FY 05/06 | FY 04/05 | FY 03/04 | SPRING 2003 | FALL 2002 | SPRING 2002

FY 04/05


Large changes in evapotranspiration (ET) and water yield are common when trees are planted on lands that previously supported herbaceous vegetation. Globally, one of the best tools to address the effects of afforestation on streamflow is long-term catchment datasets. A previous CGC working group (the “Plantations Group” in AY03/04) synthesized data from catchment studies to assess changes in streamflow with afforestation, and found that annual runoff decreased consistently in afforested catchments, but that the level of decrease varied by original vegetation type and climate, and with plantation age.

In addition to affecting evaporative water losses and runoff locally, afforestation could also affect climate at regional scales and thereby affect precipitation and water use. These regional effects depend on the location, extent, and patchiness of afforestation and operate through changes in albedo, roughness length, and water transport properties from soil to the atmosphere, including leaf area index, stomatal conductance, and rooting depth. These variables influence climate because they help determine the total amount of energy transferred between the vegetation and the atmosphere and the fraction of that energy driving evapotranspiration and warming of the air.

The objectives of this working group are to extend the work of the plantations group on the effects of afforestation on streamflow to the effects on climate, specifically by quantifying the biosphere atmosphere feedbacks of afforestation. The group will run meso-scale model simulations of various afforestation scenarios in the United States using the Ocean-Land-Atmosphere Model (OLAM) – an Earth System Model that in addition to simulating the general circulation of the atmosphere, includes a dynamic terrestrial vegetation model and nested grids and other approaches for increasing the resolution and accuracy of regional simulations. Through the model simulations, the group will estimate potential carbon sequestration rates, explore key biophysical interactions, and quantify feedbacks from large-scale afforestation with climate and precipitation.

The group is composed of an ecologist and an atmospheric scientist:
Robert B. Jackson, Nicholas School of the Environment and Earth Sciences and Department of Biology, Duke University
Roni Avissar, Civil and Environmental Engineering, Duke University

©2005 Center on Global Change
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