White‐tailed deer (Odocoileus virginianus) positively affect the growth of mature northern red oak (Quercus rubra) trees

Abstract

White-tailed deer (Odocoileus virginianus) positively affect the growth of mature northern red oak (Quercus rubra) trees.Ecosphere 4(7):84. http://dx.doi.org/10.1890/ES13-00036.1Abstract. Understanding and predicting the effects of deer (Cervidae) on forest ecosystems present significant challenges in ecosystem ecology. Deer herbivory can cause large changes in the biomass and species composition of forest understory plant communities, including early life-cycle trees (i.e., seedlings and saplings). Such changes can impact juvenile to adult transitions and the future age structure and species composition of mature forests. Changes to understory vegetation also impact flow of energy and nutrients in forest ecosystems. Studies examining the influence of deer on mature trees, however, are rare and rely on extrapolating effects from early life cycle stages of trees. We tested the hypothesis that the absence of deer would result in an increase in the growth rate of mature trees by examining the impact of white-tailed deer (Odocoileus virginianus) on mature canopy trees. We examined incremental growth in individuals of Quercus rubra, an important component of temperate deciduous forests in North America, inside and outside 16-year deer exclosures in eastern U.S. deciduous forests. We found that adult trees inside exclosures grew less than those directly exposed to deer. Our findings highlight the indirect effects of white-tailed deer on the growth of adult individuals of Q. rubra in a way opposite of what would be expected from previous studies based on immature or understory tree populations. We suggest the increased growth of adult trees in the presence of deer may be explained by increased nutrient inputs through deer fecal and urine deposits and the alteration of the competitive environment belowground through the reduction of understory vegetation by browsing. Underscoring the ecological and demographic importance of adult trees in forest ecosystems, results from this study suggest the direct and indirect effects of deer on mature trees should not be overlooked.

Single and interactive effects of deer and earthworms on non-native plants

“…Positive indirect effects of deer on ring-growth of oak trees has been attributed to increased nutrient inputs through deer excreta (Lucas et al, 2013), as deer can add a substantial quantity of nutrients through feces and urine (Jensen et al, 2011). Similarly, earthworm depletion of top soil layers (O horizon) may lead to nutrient pulses that benefit B. thunbergii growth.…”

“…Studies at invasion fronts indicate that earthworm invasion precedes and facilitates invasion by three non-native forest plants [ (Nuzzo et al, 2009). However, experimental removal of non-native Rhamnus cathartica L.P. Mil and Lonicera x bella reduced non-native earthworm abundance (Madritch and Lindroth, 2009), suggesting non-native plants facilitate earthworm invasions. Facilitation is likely mediated through changes in soil quality and structure (Kourtev et al, 2002;Bohlen et al, 2004) and associated effects in microbial communities as a result of earthworms and non-native plant invasions alike (Eisenhauer et al, 2011;Elgersma et al, 2011).…”

Demographic responses of rare forest plants to multiple stressors: the role of deer, invasive species and nutrients

“…Non‐consumptive effects of deer on non‐palatable understorey species (Wiegmann & Waller ; Waller & Maas ) and on mature stages which are not subject to deer herbivory (Lucas et al . ) tend to be positive, but negative effects have been documented for jack‐in‐the‐pulpit ( Arisaema tryphyllum L.) (Heckel et al . ).…”

“…Interestingly, this effect was non-consumptive, as deer did not browse any of the Trillium transplants. Non-consumptive effects of deer on non-palatable understorey species (Wiegmann & Waller 2006;Waller & Maas 2013) and on mature stages which are not subject to deer herbivory (Lucas et al 2013) tend to be positive, but negative effects have been documented for jack-in-the-pulpit (Arisaema tryphyllum L.) (Heckel et al 2010). Non-consumptive deer effects may occur directly through trampling, or indirectly through changes in soil properties or surrounding vegetation (Van der Wal et al 2003;Heckel et al 2010;Jensen et al 2011) and potentially through effects on microbial communities and decomposition processes (Wardle & Bardgett 2004).…”

Biological Flora of the British Isles:Quercus rubra

“…A 6‐year‐study in Pennsylvania Q. rubra forests showed negative impacts of deer browsing on seedling growth (Long, Brose, & Horsley, 2011). In contrast, absence of deer reduced growth of adult 16‐year‐old Q. rubra in Virginia, USA (Lucas et al, 2013). Indirect effects by nutrient input through deer faecal and urine deposition, and also reduction of understorey competition by browsing, may have a positive effect on adult Q. rubra trees (Lucas et al, 2013).…”