Assembling the forest herb community after abandonment from agriculture: Long-term successional dynamics differ with land-use history

1. Cultivation and pasturing, both historically common forms of agriculture in eastern North America, differ in their long-term environmental legacies. We ask whether successional reassembly of the forest herb community differs between second-growth stands with contrasting agricultural histories. We predicted that herb communities would diverge through a process of environmental filtering as colonist species responded to the agricultural histories of individual sites and to underlying edaphic gradients. 2. Thirty-five second-growth stands were grouped into a replicated chronosequence of formerly cultivated and pastured sites spanning 80 years after canopy closure. Five long-established stands without signs of agricultural history were included as controls. Herbaceous vegetation and soil and environmental variables were recorded at each site. 3. Forest herb species accumulated through the chronosequence. Community composition changed through successional time, transitioning from open-forest species to shade-tolerant perennial herbs, and differed significantly between pastured and cultivated sites. A high degree of similarity among control sites suggests eventual convergence, although chronosequence sites at 80 years had not yet reached the richness and composition observed in the controls. Agricultural practices were initially distinguishable in species richness, evenness, and composition but agricultural influence receded as the stands approached 80 years. 4. Synthesis. Community assembly in post-agricultural forests appears to be a process of site-level convergence driven by gradual accumulation of species from the regional species pool, relatively rapid conformity to soil gradients and growth of the forest stand. This result is scale-dependent; distributions are controlled by topographic filtering at coarser and finer scales.