Dynamics of litter production and its quality in relation to climatic factors in a super wet tropical rain forest, West Sumatra, Indonesia

Abstract

In order to clarify the detailed dynamics of litter production and its nutrient characteristics in a super wet tropical rainforest, a study was conducted using twelve litter traps installed in a one ha study plot at PinangPinang, in West Sumatra, Indonesia. The trapped litter was collected monthly in two different years (December 1997 to November 1998 and December 1999 to November 2(00). The annual mean litter production in 1997/98 was 12.2 Mg ha-' and in 199912000 was 11.8 Mg ha-'. The contribution of leaf litter to the totallitterlall was significantly greater (64.8%) than that of the other components i.e., twigs, branches and fruits. The totallitterlall and leaf litter production ranged from 0.16 to 1.98 and from 0.10 to 1.30 Mg ha-'month-', respectively, during the two observation periods. The seasonal pattern of leaf litter production showed a strong positive correlation with mean monthly temperature. Since the mean monthly temperature showed a negative correlation to monthly precipitation, the monthly leaf litter production also showed a negative correlation to the monthly precipitation. The negative correlation between leaf litter production and monthly precipitation was, however, less significant than the positive correlation of leaf litter production to temperature. This finding suggests that, although the mechanism is unknown, leaf litter production is strongly regulated by slight fluctuations in monthly mean temperature, within the range of 25-28 'C in this super wet tropical rainforest. A positive correlation between temperature and litter production was also observed for the total litter and for the other litter components. However, the correlation was less significant for these other litter categories than for leaf litter. Among the litter components (leaf, twigs, branches and fruit), leaf litter showed the highest concentration of nitrogen (N), magnesium (Mg) and sulfur (S). The reproductive structure (fruit) had a significantly higher concentration of P and K than leaf litter, but the fruit's concentration of Ca was lower than those of the other components of the litter. The concentrations of Ca in leaf litter showed a positive correlation to rainfall and a negative correlation to temperature, while the concentration of K in leaf litter showed the reverse trend. The trend of N concentration in leaf litter was somewhat similar to Ca. These trends might be due to the effect of dilution on Ca and N, remobilization on N, and the leaching by rainfall on K.