A comparison of floristic diversity in old-growth versus mid-successional secondary-growth hardwood forests of the White Mountain National Forest, New Hampshire, United States

There is currently debate over whether managed forests will ever regain the species diversity of old-growth stands. While succession and response to disturbance of tree species has been extensively researched, little similar effort has focused on understory herbaceous communities. This study conducted large-scale, comprehensive botanical inventories of three old-growth and three mid-successional (80–100 year old) secondary forest stands in New Hampshire's White Mountain National Forest (WMNF). Cluster analysis and TWINSPAN grouped the secondary sites within two steps. Old-growth floras were significantly richer in total, total herbaceous, woodland herbaceous, and unique herbaceous species. Abundance distributions of the two treatment groups were significantly different according to Chit results: more woodland herbaceous species of rare, infrequent, or dominant abundance rank occurred in old-growth sites. Floristic similarities were analyzed using Sorensen's Index of Similarity. Tree community data did not reflect differences in floristic diversity, suggesting that reliance on tree data alone to infer system recovery from disturbance would be misleading.