The climatic response of trees that occupy closed canopy forests in the eastern United States (US) is important to understanding the possible trajectory these forests may take in response to a warming climate. Our study examined tree rings of 664 trees from five oak species (white ( Quercus alba L.), black ( Quercus velutina Lam.), chestnut ( Quercus prinus L.), northern red ( Quercus rubra L.), scarlet ( Quercus coccinea Münchh.)) from 17 stands in eastern Tennessee, western North Carolina, and northern Georgia to determine their climatic response. We dated the samples using skeleton plots, measured the cores, and compared the site- and regional-level tree-ring chronologies of each separate species with divisional climate data. The oldest trees in each chronology dated back to 203 years for black oak, 299 years for chestnut oak, 171 years for northern red oak, 135 years for scarlet oak, and 291 years for white oak. We successfully developed climate models via multiple regression analyses with statistically significant (P < 0.05) variables representing the Palmer Drought Severity Index and average monthly temperature for most of the site-species chronologies (average R² = 0.15). All regional climate response models included the Palmer Drought Severity Index from either June or July as the most significant variable in the climate response, suggesting that growing-season drought is the most important factor limiting oak growth in the southeastern US. An increase in temperature and reduction in moisture is likely to reduce their competitiveness in their current locations and force these species to migrate to cooler climates, thereby greatly changing ecosystem health and stability in the southern Appalachians.

Using dendrochronological analyses, we reconstructed a 300 year history of eastern spruce budworm ( Choristoneura fumiferana (Clem.)) outbreaks in northern interior Maine. By analyzing radial growth patterns from the budworm host, red spruce ( Picea rubens Sarg.), and nonhost, northern white cedar ( Thuja occidentalis L.), we identified five outbreaks beginning ca. 1709, 1762, 1808, 1914, and 1976, all of which have been documented from eastern Canada. However, little or no evidence was found in our study for the 1830s, 1870s, or 1940s outbreaks also documented there. The mean outbreak return interval in our study (67 years) was roughly twice that postulated for eastern Canada. Differences in forest types, and associated stand dynamics, between the regions may explain the longer return intervals, and consequently the absence of these three outbreaks in Maine. Results also indicate that small, slow-growing trees exhibit a budworm signal very similar to that of overstory trees, once tree-ring series have been properly standardized.

Opportunities for dendrochronology in the tropics are rare because few locations experience sesonality strong enough to induce annual (or even dependably cyclic) ring formation in trees. Consequently, any such opportunities that exist are valuable and identifying them is worth investing time and effort. West Indian pine (Pinus occidentalis Swartz) is endemic to the island of Hispaniola (l9°N, 71°W). It has prviously been shown not to produce useful rings in low-elevation (<2000 m) stands. We investigated its potential in small (4-11 tree) sample sets from four sites between 2000m and 3000m where seasonality of temperature and precipitation is more pronounced. Primary growth rings were distinct at all sites. False rings, diffuse rings, pinching rings and micro-rings were also present, and their number varied considerably by site. Quality of ring formation appeared to increase with both moisture stress (elevation, exposure, edaphic factors) and cold stress (elevation, exposure, cold-air drainage). We were able to cross-date saples (average interseries correlation= 0.44; average mean sensitivity= 0.44) from nine trees at the higheselevation site, and that chronology correlated significantly (r=–0.45, P<0.001) with monthly and sesonal maximum temperatures from a nearby meteorological station. This finding suggests a centuries-long reconstruction of temperature may be possible for this subtropical location. We conclude that, with careful site and tree selection, oversampling to allow exclusion of problematic specimens and greater use of coplete cross-sections rather than cores, P. occidentalis may allow dendrochronological reconstruction of climate, fire history and other environmental processes that operate on the island of Hispaniola.