Biennial Seasonal Burning and Hardwood Control Effects on the Carbon Sequestration in a Natural Longleaf Pine Ecosystem

Abstract

This study has been superimposed on a study established in 1973 on the Escambia Experimental Forest located in south-central Alabama, USA to examine the effects of different seasons of burn and hardwood control treatments on longleaf pine overstory growth and understory plant succession. The study aims to examine the relationship between various seasons of prescribed fire (winter, spring, summer, and no-burn) and supplemental hardwood control treatments (one-time chemical, periodic mechanical, and untreated check) on carbon sequestration in natural longleaf pine stands. Overstory longleaf pine trees were measured and understory vegetation and litter samples were collected in September 2003 to determine biomass and percent carbon. Soils were sampled at three depths, 0-10, 10-20 and below 20 cm, to determine percent carbon. Analysis of variance was run to test the effects of treatments on carbon content in the understory vegetation and mineral soil. Average DBH and height of longleaf pine trees were greater on no-burn plots. No significant effects of burning and supplemental hardwood treatments on the basal area and biomass of the longleaf trees at stand level were observed. Significantly higher total biomass carbon was documented in the no burn plots, but the total biomass carbon did not differ significantly among burning treatments. The effect of biennial burning on carbon content was primarily limited to the upper 0.1 m of the mineral soil with little change apparent in the depth below 0.1 m. No burn plots had the highest carbon stored in the soil and summer burn plots had the highest carbon content among the burning treatments in 2006. No burn plots had the highest carbon stored in the soil for chemical and control plots of supplemental hardwood treatments in 2007. An increase in soil carbon was observed in the upper 0.1 m layer of mineral soil during one year time period however there was decrease in carbon in depth below 0.1 m. No burn plots had highest amount of carbon stored in the soil in year 2006 and 2007. However, the increase was lowest in these plots with spring burn plots having the highest increase in soil carbon in upper 10 cm layer during this one year time period.