Litterfall dynamics in an overcrowded mangrove Kandelia obovata (S., L.) Yong stand over five years

Organic matter fluxes into marginal wetland areas require to be quantified given their support for the detrital components. Following their study for 5 years in a mangrove (Kandelia obovata) stand near the northernmost limit of the species’ distribution in East Asia, leaf and stipule litterfalls exhibited a clear monthly pattern, with maximum values in July and minimum values in February. In this region, mangroves experience a distinct seasonal climate characterised by low temperatures and frequent typhoons. Propagule litterfall was largest in April and May, whereas no propagule litterfall occurred in summer. Kendall’s coefficient of concordance revealed that the monthly trends of litterfall did not significantly differ among years (branch, p < 0.05; other components, p < 0.001). Autocorrelation coefficient analysis demonstrated that all litterfall components exhibited a 1-year cycle, except for branch litterfall, which instead depended on typhoon occurrence. Monthly branch litterfall increased exponentially with increasing monthly maximum wind speed. The monthly total litterfall was significantly affected by mean monthly temperature, mean monthly maximum wind speed, monthly day length and mean monthly solar radiation at a 0.1% significant level, and mean monthly humidity at a 5% significant level. Mean annual total litterfall ranged from 891.1 to 1162.0 g m−2 yr−1, of which leaf litterfall constituted 49.3–67.9%. Higher annual total litterfall was caused by high production of branch litterfall during typhoons. Stipule litterfall (an indicator of new-leaf flush) decreased with increasing levels of flower/fruit and propagule litterfalls and mean annual leaf litterfall per tree decreased with increasing tree density among plots. Annual leaf litterfall per plot was almost constant regardless of tree density and mean leaf longevity was estimated to be 12.04 ± 0.04 month.