Long-term stand-level resilience in natural secondary forest stands recovering from severe windthrow damage

Long-term stand-level resilience in three natural secondary forests after a stand-replacing windthrow damage event was examined by analyzing stand composition, structure, and function using repetitive measurement data collected in permanent plots over 60 yr. The secondary forests differed among pre-disturbance forest types. For the purposes of this study, stand resilience comprised resistance to and recovery from windthrow damage. To analyze composition, the dynamics of species numbers in the permanent plots were tracked and temporal trends in similarity between pre- and post-disturbance compositions were examined. To investigate stand structure, the dynamics of tree density, mean diameter at breast height (DBH), and temporal trends in similarity between pre- and post-disturbance DBH frequency distributions were analyzed. To investigate stand function, the dynamics of stand basal area were analyzed. The calculations showed that tree density, basal area, species composition, and DBH frequency distribution were associated with low resistance to windthrow damage. By contrast, the number of species and mean DBH were resistant to windthrow damage. Basal areas recovered quickly in the 60 yr post-windthrow damage, but recovery of the pre-damage mean DBH and DBH frequency distribution was slow. Tree density and the number of species recovered to levels that exceeded those in the stands prior to the windthrow event. The recovery of species composition varied by pre-disturbance forest type. Among the stands analyzed, the hardwood forest that existed prior to disturbance was resistant to and recovered well from windthrow damage in comparison with other types of pre-disturbance forests. In conclusion, stand-replacing windthrow damage can have a long-lasting influence on secondary forests, especially in terms of stand composition and structure.