Relative Contribution Of Local Factors Research Articles

Dispersal limitations and ecological adaptions shape phylogenetic diversity patterns of angiosperm woody plant communities along latitudinal and elevational gradients in East Asian islands

For centuries, ecologists have been captivated by the assembly of local communities from regional species pools, which gives rise to spatial diversity patterns. This study focused on hierarchical filtering process, which involves dispersal limitation and climatic constraint across regional to local scale, that underpins plant biodiversity patterns in East Asian islands, as one of the biodiversity hotspots with high endemicity. We used vegetation and species pool datasets of angiosperm woody plant communities collected from seven mountains across Japan to Taiwan to explore the relative contributions of local factors of individual plots, islands, latitude, elevation, and climatic variables related to the pattern of phylogenetic community assembly. Using linear regression and variation partitioning, we found that the island factor had the strongest filtering effect followed by latitude. Elevation and local factors (slope, aspect) accounted for a very small proportion of the variance in phylogenetic dispersion and community clade age between member species. Geographical factors involving islands, distance, and elevation had overriding filtering effects over climatic factors (minimum temperature of the coldest month, precipitation of the driest month) in shaping woody plant assembly patterns at the regional scale across East Asia islands. Tropical niche conservatism contributed to shaping woody plant communities in temperate region and high elevational regions on subtropical mountains as young and closely related species coexisted in those regions due to their adaptation to cold climates. This also explained the minor climate effects on species sorting in temperate mountains characterized by temperate-specific species pool which had already been filtered by cold climates. Inconsistent elevational phylogenetic diversity patterns in East Asia islands suggest a mountain-specific process that governs community assembly along elevational gradients, likely attributed to the location and climate of the mountain. These results suggest that historical factors (geohistorical isolation) related to islands and mountains contribute to in situ diversification that shaped plant diversity gradient from subtropical to temperate forests.

Dynamic healthy food accessibility in a rapidly urbanizing metropolitan area: Socioeconomic inequality and relative contribution of local factors

The socioeconomic status (SES) related disparities in healthy food accessibility have been heatedly debated. Theoretically, a gap remains in the literature about how healthy food accessibility changes over time and the relative contribution of local factors to the change. Methodologically, one main obstacle to this issue emerges on how to address the nested structural interactions among SESs across different levels. This paper first proposes a novel theoretical framework on healthy food accessibility from a spatiotemporally dynamic perspective. Guided by this framework, we employ the enhanced two-step floating catchment area model to examine the dynamic accessibility to four types of healthy food stores (i.e., vegetable markets, supermarkets, seafood markets, and fruit stores) from 2016 to 2018 across communities within the Hangzhou metropolitan area, China. The chain substitution method is further utilized to quantify the relative contributions of local factors, including population demand, healthy food supply, and transportation linkage. Multilevel regression is finally applied to analyze the associations between healthy food accessibility and the nested SESs across community and subdistrict levels. Results reveal that the dynamics of healthy food accessibility and the contributions of the local factors substantially vary depending on the type of healthy food stores and over time. Social inequality in accessibility to supermarkets and fruit stores is much greater than that to vegetable markets. The impact of the SES at the subdistrict level is greater than that at the community level. This study demonstrates a new methodological procedure and can offer new insights into healthy food accessibility in rapidly urbanizing metropolitan areas.