Energy Dynamics and Forest Structure Differences in Intact vs Degraded Amazon Forests

The Science

Forest degradation through fires and logging is common in the Amazon and changes forest structure. However, little is known about degradation’s effects on the way tropical forests transpire water. Researchers assessed seasonal water stress and its relationship with forest structure across intact and disturbed forests in the Amazon using high-resolution remote sensing of forest structure from spaceborne lidar (Global Ecosystem Dynamics Investigation; GEDI) and evapotranspiration (ET) derived from Landsat. They found that forest structure exerts a stronger control on ET in more disturbed/drier forests than in intact or lightly disturbed forests.

The Impact

New satellite data and products allow measurement of forest structure and ET across large areas. With these data, researchers can better understand how human activities in tropical forests change the earth’s water and energy cycles. The study found that forest structure influences ET more than climate. In addition, the team found that forest degradation may make Amazon forests limited by water; intact forests in the Amazon are normally limited by energy, not water. These findings have important implications for the global water balance and rainfall patterns.

Summary

Deforestation, timber extraction, and forest fires disturb large areas in the Amazon region. These disturbances alter how forests function. Previous work focused on how deforestation affects the water and energy cycles. This research used satellite-based data to understand how degradation changes water and energy fluxes. The research team analyzed ET, land surface temperature, and forest structure (tree cover and forest height) data over a region in the southern Amazon. This region has a mix of deforested, degraded, and intact forests, allowing researchers to study the effects of forest structure on water and energy cycles.

The research team found that water stress conditions start early into the dry in croplands and pastures. They also found that second-growth and burned forests experience stronger water stress than logged and intact forests. Moreover, they found that forest structure is moderately related to ET and temperature, but only in the most disturbed forests. Results show the importance of intact forests in maintaining water balance in the Amazon region and suggest that disturbed forests may be less able to cope with the changing climate.

Principal Investigator

Ekena Rangel Pinagé
Oregon State University
[email protected]

Co-Principal Investigator

Marcos Longo
Lawrence Berkeley National Laboratory
[email protected]

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This research was supported by the Next-Generation Ecosystem Experiments Tropics, which is funded by the U.S. Department of Energy’s Biological and Environmental Research program. Support was also received from the Australian Government Research Training Program Scholarship, the U.S. Department of Agriculture Forest Service Pacific Northwest Research Station and International Programs, and the NASA Postdoctoral Program, which is administered by the Universities Space Research Association under contract with NASA. The research carried out at the California Institute of Technology’s Jet Propulsion Laboratory was under a contract with NASA.

References