Post-harvest Carbon and Nitrogen Dynamics in a Loblolly Pine Plantation.

High levels of available nitrogen in forest soils are common after harvest. This spike known as “the assart effect” has been attributed to post-harvest changes in water balance, temperature and plant uptake. Another explanation, recently proposed, is the decrease in microbial N immobilization which might occur if root exudates and other carbon sources are significantly reduced by the harvest. Forest systems accumulate significant amounts of carbon in the forest floor that could partially offset these changes in the carbon supply to soil microbes. A study was conducted in a loblolly pine plantation on the coastal plain of North Carolina to determine the effects of different levels of post-harvest forest floor retention on soil dissolved organic carbon, extractable nitrogen, and microbial biomass. Repeated measures analyses have shown significantly higher levels on all dependent variables for the treatment with highest retention of forest floor during the first year of the study.