43. Seeing the Forest for the Trees

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Seeing the Forest for the Trees: Conservation in the Face of Timber Harvest and Fuel Management

Saturday, October 22 at 1:00-2:40 pm, Pine Room

Session Description: What would California’s forests look like absent 200 years of aggressive timber harvest and 100 years of fire suppression? How do we restore and maintain a more natural forest structure and appropriate fire regime? What are the risks if we don’t act?  This session will look at the role of weather and vegetation in driving fire behavior in different regions of California, historic conditions and the influence of indigenous management in the fire-adapted forests of northern California, as well as current forest conditions and trends, and a discussion of actions (including timber harvest) and key issues to consider in restoring our frequent-fire forests.

Session Chair: Paul Mason (Pacific Forest Trust, Sacramento, CA)

43.1    Land management explains major trends in forest structure and composition over the last millennium in California’s Klamath Mountains

Dr. Clarke A. Knight (U.S. Geological Survey, Menlo Park, CA, USA), Lysanna Anderson (U.S. Geological Survey, Menlo Park, CA, USA), M. Jane Bunting (University of Hull, Hull, UK), Marie Champagne (U.S. Geological Survey, Menlo Park, CA, USA), Rosie Clayburn (The Yurok Tribe’s Cultural Resources Manager, Klamath, CA, USA), Jeffrey Crawford (USDA Forest Service, Bend, OR, USA), Anna Klimaszewski-Patterson (California State University, Sacramento, CA, USA), Eric Knapp (USDA Forest Service, Redding, CA, USA), Frank Lake (USDA Forest Service, Arcata, CA, USA), Scott Mensing (University of Nevada Reno, Reno, NV, USA), David Wahl (U.S. Geological Survey, Menlo Park, CA, USA), James Wanket (California State University, Sacramento, CA, USA), Alex Watts-Tobin (Karuk Tribe’s Department of Natural Resources, Orleans, CA, USA), Matthew Potts (University of California, Berkeley, Berkeley, CA, USA), John Battles (University of California, Berkeley, Berkeley, CA, USA

For millennia, forest ecosystems in California have been shaped by fire from both natural processes and Indigenous land management, but the notion of climatic variation as a primary controller of the pre-colonial landscape remains pervasive. Understanding the relative influence of climate and Indigenous burning on the fire regime is key because contemporary forest policy and management are informed by historical baselines. This need is particularly acute in California where 20th-century fire suppression, coupled with a warming climate, has caused forest densification and increasingly large wildfires. These wildfires threaten forest ecosystem integrity and management of the forests as part of climate mitigation efforts. We examine climatic versus anthropogenic influences on forest conditions over 3 millennia in the western Klamath Mountains—the ancestral territories of the Karuk and Yurok Tribes—by combining Indigenous knowledge with paleoenvironmental data. Trends in biomass reconstructions and the paleo–fire record matched expectations from Karuk/Yurok-based knowledge about cultural burning, as well as aligned with independent 1880 public land survey records that document vegetation composition and structure. A fire regime consisting of tribal burning practices and lightning were associated with long-term stability of forest biomass. Before Euro-American colonization, the long-term median forest biomass was between 104 and 128 Mg/ha, compared to values over 250 Mg/ha today. Indigenous depopulation after AD 1800, coupled with 20th-century fire suppression, likely allowed biomass to increase, culminating in the current landscape: a closed Douglas fir–dominant forest unlike any seen in the preceding 3,000 years. These findings are consistent with pre-contact forest conditions being influenced by Indigenous land management and suggest large-scale interventions could be needed to return to historic forest biomass levels.

43.2    What is forest resilience and how do we measure it in forest restoration?

Ryan Tompkins (University of California Cooperative Extension, Quincy, CA)

With the increasing frequency and severity of altered disturbance regimes in dry, western U.S. forests, treatments promoting resilience have become a management objective but have been difficult to define or operationalize. Many reconstruction studies, such as North et al (2022), of these forests when they had active fire regimes have documented very low tree densities of large trees before the onset of fire suppression. Building on ecological theory and recent studies, we suggest that this historic forest structure promoted resilience by minimizing competition which in turn supported vigorous tree growth and sustained large trees – the “backbone” of these forested ecosystems. To assess these historic conditions for management practices, we calculated a widely-used measure of competition, relative stand density index (SDI), for two extensive historical datasets and compared those to contemporary forest conditions. Between 1911 and 2011, tree densities on average increased by six to seven fold while average tree size was reduced by 50%. Relative SDI for historical forests was 23–28% of maximum, in the ranges considered ‘free of’ to ‘low’ competition. In contrast, most (82–95%) contemporary stands were in the range of ‘full competition’ or ‘imminent mortality’. Historical relative SDI values suggest that treatments for restoring forest resilience may need to be much more intensive then the current focus on fuels reduction. With the contemporary increase in compounding stresses such as drought, bark beetles, and high-severity wildfire, resilience in frequent-fire forests may hinge on creating stands with significantly lower densities and minimal competition. Current management practices often prescribe conditions that maintain full competition to guide development of desired conditions. Creating stands largely free of competition would require a fundamental rethinking of how frequent-fire forests can be managed for resilience.

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