Effect Of Clonal Integration On Nitrogen Turnover And Availability In The Rhizosphere Soil Of Rhizomatous Clonal Plant,Phyllostachys Bissetii,Subjected To Heterogeneous Light

Resources for plant growth,such as,light,water and nutrient,are heterogeneously distributed within various habitats.Clonal plant rapidly expands into open habitat by forming interconnected ramets(rhizome or stolon),thus placing ramets in contrasting environment.Resource heterogeneity raises the difficulty for plant in capturing essential nutrients.Carbohydrates,nutrients and water could be transported and shared among interconnected ramets of clonal plants,which was named as clonal integration.Clonal integration plays an important role for clonal plants in adapting to heterogeneous habitats,by enhancing survivorship of clonal fragment,improving growing performance,provisioning internal support to interconnected ramets.Rhizosphere is a zone of high microbial activity and turnover.Release of root exudates,such as sugar,organic acid,amino-acid,lipid and phenol,is primary source of labile carbon inputting to rhizosphere soil.As major sources of growth substrates and structural materials,the labile carbon was metabolized by root-associated microorganism.And the decomposition of recalcitrant soil organic matter provided essential nutrient for plant.An in-situ experiment was conducted by using clonal fragment of Phyllostachys bissetii with two successive ramets.Shading treatment(80%shading)was applied to offspring or mother ramets respectively,whereas counterparts were in full sun.Rhizome between two successive ramets was either severed or retained intact.We focused on following aspects:effect of clonal integration on nitrogen turnover and availability in the rhizosphere soil of rhizomatous clonal plant,Phyllostachys bissetii,subjected to heterogeneous light;effect of direction of assimilates transport on N turnover;microbial community composition in the rhizosphere soil of shaded,offspring or mother ramet;effect of clonal integration on nifH and amoA abundances in the rhizosphere.The key results of this research were exhibited as follow:(1)Effect of clonal integration on carbon availability was positive,while negative effect was observed on nitrogen availability.A higher DOC content was observed in the rhizosphere soil of shaded offspring,mother ramets.And MBC and MBN concentrations were significantly increased by rhizome connection.Positive effects of clonal integration were observed on extracellular enzyme activities.N turnover(Nmin or Nnitri)in the rhizosphere could be affected by direction of assimilates transport when clonal plant was suffering from heterogeneous habitat(2)A total of 556519 reads and 18898 OTUs were obtained from the twelve soil samples through Illumina Miseq sequencing.The bacterial OTUs were assigned into 13 different phyla and 415 genera.Nitrosomonadaceae(uncultured)?Nitrospira?Nitrospinaceae(uncultured)?Xanthobacteraceae(uncultured)?Bradyrhizobium were associated with soil N cycling,with low relative abundance.Principal component analysis(PCA)results revealed that microbial community compositions in the rhizosphere soil of shaded offspring,mother ramets were not influence by clonal integration,sharing similar micfrobial diversity at OTU level(3)Abundances of functional genes were significantly increased by clonal integration.Whether in acropetal treatment or basipetal treatment,functional gene abundances were negatively correlated with N availability in the rhizosphere soil.Corelation between abundance of functional gene and microbial processes(N turnover,extracellular enzyme activity)in acropetal treatment were different from that in basipetal treatment.In summary,C availability and soil mirobiomass were siginificantly increased by clonal integration in the rhizosphere soil of shaded offspring,mother ramets and further increase of microbial activity stimulated the turnover of soil organic matter in the rhizosphere.And direction of assimilates transport(acropetal,basipetal)exerted dfferent influence on N turnover and soil extracellular enzyme activities.We also tentatively concluded that changes in functional group abundances and its low proportion in whole soil microorganism may contribute to the fact that effect of clonal integration on rhizosphere microbial community composition was not significant.