Plant Diversity Patterns And Biodiversity-productivity Relationships Of Steppe In Inner Mongolia

Relationship between biodiversity and ecosystem function is the kernel question in ecology.Ecosystems can provide services supporting human society in.terms of products and environments for living.Biodiversity is the key factor manipulating many ecosystem processes,such as ecosystem stability,productivity,carbon sequestration,and nutrient cycling,and so on.Therefore,biodiversity is the most crucial factor for achieving and maintaining ecosystem services.Presently,studies on examining relationships between biodiversity and ecosystem function and revealing their mechanisms have significances both in enriching ecological theory,and in guiding ecosystem management and environmental conservation.Grassland is one of the important terrestrial ecosystems.China is one of the leading countries relevance to grassland resources.Steppe in Inner Mongolia is located in the eastern part of Eurasian continent,which plays a significant role in constructing ecological defense in north China.However,grassland resources in this fegion degrade severely due to long time unreasonable utilization.Consequently,biodiversity of degraded grassland ecosystems decreases,which results in weakening ecosystem functions.Accordingly,it is necessary to carry out researches about relationships between biodiversity and ecosystem function in grassland.The study was conducted in Inner Mongolia on two different spatial scales,i.e.regional scale(steppe covering the whole region of Inner Mongolia)and landscape scale(typical steppe in Xilin river basin).Observation sites,total numbers of 218 and 92 for regional and landscape scales respectively,were set in the field.Data about plant species diversity,functional diversity,productivity,and soil properties were obtained by investigating plant communities,plant functional traits,and soil samples during field trip.Spatial patterns of plant species diversity and functional diversity on two different scales were analyzed.Responses of those patterns on environmental factors were determined by coupling with additional data,such as climate,and grazing intensity.Results showed that:1.On regional scale,communities derived from meadow steppe,typical steppe,and desert steppe were grouped into seven formations.Precipitation and temperature played an important role in relating with this classification;On landscape scale,communities of typical steppe were categorized into six associations.Soil properties and human activities,such as grazing,were the main factors driving the differentiation of typical steppe vegetation.2.On regional scale,both plant species diversity and functional diversity increased with the increase of longitude and latitude,demonstrating a spatial pattern of increase from south-west to north-east.The content of soil available nitrogen(AN)and annual precipitation were key factors resulting in the pattern of species diversity.Functional diversity pattern,however,was induced by different factors with the changes of criteria.Major environmental factors included mean annual temperature,annual precipitation,AN,and the content of soil total phosphorous(TP).3.On landscape scale,species and functional diversity of typical steppe were affected mainly by AN,the content of soil total nitrogen(TN),sheep density,and annual precipitation.Many indicators of species diversity were correlated positively with AN.TN showed positive relations with species diversity and with community leaf area.Moderate grazing was helpful to maintain species and functional diversity.4.On regional scale,species diversity was correlated significantly positively with productivity.With regard to functional diversity,the productivity indicated significantly positive relations with CWMheight,CWMLA,CWMleaf dry weight,CWMspecific LA,and Rao's quadratic entropy.Functional diversity contributed much more to the productivity than species diversity did.Both selection effect and complementarity effect determined the relationship between biodiversity and productivity.5.On landscape scale,species richness showed positive relation with productivity,significantly.In terms of functional diversity,CWMheight and CWMLA were correlated with productivity significantly and positively.Functional diversity,rather than species diversity,contributed a lot to the productivity.Productivity was dominated by both selection effect and complementarity effect.6.Plant height was the most important leading factor influencing productivity,regardless spatial scales.In conclusion,biodiversity of steppe in Inner Mongolia was affected by different environmental factors when different scales were concerned.Productivity of steppe communities,however,was primarily dominated by functional diversity in both regional and landscape scales.Plant height was the most significant functional trait determining community productivity.Selection effect was the leading mechanism maintaining above mentioned biodiversity-productivity relationships.