Tree mortality estimates and species distribution probabilities in southeastern United States forests

Stresses to trees under a changing climate can lead to changes in forest tree survival, mortality and distribution.  For instance, a study examining the effects of human-induced climate change on forest biodiversity by Hansen and others (2001) predicted a 32% reduction in loblolly–shortleaf pine habitat across the eastern United States.  However, they also predicted an average increase in area of 34% for oak-hickory forests and a 290% increase in oak-pine forests.  Drought is often a leading cause of stress and mortality in forest trees (Allen and others 2010, Choat and others 2012).Drought, whether induced by climate change or other mechanisms, is considered a major inciting factor of forest decline (Leininger 1998, Manion 1981).  For example a drought-induced oak decline event in Arkansas and Missouri that began in 2000 affected up to 120,000 ha in the Ozark National Forest of Arkansas alone (Starkey and others 2004).  A study that examined 1991-2005 data across the southeastern United States found that drought negatively impacted both growth and mortality of pines and mesophytic species, but not oaks (Klos and others 2009).In that regard, three phases of research were addressed through this investigation.  In the first phase, regional relationships of mortality and drought across the Ozark Highlands of Arkansas and Missouri were examined.  In the second phase terrestrial vegetation response to climatological influences across 10 states in the southeastern United States was investigated.  In the third phase probabilities were generated predicting future tree species distribution across the southeastern United States.