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 dr y tropical forest were examined in relation to fine root biomass. Patc hy microsites were richer in mineral N and P. Year-long averages indic ated that NH4+ dominated over NO3- in the nutrient rich patchy microsi tes where fine root biomass, production and turnover were comparativel y greater than in the nutrient-poor adjacent microsites which were dom inated by NO3-. However, during the wet season nitrate was the dominat ing form of mineral-N in all the microsites. N-mineralization was high er in the patchy microsites than in the adjacent microsites. Fine root biomass was positively correlated with the N-mineralization and nitri fication rates in nutrient-rich microsites indicating that fine root d evelopment was facilitated by higher amounts of mineral-N irrespective of the form in which N was prevalent.