Seasonal and long-term patterns in litterfall in a Bornean tropical rainforest

The spatiotemporal characteristics of litterfall reflect important functional processes in a forest ecosystem, yet seasonal and long-term patterns in litterfall and relationship between litterfall and climate seasonality have rarely been examined in the aseasonal Southeast Asian tropics. We monitored monthly litterfall and conducted meteorological measurements over 16 years in a lowland mixed dipterocarp forest in Borneo. The total annual litterfall averaged 7.02 Mg ha ⁻¹ year ⁻¹ and leaf fall contributed 67.9% of total litterfall. Fourier analyses detected a significant annual cycle in monthly leaf fall, although spatial variation was relatively high, and 57.5% of litter traps showed annual cycles at the litter trap level. Rainfall, mean temperature and solar radiation also showed distinct 12-month cycles. Leaf fall was positively correlated with the daily mean air temperature of the same month, and negatively correlated with rainfall in the previous month. Leaf fall gradually increased during the study period. Our results suggest that a seasonal pattern in community-level leaf fall is regulated by the annual cycle of meteorological factors, even in this aseasonal environment, which experiences no dry season. Further monitoring and analyses are required to clarify spatial variation and long-term patterns in litterfall and their mechanisms.