Topography is a main factor that exerts a significant control on soil properties. It significantly affects the spatial distribution of soil moisture, temperature, and organic matter. Minor changes in topography can result in large differences in edaphic condition. Moreover, these changes can occur across relatively short distances. Nitrogen cycling within terrestrial ecosystems is a dynamic process that displays substantial variability at both large and small spatial scales. Understanding the effect of topography on N cycling process and soil enzyme activities is crucial. The objectives of this study were to understand: i) landscape scale variability of soil biological indices such as microbial biomass nitrogen, nitrogen mineralization, basal respiration and soil enzyme activities involved in N cycling and ii) Temperature response of nitrogen mineralization and nitrification along a toposequence in Godar Kabk region. Composited soil samples were taken from different slope position. The samples were air-dried and passed through a 2 mm sieve. Results revealed that microbial indices, Q 10 and activation energy affected significantly by slope position. More microbial activities were found in downslope marked by the highest level of soil organic matter and plant biomass comparing with up-and midslopes. Significant correlations were observed between SOC and other measured biological indices in toeslope. In contrast, no strong correlation was observed among the biological indices in other position of slope. The degree of associations among the biological indices may be attributed to the different quality of soil organic matter. Different amount of Q 10 and activation energy along a slope position confirm that organic carbon quality is different and affected by soil erosion and plant residue. The results of this research show the efficiency of biological indices such as Q 10 and activation energy in reflecting the effect of landscape scale variability and management practices.
