Effects of organic matter removal and soil compaction on fifth-year mineral soil carbon and nitrogen contents for sites across the United States and Canada

This study describes the main treatment effects of organic matter removal and compaction and a split-plot effect of competition control on mineral soil carbon (C) and nitrogen (N) pools. Treatment effects on soil C and N pools are discussed for 19 sites across five locations (British Columbia, Northern Rocky Mountains, Pacific Southwest, and Atlantic and Gulf coasts) that are part of the Long-Term Soil Productivity (LTSP) network and were established over 5 years ago. The sites cover a broad range of soil types, climatic conditions, and tree species. Most sites showed increased soil C and N levels 5 years after study establishment; however, the rate and magnitude of the changes varied between sites. Organic matter removal, compaction, or competition control did not significantly affect soil C and N contents at any site, except for the Northern Rocky Mountain site, where competition control significantly affected soil C and N contents. The observation that, after 5 years, the soil C and N contents were not negatively affected by even the extreme treatments demonstrates the high resiliency of the soil, at least in the short term, to forest management perturbations.