Volume 1 I June 2021
Science Findings of the USDA Forest Service Northern Research Station
Northern Research Station
Climate Adaptation Science Roundup
Building on the last new thing: exploring the compatibility of ecological and adaption silviculture 
This hot-off-the-press study, published in 2020 by scientists D’Amato and Palik, examines how the guiding principles of ecological silviculture – continuity, complexity and diversity, timing, and context – remain relevant in advancing silviculture for climate change adaptation. This paper unpacks the often-theoretical concepts of ‘adaptive capacity’ and ‘adaptive silviculture’ into tangible on-the-ground actions forest managers can implement.
Management Considerations

  • Forest management actions that consider the following four principles are likely to confer both ecological resilience and adaptive capacity at stand and landscape scales:
  • Continuity – such as through retention and protection in forest structure, function, and biota during harvests.
  • Complexity and diversity – such as maintaining heterogeneity in structure and composition across multiple scales.
  • Timing – such as extended rotations.
  • Context – e.g., spatial heterogenous application of the above three principles to generate a diversity of forest development stages and conditions across multiple scales.
  • The general outcomes of ecological silviculture, including high levels of heterogeneity in structural and compositional conditions at stand and landscape scales, align with recommendations for increasing forest adaptive capacity, thus suggesting compatibility in approaches.
  • Given the uncertainties around future climate change, no singular forest management approach is a ‘silver bullet.’ Management that incorporates concepts of biodiversity conservation and adaptation can be complementary. 
Combining US and Canadian forest inventories to access habitat suitability and migration potential of 25 tree species under climate change
The study evaluated the current and future dynamics of 25 tree species spanning the United States and Canada to assess suitable climatic habitat under future climate change scenarios. Using 21 climatic variables under different emissions pathways, this study evaluates range-wide habitat suitability and migration potential of tree species. At a continental scale, many species in the conterminous United States lose suitable climatic habitat but gain habitat in Canada and Alaska. For most species, even under optimistic migration rates, only a small portion of overall future suitable habitat is projected to be naturally colonized in ~100 years. Considerable variation among species points to the need for significant management efforts, including assisted migration, for economic or ecological reasons.
Management Considerations

  •  Modeling results in this study may help to identify suitable conservation strategies for the various tree species examined.
  • Featured tree species may require different conservation approaches in the United States (within-range conservation) and Canada (range expansion), thus requiring cross-border collaboration.
  • Leading edge (northernly) habitats are projected to expand rapidly due to greater warming. Trailing-edge populations may remain viable, but subject to greater climatic stress.
  • Within-range movements of climatically suitable genotypes represent a low-risk form of assisted migration that could help align population-level climate preferences with projected future climates.
Climate adaptive silviculture strategies: How do they impact growth, yield, diversity, and value in forested landscapes?
Forest managers are often seeking guidance on how to manage forests in the face of climate change. Empirically based recommendations are challenging to develop as it can take decades to assess the response of forests to different treatments. Forest landscape models provide a powerful tool to assess long-term effectiveness of management actions for building climate adaptive capacity. This new paper by Gustafson, et al. and published in Forest Ecology and Management uses the LANDIS model to assess the landscape-wide effects of alternative tree cutting and planting practices under three climate change scenarios simulated over 300 years within the Laurentian Mixed Forest Province. The goal of this research is to assess how different silvicultural strategies designed to maintain ecological and economic values of forests under future climates compares to that of “business as usual” silviculture scenarios representing current sustained yield practices.
Management Considerations

  • While drastic, forest-wide mortality events due to management or climate are unlikely, results show that Laurentian forests (conifer, mixed hardwood and conifer, and conifer bogs) of today cannot be maintained in the current state under projected climate futures. Maintaining productivity and resilience may require creative silvicultural practices.
  • Under future climate scenarios, broadleaf species (oaks, maples) tend to outcompete conifer species.
  • Climate adaptation practices can maintain productivity and economic value, maintain diversity (albeit with altered species), and provide options for adaptive management over time.
  •  In the Northwoods, climate change is projected to increase the biomass of all species (due to carbon dioxide fertilization and longer growing seasons), although the most cold-adapted species (white spruce, black spruce, jack pine, red pine, aspen, and white cedar) eventually declined under warming climate scenarios.

Desired Regeneration though Assisted Migration
Given the high level of uncertainty in the timing and intensity of climate change and the resulting impact on forests, land managers need access to the best available science to support strategies that confer resilience to a broad range of climatic futures. Assisted migration, often a controversial topic, can serve as a powerful tool for land managers interested in exploring the full range of adaptive silvicultural strategies. DREAM (Desired Regeneration though Assisted Migration) is a new research endeavor led by NRS scientists Alex Royo, Christel Kern, Dustin Bronson, and Bryce Adams that calls for active researcher-manager collaboration to develop experimental designs in harvest schemes and tree species planting tailored to regional needs. The goal of this new project is to provide guidelines on how to maximize future-adapted tree stock success efficiently and cost-effectively. 
Management Considerations

  •   Changes in climate may outpace the rate of natural plant adaptation and migration. This mismatch presents a challenge for land managers making decisions about what tree species to select, grow, and plant during reforestation and restoration projects.
  • Climate analogs serve as a tool to identify locations in space and time that share similar climatic conditions, thus supporting the potential identification of source populations and/or novel tree species that may be potentially future adapted.
  •  Testing physiological tolerances and experimentally planting novel tree species can provide answers to land managers on what tree species may thrive in future climates.

Wide-spread vulnerability of black ash (Fraxinus nigra Marsh.) wetlands in Minnesota USA to loss of tree dominance from invasive emerald ash borer
The emerald ash borer (EAB) has killed ash species across much of eastern North America, but it has yet to reach the vast ash wetlands in northern Minnesota. Across approximately 1 million acres of wetlands in northern Minnesota and roughly 850,000 acres in Wisconsin, a single species, black ash, comprises a majority of trees and has a foundational role in controlling ecosystem function. Given the likelihood of wide-spread mortality of black ash from EAB researchers are investigating what co-occurring and already present tree species may replace black ash. In this recently published paper by Palik, D’Amato, and Slesak, researchers’ examined woody plant communities across 32 black ash sites and demonstrate a region-wide lack of species capable of replacing black ash, pointing out an urgent need for silvicultural interventions.
 
To ensure long-term resilience and ecosystem function, land managers must take action to identify and establish future-adapted non-ash tree species in this wetland systems. 
Management Considerations

  • Generally, there is very low potential that other tree species will naturally replace black ash from either expansion in the overstory or through release of advanced regeneration from lower vegetation levels.
  • Implementing silvicultural actions to establish regeneration of non-ash trees species in sites threatened by EAB will help promote resilience of ecosystem function.
  • Swamp white oak, hackberry, and Dutch elm disease tolerant varieties of American elm are good potential species for ash replacement.
  • Working proactively to establish site appropriate tree species through silvicultural treatment, potentially including native non-ash, as well as non-native species, will help ensure a climate adapted future.
About Rooted in Research

Rooted in Research is a science communications platform of the Northern Research Station focused on delivering the latest science for land management needs and highlighting key science findings to people who make and influence decisions about managing land.
 
Forest Service Research and Development (FS R&D) works with partners to deliver the knowledge and tools that land managers need to sustain the health, diversity, and productivity of our Nation’s forests and grasslands for present and future generations. The Northern Research Station (NRS), one of seven FS R&D units, is rooted in the geography of the Northeast, Central Appalachians, and Midwest. NRS science improves lives and landscapes.

For more information, please contact
Andrea Brandon, Science Delivery Specialist, andrea.brandon@usda.gov