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Low-level mitigation can assist in restoring redwood forests without affecting stream temperatures

Corvallis, pray. New research from Oregon State University shows that selective logging in river regions to help restore forests can be done without negatively affecting stream water temperature as long as the dilution is not very intense.

Posted in PLoS one, The study led by David Ron, a graduate student in the College of Agricultural Sciences at Ohio State University, is one of the few studies to determine the effects of restorative mitigation on forest flows.

“We don’t know much about what happens with the more subtle changes in shadow and light that come with dilution,” Ron said. “Most research to date has looked at the effects of a net cut with no sidewalk at all, or harvesting outside an untouched buffer zone. Regulatory requirements tend to consider single descriptors of stream temperature – warmer in midsummer, for example – and possibly These descriptors do not do a comprehensive job of explaining thermal effects on environmental processes. “

Riparian areas – lands near streams, lakes, ponds, etc. It has unique soil and plant properties that are highly sensitive to the presence of water. Riparian regions make up less than 1% of the total area of ​​the American West, contrast greatly with the arid highlands of the West and provide a habitat for a host of endangered and endangered species.

In river restoration, conservation managers look at the functional and structural elements of the area – climate, soil, weather patterns, hydrology, plants, wildlife, and socio-economic use patterns – and actively or passively attempt to initiate movement processes that enable natural environmental conditions to return.

Ron explains that riverine forests in the Pacific Northwest have “changed on a large scale” due to earlier wood harvesting practices that continued for much of the 20th century, including cutting trees to the water’s edge.

Leaving a buffer zone of vegetation beside streams is crucial to wildlife, especially salmon and trout. The riverside buffer also provides a wide range of ecosystem services for forests and streams including filtration of sediments, excess nutrients and providing shade to keep water temperatures cool, as well as storing carbon. Additionally, mature trees will eventually be located next to the stream, creating an important habitat for fish.

Ron and colleagues Jason Dunham and Jeremiah Groom examined the effects of river thinning on shade, light, and current temperature in three small watersheds in second-growth redwood forests of northern California. Dunham is an aquatic ecologist with the United States Geological Survey, and has a courtesy appointment in the Department of Fisheries and Wildlife of Ohio State University. Groom, who holds two graduate degrees from Oregon, runs Groom Analytics LLC, a data analysis consulting firm, and is an expert on the effects of forest harvesting on flow temperatures.

Northern California is known for its large and distinctive redwood groves. However, intensive logging has removed most of the old-growth forests from this area and less than 10% of these forests remain.

Forests are interested in whether mitigation can be applied to young forests to help speed up restoration of ancient redwood forests. Most forest restoration efforts to date have focused on highland forests – those in which the soil does not remain saturated for long periods – and have been generally successful; Now attention is turning to young forests in the river regions.

OSU’s research was conducted on private woodland and in nearby Redwood National Park, bringing together land managers with different natural resource management requirements with a common goal of understanding the impacts of mitigation on aquatic ecosystems. The focus of this study was on current temperatures – an important consideration for the sensitive fish and amphibians that inhabit the area’s watersheds.

The large-scale field study enabled scientists to measure conditions before and after experimental dilution treatments. These types of field experiences are rare in carefully protected river forests.

“The strength of these types of field trials is that they can help us directly attribute changes to the dilution treatment itself and remove other factors that often confuse these types of studies,” Ron said. Responses to dilution differed significantly depending on the severity. In watersheds where the mitigation factors were more intense, reductions in shade and increases in light were sufficient to alter the thermal regimes of the stream both locally and downstream. However, as the mitigation factors were less intense, smaller reductions in shade and light led to slight changes in stream temperatures. “

This means, Ron said, that at lower intensity levels, mitigation within river regions in second-growth redwood forests appears as a feasible restoration strategy. This study is an important step towards making robust decisions as to whether, and by how much, dilution can be undertaken without having adverse effects on the flows.

He added that future research could look at palliative treatments with a broader range of severity. Ron also noted that the results were specific to the cold and coastal climate of redwoods and would not necessarily apply to other inland locations.

“We also need to understand the impacts of mitigation in other locations in a range of different contexts,” he said. “Until we know more about the effects of mitigation on current temperatures across a broader range of conditions, they still need to be approached with caution.”

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Oregon State University, the Green Diamond Resource Company, and the Save the Redwoods League supported this research.

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