Forest diversity and composition changed over 120 years of post-agricultural succession in Cleveland Metroparks, Ohio, USA

Abstract Changes in land use have radically impacted forests in the USA over the past several centuries. This study examined how the long-term effects of agricultural land use shape the vegetation structure, diversity, composition, and environmental conditions of forests in the urban Cleveland Metroparks, Ohio, USA. We assigned land-use histories to 285 forest plots to create a successional chronosequence. Post-agricultural forests had different indicator species, tree and understory composition from primary forests (i.e., forests never cleared for agriculture). Stem density remained consistent across forest types, but basal area varied slightly, with conifer plantations having the largest. Native understory cover was highest in primary forests, at nearly three fourths, and declined with decreasing forest age, while invasive cover increased from 12% in primary forests to 40% in the youngest post-agricultural forests. Although post-agricultural forests had higher total species richness, primary forests exhibited greater evenness and Shannon diversity. FQAI, a measure of vegetation conservation value, was highest in primary forests and decreased with decreasing forest age. Canopy openness also differed, being more open in younger forests and closed in older and primary forests, influencing understory composition to be more shade-tolerant where the canopy was more closed. Chronosequence analysis revealed that post-agricultural forests increasingly resembled primary forests over time, though critical differences persisted. These findings highlight the enduring influence of land-use history on forest succession and emphasize the conservation value of primary forests, which support high native cover, low invasive cover, high floristic quality, and species composition most similar to presettlement forests.