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1. We tested the interactions between biotic and abiotic factors in structuring temperate forest communities by comparing tree recruitment after 7 years inside 30 pairs of exclosure (excluding ungulates: red deer, roe deer, bison, moose, wild boar) and control plots (7 × 7 m each) in one of the most natural forest systems in Europe, the Białowieża Primeval Forest (eastern Poland). The strictly protected part of that forest hosts the complete native variety in trees, ungulates and their carnivores and excludes human intervention. 2. We analysed whether the exclosure effect interacted with abiotic factors, relevant for tree recruitment (canopy cover, ground vegetation cover, soil fertility and soil wetness) at different stages of tree regeneration (seedlings, saplings ≤ 50 and > 50 cm). 3. Contrary to our expectations, a single factor dominated at each stage of tree regeneration. Herbaceous vegetation cover was the main factor determining the number of seedlings with an optimum at 38% of cover. Soil fertility determined the density of saplings ≤ 50 cm, with on average three times higher density on eutrophic than on oligotrophic soils. Herbivory was the main factor determining recruitment rate of trees into > 50 cm size classes only. 4. The density of saplings that grew into the > 50 cm size class was more than three times higher in the exclosures than in the control plots during 7 years. In the absence of ungulates, on average 3.1 species recruited into the > 50 cm size class compared to 1.7 in control plots. Tree species occurred in more equal proportions inside exclosures, whereas species composition was pushed towards strong dominance of a preferred forage species, Carpinus betulus, in the presence of ungulates. This suggests that preference of species by ungulates can coincide with tolerance to browsing. 5. Synthesis. The study showed that abiotic conditions dominated the early stages and ungulate impact the later stages of tree regeneration, indicating the context-dependence of herbivore top-down effects. Heterogeneity in abiotic and biotic conditions may, therefore, have an important influence on the strength of top-down effects and the role that herbivores play in natural ecosystems. [ABSTRACT FROM AUTHOR]

Wolves (Canis lupus) belong to 3 genetically distinct subpopulations despite the absence of topographic barriers limiting dispersal. Based on data on wolf diets from 13 localities and wolf kill remains from a national-scale census, we investigated regional variation in wolf diet in relation to species structure of ungulate communities and spatial genetic differentiation of wolf populations. We also tested if various sources of data on wolf prey (scats and kills) and availability of ungulates (game inventory and harvest) yielded comparable results on prey selection. The main prey of wolves was red deer (Cervus elaphus), roe deer (Capreolus capreolus), and wild boar (Sus scrq/h). The proportion of main prey in wolf diets increased with prey availability in the community, yet wolves selected red deer, preyed on roe deer proportionally to their relative abundance, and avoided wild boar. Large prey was recorded among kills more often than small prey. Despite similar species structure of ungulate communities throughout Poland, there were significant regional differences in wolf diet, which corresponded to the genetic structure of populations. In northeastern Poland, wolves frequently hunted red deer, roe deer, wild boar, beavers (Castor.fiber), and moose (Alces alces). In eastern Poland, roe deer dominated kills. In southeastern Poland, wolves were strongly specialized on red deer. We propose that prey and habitat specialization of wolves, rather than geographic distance or topographic barriers to dispersal, are responsible for the observed ecological divergence of wolf populations, as reflected in their diet composition. [ABSTRACT FROM AUTHOR]