Initial mineralization of organic matter in a forest plantation soil following different logging residue management techniques

Abstract

The influence of tree harvesting and site preparation on inorganic N, net N mineralization and nitrification, microbial biomass and emission of CO2 from soil were evaluated in a field experiment. The study was carried out in a plantation of Pinus radiata D. Three different site preparation techniques were used: a) whole tree harvesting with removal of logging residues and forest floor, b) mechanical incorporation of logging residues and forest floor into the upper 20 cm of the mineral soil, and c) logging residues left on-site. The incorporation of residues into the mineral horizon favoured N immobilization. This effect was accompanied by a higher metabolic activity, as indicated by the higher microbial biomass and CO2 emissions, as well as the higher N contents in decomposing logging residues. In the plot with residues left on site, no changes in soil microbial biomass were observed, although there was a high degree of N immobilization.