Effects Of Exogenous Additives On Provenance Propagation And Field Recovery Of Moss Biocrusts In Sandyland

Artificial moss biocrusts(moss-dominating biological soil crusts)have attracted attention as a new type of windproof and sand fixation method in recent years,but the lack of provenance is still one of the bottleneck problems in the restoration of moss biocrusts engineering under natural conditions,and the propagation efficiency of moss biocrusts need improve.For further optimization of existing moss biocrusts provenance propagation techniques,and reveal the mechanism of different exogenous additives on the cultivation and restoration of moss biocrusts,this study adopts 4 factors 2 levels orthogonal experiment design,deeply discusses the effects of microorganism(actinomycetes,Bacillus megaterium),algae(Chlorella,Microcolus vaginatus),artemisinin gum(yes,no)and substrate type(sand substrate,formula substrate)on the provenance propagation and field restoration of moss biocrusts.The main results are as follows:(1)Several exogenous additives can promote the growth and propagation of moss biocrusts.Among the 4 factors,only the substrate type significantly affected the coverage and plant density of moss biocrusts.The average coverage and plant density of moss biocrusts treated with sand substrate were 61.0%and 17.5 strains/cm~2higher than those treated with formula substrate.The optimal propagation combination of moss biocrusts was"sand substrate+actinomycetes(1 g/kg substrate)+chlorella(2 g/m~2)".Within the 30days,based on the combination above under the incubator condition(set illumination,photoperiod,temperature,air humidity as 6000 lx,12 h/d,20?,75%),the moss biocrusts provenance of 1 m~2coverage of 92.0%can cultivated to be 4 m~2moss biocrusts coverage of 97.1%,which has realized 4 times multiplication.(2)Under the conditions of incubator,the growth treatment of"sand substrate+actinomycetes+chlorella"gradually exceeded that of other treatments after 15 days of cultivation,and the propagation effect reached the best after 30 days of cultivation.The combination of actinomycetes and chlorella add had the most obvious effect on the community structure of microorganisms when moss biocrusts was cultivated for 15?30days,With the addition of actinomycetes,the relative abundance of Actinobacteria,which is absolutely dominant in bacteria,increased when cultivate from 15 days to 30 days.With the addition of chlorella,the relative abundance of Chlorophyta,eukaryote richness and diversity increased at first(15 d)and then decreased(30 d).At the same time,the contents of soil organic matter and total nitrogen increased gradually after 15 days of cultivation,increased the activity of peroxidase(POD)and the content of soluble protein,decreased the content of malondialdehyde(MDA)and delayed the senescence rate of moss biocrusts.(3)In the field natural environment,the two treatments of"sand substrate+Atmisia gum+Bacillus megaterium+chlorella"and"sand substrate+actinomycetes+chlorella"developed rapidly and recovered to form a stable moss biocrusts at the stage of 70 to 105days,which was better than other treatments,but the recovery decreased after 140 days of cultivation.The addition of chlorella had the most obvious effect on the community structure of microorganisms during the period of 70?140 days of cultivation,the relative abundance of Chlorophyta and eukaryote diversity increased at first(70 d)and then decreased(140 d),and the eukaryote richness increased significantly.However,the relative abundance of bacteria did not change significantly during the whole cultivation period with the addition of Bacillus megaterium,actinomycetes and Microcolus vaginatus.At the same time,the addition of chlorella also increased the content of soil organic matter and total nitrogen at first(70 d)and then decreased(140 d),increased the peroxidase(POD)activity and soluble protein content of moss biocrusts cultivated from 70 days to 140 days,decreased the content of MDA,and made moss biocrusts have good stress resistance.(4)The main difference between indoor propagation and field restoration is that there is no significant difference in the promoting effect of different microorganism in field restoration,while the addition of chlorella plays a key role.Its effect is mainly shown in the two treatments of"sandy substrate+Atmisia gum+Bacillus megaterium+chlorella"and"sandy substrate+actinomycetes+chlorella"under field conditions,the recovery effect of moss biocrusts at the end of cultivation is better than other treatments.