Effects of climate, disturbance, and management on the growth and dynamics of temperate and sub-boreal forest ecosystems within the Lake States and New England

This project is using a combination of long-term data records and recently established large-scale adaptive management studies in managed forests across the Lake States, New England, Intermountain West, and Black Hills to identify forest management strategies and forest conditions that confer the greatest levels of resistance and resilience to past and emerging stressors and their relevance in addressing future global change.  This work represents a broad partnership between scientists from the USFS Northern Research Station, USFS Rocky Mountain Research Station, USGS, University of MN,  University of Maine, and Dartmoutch College in an effort to capitalize on over 50 years of data collection on USFS Experimental Forests and Forest Inventory and Analysis plot to evaluate forest adaptation strategies. In addition, this project includes two installations of the Adaptive Silviculture for Climate Change (ASCC) network in northern MN and northern NH and is using these sites to examine resistance, resilience, and transition strategies for these forests and resultant impacts on ecosystem services and wildlife populations.

Preliminary Results

Examinations of population-level responses to historic drought periods within red pine forests in Minnesota indicate a general increase in drought vulnerability with increasing tree density, particularly at extremely high densities.  In addition, populations maintained at low tree densities, while unaffected by drought at young ages, were more susceptible to drought at older ages due to the higher physiological burden of large trees in those stands.  Results suggest that thinning is a viable option for reducing drought vulnerability; however, extreme density reductions should be avoided.  Related analyses in other mixed conifer and northern hardwood forests in the Great Lakes region indicate an additional benefit from maintaining a diversity of tree sizes within a population to minimize drought impacts.  Evaluations of the importance of drought as a driver of growth patterns in these populations indicate that conifer-dominated forest systems in both Lake States and Northeastern States are more sensitive to historic drought than northern hardwood dominated forests in these regions.  Results from ponderosa pine-dominated systems in South Dakota and Arizona suggest a similar importance of forest density in determining population-level sensitivity to drought with universal relationships between relative density and drought vulnerability across populations.  In addition to examining thinning impacts on drought vulnerability, we have also capitalized on long-term prescribed burning studies to determine the impacts of this common habitat management practice on drought resistance and resilience.  Findings from this work indicate that prescribed burning has an initial negative effect on the ability of trees to resist drought effects, but neutral to positive long-term impacts due to reductions in understory trees and shrubs and concomitantly greater levels of moisture availability.  Inherent in each of these long-term evaluations has been a dynamic shift over time regarding the vulnerability of a given managed populations to drought effects, underscoring the importance of anticipating long-term feedbacks between otogenetic changes in habitat characteristics and climate.  In addition, drought impacts have been highly dependent on tree population densities across the broad geography of areas examined (AZ, SD, ME, NH, MN, WI, OH) highlighting the importance of accounting for population structure when predicting future climate response of a given tree species or forest habitat type.

Tools and Products

Increasing Forest Resiliency for an Uncertain Future   A guidance report for forest managers that will help develop ahead with proactive actions.