The productivity, metabolism and carbon cycle of two lowland tropical forest plots in south-western Amazonia, Peru

Abstract

Background: The forests of western Amazonia are known to be more dynamic that the better-studied forests of eastern Amazonia, but there has been no comprehensive description of the carbon cycle of a western Amazonian forest.

Aims: We present the carbon budget of two forest plots in Tambopata in south-eastern Peru, western Amazonia. In particular, we present, for the first time, the seasonal variation in the detailed carbon budget of a tropical forest.

Methods: We measured the major components of net primary production (NPP) and total autotrophic respiration over 3–6 years.

Results: The NPP for the two plots was 15.1 ± 0.8 and 14.2 ± 1.0 Mg C ha⁻¹ year⁻¹, the gross primary productivity (GPP) was 35.5 ± 3.6 and 34.5 ± 3.5 Mg C ha⁻¹ year⁻¹, and the carbon use efficiency (CUE) was 0.42 ± 0.05 and 0.41 ± 0.05. NPP and CUE showed a large degree of seasonality.

Conclusions: The two plots were similar in carbon cycling characteristics despite the different soils, the most notable difference being high allocation of NPP to canopy and low allocation to fine roots in the Holocene floodplain plot. The timing of the minima in the wet–dry transition suggests they are driven by phenological rhythms rather than being driven directly by water stress. When compared with results from forests on infertile forests in humid lowland eastern Amazonia, the plots have slightly higher GPP, but similar patterns of CUE and carbon allocation.

Keywords:

• allocation
• GPP
• herbivory
• NPP
• phenology
• seasonality
• soil respiration
• stem respiration
• tropical forests
• western Amazonia

Acknowledgements

This work is a product of the RAINFOR, ABERG and GEM research consortia, and was funded by grants from the Gordon and Betty Moore Foundation to the Amazon Forest Inventory Network (RAINFOR) and the Andes Biodiversity and Ecosystems Research Group (ABERG), and two grants to YM from the UK Natural Environment Research Council (Grants NE/D01025X/1, NE/D014174/1), one to PM (NE/F002149/1), and the NERC AMAZONICA consortium grant. YM is supported by the Jackson Foundation, the Oxford Martin School and a European Research Council Advanced Investigator Grant. We thank the Explorer's Inn (Tambopata) for the hosting of the project and the continuous logistical support provided, and INRENA for permits to work in the Tambopata Reserve. We also thank Eric Cosio, Eliana Esparza and Joana Ricardo for facilitating research permits and equipment shipment in Peru.