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Temporal Changes and Prescribed-Fire Effects on Vegetation and Small-Mammal Communities in Central Appalachian Forest, Creek, and Field Habitats
Karen E. Francl and Christine J. Small

Southeastern Naturalist, Volume 12, Issue 1 (2013): 11–26

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2013 SOUTHEASTERN NATURALIST 12(1):11–26 Temporal Changes and Prescribed-Fire Effects on Vegetation and Small-Mammal Communities in Central Appalachian Forest, Creek, and Field Habitats Karen E. Francl1,* and Christine J. Small1 Abstract - We quantified changes in vegetation and small-mammal communities over a 3-year period in paired creek, forest, and field sites in the central Appalachian Mountains. Prescribed burns were applied to field sites in 2008. Data were collected at all sites during summers of 2008 (pre-burn for fields), 2009 (ca. 2–4 months post-burn for fields), and 2010 (ca. 14–16 months post-burn for fields). In 19,640 trap-nights across 3 years, we captured 605 individuals of 14 small-mammal species. Sørenson index showed substantial differences in mammal communities between 2008 pre-burn and 2009/2010 post-burn fields (<10% similarity for all pre- to post-burn comparisons). Creek and forest habitats showed markedly greater year-to-year similarities (46–82%). Unlike mammals, vegetation and habitat structure showed little change over time. Minimal changes in preand post-burn fields suggest that field vegetation at these sites recovered rapidly after the low-intensity surface fires. In contrast, fire appears to have had a profound effect on small-mammal communities in fields, as documented by dramatic temporal changes in species composition and abundance and little evidence of recovery after 16 months postburn. As many managed fields in this region are burned on 3-year rotations, this potential impact of prescribed fire on small-mammal communities is important. Additional studies are needed to determine whether small-mammal populations are strongly affected by conditions during prescribed burns (i.e., direct effects on species mortality and emigration), or if the changes we observed reflect natural cyclical patterns (annual or multi-annual periodicities) in these populations. Introduction Prescribed fire is a management tool used in a variety of open and forested habitats in the central Appalachian Mountains. Goals of prescribed fire include reduction of surface fuels, regeneration of desirable, fire-tolerant forest species, and maintenance of early successional habitats. Because of the historical application of fire, many extensive oak (Quercus spp.)- and pine (Pinus spp.)-dominated forests in the Appalachians are dependent upon fire for long-term maintenance (Lafon and Hoss 2005). Several short-term studies of birds (e.g., Greenberg et al. 2007) and herpetofauna (e.g., Ford et al. 1999, Kirkland et al. 1996, Russell et al. 1999) have examined the effects of fire in natural habitats of the central and southern Appalachian Mountains. However, the number of studies investigating fire effects on Appalachian small-mammal communities is limited. Ford et al. (1999) found no marked differences in abundances of southern Appalachian 1Biology Department, Radford University, Radford, VA 24142. *Corresponding author - 12 Southeastern Naturalist Vol. 12, No. 1 small-mammal forest species due to prescribed fire, instead attributing preversus post-fire variation to differences in slope. However, Kirkland et al. (1996) discovered that generalist species such as Peromyscus leucopus Rafinesque (White-footed Mouse) were less common in tracts treated with fire than in unburned tracts. Furthermore, arvicoline rodents were noticeably absent in burned treatments (Kirkland et al. 1996). Before European colonization, frequent and widespread fires created and maintained fire-tolerant vegetation types across the Appalachian region (Abrams et al. 1997). While a range of presettlement fire regimes occurred, dendrochronological studies of the George Washington and Jefferson National Forests (GWJNF; western Virginia) indicate that fire in most mixed oak forest stands occurred at ca. 3- to 9-year intervals from the mid-1600s until the 1930s (Abrams et al. 1997, Nowacki and Abrams 2008). Today, prescribed fire is ap - plied, in part, to reestablish these historic intervals, with goals including the restoration of native communities and creation or maintenance of habitats suitable to rare species (USDA Forest Service 2011). In many forested habitats, managers follow a prescribed burn cycle of 4 to 12 years to promote forest health and to keep fuel loads at a manageable level. For grassland habitats managed by the US Forest Service, this burn cycle may be as little as 2 to 3 years to ensure the maintenance of an early-successional state (C. Croy, USFS, Roanoke, VA, pers. comm.). Despite the frequent use of prescribed fire on the GWJNF, most studies of early-successional fire effects in the Appalachian region focus on vegetation and abiotic properties (e.g., Christensen 1976) or on fires in late-successional habitats (Ford et al. 1999). Indeed, no published studies of the effects of fire on small mammals in early-successional habitats of the Appalachian Mountains could be found in recent literature. One possible explanation for lack of studies is that small mammals typically are not a target group by resource managers because many species in the region are generalists that might not respond to habitat alterations (Litvaitis 2001, Mitchell et al. 1997). Given the prevalence of prescribed fire as a management tool in our region, and the scarcity of studies examining fire effects on early-successional small mammals, we investigated short-term (3-year) changes in small-mammal communities following prescribed fire in a central Appalachian early-successional habitat. By examining capture success in pre- and post-burn fields, as well as adjacent unburned creek and hardwood forest sites, we sought to better understand prescribed fire effects and natural short-term variations in vegetation and resident small-mammal communities in common habitats of the central Appalachian Mountains. Methods Site selection Data on small-mammal community composition and capture success were collected over a 3-year period (2008–2010) at the Caldwell Fields complex on 2013 K.E. Francl and C.J. Small 13 the GWJNF (Montgomery County, VA; 37.3370735°N, 80.3256051°W). This site encompasses a number of habitat types, including two fields (6.35-ha Addison Field and 1.95-ha Liatris Field) burned in late February or early March on a 3-year rotation. Each field was bordered by an adjacent creek (Craig Creek) and associated riparian habitat that served as a firebreak for field burns. Mature mixed-hardwood forests occur on east- and west-facing slopes. Some portions of the forest tracts were historically burned in a controlled manner (e.g., forest tract south of Liatris Field burned in 2000). However, the passage of the 2009 Ridge and Valley Act (part of HR146) set aside 1940 ha of Brush Mountain (including both of our forest tracts) as a Wilderness Area, and precluded future use of prescribed fire as a management tool. Studies were conducted immediately before and in the two years after prescribed fire in Addison and Liatris fields. This timing allowed us to examine small-mammal and habitat trends before burning (Year 1: 2008, >2 years postfire), at their most disturbed (Year 2: 2009, ca. 2–4 mo. post-burn), and at a moderate level of disturbance (Year 3: 2010, 14–16 months post-burn). Creek (at the edge of each burn unit) and forest (not burned) sites provided habitat comparisons and allowed us to observe annual fluctuations in small-mammal communities in the absence of fire. Small-mammal surveys At the two field and two forest sites, we established three 100-m transects per site, each with trap stations at 5-m intervals. To reduce trap bias (e.g., Rana 1982), we used a combination of 7.6- x 8.9- x 22.9-cm Sherman live traps (H.B. Sherman, Inc., Tallahassee, FL) and Victor mouse snap-traps (Model #M154, Woodstream Corp., Lititz, PA) placed in visible mammal runways, along logs, or at the bases of shrubs within 1 m of the trapping interval. Additionally, we used six Tomahawk traps (four size #202, two size #207; Tomahawk Live Trap Co., Tomahawk, WI): two per 100-m transect, each separated by at least 25 m. At the two creek sites, we established a line of traps on one (Addison; 300-m transect) or both (Liatris; two 150-m transects) sides of the creek, as restricted by the topography of the site. Traps were baited with rolled oats and peanut butter (Shermans), sardines (snap traps), or canned dog food and a variety of fruits and vegetables (Tomahawks). Although we acknowledge that the addition of pitfall traps may have further limited trap bias (e.g., Francl et al. 2002, Mengak and Guynn 1987), time and state permitting limitations did not allow for the use of this additional technique. We set traps for four consecutive nights in late May and again in early July of 2008, 2009, and 2010. Each site contained a total of 6 Tomahawks, 60 Shermans, and 60 snap-traps, which were checked twice daily—morning and late afternoon. All live small mammals captured were sexed, aged (juvenile vs. adult), measured (total length, tail length, hind foot length, ear length) to assist with species identification, weighed, marked with an ear clip to determine recapture rates, and released. 14 Southeastern Naturalist Vol. 12, No. 1 Some Peromyscus individuals did not clearly fall into the length categories and visual descriptions of P. maniculatus Wagner (Deer Mouse) or P. leucopus and were treated as Peromyscus sp. in statistical analyses (Linzey 1998). Larger mammals (>1 kg) in Tomahawks were sexed, weighed, and released. Deceased mammals were identified, measured, and subsequently frozen. Some have been prepared as voucher specimens and deposited in the Radford University Department of Biology’s natural history collection. For statistical analyses, we converted species capture numbers to capture per trap night as an index of relative abundance. Because preliminary analyses found no differences in capture success between trapping bouts within a yea r (May vs. July), we combined capture effort to focus on differences among years. Further, because no discernible biases were discovered in preliminary analyses of temperature, moon phase, and rainfall (monthly or annual), we did not examine these metrics further. All trapping was completed in compliance with the Radford University Animal Care and Use Committee (Francl, #FY08-013), within the guidelines of Virginia scientific collecting permits (Francl, # 031159 and 035794), and with written permission from the USDA Forest Service, Eastern Divide Ranger District. Habitat surveys To characterize vegetation composition and habitat structure, we established one 400-m2 plot at each site. Field and forest plots were 20 x 20 m; creek plots were 10 x 40 m, with the longest plot dimension parallel to the creek edge to maintain habitat homogeneity within the plot. All plots were immediately adjacent to or within small-mammal trapping grids. Because plot corners were not permanently fixed, some degree of year-to-year variation in plot location (± 10 m) occurred at each study site. In each plot, percentage ground area covered by each vascular plant species was estimated using standard cover classes (<1, 1–2, 2–5, 5–10, 10–25, 25–50, 50–75, 75–100%; VA DCR-DNH 2011). In addition, we estimated total cover per plot for bryophytes/ lichen and surface-substrate categories (bedrock, mineral soil, water, decaying wood, leaf litter, other). Basal area and stem density were determined for each woody species reaching or exceeding breast height (1.37 m) in each plot. Additional plot measures included: number of snags (dead upright trees >10 cm diameter at breast height [DBH]); number of logs (dead, downed trees >2 m long, >10 cm diameter); light (5 replicate measures of photosynthetically active radiation [PAR]; LI-250A quantum sensor light meter, LI-COR, Lincoln, NE); tree canopy cover (concave spherical densiometer, following corrected procedure of Strickler [1959]: % tree canopy cover = [(sum of cover estimates at cardinal compass directions) x 1.5)] - 1); soil moisture (4 replicate measures; Kel Instruments, Inc., Wyckoff, NJ); leaflitter depth (4 replicate measures); elevation; slope steepness; and topographic aspect. Twenty replicate range-pole measurements were taken in each plot 2013 K.E. Francl and C.J. Small 15 to calculate the Levins index of vertical diversity (Levins 1968) and total vegetation volume (Mills et al. 1989). Composite soil samples from the Ahorizon (upper 10 cm) were collected from each plot and used in laboratory determinations of soil pH (glass-electrode method) and percent organic matter (dry-ash method; Shepard et al. 1993). Habitat surveys were conducted in early July 2008, 2009, and 2010. Statistical analyses Vegetation and small-mammal capture data were compared across our six sites and three sample years using global Non-Metric Multidimensional Scaling (NMS) ordination, with Sørenson distance (Magurran 2004, McCune and Grace 2002). NMS ordination has been shown to perform well with ecological data, which tend to be non-normal and contain numerous zero entries (Mc- Cune and Grace 2002). Separate ordinations were performed for vegetation and small-mammal data. Following ordination analysis, Pearson productmoment correlations of habitat variables and NMS axis scores were calculated to identify habitat conditions most strongly correlated with small-mammal capture success. To test for changes in small-mammal and vegetation communities across sites and years, we used blocked multi-response permutation procedure (MRPP). This non-parametric, multivariate analysis tests for significant differences in species composition between samples (McCune and Grace 2002). Sørenson was used as the distance measure for consistency with NMS ordination analyses. All multivariate analyses were conducted using PC-ORD for Windows (ver. 5.14; MjM Software, Gleneden Beach, OR). Results Mammal surveys In 18,144 trapnights across 3 years, we trapped 605 individuals of 14 mammal species (12 species in 2008, 9 in 2009, 9 in 2010; Table 1). Mammal trap success by year was 4.3% in 2008, 2.7% in 2009, and 1.9% in 2010, including recaptures. Two species of Peromyscus, White-footed Mouse (25.6% of all captures) and Deer Mouse (24.8% of all captures), dominated captures across all years. Sigmodon hispidus Say and Ord (Hispid Cotton Rat), captured in 2008 in Addison Field, was a new county record (Francl and Meikle 2009). Small-mammal communities differed markedly across habitats, particularly in fields. In our initial sample year (2008), mammal captures in fields were ≤10% similar to creeks or forests (Sørenson index; Table 2). Mammal captures in creek and forest habitats showed much greater compositional similarity (>50% similarity) in 2008 (Table 2). Ordination analysis of small-mammal captures was best fit by a two-axis solution, based on a NMS scree plot and Monte Carlo randomization test (P < 0.05, final stress = 26.63, final instability = 0.05, 500 iterations). These NMS axes accounted for 84.5% of the variability in the data (Axis 1 = 16 Southeastern Naturalist Vol. 12, No. 1 Table 1. Capture metrics (captures per trapnight and species richness) for small mammals at Caldwell Fields complex, VA over a three-year study. Within the complex, Addison and Liatris sites each included a field, an adjacent creek, and upland forest. The two field sites had prescribed burns between the 2008 and 2009 trapping efforts. Creek Field Forest Location/Order Family Scientific name 2008 2009 2010 2008 2009 2010 2008 2009 2010 Addison Didelphimorphia Didelphidae Didelphis virginiana 0.001 0.002 - - - - - 0.002 - Insectivora Soricidae Blarina brevicauda - 0.002 0.004 0.004 0.002 0.004 - 0.002 0.001 Insectivora Soricidae Cryptotis parva - - - 0.003 - - - - - Rodentia Cricetidae Microtus pennsylvanicus - - - 0.095 0.002 0.001 - - - Rodentia Cricetidae Peromyscus leucopus 0.022 0.017 0.012 0.002 0.001 - 0.012 0.006 0.002 Rodentia Cricetidae Permyscus maniculatus 0.010 0.015 0.023 0.004 - - 0.004 0.007 0.003 Rodentia Cricetidae Peromyscus sp. 0.015 0.003 0.002 0.001 - - 0.002 0.002 0.001 Rodentia Cricetidae Sigmodon hispidus - - - 0.006 - - - - - Rodentia Cricetidae Synaptomys cooperi - 0.001 - 0.013 - - - - - Rodentia Sciuridae Glaucomys volans - - - - - - - - 0.001 Rodentia Sciuridae Tamias striatus 0.001 - - - 0.001 - - - - Rodentia Cricetidae Zapus hudsonius - 0.002 - - 0.005 - - - - Carnivora Mephitidae Mephitis mephitis - - - - - 0.002 - - - Carnivora Procyonidae Procyon lotor - 0.001 - - - - - - - Lagomorpha Leporidae Sylvilagus floridanus - - - 0.001 - - - - - Species richness 4 7 3 8 5 3 2 4 4 Liatris Didelphimorphia Didelphidae Didelphis virginiana - - - - - - 0.001 - - Insectivora Soricidae Blarina brevicauda - 0.003 - 0.001 - - - 0.001 0.002 Insectivora Soricidae Cryptotis parva - - - - - - - - - Rodentia Cricetidae Microtus pennsylvanicus - - - 0.039 0.002 0.002 - - - Rodentia Cricetidae Peromyscus leucopus 0.020 0.017 0.011 0.001 0.006 - 0.013 0.009 0.004 Rodentia Cricetidae Permyscus maniculatus 0.008 0.022 0.023 0.002 0.003 - 0.005 0.013 0.007 Rodentia Cricetidae Peromyscus sp. 0.008 0.005 0.002 - - - 0.012 0.003 0.004 Rodentia Cricetidae Sigmodon hispidus - - - - - - - - - Rodentia Cricetidae Synaptomys cooperi - - - - - - - - - Rodentia Sciuridae Glaucomys volans - - - - - - - - - Rodentia Sciuridae Tamias striatus - - 0.001 - 0.001 - 0.002 0.004 0.003 Rodentia Cricetidae Zapus hudsonius 0.001 - - 0.002 0.001 0.001 - - - Carnivora Mephitidae Mephitis mephitis - - - - - - - - - Carnivora Procyonidae Procyon lotor 0.001 0.001 - - - - - 0.001 - Lagomorpha Leporidae Sylvilagus floridanus - - - - - 0.001 - - - Species richness 4 4 3 5 5 3 4 5 4 2013 K.E. Francl and C.J. Small 17 Table 2. Sørenson similarity (%) for small-mammal captures at Addison (AD) and Liatris (LI) field, creek, and forest sites throughout the three-year study period. Underlined values are discussed in text. (See Methods f or complete description of sampling design.) 2008 2009 2010 AD LI AD LI AD LI Field Creek Forest Field Creek Forest Field Creek Forest Field Creek Forest Field Creek Forest Field Creek Forest Year 2008 AD Field 100.0 8.3 9.9 49.4 8.7 9.1 7.0 12.0 12.6 9.9 11.7 10.4 7.2 13.3 10.0 4.4 8.9 12.5 AD Creek 100.0 53.0 6.7 83.7 77.2 6.6 67.7 46.6 31.9 66.2 58.0 0.0 53.7 20.8 0.0 56.2 46.0 AD Forest 100.0 10.0 62.4 70.3 6.9 58.8 66.2 58.2 54.4 62.7 0.0 60.5 46.3 0.0 62.7 54.5 LI Field 100.0 10.0 8.1 21.8 14.1 13.2 21.1 9.1 10.9 7.8 9.8 15.6 12.0 7.7 13.0 LI Creek 100.0 73.5 8.2 74.2 51.3 38.1 72.1 61.1 0.0 56.0 25.3 4.6 56.3 50.4 LI Forest 100.0 9.1 58.4 55.3 43.4 57.1 60.8 0.0 52.2 29.2 0.0 55.2 58.3 Year 2009 AD Field 100.0 18.5 20.0 41.7 10.2 14.3 33.3 11.5 21.1 40.0 8.3 25.8 AD Creek 100.0 61.3 35.7 83.5 73.0 8.0 73.8 27.5 4.3 70.0 50.8 AD Forest 100.0 56.3 50.7 64.0 15.4 56.7 51.9 0.0 53.6 76.9 LI Field 100.0 29.5 45.5 10.0 33.3 47.6 35.3 40.0 48.5 LI Creek 100.0 68.4 10.9 87.6 25.0 0.0 82.4 50.0 LI Forest 100.0 5.3 69.4 35.9 0.0 73.5 70.6 Year 2010 AD Field 100.0 16.7 13.3 18.2 0.0 14.8 AD Creek 100.0 28.6 0.0 92.3 49.2 AD Forest 100.0 0.0 26.7 50.0 LI Field 100.0 0.0 0.0 LI Creek 100.0 49.1 LI Forest 100.0 18 Southeastern Naturalist Vol. 12, No. 1 39.4%, Axis 2 = 45.1%). Again, mammal captures in field sites appeared most distinct, separating out low on NMS Axes 1 and 2 (Fig. 1A) and negatively correlated with light availability (Axis 1 r = -0.73, Axis 2 r = -0.66). Captures in 2013 K.E. Francl and C.J. Small 19 forest and creek sites showed much greater similarity and were arranged high on NMS Axes 1 and 2. These were positively correlated with tree canopy cover (Axis 1 r = 0.75, Axis 2 r = 0.70) and shrub cover (Axis 1 r = 0.47, Axis 2 r = 0.65). Soil moisture also was positively correlated with Axis 1 (r = 0.64). Mammal species differed considerably in their habitat preferences. Across all years, Peromyscus species showed similar habitat preferences, based on NMS ordination results (Fig. 1B). Deer Mice (Axis 1 r = 0.61, Axis 2 r = 0.38) and Whitefooted Mice (Axis 1 r = 0.76, Axis 2 r = 0.50) were positively correlated with Axes 1 and 2, indicating greater capture success at creek sites. We captured Tamias striatus L. (Eastern Chipmunk) only in forests (Axis 1 r = 0.21, Axis 2 r = 0.26). Didelphis virginiana Kerr (Virginia Opossum; Axis 1 r = 0.28, Axis 2 r = 0.28) and Procyon lotor L. (Raccoon; Axis 1 r = 0.41, Axis 2 r = 0.25) were captured at both forest and creek sites (Fig. 1B). Microtus pennsylvanicus Ord (Meadow Vole; Axis 1 r = -0.72), Sylvilagus floridanus J.A. Allen (Eastern Cottontail; Axis 1 r = -0.58), and Zapus hudsonius Zimmermann (Meadow Jumping Mouse; Axis 1 r = -0.54) all were negatively correlated with Axes 1 and 2, with higher capture success in fields. Blarina brevicauda Say (Northern Short-tailed Shrew; Axis 1 r = -0.15, Axis 2 r = -0.22) was ubiquitous across habitat types. In examining year-to-year variations in mammal communities, we found that fields showed considerable declines in small-mammal captures over time, whereas capture rates in creeks and forests were relatively constant (Table 1). Results of MRPP analysis emphasized this marked change in field mammals over time (within group distance = 272.4–654.4) and lesser changes in creek (134.5–152.8) and forest (75.9–108.0) habitats (Table 3). Sørenson values for fields were extremely low across years, especially when comparing 2008 (preburn) mammal communities to post-burn years (all 7–21% similarity; Table 2). Two species (Hispid Cotton Rat and Least Shrew [Cryptotis parva Say]) were Figure 1 (opposite page). NMS ordination of small-mammal capture data at Liatris (LI) and Addison (AD) study sites (field = FI, creek = CK, forest = FO). Each site was sampled in 2008, 2009, 2010. A) Vectors indicate the strength and direction of Pearson product-moment correlations between plots and habitat variables. Vectors: trees = mean relative basal area and density; canopy = tree canopy cover; topographic position = visual characterization of topography position (1 = crest, 2 = upper slope, 3 = middle slope, 4 = lower slope, 5 = toe slope, 6 = floodplain or level bottom, 7 = basin or depression; categories follow VA DCR-DNH [2011]). (See Table 4 and text for remaining variable definitions and field methods.) B) Locations of species maxima on the ordination, based on abundance at each study site and sample year. Species abbreviations: BLBR= Blarina brevicauda, CRPA= Cryptotis parva, DIVI= Didelphis virginiana, GLVO= Glaucomys volans L. (Southern Flying Squirrel), MEME= Mephitis mephitis Schreber (Striped Skunk), MIPE= Microtus pennsylvanicus, PEsp= Peromyscus leucopus/maniculatus (unknown), PELE= Peromyscus leucopus, PEMA= Peromyscus maniculatus, PRLO= Procyon lotor, SIHI= Sigmodon hispidus, SYCO= Synaptomys cooperi Baird (Southern Bog Lemming), SYFL= Sylvilagus floridanus, TAST= Tamias striatus, ZAHU= Zapus hudsonius. C) Vectors connect annual observations for each study site, illustrating magnitude and direction of change in mammal communities from 2008 to 2010. 20 Southeastern Naturalist Vol. 12, No. 1 captured solely in Addison Field in 2008. Although similarity remained relatively low, field mammals showed much greater similarity in 2009 vs. 2010 post-burn samples (33–35% similarity), (Table 2). Ordination analysis also emphasized the dramatic compositional shift in pre- to post-burn mammals (2008 vs. 2009 and 2010 fields; Fig. 1C). In contrast, forest (46–71% similarity) and creek (53–82% similarity) sites showed relatively little change in mammal captures across our three years of sampling (Table 2, Fig. 1C). Habitat surveys Unlike small-mammal communities, vegetation showed little change over time, regardless of habitat type. Our three habitat types were widely separated on the vegetation ordination (two-axis solution, final stress = 5.68, final instability = less than 0.00001, 59 iterations), indicating marked compositional differences, particularly in fields. However, within-habitat variation was minimal (Fig. 2). Each habitat/study site showed tight clustering of 2008, 2009, 2010 samples, indicating little year-to-year variation. Most compositional variation was explained by ordination Axis 2 (65.6%). Axis 2 was positively correlated with Figure 2. NMS ordination of vegetation data at Liatris (LI) and Addison (AD) study sites (field = FI, creek = CK, forest = FO). Each site was sampled in 2008, 2009, and 2010. Vectors connect annual observations for each study site, illustrating magnitude and direction of vegetation change from 2008 to 2010. (See text for complete description of habitat variables and sampling methodology). 2013 K.E. Francl and C.J. Small 21 light (r = 0.77) and herbaceous cover (r = 0.66), which reached greatest abundance in fields, and negatively correlated with tree cover (r = -0.85), shrub (r = -0.69) cover, and density of logs (r = -0.81) and snags (r = -0.80), factors greatest in our tree-dominated creek and forest sites. Axis 1 accounted for 22.3% of the variation in vegetation data and was strongly correlated with moisture (r = 0.94; greatest in creek sites). Table 3. Multi-response permutation procedure (MRPP) analysis of changes in small-mammal and vegetation communities from 2008 to 2010 at Addison and Liatris study sites. Values represent average within-group Euclidean distance. Mammals were trapped along three 100-m transects at each site, with trap stations at 5-m intervals, using a combination of Sherman live traps and Victor mouse snap-traps. Vegetation data were collected in one 400-m2 plot adjacent to or within small-mammal trapping grids in each habitat. (See Methods section for a complete description of sampling design.) Field Creek Forest Addison Liatris Addison Liatris Addison Liatris Small mammals 654.4 272.4 152.8 134.5 75.9 108.0 Vegetation 2.5 3.7 15.4 9.2 11.8 9.3 Table 4. Habitat variables measured in one 400-m2 plot adjacent to or within small-mammal trapping grids at Addison and Liatris study sites. Values represent means ± standard error of 2008, 2009, and 2010 data. Only variables significantly correlated with NMS ordination of small-mammal captures (Fig. 1) shown. See text for variable definitions a nd field methods. Field Creek Forest Addison Liatris Addison Liatris Addison Liatris Tree basal area (m2/400-m2 plot) 0.00 0.00 1.06 0.91 0.79 0.70 (0.00) (0.00) (0.20) (0.44) (0.08) (0.05) Tree density (stems/400-m2 plot) 0.00 1.33 168.00 18.67 125.67 98.33 (0.00) (1.33) (59.01) (6.69) (7.80) (26.03) Tree canopy cover (%) 0.50 4.40 96.07 86.73 73.97 81.83 (0.50) (4.40) (1.97) (5.87) (15.78) (6.85) Shrub cover (%) 2.17 5.50 13.83 14.00 22.00 43.33 (0.67) (0.58) (2.33) (1.32) (1.89) (5.67) Herbaceous cover (%) 100.00 100.00 85.67 100.00 34.83 33.67 (0.00) (0.00) (7.84) (0.00) (5.25) (3.83) Light (μmol/sec/m2) 1027.78 1203.39 19.00 66.43 37.97 204.35 (93.34) (81.13) (4.40) (13.28) (3.50) (276.85) Soil moisture (%) 37.67 40.40 32.92 36.32 14.17 7.75 (5.63) (7.52) (6.36) (7.83) (5.56) (3.06) Snag density (#/plot) 0.00 0.00 1.00 0.67 3.67 4.00 (0.00) (0.00) (0.58) (0.33) (1.20) (0.00) Log density (#/plot) 0.00 0.33 2.33 2.33 9.67 6.67 (0.00) (0.33) (0.88) (0.88) (1.20) (2.03) 22 Southeastern Naturalist Vol. 12, No. 1 Results of MRPP analyses emphasized the lack of vegetation change over time (MRPP within group distance = 2.5–15.4), as compared to small mammal communities (Table 3). This stability was expected in forest and creek habitats, as these are dominated by long-lived trees and thus maintain relatively constant composition and structure. These sites were heavily wooded with high tree density, basal area, and canopy cover (Table 4). Forests generally had greater density of snags and logs; creeks had higher herbaceous cover (comparable to fields). Field habitats remained open, with high light, dense herbaceous cover, and few trees or shrubs (Table 4). Snags and downed logs were virtually absent. However, given the 2008 prescribed burns and pronounced changes in field mammals over time, the lack of temporal change in field vegetation (average within-group distance = 2.5–3.7; Table 3) was a strong contrast. Discussion Perhaps the most notable finding at the Caldwell Fields complex was the stark difference in fire response by mammal and vegetation communities. Whereas mammals exhibited precipitous declines in capture success and species richness, vegetation showed markedly little change over our three-year study. Both ordination (Fig. 1) and MRPP (Table 2) analyses highlighted the dramatic changes in small-mammal communities over time (within-group distance for small mammals, all habitat types = 233.0 ± 88.6). These temporal changes were particularly pronounced in field sites (463.4 ± 191.0). In contrast, we found relative stability of vegetation and habitat structure at each site (within-group distance for all vegetation types = 8.7 ± 2.0). Least compositional change was observed in field sites, despite prescribed burns (Table 2, Fig. 2). As our field sites were dominated by a mixture of early-successional species, including many fire-tolerant perennial grasses and forbs, it is not surprising that field vegetation recovered quickly after prescribed fires. As in other eastern North American natural areas where fire is used to maintain open grassland conditions and control invasion of woody plants (e.g., Christensen 1976), fire appeared to have little detrimental effect on herbaceous plants at our site. Based on other studies, we predicted highest small-mammal capture rates in fields prior to burning, lowest immediately after burning, and recovery to near pre-burn levels within 1–2 years. Due to the absence of fire, we expected considerably less year-to-year variation in adjacent creek and forest sites. The mammalian species richness declines that we observed in the short-term were similar to a Utah study of Artemisia tridentata Nutt. (Big Sagebrush ) community. McGee (1982) found that small-mammal species richness declined slightly post-fire but returned to pre-burn levels after three years. In this Utah study, however, total mammalian abundance significantly increased in the first two years post-burn, partly because of a dramatic increase in captures (presumably also an increase in abundance) of Deer Mice, a species also present in our study. Studies in Midwestern tallgrass prairies and western grassland systems also reported generally high survival rates for Deer Mice and White-footed Mice following fire, and increased abundance during the next growing season 2013 K.E. Francl and C.J. Small 23 relative to pre-burn and unburned sites. Population increases were attributed to their rapid colonization ability and reduced litter depth and increased food supplies for Peromyscus spp. after fire (Kaufman et al. 1990, Sullivan 1995). In our study, however, both Deer Mice and White-footed Mice were uncommon in the field sites across all years, and both populations appeared stable and abundant in the creek and forest sites. Both forest sites showed declines in mammal capture success from 2009 to 2010, but these declines were of lesser magnitude than in our fields and were not evident from 2008 to 2009. In addition, year-to-year variation in mammal composition (based on Euclidean distance) was minimal in creek and especially forest sites, as compared to fields (Table 3). However, it is possible that our trapping techniques (lack of pitfall traps) underestimated soricid community’s response to fire. We cannot eliminate the possibility that mammalian communities varied not only because of the prescribed fire, but also because of natural cyclical patterns. Other studies have shown that Deer Mice, White-footed Mice, and Hispid Cotton Rats all exhibit annual or multi-annual periodicities (Brady and Slade 2004, Langley and Shure 1988, Rehmeier et al. 2005). Despite our preliminary analyses indicating that yearly or monthly rainfall was not correlated with capture success, unmeasured climatological metrics may have altered resource availability (e.g., food, nesting sites) for small mammals (Langley and Shure 1988, Rehmeier et al. 2005). However, if the observed variations were linked to climate patterns and natural population cycles, we should expect comparable declines at our forest and (potentially) creek sites. All of our habitats showed marked changes in mammal captures over time, yet none were as dramatic as our field sites. It is important to note, however, that eastern forests typically show little response to small-scale moisture variations (Small and McCarthy 2002). High canopy cover and moisture availability at our creek sites would contribute greatly to droughtresilience. Our forest sites, on the other hand, were significantly drier than other habitats (Table 4), dominated by relatively drought-tolerant oak- and heathdominated communities. Our study provides evidence that small-mammal communities in central Appalachian grasslands are responding to prescribed fire in the short-term, while habitat conditions remain remarkably unchanged. Lack of variati on in field vegetation from pre- to post-burn years suggests that plant species in these habitats are tolerant of low-intensity surface fire. In contrast, the small-mammal communities of Caldwell Fields complex showed marked change, without recovery 16 months post-burn (despite little change in habitat structure). As many managed fields in this region are burned on 3-year rotations, this potential impact of prescribed fire on small-mammal communities is important. Additional studies are needed to determine whether small-mammal populations show pronounced response to conditions occurring during prescribed burns (i.e., direct effects on species mortality and emigration), or if the changes we observed reflect natural cyclical patterns (annual or multi-annual periodicities) in these populations, as reported for selected small-mammal populations in other regions . 24 Southeastern Naturalist Vol. 12, No. 1 Due to the brevity of our project, the long-term implications still are unknown. We suggest that surveys like these be expanded to investigate the effects on mammals in other burned grasslands on the George Washington and Jefferson National Forests. A larger-scale small-mammal surveying effort would allow investigators to capture multiple fields at different stages of postfire succession. The time between burns also could be investigated as a factor in small-mammal recovery. Because of the failure for small-mammal communities to recover 16 months post-burn, we suggest that care be taken in burning early-successional habitats. It is likely that an additional year between burns (4-year rotation) at Caldwell Fields could allow for sufficient recovery time for small-mammal populations, yet still maintain an early-successional habitat. In cases where previous smallmammal surveys have revealed the presence of rare species or species of concern, the details (season, frequency) of the burn should be planned with this species’ natural history characteristics in mind. Acknowledgments We thank C. Croy, S. Croy, and J. Overcash of the USDA Forest Service for assistance with site selection and GIS mapping components. We also thank numerous student technicians who assisted with field work and lab analyses: M. Baisey, R.C. Bland, M. Brennan, E. Burnett, T. Canniff, K. Creange, S. Demeo, C. Faidley, G. Good, J. Lucas, D. Mathews, D. Meikle, B. Meyer, A. 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