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

Authors: Pisarello, Kathryn; SUN, GE - Us Forest Service (FS); EVANS, JASON - Stetson University; FLETCHER, ROBERT - University Of Florida

Submitted to: Forest Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2022
Publication Date: 10/15/2022
Citation: Pisarello, K., Sun, G., Evans, J.M., Fletcher, R.J. 2022. Potential long term water yield impacts from pine plantation management strategies in the southeastern United States. Forest Ecology and Management. 36:e13872. HTTPS://www.doi.org/10.1111/cobi.13872.
DOI: https://doi.org/10.1111/cobi.13872

Interpretive Summary: Wood-based energy from pine plantations in the southeastern U.S. has increasingly served as a possible sustainable energy substitute for fossil fuels. Trees are harvested from pine plantations in a variety of ways that have associated impacts on how much rainwater runs off the landscape and into local streams, rivers, and reservoirs. In this study, we assessed how volume of rainwater runoff potentially increases under various plantation management practices in pine plantations as well as in watersheds. We found that when plantations are clear-cut, water increased the most compared to other management practices, while only a small amount of thinning (10%) increased water the least, and short rotation (harvesting trees when they reach a certain age) had a variable effect. Importantly, water generally did not increase as much with these land management practices in watersheds,suggesting that land management has smaller impact on water volume across larger areas. These results show that landowners can therefore mitigate some local water shortages or future drought conditions by choosing a management practice that allows for more local accumulation of water runoff.

Technical Abstract: In the Southeastern U.S., changes in global bioenergy consumption have catalyzed the emergence of pine plantations as an important fossil fuel alternative. With increased demand for pine trees as a bioenergy stock, it is critical to assess how forestry management practices may congruently alter landscapes and ecosystem services, like 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, clear-cut, and short rotation on long term mean annual water yield across a 55-year time horizon at both pine plantation (i.e., site) and 8-digit Hydrologic Unit Code watershed scales (watershed area ranging 696 – 7,374 km2) in northern Florida, southern Georgia, and southern Alabama. We compared three site-level evapotranspiration models as well as the watershed-level Water Supply Stress Index water balance model to simulate site and watershed hydrologic responses from pine plantation management scenarios. Both methods showed that 10% thinning had the smallest increase in water yield (<7% for both site and watershed models), while clear-cut conditions imposed the greatest increase (up to 67% in site simulations). Short rotation management caused site-level water yield increases ranging from 10%-50%. 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. The results here show that landowners have some agency over the magnitude of water that is yielded from their plantations, indicating that under drought circumstances, landowners can mitigate local water supply shortages by changing management strategies. Our results can therefore inform expected hydrologic changes under different management scenarios, from which landowners can strategize for optimizing both profit and ecosystem service performance.