Effects of clear‐cutting and burning on characteristics of nitrogen mineralization and microbes in the forest soil of a Pinus massoniana plantation in Southern China

Abstract

The aim of this study was to clarify the effects of clear‐cutting and burning (CCB) on soil fertility in a Pinus massoniana (Masson pine) plantation after CCB in Fujian Province, China. We investigated changes in nitrogen (N) mineralization potential (N0), N mineralization rate constant (k) and the apparent activation energy (Ea) of the soil, with a mathematical analysis using a kinetics model based on the results of in vitro incubation. Changes in the amount of microbial biomass nitrogen (MBN), as well as the number of heterotrophic and nitrite‐oxidizing bacteria, were also investigated. The N0, MBN and the number of fungi and actinomycetes in forest soil was reduced for at least 18 months after CCB. The number of heterotrophic and nitrite‐oxidizing bacteria increased, and k, Ea and N mineralization became greater after 6 months of CCB, compared with the control plots. Because there were few young trees planted, which would have taken up mineralized N in the post‐CCB site, it is probable that a high proportion of the mineralized N that accumulated in the soil may have been lost during the summer rainy season. Therefore, it is suggested that CCB led to a deficiency in available N during short rotations, which resulted in soil degradation.