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,2 f tIIr,' llrqtacts ("�i a ld I slllfts Precipitation patterns have direct effects on evapo- transpiration and water availability, which are key determinants of the distribution of plant diversity (Kreft and Jetz 2007) and vegetation types (Stephen- son 1990). Although most landscape -scale shifts in vegetation are assumed to have occurred over rela- tively long time scales in the past, rapid changes in future climate are expected to produce major shifts in vegetation (e.g., Saxon et al. 2005). Such rapid responses to altered moisture regimes are not unprec- edented. For example in northern New Mexico in the 1950s, the boundary between semiarid ponder- osa pine forest and pifion- juniper woodland shifted extensively and rapidly through mortality of ponder- osa pines in response to severe drought, with lasting effects (Allen and Breshears 1998). Among pines found in the southeastern United States, longleaf pine may be more tolerant of a range of conditions (NWF 2009), including very dry periods during the growing season, than loblolly and slash pine (Iverson et al. 1999). Among aquatic systems, wetlands will be particularly sensitive to even relatively small changes in precipi- tation. Wetlands that depend primarily on precipi- tation as a water source will be among the habitats most vulnerable. Winter (2000) assessed the vulner- ability of wetlands to changes in climate relative to their position within the hydrologic landscape. He suggested that wetlands located in mountainous regions would be some of the most vulnerable to climate change due to their location within relatively small watersheds and dependence on precipitation inputs. For the organisms that are dependent on these ecological systems for specific portions of their life cycles, changes in precipitation patterns through- out the year can be as significant, if not more so, than changes in total or mean precipitation (Virginia Burkett and Kusler 2000). A number of amphibian species, for example, are sensitive to the amount and timing of precipitation for successful reproduction. Analysis of population trends over a 26 -year peri- od in South Carolina showed that declines in four species were associated with insufficient rainfall and a shortened hydroperiod at breeding sites (Daszak et al. 2005). Wetlands associated with surface water, such as ripar- ian wetlands, will be dependent on the hydrologic impacts of climate change on the stream flow. Those wetlands located in broad basins of interior drain- age often depend on stream flow originating from precipitation in the contiguous uplands, with much smaller contributions from ground water and precip- itation. They will therefore be highly dependent on precipitation regimes in the contiguous uplands and will also be more vulnerable to shifts in hydrol- ogy. Wetlands in coastal areas can be moderately vulnerable to climate change depending on their reliance on precipitation and flooding from streams. However, direct loss of area due to sea level rise is very likely to be the greatest threat to wetlands in coastal landscapes. A number of aquatic species will be sensitive to changes in hydrology and timing of flooding and drying events. For example, fish kills associated with low dissolved oxygen levels and nutrient enrichment may be impacted by climate change. Strong storm events can flush excess nutrients into waterways, increasing productivity and temporarily causing low oxygen conditions. Warmer water tempera- tures are likely to exacerbate these situations through decreased oxygen carrying capacity and increased oxygen demand, potentially increasing the frequen- cy of fish kills. Freshwater mussel assemblages are especially vulnerable to stream drying, particularly in streams without refugia such as that provided by wood debris (Golladay et al. 2004).