Organic Matter Removal from Forest Soils: Lessons from the Long-Term Soil Productivity Study.

The North American Long-Term Soil Productivity experiment was installed 25 years ago to study the fundamental ways in which forest management affects site productivity across North American timberlands. It started as an effort between the USFS Research and Development and National Forest Systems branches to provide science for soil quality standards, but quickly expanded to include cooperators from Canada, forest industry and universities.

One of the primary mechanisms by which forest management affects site productivity is the removal of organic matter. Three levels of organic matter removal, which included bole-only and whole tree timber harvest and complete aboveground organic matter removal, were studied on a shared design on 60 sites in the U.S. and Canada. An additional group of affiliate studies incorporated the fundamental treatments in some way but often included other treatments often mitigation treatments.

Overwhelmingly, the last two decades of results have indicated that forest site productivity in North America is highly resistant and resilient to the one-time removal of even all aboveground organic matter. Neither soil properties nor planted tree growth have shown consistent effects from removals. However, a number of site-specific responses have been observed that improve our overall understanding of the fundamentals of sustaining site productivity. After 25 years, this self-supported research network has continued to grow and will continue to incorporate new affiliate studies and investigators, especially ones aimed at improving guidelines for biomass removal.