Spatial patterns in neighbourhood effects on woody plant selection and bark stripping by deer in a lowland alluvial forest

Abstract

Questions Ungulate herbivory and its impact on one plant species may be driven by other plants in the neighbourhood. Although such neighbourhood effects have long been recognized, there is limited understanding of how spatial variation in these effects relates to local plant density and distances between plants. Our goal was to examine if the density of or distance to conspecific and heterospecific neighbouring woody individuals produces neighbourhood effects on bark stripping by deer, and how these effects differ in spatial scale and type (reduce/increase herbivory). Location Lowland old‐growth forest, Czech Republic. Methods Woody individuals were assessed for evidence of bark stripping and the level of damage done by deer in a square 4‐ha plot, mapping all woody stems ≥1 cm diameter at breast height. The spatial distribution of stripping was used to examine neighbourhood effects using spatial point pattern methods. Results The density and distance to neighbours and species identity of focal and neighbouring individuals contributed to a large spatial variation in neighbourhood effects (up to distances of 2–30 m from neighbours). Neighbourhood effects arose mainly from the interactions between neighbouring shrub species and all tree species, and interactions between individual species pairs. Neighbourhood effects more often increased than reduced the stripping of focal individuals. The stripping of Ulmus laevis, Acer campestre and Crataegus laevigata increased near conspecifics, while the stripping of all tree species was more likely near Ulmus laevis, Fraxinus angustifolia and shrubs. Heterospecific tree species were less susceptible to stripping near Tilia cordata and especially Carpinus betulus. Conclusion Our study provides new insight into neighbourhood effects by showing how and at which spatial scales woody plant interactions modify deer herbivory. We advocate considering the life stage and relevant plant traits with multivariate spatial methods in order to elucidate the role of neighbourhood effects in complex plant communities.

Sex-driven neighborhood effects on herbivory in the dioecious Mediterranean palm Chamaerops humilis L.

“…Such large-scale neighborhood effects can be explained by the foraging behavior of herbivores (Fryxell et al 2008 ) or by spatial heterogeneity in the pattern of plants (Wiegand and Moloney 2014 ). In our study case, large-scale neighborhood effects on goat folivory were detected even when applying local marking null models (e.g., Holík and Janík 2022 ), which reduces the influence of spatial heterogeneity. Therefore, differences in the spatial scaling between goat florivory and goat folivory indicate that goat-feeding behavior is dependent on the abundance and type of food resource (inflorescences vs. leaves).…”

“…Deer browsing on Abies balsamea seedlings negatively correlated with the nutritional quality of conspecific seedlings at distances up to 50 m (Champagne et al 2018 ). In a lowland alluvial forest, the probability of bark stripping by deer on hetero-specific trees decreased up to a distance of 25 m from Carpinus trees (Holík and Janík 2022 ). Such large-scale neighborhood effects can be explained by the foraging behavior of herbivores (Fryxell et al 2008 ) or by spatial heterogeneity in the pattern of plants (Wiegand and Moloney 2014 ).…”

“… To find out if, and at what distance r , the density of conspecific neighbors influences the attack intensity (hypothesis 1), we used analysis of univariate patterns with one quantitative mark. Specifically, we used the density correlation function C m,g ( r ) (Fedriani et al 2015 ; Holík and Janík 2022 ) to evaluate whether the intensity of attack of palms is positively or negatively correlated with the density of conspecifics at distance r . For example, a positive value of C m,g ( r ) indicates that the attack intensity of palms are positively correlated with the neighborhood density at distance r .…”

“…Since Ruiz et al ( 2018 ) described contrasting neighborhood effects on moth herbivory across study sites, we also expect some differences between our plots. Moreover, the vegetation patchiness and the density of conspecific neighbors increase herbivory by goats (De Knegt et al 2007 ; Chebli et al 2020 ) and other ungulates (e.g.,Holík et al 2021 ; Murphy and Comita 2021 ; Holík and Janík 2022 ). As our target herbivores show divergent phylogeny (insect vs. mammal) and feeding behavior, we also expect that the sign and spatial extent of the neighborhood effects will vary between both herbivorous species.…”

“…Higher densities of conspecific neighbors can either attract herbivores (‘resource concentration effect’; Root 1973 ) or deter them (‘resource dilution effect’; Otway et al 2005 ). These trait- and density-related conspecific effects may only operate up to certain distances from the focal plant, resulting in spatially explicit conspecific neighborhood effects (Kim and Underwood 2015 ; Holík and Janík 2022 ). While sexual dimorphism is prevalent in dioecious species and has been demonstrated to influence herbivory (Cornelissen and Stiling 2005 ), the role of plant sex as a driver of neighborhood effects remains unstudied.…”