Agricultural history drives structure and tree species composition of second growth forest over 100 years in southeastern Ohio, USA

Question: Most modern forest in eastern North America has recolonized after abandonment from agriculture. Cultivation and pasturing, historically the dominant forms of agriculture, differ in their environmental legacies and potentially influence stand development following abandonment. We ask how the legacy of agriculture plays out in development of second-growth stands, and whether tree community composition and structure differ between sites with contrasting land-use histories. Location: Southeast Ohio, USA. Methods: Thirty-five second-growth stands were sorted into a replicated chronosequence of formerly cultivated and pastured sites spanning 80yr. Stand age and land-use history were determined from historical aerial photographs and from site characteristics including microtopography and soil profiles. In addition, a control group was selected consisting of long-established forest stands showing no signs of agricultural disturbance. At each site stand composition and structure were described using the point-centred quarter method. Results: Stand density declined and basal area increased through the chronosequence but neither pastured nor cultivated sites reached levels observed in the control group. Density decreased most dramatically between the 41-60- and 61-80-yr age classes, consistent with competitive stand thinning. Tree community composition changed through time, reflecting a shift away from light-demanding successional species and toward long-lived, shade-tolerant species characteristic of long-established forests. Composition and structure did not differ significantly between cultivated and pastured sites, but individual species did show significant differences, with the greatest contrast evident shortly after abandonment. Conclusions: Stand development following agriculture appears to be a process of convergence in species composition and density. Because most deciduous forest in eastern North America is <80-yr-old, these results suggest that most forest is still accruing biomass and has yet to reach a stable density and composition.