Altitudinal variation in leaf mass per unit area, leaf tissue density and foliar nitrogen and phosphorus content along an Amazon-Andes gradient in Peru

Abstract

Background: Leaf traits are important in determining the capacity for a plant to acquire carbon, but few data are available for montane cloud forests in the Andes. Aims: To investigate the changes in leaf traits along a large altitudinal transect (220-3600 m) from lowland to montane cloud forest in Peru. Methods: We determined leaf mass per area (LMA, g m-2), leaf tissue density (Ld, g cm-3), and foliar nitrogen (N) and phosphorus (P) content, both on a mass (Nm and Pm, %) and area (Na and Pa, g m-2) basis for the most abundant species locally. Results: LMA increased with altitude (62.8-169.4 g m-2), though overall, LMA was lower than in comparable tropical elevation gradients. Nm declined significantly with altitude (2.39-1.25%, P < 0.05), but Nm contents were higher than in comparable studies. The relatively high Nm and low LMA values are consistent with published global leaf trait datasets. No altitudinal trend for Pm was found; rather, our data highlighted the spatial variability in Pm (and Pa) within and among sites at different elevations. Foliar N:P ratios did not show a trend with altitude and did not indicate N limitation except at 3000 m altitude. Conclusions: Though leaf traits showed altitudinal trends similar to other studies, contrary to the general hypothesis, our data suggest that the tropical montane forests presented here are not N limited. Show more