Severe Drought More Than Offset Post-harvest Hydrological Gains at Caspar Creek in Northern California
Abstract
An experimental selection harvest in a coast redwood forest was completed in the South Fork of the Caspar Creek Experimental Watersheds in northern California in 2019. Prior harvesting results at Caspar Creek showed that harvesting typically increased stream discharge, which was attributed to decreased transpiration and increased throughfall; summer low flows were particularly enhanced relative to pre-harvest conditions. These results suggest a potential benefit of timber harvesting for aquatic species, such as anadromous salmonids, that rely on small streams for summer rearing habitat. Severe drought preceded and followed the 2017-2019 South Fork harvest, creating a special opportunity to assess both the consequences of harvesting at different intensities across the watershed and the impacts of harvesting during a drought period. We investigated the hydrological impacts of harvesting on transpiration, rainfall interception, peak flow response, and summer low flow response. Results from the recent timber harvest also point to increased flow relative to pre-harvest conditions, but in absolute terms, the lowest summer flows in the experiment's 60-year record occurred in 2021. Because of these low summer discharges, relative increases in streamflow caused by the harvest did not result in absolute streamflow increases that may have benefitted aquatic organisms. Other research has shown that temporary benefits of timber harvest on streamflow yields can occur, but these potential gains may not be realized during droughts. These results suggest that land managers and others involved with developing and implementing best management practices should consider additional avenues to promote landscape and habitat resilience during periods of drought.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H52D..02R