A comparison of soil organic matter content in 1932, 1984, and 2005/6 in forests of the Adirondack Mountains, New York

We quantified the organic matter content of organic and mineral horizons in 1932, 1984, and in 2005/6 at 54 sites in a mixed hardwood-softwood stand and in northern hardwood (NH), pine-dominated (PW), and spruce-fir (SF) forests of the Adirondack Mountains, NY to determine if there were measurable changes in soil organic matter (SOM) pools over the ~75-yr interval. Further, the different land-use histories of these sites provided an opportunity to evaluate the influence of land-use history on forest SOM since the early 1930s. Overall, there were no significant differences in combined organic + mineral horizon (whole-profile) SOM amounts over the interval. There was, however, a significant increase in whole-profile SOM content between 1932 and 2005/6 at 16 sites that had a history of agriculture or fire which amounted to an increase in C content of approximately 0.5 Mg C [ha.sup.-1] [yr.sup.-1]. This indicated that at least some Adirondack forest soils were accumulating C during the 20th century. Abbreviations: LOI, loss-on-ignition; MSD, minimum significant difference; NC, Newcomb; NH, northern hardwood; OM, organic matter; PW, pine-dominated; SE spruce-fir; SOM, soil organic matter. doi:10.2136/sssaj2009.0132N