Emmons, Louise H.;Chatelet, Patrick;Cournac, Laurent;Pitman, Nigel C. A.;Vilca V., Vicente;Fernando del Aguila, Luis;Dubois, Marc A.
Seasonal change in leaf area index at three sites along a South American latitudinal gradient
Ecotropica
2006
Journal Article
12
87-102
Los Amigos;Bolivia;French Guiana;light;leaf area index;seasonality
We measured Leaf Area Index (LAI) monthly, by light transmittance, on two 0.5 km to 1 km transects at each of three South American localities spanning a wide gradient in latitude and dry season severity. Our goals were: (1) to evaluate whether we could use a simple methodology to measure seasonal foliar changes in forest cover; (2) to examine the magnitude of seasonal changes within and between sites; and (3) to see how measured LAI patterns correlated with rainfall and litterfall phenology. Each site showed a predictable annual cycle in LAI. The magnitude of seasonal differences was directly related to the severity of the dry season. Median monthly LAI varied roughly inversely with rainfall: at all sites yearly minima occurred in the months of maximum rainfall, and maxima were recorded in the early to mid dry season. Transects with wet-season flooding had lower LAI than did more xeric transects. Litterfall patterns suggest that the major part of within-site seasonal LAI differences are due to deciduousness. This seemingly obvious result is counterbalanced by the many still unresolved interactions between climate, insolation, deciduousness, and seasonal light availability in tropical forest understories.