Neutral and accumulator species in determining the spatial structure of tree species at different spatial scales

In 2014,a 40-ha undisturbed plot was established in the Beijing Songshan Nature Reserve.The spatial distribution and spatial associations of five dominant tree species of different height classes were examined using spatial point pattern analysis and the effects of these species on local community diversity assemblages were examined using the ISAR method.The dominant species were characterized by an aggregated distribution at spatial scales of 0–50 m.At smaller spatial scales,trees in larger height classes had significant positive and negative effects on the diversity of the lower height classes.However,at larger spatial scales this effect was diminished.At small scales(0–10 m),accumulator species had positive effects on species diversity,maintained an over-representative proportion of diversity in their proximity,and supported the ecological niche theory.At the larger scale(10–50 m),neutral species were dominant and had positive effects on species diversity,though repeller species,which had negative effects on species diversity,also contributed to diversity.Neutral and accumulator species together determined local species diversity,but the relative importance of the two was closely related to spatial scale.A combination of the ecological niche theory and neutral processes together determines species coexistence and biodiversity of an undisturbed pine forest.

Elevational diversity gradients across seed plant taxonomic levels in the Lancang River Nature Reserve： role of temperature, water and the mid-domain effect

It remains unclear whether the elevational diversity gradients observed in seed plants across different taxonomic levels （family, genus, and species） are driven by the same macro-environmental variables. In this study, seed plant elevational distribution data from the Lancang River Nature Reserve （Yunnan, China） were used to investigate spatial patterns in diversity and their environ- mental correlates, comparing across taxonomic levels. Environmental variables included energy availability, climate seasonality and environmental heterogeneity. All taxonomic levels （family, genus, and species） were found to have strong elevational richness gradients, with the strength of the gradient weakening at higher taxonomic levels. Spatial patterns in richness were explained by a combination of contemporary environmental variables and the mid-domain effect at all taxonomic levels. The independent effects of temperature- and precipitation-related variables were similar in explaining geographical patterns of family, genus and species richness. Energy, seasonality and heterogeneity variables influenced seed plant spatial richness at different taxonomic levels in similar ways.

Multi-scale analysis on species diversity within a 40-ha old-growth temperate forest

In order to better explore the maintenance mechanisms of biodiversity, data collected from a 40-ha undisturbed Pinus forest were applied to the Individual Species-Area Relationship model(ISAR) to determine distribution patterns for species richness. The ecological processes influencing species abundance distribution patterns were assessed by applying the same data set to five models: a LogNormal Model(LNM), a Broken Stick Model(BSM), a Zipf Model(ZM), a Niche Preemption Model(NPM), and a Neutral Model(NM). Each of the five models was used at six different sampling scales(10 m×10 m, 20 m×20 m, 40 m×40 m, 60 m×60 m, 80 m×80 m, and 100 m×100 m). Model outputs showed that:(1) Accumulators and neutral species strongly influenced species diversity, but the relative importance of the two types of species varied across spatial scales.(2) Distribution patterns of species abundance were best explained by the NPM at small scales(10 m-20 m), whereas the NM was the best fit model at large spatial scales.(3) Species richness and abundance distribution patterns appeared to be driven by similar ecological processes. At small scales, the niche theory could be applied to describe species richness and abundance, while at larger scales the neutral theory was more applicable.