The Effect Of Bacteria And Algae On The Cultivation Of Brachythecium Plumosum(Hedw.) B.S.G. And Its Intergenerational Change

As a result of production and construction projects such as highway and railway construction and mineral resources development,a large number of exposed rock slopes have been formed in Qinling area,and its water-holding capacity is poor,so it is difficult to achieve long-term and stable protective effect only by single measures.Moss crusts can grow on the rock surface,absorb nutrients and water from the atmosphere,and promote mineral differentiation and vegetation succession.It is a potential ideal material for bare rock slope restoration.There is a very broad market prospect for the ecological repair of rock engineering wounds by using artificially cultivated moss crusts,and it has become the primary task to explore efficient moss crusts cultivation techniques for the dominant species in specific areas.In summary,Brachythecium plumosum（Hedw.）B.S.G.,the lithophytic creeping moss species with growth-well and high biomass in the northern of Qinling Mountains,was as the moss inoculum material,exogenous addition of Rhodopseudomonas palustris and Chlorella vulgaris to carry out indoor moss crusts primary and subculture cultivation experiment.By measuring the growth indexes,eco-stoichiometric characteristics,nutrient indexes and microbial composition of matrix,the effect and mechanism of bacteria and algae and their adding time on the growth of moss crusts were explored,and the intergenerational differences of moss crusts treated by bacteria and algae were analyzed.The main conclusions are（For the convenience of expression,the following moss crusts all refers to Brachythecium plumosum（Hedw.）B.S.G.,bacteria all refers to Rhodopseudomonas palustris,algae all refers to Chlorella vulgaris）:（1）Bacteria can significantly promote the cultivation of moss crusts.The addition of bacteria during moss inoculum or the addition of algae 7 days in advance could promote the germination of moss crusts.The former is also beneficial to the growth of newly sprouted stem length.The addition of bacteria 7 days in advance was not conducive to the stable formation of moss crusts.The optimal treatment for the first cultivation of moss crusts is:adding low concentration(OD₆₀₀=3.231,12 ml·L^-1)of bacteria during moss inoculum.Under the condition of 32 days artificial climate incubator（temperature at 20℃,air humidity at 80%,light at 1500-2000 lx,photoperiod at 16 h:8 h）,compared to CK,the optimal treatment can increase the coverage of moss crusts by 14.3%,the number of new sprouts by 61.2%,and the length of newly germinated stems by 34%.（2）Bacteria and algae can affect the growth of moss crusts by affecting the utilization rate of nitrogen and available phosphorus by moss crusts,and the effect varies with the concentration ratio of bacteria and algae and the adding time.The addition of bacteria decreased the relative abundance of Actinobacteria and Tubulinea in the matrix by 22.5%and59.5%,respectively.Bacteria promote the growth of moss crusts by weakening the adverse effects of these microbial communities on moss crusts growth.（3）There were significant differences between primary and subculture moss crusts in response to the same treatment.The optimal treatment of subculture moss crusts cultivation experiment is:adding high concentration of bacteria(OD₆₀₀=3.231,24 ml·L^-1)during moss inoculum,which was higher concentration of bacteria than the first generation.Under the condition of 32 days artificial climate incubator（same as primary experiment）,compared to CK,the optimal treatment can increase the coverage of moss crusts by 16.6%,the number of new sprouts by 38.3%,and the length of newly germinated stems by 43.7%.Compared with the same treatment condition of first generation:the degradation of subculture moss crusts coverage did not show obvious regularity,but the overall coverage of the treatment with bacteria or algae was still higher than that of the control treatment;the number of new sprouting of subculture moss crusts obviously increased and the stem length decreased obviously;and the total C,N and P contents tended to increase,which was closer to the total C,N and P content of field moss crusts;the stoichiometric ratio of moss crusts of the treatment that adding bacteria and algae 7 days in advance are decreased;the phosphorus utilization efficiency of moss crusts with subculture optimal treatment was significantly improved,and the growth was faster.The recommended cultivation scheme is:adding low concentration(OD₆₀₀=3.231,12ml·L^-1)of bacteria during moss inoculum and subculture regularly,which can comprehensively improve the cultivation efficiency and achieve the full coverage of moss crusts more quickly,but the optimal subculture cycle and the suitable concentration of bacteria need further exploring.Subculture cultivation of moss crusts can also replace collecting moss crusts from field,which has important practical guidance value for realizing the sustainable circular development of ecological industrial production and engineering restoration of moss crusts.