Search USGS⌕ Search
Home/Archive/USGS

USGS · 70192142

Interactive effects of deer exclusion and exotic plant removal on deciduous forest understory communities

Norman Bourg·William J. McShea·Valentine Herrmann·Chad M. Stewart
View original source ↗Export metadata ↓

Abstract

Mammalian herbivory and exotic plant species interactions are an important ongoing research topic, due to their presumed impacts on native biodiversity. The extent to which these interactions affect forest understory plant community composition and persistence was the subject of our study. We conducted a 5-year, 2 × 2 factorial experiment in three mid-Atlantic US deciduous forests with high densities of white-tailed deer ( Odocoileus virginianus ) and exotic understory plants. We predicted: (i) only deer exclusion and exotic plant removal in tandem would increase native plant species metrics; and (ii) deer exclusion alone would decrease exotic plant abundance over time. Treatments combining exotic invasive plant removal and deer exclusion for plots with high initial cover, while not differing from fenced or exotic removal only plots, were the only ones to exhibit positive richness responses by native herbaceous plants compared to control plots. Woody seedling metrics were not affected by any treatments. Deer exclusion caused significant increases in abundance and richness of native woody species >30 cm in height. Abundance changes in two focal members of the native sapling community showed that oaks ( Quercus spp.) increased only with combined exotic removal and deer exclusion, while shade-tolerant maples ( Acer spp.) showed no changes. We also found significant declines in invasive Japanese stiltgrass ( Microstegium vimineum ) abundance in deer-excluded plots. Our study demonstrates alien invasive plants and deer impact different components and life-history stages of the forest plant community, and controlling both is needed to enhance understory richness and abundance. Alien plant removal combined with deer exclusion will most benefit native herbaceous species richness under high invasive cover conditions while neither action may impact native woody seedlings. For larger native woody species, only deer exclusion is needed for such increases. Deer exclusion directly facilitated declines in invasive species abundance. Resource managers should consider addressing both factors to achieve their forest management goals.

Explore related subjects

AoB PLANTSArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Norman Bourg, William J. McShea, Valentine Herrmann, Chad M. Stewart. 2017-09-07. Interactive effects of deer exclusion and exotic plant removal on deciduous forest understory communities. https://doi.org/10.1093/aobpla%2Fplx046

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2022

Post-fire seed dispersal of a wind-dispersed shrub declined with distance to seed source, yet had high levels of unexplained variation

Plant-population recovery across large disturbance areas is often seed-limited. An understanding of seed dispersal patterns is fundamental for determining natural-regeneration potential. However, forecasting seed dispersal rates across heterogeneous landscapes remains a challenge. Our objectives were to determine (i) the landscape patterning of post-disturbance seed dispersal, and underlying sources of variation and the scale at which they operate, and (ii) how the natural seed dispersal patterns relate to a seed augmentation strategy. Vertical seed trapping experiments were replicated across 2 years and five burned and/or managed landscapes in sagebrush steppe. Multi-scale sampling and hierarchical Bayesian models were used to determine the scale of spatial variation in seed dispersal. We then integrated an empirical and mechanistic dispersal kernel for wind-dispersed species to project rates of seed dispersal and compared natural seed arrival to typical post-fire aerial seeding rates. Seeds were captured across the range of tested dispersal distances, up to a maximum distance of 26 m from seed-source plants, although dispersal to the furthest traps was variable. Seed dispersal was better explained by transect heterogeneity than by patch or site heterogeneity (transects were nested within patch within site). The number of seeds captured varied from a modelled mean of ~13 m −2 adjacent to patches of seed-producing plants, to nearly none at 10 m from patches, standardized over a 49-day period. Maximum seed dispersal distances on average were estimated to be 16 m according to a novel modelling approach using a ‘latent’ variable for dispersal distance based on seed trapping heights. Surprisingly, statistical representation of wind did not improve model fit and seed rain was not related to the large variation in total available seed of adjacent patches. The models predicted severe seed limitations were likely on typical burned areas, especially compared to the mean 95–250 seeds per m 2 that previous literature suggested were required to generate sagebrush recovery. More broadly, our Bayesian data fusion approach could be applied to other cases that require quantitative estimates of long-distance seed dispersal across heterogeneous landscapes.

Idaho↗
USGS2019

Effects of white-tailed deer (Odocoileus virginianus) exclusion on plant recovery in overwash fans after a severe coastal storm

We documented the impacts of a hyper-abundant deer population on dune vegetation recovering from severe storm surge on a barrier island through use of permanent plots and a repeated measures analysis. Three years after landfall of the storm, vegetation cover was dominated by American beachgrass, Ammophila breviligulata, though we observed twelve plant species among plots surveyed. We documented significantly greater vegetation cover in fenced than unfenced plots in overwash fans in two consecutive years. The difference in species richness between fenced and unfenced plots was significant, though richness was consistently low (≤4 species per plot) and we did not detect a statistically significant difference between years. Both deer trampling and foraging effects were captured in this study, though separation between these effects was not possible. Because trampling effects are often exacerbated on sandy soils, trampling and foraging effects should be isolated and investigated in future assessments of deer impacts on coastal vegetation. Managing deer to lower abundance may enhance coastal resilience if vegetation is allowed to recover unimpeded by foraging and trampling, though a better understanding of the precise nature of deer impacts on dune vegetation is necessary.

AoB PLANTS↗
USGS2019

Soil chemistry, and not short-term (1–2 year) deer exclusion, explains understory plant occupancy in forests affected by acid deposition

The loss of species diversity and plant community structure throughout the temperate deciduous forests of North America have often been attributed to overbrowsing by white-tailed deer ( Odocoileus virginanus ). Slow species recovery following removal from browsing, or reduction in deer density, has been termed a legacy effect of past deer herbivory. However, vegetation legacy effects have also coincided with changes to soil chemistry throughout the north-eastern USA. In this paper, we assess the viability of soil chemistry (i.e. pH, extractable nutrients and extractable metals) and other factors (topography, light, overstory basal area and location) as alternative explanations for a lack of vegetation recovery. We compared the relative effects of soil chemistry, site conditions and short-term (1–2 year) deer exclusion on single-species occupancy probabilities of 10 plant taxa common to oak-hickory forests in central Pennsylvania. We found detection for all modelled species was constant and high ( ⁠ p ^ "> p ^ p^ > 0.65), and occupancy probability of most taxa was best explained by at least one soil chemistry parameter. Specifically, ericaceous competing vegetation was more likely to occupy acidic (pH < 3.5), base cation-poor (K < 0.20 cmol c kg −1 ) sites, while deer-preferred plants were less likely to occur when soil manganese exceeded 0.1 cmol c kg −1 . Short-term deer exclusion did not explain occupancy of any plant taxon, and site conditions were of nominal importance. This study demonstrates the importance of soil chemistry in shaping plant community composition in the north-central Appalachians, and suggests soil as an alternative, or additional, explanation for deer vegetation legacy effects. We suggest that the reliance on phyto-indicators of deer browsing effects may overestimate the effects of browsing if those species are also limited by unfavourable soil conditions. Future research should consider study designs that address the complexity of deer forest interactions, especially in areas with complex site-vegetation histories.

Pennsylvania↗