Nitrogen and Phosphorus Content in Forest Floor Litter is Elevated in a Tropical Landscape Recovering from Deforestation
Fallen leaf chemistry provides a window into the various and often complex factors affecting the availability of nutrients to trees. Forest Service scientists and collaborators analyzed 11 elements in forest floor (fallen) leaves and additional litter components from 143 Forest Inventory and Analysis (FIA) plots systematically located across Puerto Rico, a tropical landscape recovering from large-scale forest clearing. Across several scales, fallen leaf nitrogen concentration was positively related to the basal area of putatively nitrogen fixing tree legumes, which were concentrated in lower topographic positions, providing for the first time a biological explanation for the high nitrogen concentrations of fallen leaves in these landscape positions that can be linked to land-use patterns. Phosphorus concentrations in fallen leaves by forest assemblages also were correlated with the basal area of nitrogen fixing legumes and decreased with mean age of assemblage, as did fallen leaf nitrogen concentrations. The findings suggest that nitrogen and phosphorus availability may currently be greater on the island than before deforestation when older and presumably native forests dominated the landscape, because the island forests are now dominated by younger and often novel forests.
Forest Service Partners