Zhiliang Yuan

Effects of Environmental and Spatial Heterogeneity on Tree Community Assembly in Baotianman National Nature Reserve, Henan, China

ABSTRACT The debate on species coexistence mechanisms never stops. The niche theory, neutral theory, and negative density dependence mechanism has been attracting considerable attention in recent years, but an integrated research on species coexistence mechanisms has rarely been conducted. In this study, a previous investigation at a plot in Henan Province was used as a basis to analyze the spatial structure of the community with principal coordinates of neighbor matrices (PCNM). Variance partitioning was used to analyze the effects of topography, soil, spatial, and stand density on species distribution. Results show that the community structure in the broad, medium, and fine scales generally showed a highly significant spatial structure. Topography, soil, spatial variables, and stand density explained 3.4, 11.7, 12.1 and 19.49% of species distribution, respectively. The aforementioned results suggest that spatial factor was an important factor that affects community structure. Species distribution was evidently influenced by environmental spatial heterogeneity. It had a very important function for density-dependent effects acting on species distribution. Niche theory, neutral theory, and negative density dependence mechanisms affected community building in different degrees.

Effects of Environment and Space on Species Turnover of Woody Plants across Multiple Forest Dynamic Plots in East Asia

Species turnover is fundamental for understanding the mechanisms that influence large-scale species richness patterns. However, few studies have described and interpreted large-scale spatial variation in plant species turnover, and the causes of this variation remain elusive. In addition, the determinants of species turnover depend on the dispersal ability of growth forms. In this study, we explored the large-scale patterns of woody species turnover across the latitude gradient based on eight large stem-mapping plots (covering 184 ha forest) in East Asia. The patterns of woody species turnover increased significantly with increasing latitude differences in East Asia. For overall woody species, environment explained 36.30, 37.20, and 48.48% of the total variance in Jaccard’s (βj), Sorenson’s, (βs), and Simpson’s dissimilarity (βsim). Spatial factors explained 47.92, 48.39, and 41.38% of the total variance in βj, βs, and βsim, respectively. The effects of pure spatial and spatially structured environments were stronger than pure environmental effects for overall woody species. Our results support the hypothesis that the effect of neutral processes on woody species turnover is more important than the effect of the environment. Neutral processes explained more variation for turnover of tree species, and environmental factors explained more variation for the turnover of shrub species on a large scale. Therefore, trees and shrubs should be subjected to different protection strategies in future biodiversity conservation efforts.

How do similarities in spatial distributions and interspecific associations affect the coexistence of Quercus species in the Baotianman National Nature Reserve, Henan, China

Abstract Congeneric species often have similar ecological characteristics and use similar resources. These similarities may make it easier for them to co‐occur in a similar habitat but may also lead to strong competitions that limit their coexistence. Hence, how do similarities in congeneric species affect their coexistence exactly? This study mainly used spatial point pattern analysis in two 1 hm2 plots in the Baotianman National Nature Reserve, Henan, China, to compare the similarities in spatial distributions and interspecific associations of Quercus species. Results revealed that Quercus species were all aggregated under the complete spatial randomness null model, and aggregations were weaker under the heterogeneous Poisson process null model in each plot. The interspecific associations of Quercus species to non‐Quercus species were very similar in Plot 1. However, they can be either positive or negative in different plots between the co‐occurring Quercus species. The spatial distributions of congeneric species, interspecific associations with non‐Quercus species, neighborhood richness around species, and species diversity were all different between the two plots. We found that congeneric species did have some similarities, and the closely related congeneric species can positive or negative associate with each other in different plots. The co‐occurring congeneric species may have different survival strategies in different habitats. On the one hand, competition among congenerics may lead to differentiation in resource utilization. On the other hand, their similar interspecific associations can strengthen their competitive ability and promote local exclusion to noncongeneric species to obtain more living space. Our results provide new knowledge for us to better understand the coexistence mechanisms of species.

Stand Structure and Substrate Diversity as Two Major Drivers for Bryophyte Distribution in a Temperate Montane Ecosystem

Elucidating the major drivers of bryophyte distribution is the first step to protecting bryophyte diversity. Topography, forest, substrates (ground, tree trunks, roots, rocks, and rotten wood), and spatial factor, which factors are the major drivers of bryophyte distribution? In this study, 53 plots were set in 400 m2 along the elevation gradient in Xiaoqinling, China. All bryophytes in the plots were collected and identified. Regression analysis was used to examine the relationship between bryophyte and substrate diversity. We compared the patterns of overall bryophyte diversity and diversity of bryophytes found on the ground, tree, and rock along elevational gradients. Canonical correspondence analysis was applied to relate species composition to selected environmental variables. The importance of topography, forest, substrates, and spatial factors was determined by variance partitioning. A total of 1378 bryophyte specimens were collected, and 240 species were identified. Bryophyte diversity was closely related to substrate diversity. The overall bryophyte diversity significantly increased with elevation; however, the response varied among ground, tree, and rock bryophytes. Tree diversity and herb layer were considered important environmental factors in determining bryophyte distribution. Species abundance was best explained by stand structure (17%), and species diversity was best explained by stand structure (35%) and substrate (40%). Results directly indicated that substrate diversity can improve bryophyte species diversity. The effects of micro-habitat formed by stand structure and substrate diversity were higher than those of spatial processes and topography factors on bryophyte distribution. This study proved that the determinant factors influencing bryophyte diversity reflect the trends in recent forest management, providing a real opportunity to improve forest biodiversity conservation.

Drivers of Macrofungi Community Structure Differ between Soil and Rotten-Wood Substrates in a Temperate Mountain Forest in China

The effects of environmental and dispersal processes on macrofungi community assembly remain unclear. Further, it is not well understood if community assembly differs for different functional guilds of macrofungi, e.g., soil and rotten-wood macrofungi. In this study, using 2433 macrofungi sporocarps belonging to 217 species located within a forest dynamics plot in temperate mountain forest (China), we examined the explanatory power of topography, spatial eigenvectors (representing unknown spatial processes, e.g., dispersal), plant community, and light availability for local spatial variation in the macrofungi community through variance partitioning and partial least squares path modeling. We found spatial eigenvectors and light as the most important factors for explaining species richness and composition of macrofungi. Light was negatively correlated with species richness of macrofungi. Furthermore, species richness and composition of soil macrofungi were best explained by light, and species richness and composition of rotten-wood macrofungi were best explained by spatial eigenvectors. Woody plant community structure was not an important factor for species richness and composition of macrofungi. Our findings suggest that spatial processes, perhaps dispersal limitation, and light availability were the most important factors affecting macrofungi community in temperate deciduous broad-leaved forest. Major differences in influencing factors between soil and rotten-wood macrofungi were observed, with light as the major driver for soil macrofungi and unknown spatial processes as the major driver for rotten-wood macrofungi. These findings shed new light to the processes shaping community assembly in macrofungi in temperate deciduous broad-leaved forest and point to the potential importance of both intrinsic dynamics, such as dispersal, and external forcing, such as forest dynamics, via its effect on light availability.

Carbon storage dynamics ofPinus armandiiforest at different diameter levels based on tree ring data in the Baotianman National Nature Reserve, central China

Based on tree-ring analysis, Pinus armandii trees were divided into three classes (A, DBH≤15 cm; B, 15 cm 25 cm) to study carbon storage dynamics of Pinus armandii populations in the Baotianman National Nature Reserve. Comparison of these three diameter classes revealed three major findings. (1) The carbon storage of P. armandii trees in small DBH class A, intermediate class B and large class C were 2.757, 9.211 and 15.408 t/hm2, respectively, with corresponding annual carbon increments of 0.0685, 0.1535 and 0.136 t/hm2. (2) The intermediate class (15 cm 25 cm) had the greatest contribution to total carbon storage of the P. armandii forest. Tree mortality was the main factor limiting carbon storage within small and intermediate DBH class P. armandii trees, whereas physiological growth was the restrictive factor for large DBH class trees. Our results demonstrate that dendrochronological analysisis is an important method to evaluate growth trends and to assess the carbon storage dynamics of the P. armandii forest in the Baotianman National Nature Reserve.

Correlation analysis of soil and species of different life forms in Baotianman Nature Reserve

The plant community renewal process is influenced by the vertical structure of forests and soil is an important factor affecting community succession. This study investigated the relationships between soil and different species of each forest layer in the Baotianman Nature Reserve. The Canonical Redundancy Analysis(RDA) was used to explore the relationship between the surface soil and deep soil and the distribution of different forest layer species. Principal Component Analysis(PCA) was conducted on the properties of the two soil layers and a Generalized Additive Model(GAM) was used to fit the relationship between the main species of trees, small trees and shrubs with each principal component. The results were as follows:(i) the surface soil and deep soil jointly explained 40.52%, 40.46%, 37.17% and 42.14% of the distribution of all species, trees, small trees and shrubs, respectively. The corresponding values in the surface soil independently were 14.68%, 17.32%, 10.61% and 17.32%, and in the deep soil independently were 18.24%, 17.22%, 18.8% and 18.84%.(ii) The 15 soil properties of PCA showed that the first four principal components represented 38.02%, 14.41%, 9.06% and 5.79% and the cumulative contribution rate was 67.28%.(iii) The GAM fitting results showed the different forest vertical layers that were associated with the four principal components: the tree layer of D2 was 0.63%–9.07%, the little tree layer of D2 was 1.41%–1.41% and the shrub layer of D2 was 1.91%–1.91%. These results showed that soil properties play an important role on species distribution in the Baotianman Nature Reserve. The nutrient content of topsoil is greater than the deep soil, but that does not necessarily mean a stronger relationship with the forest layer species distribution than the deep soil. Future research should focus on the combined effects of the soil properties and the characteristics of the each layer species, with special attention to the role of the species in the deep soil. Different intra- and inter-layer species may compete for soil nutrients, which may promote species coexistence and resource partitioning.

Macrofungal species distributions depend on habitat partitioning of topography, light, and vegetation in a temperate mountain forest

The habitat partitioning hypothesis provides a conceptual framework for explaining the maintenance of plant and animal diversity. Its central tenet assumes environmental conditions are spatially structured, and that this structure is reflected in species distributions through associations with different habitats. Studies confirming habitat partitioning effects have focused primarily on spatial distributions of plants and animals, with habitat partitioning hypothesis under explored for macrofungi. Here, we examined the sporocarps of macrofungi in a 5-ha forest dynamics plot in China. We used four different methods to define microhabitats for habitat partitioning analyses based on topography, understory light availability, plant community, or a combination of these factors, and analyzed the effect of microhabitat partitioning on epigeous macrofungal community. Our results showed that the characteristics of the macrofungal assemblages varied among the habitats. A total of 85 species examined were associated with one or more of the habitat types (85/125, 68%). The factors related to the sporocarp composition differed among the various microhabitats. Our findings suggest that different microhabitats favor occurrence of different macrofungal species, and sporocarps -environment relation varied among the different microhabitats at this temperate mountain forest locality. These findings shed new light to the biodiversity conservation in macrofungi in temperate deciduous broad-leaved forest and point to the potential importance of microhabitat partitioning for sporocarp formation.

Effects of Topographical Heterogeneity and Dispersal Limitation on Species Turnover in a Temperate Mountane Ecosystem: a Case Study in the Henan Province, China

Species turnover patterns can be inconsistent due to differences in the dispersal ability of different growth forms. Here, species of trees, shrubs, herbs, and bryophytes in the Xiaoqinling National Nature Reserve in China were analyzed to determine patterns of species turnover along an elevation and spatial gradient. Variance partitioning was used to assess the relative contribution of topographic heterogeneity and dispersal limitation to species turnover. Our results suggest that the effect of dispersal limitation is more important than topographic heterogeneity on species turnover in temperate mountane ecosystems in the study area. Dispersal limitation has a greater effect on trees species turnover than on shrubs, herbs or bryophytes species turnover.