Cathryn H. Greenberg

Forest disturbance in hurricane-related downbursts in the Appalachian mountains of North Carolina

Abstract We characterized five 0.2–1.1 ha gaps created by downbursts during Hurricane Opal in xeric oak forest at the Bent Creek Experimental Forest, Asheville, NC. Direction of windthrow was nonrandom in four of the five gaps, but differed among gaps suggesting that each was caused by an independent downburst. Windthrows reduced tree density by 19–39% and basal area (BA) by 30–53% within gaps. Most windthrows were uprooted (17–38% of all trees) versus broken below 1.8 m height (0–3%). Most species were uprooted in proportion to their abundance regardless of canopy position. Red oaks (Quercus coccinea, Quercus rubra and Quercus velutina) were disproportionately uprooted, while Nyssa sylvatica and Acer rubrum were resistant to uprooting. As a group, Quercus lost 27–47% of individuals and 41–50% of BA. Q. coccinea lost ≥44% of trees and >55% of BA in sites where it occurred. Only minor shifts in canopy species dominance were evident. For several species, significantly more large-diameter individuals uprooted than their smaller counterparts. No relationship between dbh and number uprooted was detected for the red oaks, however. Canopy position appeared to have little bearing on this relationship. Uprooting disturbed 1.6–4.3% of the ground area and displaced 130–587 m3 of root–soil–rock masses (rootmasses) per gap. We suggest that episodic, high-intensity wind is not uncommon, and has a substantial influence on forest structure, species composition, regeneration and microtopography of the southern Appalachian mountains at variable scales.

A Comparison of Herpetofaunal Sampling Effectiveness of Pitfall, Single-ended, and Double-ended Funnel Traps Used with Drift Fences

We assessed the relative effectiveness of pitfalls, single-ended, and double-ended funnel traps at 12 replicate sites in sand pine scrub using drift fence arrays. Pitfalls captured fewer species but yielded more individuals of many species and higher average species richness than funnel traps. Pitfalls and funnel traps exhibited differential capture bias probably due to differences in behavior or morphology. More surface-active lizards, frogs, and small semifossorial herpetofaunal species were captured in pitfalls whereas captures of large snake species were restricted to funnel traps. Double-ended funnel traps captured twice as many large snakes as single-ended funnel traps. All three trap types yielded similar estimates of relative abundance of lizards and frogs but not snakes. Estimates of relative abundance of large snakes were higher for double-ended funnel traps than pitfalls or single-ended funnel traps. Pitfall and funnel traps yield complementary results, and choice of type(s) depends on target species and sampling goals.

Response of reptile and amphibian communities to canopy gaps created by wind disturbance in the southern Appalachians

Reptile and amphibian communities were sampled in intact gaps created by wind disturbance, salvage-logged gaps, and closed canopy mature forest (controls). Sampling was conducted during June-October in 1997 and 1998 using drift fences with pitfall and funnel traps. Basal area of live trees, shade, leaf litter coverage, and litter depth was highest in controls and lowest in salvaged gaps. Percent cover, length, and diameter of coarse woody debris (CWD) were significantly greater in intact gaps than in salvaged gaps or controls. Coarse woody debris was more decayed and had less bark in controls than gaps. The relative abundance of salamanders and American toads, and species richness and diversity of amphibians did not differ among treatments. In contrast, relative abundance of two lizard species and (marginally) snakes, and species richness and diversity of reptiles was higher in both gap treatments than in controls. Results suggest that higher light in gaps positively influenced reptile abundance, but CWD at the tested levels was not an important determinant of habitat quality. The presence of a partial canopy and other forest features in both gap treatments may have adequately retained the microclimatic conditions required by moisture-sensitive amphibians. Xeric study sites and an associated assemblage of species that are pre-adapted to relatively warm, dry conditions also might partially explain the absence of any significant response by amphibians. In the closed canopy forests of the southern Appalachians, I suggest that salamanders were historically dominant, whereas many reptile species occurred at low densities and depended upon infrequent natural disturbance to create ephemeral patches of suitable habitat. Further study is required to determine what parameters of disturbance influence reptile and amphibian communities, and how these effects might differ along a moisture gradient and among species. 0 2001 Elsevier Science B.V. All rights reserved.

Individual variation in acorn production by five species of southern Appalachian oaks

Acorns are an important wildlife food resource and seed source for oak regeneration. Most acorn production studies note wide and consistent differences in acorn productivity among individuals, but none clearly demonstrate determinants of productivity. Acorn production by black, northern red, scarlet, chestnut and white oak was measured from 1993 to 1997 in the southern Appalachians was measured and compared among species and individuals. To standardize comparisons among different sized trees and simplify for use by forest managers, the number of acorns per tree were converted to the number/m 2 BA (basal area). On average, white oak produced the most acorns and chestnut oak the fewest. Northern red and white oak produced higher green weight and dry biomass than the other three species. There was a significant positive relationship between tree basal area and the number of acorns produced per crown for all species (r 2 between 0.10 and 0.27). However, this is because larger trees have greater crown areas for producing acorns, and not because they produce more acorns per unit area of crown. Alone, BA was significantly, positively correlated with the number of acorns/m 2 BA only in black, northern red (p < 0.06) and white oak (not in scarlet or chestnut oak) but explained little of the variation in acorn production among individuals. Trees25 cm DBH of most species produced significantly fewer acorns/m 2 BA than their larger counterparts. However, many small (<23 cm DBH) scarlet oaks originating from a 1967 clear-cut were prolific producers, whereas white oaks (<25 cm DBH) in the same stand were not. Frequency of acorn production ranged from never to yearly among individuals. Good producers (trees producing5-year species mean) composed 20% (chestnut oak) to 46% (northern red oak) of sample populations but contributed disproportionately to the acorn crop in moderate and good crop years. Good producers produced acorns more frequently and had more acorns/m 2 BA on fruiting trees than did poor producers. However, in any given year good and poor producers were similarly represented in the fruiting population. Hence, good producers could not be easily identified by the presence of acorns during poor crop years, nor could poor producers be identified by an absence of acorns in good crop years. # 2000 Elsevier Science B.V. All rights reserved.

Fruit Fate, Seed Germination and Growth of an Invasive Vine – an Experimental Test of ‘sit and Wait’ Strategy

Oriental bittersweet (Celastrus orbiculatus Thunb.) is a non-indigenous, invasive woody vine in North America that proliferates in disturbed open sites. Unlike most invasive species, C. orbiculatus exhibits a ‘sit and wait’ strategy by establishing and persisting indefinitely in undisturbed, closed canopy forest and responding to canopy disturbance with rapid growth, often overtopping trees. We compared fruit fates of C. orbiculatus and native American holly (Ilex opaca). We also explored mechanisms for this ‘sit and wait’ invasion strategy by testing the effect of C. orbiculatus fruit crop density on removal rates and by examining the influence of seed treatment and light intensity on seed germination and seedling growth. More C. orbiculatus than I. opaca fruits became damaged, and damage occurred earlier. More fruit fell from C. orbiculatus than I. opaca, but removal rates by frugivores did not differ (76.0 ± 4.2% vs 87.5 ± 3.7%, respectively). Density (number of fruits in a patch) of C. orbiculatus did not influence removal rates. Scarification (bird-ingestion) of C. orbiculatus seed delayed germination but seeds germinated in similar proportion to manually defleshed seeds (sown either singly or all seeds from a fruit). Germination of seeds within intact fruits was inhibited and delayed compared to other treatments. Seed treatment did not affect seedling growth. The proportion of seeds germinating and time until germination was similar among five light intensity levels, ranging from full sun to closed-canopy. Seedlings in >70% photosynthetically active radiation (PAR) had more leaves, heavier shoots, and longer, heavier roots than seedlings at lower PAR levels. Results show that most (>75%) C. orbiculatus seeds are dispersed, seedlings can establish in dense shade, and plants grow rapidly when exposed to high light conditions. Control strategies for this highly invasive species should likely focus on minimizing seed dispersal by vertebrates.

A comparison of relative abundance and biomass of ground-dwelling arthropods under different forest management practices

Abstract Habitat structural characteristics and relative abundance and biomass of ground-dwelling arthropods were compared among four replicated stand treatments: intense burning and salvage logging; clearcutting follwed by roller-chopping (100% soil surface disturbance); clearcutting followed by bracke seeding (30% soil surface disturbance); and naturally regenerated mature, forested sand pine scrub. Arthropods were classified by taxa and by mean maximum width. Monthly trends in abundance and biomass of arthropods captured are described. Mature forest differed from the three disturbance treatments in most habitat structural features, but disturbance treatments were similar. Total numbers and dry weight did not differ among treatments but more individuals and biomass of arthropods less than 5 mm mean maximum width occurred in burned sites. These were significantly more arthropods 10 mm or less in mean maximum width than over 10 mm, but arthropods 5–10 mm had the highest biomass. The relative abundance of some taxa differed among treatments, and taxa differed in monthly capture rates. Total numbers and biomass of captured arthropods were greatest from late May through November.

Wintering Yellow-rumped Warblers ( Dendroica coronata ) track manipulated abundance of Myrica cerifera fruits

Abstract Food availability during winter may determine habitat use and limit populations of overwintering birds, yet its importance is difficult to judge because few studies have experimentally tested the response of nonbreeding birds to changes in resource abundance. We experimentally examined the link between fruit availability and habitat use by manipulating winter abundance of Myrica cerifera L. (Myricaceae) fruits in managed longleaf (Pinus palustris) and loblolly (P. taeda) pine stands in South Carolina. Myrica cerifera is a common understory shrub in the southeastern United States and provides lipid-rich fruit in late winter (February and March), when insects and other fruits are scarce. On treatment plots, we covered fruiting M. cerifera shrubs with netting in early winter to prevent birds from eating their fruits. In late February, when M. cerifera fruit crops were largely depleted elsewhere on our study site, we uncovered the shrubs and documented the response of the bird community to those patches of high fruit availability. Relative to control plots, total bird abundance (excluding the most common species, Yellow-rumped Warbler [Dendroica coronata]) and species richness did not change after net removal. Yellow-rumped Warblers, however, became significantly more abundant on treatment plots after net removal, which suggests that they track M. cerifera fruit abundance. We suggest that M. cerifera plays a role in determining the local distribution of wintering Yellow-rumped Warblers at our study site. To put these results into a management context, we also examined the effect of prescribed fire frequencies on M. cerifera fruit production. Across pine stands with different fire regimes, M. cerifera fruit abundance increased with the number of years since burning. It takes 4–6 years for individuals to recover sufficiently from a burn to produce large quantities of fruit. Thus, shorter intervals between burns will reduce winter fruit availability. Taken together, these results suggest that within those pine plantations, the local winter distribution of at least one common migratory bird is closely tied to fruit abundance, which in turn is tied to the frequency of prescribed fires.

Response of white-footed mice (Peromyscus leucopus) to coarse woody debris and microsite use in southern Appalachian treefall gaps

The influence of treefall gaps and coarse woody debris (CWD) on white-footed mouse (Peromyscus leucopus) abundance was tested experimentally during 1996–1999 in a southern Appalachian hardwood forest. I compared the relative abundance and body size of P. leucopus among unsalvaged gaps that were created by wind disturbance and retained high CWD levels, salvage logged gaps where fallen and damaged tree boles had been removed, and closed-canopy controls. I also tested the relative use by mice of four microsite types: CWD, pits, woody brush, and open ground. One-hundred and forty-one P. leucopus were captured 310 times during the study. There were no differences in capture success, body size, or sex ratio among treatments before or after salvage logging, but abundance varied among years. Capture success was higher at traps set adjacent to CWD (P<0.05) and in pits (P<0.10) than at traps set under brush or on open ground. In the southern Appalachians, windthrow-created canopy gaps and associated microsites do not affect habitat use by P. leucopus at a landscape level (as measured by relative abundance among treatments), but CWD influences the microdistribution of P. leucopus where it is present.

Response of Reptiles and Amphibians to Repeated Fuel Reduction Treatments

Abstract Recent use of prescribed fire and fire surrogates to reduce fuel hazards has spurred interest in their effects on wildlife. Studies of fire in the southern Appalachian Mountains (USA) have documented few effects on reptiles and amphibians. However, these studies were conducted after only one fire and for only a short time (1–3 yr) after the fire. From mid-May to mid-August 2006 and 2007, we used drift fences with pitfall and funnel traps to capture reptiles and amphibians in a control and 3 replicated fuel-reduction treatments: 1) twice-burned (2003 and 2006), 2) mechanical understory cut (2002), and 3) mechanical understory cut (2002) followed by 2 burns (2003 and 2006). We captured fewer salamanders in mechanical + twice-burned treatment areas than in twice-burned and control treatment areas, but we captured more lizards in mechanical + twice-burned treatment areas than in other treatment areas. Higher lizard captures in mechanical + twice-burned treatment areas likely was related to increased ground temperatures and greater thermoregulatory opportunities. Higher and more variable ground temperatures and faster drying of remaining litter and duff may have led to fewer salamander captures in mechanical + twice-burned treatment areas. Our longer term results, after 2 prescribed burns, differ from shorter term results. After one prescribed burn at the same site, eastern fence lizard (Sceloporus undulatus) captures were greater in mechanical + burn treatment areas but salamander captures did not differ among treatment areas. Our results indicate that multiple (≥2) fuel-reduction treatments that decrease canopy cover may benefit lizards but negatively affect salamanders.

Short‐Term Effects of Fire and Other Fuel Reduction Treatments on Breeding Birds in a Southern Appalachian Upland Hardwood Forest

Abstract We compared the effects of 3 fuel reduction techniques and a control on breeding birds during 2001–2005 using 50-m point counts. Four experimental units, each >14 ha, were contained within each of 3 replicate blocks at the Green River Game Land, Polk County, North Carolina, USA. Treatments were 1) prescribed burn, 2) mechanical understory reduction (chainsaw-felling of shrubs and small trees), 3) mechanical + burn, and 4) controls. We conducted mechanical treatments in winter 2001–2002 and prescribed burns in spring 2003. Tall shrub cover was substantially reduced in all treatments compared to controls. Tree mortality and canopy openness was highest in the mechanical + burn treatment after burning, likely due to higher fuel loading and hotter burns; tree mortality increased with time. Many bird species did not detectably decrease or increase in response to treatments. Species richness, total bird density, and some species, including indigo buntings (Passerina cyanea) and eastern bluebirds (Sialia sialis), increased in the mechanical + burn treatment after a 1-year to 2-year delay; eastern wood-pewees (Contopus virens) increased immediately after treatment. Hooded warblers (Wilsonia citrina), black-and-white warblers (Mniotilta varia), and worm-eating warblers (Helmitheros vermivorus) declined temporarily in some or all treatments, likely in response to understory and (or) leaf litter depth reductions. Densities of most species affected by treatments varied with shrub cover, tree or snag density, or leaf litter depth. High snag availability, open conditions, and a higher density of flying insects in the mechanical + burn treatment likely contributed to increased bird density and species richness. In our study, fuel reduction treatments that left the canopy intact, such as low-intensity prescribed fire or mechanical understory removal, had few detectable effects on breeding birds compared to the mechanical + burn treatment. High-intensity burning with heavy tree-kill, as occurred in our mechanical + burn treatment, can be used as a management tool to increase densities of birds associated with open habitat while retaining many forest and generalist species, but may have short-term adverse effects on some species that are associated with the ground- or shrub-strata for nesting and foraging.