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Litter-dwelling arthropods play crucial roles in litter decomposition and nutrient cycling, and changes in their diversity or abundance can affect these processes. Previous studies have outlined individual effects of invasive plants and overabundant ungulates on litter-dwelling arthropod communities but have paid little attention to whether invasive plants and ungulates interact to affect these arthropod communifies. We examined how invasive Amur honeysuckle (Lonicera maackii) and grazing by white-tailed deer (Odocoileus virginianus) affected diversity, abundance, and taxonomic composition of litter-dwelling arthropod communities in a deciduous forest in southwestern Ohio. We also examined whether deer or honeysuckle affected substrate composition and depth of litter. We found no significant effect of honeysuckle, deer, or their interaction on arthropod diversity, bur exclusion of deer increased total arthropod abundance and abundance of Araneae, and thereby affected taxonomic composition of the litter community. These effects were likely related to greater plant cover and less soil compaction in areas from which deer were excluded. Honeysuckle negatively affected Araneae abundance and positively affected Acari abundance, possibly revealing an indirect effect of Araneae on Acari. A honeysuckle x deer interaction on abundance of Acari was important only during the first year of our study. There were no differences in arthropod abundance between honeysuckle-absent and honeysuckle-removed plots, indicating rapid restoration of the litter community after honeysuckle removal. Neither honeysuckle nor deer affected composition or depth of litter. Our findings suggest that current management techniques that control the effects of honeysuckle and deer on native plant communities by separate measures may be sufficient to reduce impacts on litter-dwelling arthropods., INTRODUCTION Above-ground and below-ground food webs often have been studied separately, although connections between these food webs are being revealed (Wardle, 2002; Coleman et al., 2004; Bardgett and Wardle, 2010). [...]

To assess the effects of deer browsing on understory composition, we examined hardwood forests with documented differences in browse intensity within two regions of the Hiawatha National Forest in Michigan's Upper Peninsula. A deciduous twig damage assessment confirmed that two sites within the southern region experienced high white-tailed deer (Odocoileus virginianus) browse intensity (44-49% of twigs browsed) and two sites within the northern region incurred low browse intensity (0.5% and 0.6% of twigs browsed). We used within-site sample means and site-level rarefaction curves to compare understory species richness in these two forests. The forest experiencing low browse intensity had higher woody species richness on a per plot basis than the heavily browsed forest, but the converse was observed for herbaceous species richness. Site-level evaluation with rarefaction curves confirmed the plot-scale results for herbaceous species, but different patterns in woody species richness emerged due to differences in the distributions of species across the four sites. When graphed as a function of cumulative number of plots, we again found that a low browse site had the highest woody plant species richness, but a high browse site had the highest richness values when richness was graphed as a function of cumulative number of stems sampled. This study demonstrates that although species richness is a useful tool for describing ecosystems, results for the same sites can differ based on how species are grouped and on the scale of analysis.

Both herbivory and windthrow disturbances have individually been shown to dramatically alter the structure and composition of forest communities; however, the interaction of these two factors has scarcely been examined. Windthrow disturbance creates microsites such as fallen logs and treefall mounds and pits that may hinder movement and limit visibility of large mammals, thereby reducing the impact of browsing by white-tailed deer. In an old growth Pennsylvania forest that was severely wind-damaged in 1985, a previous study based on sampling in 1994 demonstrated reduced browsing and greater Tsuga canadensis (L.) Carr seedling density on treefall mounds (Long et al., 1998). In this study we surveyed mounds to see if they continue to be effective browsing refugia 9 y later. We also determined whether other types of microsites and nearby microsites provide protection from browsing and tested for an associational density refuge, whereby seedlings of a preferred species are less browsed when surrounded by a high density of saplings. Tsuga canadensis seedlings occurred more frequently on microsites, particularly logs and mounds, whereas randomly selected points occurred most frequently off microsites. Tsuga canadensis seedlings that established off microsites were more heavily browsed than seedlings on mounds or logs. Seedling heights were greatest on mounds and shortest on logs. Although growing on a microsite acted as refugia from browsing, having multiple surrounding microsites did not. Additionally, seedling browse damage was not decreased by having multiple nearby saplings, suggesting no associational defense. Nevertheless, certain microsites continue to provide refugia from browsing 18 y after disturbance and, thereby, enhance regeneration of Tsuga canadensis.

Effects of multiple herbivores were isolated in a rare, old-growth, maritime forest that has been affected by high white-tailed deer (Odocoileus virginianus) populations for several decades. Three decades of change in the plant community was described using permanent plots and nearly two decades of recovery using deer exclosures. Additional short-term exclosure experiments were used to separate the effect of rabbit and vole herbivory and the influence of canopy type on understory vegetation. We assessed whether natural enclosures formed by high densities of greenbrier (Smilax rotundifolia and S. glauca) provide spatial refugia for plant species from deer. Significant differences in fenced plots indicate that deer, rabbits and voles individually affect the understory vegetation, though rabbits and voles are secondary to deer that are the major herbivore in the American holly (Ilex opaca) forest. Plant cover decreased within permanent plots from 1967 to 1986; during the same time period deer densities increased drastically island-wide. Since plots were fenced in 1986 no additional significant changes were detected, but this is likely due to an inadequate sample size, The cover of all species depended on the interaction of fencing and canopy type with significantly higher plant cover in fenced plots beneath mixed or exclusively deciduous canopy. The proportion of woody stems surpassing 0.5 m tall was significantly higher when stems were fenced. Browsing impacts were apparent on approximately a quarter of the vegetation in June 2003. Plant cover, richness and diversity were higher within natural greenbrier enclosures. Overall the exclosure studies indicate the potential natural recovery that could occur within the forest if deer herbivory were limited. Few species have been extirpated, although several are confined to the greenbrier enclosures. Under the current level of herbivory, the maritime holly forest composition will be altered, changing the characteristic canopy of a critically imperiled plant community.

Some 30 y after wolves (Canis lupus) were implicated in decimating wintering white-tailed deer (Odocoileus virginianus) in a 3000-[km.sup.2] area of northeastern Minnesota, wintering deer still have not recolonized the area. From 1976 to 2004, we aerially radio-tracked wolves there during 250 h and recorded 2 deer (in 1985 and 2000) killed or eaten by wolves during February and March. We observed no other deer or deer sign, but regularly observed deer, deer sign and wolf-killed deer in adjacent wolf-pack territories. Although habitat in the study area generally remains poor, some regeneration has taken place, and deer have increased adjacent to the area. However, wolf numbers have persisted by preying on moose (Alces alces). We could detect no reason other than wolf predation and deer migration traditions for why wintering deer have not recolonized the area.

We compared the germination rates of running buffalo clover (Trifolium stoloniferum) seeds that had been passed through the digestive tract of a captive white-tailed deer (Odocoileus virginianus) with those that had not. We found no significant difference among germination rates of seeds passed through deer and those not, nor with seeds that were cold-stratified prior to planting and those that were not. Although white-tailed deer are viable vectors for running buffalo clover seed, our data suggest that the rates of ingested seed germination and survival are low. Dispersal and establishment of new populations by white-tailed deer herbivory may not contribute quickly or significantly to the recovery of running buffalo clover at present.

Large effects of white-tailed deer (Odocoileus virginianus) upon individual plants, plant populations and communities have been documented in a number of studies. However, well-supported experimental measures of the magnitude and geographical extent of these effects are still surprisingly scarce. Deer-caused changes in stem morphology and reductions in plant growth rates are well-documented in some parts of the North America. Furthermore, deer have been shown to affect the composition of several plant communities in the north-central and northeastern United States. There are some documented cases of deer-caused reductions in plant survival; most of these are tree seedlings and saplings. However, many studies have detected no effects on plant survival or fecundity, or have found that negative effects occur only in a fraction of years, seasons, sites or deer densities. Little is known about population-level or ecosystem-level impacts. Many regions and plant communities with large deer populations have not been studied. Whereas deer density is clearly important in determining spatial and temporal variation in the presence and magnitude of deer effects, other factors that may modify the effects of deer density are poorly understood.