Species assembly and niche differentiation were studied, and future species composition was predicted by simple Markov models, in an old-growth deciduous forest at the Ogawa Forest Reserve in central Japan. The dominant species in our 6ha study site are Quercus serrata, Fagusjaponica, and F. crenata.An ordination by population parameters revealed four different combination 3 of life forms and regeneration niches. Cluster analysis based on interspecific spatial correlation revealed three groups of species. The species in cluster A, such as F. japonica, occurred at the bottom of the valley, while those in cluster B, such as Q. serrata, occurred along ridges. Species in cluster C, such as F. crenata, did not show any particular habitat preference. Clusters B and C were further divided into three smaller clusters (a-c). Both clusters Ba and Bb included shade intolerant species. Species in cluster Ba had large clump sizes (> 1500 m2), reflecting regeneration following large-scale disturbances. Species in cluster Bb had smaller clump sizes (< 400 m 2) reflecting regeneration following local disturbances. Clusters Caand Cb mainly included shade tolerant species and shade intolerant species, respectively. Markov models predicted that shade intolerant species, particularly those in cluster Ba, would be eliminated. Thus, species coexist by differentiation of both habitats and regeneration niche in this forest community. Some species such as Quercus serrata, however, regenerate following large-scale disturbances or human activity.

No abstract

To investigate synchronized annual fluctuation of seed production and its advantage for regeneration at the community level, for nine years (1987–1995) we monitored the flowering, seed production, and seedling emergence of the 16 principal tree species in a temperate deciduous forest, Ogawa Forest Reserve, in central Japan. We found that the species with higher synchronized flowering within a population had larger fluctuation of annual seed production at the population level. The coefficient of concordance of flowering and the coefficient of variation of annual seed production were continuously distributed among species, making it difficult to distinguish masting from nonmasting species. The annual seed production patterns of the 16 species were classified, by cluster analysis, into groups that synchronize their fluctuation of annual seed production. This analysis showed a highly synchronized annual seed production, not only among congeneric species, but also among species of different families. Although our results have some insufficiency of statistical significance, they did show that predator satiation, both in a population and a guild, effectively operated for many species to enhance seed survival at the pre‐dispersal stage. They also showed that pollination efficiency was likely to be operating at the population level for half of the wind‐pollinating species. However, generalist predator satiation at the postdispersal seed stage may not operate in a simple, detectable manner in this species‐rich forest community. It is highly probable that there are combined effects of several factors: limited weather triggers for flowering, common flowering physiology among taxonomically related species, and the ecological advantages at the population and guild levels, may cause multiple species to have synchronized fluctuation patterns of seed production.

Although species with large area requirements are sometimes used as umbrella species, their general utility as conservation tools is uncertain. We surveyed the species diversity of birds, butterflies, carabids, and forest-floor plants in forest sites across an area (1,600 km2) in which we delineated large breeding home ranges of Northern Goshawk (Accipiter gentilis). We tested whether protection of the home ranges could serve as an effective umbrella to protect sympatric species of the four taxa. We also used an empirical habitat model of occupancy of home range to examine mechanisms by which the Northern Goshawk acts as an umbrella species. Among species richness, abundance, and species composition of the four taxa, only abundance and species composition of birds differed between sites located inside and outside home ranges, which was due to greater abundance of bird species that were prey of Northern Goshawks inside the home ranges. Thus, although home range indicated areas with high abundance of certain bird prey species, it was not effective as an indicator of the species diversity of all four taxa. We also did not find any difference in species richness, abundance, and species composition between sites predicted as occupied and unoccupied using the habitat model. In contrast, when we selected sites on the basis of each habitat variable in the model, habitat variables that selected sites either in agricultural or forested landscapes encompassed sites with high species richness or particular species composition. This result suggests that the low performance of the Northern Goshawk as an umbrella species is due to this species' preference for habitat in both agricultural and forested landscapes. Species that can adjust to changes in habitat conditions may not act as effective umbrella species despite having large home ranges.

Although we know that rainfall interception (the rain caught, stored, and evaporated from aboveground vegetative surfaces and ground litter) is affected by rain and throughfall drop size, what was unknown until now is the relative proportion of each throughfall type (free throughfall, splash throughfall, canopy drip) beneath coniferous and broadleaved trees. Based on a multinational data set of >120 million throughfall drops, we found that the type, number, and volume of throughfall drops are different between coniferous and broadleaved tree species, leaf states, and timing within rain events. Compared with leafed broadleaved trees, conifers had a lower percentage of canopy drip (51% vs. 69% with respect to total throughfall volume) and slightly smaller diameter splash throughfall and canopy drip. Canopy drip from leafless broadleaved trees consisted of fewer and smaller diameter drops (D50_DR, 50th cumulative drop volume percentile for canopy drip, of 2.24 mm) than leafed broadleaved trees (D50_DR of 4.32 mm). Canopy drip was much larger in diameter under woody drip points (D50_DR of 5.92 mm) than leafed broadleaved trees. Based on throughfall volume, the percentage of canopy drip was significantly different between conifers, leafed broadleaved trees, leafless broadleaved trees, and woody surface drip points (p ranged from <0.001 to 0.005). These findings are partly attributable to differences in canopy structure and plant surface characteristics between plant functional types and canopy state (leaf, leafless), among other factors. Hence, our results demonstrating the importance of drop‐size‐dependent partitioning between coniferous and broadleaved tree species could be useful to those requiring more detailed information on throughfall fluxes to the forest floor.