Abstract
Sandy outwash and glacial till soils compose large amounts of public forestland due to historically poor agricultural yields. The outwash soils have low fertility, poor nutrient retention and are restricted from whole-tree harvesting (WTH) in some states, whereas the glacial till has medium nutrient retention and fertility, and is unrestricted from WTH. To assess the long-term sustainability of harvesting, a nutrient budget was constructed from field measurements, the National Cooperative Soil Survey (NCSS) database, and literature values for stem-only harvesting (SOH) and WTH at a 45-year rotation length and 11 rotations were simulated. The budgets showed that SOH and WTH recovery years, or the time necessary for the inputs to match outputs through leaching and one harvest, exceeded common rotation lengths for both soil types under all weathering scenarios, and the average WTH reduced the total available rotations by one harvest. The large variation in soil nutrient pools and harvest removals complicated the ability to identify the difference between SOH and WTH early in the model, but differences became apparent with sequential harvests. The recovery years were 2–20 times the 45-year rotation length under all weathering rates. Taken together, models in this study bridge the gap between short- and long-term studies and bring into question the sustainability of WTH and SOH practices on nutrient-poor soils.
Highlights
College of Forest Resources and Environmental Science, Michigan Technological University, U.S Forest Service—Northern Research Station, 410 MacInnes Drive, Houghton, MI 49931, USA
Simulations showed that increased harvest intensity from stem-only harvesting (SOH) to whole-tree harvesting (WTH) of aspen on nutrient-poor soils shortened the available nutrient pools on average by one full rotation length for Ca, Mg, and K, and K for the slightly richer
N and P were less impacted for both soils since the percent removed in each harvest was generally small in comparison to the residual tissues and soil pools
Summary
College of Forest Resources and Environmental Science, Michigan Technological University, U.S Forest Service—Northern Research Station, 410 MacInnes Drive, Houghton, MI 49931, USA. The outwash soils have low fertility, poor nutrient retention and are restricted from whole-tree harvesting (WTH) in some states, whereas the glacial till has medium nutrient retention and fertility, and is unrestricted from WTH. The budgets showed that SOH and WTH recovery years, or the time necessary for the inputs to match outputs through leaching and one harvest, exceeded common rotation lengths for both soil types under all weathering scenarios, and the average WTH reduced the total available rotations by one harvest. Models in this study bridge the gap between short- and long-term studies and bring into question the sustainability of WTH and SOH practices on nutrient-poor soils. 1. Introduction with regard to jurisdictional claims in Nutrient-poor and medium fertility soils, such as glacial outwash (Typic Udipsamments, Entic Haplorthods) and tills (Alfic Haplorthods), are abundant throughout the Great
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