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.

Keywords:

• elevation gradient
• foliar nutrients
• leaf mass per area
• leaf traits
• nitrogen
• phosphorus
• tropical montane cloud forests

Acknowledgements

This study is a product of the ABERG programme (http://www.andesconservation.org). We thank the School of Geosciences, University of Edinburgh and the Gordon and Betty Moore Foundation ‘Andes to Amazon’ Programme for their Ph.D. scholarship funding. We also thank the Amazon Conservation Association, Cusco and the Instituto Nacional de Recursos Naturales, Lima for the access to the study sites and their support. Norma Salina Revilla of the University San Antonio Abad, Cusco, Peru, and Dr Miles R. Silman, Wake Forest University, USA, helped our work within ABERG.