| The Tianmu Mountain Natural Reserve is the first natural reserve in Zhejiang province,which is rich in resources and unique in the protection of indigenous species in the natural reserve system of China.Environmental change affects the structure and function of the natural ecosystems.The arthropod community structure and species diversity in Tianmu Mountain were also greatly affected by environmental changes.It is important to investigate a community’s composition,species structure,and environmental impacts.Species diversity is an essential indicator of the community composition structure.It not only directly reflects the level of community organization,but also indirectly reflects the community function.Arthropod communities are sensitive to environmental changes,so they can be used to some extent to monitor the health of the ecosystems in which they live.To study the patterns of the arthropod community and the effects of environmental conditions on arthropod community structure,we carried out field research in Tianmushan Nature Reserve in 2017 and the supplementary investigation was carried out in 2019.The experimental plots(50 m*50 m)were set and divided into 3 types,(a)elevation I(588～598m),(b)elevation II(1098～1148m),and(c)elevation III(1233～1287m).The experimental plots included 4 forest types distributed on different elevations.The broad-leaved evergreen forest(F1)located at elevation I;the mixed broad-leaved evergreen-deciduous forest(F2)and the mixed broad-leaved evergreen-deciduous forest(F3)located at elevation II;the deciduous forest(F4)located at elevation III.The sampling seasons were April,August,and November.A total of 1325 samples of arthropods from the arboreal layer,1345 samples from the shrub layer,and 554 samples from the real soil layer were collected.The diversity index,Similarity index,Dominant taxa of arthropod community structure,Pearson and Spearman correlation,and arthropods and plant community structure were analyzed using the standard statistical methods.The soil environmental data matrix including the soil properties and altitude,and the vegetation data matrix was established.The results showed that(1)the soil p H values did not change significantly among the different sites;(2)soil water content and soil bulk density varied with elevation changes;(3)the soil organic matter,alkaline nitrogen and total nitrogen were higher at the low elevations and lower at the higher elevations;(4)soil total phosphorus were higher in the lower elevation and lower in the high elevation;the arthropod community structure was more sensitive to soil total phosphorus;(5)soil available phosphorus fluctuated greatly along elevation gradient;(6)soil bulk density at the elevation II in forest F2 was lower than that in the F3 at the same elevation,and the soil available nitrogen was higher at the elevation III and lower at the elevation II;(7)the S?renson value of the similarity index between the dominant species in the above-ground community was 0.5 for trees,0.3 for shrubs,and 0.4 for the herbaceous layer,indicating that the species composition in the above-ground community in the Tianmu Mountain Nature Reserve was quite different with higher community heterogeneity,higher frequency of dominant species and uniform species distribution.The seasonal trends of community structure and species diversity of above-ground arthropods were as follows: in April,the arthropod community structure and number of taxa(class or order or family)in the tree layer were more abundant because they were less affected by the environmental variations(e.g.,rainfall).Due to the monsoon season in August,the arthropod community structure and species diversity in the arbor layer were highly affected.Elevation II showed higher arthropod species diversity in the arbor layer because the environmental variations less affected the arthropod community structure than those at elevations I and III.In November,the community structure and diversity of the arthropod taxa in the shrub layer showed marginally abundant compared to those in April and August.The richness of the arthropod taxa in the herbaceous plant layer decreased with the increase in elevation.The most abundant arthropod community structure appeared at elevation II compared to elevations III and I.The seasonal variation trends of arthropod community structure and species diversity in the true soil layer were as follows: in April,the arthropod taxa richness in the true soil layer of each plot decreased with the elevation increase.The number of arthropod families was low,the distribution of the dominant taxa was relatively uniform,and the taxa similarity between forest plots was low.The Shannon-Wiener diversity index H values and the taxa richness index M were lower at the highest elevation.In August,the herbaceous arthropod community structure showed more abundance because the arbor layer arthropods tended to take refuge in the soil in the rainy season.In November,the number of soil arthropod families was high,and the Shannon-Wiener diversity index H was higher at elevation I and lower at other heights.The variations of environmental factors were directly correlated with the arthropod community structures and diversity.Soil arthropod diversity was negatively correlated with plant species diversity,soil water content,and total soil phosphorus.The distribution of soil arthropods positively correlated with the elevation,soil organic matter,and soil water content.The results of this study might provide theoretical and technical reference for the scientific evaluation of ecosystem health in Tianmushan Nature Reserve,and also provide relevant empirical basis for ecosystem protection in this area. |
