| Plant community is one of the important components of an ecosystem.A plant community is a regular assemblage of many plant populations according to certain genetic and ecological principles in the long-term evolution process.The differences of regional environment and human activities would cause the variations of species composition,structure and function of plant communities.In recent years,with the excessive exploitation and unreasonable utilization of resources,the biodiversity conservation of plant communities are facing great challenges due to climate change,human activities and land use change.Shanxi Province,also known as the“Shanxi Plateau”,is situated in the eastern Loess Plateau in China.The complex topography and various climate and soil conditions have created favorable conditions for the development and survival of natural plant communities.However,the intensification of human activities,the exploitation of mineral resources and the irrational use of land resources have caused strong effects on the distribution,structure,composition and biodiversity of natural plant communities in Shanxi.Therefore,how to carry out systematic and practicable inventory and protection for the biodiversity is an urgent issue that should be paid more attention to and should be solved.In this study,the classification system of vegetation of Shanxi was first revised based on the field survey data with the unified investigation methodology and technical specification and according to the four classification units?vegetation type group,vegetation type,formation group and formation?as in the book“Vegetation of China”published in 1980.Meanwhile,the types and landscape patterns of plant functional types?PFTs?in the plateau were analyzed by use of the landscape pattern indices based on plant traits,thermal characteristics and water availability,together with the climatic and geographical conditions.Moreover,the diversity patterns,assembly mechanism,and main drivers of plant communities were analyzed and explored using the indices of species,phylogenetic and functional diversity at the different spatial and temporal scales,with the specific aim to answer the following scientific questions:?1?what major factors and processes are affecting the diversity patterns and assembly mechanisms;?2?weather there are a consistent diversity pattern and assembly mechanism between the woody and herbaceous plants;?3?how human activities and ecological restoration affected the composition and diversity patterns of plant communities.We hope that this systematic research can provide scientific theoretical basis for the future work for the investigation of vegetation,protection and utilization of biological resources,and biodiversity conservation.The main results were as follows:1.The vegetation of Shanxi was classified into 8 vegetation type groups,17 vegetation types,40 formation groups and 129 formations.Of all the formations,35 were newly found,including 2 broad-leaved forest formations,8 scrub and scrub grass formations,2 grass formations,3 steppe formations,5 meadow formations,and 15 swamp and aquatic formations.2.A total of 19 plant functional types?PFTs?were identified,i.e.,the cold warm-temperate evergreen coniferous forest,cold warm-temperate deciduous coniferous forest,warm-temperate evergreen coniferous forest,warm-temperate deciduous broadleaf forest,cold warm-temperate deciduous scrub,warm-temperate deciduous scrub,perennial grassland,perennial grass steppe,perennial grass meadow,perennial forb grassland,perennial forb steppe,perennial forb meadow,perennial legume steppe,perennial sedge meadow,annual forb meadow,fruit orchard,one year one ripe crop filed,one year two ripes crop filed,and two years three ripes crop filed.The cultivation crops were the dominant PFTs in Shanxi.The PFTs for forests and scrubs were dominated by the warm-temperate evergreen coniferous forest,warm-temperate deciduous broadleaf forest and warm deciduous scrub,respectively.The perennial grassland accounted for a large proportion of the herbaceous PFTs.The cultivation crops showed good integrity and connectivity,while other PFTs showed different degrees of fragmentation and discretization.The PFTs were significantly different among the three areas?except for cultivation crops?due to the heterogeneity of hydrothermal conditions and geographical environment.The PFTs across the whole region showed high landscape diversity.Compared with the other two areas,more fragmentation and higher landscape diversity were found in the central Shanxi.The landscape dominance was strong in north Shanxi.3.A total of 357 species belonging to 227 genera and 71 families were recorded in the 113 Pinus tabuliformis?Chinese pine?forests.There were no clear latitude patterns of?and?diversity for these forests.However,there were significant differences in the species richness?S?and phylogenetic diversity?PD?for them among the mountains due to the complex geographical conditions and high spatial heterogeneity.The S and PD were higher for natural Chinese pine forests than those of the planted forests.Both natural and stand factors had significant influence on the PD and net relatedness index?NRI?of the forests.The primary natural drivers were the topographic factors?slope and slope position?,followed by total soil phosphorus and precipitation.The topographic and soil factors had primary influence on the PD patterns in Mount Luliang,while the climatic and soil factors had strong effect on the PD patterns in Mount Taihang.The stand type and stand structure had strong effects on the PD patterns of the herbaceous plants.With the increase of altitude,there was an insignificant decreasing trend of?diversity(?total)for both the woody and herbaceous plants,but the change trends of their component replacement(?repl)and richness difference(?rich)were different.With the increase of latitude,?replepl showed an increasing trend,and?richich showed a declining trend for the woody plants;while they had declining and increasing trends respectively for the herbaceous plants.The geographical distance was the main influencing factor on the species and phylogenetic?diversity for the woody and herbaceous plants.This suggested that dispersal limitation was the key factor in community assembly at large spatial scale,especially in the complex terrain.4.The S,PD and funcitional richness?FRic?showed a monotonically increasing pattern along the altitudinal gradient for the forests in Mount Guandi,especially in the altitude above 1800 m.With the increase of altitude,?totalotal and?replepl showed increasing trends,and?richich showed declining trend for the forests.The species,phylogenetic and functional diversity patterns were significantly different between the woody and herbaceous plants.With the increase of altitude,the increasing trends of S and species diversity?H'?for the herbaceous plants were more obvious than those of the woody plants.The altitude and slope were the main influencing factors on the S of herbaceous plants;while the mean phylogenetic distance?MPD?and NRI were the most important influencing factors on the S of the woody plants.The result of NRI suggested that the relation among woody plants was mostly phylogenetic convergence,while the relation among herbaceous plants was mostly phylogenetic divergence.With the increase of altitude,the increasing trend of?totalotal for the woody plants was more obvious than that of the herbaceous plants.The altitude patterns of?replepl and?richich were different between the woody and herbaceous plants.For the woody plants,the?replepl and?richich showed a unimodal pattern and U-shaped pattern,respectively;while the?replepl and?richich showed a monotonically increasing and decreasing pattern respectively for the herbaceous plants.Environmental filtering played a key role in the assembly mechanism for the woody plants;however,environmental filtering and dispersal limitation jointly influenced the assembly mechanism for the herbaceous plants.5.The tourism development and human activities had caused severe ecological and environmental problems in the Lishan mountain meadow,such as the decrease of vegetation coverage,biodiversity loss,and soil and water losses,especially in the first transect?the severely disturbed area?.The dominant species of communities in this area had changed from perennial grasses to annual and anthropochorous plants.Following the implementation of ecological restoration project,the species and functional diversity generally showed a highly significant increase?P<0.01?,especially in the severely disturbed area,while the phylogenetic diversity had no significant change?P>0.05?.The species,phylogenetic and functional diversity was significantly different among the transects?P<0.01?before the restoration.However,the difference decreased and even disappeared following the restoration?P>0.05?.Due to the ecological restoration project,the change of species composition resulted in higher?diversity in the severely disturbed area.With the increase of distance from the pathways,the?diversity gradually decreased.The species composition,phylogenetic relationship and functional traits of communities were in relatively stable state in the undisturbed transect 4.The changes of T?total,P?totalotal and F?totalotal patterns were similar,but the relative roles of?replepl and?richich were different in the different disturbed areas.When the community was subjected to slight anthropogenic disturbance,?replepl had an important role in generating?diversity patterns.With the increase of disturbance intensity,both?replepl and?richich played important roles in generating?diversity patterns. |
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