Adaptive management of a riparian zone in the lower Klamath River basin, northern California: the effects of riparian harvest on canopy closure, water temperatures and baseflow
Graduation Date
2016
Document Type
Thesis
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Natural Resources: Forestry, Watershed, and Wildland Sciences, 2016
Committee Chair Name
Andrew Stubblefield
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Evapotranspiration, Riparian buffers, Water temperature, Klamath River basin, California forest practice, Alder, Redwood, Adaptive resource management, Humboldt State University -- Theses -- Natural Resources, Thinning
Abstract
Riparian timber harvest buffer policy in California has grown increasingly complex since its creation in 1972, seeking to prevent cumulative watershed effects from logging on private lands. Originally implemented to mitigate sediment inputs into watercourses following clearcut logging, trees in these riparian buffers have continued to grow since the 1970's, shading streams and affecting water temperature throughout northern California. Current California forest practice allows for some riparian harvest, but limits flexibility of individual treatments, instead relying on uniform buffers to protect watercourses. The federal government allows more flexible site-specific management with an appropriate habitat conservation plan and justification. This thesis contains two components: the first is a discussion of the development of current riparian policy, which uses interviews and analysis of documents to examine the history of the policy governing riparian zones. The history, evolution, and expansion of California forest policy and the interaction between federal and state forest law provides context for the case study contained within the second portion of this thesis, measurement of stream warming and discharge changes as a response to riparian thinning.Thinning along a 330-meter Class I stream reach in winter 2014/2015 opened the second-growth hardwood canopy surrounding the reach, and allowed light in to the stream surface, which spurs primary productivity. Measured discharge was higher in the second year, post thinning, despite lower annual precipitation and lower spring precipitation. Reduced evapotranspiration from fewer trees increased summer streamflow the year post-treatment, a desirable result for salmon and other aquatic vertebrates, given the severe drought in California. Results indicate that water temperature maxima increased in the reach by 1.68°C, and diurnal variation increased due to this higher maxima, combined with lower minima from the loss of the insulative canopy layer. Results suggest that spatially explicit riparian thinning and adaptive riparian management can increase thermal heterogeneity, and may be a potential solution for salmon habitat restoration when instituted carefully, in a spatially limited manner within the cool coastal anadromy zone on Northern California's coast.
Recommended Citation
Wick, Alexander R., "Adaptive management of a riparian zone in the lower Klamath River basin, northern California: the effects of riparian harvest on canopy closure, water temperatures and baseflow" (2016). Cal Poly Humboldt theses and projects. 2051.
https://digitalcommons.humboldt.edu/etd/2051
https://scholarworks.calstate.edu/concern/theses/6q182n52w