Robles, Marcos D. and Marshall, Robert M. and O'Donnell, Frances and Smith, Edward B. and Haney, Jeanmarie A. and Gori, David F. (2014) Effects of climate variability and accelerated forest thinning on watershed-scale runoff in southwestern USA ponderosa pine forests. PLoS ONE, 9 (10). e111092. ISSN 1932-6203
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Abstract
The recent mortality of up to 20% of forests and woodlands in the southwestern United States, along with declining stream flows and projected future water shortages, heightens the need to understand how management practices can enhance forest resilience and functioning under unprecedented scales of drought and wildfire. To address this challenge, a combination of mechanical thinning and fire treatments are planned for 238,000 hectares (588,000 acres) of ponderosa pine (Pinus ponderosa) forests across central Arizona, USA. Mechanical thinning can increase runoff at fine scales, as well as reduce fire risk and tree water stress during drought, but the effects of this practice have not been studied at scales commensurate with recent forest disturbances or under a highly variable climate. Modifying a historical runoff model, we constructed scenarios to estimate increases in runoff from thinning ponderosa pine at the landscape and watershed scales based on driving variables: pace, extent and intensity of forest treatments and variability in winter precipitation. We found that runoff on thinned forests was about 20% greater than unthinned forests, regardless of whether treatments occurred in a drought or pluvial period. The magnitude of this increase is similar to observed declines in snowpack for the region, suggesting that accelerated thinning may lessen runoff losses due to warming effects. Gains in runoff were temporary (six years after treatment) and modest when compared to mean annual runoff from the study watersheds (0–3%). Nonetheless gains observed during drought periods could play a role in augmenting river flows on a seasonal basis, improving conditions for water-dependent natural resources, as well as benefit water supplies for downstream communities. Results of this study and others suggest that accelerated forest thinning at large scales could improve the water balance and resilience of forests and sustain the ecosystem services they provide.
| Item Type: | Article |
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| ID number or DOI: | 10.1371/journal.pone.0111092 |
| Related URLs: | |
| Keywords: | Aquatic environments; Biogeography; Biology and life sciences; climactic changes; Conservation science; Drought; Earth sciences; Ecology; Ecology and environmental sciences; Ecosystem functioning; Ecosystems; Environmental geography; Environmental impacts; environmental management; Fire management; fire severity; forest density; Forest ecology; forests; forest thinning; Fresh water; Freshwater environments; fuels; Geography; Hydrology; increase; Marine and aquatic sciences; native fish; Natural resources; Nature-society interactions; northern Arizona; ponderosa pine; precipitation; Research Article; Restoration ecology; river-basin; Rivers; runoff; Surface water; Systems ecology; Terrestrial ecology; Terrestrial environments; United States; united-states; Water resources; watersheds; Wildfires; Yield |
| Subjects: | S Agriculture > SD Forestry |
| NAU Depositing Author Academic Status: | Faculty/Staff |
| Department/Unit: | College of Engineering, Forestry, and Natural Science > School of Earth Sciences and Environmental Sustainability |
| Date Deposited: | 16 Oct 2015 19:13 |
| URI: | http://openknowledge.nau.edu/id/eprint/1698 |
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