Effect of altitude and aspect on soil organic carbon and nitrogen stocks in the Himalayan Mawer Forest Range

The soil organic carbon (SOC) and nitrogen (N) stocks in mountainous forests are influenced by the forest diversity, topographic features, and climate change impacts. Role of forest SOC and N stocks in global C cycle has been a subject of great research recently, but the effect of topographic features on their dynamics at the stand level has received less attention especially under temperate conditions. In order to find out how topographic aspect and altitude affect SOC and N budgets, a study was conducted in the Himalayan Mawer Forest Range. We examined SOC and N stocks at two altitude zones (Z1: 1800-2200 masl & Z2: 2200-2500 masl) under North (N) and South (S) aspects at three soil depths (Dl: 0-20 cm, D2: 20-40 cm and D3: 40-60 cm). The SOC stock was found to be decreasing with altitude from 105.9 Mg ha(-1) to 78.3 Mg ha(-1) under N aspect and from 81.6 Mg ha(-1) to 74.0 Mg ha(-1) under S aspect. SOC stock was higher by 16.5% under N aspect as compared to S aspect. The results lead to the conclusion that altitude has a negative effect on SOC stabilization and therefore altitude and aspect effect may be included in SOC stock estimation equations.