Plant species are threatened by human activities in the same ways that animals are (see Information Paper 5). Habitat destruction isolates and reduces the number and size of plant populations which then become highly susceptible to extinction. In addition many plants are threatened directly by overharvesting (e.g., tropical orchids, rare cacti, carnivorous plants), trampling and "predation" by exotic animals (such as cattle, sheep, feral pigs), competition with exotic plants, and epidemic disease caused by introduced pathogens (such as the chestnut blight, an introduced fungus which virtually wiped out the native American chestnut tree in the eastern U.S.). In Glacier National Park plants are protected from harvesting, but in some areas perhaps most noticeably around the intensely used Logan Pass area portions of plant communities have been destroyed by the construction of roads, parking areas, visitor facilities, and trails. At least 128 exotic plant species have been recorded in the park; spotted knapweed (Centaurea maculosa) is of particular concern because of its ability to spread rapidly and displace native plant communities (NPS 1989).

Although plants and animals face similar threats from human activities, there are important differences between plants and animals that must be considered when managing plant populations. Some of these differences involve mobility, reproductive strategies, genetic structure, population structure, response to natural disturbance, and interactions with other organisms. (The discussion of these factors below is based almost entirely on Huenneke et al. 1986). Current research in Glacier is addressing some of these factors; others will be investigated in future projects.

About Plants
It's not easy being green. The most obvious difference between plants and animals is that individual plants are sessile they can't move. Their lack of mobility means that plants are at the mercy of local conditions. Variations in rainfall and other abiotic factors or the vigor of neighboring plants may greatly affect an individual plant's growth rate, chance of survival, and reproductive success. If not enough rain falls one season or if another plant casts a shadow, a plant cannot simply pick up and move to a wetter or sunnier spot. Plants cannot actively escape from herbivores, a vibram sole, or a backhoe. The only mobile parts of a plant are its seeds and its pollen which are dispersed either by gravity, wind, water, or some kind of animal (mammal, bird, insect, sometimes even fish in tropical flood basins). But the vast majority of seeds, even those that are wind-dispersed, are destined to fall within only a few meters of their parent plant; and if they happen to fall on an inhospitable site, seeds cannot move themselves to one that is more favorable for germination.

Sex lives of plants. Although to most people plants don't have the sex appeal of lions, tigers, and bears, in fact plants exhibit an amazing, almost bewildering array of reproductive strategies far more so than do vertebrates. These range from asexual cloning via underground roots or stems (vegetative growth), to self-fertilization, to obligate outcrossing (plants have various mechanisms that prevent them from pollinating themselves), with everything in between. Furthermore, many plants can switch from one strategy to another depending on environmental conditions. Examples of this reproductive spectrum in Glacier range from aspens (Populus tremuloides) at one extreme (although aspens can reproduce sexually, clonal growth is much more common; most aspen groves are, genetically speaking, single individuals) to russett buffalo-berry (Shepherdia canadensis) or Rocky Mountain maple (Acer glabrum) at the other extreme (these species are dioecious: male flowers and female flowers grow on separate plants, so that the plants must outcross to breed).

The birds and the bees. A plant's survival may be entirely dependent upon the activity of one or a handful of other species. Some plants are wind-pollinated (e.g., grasses, pine trees), but most flowering plants rely on beetles, flies, bees, moths, butterflies, birds, or bats to transport pollen from one flower to another; these animals are a vital link in the plants' reproductive cycles. The bright, colorful flowers or juicy fruits borne by many plants have evolved for the sole purpose of attracting pollinators or seed dispersers. Frugivores (fruit-eaters) may not only aid in seed dispersal, they may be a necessary part of seed germination. Perhaps the most famous example of this is the tree Calvaria major on the island of Mauritius. It was noticed in recent years that although mature trees of this species were producing fruit, no new trees were germinating, and, hence, as older trees died out the species was slowly going extinct. It was discovered this tree had coevolved with the now-extinct dodo bird which ate the fruits of this tree; the seed scarification that occurred in the dodo's gizzard was a requisite precursor to the seeds' germination (Temple 1977). Effective plant conservation clearly must include conservation of plants' mutualistic relationships with other species.

Genetic diversity. The plasticity plants exhibit their ability to respond to differing conditions with different breeding systems and growth patterns reflects the underlying wealth of genetic diversity within and between plant populations and species, again a diversity much greater than that exhibited by vertebrate species.

Because plants can't move there can be a great deal of genetic differentiation in a small area especially within populations of self-fertilizing plants (in other words, since individuals in these populations don't get mixed up a lot, genetic differences may be preserved on a very small scale). Within the same population, covering only a few tens of meters, there may be several distinct genotypes (individuals sharing the same genetic constitution) adapted to take advantage of different conditions. Some members, for instance, may be adapted to drought, while others will grow only under normal moisture conditions. Some of these genotypes may be common, others may be rare. In managing such a population, awareness of such within-population genetic diversity can make an important difference in assuring that population's long-term survival. For example, if a portion of such a population must be disturbed, which portion is chosen may make a big difference in how much genetic diversity the population loses.

Plants can exhibit significant between-population genetic diversity as well, especially within a widespread species. This phenomenon is known as ecotypic differentiation. In yarrow (Achillea millefolium), for example, which grows in Glacier National Park and has a circumboreal distribution, some populations are identified as separate races because they are genetically distinct and adapted to specific climate and soil conditions. When grown in the same field, yarrow grown from seed collected on the east side of Glacier has a bluer tinge than plants grown from seed collected on the west side a variation which probably indicates the presence of different ecotypes within the park (R. Potter, pers. commun.). In a plant species (or animal species for that matter) that exhibits such ecotypic variation, many isolated populations may need protection in order to conserve as much of the entire range of the species' genetic diversity as possible.

Seed banks. Another important difference between plants and animals is that a significant portion of a plant's population may be "invisible" in the form of dormant seeds in the soil. This seed bank can serve as a buffer against environmental, demographic, and genetic stochasticity (see Information Paper 5 for definitions of these terrns). In the event of a fire or a failure of plants to reproduce one year, the seed bank can provide new plants as soon as conditions are suitable for germination. And if viable seeds accumulate in the soil over growing seasons or years, the seed bank serves as a reservoir of the different genotypes of a population that are adapted to different conditions and prevents the loss of genetic variability through genetic drift (see Information Paper 5). (Artificial seed banks assembled by humans may be able to serve the same buffering function.)

Both seed banks and clonal growth pose practical problems for plant researchers and managers. It is generally assumed that plants are much easier to study than animals because they can't move around or hide. Some species are in fact easy to observe and census. But in the field it is impossible to count the invisible individuals in the soil soil samples must be taken for examination in a lab to find out if there is a seed bank and to estimate its size. Furthermore, with most vertebrates, the number of bodies equals the number of genetic individuals; but there are usually far more above-ground stems of grass or trunks of aspens than there are genetic individuals. Tracing underground connections (like rhizomes) between such plants may destroy the population, and in any event such connections often rot away over time. In such clonal plants, it may be difficult or impossible to identify individuals without resorting to sophisticated genetic analyses like gel electrophoresis.

Natural disturbance. Humans have been inclined in the past to view disturbance and change in nature as bad things. We are recognizing more and more, however, that disturbance is a natural process, and that in fact many species, particularly plants, have evolved means of not just coping with disturbance but taking advantage of it. In Glacier, as in many temperate ecosystems, one of the more prominent natural disturbances is fire. Some plants and plant communities here not only benefit from fires but actually depend on fire for their regeneration. For example, in addition to producing normal cones, lodgepole pines (Pinus contorta) produce serotinous cones cones that do not release their seeds until the heat of a fire melts the resins which hold the cone closed. Furthermore, lodgepole seedlings grow much better in the open areas created by fire. As a forest matures and the tree canopy closes, limiting the amount of sunlight that reaches the forest floor, lodgepole may be unsuccessful in competing with more shade tolerant species, and hence may die out. Another plant with physiological adaptations to disturbance is the aspen. Mature aspen can produce flowering buds and seeds through normal sexual reproduction. The buds send the hormone auxin to the roots to inhibit vegetative sprouting of new shoots. But if a fire or avalanche destroys the above-ground portion of the tree and the buds with it, the hormone is no longer sent and the root system quickly generates new sprouts to recolonize the burned area (Schier et al. 1985).

In managing plants it is important to consider the scale, frequency, and intensity of natural disturbances under which those plants have evolved. In Glacier, where lightning-caused fires were a common occurrence before this century, fire suppression may result in the loss of some plant and community diversity and in an unnatural aging of forests which then may be highly susceptible to epidemic disease outbreaks (e.g., mountain pine beetle). Other human disturbances that appear superficially to mimic natural disturbances often have completely different consequences because plants are not adapted to their intensity or frequency. Plants that can survive periodic light fires may be completely killed by extremely hot or unusually frequent fires. A riparian shrub that will germinate only on recently flooded gravel beds may be completely wiped out by inundation from a dam. Gopher, ground squirrel, and badger mounds may provide favorable sites for some seedling establishment while bulldozer tracks or even footsteps in a fragile alpine meadow may prohibit natural revegetation for years.

Vegetation Management in Glacier
Maintenance of native plant and animal diversity is a fundamental goal in natural zones of national parks (NPS 1988), and 99% of Glacier is classified as natural (NPS 1985). However, there are very few plant species for which we have the kinds of information described above (population structure, genetic diversity, dependence on particular mutualist species and natural disturbances, etc.). With the help of outside researchers Glacier's staff is working to remedy this information gap and address the special conservation needs of plants through several ongoing research and management projects. These fall under three broad categories: site restoration, exotic plant management, and fire management. In addition to these efforts the park's inventory and monitoring program (see Information Papers 4 and 8) will contribute to vegetation management by providing information on the distribution of plant species and communities in the park and changes in these distributions over time.

Site restoration. In keeping with the NPS policy of maintaining native species within naturally functioning ecosystems (NPS 1988), the resource management staff in Glacier is working to prevent vegetation disturbance in areas that receive heavy foot traffic (such as backcountry campgrounds and frontcountry trails) and to revegetate frontcountry sites that have been disturbed by construction or other activities.

The most visible revegetation effort has been the ongoing project to conserve and restore the subalpine vegetation around the Logan Pass Visitor Center that was disturbed during building and walkway renovation from 1986-1988 (Filipiak 1987). Current efforts are centered on preparations to mitigate vegetation disturbance that will be caused by the improvements to be made on the Going-to -the-Sun Road (GTSR). Specific projects have included:

1. Collection of seeds to use in revegetation.
2. Construction of a nursery in West Glacier in which to raise plants from seeds and cuttings and experiment with propagation techniques.
3. Surveys along the Lake McDonald section of the GTSR to inventory plants and identify any rare plant populations that might be adversely affected by road construction (no native rare plants were found).
4. Photo documentation to compare vegetation recovery since road construction in the 1930s and to monitor future changes along the road.
5. Study of natural seed fall along the GTSR to determine the extent to which natural regeneration can be expected to recover disturbed sites.
6. Experiments on the Coram Experimental Forest (on Flathead National Forest) to test methods for revegetating road cuts and ditches using beargrass (Xerophyllum tenax) and pinegrass (Calamagrostis rubescens) seeds and plants and other native and nonnative plant species (Potter 1987, Potter et al. 1989). (Based on the results of these experiments beargrass has now successfully being used to revegetate the areas around park headquarters that were disturbed by the burial of powerlines [Lapp 1989].)

In collecting seeds and cuttings, efforts are being made to utilize plants that are as close as possible geographically to the areas to be revegetated, from similar habitat types located at the same elevation and aspect, in order to preserve the genetic diversity of native plant populations (see Millar & Libby 1990 for a discussion of the effects of moving plant materials on genetic diversity). In practice it has been necessary to collect some seeds and cuttings from outside of the park and in different habitat types (Potter 1987). Two current research projects are investigating the genetic variability of plant species across environmental and geographic gradients. Strawberry is first being subjected to lab analysis to determine cellular genetic differences between populations at different locations. Individual plants gathered from the park are then propagated at three different elevations--in gardens at West Glacier, a relatively low altitude, at St. Mary which is somewhat higher, and at a high altitude site in the Whitefish Mountain range. Morphological differences between the plants are observed (such as number of flowers and length of stolons) to determine if these characteristics are peculiar to a genetic population, and if they respond to different environments: are these genetic differences important to plant survival? Results so far indicate that populations from the east side of the Continental Divide differ markedly from those taken at Logan Pass and the west side, which tend to be more similar. With this information researchers will gain a better idea of the genetic consequences of transplanting species and they will be able to develop practical guidelines for plant material collection that will minimize the loss of genetic diversity on restored sites (L. Kurth, pers. commun.).

Most of the seeds collected in and around the park are sent to the Soil Conservation Service's Plant Materials Center where they are sorted, cleaned, and used to produce materials for transplanting on revegetation sites. Out of this activity a second study has arisen to investigate the possibility that planting, harvesting and replanting seeds over a few generations in greenhouses and nurseries will cause genetic drift and loss of genetic variability in transplanted populations. To test for this possibility, mountain brome is being analyzed on the genetic level (much like the strawberry). The seed which is sown at Bridger Plant Material Center matures and produces its own seed, which in turn is subjected to electrophoresis at the University of Montana. Over time it should be possible to determine how much difference at the genetic level it makes to raise plants in the hotter, drier climate of Bridger rather than in the park itself. It should be possible to generalize from the mountain brome study to other plant species.

The park's resource management staff have been actively enlisting community involvement in their revegetation projects. For several years the general public along with members of the Montana Native Plant Society have been invited to attend a Logan Pass Seed Collection Day, and volunteers help in the nursery as well. The success of these activities attests to a growing interest in native plants and habitat restoration. Additional events to educate the public and to encourage the active participation of ecosystem residents in vegetation management are being planned (R. Potter, pers. commun.).

Exotic plant management. Not only are exotic species, by definition, unnatural members of Glacier's communities, they may contribute to the decline of native species and the deterioration of natural habitats. Spotted knapweed (Centaurea maculosa), for example, rapidly invades disturbed areas, but also is a potentially aggressive invader of undisturbed sites where it displaces native vegetation (Tyser & Key 1988). Furthermore, exotics like knapweed are agricultural weeds outside of the park and their eradication is of economic importance to the region's farmers and ranchers. Other particularly noxious weeds in Glacier are leafy spurge (Euphorbia esula), St. Johnswort (Hypericum perforatum), and oxeye daisy (Chrysanthemum leucanthemum) (NPS 1988).

Management actions in the park to control the spread of these species may include: mechanical removal of plants (pulling, cutting, mowing); cultural methods (revegetation, burning); biological controls (e.g., introducing insects that feed on exotics); and chemical treatments (herbicides). The park seeks to use a combination of these methods for each site that will be the most effective in controlling the exotics while minimizing alteration of native communities, an approach known as Integrated Pest Management (NPS 1988). Other components of Glacier's exotic management policy include prevention of exotic plant dispersal (e.g., not permitting hay, which is primarily composed of exotic plants and their seeds, to be taken into the backcountry to feed stock) and public education. Interpreters have, for example, engaged visitors in pulling exotic plants like spotted knapweed and butter-and-eggs (Linaria vulgaris) during interpretive programs which also provide information on the impacts of exotic species on biodiversity (see NH 4.20, 5.11). Perhaps the single most important component of Glacier's exotic plant program is minimizing human-caused vegetation and soil disturbances and thereby minimizing the size and number of optimal sites for these plants to invade (R. Potter, pers. commun.).

Fire management. Following the fires of 1988 all western parks were required to review their fire management plans. At this time all of Glacier National Park is in a "prescribed natural fire unit" in which the goal is to allow fire to play its natural role as much as possible (i.e., while protecting human lives and property). Because of the high hazard on the east side and along some of the western boundary, these areas are out of prescription between March 15 and December 15 each year (meaning that the park would attempt to suppress any fires begun in that period regardless of their cause). In other areas, especially along the west boundary of the Park, units go in and out of prescription on a daily basis depending on how the fire management plan evaluates factors such as time of year, drought, location, soil condition, and current weather. In the event of a lightning-caused fire, a process of decision analysis determines what the maximum allowable perimeter of the fire will be. The fire is monitored daily; if it should exceed that perimeter, it would go into a suppression mode. Prescribed natural fires are thus distinguished from wildfire, which is a fire that is unacceptable because of current fire conditions or the potential damage it might do.

Management ignited prescribed fires (MIPFs) are also a part of Glacier National Park's fire management plan. Their function is to restore fire to its natural role in communities where fire has been absent for longer than normal. In 1992 two MIPFs were set in the prairies of the North Fork, areas which had not burned in over sixty years although the natural fire period has been about twenty years. The unnatural absence of fire has allowed young lodgepole pines to encroach on the meadows, beginning a succession to a forest community which would not occur under a natural fire regime. In Round Prairie, in particular, sagebrush have begun to dominate the meadow, changing the species composition of the community as it would have been under a natural twenty-year cycle. MIPFs attempt to restore the fire climax community--in this case, prairie--to its natural condition.

The park's fire history has now been completed in the Missouri drainage; the Waterton valley and Belly River areas will be studied in 1993. Field research continues on the firelines bulldozed during the Red Bench fire of 1988; although more exotic plants are being found on the rehabilitated dozer lines than in the undisturbed area, with the exception of Kentucky bluegrass they are minimal. The Geographic Information System (GIS) has been used to map and analyze fire patterns on the west side of the park and also to examine the effects of the Red Bench fire. The park's goal is to allow fire to continue its role in maintaining natural communities (L. Kurth, pers. commun.).

Conclusion
To many visitors the most important thing about plant diversity in Glacier is that it provides us with glorious wildflower displays. Indeed the wildflowers, forests, bogs, alpine meadows, and avalanche chutes all contribute to the visual diversity and splendor of Glacier's landscape. But plants also represent a complex universe in and of themselves, a universe we are utterly dependent upon but are only beginning to understand, a universe whose future depends on our ability and our will to uncover its secrets.

Author: Karen J. Schmidt.

References

Barrett, S.W., S.F. Arno, and C.H. Key. 1991. Fire regimes of western larch-lodgepole pine forests in Glacier National Park, Montana. Can. J. For. Res. 21:1711-1720.

Schulhof, R. 1989. Public perception of native vegetation. Restoration and Management Notes 7(2):6172.