![]() To improve understanding of the linkages between abiotic processes and biotic communities and how they are influenced by hydroclimatology and anthropogenic land and water use, SERDP researchers also are studying three sites across the Sonoran Desert and southeastern Arizona that represent stream systems differing in duration, intensity, and frequency of seasonal precipitation events and water table depths. Quantitative models that forecast the ecological and genetic consequences of altered hydrologic connectivity will help identify aquatic taxa whose persistence are particularly jeopardized and that may require active management efforts such as corridor connections, translocations, or water management. Researchers are assessing whether these ecological functions will be maintained in a changing climate. How intermittent and ephemeral streams provide critical habitat and population connectivity for aquatic species (insects and amphibians) is the subject of SERDP research at Fort Huachuca in southeastern Arizona. The resulting tools will enable DoD land managers to map stream types and evaluate the impacts of perturbations on the hydrologic regimes of these systems and the species that depend on them. They are also characterizing streams and developing a stream hydrogeomorphic classification system incorporating key physical process drivers that create and support riverine and riparian landforms, hydrologic regimes, and biota in the Sonoran Desert. SERDP researchers are assessing intermittent and ephemeral streams at sites across the southwestern United States to develop a landscape-scale classification and measurement methodology that distinguishes channel types by a set of biotic and abiotic attributes, which are directly related to their hydrologic regime. Intermittent and ephemeral streams transport and retain water, nutrients, sediments, and organic matter episodically in their networks and associated floodplains, support the establishment and maintenance of riparian vegetation, and provide ecologic and hydrologic connectivity to uplands and to downstream perennial watercourses. These dryland streams and their associated riparian zones play a significant role in supporting the biological diversity of this region. More than 80 percent of all streams in the six southwestern states-Arizona, New Mexico, Utah, Nevada, Colorado, and California-are intermittent or ephemeral (only flow during rain events). Intermittent and Ephemeral Stream Systems They are also examining the population strategies used by non-native plants to spread into areas between desert shrubs, increasing fuel loads and changing desert communities and landscapes. SERDP researchers are developing decision-support tools that DoD and other land managers can use to more effectively and efficiently manage non-native invasive plant species and wildfire in the Sonoran and Mojave Deserts now and under changing climate conditions. The individual and synergistic impacts of invasive plants, fire, and global climate change on native habitats will affect threatened, sensitive, or at-risk species in complex ways. Future shifts in climate could affect the relative abundances of these vegetation types and increase the dominance of non-native invasive plants. Plant invasions have had their greatest effects on fire regimes at lower elevations, especially in desert scrub systems. Interactions between plant invasion and increases in fire frequency and magnitude are a growing concern in the Southwest. Altered Fire Regimes and Non-Native Invasive Plants Global climate change also will result in region-specific changes in temperature, precipitation regimes, and extreme weather events including drought that will exacerbate these impacts. Human population pressure and associated land-use activity, altered hydrologic regimes, and non-native species introductions are relatively new perturbations in this region. The long-term use of these lands depends, in part, on the ability to maintain the continued ecological functioning of the land base. This work will help the Department of Defense sustain military training and testing capabilities in the Southwest. SERDP researchers are developing the science and tools needed to manage and recover ecosystems on military installations and ranges in the southwestern United States.
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