Functional diversity of Cercidiphyllum japonicum, communities in the Shennongjia Reserve, central China

Functional diversity is significant to ecological processes of plant communities. We analyzed the variation of functional diversity of endangered species, Cercidiphyllum japonicum, communities along an elevational gradient in the Shennongjia Reserve, central China. Sixty plots of 10 9 20 m from 1,350 to 2,050 m were set up and species composition, traits and environmental variables were measured and recorded. These data were analyzed using five functional diversity indices, functional attribute diversity, modified functional attribute diversity, plot based functional diversity, community based functional diversity and Rao＇s functional diversity indices（Rao＇s index）,Functional diversities of C. japonicum communities were rich and varied greatly. Functional diversity declined nonlinearly with increasing elevation. Functional diversity was significantly correlated with species richness and heterogeneity. Elevation was a key environmental variable influencing functional diversity and species diversity. The five functional diversity indices were all effective for measuring functional diversity of communities. Functional diversity can be used as an indicator of conservation efficiency of endangered species such as C. japonicum.

Examining residual spatial correlation in variation partitioning of beta diversity in a subtropical forest

Aims The relative roles of ecological processes in structuring beta diver-sity are usually quantified by variation partitioning of beta diversity with respect to environmental and spatial variables or gamma di-versity.However,if important environmental or spatial factors are omitted,or a scale mismatch occurs in the analysis,unaccounted spatial correlation will appear in the residual errors and lead to re-sidual spatial correlation and problematic inferences.Methods Multi-scale ordination(MSO)partitions the canonical ordination results by distance into a set of empirical variograms which charac-terize the spatial structures of explanatory,conditional and residual variance against distance.Then these variance components can be used to diagnose residual spatial correlation by checking assump-tions related to geostatistics or regression analysis.In this paper,we first illustrate the performance of MSO using a simulated data set with known properties,thus making statistical issues explicit.We then test for significant residual spatial correlation in beta diversity analyses of the Gutianshan(GTS)24-ha subtropical forest plot in eastern China.Important Findings Even though we used up to 24 topographic and edaphic variables mapped at high resolution and spatial variables representing spa-tial structures at all scales,we still found significant residual spatial correlation at the 10 m×10 m quadrat scale.This invalidated the analysis and inferences at this scale.We also show that MSO pro-vides a complementary tool to test for significant residual spatial correlation in beta diversity analyses.Our results provided a strong argument supporting the need to test for significant residual spatial correlation before interpreting the results of beta diversity analyses.

Development of plant communities after restoration of the Antaibao mining site, China

To investigate the dynamic changes in the artificial vegetation in an abandoned mining site,we analyzed the re lationships among community types,environmental variables and community structure in the process of vegetation restoration in the Antaibao mining site,China by survey of the communities and use of biological dating methods.By means of the quantitative classification method(two-way indicator-species analysis,TWINSPAN)and the ordination technique(de-trended correspondence analysis,DCA;and de-trended canonical correspondence analysis,DCCA),the plant communities were classified into seven groups:community I,Robinia pseudoacacia+Pimus tabulaeformis-Caragana kor-shinskii-Agropyron cristatum;community II,Robinia pseudoacacia-Hippophae rhamnoides-Artemisia capil-laries;community II,Ulmus pumila-Elaeagmus angu-stifolia-Artemisia capillaries;community IV,Caragana korshinskii-Agropyron cristatum+Artemisia capillaries;community V,Hippophae rhamnoides-Elymus dahur-icus;community VI,Elaeagnus angustifolia+Hippophae rhamnoides-Brassica jucea;community VII,Hippophae rhammoides+Elaeagnus angustifolia-Salsola collina.We conclude that the community types and diversity are mainly influenced by the succession time and the soil organic matter content.The forest community is more adaptable to the special inhabitation than the shrub community.

Spatial hints of forest ecotone indicating forest succession, a case of larch forests in Baihuashan Reserve, north China

In cold or alpine areas of northern China,birch forests and larch forests are the two primary forest types.These forests are also characteristic of a south branch of boreal forests in Asia.Some ecologists argue that larch forests can replace birch forests,but this still remains a question due to fragmentary or short observations.The ecotone between a larch forest patch and a birch forest patch is the arena in which the two species interplay and compete with each other,and studies of these areas are meaningful to understanding forest succession.In the alpine area of the Baihuashan Reserve,northern China,we sampled a larch-birch forest ecotone with eight plots in four transects and then analyzed population structures of larches and birches.The results show that the edges of the larch forest patch are composed of many larch saplings or young trees,but the edges of the birch forest patch are mainly composed of old birches.Across the ecotone,the larches,on average,are taller than the birches.These facts suggest that larch saplings can permeate into birch forest patches,probably by seed dispersal,germination,success-ful competition and growth,but birch saplings cannot permeate into larch forest patches.Therefore,on the ecotone,larch forest patches can steadily expand by unceasing permeation into birch forest patches,whereas birch forest patches progressively recede due to ultimate death of the old and poor recruitment of the young.Larch forest patches replace birch forest patches in a stepwise manner,causing succession from birch forests to larch forests.This study not only confirms that larch forests can naturally replace birch forests,but also introduces a simple and reliable method,employing spatial hints,to study forest succession.Additionally,the findings are of benefit to cultivation or development of larch forests in cold or alpine areas of the North Temperate Zone,which can be a huge carbon sink.

Quartered neighbor method: A new distance method for density estimation

Quantitative data are essential to an appro-priate characterization of vegetation.In the past few years,considerable attention has been paid to vegetation sampling techniques.A number of methods have been developed for plant density estimations that utilize spacing distances instead of fixed-area quadrats.In this paper,we review the main distance methods for estimating density and propose a new distance method denominated the quartered neighbor method.In this method,the sampling point is considered the center,and the area around it is divided into four quadrants.The distance from the closest individual in each quadrant to its closest neighbor in the same quadrant is measured,and the average of them is the distance we need.It is actually an integration of two old distance methods,the nearest neighbor method,and the point-centered quarter method.With our new method and an old distance method(the point-centered quarter method),we calculated the average spacing distances of the Larix principis-rupprechtii population in the larch forests of the Donglingshan Mountain.Comparing the two methods with the quadrat method,we found they were almost the same in accuracy,but the precision of the new one was better.Meanwhile,it is adequate in sampling intensity and adaptable for general use in rapid ecological survey work.

Quantitative analysis of endangered Acanthopanax senticosus communities in Dongling Mountain of Beijing

Based on the survey of community plots,a quantitative analysis of endangered Acanthopanax senticosus communities in Dongling Mountain was performed with two way indicator species analysis(TWINSPAN),detrended correspondence analysis(DCA)and canonical correspondence analysis(CCA).The communities of A.senticosus were classified into 9 types by TWINSPAN and the results were validated by DCA.On the DCA graph,the first axis reflected the gradient of altitude and the second axis reflected the aspect and slope.Most of A.senticosus were distributed in the thick forests at a high altitude with little light.With the exception of being a dominant species of shrub layers in a few communities,A.senticosus has a relatively scarce distribution.In accordance with DCA,the results of CCA also show the trend that the distribution of A.senticosus communities varied along with the gradient change of environmental factors.Altitude and light are the main factors affecting A.senticosus growth.

Application of self-organizing neural networks to classification of plant communities in Pangquangou Nature Reserve, North China

Vegetation classification is an important topic in plant ecology and many quantitative techniques for classification have been developed in the field.The artificial neural network is a comparatively new tool for data analysis.The self-organizing feature map(SOFM)is powerful tool for clustering analysis.SOFM has been applied to many research fields and it was applied to the classification of plant communities in the Pangquangou Nature Reserve in the present work.Pangquangou Nature Reserve,located at 37°20′–38°20′ N,110°18′–111°18′ E,is a part of the Luliang Mountain range.Eighty-nine samples(quadrats)of 10 m×10 m for forest,4 m×4 m for shrubland and 1 m×1 m for grassland along an elevation gradient,were set up and species data was recorded in each sample.After discussion of the mathematical algorism,clustering technique and the procedure of SOFM,the classification was carried out by using NNTool box in MATLAB(6.5).As a result,the 89 samples were clustered into 13 groups representing 13 types of plant communities.The characteristics of each community were described.The result of SOFM classification was identical to the result of fuzzy c-mean clustering and consistent with the distribution patterns of vegetation in the study area and shows significant ecological meanings.This suggests that SOFM may clearly describe the ecological relationships between plant communities and it is a very effective quantitative technique in plant ecology research.