Approach
EASTERN: Species are vulnerable to stressors at different stages in their life cycle. Even-aged stands are often more vulnerable to insect pests and diseases, many of which are likely to increase in range and severity as a result of climate change. In uneven-aged systems, a smaller proportion of the population may be exposed to a particular threat at any one time, which can increase the resistance or resilience of a stand to a wider range of disturbances. Maintaining a mix of ages, sizes, or canopy positions will help buffer vulnerability to stressors of any single age class, as well as increase structural diversity within stands or across a landscape.
WESTERN: Any given species will have unique vulnerabilities to different stressors which may differ at different stages in their life cycle. Even-aged forested stands are often more vulnerable to insects and diseases, many of which are likely to increase in range and severity as a result of climate change. In uneven-aged systems, more typical of most forests in California, a smaller proportion of the population may be exposed to a particular threat at any one time, which can increase the resistance or resilience of a stand to a wider range of disturbances. Forest stands with a combination of widely scattered individuals, clusters of mixed age trees, and open spaces may increase forest resilience. Maintaining a mix of species, ages, sizes, or canopy positions will help buffer vulnerability to stressors of any single age class, as well as increase structural diversity within stands or across a landscape.
Tactics
- Emulating aspects of disturbances through forest management techniques such as variable-density treatments or irregular return intervals in order to encourage the development of multiple age cohorts.
- Focusing salvage operations on creating desired residual stand structures following disturbance, even if less merchantable timber is removed as a result.
- Using site scarification, planting, or other techniques to support adequate regeneration.
- Maintaining a variety of age classes of a given forest type across a larger landscape.
- Maintaining a variety of stand structural or seral classes of a given forest type across a larger landscape, especially in approximate proportion to the natural range of variation.
- Managing competing vegetation in areas of older regeneration (typically 10 to 20 years post-fire) with prescribed burning and using a prescription that creates an appropriate mixture of tree and shrub survivorship and cover patchiness.
- Silvicultural or reforestation designs that emphasize arrays with a combination of scattered individual, clusters of trees and patches of open spaces.
Strategy
Strategy Text
Land managers already work to increase structural and species diversity in many cases, and as an adaptation strategy this general goal receives added effort and focus. Structural and species diversity may buffer a community against the susceptibility of its individual components to climate change. In other words, a community may still experience stress as individual components fare poorly, but the redundancy of particular roles and variability among all species’ responses contribute to the resilience of the community. Although a forest is often defined by its dominant or most abundant species, even rare species can act as keystone species or contribute to the suppression of invasive exotic plants.
1. Swanston, C.W.; Janowiak, M.K.; Brandt, L.A.; Butler, P.R.; Handler, S.D.; Shannon, P.D.; Derby Lewis, A.; Hall, K.; Fahey, R.T.; Scott, L.; Kerber, A.; Miesbauer, J.W.; Darling, L.; 2016. Forest Adaptation Resources: climate change tools and approaches for land managers, 2nd ed. US Department of Agriculture, Forest Service, Northern Research Station. 161 p. http://dx.doi.org/10.2737/NRS-GTR-87-2