Climate-growth relationships for yellow-poplar across structural and site quality gradients in the southern Appalachian Mountains

Annual basal area increment (BAI) was most related to the Palmer Drought Severity Index (PDSI) during the months of May, June, and July (PDSIMJJ) relative to that of the annual or growing season when structural and site productivity variables were included in the analysis. Annual BAI of trees growing in stands of lower density responded to increases in PDSIMJJ at a faster rate than trees growing in stands of greater density. Conversely, those same trees experienced proportionally greater decreases in BAI at lower values of PDSIMJJ compared to trees in stands of greater density. Annual BAI was positivity related to site productivity, as quantified by site index, with BAI more sensitive to changes in PDSIMJJ on plots of progressively higher site index. Results suggest stand structure as well as measures of productivity should be considered when quantifying climate-growth relationships for forest tree species. Such information could not only aid in the identification of stands most susceptible to reduced growth, but also be used to develop site- or stand-specific silvicultural prescriptions focused on promoting resilience or resistance under a changing climate.