ARTICLE IN PRESS Dendrochronologia 22 (2004) 7–29 www.elsevier.de/dendro ORIGINAL ARTICLE The influence of winter temperatures on the annual radial growth of six northern range margin tree species Neil Pedersona,b,Ã, Edward R. Cookb, Gordon C. Jacobyb, Dorothy M. Peteetc, Kevin L. Griffina,d aDepartment of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, P.O. Box 1000, 61 Rt. 9W, Palisades, NY 10976, USA bTree-Ring Laboratory, Lamont-Doherty Earth Observatory, Palisades, NY, USA cPaleoecology Laboratory, Lamont-Doherty Earth Observatory, NY, USA dPlant Physiological Ecology Laboratory, Lamont-Doherty Earth Observatory, Palisades, NY, USA Received 21 December 2003; accepted 11 May 2004 Abstract This study explores the influence of temperature on the growth of six northern range margin (NRM) tree species in the Hudson River Valley (HRV). The HRV has excellent geographic and floristic qualities to study the influence of climate change on forested ecosystems. Indices of radial growth for three populations per species are developed and correlated against average minimum and maximum monthly temperatures from 1897 to 1994. Only positive correlations to temperature are considered for this analysis. Principal component analysis (PCA) is performed on chronologies over the entire HRV and at four subregions. PCA reveals a strong common signal among populations at subregional and regional scales. January temperatures most limit growth at the ecosystem level, supporting the hypothesis that winter temperatures may control vegetational ecotones. Surprisingly, growth of the oak–hickory ecosystem is most limited by January temperatures only in the southern half of the study region. Chestnut and white oak are the primary species driving the geographic pattern. As winter xylem embolism is a constant factor for ring- porous species, snow cover and its interaction on fine root mortality may be the leading factors of the pattern of temperature sensitivity. Species-specific differences in temperature sensitivity are apparent. Atlantic white-cedar (AWC) and pitch pine are more sensitive to the entire winter season (December–March) while oak and hickory are most sensitive to January temperatures. AWC is most sensitive species to temperature. Chestnut and white oak in the HRV are more sensitive to winter temperature than red oak. Pignut hickory has the most unique response with significant relations to late growing season temperatures. Interestingly, AWC and pitch pine are sensitive to winter temperatures at their NRM while oak and hickory are not. Our results suggest that temperature limitations of growth may be species and phylogenetically specific. They also indicate that the influence of temperature on radial growth at species and ecosystem levels may operate differently at varying geographic scales. If these results apply broadly to other temperate regions, winter temperatures may play an important role in the terrestrial carbon cycle. r 2004 Elsevier GmbH. All rights reserved. Keywords: Temperature sensitivity; Temperate forests; Geographic temperature response; White oak subgenus; Eastern North America; Oak–hickory ecosystem ÃCorresponding author. Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, P.O. Box 1000, 61 Rt. 9W, Palisades, NY 10976, USA. Tel.: +1 845 365 8783; fax: +1 845 365 8152. E-mail address: [email protected] (N. Pederson). 1125-7865/$ - see front matter r 2004 Elsevier GmbH. All rights reserved. doi:10.1016/j.dendro.2004.09.005 ARTICLE IN PRESS 8 N. Pederson et al. / Dendrochronologia 22 (2004) 7–29 Introduction winter temperaturesonly at itsNRM locations( Cook et al., 1998). However, eastern hemlock (Tsuga cana- It hasbeen forecastthat rapid warming over the next densis L.) ispositively correlated to March temperatures 100 years will substantially alter forested ecosystems throughout itsrange in eastern North American ( Cook (Solomon, 1986; Overpeck et al., 1991; Iverson and and Cole, 1991). Two mountain hemlock (Tsuga Prasad, 1998; Bachelet et al., 2001; IPCC, 2001). mertensiana (Bong.) Carr.) populationsat high elevation However, the impact of such warming on ecosystems in Alaska are most strongly and positively correlated to is uncertain because existing information describing the March–July temperatures( Wileset al., 1998 ). In influence of temperature on growth for most tree species contrast, a nearby mountain hemlock population at islacking ( Loehle and LeBlanc, 1996). While tempera- lower elevation has the strongest positive correlation to ture hasbeen shownto be an important factor of tree January–March temperatures( Frank, 1998). An Amer- growth and forest ecosystem dynamics at treeline (e.g. ican beech (Fagus grandifolia Ehrh.) population near its Jacoby and D’Arrigo, 1989; Villalba, 1994; Briffa et al., NRM in eastern Canada is positively correlated to April 2001; Buckley et al., 1997; Kullman, 2001), it isnot as temperatures( Tardif et al., 2001). These studies show well understood in temperate forests. Because northern that each species may have a specific temperature range margins(NRM) representa ‘‘speciestreeline,’’ response, and therefore, a full understanding of poten- NRM are optimum locationsto determine if tempera- tial changes in forested ecosystems as a result of climatic ture limitstree growth in temperate regions.Temperate warming may require the study of many tree species. regions possess some of the largest global aboveground We chose six species to investigate the influence of terrestrial carbon pools (Myneni et al., 2001) while also temperature on the radial growth of NRM species in the directly providing society with goods and services. Hudson River Valley (HRV) (Fig. 1): Atlantic white- Therefore, it iscritical to understandthe influence of cedar (AWC) (Chamaecyparis thyoides (L.) B.S.P.), climate change on tree growth in temperate regions. pitch pine (Pinus rigida Mill.), chestnut oak (Quercus Radial growth studies of NRM populations indicate prinus L.), white oak (Q. alba L.), northern red oak (Q. that temperature may influence individual species rubra L.), and pignut hickory (Carya glabra Mill.). In differently. For example, in the southeastern US loblolly general, these species represent the range of distributions pine (Pinus taeda L.) growth ispositively correlated to for the 30+NRM species in the HRV (Little, 1971). For a b 76 75 74 73 72 LCV 45 d 45 44 44 ADK Hudson GRN River PM GF RH TAC SF GE 43 Gloversville 43 HRV LK Albany PB c NY CAT MP 42 Mohonk 42 N Preserve Port SM West Jervis BV Point ST 41 UB 41 100 km NJ 76 75 74 73 72 Fig. 1. (a) Topographic map centered on eastern New York State and the Hudson Valley. The darker shades represent mountainous areas and are identified by abbreviations: ADK=Adirondack Mountains; GRN=Green Mountains; TAC=Taconic Mountains; CAT=Catskill Mountains. The two main valleys are designated by: HRV=Hudson River Valley and LCV=Lake Champlain Valley. Distribution maps of (b) pitch pine and (c) chestnut oak. (d) Map of population sites and meteorological stations. Tree species are represented by symbols: (~) AWC, (m) pitch pine, (}) chestnut oak, (n) white oak, (J) red oak, and (’) pignut hickory. Site locations are represented by abbreviations. These populations are (north–south): PM=Prospect Mountain, GF=Glen Lake Fen, RH=Rooster Hill, GE=Goose Egg Ridge, SF=Stott Farm, LK=Lisha Kill, PB=Albany Pine Bush, MP=Montgomery Place, SM=Schunnemunk Mountain, BV=Bellvale Mountain, ST=Sterling Forest, and UB=Uttertown Bog. Meteorological stations are in bold italic and represented by (K). The (- - -) represents the average position of the average location of the convergence of winter Arctic and Pacific Frontal Zones(adapted from Bryson et al., 1970). (a) Adapted from Ray Steiner’sColorlandform Atlasof the United States: http://fermi.jhuapl.edu/states/states.html. (b,c) Adapted from Little (1971). ARTICLE IN PRESS N. Pederson et al. / Dendrochronologia 22 (2004) 7–29 9 example, AWC distribution is limited to the southern response of different species have distinct geographic HRV. Distributions of pitch pine, chestnut oak and patterns( Cook and Cole, 1991; Cook et al., 1998; pignut hickory are primarily confined to the HRV with Hofgaard et al., 1999; Gedalof and Smith, 2001; outlier populationsextending into the Lake Champlain Peterson and Peterson, 2001). Therefore, we will Valley (Figs. 1b and c). Northern red and white oak is examine temperature responses at the species and distributed northward through the Champlain Valley ecosystem levels to determine if a geographic pattern and into the St. Lawrence River valley. However, both exists in the HRV. specieshave range marginsalong the edgesof the Adirondack and Green Mountains. Geographic, climatic and floristic qualities of the HRV and surrounding mountains make it an excellent Methods region to study climate change and forested ecosystems. Despite varying objectives and methods, different Region of study geographic studies of vegetation consistently show a distinct boundary at the northern end of the HRV The region of study under investigation is centered on (Bray, 1915; Braun, 1950; Eyre, 1980; Bailey, 1995; the HRV, extending from northern New Jersey to the Lugo et al., 1999). Two recent reconstructions of southern Adirondack Mountains, northwestern Taconic northeastern US vegetation patterns using different Mountains and southern Champlain Valley. The Catskill methodsindicate that thisecotone hasbeen present Mountainsbound the HRV on the westwhile the Taconic since European