As the climate changes, forests are experiencing increasing frequency and severity of disturbances and mismatches between available habitat and climate (Turner 2010). Ongoing and predicted impacts to forests include regeneration failures, shifts in species’ ranges, drought mortality, and increasing severity of disturbances (e.g. bark beetle outbreaks and/or fire). These changes are creating uncertainty in how ecosystem dynamics will function in the future and concerns around sustaining ecosystem goods and services (Seidl & Lexer 2013). Inhibition of conifer regeneration, for example, can lead to ecosystem type conversions and/or long-term changes in stand dynamics, and this concern is magnified in already warm, dry, lower montane systems.
The fact that future conditions will be different from those of the past and the present forces us to step back and rethink the way we manage forests (Millar et al. 2007). The objective of management needs to be in maintaining desired forest characteristics, such as goods and ecological services, when faced with future drought, insects, fire, and warming. Foresters can tackle this challenge head on by building resilience and resistance into the landscape (DeRose &Long 2015) while also planting species better adapted for future (rather than current) conditions (Aitken & Bemmels 2016).
This Sierra Nevada-wide project will utilize progressive, scientifically-supported silvicultural treatments to increase resilience, resistance, and adaptation capacity of Sierra Nevada mixed conifer forests. This work builds on the foundation for management and experimentation laid out by the National Adaptive Silviculture for Climate Change network (Nagel et al. 2017). As the climate changes, foresters will need to be proactive to reduce the risk of these massive carbon (C) sinks becoming C sources and to mitigate predicted impacts to forests, including regeneration failures, drought mortality, and catastrophic wildfire. The foresters leading this collaborative project will tackle this challenge by building resilience and resistance into the landscape while reforesting with seed better adapted for future climate conditions to ensure ongoing C sequestration across the landscape.
The fact that future conditions will be different from those of the past and the present forces us to step back and rethink the way we manage forests (Millar et al. 2007). The objective of management needs to be in maintaining desired forest characteristics, such as goods and ecological services, when faced with future drought, insects, fire, and warming. Foresters can tackle this challenge head on by building resilience and resistance into the landscape (DeRose &Long 2015) while also planting species better adapted for future (rather than current) conditions (Aitken & Bemmels 2016).
This Sierra Nevada-wide project will utilize progressive, scientifically-supported silvicultural treatments to increase resilience, resistance, and adaptation capacity of Sierra Nevada mixed conifer forests. This work builds on the foundation for management and experimentation laid out by the National Adaptive Silviculture for Climate Change network (Nagel et al. 2017). As the climate changes, foresters will need to be proactive to reduce the risk of these massive carbon (C) sinks becoming C sources and to mitigate predicted impacts to forests, including regeneration failures, drought mortality, and catastrophic wildfire. The foresters leading this collaborative project will tackle this challenge by building resilience and resistance into the landscape while reforesting with seed better adapted for future climate conditions to ensure ongoing C sequestration across the landscape.
treatment design & link to adaptive capacity
In Sierra Nevada Adaptive Management Experiment, state and private foresters will implement these concepts on the ground through resilience, resistance, and transition methods of management. These treatments are designed to generate and track long-term changes in forest composition, structure, and function under current and future climate changes. Foresters are dedicated to maintaining these as permanent treatments to facilitate continued C sequestration and other ecosystem services while also tracking effectiveness of these varying intensity treatments. Treatments are meant to represent a basic suite of plausible approaches that managers may feasibly take to address ongoing and novel stresses in forests related to climatic change. Following this design, four treatments will be installed and replicated at the stand level (4 treatments x 3 replicates x 20 acres per replicate = 240 acres); in some areas, treatments will be doubled to allow for a fire or fire surrogate operation to one full replicated set (4 treatments x 3 replicates x 20 acres per replicate x 2 fire or fire surrogate treatment = 480 acres).
Resilience treatments closely mimic forest structure under historic fire conditions and are designed to prepare the forest for disturbance by creating stand conditions that will facilitate recovery of pre-disturbance composition and structure. These treatments mitigate climate change effects and reduce the likelihood of requiring assisted recovering following disturbance or catastrophic climate impact through retention of diverse species and structures. Resilience treatments are comparable to conventional density management in the Sierra Nevada and will create a patchy matrix with high structural heterogeneity and species diversity while retaining locally rare species (e.g. giant sequoia at southern properties).
Resistance treatments are aimed at reducing fuel loading and will prepare the forest to resist a disturbance by creating stand structure that is open, park-like, and forces fire to stay on the ground. These treatments favor large trees that can rapidly respond to release and increase in average diameter. Treatments further change stand structure by removing ladder fuels and increasing spacing among trees. Foresters will retain the largest trees of diverse species, using high leaf area, as opposed to stem form, as a deciding factor in marking (i.e. high leaf area = assumed more resistant to stress).
Transition treatments will work to actively help the forest adapt to changing climate, representing the scenario where resistance and resilience treatments are not effective and the forest cannot recover without intervention. Treatments mimic a disturbance that fundamentally changes the composition and structure of the forest. In this treatment, foresters will use group selection to favor large, live trees but also create large gaps for reforestation. Canopy gaps will cover 10% of transition treatment area, with gaps ranging from 0.25ac to 1ac openings. Transition treatments will create a low stocking matrix with large canopy openings to facilitate common garden trials. A diversity of species and seed sources (provenances) will be selected for reforestation, which will include both local populations and those predicted to be better adapted to current and future climate conditions. These seedlings are the future forest and will need to endure ongoing changes in climate while growing into the canopy.
Controls will maintain untreated areas so that the relative effects of treatments can be assessed. Importantly, controls also represent the plausible alternative that a hands-off approach may in some cases be appropriate given certain climate scenarios. While the context of this study primarily assumes that pro-active management will likely be necessary to sustain forest values into the future, it is also critical to actively test a broad set of approaches- including a hands-off approach.
Flexibility in Treatments: Resilience and resistance treatments use historic natural conditions and treatments as guideposts, acknowledging that composition and structure may depart from these conditions with climate change, as seen with extreme drought mortality in Sierra Nevada. Our targets are in maintaining forest ecosystem function, forests as forests, and the desired services provided by these ecosystems.
Resilience treatments closely mimic forest structure under historic fire conditions and are designed to prepare the forest for disturbance by creating stand conditions that will facilitate recovery of pre-disturbance composition and structure. These treatments mitigate climate change effects and reduce the likelihood of requiring assisted recovering following disturbance or catastrophic climate impact through retention of diverse species and structures. Resilience treatments are comparable to conventional density management in the Sierra Nevada and will create a patchy matrix with high structural heterogeneity and species diversity while retaining locally rare species (e.g. giant sequoia at southern properties).
Resistance treatments are aimed at reducing fuel loading and will prepare the forest to resist a disturbance by creating stand structure that is open, park-like, and forces fire to stay on the ground. These treatments favor large trees that can rapidly respond to release and increase in average diameter. Treatments further change stand structure by removing ladder fuels and increasing spacing among trees. Foresters will retain the largest trees of diverse species, using high leaf area, as opposed to stem form, as a deciding factor in marking (i.e. high leaf area = assumed more resistant to stress).
Transition treatments will work to actively help the forest adapt to changing climate, representing the scenario where resistance and resilience treatments are not effective and the forest cannot recover without intervention. Treatments mimic a disturbance that fundamentally changes the composition and structure of the forest. In this treatment, foresters will use group selection to favor large, live trees but also create large gaps for reforestation. Canopy gaps will cover 10% of transition treatment area, with gaps ranging from 0.25ac to 1ac openings. Transition treatments will create a low stocking matrix with large canopy openings to facilitate common garden trials. A diversity of species and seed sources (provenances) will be selected for reforestation, which will include both local populations and those predicted to be better adapted to current and future climate conditions. These seedlings are the future forest and will need to endure ongoing changes in climate while growing into the canopy.
Controls will maintain untreated areas so that the relative effects of treatments can be assessed. Importantly, controls also represent the plausible alternative that a hands-off approach may in some cases be appropriate given certain climate scenarios. While the context of this study primarily assumes that pro-active management will likely be necessary to sustain forest values into the future, it is also critical to actively test a broad set of approaches- including a hands-off approach.
Flexibility in Treatments: Resilience and resistance treatments use historic natural conditions and treatments as guideposts, acknowledging that composition and structure may depart from these conditions with climate change, as seen with extreme drought mortality in Sierra Nevada. Our targets are in maintaining forest ecosystem function, forests as forests, and the desired services provided by these ecosystems.
literature cited
Aitken, S.N. and Bemmels, J.B., 2016. Time to get moving: assisted gene flow of forest trees. Evolutionary applications. 9(1): 271-290.
DeRose, R.J. and Long, J.N., 2014. Resistance and resilience: A conceptual framework for silviculture. Forest Science. 60(6): 1205-1212.
Millar, C.I., Stephenson, N.L. and Stephens, S.L., 2007. Climate change and forests of the future: managing in the face of uncertainty. Ecological applications. 17(8): 2145-2151.
Nagel, L.M., Palik, B.J., Battaglia, M.A., D'Amato,A.W., Guldin, J.M., Swanston, C.W., Janowiak, M.K., Powers, M.P., Joyce, L.A., Millar, C.I., Peterson, D.L., Ganio, D.L., Kirschbaum, C., and Roskie, M.R. Adaptive Silviculture for climate change: a national experiment in manager-scientist partnerships to apply an adaptation framework. Journal of Forestry. 115(3): 167-178.
Seidl, R. and Lexer, M.J., 2013. Forest management under climatic and social uncertainty: Trade-offs between reducing climate change impacts and fostering adaptive capacity. Journal of Environmental Management. 114: 461-469.
Turner, M.G., 2010. Disturbance and landscape dynamics in a changing world. Ecology, 91(10): 2833-2849.
DeRose, R.J. and Long, J.N., 2014. Resistance and resilience: A conceptual framework for silviculture. Forest Science. 60(6): 1205-1212.
Millar, C.I., Stephenson, N.L. and Stephens, S.L., 2007. Climate change and forests of the future: managing in the face of uncertainty. Ecological applications. 17(8): 2145-2151.
Nagel, L.M., Palik, B.J., Battaglia, M.A., D'Amato,A.W., Guldin, J.M., Swanston, C.W., Janowiak, M.K., Powers, M.P., Joyce, L.A., Millar, C.I., Peterson, D.L., Ganio, D.L., Kirschbaum, C., and Roskie, M.R. Adaptive Silviculture for climate change: a national experiment in manager-scientist partnerships to apply an adaptation framework. Journal of Forestry. 115(3): 167-178.
Seidl, R. and Lexer, M.J., 2013. Forest management under climatic and social uncertainty: Trade-offs between reducing climate change impacts and fostering adaptive capacity. Journal of Environmental Management. 114: 461-469.
Turner, M.G., 2010. Disturbance and landscape dynamics in a changing world. Ecology, 91(10): 2833-2849.
benefits
Project activities will support a suite of ecosystem services across the western Sierra Nevada by creating structural heterogeneity and plant community diversity at the stand, landscape, and regional scales. Structural heterogeneity facilitates wildlife movement via patch diversity and intact corridors while supporting habitat for a wide range of species (e.g. birds of prey and ungulates in large gaps versus black bears in areas with open understory and high plant diversity). On resistance treatments, reductions in basal area and removal of understory fuels will support increased diversity in the under story plant community and associated herbivores. Resilience treatments will create the greatest compositional and structural heterogeneity, supporting a wider range of plant and animal species under both current and future conditions. Transition treatments are aimed at insuring continued forest cover under future conditions, maintaining C sequestration over a 100 year rotation while also providing for continued forest cover for wildlife. The planting of provenances better adapted to future conditions will make these forests more resilient to climate change in the long-term, allowing for perpetuation of ecosystem services. Fuels reduction activities across core properties will have a wide-reaching impact on watersheds and downstream users by reducing sedimentation, maintaining water quality, and providing a continued source of upland water for downstream users. Biomass removed via harvest will be stored long-term in wood products produced by local mills (e.g. Sierra Forest Products in the southern Sierra Nevada).
All actions will lead to immediate short-term C sequestration through release of large-diameter trees and long-term C storage through reforestation efforts and regular maintenance of proposed conditions. Foresters are managing state and private working forests and committed to perpetuating the structural objectives of the project.
All actions will lead to immediate short-term C sequestration through release of large-diameter trees and long-term C storage through reforestation efforts and regular maintenance of proposed conditions. Foresters are managing state and private working forests and committed to perpetuating the structural objectives of the project.
Further Reading
ASCC
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