Grand Canyon National Park, in collaboration with other 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 spp.).
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, starting with an assessment of current site conditions that includes a vegetation inventory, soil sampling, and the installation of temporary groundwater monitoring wells.
Work crews will be present intermittently at the site through the spring 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.
Consultation in Monument Creek.
Tamarisk Removal and Native Vegetation Planting
Park staff is currently working 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 are to remove selected tamarisk using a variety of methods, replace those tamarisk with native species, and conduct long-term monitoring to continue to improve the understanding of riparian rehabilitation along the river.
Primary vegetation treatment area.
The primary vegetation treatment area will be at the river camp, downriver from the boat docking and kitchen areas to the confluence with Monument Creek. Starting in fall 2012, some tamarisk will be selectively controlled and removed within the treatment area.
It is important to note that not all tamarisk 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.
There may be selective and limited tamarisk removal at the upstream end of camp to promote growth of willows and baccharis currently along the river. Every effort will be made to maintain the functionality of the camp and improve the overall visitor experience at the site. The work will be implemented in phases using a relatively 'light touch' since mass tamarisk removal could jeopardize the structure and stability of the beach..
Large tamarisk to be removed.
Tamarisk trees will be killed and/or removed using a variety of methods including girdling (trees remain standing but with a one inch deep cut around the circumference of the trunk to mimick trees killed by tamarisk leaf beetles), cut stump (removing trees to ground level by cutting), and complete excavation of trees.
Minimal amounts of aquatic approved herbicide will be applied to girdled and cut stump trees to prevent re-sprouting.
The wood and vegetative debris will be cut into smaller pieces and disposed of into the river. Impacts to boaters will be minimized during wood disposal in the river. If possible, the wood will be released into the river during a high flow event to increase dispersal downstream.
In 2013, native species, including coyote willow, Goodding's willow, cottonwood, twining snapdragon, twining milkweed, Arizona grape, brittlebush, wolfberry, and Mormon tea, will be planted at the site.
Park staff has been collecting seeds and cuttings of native plants to replant at Granite Camp. These plantings will require frequent watering by hand and/or drip irrigation to become successfully established. Some plant species that will be planted at the site, such as Goodding's willow and cottonwood, will also need to be caged to protect them from beaver herbivory. These native trees will provide replacement habitat and shade.
For volunteer opportunities with this project, visit:
http://www.gcvolunteers.org or email the project lead here.
NPS photo: Glen Canyon NRA
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 tamerisk 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.
Camp trees will remain.
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.
What the temporary wells look like.
Temporary Groundwater Monitoring Wells
Five groundwater monitoring wells were installed in early June 2012 to collect data on the depth to groundwater, water temperature, fluctuations with river stage and water quality.
The wells are sunk approximately eleven feet below the surface and have two foot risers above ground which are metal pipes. Inside the risers is a pressure transducer and data logger that records water level and temperature every 15 minutes.
An additional monitoring well in the river measures fluctuations in river flow. Water quality measurements for salinity, pH, specific conductivity, and dissolved oxygen are also periodically collected from the monitoring wells.
Data from the monitoring wells will be used to determine appropriate planting locations for particular species. It is important to plant water-loving species like willows in areas where they will have access to groundwater. The wells are temporary and will be removed when staff has collected adequate data on groundwater levels to analyze beach aquifer characteristics.
Excavating Monument Creek site.
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.