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Activities

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[ || Soil Moisture || Geology & Soil Texture || Biological Soil Crusts || Fire || Vegetation Dynamics || Soil Compaction || Wind Erosion || Climate || Repeat Photography || Land Use History || Spatial Modeling || ]

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Mapping and Modeling Current Conditions

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Because vulnerability and recovery times vary across the landscape, RVDE scientists hypothesized that landscape variables such as geology, slope, microclimate, and botanic habitat must influence how quickly an area recovers from human impact. Modeling vulnerability and recoverability therefore requires maps of those landscape factors determined to be most important. Existing geospatial data for the Mojave Desert, such as elevation, roads, hydrography, and Landsat imagery, were collected as part of the Mojave Desert Ecosystem Program, a GIS data clearinghouse.

Starting with these data, RVDE scientists are mapping crucial datasets, such as surficial geology and plant distribution, and modeling various complex landscape characteristics that vary over an area (spatially) and over time (temporally). For example, soil moisture and soil texture are two important physical landscape factors that influence several other components of the ecosystem, including vegetation cover and composition, soil compaction and erosion, and the distribution and cover of biological soil crusts. Hydrologists are working on improved spatial and temporal models of soil moisture and evapotranspiration in the Mojave Desert. Geologists are developing better maps of soil texture by combining maps of surficial geology with soil-sample analyses and topography. Maps of evapotranspiration and soil properties can help predict conditions conducive to biological soil crusts, a very fragile and important element of desert ecosystems.

Information on current disturbance is also important. RVDE scientists are also collecting and analyzing data on recent fire occurrences to better understand fire characteristics in the Mojave Desert. These maps of existing landscape conditions form the base for building vulnerability and recoverability models.

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Understanding the Processes

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RVDE scientists are focusing on common impacts and processes that result from different types of activities, including disturbance or removal of the vegetation, and soil disturbances that result in compaction, destruction of fragile soil crusts, and increased susceptibility to wind erosion. To understand how vegetation recovers, it is also necessary to understand how vegetation changes naturally over time in undisturbed areas of the Mojave Desert.

Scientists are also studying vegetation recovery in disturbed areas, both in terms of amount of vegetation and species composition. Vulnerability to soil compaction, recovery from compaction, vulnerability to wind erosion, and time for recovery of soil crusts are all functions of a number of factors, such as soil moisture and soil texture. RVDE scientists use a variety of experimental techniques to determine the functions involved in these processes.

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Using the Past to Understand the Present

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Studies of areas that were disturbed in the past but have since been abandoned, such as military training areas, ghost towns, roads, and utility rights of way, provide useful data on recovery processes and times. Some of the once-bustling mining towns that thrived in the Mojave during the early 1900s have vanished with almost complete visual recovery of the vegetation, while the sites of other ghost towns are still readily apparent. USGS scientists in the RVDE project are collecting information about conditions in the past to analyze these differences in ecosystem recovery rates and to better understand how the desert recovers.

Analyses of climate history and its influence on vegetation recovery and geomorphic processes (such as overland flow) provide clues as to how vulnerability and recoverability may vary over time. Repeat photography is also a valuable tool in the analysis of recovery. Data from old maps depicting land use history allow a better understanding of the effect of historical land use patterns on current conditions.

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Modeling Vulnerability and Recoverability

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To make this research useful to land managers, RVDE scientists are synthesizing this information into spatial models of vulnerability and recoverability. Existing datasets of the most relevant landscape factors are combined with information gathered during lab and field studies. These tools, which are based on understanding and modeling dynamic processes rather than developing static maps, allow land managers to apply specific, relevant data of various resolutions.

Prototype models are being developed for soil compaction (both vulnerability and recovery), wind erosion vulnerability, soil crust predictions, and vegetation recovery for a part of the Mojave Desert. As these models are refined and additional models developed, they will be combined into a suite of tools that can be used by land managers to provide input for decision-making. For example, assessing the relative vulnerability of several sites could help in choosing the best location and timing for off-road vehicle use or military activities. Analyzing recovery times in various areas could also determine where road closures will be most effective in restoring habitat.

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