Litterfall dynamics in mangrove Kandelia obovata (S., L.) Yong stands on Okinawa Island, Japan, over four years

The objective of this study was to quantify litterfall dynamics in a belt-transect (5 m x 125 m) of Kandelia obovata (S., L.) Yong stands over four years. The leaf litterfall showed a seasonal pattern: the main peak occurred in July and the lesser one was in February. The stipule litterfall was the highest in July and the lowest in February. The highest propagule litterfall was in April and May, while there was no propagule litterfall in summer. The seasonal trends of litterfalls were not different among the years. Branch litterfall showed an exponential relation with the monthly maximum wind speed. The autocorrelation coefficient showed a clear one year cycle for all litterfalls, except for the branch litterfall. The stipule litterfall, i.e. an indicator of new leaf flush, positively correlated to the leaf litterfall, which suggests that the leaf litterfall followed the production of new leaves. The stipule litterfall decreased up to a minimum value with an increase of flower-propagule litterfall. This result indicates that the new leaf flush can decrease with increasing flower and propagule production, but there exists a lower limit of the new leaf flush. Mean annual total litterfalls of the 1(st) year, the 2(nd) year, the 3(rd) year and the 4(th) year were respectively estimated as 891.1 +/- 0.3, 1037.3 +/- 0.5, 1162.0 +/- 0.9 and 902.4 +/- 0.9 (SE) g m(-2) yr(-1), of which the leaf litterfall comprised 67.9 (1(st) year), 57.3 (2(nd) year), 49.3 (3(rd) year) and 60.4% (4(th) year) respectively.