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Oct 2020

Landscape restoration minimizes tree growth vulnerability to 21st century drought in a dry forest

John. B. Bradford, Caitlin A. Andrews, Marcos D. Robles, Lisa A. McCauley, Travis J. Woolley, Robert M. Marshall
Arizona
Climate Change
Forest
USFS, USGS
Abstract

With hotter temperatures and less precipitation projected in the future, reducing tree density is a possible strategy to minimize the impacts of drought on forest growth. Many forest restoration programs are focused reducing tree density to minimize wildfire risks, but it is unknown how these efforts will impact drought vulnerability. In this study, we looked at how the Four Forest Restoration Initiative (4FRI) would alter landscape-scale patterns of forest growth and drought vulnerability throughout the 21st century. We found that hotter and drier conditions in the future could reduce tree growth, but the severity of drought and the magnitude of future growth declines was lessened by the thinning treatments. Compared to historical conditions, proportional tree growth by 2050 declines by ~40% if thinning continues at the status quo pace.  By comparison, proportional growth declines by only 20% if the 4FRI thinning treatments are fully implemented, and < 10% if stands are thinned even more intensively. These results indicate that forest restoration projects designed for other objectives can also have substantial benefits for minimizing future drought vulnerability in dry forests and provide additional incentive to accelerate the pace of restoration.

Available here

 
(ALL RIGHTS GRANTED TNC) View of Escudilla Mountain. Fall colors heighten the natural beauty of forest and meadow in the White Mountains, one of Arizona’s last wide-open spaces and where TNC works to protect the headwaters of three major Arizona rivers: the Salt, Gila, and Little Colorado and their greenbelts – riparian habitats critical for wildlife and water quality – as well as restore healthy forests within the largest ponderosa pine community in the world, save rare and unique wildlife and plant species, and control non-native, invasive species, such as crayfish, Arizona. © Betsy D. Warner/TNC
Aerial view of the Parks West restoration site overseen by TNC. Taken March 16, 2020.
Conservancy staffers, Dale Turner and Amanda Rebore, helping to map the Sabn Pedro River in Arizona. They use a GPS unit to denote the end of the water flow on the LowerSan Pedro River. They hiked through the Conservancy’s San Pedro Preserve.

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