US EPA

3280949 

Journal Article 

The Effects of Drought on Amazonian Rain Forests 

Meir, P; Brando, PM; Nepstad, D; Vasconcelos, S; Costa, ACL; Davidson, E; Almeida, S; Fisher, RA; Sotta, ED; Zarin, D; Cardinot, G 

2009 

Yes 

Geophysical Monographs Book Series
ISSN: 0065-8448 

Geophysical Monograph Series 

186 

429-449 

10.1029/2009GM000882 

WOS:000289443400026 

The functioning of Amazonian rain forest ecosystems during drought has become a scientific focal point because of associated risks to forest integrity and climate. We review current understanding of drought impacts on Amazon rain forests by summarising the results from two throughfall exclusion (TFE) experiments in old-growth rain forests at Caxiuana and Tapajos National Forest Reserves, and an irrigation experiment in secondary forest, near Castanhal, Brazil. Soil physical properties strongly influenced drought impacts at each site. Over years 1 to 3 of soil moisture reduction, leaf area index declined by 20-30% at the TFE sites. Leaf physiology and tree mortality results suggested some species-based differences in drought resistance. Mortality was initially resistant to drought but increased after 3 years at Tapajos to 9%, followed by a decline. Transpiration and gross primary production were reduced under TFE at Caxiuana by 30-40% and 12-13%, respectively, and the maximum fire risk at Tapajos increased from 0.27 to 0.47. Drought reduced soil CO2 emissions by more than 20% at Caxiuana and Castanhal but not at Tapajos, where N2O and CH4 emissions declined. Overall, the results indicate short-term resistance to drought with reduced productivity, but that increased mortality is likely under substantial, multiyear, reductions in rainfall. These data sets from field-scale experimental manipulations uniquely complement existing observations from Amazonia and will become increasingly powerful if the experiments are extended. Estimating the long-term (decadal-scale) impacts of continued drought on Amazonian forests will also require integrated models to couple changes in vegetation, climate, land management, and fire risk.