INFLUENCE OF ELEVATION AND FOREST TYPE ON COMMUNITY ASSEMBLAGE AND SPECIES DISTRIBUTION OF SHREWS IN THETHE CECEN-N- TRAL AND SOUTHERN APPALACHIAN MOUNTAINS W. M ARK FORD , T IMOTHY S. M CCAY , M ICHAEL A. M ENZEL , W. D AVID WEBSTER , C ATHRYN H. G REENBERG , J OHN F. P AGELS , AND JOSEPH F. M ERRITT ABSTRACT We analyzed shrew community data from anced assemblage of size classes less than expected. 398,832 pitfall trapnights at 303 sites across the up- Among individual species, presence of masked per Piedmont, Blue Ridge, northern Ridge and Val- shrew ( Sorex cinereus ) and smoky shrew ( Sorex fumeus ) ley, southern Ridge and Valley, Cumberland Plateau was associated strongly with increasing elevation and Allegheny Mountains and Plateau sections of and mesic forests, whereas presence of southeastern the central and southern Appalachian Mountains shrew ( Sorex longirostris ) and southern short-tailed from Alabama to Pennsylvania. The objectives of shrew ( Blarina carolinensis ) showed an opposite trend our research were to describe regional species dis- with elevation and forest type. The strong relation- tributions and to identify macro-environmental fac- ships we documented between presence of these tors important to shrews at both the community four species with elevation and forest type facili- and individual species scales. Our study docu- tated reliable predictive habitat modeling. Con- mented the presence of nine species with a low of versely, the presence of pygmy shrew ( Sorex hoyi ) three in the southern Ridge and Valley section to a and northern short-tailed shrew ( Blarina brevicauda ) high of eight in the Blue Ridge section where the was not linked to forest type and only weakly linked Appalachian, Austral and Boreomontane fauna ele- to increasing elevation. Our analyses failed to pro- ments converge. Region-wide, shrew species rich- duce meaningful relationships about extreme habitat ness was related to increasing elevation and was specialists documented by our survey, the rock higher in mesic forest types than in xeric types. shrew ( Sorex dispar ) associated with colluvial talus, Conformity to expected distribution of shrew body- the water shrew ( Sorex palustris ) associated with size (small, medium and large) appropriate for the high-gradient streams, and the least shrew ( Cryptotis central and southern Appalachian species pool parva ) associated with oldfields and early sucessional showed no relationship to elevation gradients. habitats. However, xeric forest types conformed to a bal- INTRODUCTION Within the central and southern Appalachian Appalachians to support a rich shrew community Mountains of the southeastern and mid-Atlantic within local landscapes (i.e., > 2,000 ha). However, United States, the family Soricidae is represented by many of these species with sympatric regional dis- 9 species of shrews (Kirkland and Snoddy 1999; tributions often are not syntopic. Strong local seg- Laerm et al. 1999). The Appalachian Mountains regation occurs between similar species, such as the provide an extension of the Boreomontane and masked shrew ( Sorex cinereus ) and the southeastern Appalachian faunal elements into a region with Aus- shrew ( Sorex longirostris ; Pagels and Handley 1989; tral affinities (Choate et al. 1994). Superficially, var- Ford et al. 2001). In part, this is a function of the ied topography that produces considerable habitat varied habitat preferences among shrew species heterogeneity and the high elevations that provide (Laerm et al. 1999) as well as differences in body cool and moist climatic regimes are two comple- size that contribute to fairly predictable species as- mentary factors that enable the central and southern semblages and local distributions (Fox and Kirkland 303 304 SPECIAL PUBLICATION OF THE INTERNATIONAL SOCIETY OF SHREW BIOLOGISTS NO. 01 1992; Shvarts and Demin 1994; Churchfield et al. sights in defining and conserving functioning mon- 1999). Nonetheless, the factors that explain pres- tane boreal or northern hardwood forest communi- ence of individual shrew species at the micro- or ties that currently exist as isolated relicts (Ford et al. macro-habitat or even landscape distribution scales 1994). Presence of water shrews ( Sorex palustris ) in the central and southern Appalachian Mountains may be indicative of high water quality that merits have not been quantified. extraordinary riparian zone protection in the central and southern Appalachian Mountains (Pagels et al. Seven of the nine shrew species that occur in 1998), whereas presence of the rock shrew ( Sorex the central and southern Appalachian Mountains are dispar listed as sensitive or species of concern in one or ) probably are indicative of talus and rock out- crop habitats that support two rodents of very high more states in the region (Laerm et al. 2000a). conservation concern, the Allegheny woodrat Therefore, the ability to understand the environ- (Neotoma magister ) and the rock vole ( Microtus chrotor- mental factors responsible for distributional pat- rhinus terns of presence and absence within a shrew spe- ). Accordingly, the objectives of our study were to: 1) examine the influence of elevation and cies’ distribution is critical from a conservation forest type on shrew species richness and distribu- viewpoint. Because most shrews are cryptic ani- mals that are difficult to survey without time- and tion of shrew species in the central and southern labor-intensive pitfall trapping (Kirkland and Appalachian Mountains; 2) examine the influence of Sheppard 1994; Ford et al. 1997), developing easily elevation and forest type on maintaining conformity quantifiable habitat parameters to accurately predict to equitable function groups of shrews as delineated species presence would be useful in conservation by current species-assembly rules for shrews in the planning and biodiversity management. For exam- eastern United States; and 3) explore the utility of ple, knowledge of masked shrew distribution in the modeling shrew species distribution across the cen- southernmost Blue Ridge section could provide in- tral and southern Appalachian Mountains. METHODS We assembled survey data from pitfall collec- rigue 2001; Merritt et al. 2001;Keyser et al. 2001). tions from 303 sites over 398,832 trapnights in the The majority of these collections were obtained central and southern Appalachian Mountains in the from pitfall trapping using 943 cm 3 plastic cups or upper Piedmont, Blue Ridge, northern Ridge and #10 tin cans set in transects along natural cover Valley, southern Ridge and Valley, Allegheny Moun- such as coarse woody debris or boulders or associ- tains and Plateau and Cumberland Plateau sections ated with aluminum drift-fences. Pitfall trapping from northeastern Alabama to southwestern Penn- methods are described in detail by Ford et al (1994), sylvania (Figure 1). Our collection data emanated Pagels et al. (1994) and McCay et al. (1998). from several ecological studies and unpublished For each pitfall collection site, we determined survey efforts that were undertaken by the Univer- Appalachian physiographic section, elevation, forest sity of Georgia, the USDA Forest Service, the Uni- type, species presence and richness. Collection site versity of North Carolina at Wilmington, Virginia elevations ranged from 160 m in the upper Pied- Commonwealth University, Marshall University, mont to approximately 1,600 m in the Blue Ridge. Kentucky Nature Preserves Commission and Pow- Most sites were located in mature, second-growth dermill Biological Station from 1979-2000 (Caldwell forest stands that originated from forest harvesting 1980; Cawthorn 1994; Ford et al. 1994; Laerm et al. or farm abandonment during 1880-1930 (Ford et al. 1994; Pagels et al. 1994; Hajenga 1995; Laerm et al. 1994; Ford et al. 2000b). However, some collec- 1995a; Laerm et al. 1995b; Laerm et al. 1995c; tions were from younger-aged forest stands (15-50 Laerm et al. 1996a; Laerm et al. 1996b; Ford et al. years-old) or unharvested old-growth (Ford et al. 1997; Laerm et al. 1997; Ford et al. 1999; Laerm et 1997). We characterized each collection site as al. 1999; Menzel et al. 1999; Ford et al. 2000a; mesic or xeric forest type. Mesic forest communi- Laerm et al. 2000b; Ford et al. 2001; Ford and Rod- 2005 FORD ET AL. – SHREW COMMUNITY ASSEMBLAGES 305 ties were located at either high elevations or in areas with favorable site conditions, such as sheltered PA north-facing slopes and ravines, whereas xeric for- 5 ests usually were located at either low- to mid- MD elevations or in exposed aspects and unsheltered 3 landforms. Mesic forests included red spruce ( Picea rubens )-dominated forests or northern hardwood WV 1 communities dominated by American beech ( Fagus grandifolia ), yellow birch ( Betula alleghaniensis ), sugar 5 3 VA maple ( Acer saccarhum ) and black cherry ( Prunus serot- KY ina ) at the highest elevations, cove hardwood forests 2 dominated by yellow poplar ( Liriodendron tulipifera ), basswood ( Tilia americana ) and northern red oak 6 1 4 (Quercus rubra ) on north-facing slopes and ravines; 6 NC and eastern hemlock ( Tsuga canadensis )-white pine 2 TN (Pinus strobus )-dominated montane riparian areas along very sheltered, high-gradient streams (Ford et SC al. 2000a; Ford et al 200b; Ford and Rodrigue 2001). 2 Xeric forest communities included upland hard- AL 6 4 1 wood forests dominated by several oak ( Quercus ) GA and hickory ( Carya ) species, red maple ( Acer rubra ) and blackgum ( Nyssa sylvatica ); mixed pine ( Pinus )-