- Author: Lorena Anderson
Mechanical thinning of overstocked forests, prescribed burning and managed wildfire now being carried out to enhance fire protection of California's forests provide many benefits, or ecosystem services, that people depend on.
In a paper published in Restoration Ecology, researchers at UC Merced, UC ANR and UC Irvine reported that stakeholders perceived fire protection as central to forest restoration, with multiple other ecosystem services also depending on wildfire severity. Researcher Max Eriksson, lead author on the paper, noted that "forest restoration involves multiple fuels-reduction actions that were perceived as benefiting fire protection, with some also offering strong benefits to other ecosystem services such as air quality, wildlife habitat, soil retention and water supply."
The study showed that the total effect of an action such as mechanical thinning of forests aimed at reducing fuels includes not only the direct effect on reducing wildfire severity, but also secondary effects that improving fire protection has on benefits such as providing water and hydroelectricity for agriculture and communities across the state or storing carbon and reducing carbon-dioxide emissions from wildfire to the atmosphere. Fire management is therefore central to human well-being.
Across the western United States, researchers are addressing the huge challenge of transforming forest management from the historical goal of maximum resource extraction (e.g., timber production) to a paradigm built on multiple benefits, or ecosystem services.
The study involved a series of virtual workshops with natural-resource professionals, including forest managers, to understand their perceived effects of management actions on ecosystem services and the interactions of the various services. Eleven ecosystem services and nine currently used management actions were considered.
Safeeq Khan, co-author and UC ANR Cooperative Extension specialist in water and watershed sciences, adds, "Understanding both actual and perceived benefits provided by restoring overstocked forests is crucial to guiding the choice of management actions, public support, policy initiatives and investments by beneficiaries, i.e., monetizing ecosystem services."
UC Merced Professor and co-author Roger Bales points out that "reducing fuel loads is increasingly being recognized as an effective measure to transition our forests across the western United States from a destructive to a beneficial wildfire regime."
Bales adds, "Our research supports the perception that California's wildfire-vulnerable forests should primarily and urgently be restored to conditions that better regulate wildfire severity, and thus provide greater fire protection and other ecosystem-service benefits. Lower-severity wildfire is a natural and beneficial part of these ecosystems."
An important contribution of this study is the breadth of both ecosystem-service benefits and management actions considered. Study collaborator and ecosystem-service expert Benis Egoh, an assistant professor at UC Irvine, points out that, "This research recognized that given the complexity of forest ecosystems across the western United States, the investments required and the management constraints, increasing forest resilience requires a range of actions." She adds, "Accounting for perceived interactions of ecosystem services is key to multi-benefit valuation of restoration investments and to monetizing those benefits in equitable ways."
- Author: Jaquelyn Lugg
Reposted from the UCANR Green Blog
To effectively reduce these adverse effects of harvest, foresters first need to know the precise causes of sediment increases. Historically, researchers investigating the effects of timber harvest on the land have considered two primary drivers: hydrologic changes following timber harvest or fuel reduction that drive sediment transport, and increased sediment supply from ground disturbances and/or mass movements that result from those harvest or fuel reduction activities.
While these causes are tightly linked, little is understood about the relative role each plays in transporting sediment from the watersheds. In other words, which is dominant in increasing sediment delivery and transport: increased streamflow due to greater water availability that can sweep up and transport sediment, or a greater supply of sediment entering the waterway in the first place?
A new analytical approach developed by Safeeq Khan, UC Cooperative Extension specialist in water and watershed sciences at UC Merced, and collaborators now provides valuable insights into this issue, and ways to target effective mitigation strategies.
Published in the Journal of Hydrology last fall, the team's study analyzed long-term (1952-2017) streamflow and sediment data from two adjacent paired watersheds in the H. J. Andrews Experimental Forest in the western Cascades Range of Oregon. One of the watersheds was harvested and replanted in the 1960s, while the second was not disturbed and used as a control.
“The data is from Oregon, but highly relevant for our work in the Sierra Nevada,” said Khan, lead author of the study. “We have tried to quantify the effect of hydrologic changes and increased sediment supply from logging activities on total sediment yield.”
To isolate the relative contributions of streamflow changes and increased sediment supply on sediment transport, Khan and colleagues developed a statistical reconstruction technique to account for the hydrologic changes following harvest.
“This approach allows us to analyze and estimate background sediment production in the treated watershed during the post-treatment period as if the harvest had not occurred, which is remarkable,” said Khan.
The new approach demonstrated that sharp increases in sediment following harvests can be confidently attributed to ground disturbances associated with timber harvest or thinning operations to reduce fuel. Changes in sediment supply overwhelmingly dominate streamflow in terms of contributions to increased sediment in the watershed. Streamflow increases alone led to modest increases in sediment, less than 10%, with the watershed transporting about twice as much total sediment than it would have had the area been left unharvested. This effect diminishes more or less exponentially over time, especially with respect to suspended sediment, as bare areas revegetate, which reduces hillslope sediment supply, and as streamflow returns to pre-treatment levels.
“Once we know the background sediment production, we can easily attribute how much of the increase is due to what mechanisms” said Gordon Grant, a hydrologist with the U.S. Forest Service Pacific Northwest Research Station and co-author on the study.
“Determining that increased sediment in watersheds after harvests is primarily driven by ground disturbance is crucial in targeting mitigation efforts,” explained Khan. “Now, we know that strategies that limit ground disruption – like suspending logs while transporting instead of dragging them, avoiding heavy machinery when and where possible, and mastication and mulching – are likely to be highly effective in reducing sediment yields.”
These changes are most pronounced in the first few years following harvest, but the treated watershed did not return to pre-harvest levels of sediment for two decades, underscoring the long-term effects of harvest on a forest's hydrologic and geomorphic systems.
While clearcutting is no longer practiced on U.S. federal land, it is still the primary timber harvest method used across the globe. Additionally, many other types of forest disturbances such as wildfires, mass tree die-offs, and salvage logging create hydrogeomorphic conditions not too different from clearcutting.
"Our findings provide insights that can help land managers and foresters better target land management and restoration in the future,” said Khan. “We're hopeful that these results will lead to strategies that minimize the long-term impacts and legacies of intense land-use disturbances.”
The full study, titled “Disentangling effects of forest harvest on long-term hydrologic and sediment dynamics, western Cascades, Oregon" is available online in the Journal of Hydrology at https://www.sciencedirect.com/science/article/pii/S0022169419309941?via%3Dihub.
- Author: Pam Kan-Rice
Reposted from the UCANR News
Do you have an opinion on how California wildlands are managed? UC Cooperative Extension specialists Safeeq Khan, Tapan Pathak and Toby O'Geen are conducting a need assessment survey about land management and ecosystem climate solutions.
Khan, Pathak and O'Geen are part of the Innovation Center for Ecosystem Climate Solutions (CECS), a state-funded collaboration between eight California research institutions, including UC ANR, working to develop innovative solutions to managing California's wildlands to reduce negative impacts of drought and climate change. Their goal is to identify land management practices that simultaneously enhance carbon sequestration, reduce wildfire severity, protect watersheds, and increase ecological and community resilience.
Khan would like your help in identifying problems and issues like wildfire and water supply, multiple benefits and beneficiaries of wildlands management, data and information gaps, and major implementation barriers.
To help the research team better understand stakeholder needs and develop data/information solutions for active ecosystem management, please take the survey at https://ucmerced.az1.qualtrics.com/jfe/form/SV_8ptCWlrQBTILyAd. It should take about 30 minutes to complete.
Please feel free to share the survey with your colleagues. To get more involved in the project, contact the team at firstname.lastname@example.org.
The project is funded by the Strategic Growth Council of California.