The nature of plant competitive interactions and their resulting influence on community structure and dynamics have long been a central focus of research in forest ecology. Despite a volume of work on neighborhood competition dynamics within a given forest age class, little is known about how the nature and importance of neighborhood competition changes over the course of stand development. Likewise, the role these interactions play in influencing stand structure and carbon sequestration patterns within and among communities has received little attention. This study uses dendroecological data collected from a red pine (Pinus resinosa) chronosequence spanning 150 years, as well as six old-growth stands to examine how neighborhood competition has influenced patterns of growth and development within this common forest type. In particular, this dataset includes 25 stands ranging in age from 20 to over 300 years allowing us to address questions including: 1) How does the importance and intensity of neighborhood competition change with stand age and overall population structure, and 2) How do patterns of carbon sequestration, as quantified via tree-ring data, vary within a population relative to the intensity of competition among individuals?
Results/Conclusions
Red pine stands sampled along the chronosequence were strongly even-aged and were either of logging or fire-origin. In contrast, age structures within old-growth stands were either even-aged or two-aged with over 100 year periods often separating cohorts. Variability in growth patterns and sequestration rate was strongly related to stand age and structure, with stands in the stem-exclusion phase (50-85 years) exhibiting the greatest degree of within-stand variability. The importance of neighborhood competition in explaining patterns of growth followed a similar pattern, as models predicting growth as a function of neighborhood conditions had the strongest level of support within these 50-85 year-old stands. In contrast, stand-level measures of stocking were the best indicators of growth in young stands, whereas models incorporating measures of individual tree competitive status and neighborhood competition had the highest levels of support for old-growth stands. The implications of these varying spatial and temporal competition patterns to achieving objectives, including managing for carbon sequestration and promoting late-seral structure, will be discussed.
