Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

Sabo, Autumn E.; Frerker, Katie; Waller, Donald M.; Kruger, Eric L.

doi:10.1111/1365-2745.12748

Cited by 33 publications

(17 citation statements)

References 80 publications

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“…Over a large monitoring network, covering a broad range of temperate forest ecosystems, we observed that the presence of wild ungulates enhanced species richness of the herbaceous layer. In line with Sabo, Frerker, Waller, and Kruger (), our results show that ungulate impacts on forest understory vegetation are a consequence of their effects on environmental factors but also bring to light their critical role on plant species dispersal and plant‐plant interactions. More specifically, by reducing the cover of shrub layers and dominant and palatable plant species, deer maintain an openness that enhances ground flora diversity.…”

Section: Discussionsupporting

confidence: 90%

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Ungulates increase forest plant species richness to the benefit of non‐forest specialists

Boulanger

Dupouey

Archaux

et al. 2017

Global Change Biology

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Large wild ungulates are a major biotic factor shaping plant communities. They influence species abundance and occurrence directly by herbivory and plant dispersal, or indirectly by modifying plant-plant interactions and through soil disturbance. In forest ecosystems, researchers' attention has been mainly focused on deer overabundance. Far less is known about the effects on understory plant dynamics and diversity of wild ungulates where their abundance is maintained at lower levels to mitigate impacts on tree regeneration. We used vegetation data collected over 10 years on 82 pairs of exclosure (excluding ungulates) and control plots located in a nation-wide forest monitoring network (Renecofor). We report the effects of ungulate exclusion on (i) plant species richness and ecological characteristics, (ii) and cover percentage of herbaceous and shrub layers. We also analyzed the response of these variables along gradients of ungulate abundance, based on hunting statistics, for wild boar (Sus scrofa), red deer (Cervus elaphus) and roe deer (Capreolus capreolus). Outside the exclosures, forest ungulates maintained higher species richness in the herbaceous layer (+15%), while the shrub layer was 17% less rich, and the plant communities became more light-demanding. Inside the exclosures, shrub cover increased, often to the benefit of bramble (Rubus fruticosus agg.). Ungulates tend to favour ruderal, hemerobic, epizoochorous and non-forest species. Among plots, the magnitude of vegetation changes was proportional to deer abundance. We conclude that ungulates, through the control of the shrub layer, indirectly increase herbaceous plant species richness by increasing light reaching the ground. However, this increase is detrimental to the peculiarity of forest plant communities and contributes to a landscape-level biotic homogenization. Even at population density levels considered to be harmless for overall plant species richness, ungulates remain a conservation issue for plant community composition.

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Section: Discussionsupporting

confidence: 90%

Section: Beyond Increasing Species Richness: Shifts In Species Compmentioning

confidence: 88%

Ungulates increase forest plant species richness to the benefit of non‐forest specialists

Boulanger

Dupouey

Archaux

et al. 2017

Global Change Biology

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“…High soil compaction alters soil hydrology and aggregation and has deleterious effects on plant vital rates, leading to physiological dysfunction, reduced water and soil nutrient absorption, and altered root respiration (Kozlowski 1999). Increased soil compaction by deer has known negative effects on forest plant abundance and diversity (Sabo et al 2017). For Arisaema, our previous work demonstrates that plant vital rates decline as abiotic site impacts by deer increases ( fig.…”

Section: Study Sitesmentioning

confidence: 97%

Deer Indirectly Alter the Reproductive Strategy and Operational Sex Ratio of an Unpalatable Forest Perennial

Bialic‐Murphy

Heckel

McElderry

et al. 2020

The American Naturalist

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Environmental conditions impose restrictions and costs on reproduction. Multiple reproductive options exist when increased reproductive costs drive plant populations toward alternative reproductive strategies. Using 4 years of demographic data across a deer impact gradient, where deer alter the abiotic environment, we parameterize a size-dependent integral projection model for a sexually labile and unpalatable forest perennial to investigate the demographic processes driving differentiation in the operational sex ratio (OSR) of local populations. In addition to a relative increase in asexual reproduction, our results illustrate that nontrophic indirect effects by overabundant deer on this perennial result in delayed female sex expression to unsustainably large plant sizes and lead to more pronounced plant shrinkage following female sex expression, effectively increasing the cost of reproduction. Among plants of reproductive age, increased deer impact decreases the size-dependent probability of flowering and reduces reproductive consistency over time. This pattern in sex expression skews populations toward female-biased OSRs at low deer impact sites and male-biased OSRs at intermediate and high deer impact sites. While this shift toward a male-biased OSR may ameliorate pollen limitation, it also decreases the effective population size when coupled with increased asexual reproduction. The divergence of reproductive strategies and reduced lifetime fitness in response to indirect deer impacts illustrate the persistent long-term effects of overabundant herbivores on unpalatable understory perennials.

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“…We focused on two questions: (a) how do deer affect the abundance and diversity of tree species regeneration along its height growth, and (b) what is the impact of the presence of deer on the diversity of herbaceous layer vegetation? Species composition in the herbaceous layer may be sensitive to changes in the tree species regeneration layer mediated by deer (Beguin, Pothier, & Côte, ; Sabo, Frerker, Waller, & Kruger, ; Stewart et al., ). Therefore, we also tested for the indirect influence of red deer on the diversity of shorter tree species regeneration and the diversity of the herbaceous layer through its influence on the recruitment of saplings of tree species.…”

Section: Introductionmentioning

confidence: 99%

Assessment of the long‐term impact of deer on understory vegetation in mixed temperate forests

Simončič

Bončina

Jarni

et al. 2019

J Vegetation Science

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Questions What is the long‐term impact of deer browsing on the diversity of the herbaceous layer and tree species regeneration? Which parameters of regeneration of the tree species regeneration and the herbaceous layer best indicate browsing impact? Study site Dinaric Mountains, Slovenia. Methods We studied the long‐term impact of red deer on mixed temperate forests by comparing the tree species regeneration and herbaceous layer vegetation under two treatments: deer present, no deer. We analyzed the regeneration of trees older than one year up to a diameter at breast height of 10 cm (categorized into five height classes) and the cover abundance of plant species in the herbaceous layer (<50 cm). Results There were no significant differences between the treatments in the number of tree species regeneration. Browsing impact on the most abundant tree species—European beech, silver fir and sycamore—varied, indicating differences in palatability. When deer were present, the number of silver fir regenerating was significantly lower in all height classes, and regeneration of European beech specimens shorter than 50 cm was more abundant, while for sycamore shorter seedlings (<20 cm) were more abundant, and regeneration of taller specimens (≥50 cm) was significantly less abundant. The reduction of tree species diversity during natural regeneration is evident. There were no significant differences between the treatments in the number and diversity of plant species in the herbaceous layer; however, the abundance of 13 plant species differed significantly between the treatments. Deer reduce the density of tree species saplings due to long‐term browsing and thus indirectly increase tree species diversity in the regeneration up to 20 cm in height and plant species diversity in the herbaceous layer. Conclusions We documented the direct and indirect impact of deer on the diversity of tree species regeneration, but only found an indirect influence on the diversity of the herbaceous layer. The height structure of palatable tree species regeneration appears to be the most appropriate indicator of browsing impact. The observed browsing impact leads to the complete dominance of European beech in the tree species composition of forest stands.

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Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

Cited by 33 publications

References 80 publications

Ungulates increase forest plant species richness to the benefit of non‐forest specialists

Ungulates increase forest plant species richness to the benefit of non‐forest specialists

Deer Indirectly Alter the Reproductive Strategy and Operational Sex Ratio of an Unpalatable Forest Perennial

Assessment of the long‐term impact of deer on understory vegetation in mixed temperate forests

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