Unexpected Decrease in Forest Water Use Efficiency: Legacy Impacts of Acid Deposition
Abstract
Recent studies have highlighted the important role soil biogeochemistry plays in regulating plant water use at the ecosystem scale, specifically that of soil base cations. Calcium in particular serves as a secondary messenger ion in the guard cells, regulating stomatal aperture and thus exerting some control over water use and likely carbon uptake. Soil base cation availability in the Northeastern United States has been largely impacted by the rise and fall of acid deposition since the 1850s and may have an important effect of plant water use efficiency; the ratio of carbon uptake to water loss. We performed stable isotope (13C) analysis on tree cores collected from the Fernow Experimental Forest in controlled and acidified watersheds and on tree cores collected in Shenandoah National Park along a gradient of soil base saturation. Preliminary results from the experimental forest indicate that increased acid deposition caused base cations to leach from the acidified watershed, leading to decreased forest water use efficiency compared to the control. Surprisingly, the water use efficiency of the control watershed also decreased, though to a lesser extent. At the Shenandoah sites, water use efficiency (inferred through δ13C) was observed to be higher at sites with lower base saturation, still decreasing over all. Such observations are at stark contrast with global trends in water use efficiency indicating that not only does current acid deposition impact plant water use, but past deposition regimes may have lasting effects currently unaccounted for.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B33I2593L
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1818 Evapotranspiration;
- HYDROLOGY