Seasonal dynamics of soil Inorganic N and Nmineralization in sub-tropical Sal forest in Central Himalaya, India

Abstract

Seasonal variation in inorganic N-pool and Net N-mineralization rate was investigated in relation to site characteristics in sub-tropical Sal forest in Central Himalaya, India. Two sites, viz. Fatehpur (FP) located at a latitude of 29°19'23.69''N and longitude of 79°18'05.34''E at 430 m asl and Ranibagh (RB) at a latitude of 29°17'10.03''N and longitude of 79°32'49.19''E at 580m asl were established. Ammonification, nitrification and Nmineralization rates were significantly (p<0.05) affected by site, season, soil depth and their interactions. Total inorganic -N and N-mineralization rates were significantly higher in FP site as compared to RB site. Higher mineralization rates were reported during the summer (7.30±0.17 μg g-1 month-1 and 6.17±0.27 μg g-1 month-1 in FP and RB site, respectively) and lowest rates during the winter season (2.10±0.17 μg g-1 month-1 ) in FP and (1.78±0.18 μg g-1 month-1 in RB site). The variability in mineralization rates may be due to the ecological differences among the sites. Seasons and soil nitrogen content showed positive correlation with Nmineralization rates while site, clay content and C/N ratio showed negative correlation. The soil Nmineralization affects the N release and availability of inorganic-N for supporting the plant growth, thus regulates the N- cycling in forest ecosystems.