Grand Canyon National Park, in collaboration with partners, is conducting a pilot stewardship project at Granite Camp and within the Monument Creek Watershed.
This is a very popular area for backcountry and river users, but like many areas within the Colorado River corridor has been adversely impacted by the operations of Glen Canyon Dam, high recreational use, and the introduction of non-native plant species, particularly tamarisk (Tamarix ramosissima).
The goals of this pilot project are to rehabilitate the native riparian plant community and wildlife habitat, recover data from and stabilize a threatened prehistoric archeological site, and enrich the overall visitor experience.
The work at Granite Camp will be completed in phases. The first phase began with an assessment of current site conditions that included a vegetation inventory, soil sampling, and the installation of temporary groundwater monitoring wells to measure the distance to ground water. The second phase consisted of large scale tamarisk removal throughout designated areas of the camp and the third phase involved planting the site with a variety of native vegetation. Park staff will continue to monitor the site for the next several years.
Work crews will be present intermittently at the site through the fall 2013. While all efforts will be made to minimize impacts to visitors, on-site work may still be disruptive and limit opportunities for a wilderness experience.
The Big Picture
Park staff collaborated with Fred Phillips Consulting to develop a comprehensive rehabilitation design and implementation plan that incorporates lessons learned from similar projects elsewhere along the Colorado River.
The ultimate goals were to remove selected tamarisk, replace those tamarisk with native species, and conduct long-term monitoring to continue to improve the understanding of riparian rehabilitation along the river.
The primary vegetation treatment area begins at the river camp and continues downriver from the boat docking and kitchen areas to the confluence with Monument Creek. Crews conducted selective tamarisk removal at the upstream end of camp (near the groover site) to promote growth of willows and baccharis currently along the river. Every effort was made to maintain the functionality of the camp and improve the overall visitor experience at the site..
It is important to note that not all tamarisk were or will be removed within the treatment area and that none of the mature tamarisk that provide shade and are used as boat anchors will be removed as part of this project.
Tamarisk trees were removed using only hand tools. Tree branches were cut back until only a stump of remained. Crews then excabated the stumps by digging down, cutting the stump several inches below the ground surface and treating the cut stumps with herbicide. Minimal amounts of aquatic approved herbicide were applied trees to prevent re-sprouting. The wood and vegetative debris was then disposed of into the river.
Crews worked one week a month November-February to remove 1,584 tamarisk trees from the site. The majority of the work was done by volunteers who donated 1,575 hours to the project.
Native Plant Rehabilitation
In January and February, park staff and volunteers collected 118 coyote willow (Salix exigua) poles from Bright Angel Creek, 23 Goodding's willow (Salix gooddingii) from along the Colorado River and 24 total cottonwoods (Populus fremontii) from both Nankoweap and Kwagunt Canyons. The dormant poles were cut to lengths of 7 feet and soaked in the creek or river 4-14 days. Soaking the poles allows them to fill with water and once they are planted in the sand, they can begin to send out roots. Working with volunteers and a crew from Canyon Explorations river company, staff were able to plant all of the poles over five days. The cottonwoods and Goodding's willow were caged to protect them from beaver herbivory.
Staff began collecting seeds and cuttings during the summer of 2012 that were grown out in the nursery on the South Rim and at Signature Botanica in Phoenix. Those plants took a helicopter ride from the South Rim to Granite Camp in early April. Park staff partnered with NPS volunteers and participants on a training trip sponsored by the Grand Canyon River Guides Association to plant the site. They were able to plant 94 trees (mesquite, acacia, hackberry, willows and cottonwoods); 137 shrubs and forbs (sacred datura, brittlebush, Mormon tea, preleaf, Chuckwalla's delight, and monkey flower) and 295 grasses or grass-like plants (satintail, scratchgrass and rush). Many of these plants will need supplemental water throughout the next two years and volunteers on river and backpacking trips will spend time at Granite Camp watering these news plants.
For volunteer opportunities with this project, email the project lead.
Tamarisk Leaf Beetles
After years of controlled studies, researchers released the northern tamarisk leaf beetle in a number of locations throughout the west in 2001. As a biological control agent for non-native tamarisk trees, tamarisk leaf beetles and their larvae feed exclusively on tamarisk foliage. The larvae induce the most damage by completely defoliating the trees.
The beetles may have two to three generations each year meaning the trees may be subjected to multiple successive defoliation events.
Current research indicates that trees that are already water- or nutrient-stressed may not survive the multiple defoliations and could die within three to five years. However, in some cases, the trees may be able to survive defoliation and continue to re-sprout.
Due to specific light requirements during beetle development, researchers assumed that the beetle would not survive or spread below the 38th parallel, which is north of Grand Canyon National Park. However, in 2009, tamarisk beetles were documented within the park. The beetles have spread rapidly throughout the canyon and, as of August 2012, have been found from Glen Canyon Dam to the Little Colorado River and again just below Horn Creek, continuing intermittently to Lake Mead. Due to the spread, the gap between the Little Colorado River and Horn Creek will likely be closed within the next year.
The potential for widespread tamarisk mortality along the Colorado River in Grand Canyon National Park has unknown impacts to the riparian ecosystem, as well as to visitor experience. Tamarisk trees currently provide habitat for a variety of wildlife species as well as shade and tie-off points for boaters.
Actual rates of tree mortality due to the tamarisk beetle are still unknown. Park staff has observed some tamarisk stands in Grand Canyon, for example near Deer Creek and Lava Falls that are almost completely dead. Researchers in Colorado and Utah have found that as tamarisk die from continued defoliation, native vegetation like willows and acacias gradually fill the empty niche.
There is also the potential threat of exotic plants species replacing the dead tamarisk, but little information is available at this point.
The arrival of the tamarisk leaf beetle within Grand Canyon National Park provided an impetus for developing a more integrated approach to resource stewardship along the river. While the beetle has not yet arrived at Granite Camp, results from this pilot project will help park staff to assess the feasibility of removing tamarisk and proactively planting native species at priority sites along the river corridor.
Archeological Site Excavation
An archeological excavation of a small site along Monument Creek occurred in early May 2012. The site consisted of multiple fire, or hearth, features visible in the drainage bank and a structure on the terrace top.
Archeologists found three distinct occupations of the site: an early Basketmaker period (1000 BCE to 500 CE) one based on charcoal present in the fire features along the drainage bank, and two ancestral Puebloan ones. A Pueblo I (800-1000 CE) use was evident from the pottery found inside a small hearth, and the Pueblo II (1000-1150 CE) occupation was determined by the construction style of structure.
Prior to starting the excavation, the crew met on-site with vegetation staff to determine appropriate plants to remove and cache during the excavation and to identify re-seeding efforts.
Upon completion of the excavation, the area was completely backfilled and the slope re-contoured to reduce the likelihood of additional erosion of the area. The site continues to be monitored to ensure successful rehabilitation.