Drought, especially persistent drought, may impact forests in direct and indirect ways. Low to moderate drought stress directly reduces plant growth processes at the cellular level, while more severe stress also substantially diminishes photosynthesis (Kareiva and others 1993, Mattson and Haack 1987). Indirectly, forest communities subjected to drought stress may be more susceptible to infestations, and in some cases major outbreaks, of tree-damaging insects (Mattson and Haack 1987). Furthermore, drought impedes decomposition of organic matter and reduces moisture content in woody debris and other potential fire fuels, substantially heightening wildland fire risk (Clark 1989, Keetch and Byram 1968, Schoennagel and others 2004).
Koch, Frank H.; Coulston, John W.; Smith, William D. 2012. Mapping drought conditions using multi-year windows. In: Potter, Kevin M.; Conkling, Barbara L., eds. 2012. Forest health monitoring: 2009 national technical report. Gen. Tech. Rep. SRS-167. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 163-179.