Seasonal production, allocation and cycling of carbon in two mid-elevation tropical montane forest plots in the Peruvian Andes

Abstract

Background: Tropical montane cloud forests (TMCF) are unique ecosystems with high biodiversity and large carbon reservoirs. To date there have been limited descriptions of the carbon cycle of TMCF.

Aims: We present results on the production, allocation and cycling of carbon for two mid-elevation (1500–1750 m) tropical montane cloud forest plots in San Pedro, Kosñipata Valley, Peru.

Methods: We repeatedly recorded the components of net primary productivity (NPP) using biometric measurements, and autotrophic (R _a) and heterotrophic (R _h) respiration, using gas exchange measurements. From these we estimated gross primary productivity (GPP) and carbon use efficiency (CUE) at the plot level.

Results: The plot at 1500 m was found very productive, with our results comparable with the most productive lowland Amazonian forests. The plot at 1750 m had significantly lower productivity, possibly because of greater cloud immersion. Both plots had similar patterns of NPP allocation, a substantial seasonality in NPP components and little seasonality in R_a .

Conclusions: These two plots lie within the ecotone between lower and upper montane forests, near the level of the cloud base. Climate change is likely to increase elevation of the cloud base, resulting in shifts in forest functioning. Longer-term surveillance of the carbon cycle at these sites would yield valuable insights into the response of TMCFs to a shifting cloud base.

Keywords:

• Andes
• ecophysiology
• elevational gradient
• gross primary productivity
• net primary productivity
• carbon use efficiency
• soil water content
• temperature
• tropical montane forests

Acknowledgements

This work is a product of the RAINFOR and ABERG research consortia, and embedded within the GEM (Global Ecosystems Monitoring) network of research sites. It was funded by grants from the Gordon and Betty Moore Foundation to the Amazon Forest Inventory Work (RAINFOR) and the Andes Biodiversity and Ecosystems Research Group (ABERG), and a grant to YM and PM from the UK Natural Environment Research Council (Grant NE/D014174/1). YM is supported by the Jackson Foundation and the Oxford Martin School. We thank the Cock of the Rock Lodge at San Pedro, and Sr. Demetrio, for logistical support with this work, and INRENA for permits to conduct research in Peru.