@article{mayfield iii_jetton_mudder_whittier_keyser_rhea_2023, title={Silvicultural canopy gaps improve health and growth of eastern hemlocks infested with & nbsp;Adelges tsugae & nbsp;in the southern Appalachian Mountains}, volume={546}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2023.121374}, abstractNote={The hemlock woolly adelgid (HWA, Adelges tsugae Annand) is an invasive forest insect threatening the sustainability of eastern hemlock (Tsuga canadensis (L.) Carrière) in eastern North America. In this study, cutting small gaps in the forest canopy above understory eastern hemlocks was evaluated as a potential tool for use in the integrated pest management of HWA. Two gap sizes and two gap creation methods (felling vs. girdling trees) were assessed for effects on HWA density, hemlock crown health, hemlock growth, and regeneration of competing tree species, at three different latitude groups in the southern Appalachian Mountains. In all three latitude groups, the treatment that removed the most canopy competition (Large Fell) increased the production of new hemlock shoots, reduced the percentage of dead shoots, and increased basal area increment of target hemlocks relative to unreleased trees. Smaller gaps and those that removed fewer competing live trees (Girdle treatments) also improved hemlock health in the southernmost latitude group. Positive effects of canopy gaps on hemlock crown condition and growth occurred despite similar or higher HWA densities on gap-released vs. unreleased trees. In regression analysis, more than half the variability in crown transparency change and basal area growth post-treatment was explained by the competition index of live trees remaining, average HWA density index, and tree size (dominant tree height and hemlock dbh). In the southernmost latitude group, the regeneration density of deciduous species increased significantly in the three years following gap creation and were highest in the Large Fell treatment. Results support the hypothesis that the increased availability of sunlight (and possibly other limited resources) resulting from canopy gaps (radius approximately ¼ to ½ dominant tree height) improves the physiological tolerance of eastern hemlock to HWA infestation and could complement biological control by providing a more stable source of new shoots with adelgid prey for predatory insects.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Mayfield III, Albert E. and Jetton, Robert M. and Mudder, Bryan T. and Whittier, William A. and Keyser, Tara L. and Rhea, James R.}, year={2023}, month={Oct} }
 @article{potter_jetton_whittier_crane_hipkins_echt_hodge_2022, title={Table Mountain Pine (Pinus pungens): Genetic Diversity and Conservation of an Imperiled Conifer}, volume={12}, ISSN={["1938-3738"]}, url={https://doi.org/10.1093/forsci/fxac043}, DOI={10.1093/forsci/fxac043}, abstractNote={Abstract}, journal={FOREST SCIENCE}, author={Potter, Kevin M. and Jetton, Robert M. and Whittier, W. Andrew and Crane, Barbara S. and Hipkins, Valerie D. and Echt, Craig S. and Hodge, Gary R.}, year={2022}, month={Dec} }
 @article{whittier_hodge_lopez_saravitz_acosta_2021, title={The use of near infrared spectroscopy to predict foliar nutrient levels of hydroponically grown teak seedlings}, volume={7}, ISSN={["1751-6552"]}, DOI={10.1177/09670335211025649}, abstractNote={ Due to a combination of durability, strength, and aesthetically pleasing color, teak ( Tectona grandis L.f.) is globally regarded as a premier timber species. High value, in combination with comprehensive harvesting restrictions from natural populations, has resulted in extensive teak plantation establishment throughout the tropics and subtropics. Plantations directly depend on the production of healthy seedlings. In order to assist growers in efficiently diagnosing teak seedling nutrient issues, a hydroponic nutrient study was conducted at North Carolina State University. The ability to accurately diagnose nutrient disorders prior to the onset of visual symptoms through the use of near infrared (NIR) technology will allow growers to potentially remedy seedling issues before irreversible damage is done. This research utilized two different near infrared (NIR) spectrometers to develop predictive foliar nutrient models for 13 nutrients and then compared the accuracy of the models between the devices. Destructive leaf sampling and laboratory grade NIR spectroscopy scanning was compared to nondestructive sampling coupled with a handheld NIR device used in a greenhouse. Using traditional wet lab foliar analysis results for calibration, nutrient prediction models for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), copper (Cu), molybdenum (Mo), magnesium (Mg), boron (B), calcium (Ca), manganese (Mn), iron (Fe), sodium (Na), and zinc (Z) were developed using both NIR devices. Models developed using both techniques were good for N, P, and K (R2 > 0.80), while the B model was adequate only with the destructive sampling procedure. Models for the remaining nutrients were not suitable. Although destructive sampling and desktop scanning procedure generally produced models with higher correlations they required work and time for sample preparation that might reduce the value of this NIR approach. The results suggest that both destructive and nondestructive sampling NIR calibrations can be useful to monitor macro nutrient status of teak plants grown in a nursery environment. }, journal={JOURNAL OF NEAR INFRARED SPECTROSCOPY}, author={Whittier, William Andrew and Hodge, Gary R. and Lopez, Juan and Saravitz, Carole and Acosta, Juan Jose}, year={2021}, month={Jul} }
 @article{potter_jetton_dvorak_hipkins_rhea_whittier_2011, title={Widespread inbreeding and unexpected geographic patterns of genetic variation in eastern hemlock (Tsuga canadensis), an imperiled North American conifer}, volume={13}, ISSN={1566-0621 1572-9737}, url={http://dx.doi.org/10.1007/s10592-011-0301-2}, DOI={10.1007/s10592-011-0301-2}, abstractNote={Eastern hemlock (Tsuga canadensis [L.] Carr.) is an ecologically important tree species experiencing severe mortality across much of its eastern North American distribution, caused by infestation of the exotic hemlock woolly adelgid (Adelges tsugae Annand). To guide gene conservation strategies for this imperiled conifer, we conducted a range-wide genetic variation study for eastern hemlock, amplifying 13 highly polymorphic nuclear microsatellite loci in 1,180 trees across 60 populations. The results demonstrate that eastern hemlock exhibits moderate inbreeding, possibly a signature of a prehistoric decline associated with a widespread insect outbreak. Contrary to expectations, populations in formerly glaciated regions are not less genetically diverse than in the putative southern refugial region. As expected, peripheral disjunct populations are less genetically diverse than main-range populations, but some are highly genetically differentiated or contain unique alleles. Spatially explicit Bayesian clustering analyses suggest that three or four Pleistocene glacial refuges may have existed in the Southeastern United States, with a main post-glacial movement into the Northeast and the Great Lakes region. Efforts to conserve eastern hemlock genetic material should emphasize the capture of broad adaptability that occurs across the geographic range of the species, as well as genetic variability within regions with the highest allelic richness and heterozygosity, such as the Southern Appalachians and New England, and within disjunct populations that are genetically distinct. Much genetic variation exists in areas both infested and uninfested by the adelgid.}, number={2}, journal={Conservation Genetics}, publisher={Springer Nature}, author={Potter, Kevin M. and Jetton, Robert M. and Dvorak, William S. and Hipkins, Valerie D. and Rhea, Rusty and Whittier, W. Andrew}, year={2011}, month={Dec}, pages={475–498} }
 @inproceedings{jetton_dvorak_whittier_potter_2009, title={Genetics and conservation of hemlock species threatened by the hemlock woolly adelgid}, booktitle={Proceedings of the 20th U.S. Department of Agriculture Interagency Research Forum on Invasive Species}, author={Jetton, R.M. and Dvorak, W.S. and Whittier, W.A. and Potter, K.M.}, year={2009}, pages={39–40} }
 @misc{jetton_dvorak_whittier_2008, title={Ecological and genetic factors that define the natural distribution of Carolina hemlock in the southeastern United States and their role in ex situ conservation}, volume={255}, ISSN={["0378-1127"]}, DOI={10.1016/j.foreco.2008.01.032}, abstractNote={Carolina hemlock (Tsuga caroliniana Engelm.) is a rare endemic found in the Appalachian Mountains and Upper Piedmont of the southeastern United States. It is being decimated by the hemlock woolly adelgid (Adelges tsugae Annand), an exotic pest introduced into the region from Japan several decades ago. We examine ecological, genetic and climatic factors in natural stands that characterize the species’ occurrence to better determine where ex situ conservation plantings should be established. To facilitate species/site matching, we use FloraMap™ software that quantifies climatic variables at provenance collection sites to predict other areas where Carolina hemlock could be planted in the U.S. and Latin America. Results indicate that based on analysis of 15 populations, Carolina hemlock is found on predominantly sandy-clay loam soils but occurs on a wider range of soil textural groups than previously thought. Its natural occurrence represents two different climatic groups, with the Cradle of Forestry, NC site most different than the rest. FloraMap™ predicts with high probability that Carolina hemlock populations can be successfully moved to central Chile, and with lower probability to the Ozark region of Arkansas and southern Brazil. Camcore, North Carolina State University, has now collected seeds from 12 provenances and 77 mother trees in natural populations of Carolina hemlock and distributed these to the three regions listed above. Our goal is to sample 150 trees from the 15 provenances which will sample most of the species’ genetic diversity for ex situ conservation. The ex situ approach offers an alternate means of protecting the species if efforts to control the adelgid fail in the southeastern US.}, number={8-9}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Jetton, Robert M. and Dvorak, William S. and Whittier, W. Andrew}, year={2008}, month={May}, pages={3212–3221} }
 @inproceedings{jetton_whittier_dvorak_potter_2008, title={Status of ex situ conservation efforts for eastern and Carolina hemlock in the southeastern United States}, booktitle={Proceedings of the 4th Symposium on Hemlock Woolly Adelgid}, author={Jetton, R.M. and Whittier, W.A. and Dvorak, W.S. and Potter, K.M.}, year={2008}, pages={81–89} }
 @article{potter_dvorak_crane_hipkins_jetton_whittier_rhea_2007, title={Allozyme variation and recent evolutionary history of eastern hemlock (Tsuga canadensis) in the southeastern United States}, volume={35}, ISSN={0169-4286 1573-5095}, url={http://dx.doi.org/10.1007/s11056-007-9067-2}, DOI={10.1007/s11056-007-9067-2}, abstractNote={Eastern hemlock (Tsuga canadensis [L.] Carr.) is a widespread and ecologically important conifer species of eastern North America that is threatened by the hemlock woolly adelgid (Adelges tsugae Annand), a pest introduced into the United States from Asia in the 1920s. Information about the genetic composition of eastern hemlock is necessary to guide ex situ conservation efforts in the southeastern United States, where the species is expected to harbor relatively high amounts of genetic variation in areas of Pleistocene glacial refuge. Nineteen allozyme markers were used to quantify the genetic variation present in 20 eastern hemlock populations in the southeastern United States. Results indicate that the species has low levels of genetic diversity in the region compared to most other conifers, but greater population differentiation (F ST = 0.126). Populations along the eastern periphery and in the Appalachian interior exhibited higher levels of diversity than those along the western periphery of its geographic range. The results suggest that the glacial refuge area for eastern hemlock was likely located east of the southern Appalachian Mountains, and indicate that ex situ conservation seed collections should be concentrated in these areas of higher diversity.}, number={2}, journal={New Forests}, publisher={Springer Nature}, author={Potter, K. M. and Dvorak, W. S. and Crane, B. S. and Hipkins, V. D. and Jetton, R. M. and Whittier, W. A. and Rhea, R.}, year={2007}, month={Oct}, pages={131–145} }