Process-based Approaches for Ecological Restoration of Degraded Drylands

Science Center Objects

Surface disturbances ranging from military training, recreation, energy exploration and development, and wildfires impact a large majority of federal lands in the western US, but the ecological and economic impacts are poorly understood. Explore this webpage to learn how Dr. Lesley DeFalco and her research team are currently evaluating and refining conventional approaches for post-fire restoration of Mojave desert tortoise critical habitat and developing ecological restoration strategies for shrubland communities impacted by energy exploration and development on the Colorado Plateau.

WERC Cones protect seedlings of the native shrubs
Cones protect seedlings of the native shrubs blackbrush (Coleogyne ramosissima) and Nevada joint-fir (Ephedra nevadensis) planted after a wildfire at Red Rock National Conservation Area, Nevada(Credit: Lesley DeFalco, USGS WERC. Public domain.)

Evaluation and refinement of conventional approaches for post-fire restoration of Mojave desert tortoise critical habitat

The Mojave Desert spans southern California, Nevada, and Utah and northwestern Arizona with 37% of the land area comprised of low elevation shrublands, which are habitat for the federally-listed Mojave desert tortoise (Gopherus agassizii). Increasing prevalence of wildfires fueled by invasive annual plants threatens the recovery of the species, with recent wildfires burning an unprecedented 1 million acres of shrublands and a loss of 4% of critical habitat designated for the desert tortoise. Mojave Desert shrublands are poorly adapted to recover from wildfires because re-sprouting doesn’t ensure shrub survival, native soil seed banks important for regeneration are decimated by surface disturbances, and invasive grasses rapidly dominate disturbances, thus promoting further habitat degradation. Furthermore, conventional restoration practices often fail because seed predators such as ants and rodents gather the majority of seeds broadcast during re-seeding efforts, and jackrabbits consume nursery grown seedlings planted at restoration sites. USGS research focuses on understanding how to reduce dominance of invasive grasses following wildfire, how conventional seeding practices can be improved to establish native plants under Mojave Desert conditions, and how nursery seedling stock can be improved for enduring post-transplanting stress. Experimental restoration trials test the use of invasive grass-specific herbicides, seed encapsulation to discourage seed predators, and outplanting to accelerate natural re-establishment. Research findings from these process-based restoration trials are currently refined for evaluation in a landscape-scale project across multiple burned areas in the northeast Mojave Desert. Novel methods include improving nursery seedling quality and diversionary seeding to test on largescale disturbances. This project is a multi-agency collaboration with Bureau of Land Management, National Park Service, and US Fish and Wildlife Service.

WERC Ants collect seeds/floret
Seed predators such as harvester ants collect the majority of seeds broadcast on the surface of burned areas that are re-seeded(Credit: Lesley DeFalco, USGS WERC. Public domain.)
Seeds of shrubs and perennial grasses encapsulated in soil wafers
Seeds of shrubs and perennial grasses that are difficult to establish via broadcast seeding are encapsulated in soil wafers to protect them from ants and rodents while they await conditions for germination.(Credit: Lesley DeFalco, USGS WERC. Public domain.)
Herbicide is applied to burned areas to reduce invasive annual grasses
Herbicide is applied to burned areas to reduce invasive annual grasses and facilitate the re-vegetation of long-lived desert shrubs that are typically difficult to re-establish(Credit: Lesley DeFalco, USGS WERC. Public domain.)
Intern works with USGS to measure species composition of recovering shrubs along a perennial transect
Chicago Botanic Garden Conservation and Land Management intern Jessica Milkenas works with USGS to measure species composition of recovering shrubs along a perennial transect positioned in an abandoned drill pad. Many recovering pads are colonized by short-lived species such as snakeweed, and the community dominants are difficult to recover on their own(Credit: Lesley DeFalco, USGS WERC. Public domain.)

Ecological restoration of shrubland communities impacted by energy exploration and development on the Colorado Plateau of Utah

Energy exploration and development have altered shrublands on the Colorado Plateau during the past century, and long-lived community-dominants are particularly difficult to recover. Blackbrush (Coleogyne ramossisima) and sagebrush (Artemisia spp.) form stable communities that resist environmental fluctuations but are vulnerable to surface disturbances that remove mature vegetation and alter topsoil. Energy exploration and development activities disrupt the shrub matrix and de-stabilize soils. The result is often dominance by early-colonizing forbs and invasive annuals and soil loss. Intervention is required early in the successional process to reestablish ecological function. USGS, Western Ecological Research Center performs studies on the ecological restoration of roads and oil and gas exploration pads on the Colorado Plateau in Utah. This research is a collaborative effort with USGS – Southwest Biological Science Center, USGS – Fort Collins Science Center, and Texas State University – San Marcos. Vegetation monitoring and dendrochronology sampling on a chronosequence of drill pads that have recovered over 80 years and undisturbed reference sites is revealing the importance of climate and recovery time on vegetation reassembly.