A Research Of The Relationship Between Diversity And Productivity From Community And Species Level Biomass

In recent decades,the loss of species diversity is very common due to environmental pollution,human disturbance and other factors.Species diversity plays an important role in maintaining structural stability and functional integrity of ecosystems.Thus the research on the influence of diversity loss on system stability and function has been a hot spot of ecological research.The effects of biodiversity can be reflected by studying the relationship between diversity and productivity to some extend.The relationship between diversity and productivity mainly has four patterns: Positive correlation,negative correlation,single-peak effect and no significant correlation.Among them,the positive correlation pattern has received much more attention.Complementarity effect and sampling effect are the two main mechanism explaining their positive correlation.This is mainly because that the relationship between them is affected by many biological and environmental factors,which makes the relationship more complex.The previous research mainly explains the positive relationship between them from a perspective view of community,and can not explain the other three patterns.This research attempts to explain the relationship based on the response of individual species to diversity.In this study,I want to explain the correlation between diversity and productivity both from the responses of community and individual species levels production to diversity in a terrestrial and an aquatic plant experiment.Moreover,we want to prove our hypothesis in a species loss experiment.I conducted three experiments to prove my hypotheses,and the experimental process and results are described as follows:(1)In this study,we determined the biodiversity effects on community productivity,species level plant mass and carbon and nitrogen metabolism of eight submerged plants.The results showed that the community level biomass was positively correlated to plant species richness although the species level plant mass of individual species responded differently to overall plant species richness.Namely,only one plant mass positively correlated to species richness and those of the others decreased or showed no significant correlation with the increase of species richness.The soluble proteins of most macrophytes were positively correlated to species richness;however,both the free amino acid and soluble carbohydrate of the plants were negatively or not significantly correlated to species richness.These results indicated that the selection effects might dominate in our aquatic communities and the negative impacts of biodiversity on C and N metabolism of the macrophytes increased with the increase of species richness might result from the strong competiveness among the studied species.(2)Based on the results of the aquatic plant experiment,we determined the effects of biodiversity loss of one species on community productivity,species level plant mass and carbon and nitrogen metabolism of eight submerged plants.The results showed that,compared the community with no diversity loss,the community biomass increased when the dominant species(Ceratophyllum demersum)excluded while the community biomass with one non-dominant species loss showed no significant differences with that of the community with no diversity loss.For individual species level mass,soluble proteins,free amino acid and soluble carbohydrate of the submerged species in communities with species loss demonstrated various promoting,inhibiting or relative stable effects compared with that in communities with no species loss.(3)A field experiment from 2008 to 2013 and a pot experiment in 2014 were conducted to study the effects of plant invasion on the relationship between diversity and productivity and the response of species level plant mass to species richness in native and invaded communities.The community level biomass was negatively correlated to plant species richness in invaded communities while the same relationship was positive in native communities.The species level plant mass of individual species responded differently to overall plant species richness in the native and invaded communities,namely,most of the species' plant mass increased in native communities,but decreased in invaded communities with increasing species richness.The complementarity or selection effects might dominate in native communities while competition effects might dominate in invaded communities.We can presume that the complementarity or selection effects might dominate in native terrestrial communities while competition effects might dominate in invaded terrestial communities and selection effect might dominate in native aquatic communities.The complementarity or selection effects in native terrestrial communities could be changed by plant invasion resulting in the positive relationship between biodiversity and production shaping to negative relationship because of the occurrence of strong competition among species.Accordingly,the analyses of the plant species level response to species richness might contribute to explaining the relationship between diversity and productivity compared to the analyses of community biomass response to biodiversity.The pattern of diversity and productivity can be well explained by analyzing the responses of each individual plant species mass to diversity,and I argue that the overall pattern of community biomass is determined by tradeoffs between the plant masses of all species in local communities.The community biomass of the whole community is greatly promoted when the dominant species was exclude,which might because the competition effect exerted by C.demersum is weakened.The relation between diversity and productivity is well explained by measuring the each individual plant species mass in different species richness whatever the relationship is affected by any biotic and abiotic factors.Accordingly,I think that the analyses of the plant species level response to species richness might contribute to explaining the relationship between diversity and productivity.