Drought has significant direct and indirect impacts on forest health. In direct terms, low-to-moderate drought stress limits plant growth, while more severe drought stress reduces both growth and photosynthetic activity (Kareiva and others 1993, Mattson and Haack 1987). Indirectly, drought stress in forest communities may predispose trees to insect infestation, in some cases leading to major outbreaks (Mattson and Haack 1987). In addition, drought slows organic matter decomposition and reduces the moisture content of woody debris and other fuels, greatly increasing fire risk in wildland areas (Clark 1989, Keetch and Byram 1968, Schoennagel and others 2004).
Koch, Frank H.; Coulston, John W.; Smith, William D. 2012. High-Resolution Mapping of Drought Conditions. In: Potter, Kevin M.; Conkling, Barbara L. 2012. Forest health monitoring: 2008 national technical report. General Technical Report SRS-158. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. Pages 45-62.