Seasonal and spatial dynamics of plant-available N and P pools and N-mineralization in relation to fine roots in a dry tropical forest habitat

Seasonal dynamics of mineral N (NH4+ and NO3−), available P (NaHCO3Pi) and N-mineralization rates in patchy and adjacent microsites of a dry tropical forest were examined in relation to fine root biomass. Patchy microsites were richer in mineral N and P. Year-long averages indicated that NH4+ dominated over NO3− in the nutrient rich patchy microsites where fine root biomass, production and turnover were comparatively greater than in the nutrient-poor adjacent microsites which were dominated by NO3−. However, during the wet season nitrate was the dominating form of mineral-N in all the microsites. N-mineralization was higher in the patchy microsites than in the adjacent microsites. Fine root biomass was positively correlated with the N-mineralization and nitrification rates in nutrient-rich microsites indicating that fine root development was facilitated by higher amounts of mineral-N irrespective of the form in which N was prevalent.