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Elmore, AJ, Manning, SJ, Mustard, JF, and Craine JS (2006) Decline in alkali meadow vegetation cover in California: the effects of groundwater extraction and drought. Journal of Applied Ecology, 43:770-779 In a Nutshell: Problem - Throughout arid regions of the world, groundwater is extracted to human population centers without regard to how groundwater decline impacts overlying vegetation. This is particularly true for alkali meadow vegetation in the Great Basin and Range region of the United States. Here, meadows are restricted to zones of shallow groundwater that are being actively pumped. What - To increase understanding of the relative importance of groundwater and precipitation in maintaining alkali meadow vegetation cover, we use a 16-year record of plant cover derived from satellite data of Owens Valley, California, USA, in conjunction with concurrent depth-to-water and meteorological measurements to analyze vegetation response to variability in groundwater (range: 0.5 to 5.0 m) and precipitation (including a 5 year drought). Findings - Meadow plant cover over the 16-year study period was correlated with groundwater depth, but plant cover was generally unresponsive to annual precipitation variability and drought. The results show that these desert meadows are groundwater dependent, and that this characteristic buffers the system from drought. At sites with extensive groundwater decline, remaining plant cover became weakly correlated with precipitation only after groundwater declined below a threshold depth located at 2.5m, representing the average plant rooting depth. Application - Sustainable water development that seeks to pump groundwater without adversely affecting vegetation cover and plant assemblages must recognize the maximum rooting depth of groundwater-dependent plant species. When groundwater is within the root zone, management decisions can be made to either increase or decrease vegetation cover through modification of groundwater depth. When groundwater is below the root zone, vegetation cover is low and susceptible to changes in precipitation. Quantitative satellite measurements of vegetation cover might aid in monitoring and sustainable management of water resources. |
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