The Relationship Between Biodiversity And Ecosystem Function In Danxia Herbaceous Communities On The Lithoid Cliff

Field observational study on the relationship between biodiversity and productivity was taken on more than 300 plots in Danxia communities of Wuyishan,Liancheng and Taining in Fujian province,southeast China.With the steps of species identification,observational coverage value data collection,growing type seperation and biomass measurement,the above-ground biomass value of the plots was estimated indirectly,which was taken to represent productivity of the plots.Regression analysis supplied evidence for four mainstream but far different hypotheses on biodiversity-ecosystem function relationship;the relevant factors included all-species and "visible" species(species whose coverage value is larger than 15%) richness,photic functional diversity,different saturation of experimental communities as well as the sunlight variation.The results were as follow:(1) The investigation results of Danxia communities' shows that,there were vascular plants 63 families,114 genera and 135 species in the plots of experimental area Wuyishan,61 families,118 genera and 151 species in the plots of experimental area Liancheng,76 families, 151 genera and 197 species in the plots of experimental area Taining(not contain the contrasting sites).The most common families of Danxia communities in Fujian province were Selaginellaceae,Poaceae,Gesneriaceae,Urticaceae,Dryopteridaceae and Polypodiaceae.Selaginella tamariscina,Neyraudia montana,Oreocharis maximowiczii,Selaginella moellendorfii and Hemerocallis citrine are the most common dominant species.(2) The relationship between all-species richness and plot productivity of Taining was accorded with the redundancy hypothesis(S model),while those of Wuyishan and Liancheng were accorded with the idiosyncratic hypothesis.This difference could be brought by the different saturation of communities,the ratio between mean plot species richness and Gleason diversity index of all the plots(N_p/D) in Wuyishan was only 0.39,while in Liancheng and Taining,the ratio is 0.49 and 0.43.What's more,the individual saturation of Taining's plots is higher than that of Liancheng's.(3) The relationships between "visible" species richness and productivity were all accorded with the "rivet" hypothesis,which could be explained as the result of the definition of species playing an important role in ecosystem functions,by "rivet" hypothesis. (4) With the co-analyzing of sunlight level and photic functional diversity as "hidden treatments" insisted by the null hypothesis,these correlating factors of productivity and its stability were corroborated.Concretely,compared with the spatial variation of sunlight level in the valleys,it was lower on the top of the Danxia peaks,so was the variation of plot productivity in site Zhuangyuan Rock than that in site Qianlong Valley.However,the variation of productivity in site Xiantao Valley was lower than site Jiulong Lake peaks.All the sites in valleys had more species than those on the peaks.This result means a double-side amendment effect of sunlight factor,both on species richness and the stability of productivity.(5) The mechanism that biodiversity promote ecosystem function was also discussed,the data from Danxia communities of experimental area Taining and Wuyishan supported that the sampling effect of large fascicular graminoids would play a more important role in low-diversity ecosystems,while in high-diversity ecosystems,the complementary effect (represent as the pothic layers within plots) should be dominant.It seems that all these hypotheses should be considered as correct ones;however,each of them only fits ecosystems with some determinate conditions.Thus,there is no doubt that biodiversity does play an important role in ecosystem processes,as well as the abiotc factors, which take alterations to the biodiversity-ecosystem function relationship.