Oxygen isotope ratio stratification in a tropical moist forest.

Oxygen isotope ratios were determined in leaf cellulose from two plant species at Barro Colorado (Republic of Panama) in 4 different plots, two of which were undergoing an irrigation treatment during the dry season. There is a gradient in δO values of leaf cellulose from the understory to canopy leaves, reflecting the differences in relative humidity between these two levels of the forest. This gradient is most pronounced in irrigated plots.