Shifts in plant respiration and carbon use efficiency at a large‐scale drought experiment in the eastern Amazon

Abstract

Summary• The effects of drought on the Amazon rainforest are potentially large but remain poorly understood. Here, carbon (C) cycling after 5 yr of a large-scale through-fall exclusion (TFE) experiment excluding about 50% of incident rainfall from an eastern Amazon rainforest was compared with a nearby control plot.• Principal C stocks and fluxes were intensively measured in 2005. Additional minor components were either quantified in later site measurements or derived from the available literature.• Total ecosystem respiration (R eco ) and total plant C expenditure (PCE, the sum of net primary productivity (NPP) and autotrophic respiration (R auto )), were elevated on the TFE plot relative to the control. The increase in PCE and R eco was mainly caused by a rise in R auto from foliage and roots. Heterotrophic respiration did not differ substantially between plots. NPP was 2.4 ± 1.4 t C ha )1 yr )1 lower on the TFE than the control. Ecosystem carbon use efficiency, the proportion of PCE invested in NPP, was lower in the TFE plot (0.24 ± 0.04) than in the control (0.32 ± 0.04).• Drought caused by the TFE treatment appeared to drive fundamental shifts in ecosystem C cycling with potentially important consequences for long-term forest C storage.

Predicting the response of the Amazon rainforest to persistent drought conditions under current and future climates: a major challenge for global land surface models

“…In comparison to ecosystem carbon fluxes derived by Metcalfe et al (2010) at Caxiuanã, the model overestimates woody tissue respiration and underestimates respiration of leaves and roots. These errors compensate each other and overall the ISBA CC reasonably matches the yearly heterotrophic and autotrophic respiration fluxes (Fig.…”

Improving the ISBA<sub>CC</sub> land surface model simulation of water and carbon fluxes and stocks over the Amazon forest

“…This result is not realistic. Over the Amazon, the CUE is roughly estimated to be around 0.3 (Chambers et al, 2004;Malhi et al, 2009Malhi et al, , 2011Metcalfe et al, 2010). Therefore, a new parameterization of each respiration term is proposed and described below.…”

Comparison of Carbon-Use Efficiency Among Different Land-Use Patterns of the Temperate Steppe in the Northern China Pastoral Farming Ecotone

“…In our study, we also focused on the environmental factors that influenced ecosystem CUE and the regulation mechanisms. With reference to Metcalfe et al [41] on the influence of drought on CUE, and other research on the influence of microbial biomass, diversity or forest age on CUE, it has generally been indicated that the Re variation correlates with CUE change [34,36,45]. This helps us to focus on revealing the process governing the influence of Re on CUE, and analyzing how the relationship between Re composition changes with CUE variation under different steppe land-use patterns.…”

“…Previous research has already promoted deep understanding of how artificial experimental temperature increases change the ecosystem CUE by influencing soil organic carbon release [24,34,36]. Also, using an experimental approach, Metcalfe et al [41] studied the influence of drought on CUE, which suggested that severe drought restrained the respiration of plants and soil microbial of ecosystems, causing the decrease of Re, and finally decreased the ecosystem CUE. This finding indicated that the CUE decrease of the ecosystem was caused by a water shortage.…”

“…The study was conducted on typical Stipa grandis-dominant temperate steppe (43 • 32 24.06 N, 116 • 33 41.76 E, elevation 1250 m) at Xilinhot, Inner Mongolia, northern China ( Figure 1). Based on local climate data , the average annual temperature is 0.6 • C, and the mean daily temperature is −18.5 • C in the coldest month (January) and 21.5 • C in the warmest month (July).…”