Drought

(SOFRA-Moore)

Droughts occur in most forest ecosystems in the South. Occurrence is irregular in forests east of the Mississippi River, occasional across most of the South, and more common in late summer on the Coastal Plain (Hanson and Weltzin 2000). Consequences long-term drought or, flooding are generally proportional to the area affected; during the past few decades, an increasing portion of the United States has experienced either severe drought or flooding (Karl and others 1995b). Drought effects are influenced by soil texture and depth, exposure, species composition, life stage, and the frequency, duration, and severity of drought. The immediate response of forests to drought is to reduce water use and growth. Small plants, including seedlings and saplings, are usually the first to succumb to moderate drought conditions. Deep rooting and stored carbohydrates and nutrients make large trees susceptible only to severe droughts (Dale and others 2001).

Global circulation model predictions of future precipitation patterns are particularly problematic for the South. While one scenario predicts increased precipitation throughout the United States, another predicts significant reductions in both summer and winter precipitation across the South by 2100. To address the potential impacts of drought on forests, the net effect of precipitation changes on soil water must be understood; unfortunately, global scale climate models are not designed to predict this information (Hanson and Weltzin 2000).