Deer overabundance reduces forest groundlayer vegetation and can cause cascading impacts on a forest ecosystem. To predict these effects, we must elucidate the relationship between deer density and the status of ground-layer vegetation. This relationship was studied in the Boso Peninsula, where the deer population density exhibits a clear geographical gradient. We examined species richness and cover of ground-layer vegetation at several cedar plantations and hardwood forests in the Boso Peninsula. We also examined whether deer impacts were altered by light condition, soil water content and forest type (cedar and hardwood). Species richness of ground-layer vegetation was maximized at an intermediate level of deer density, suggesting an intermediate disturbance effect. This phenomenon was compatible with the observation that evergreen species, which were competitive dominants, decreased with increasing deer density, whereas less competitive deciduous species increased until herbivory was intermediate. As deer density increased, cover of ground-layer vegetation gradually decreased, but species unpalatable to deer increased in abundance, suggesting indirect positive effects of deer for unpalatable species. Cedar plantations tended to have greater species richness and ground-layer cover than hardwood forests with similar deer levels. Canopy openness, an indicator of light conditions, increased species richness of hardwood forests and ground-layer cover of cedar plantations, even under deer herbivory. Topographic wetness index, an indicator of soil water content, significantly increased the groundlayer cover of cedar plantations under deer herbivory. These results emphasize the importance of environmental productivity and forest type in the management of ground-layer vegetation experiencing deer overabundance.
Ungulate herbivory can fundamentally affect terrestrial vegetation at the landscape and regional levels, but its impact has never been analyzed from meta‐community perspectives. Here, we study a meta‐community of forest ground‐layer plants in a warm‐temperate region along a clear gradient of deer density interplaying with gradients of other environmental factors (forest type, sky openness and topographic wetness). Canonical corresponding analysis showed that deer density was the most important determinant of species distributions. These distributions conformed to a two‐directional filtering model, which selects for competitive species at low deer density but favours herbivory‐tolerant plants at high deer density, with these two directions counterbalancing each other when herbivory is intermediary. This resulted in a bi‐directionally nested meta‐community, in which local species richness was highest at intermediate levels of deer density, conforming also to the intermediate disturbance hypothesis. Our results suggest that herbivory can be the most important driver of meta‐community structure in mesic systems; this contrasts with the results of earlier studies conducted in harsh environments, where species sorting by abiotic factors at early life stages reduced the role of biotic interactions, including herbivory.
A global positioning system (GPS) collar recorded the locations of an adult female Japanese macaque over a 9-day period in a habitat with mixed suburban and rural land-uses in Chiba Prefecture, Japan. The GPS device acquired positions even in forested areas. The GPS data located the female mostly in forested areas, although the female had ranged through a habitat with inter-mingled fields, orchards, quarries, and residential areas. However, the GPS position acquisition rate was low compared to studies carried out on North American mammals. The GPS fixed a position in 20% of positioning attempts. When the collared female was tracked by radio-telemetry, almost all failures of the GPS to fix a position occurred in forest.
We have examined the seroprevalence of BDV in wild Japanese macaques (Macaca fuscata) in the peninsula (Chiba prefecture), Japan. Serum samples from macaques were examined by the ELISA, Western blot and immunofluorescence assays to detect the presence of serum antibodies that react specifically to BDV antigens. Among 49 investigated individuals, 6 (12.2%) showed positive reaction to BDV antigens. RT-PCR studies detected BDV sequences in brain tissue of one case among four seropositive cases examined. Sequence analysis revealed a high degree of genetic conservation between BDV sequences derived from Japanese macaques and those documented for other animal species. Nevertheless, phylogenetic analysis revealed unique differences between macaque and other species derived BDV sequences.
Temperature requirements for the breaking of seed dormancy and germination inPrimula sieboldii E. Morren and the annual surface-soil temperature regime in one of its natural habitats were investigated in order to clarify the germination responses determining the seedling emergence seasonality of the species. In a grassland nature reserve in an abandoned flood plain of the Arakawa River, natural seedling emergence of the species was shown to be restricted to mid-to late-spring before the closure of seasonal vegetational gaps, when the daily mean soil surface temperature reached about 15~ accompanied by large daily fluctuations of about 10~ Mature seeds collected in late June were never able to germinate at any constant temperature in the range of 8-40~ unless they had been previously subjected to moist-chilling treatment. The proportion of seeds which were released from dormancy increased with increasing duration of the moist-chilling treatment at 2~ 70-85 ~ of seeds becoming germinable at 16-28~ after 12 weeks of pretreatment at 2~ The thermal time required for the germination of the thus-pretreated seed population was 905-1690 Kh with a base temperature of around 5~ Fluctuating temperatures between 24~ and 16 or 12~ had a remarkable dormancy-breaking effect, inducing considerably quick germination in most of the seeds previously subjected to 2~ moist-chilling for 8 weeks.
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