White pine seed-tree legacies in an aspen landscape: influences on post-disturbance white pine population structure

Abstract

White pines that survived late nineteenth century logging and wildfires in the Great Lakes region act as seed-sources for white pine regeneration in aspen and oak ecosystems that developed following these disturbances. The local abundance of remnant white pines may influence the direction of succession following disturbance, yet no studies have quantified relationships between characteristics of remnant white pine seed-sources and the structure of post-disturbance white pine populations. The objective of the present study was to relate the number, size, and location of remnant white pine seed trees to the structure of post-disturbance white pine populations. The study was conducted in a 75–80 year old bigtooth aspen-dominated forest in northern Michigan. White pine seed-source characteristics varied considerably across the study area, as did stem densities and the age and height structures of post-disturbance white pine populations. Regenerating white pine populations which were located close to several large remnant trees were larger, began establishing sooner after disturbance, and contained a greater diversity of age and height classes relative to populations with less favorable seed-source characteristics. Additionally, plots with small post-disturbance white pine populations often had large populations of red maple advanced regeneration. Variable successional pathways in the study area may reflect the influence of remnant white pine seed-sources, and ultimately, a disturbance history that allowed some seed trees to survive logging and wildfires. Retention of large white pine seed trees in commercial aspen forests may be an important silvicultural tool if a goal of management is to maximize structural and compositional diversity in managed stands.