Soil microbial biomass C and N changes in relation to forest conversion in the northwestern Turkey

Tree species differ in their effect on soil development and nutrient cycling. Conversion of beech coppice to pine plantations can alter soil physical and chemical properties, which in turn may have significant impacts on soil microbial biomass C and N (Cmic, Nmic). The major objective of this study was to evaluate soil quality changes associated with the forest conversion in humid NW Turkey. Results from this study showed that levels of soil organic carbon (Corg), total nitrogen (Nt), moisture, Cmic and Nmic, under beech coppice were consistently higher but levels of pH, CaCO3 and EC were lower compared to pine plantation. Differences between the forest stands in Cmic and Nmic were mainly related to the size of the Corg stores in soil and to tree species. In addition, high level of CaCO3 is likely to reduce pools of soil organic C and possibly even microbial biomass C and N in pine forests. The average Cmic:Nmic ratios were higher in soils under beech coppice than pine plantation, while Cmic:Corg and Nmic:Nt, percentages were similar in both forest types. These results revealed the differences in microbial community structure associated with different tree species and the complex interrelationships between microbial biomass, soil characteristics, litter quantity and quality. Copyright © 2008 John Wiley & Sons, Ltd