LITTERFALL, NUTRIENT FLUX AND NUTRIENT USE EFFICIENCY IN SAKAERAT SEASONAL RAIN FOREST, NORTHEAST THAILAND 2. NUTRIENT FLUX IN LITTER AND NUTRIENT USE EFFICIENCY

摘要

Nutrient contents in litterfall, fresh leaves and in littermass accumulating on the forest floor (Ao - layer) were investigated along with the decomposition quotient and nutrient use efficiency estimated in Sakaerat seasonal rain forest. The studies demonstrated that nutrient contents in litterfall fluctuate seasonally and most nutrients except for potassium (K) in leaf litter are greater in the wet season than in the dry season but those in branch litter are not different during the 2 seasons and also only calcium (Ca) in trash shows a higher content in the wet than in the dry season. Nitrogen (N) in leaf litter positively and significantly related to monthly precipitation but K and magnesium (Mg) show the reverse significant relationship. Nutrient contents in fresh leaves are obviously higher than in leaf litter, making up high nutrient quotient and suggesting the retranslocation of most nutrients before leaf shedding. Nutrient flux in litterfall differs markedly among each litter fraction, being high for N, low for phosphorus (P) and intermediate for K, Ca and Mg. Turnover rates of N, P and Ca are lower and turnover times are longer than those of K and Mg. Nutrient use efficiency within - stand is most efficient for P, suggesting that P is the limiting factor for the productivity of this forest type.