Dendroecology in young stands: case studies from jack pine in northern lower Michigan

Abstract

Eight jack pine ( Pinus banksiana) stands in northern lower Michigan were sampled to evaluate the potential of dendroecological methods for studying stand dynamics with young trees. At each stand, a minimum of 20 dominant and codominant trees were cored, and at two stands additional recruitment data were collected. The cores were all cross-dated and measured. The raw ring widths were used to identify growth suppressions and releases within the individual chronologies. Standardized master chronologies were developed, and the residual master chronology from each stand was correlated with temperature and precipitation to identify significant dendroclimatic relationships that may reduce the ecological signal in the tree-ring record. There were no important dendroclimatic relationships at any of the eight stands; therefore, the tree-ring record was largely a reflection of stand development. At all stands, suppression periods were more common than release events because all of the stands were composed of open-grown jack pine that had initial high rates of growth. The jack pine plantations had synchronous canopy closure (as evidenced by suppression), but the naturally regenerated stands had asynchronous canopy closure. Thus, the master chronologies were useful for identifying common stand-level growth patterns within plantations, but the individual tree chronologies were more useful within the naturally regenerated stands. One of the limitations of calculating suppression events in young trees was that the first and last 10 years of the chronology were excluded because of the equations used to calculate suppression events; therefore, any changes in growth pattern during these periods had to be visually identified. By combining quantitatively determined suppression events with recruitment data and visual interpretation of the chronologies, reconstruction of stand development events, canopy closure, thinning treatments and subsequent canopy re-closure, and changes in species composition associated with stand development were all identified within the tree-ring record. Thus, there is great potential for dendroecological studies in young trees to improve our understanding of the early stages of stand development.