in size-class 2 (ex. 56 seeds produced / 50 size-class 2 plants = average of 1.12 seeds/plant).
Several useful demographic interpretations can be made directly from the study of individual matrices. For example, decreasing mortality can be observed as plants become larger, or increase in size-class. Stasis (remaining in the same size-class) can also be observed to be the most prevalent transition, particularly in larger size-classes (2 and higher). Finally, the increasing number of seeds produced per individual plant can also be seen to increase as size increases. However, the most useful single piece of information that can be obtained from a transition matrix, is the growth rate () of the population it represents. The growth rate indicates if a population is stable (recruitment equal to mortality, = 1.0), or expanding ( ³ 1.0), or decreasing ( ² 1.0). For example, a growth rate of 0.95 indicates that a population is decreasing at a rate of 5 % annually. Similarly, a growth rate of 1.10 indicates that a population is expanding at a rate of 10 % annually (increase in total number of individuals, spread over all state or size-classes, in proportion to the normal size distribution of the population).
In order to extract more information out of each transition matrix, they can also be transformed into elasticity matrices (see method in De Kroon et al., 1986). Elasticity matrices are basic transition matrices in which each cell is transformed in order to express its specific contribution to the population growth rate. The cells with the largest values in an elasticity matrix indicate which transition, or transitions, contribute the most to the population growth rate. For example, in Quebec ginseng populations, the transitions 3-3 and 4-4 (size-class 3 and 4 individuals remaining in their size-class) were seen to be the highest contributors to population growth rate (Charron and Gagnon 1991). This means that maintaining large plants (3 or 4-leaved individuals) in a population is very important to population growth, as these are the most prolific seed producing individuals, and because ginseng relies solely on seed production for population maintenance and growth (there is no vegetative propagation in ginseng, as opposed to many forest perennial herb species).
The population growth rate obtained for each individual matrix identifies the growth trend of the population represented by each matrix, during the time step represented. This is why transition matrices are referred to by some as projection matrices. One can project into the future the population growth trend obtained, in order to predict if the population is stable, growing (slowly or fast) or declining (slowly or fast). However, this prediction implies that the environmental conditions occurring during the time step represented by the matrix (one year) will remain the same in the future. This is certainly not true, as year to year variations in environmental conditions are common and frequent (drought, frost, browsing, pathogens, etc.), and they have a significant influence on demographic parameters (flower abortion, seed production, growth, mortality, germination, seedling emergence). At best, the population growth rate derived from one matrix is a good snapshot of the status of the studied population (stable, expanding, declining).
In order to provide a better tool for predicting the survival and growth of a population, several matrices are needed. These can be used in stochastic population projections, which give a more realistic picture of the population dynamics over time. Stochastic population projections are achieved by calculating the growth of a population using a series of matrices in a random order. This is more similar to what occurs in a natural environment, where years of good growth will alternate with years of poor growth, and sometimes several good or bad years in a row will occur. These different matrices should optimally come from the same population studied over several years, such as the four matrices produced for a wild leek (Allium tricoccum) population by Nault and Gagnon (1993). However, if several populations from similar ecological conditions (i.e. same elevation, habitat and vegetation type) are studied at the same time, all of their matrices can be pooled to produce the series of matrices necessary for stochastic population projections (Nantel et al. 1996).
Stochastic population projections can be used to calculate a minimum viable population size for ginseng, for each distinct region or state studied (Nantel et al. 1996). Similarly, these projections can be used to predict the effects on population survival of various levels of harvesting (Nantel et al. 1996). The method used is to produce 100 series of randomly ordered matrices, from those available (a minimum of four should be used; they can be obtained initially by studying four similar populations for two years [one transition per population], or better by eventually having as many transitions as possible for each study population). Each random series is different, as the order of appearance of each matrix is different within each, and represents 100 years. Minimum viable population size can be empirically determined by doing 100 population projections (using the 100 random series) for each one of different starting population sizes. The largest population size at which 5 % or more of the series become extinct, is the minimum viable population size. This minimum viable population size (MVP) is defined as a population size likely to give a population a 95 % probability of survival over a period of 100 years (Menges 1992).
Similarly, harvesting impacts on population survival and growth can be tested using stochastic population projections. The appropriate cells of each matrix (i.e. those of 3 and 4-leaved size-classes, targeted by harvesters), can be modified to account for harvesting by simply increasing mortality. In the case of ginseng, the harvesting of a plant is the demographic equivalent of its death; it is entirely removed from the population. Whether the seeds are left at harvest, or removed, can also be modeled. Another refinement possible is the frequency of the harvesting. It can be every year, every three years, every five years or more, or follow a random pattern (i.e. discovery by poachers).
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1: "Site and ecological data" field form
|SITE NO.:_________||NAME OF SITE:_______________________________|
|AREA (m2):________ PHOTOS:_____||SOIL SAMPLE:_____|
|SOIL TYPE:____________ HUMUS TYPE:______||BEDROCK TYPE:____________|
|LATITUDE-LONG. (or map):____________________|
|1. Elevation _____ m|
|2. Aspect _____ degrees|
|3. Slope _____ %|
|4. Topo. position _____ 1-6||1=crest
|5. Drainage _____ 1 - 6||1=excessive
|6. Flooding _____ 1 - 6||1=never
3=tempor.< 6 mo.
4=tempor. > 6 mo.
|7. Outcrops _____ %|
|8. Surficial material ___ 1 - 6||1=bedrock
|9. Rocks in soil _____ 0 - 5||0=0%
|10. Soil depth _____ cm|
|11. Charcoal _____ 0 - 3|
|12. Mottles _____ 0 - 3||0=absent
|13. Watertable _____ 0 - 1||0=below 30 cm
1=above 30 cm
|14. Light _____ 1 - 3||1=open
|15. Seepage _____ Y / N|
|16. Sketch and comments|
Appendix 2: "Vegetation data" field form
SITE NO.:_________ NAME OF SITE:_______________________________
% COVER OF STRATA TREE:____ SHRUB:____ HERB:____ MOSS:_____
SPECIES and % COVER CLASS (1 = 0-1%; 2 = 1-5; 3 = 5-25; 4 = 25-50; 5 = 50-75; 6 = 75-100)
Appendix 3: "Ginseng data" field form
SITE NO.:_________ NAME OF SITE:_______________________________
No., Height, Leaves (% browse), Leaflets (1 leaf), Flowers, Fruit (abort. or pred.), Seeds
Figure 1: Example of a location map of individual ginseng plants within an intensively monitored population
Map drawn to scale (1 m = 1/4 inch) with permanent features indicated (trees, logs, rocks, streams, etc.). Center line (following a compass bearing) starts at large conspicuous tree. Invidual ginseng plant locations are mapped (and sequentially numbered) on both sides of this center line. Dense groups of plants are mapped in enlarged map sections to provide enough detail to accurately relocate individuals (enlargements can be placed on a separate sheet)
Figure 2: Diagram of ginseng plant showing types of measurements needed for demographic analysis
Sixe-class 2 (determined by number of leaves or prongs) ginseng plant showing height (H) measurement between soil surface and base of leaf petioles. Inflorescence with fruit (Fr) shows how flowers can be counted by adding aborted flowers (Fl) to fruit count (peduncles remain). Top view of fruits containing one seed (1), two seeds (2) and three seeds (3)