The effect of the red land crab (Gecarcinus lateralis) on leaf litter biomass and nutrient transformation was investigated in a semi-deciduous tropical forest on coastal dunes using access and exclusion plots observed for six months. Crabs were in burrows during drought, but began foraging immediately after rainfall. Crabs accelerated litter disappearance significantly during the wet season at one site located beneath Brosimum alicastrum, but had no effect beneath a nearby Enterolobium cyclocarpum. The difference is tentatively attributed to small leaflet size in the latter species which crabs were unable to handle and consume. At both sites, litter in exdosures had approximately doubled by the end of the ensuing dry season. At the Brosimum site it is attributed to sporadic crab detritivory occurring after dry seasonal rains. At the Enterolobium site it is attributed to preferential retention of litter in the cxclosures during strong dry season winds. The nutrient content of litter exposed to, or protected from, crabs was not significantly different at either site and differences in litter nutrient pools reflected differences in litter biomass. Accelerated nutrient mineralization due to crab detritivory was concentrated early in the wet season before leaching began from the soils, and it is suggested that this altered seasonal pattern of mineralization may reduce the loss of nutrients from the site in percolating water.

We used tree-rings to reconstruct long-term patterns of suppression, release and growth among five sympatric canopy tree species representing the full range of shade tolerance in a seasonal tropical forest in western Thailand. We expected that the frequency and duration of suppression and release events would be positively correlated with shade tolerance. All five species showed evidence of major and moderate growth releases. As expected, Melia azederach, an extreme heliophile, had the fewest releases. However, among the other species the number of major releases was consistent across the range of shade tolerance. The most significant difference among the species was the number of moderate releases recorded. There was a general positive correlation between the number of moderate releases and shade tolerance; however, Chukrasia tabularis, a relatively shade-intolerant species, had an anomalously high number of moderate releases. The study species also showed considerable variation in canopy accession strategies. The least common canopy accession strategy was establishment in the understorey and growth into the canopy in the absence of any gaps. However, with the exception of Melia, all four study species had one or more individuals that successfully reached the canopy using each of the four canopy accession strategies. These results highlight the importance of periodic or episodic bouts of gap formation on canopy tree recruitment and the utility of tree-rings for reconstructing long-term growth patterns in tropical trees.