Potential long term water yield impacts from pine plantation management strategies in the southeastern United States

Changes in global bioenergy consumption have catalyzed the emergence of forest plantations as an important energy alternative. In the southeastern United States, land cover changes caused by increasing demands for pine trees as a bioenergy feedstock incite associated impacts on local ecosystem services (e.g., water yield). However, water yield impacts from pine plantation management strategies, such as thinning and short rotation, have yet to be simultaneously examined on multiple spatial scales. Here, we modeled the effects of thinning and clear-cut conditions on long term mean annual water yield across a 55-year time horizon at the watershed scale (watershed area ranging 696 - 7,374 km(2)) in northern Florida, southern Georgia, and southern Alabama. Additionally, we assessed the long term water yield effects of thinning, clear-cut, and short-rotation management at the pine plantation (i.e., plot) scale. We compared three plot-level evapotranspiration models as well as the watershed-level Water Supply Stress Index water balance model to simulate plot and watershed hydrologic responses from pine plantation management scenarios. Both methods showed that 10% thinning had the smallest increase in water yield (<6%), while clear-cut conditions imposed the greatest increase (up to 51% for plot scale and up to 25% for watershed scale simulations). Short-rotation management caused plot-level water yield increases ranging from 3% to 24%. Overall, greater water yield effects were seen in site simulations, rather than in watersheds, reinforcing the importance of scale when assessing water budget impacts given land cover changes. These results suggest that landowners have agency over the magnitude of water that is yielded from their plantations and that local water supply shortages can be mitigated by changing forestry biomass management strategies. The opportunity to supplement local water availability is especially valuable within the context of changing climate cycles that may bring about drier local conditions. The multi-scale approach presented here can support efforts from landowners and water managers to optimize profit as well as ecosystem service provision.