Changes in evapotranspiration, transpiration and evaporation across natural and managed landscapes in the Amazon, Cerrado and Pantanal biomes

Land-use and land-cover change (LULCC) can dramatically affect the magnitude, seasonality and main drivers of evaporation (E) and transpiration (T), together as evapotranspiration (ET), with effects on overall ecosystem function, as well as both the hydrological cycle and climate system at multiple scales. Our understanding of tropical ecosystem responses to LULCC and global change processes is still limited, mainly due to a lack of ground-based observations that cover a variety of ecosystems, land-uses and land-covers.

In this study, the authors used a network of nine eddy covariance flux towers installed in natural (forest, savanna, wetland) and managed systems (rainfed and irrigated cropland, pastureland) to explore how LULCC affects ET and its components in the Amazon, Cerrado and Pantanal biomes. At each site, tower-based ET measurements were partitioned into T and E to investigate how these fluxes varied between different land-uses and seasons.

The authors found that ET, T and E decreased significantly during the dry season, except in Amazon forest ecosystems where T rates were maintained throughout the year. In contrast to Amazon forests, Cerrado and Pantanal ecosystems showed stronger stomatal control during the dry season. Cropland and pasture sites had lower ET and T compared to native vegetation in all biomes, but E was greater in Pantanal pasture when compared to Pantanal forest. The T fraction of ET was correlated with LAI and EVI, but relationships were weaker in Amazon forests. Their results highlight the importance of understanding the effects of LULCC on water fluxes in tropical ecosystems, and the implications for climate change mitigation policies and land management.