Effects of a Prescribed Fire on Understory Vegetation, Carbon Pools, and Soil Nutrients in a Longleaf Pine-Slash Pine Forest in Florida

Abstract

We quantified fire-driven loss and post-fire recovery of understory and soil carbon (C) and nutrient pools for one to three years following a single prescribed fire in a naturally regenerated longleaf (Pinus palustris Mill.) and slash pine (Pinus elliottii Engelm. var. elliottii) forest located in north central Florida. Fire immediately reduced total aboveground understory C and nitrogen (N) pools, but these pools recovered to pre-fire levels after three years. Our results also showed that the effect of fire on the understory composition and structure was only short-lived. Prescribed fire significantly reduced total C and N pools in the forest floor (F and H horizons), and this effect persisted for at least one year postfire. Available NH4 , PO43-, Ca2 , Mg2, and K concentrations in the forest floor decreased immediately after fire, but increased in the surface mineral soil (O to 5 cm depth); Ca2 , Mg2 , and K remained elevated for the first year after fire. Fire immediately reduced total ecosystem C and N pools by 40% and 27%, respectively, emitting 3860 g C m-2 and 170 g N m-2 to the atmosphere. The pools recovered to 67% and 76% of pre-fire C and N pools, respectively, after one year. Of the pools measured, C and N recovery in forest floor materials was the slowest, and projections of initial recovery rates suggest that it will take more than six years, the previous fire interval, to reach pre-fire levels. This slow recovery may indicate variation in past rates of forest floor accumulation due to management practices as well as effects of the severity of this or previous fires.