Silviculture for eastern old-growth in the context of global change
Creators: name: Keeton, William S.
Publisher: name: F1000 Research Limited
Year: 2019

description: Many have wondered if silviculture could be used to restore characteristics of eastern old-growth forests, both in reserves and managed forests. After several decades of research this proposition is no longer theoretical. Rather, old-growth silviculture is employed operationally in a variety of settings. And yet a variety of novel stressors, including climate change and invasive pests and pathogens, pose serious challenges. With baselines shifting, adaptive old-growth silviculture must be designed to increase system resilience and sustain critical functions into the future. There is no “one-size-fits-all” approach for old-growth silviculture. Rather, forest managers can target a range of old-growth characteristics. This talk will review several such approaches, focusing specifically on a system called <i>Structural Complexity Enhancement</i> (SCE). The working hypothesis is that by emulating both density-dependent and density-independent mortality processes, SCE can accelerate rates of late-successional development faster than conventional selection systems. Response variables include financial viability, late-successional biodiversity, tree regeneration, and aboveground carbon pools. The Before-After-Control-Impact designs compares SCE against two modified uneven-aged treatments. Manipulations and controls were applied to 2 ha units and replicated four times at two research areas in the Green Mountains of Vermont. The selection treatments and controls were replicated two additional times in the Adirondack Mountains of New York. Field data were collected over two years pre-treatment and 18 years post-treatment. Operational expenses and revenue were tracked during and after logging operations, as was information on market conditions. Ten years after harvest, measured aboveground carbon in SCE units was 15.9% less than simulated no-harvest baselines, compared to 44.9% less in conventional treatments. All treatments were successful in maintaining overall richness and/or abundance of understory plants, terrestrial salamanders, and fungi. Statistical model results show that understory plant responses were strongly affected by treatment and less influenced by soil chemistry and drought stress. However, diversity for sensitive, late-successional herbaceous plants increased significantly in SCE units and decreased significantly in the semi-open canopied conditions within group selection units. Fungi and salamander responses were strongly associated with microsite characteristics, particularly coarse woody debris, and increased significantly under SCE, but showed no statistically significant decrease in silvicultural gaps. SCE is economically profitable or breaks even under the right site and market conditions. Potential applications include old-growth restoration, riparian restoration, carbon management, and low intensity commercial management. Adaptive silviculture promoting old-growth forest characteristics will contribute to biodiversity conservation and climate mitigation while providing both timber and non-timber economic opportunities.