Abstract:
The conversion of agriculture lands to forest has been occurring in parts of North America for decades. The legacy of management activity during this transition is reflected in soil physical and chemical properties years after abandonment. This study was conducted at the Smithsonian Environmental Research Center, Maryland, USA, to determine land-use history and forest age effects on soil nutrients, carbon, pH, and bulk density. Soils in young and old successional forests and forests with no evidence of historical disturbance were sampled. The young forest stands were abandoned from agriculture 50 70 years ago and the old forest stands had been abandoned from agriculture or grazing 120 150 years ago. The oldest forest stands had no recorded history of disturbance even though it is likely they were at least disturbed by tree removal or grazing of animals in the colonial era. Young forest soils had higher concentrations of Mg, Ca, NO3 and a higher pH than old, which may be an age effect. The old forest soils that had been abandoned from agriculture and grazing had higher bulk density and lower C content than undisturbed stands indicating a land-use effect. In the stands that were formally agriculture there was evidence of erosion, indicated by a Bt horizon closer to the surface. The most evident difference between stands of different land-use history was the absence of a well-developed O horizon, which we attribute to the presence of earthworms. Land-use legacy set the forest ecosystem in a different trajectory of soil evolution.
