Environmental drivers of deadwood dynamics in woodlands and forests

Deadwood dynamics play a key role in many forest ecosystems. Understanding the mechanisms involved in the accumulation and depletion of deadwood can enhance our understanding of fundamental processes such as carbon sequestration and disturbance regimes, allowing better predictions of future changes related to alternative management and climate scenarios. A conceptual framework for deadwood dynamics has been generally accepted but has not been broadly tested with empirical data. We used a large (n = 6191) data set containing measurements of live and standing dead trees, and downed woody material, representing numerous woodland and forest types from throughout the Interior Western USA, to assess relationships between environmental factors and basic elements of forest structure, with particular focus on the various components of deadwood (i.e., fine woody debris, litter, duff and large deadwood, both standing and downed). Environmental gradients emerged as the most influential factors determining structure and deadwood dynamics of these diverse vegetation types. We found that dead components are approximately proportional to the live component and that all of the various components of structure can be ordered as a function of climatic gradients representing temperature and moisture. The postulate that maximum accumulation of biomass is associated with intermediate values of temperature and moisture was only partially supported by our results, indicating that conceptualizations of deadwood dynamics must be considered in the context of the particular disturbance regimes (e.g., fire, insect outbreaks, wind) most commonly associated with particular woodland and forest types. These findings are relevant to a wide range of applications, from ecosystem modeling to development of resource management plans under alternative future climates.