The effect of forest degradation intensity on soil function indicators in northern Iran

Abstract

The degradation of forest ecosystems has an important role in global warming through the carbon (C) and nitrogen (N) cycles. The response of soil organic matter fractions and microbial activities to forest degradation has been poorly studied. The purpose of the current research was to evaluate the effect of different intensities (i.e. low, moderate, and high) of forest degradation in northern Iran on the fractions of particulate and dissolved organic matter, microbial and enzyme activities as indicators of soil function. In this research, a total of 15 soil samples (30 × 30 × 10 cm) from each studied forest sites were transferred to the laboratory. Fifty-two soil characteristics of those forest ecosystems were studied by principal component analysis (PCA), with an explanation of more than 55% of the variance by axes 1 and 2. The fractions of soil organic matter (particulate and dissolved organic matter), fertility, microbial activities (microbial respiration and microbial biomass of carbon, nitrogen, and phosphorous), enzyme indices (urease, acid phosphatase, arylsulfatase, invertase, geometric mean of enzyme activities, and Shannon’s diversity index), and stoichiometry of enzyme activity/organic C were enhanced at sites with low degradation intensity. Instead, all studied soil characteristics were suppressed at sites showing high forest degradation. The stoichiometry of enzyme activity/microbial biomass of C were not significantly different among the studied stands. It was concluded that the degradation intensity of natural forests can play a very important role in the soil function of temperate ecosystems.