Responses of Heterotrophic and Autotrophic Soil Respiration to Simulated Drought in Managed Southern Pine Forests.

Since the 1950’s – 60’s intensively managed pine plantations in the southeast have become net carbon sinks. However, climate change predictions for some areas the southeast could see up to a 30% decrease in overall precipitation which may lead to declines in productivity and as a result may change the net carbon balance of forests in the southeast. In this study we examine the effects of fertilization and drought on net ecosystem production (NEP), in a fully replicated, 2x2 factorial design. Seasonal variations in soil respiration are measured in order to find a heterotrophic respiration coefficient that will lead to the ability to quantify NEP in southeastern loblolly pine plantations. To accomplish this, root exclusion collars have been installed in order to drive autotrophic respiration to zero with the remaining respiration rate being heterotrophic respiration. Collecting these data over a growing season and at various levels of fetility and throughfall exclusion will allow us to predict rates of heterotrophic respiration For use in NEP modeling efforts.