High sensitivity of a tropical rainforest to water variability: Evidence from 10 years of inventory and eddy flux data

The response of tropical rainforest to environmental perturbation is of critical importance given their potential to mitigate climate change. Nevertheless, it was not well addressed to date. Therefore, related hypotheses, i.e., CO2 fertilization-related accelerating growth hypothesis (AGH) and remote sensing-based drought resilience hypothesis (DRH), were necessarily to be testified. Here these hypotheses were tested through 10 years of annual inventory records and half-hourly eddy flux measurements from a tropical rainforest. We show that the studied forest is highly sensitive to water variability, with low canopy photosynthesis, slow stand growth, and high mortality rate in dry years, especially in the severe drought. Ecosystem respiration was not correlated with net water balance within years, but significant correlations were found between these parameters with a time lag of 10-15 months. A boom of photosynthesis in 1 year post drought was most probably a result of nutrient pulse-related drought. In general, neither AGH nor DRH was supported by the study. Given predictions that tropical areas will experience increasingly dry conditions in the future, much attention should be paid to the potential fate of carbon sink in tropical rainforests