Vegetation Response to Adaptive Silviculture Treatment Aimed at Climate Change in Northern Minnesota, USA

Abstract

The Adaptive Silviculture for Climate Change (ASCC) project was developed to provide regionally-specific examples of on-the-ground adaptation approaches that address complex management challenges. The ASCC project includes three adaptation options (resistance, resilience, and transition) along with a no action treatment for comparison. The first replicated ASCC site (MN-ASCC) is located on the Cutfoot Experimental Forest (CEF) on the Chippewa National Forest in northern Minnesota, USA. Research efforts presented here focus on short- and long-term vegetation response of the adaptation options by comparing initial performance of planted seedlings in the transition treatment, examining effects of adaptive treatments on below-canopy microclimate, and assessing and comparing long-term performance of each treatment using the Forest Vegetation Simulator (FVS) model. To assess seedling performance, eight future climate-adapted tree species were planted following harvest in 2015. Four native species and four novel species to the CEF were monitored for three years (2015-2018). Results show seedling performance varied among the planted species, overstory conditions, and shrub/herbaceous densities. These findings indicate it may be reasonable for managers to consider novel species compositions to begin transitioning forests to future-climate adapted species compositions. To explore the relationship between overstory condition and below-canopy microclimate, 40 microclimate stations were installed across four overstory conditions ranging in density levels. Hemispherical photography was used to estimate overstory conditions while microclimate variables were sampled hourly over the entire 2017 growing season. Results from this study highlight the potential for silvicultural treatments to enhance microsite conditions for diverse future-adapted species compositions. Additionally, these findings suggest it may be advantageous to maintain lower stocking levels of red pine to help retain soil moisture and further enhance microsite conditions. Finally, FVS was used to assess whether the ASCC treatments attained long-term desired future conditions and to determine treatment success in terms of growth, productivity, and survival. These results highlight the relative success of the transition treatment, which had greater volume production and lower mortality than the other treatments. Overall, these findings further our understanding of important tree- and stand-level responses to adaptive silviculture treatment, and highlights important real-world implications for today’s natural resource manager.