Abstract
Exchange of biomass between the ecosystem and the atmosphere plays an important role in regional and global carbon cycles that have a major impact on biodiversity. This study evaluated the effect of reduction in rainfall on the aboveground biomass in an Amazonian rainforest. Data for this study were obtained from the “Long-term drought impact on water and carbon dioxide fluxes in Amazonian Tropical Rainforest Experiment (ESECAFLOR)” which was a subproject of Large Scale Biosphere Atmosphere Experiment in Amazon forest (LBA), carried out in terra firma rainforest in Caxiuana National Forest, Para, Brazil. The experimental design entailed two experimental sites each with one hectare of natural forest: control TFE (a simulated soil drought or ‘throughfall exclusion’ experiment) under normal conditions of climate and treatment TFE with rainfall exclusion of about 50%. The tree growth parameters employed in the study were based on monthly data from the experimental period from January 2005 to May 2009. Results indicated that a decrease in rainfall significantly affected the tree growth parameters, resulting in a decrease of biomass (21.1 t ha-1 year-1) and basal area (1.04 m2 ha-1 year-1). The Amazonian rainforest may become increasingly vulnerable to higher background tree mortality rates in response to drought events, such as El Nino.
Highlights
Recent analyses suggest that carbon dynamics of the Amazonian tropical forests vary interannually in response to rainfall and temperature anomalies [1]
There was an appreciable difference in the aboveground biomass between control and treatment plots for all tree diameter classes throughout the study period, as shown in Figure 2, because rainfall was artificially excluded to simulate a severe drought which is associated with the El-Niño years
The aboveground biomass on control throughfall” exclusion (TFE) did not practically vary during the experimental period, except for the smallest class with an increase of only 2.7 t ha-1, while the other classes showed a little sign of decreasing trend
Summary
Recent analyses suggest that carbon dynamics of the Amazonian tropical forests vary interannually in response to rainfall and temperature anomalies [1]. Using simulated soil-moisture droughts or TFE experiments (throughfall exclusion experiment), effects of severe droughts as a consequence of climate change, have been investigated in the eastern Amazonian rainforest. These investigations have analyzed tropical forests which have been subjected to increasingly severe drought episodes through the El-Niño/Southern Oscillation (ENSO). Using the same design as for the Caxiuanã forest, Fisher et al [1] analyzed the response of an eastern Amazonian rainforest to drought stress using data from the TFE experiments Both investigations were carried out as part of LBA, using two 100 m x100 m plots, one control plot and one treatment ‘TFE’ plot
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