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 (L d, g cm−3), and foliar nitrogen (N) and phosphorus (P) content, both on a mass (N m and P m, %) and area (N a and P a, 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. N m declined significantly with altitude (2.39–1.25 %, P < 0.05), but N m contents were higher than in comparable studies. The relatively high N m and low LMA values are consistent with published global leaf trait datasets. No altitudinal trend for P m was found; rather, our data highlighted the spatial variability in P m (and P a) 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.