Philip B. White

Abstract: We investigated the climatic sensitivity of oak species across a wide elevation range in the southern Appalachian Mountains, an area where greater knowledge of oak sensitivity is desired. We developed three tree-ring chronologies for climatic analyses from oak cores taken from the Jefferson National Forest, Virginia, and Great Smoky Mountains National Park, Tennessee. We statistically compared the three chronologies with monthly climatic data from 1930 to 2005. The results of our analyses suggest that oak species in the southern Appalachian Mountains require a cool, moist summer for above average-growth to occur. The climate signal increased in duration from high to low elevational and latitudinal gradients, indicating a strong moisture-preconditioning signal during the previous fall at our lowest elevation site. A notable finding of this research was the degree of responsiveness in oaks that are growing in forest interior locations where strong climate sensitivity would not be expected because of the effects of internal stand dynamics. Furthermore, the relationships between evapotranspiration rates and the geographic factors of elevation, latitude, and aspect influence the climate signals at the three sites. Our research suggests that oaks located in a warm and xeric climate experience more physiological stress and put forth a more varied climatic response.

Abstract: Red spruce-Fraser fir forests are geographically limited to high elevations in the Appalachian Mountains (USA) and are considered to be endangered in the USA. We investigated the successional status and radial growth patterns in the heavily disturbed red spruce Picea rubens Sarg. and Fraser fir Abies fraseri (Pursh) Poir. forest of Roan Mountain, Tennessee and North Carolina. This study elucidates the complexity of second-growth red spruce development after logging and disturbances by balsam woolly adelgid Adelges piceae Ratz. We documented precise temporal information of stand age, disturbance regimes, recruitment patterns, and the successional trajectory of the spruce-fir forest community. We used radial growth patterns of red spruce samples to detect the frequency and magnitude of disturbance. Red spruce was the oldest dominant canopy species, although Fraser fir had high recruitment rates over the past 80 yr. Changes in forest structure and species richness coincided with stand-wide disturbance events such as balsam woolly adelgid infestation and widespread early twentieth-century logging. The competitive advantage of Fraser fir over red spruce has resulted in an even-aged Fraser fir-dominant forest that occupies a relatively early stage of successional development. This study provides a 130 yr environmental history to assist land managers in the southern Appalachian Mountains as they develop long-term restoration plans for this unique ecosystem.

Abstract: We used dendrochronological techniques to develop a tree-ring chronology (AD 1874–2009) from live trees and investigated the temporal stability of regional climate signals in the heavily disturbed red spruce (Picea rubens Sarg.) and Fraser fir [Abies fraseri (Pursh) Poir.] forest of Roan Mountain, Tennessee and North Carolina, USA. We performed bootstrapped correlation analyses in split data sets and moving intervals analyses to detect shifts in climatic sensitivity during periods of changing forest structure following disturbances. Most notably, a significant shift in red spruce temperature sensitivity occurred post-1930s, where positive growth responses to warm temperatures shifted to negative responses, and this shift coincided with a period of clear cut harvesting. As exogenous disturbances (i.e. ice storms, wind throw, and acidic deposition) are expected to continue altering the structure of this forest throughout the region, the climatic sensitivity of these species may become increasingly unstable.

Abstract: We analyzed tree species composition and age structure in a rare, old-growth Quercus rubra L. (northern red oak) forest at Bluff Mountain Preserve, North Carolina, to assess potential changes associated with Cryphonectria parasitica (Murrill) M.E. Barr (chestnut blight), selective logging, livestock grazing, ice storms, wind events, and fire history. We established forest inventory plots to determine the forest composition, vertical structure, and age of the high- elevation Q. rubra dominated forest. We developed the longest Q. rubra dendroecological history (1671-2009) in North America. Several living Q. rubra individuals were more than 250 years old. The frequency, magnitude, and spatial extent of canopy disturbance events were shown in radial growth trends in Q. rubra samples. We also examined Q. rubra climate - radial growth relationships to compare high-elevation Q. rubra climate response patterns with results from lower elevation Quercus dendroclimatological studies. Stand-wide release events corresponded with the loss of Castanea dentata (Marsh.) Borkh. (American chestnut) during the 1930s and frequent ice storms or wind events. Although we observed fire scars on living hardwood trees, we did not find fire scars on the remnant logs. The lack of fire scars on the remnant logs indicates that the observed fires likely occurred during the second half of the 20th century. Quercus rubra were most climatically sensitive to cool March temperatures. Quercus rubra sampled at higher elevations were more sensitive to temperature than lower elevation Quercus spp. trees, which may indicate higher sensitivity to March frosts. Quercus rubra has been a dominant species at Bluff Mountain for the past 300 years; however, our data indicate that the forest will transition to support a much stronger Acer saccharum Marsh. (sugar maple) component during the next 50 years. This study provides a multicentury perspective to guide conservation efforts and forest management in high-elevation Quercus spp. forests in the southern Appalachian Mountains. Resume : L'auteur a analyse la composition en especes ligneuses et la structure de l'âge dans une rare foret surannee de Quercus rubra L. (chene rouge du nord) dans la reserve de Bluff Mountain, en Caroline du Nord, dans le but d'evaluer les

Abstract: Annual surface air temperatures across the eastern United States (US) have increased by more than 1 °C within the last century, with the recent decades marked by an unprecedented warming trend. Tree-rings have long been used as a proxy for climate reconstruction, but few truly temperature-sensitive trees have been documented for the eastern US, much less the Appalachian Mountains in the Southeast. Here, we measure blue intensity (BI) and ring width (RWI) in red spruce growing at the southernmost latitudinal range margin of the species on the North Carolina-Tennessee border to test the efficacy of using either metric as a temperature proxy in the eastern US. The BI and RWI chronologies spanned 1883–2008 and had an interseries correlations of 0.42 and 0.54, respectively, but time series were trimmed to the period 1950–2008 due to low sample depth. We discovered strong, positive, and stable correlations between both current-year early fall (September–October) Tmax (r = 0.62; p

Abstract: We review and synthesize information on invasions of nonnative forest insects and diseases in the United States, including their ecological and economic impacts, pathways of arrival, distribution within the United States, and policy options for reducing future invasions. Nonnative insects have accumulated in United States forests at a rate of ~2.5 per yr over the last 150 yr. Currently the two major pathways of introduction are importation of live plants and wood packing material such as pallets and crates. Introduced insects and diseases occur in forests and cities throughout the United States, and the problem is particularly severe in the Northeast and Upper Midwest. Nonnative forest pests are the only disturbance agent that has effectively eliminated entire tree species or genera from United States forests within decades. The resulting shift in forest structure and species composition alters ecosystem functions such as productivity, nutrient cycling, and wildlife habitat. In urban and suburban areas, loss of trees from streets, yards, and parks affects aesthetics, property values, shading, stormwater runoff, and human health. The economic damage from nonnative pests is not yet fully known, but is likely in the billions of dollars per year, with the majority of this economic burden borne by municipalities and residential property owners. Current policies for preventing introductions are having positive effects but are insufficient to reduce the influx of pests in the face of burgeoning global trade. Options are available to strengthen the defenses against pest arrival and establishment, including measures taken in the exporting country prior to shipment, measures to ensure clean shipments of plants and wood products, inspections at ports of entry, and post-entry measures such as quarantines, surveillance, and eradication programs. Improved data collection procedures for inspections, greater data accessibility, and better reporting would support better evaluation of policy effectiveness. Lack of additional action places the nation, local municipalities, and property owners at high risk of further damaging and costly invasions. Adopting stronger policies to reduce establishments of new forest insects and diseases would shift the major costs of control to the source and alleviate the economic burden now borne by homeowners and municipalities.

Abstract: Previous studies of the impacts of climate change on lichens and fungi have focused largely on alpine and subalpine habitats, and have not investigated the potential impact on narrowly endemic species. Here, we estimate the impacts of climate change on high-elevation, endemic lichens in the southern Appalachians, a global diversity hotspot for many groups of organisms, including lichens. We conducted extensive field surveys in the high elevations of the region to accurately document the current distributions of eight narrowly endemic lichen species. Species distribution modeling was used to predict how much climatically suitable area will remain within, and north of, the current range of the target species under multiple climate change scenarios at two time points in the future. Our field work showed that target species ranged from extreme rarity to locally abundant. Models predicted over 93 % distributional loss for all species investigated and very little potentially suitable area north of their current distribution in the coming century. Our results indicate that climate change poses a significant threat to high-elevation lichens, and provide a case study in the application of current modeling techniques for rare, montane species.