Effects of forest types on soil dissolved organic carbon and nitrogen in surface and deep la-yers in subtropical region, China.

Abstract

Forest types have significant effects on the availability and dynamics of soil dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). By now the impacts of forest types on soil DOC and DON were mainly focused on surface soil (0-10 cm). Based on the comparisons between natural forest, Phyllostachys pubescens, Castanopsis kawakamii and Cunninghamia lanceolata plantations, we investigated the effects of forest types on soil DOC and DON pools in top (0-10 cm) and deep soils (40-60 cm). Cold water, hot water and KCl solutions were used to extract soil DOC and DON from surface and deep soils. Results showed that the effects of forest types on soil DOC, DOC/TOC, DON and soil microbial biomass carbon were only significant in the surface soil. The concentrations of DOC and DON varied with extract methods and hot water extracted the largest amounts of DOC and DON, and cold water the least. Correlations among hot water, KCl and cold water extracted DOC and DON were significant, suggesting that the organic C and N released by these three solutions might be at least partly from similar pools. The concentrations of DOC and DON and DOC/TOC in surface soil under natural forest and P. pubescens were greater than under C. kawakamii and C. lanceolata. It indicated that the concentrations of DOC and DON were greater under the natural forest and P. pubescens than under the C. kawakamii and C. Lanceolata, and more beneficial to improve soil fertility.