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Keywords:

  • carbon;
  • density;
  • historic land use;
  • land use legacy;
  • nitrogen;
  • restoration;
  • soil

Abstract

We present results on changes in soil properties following land use change over an approximately 55-year period at Fort Benning, Georgia, U.S.A. Soil cores were taken at 129 locations that were categorized as reforested (field/bare ground in 1944 and forest in 1999), disturbed (field/bare ground in 1944 and 1999), or reference forests (forest in 1944 and 1999). Soil disturbance included historic agriculture (pre-1944) and military training (post-1944). Density in mineral soils exhibited a historic land use legacy effect (reference < reforested < disturbed). Rates of change in bulk density decreased with depth and estimated total times to reach reference forest levels ranged from 83 (0–10 cm) to 165 (30–40 cm) years. A land use legacy effect on C stock was apparent in the O-horizon and in 30- to 40-cm soil increment (reference > reforested > disturbed). Soil C stock in all other increments and in particulate organic matter was affected by disturbance; however, no legacy was apparent (reference = reforested > disturbed). For the entire soil profile (O-horizon to 40 cm), rate of C accrual was 28 g m−2 yr−1 (1.5%/yr). Nitrogen stocks were affected by disturbance in the O-horizon and 0- to 10-cm increment; however, no legacy effect was detected (reference = reforested > disturbed). Nitrogen accumulated at 0.56 g m−2 yr−1 (0.6%/yr) for the entire soil profile. At Fort Benning, soil C and N stocks of reforested stands were similar to those of reference forested stands after approximately 55 years. However, soil bulk density was greater on reforested stands than reference forest stands at 55 years and may require an additional century to reach reference levels.