Soil moisture dynamics and smoldering combustion limits of pocosin soils in North Carolina, USA

摘要

Smoldering combustion of wetland organic soils in the south-eastern USA is a serious management concern. Previous studies have reported smoldering was sensitive to a wide range of moisture contents, but studies of soil moisture dynamics and changing smoldering combustion potential in wetland communities are limited. Linking soil moisture measurements with estimates of the sustained smoldering limits of organic soils will improve our understanding of changes in ground fire potential over time. Seasonal soil moisture trends were monitored in six North Carolina coastal plain pocosin sites from January 2005 to November 2007. Measurements of the root-mat upper soil horizons were sampled at 2-week intervals while measurements of lower horizon muck (sapric) soil moisture contents and watertable depths were made with automated data logging equipment. The watertable and soil moisture responses were influenced by seasonal and yearly differences in precipitation and hydrologic factors. The maximum estimated probabilities of sustained smoldering were highest in the fall of 2007 and lowest in 2006. Watertable depth was not a consistent predictor of the smoldering combustion potential in the upper organic soil horizons. Maximum Keetch-Byram Drought Index values on all sites were between 500 and 662 during 2005 and 2007 and these values were not consistent with measured soil moistures.