The Composition And Dynamic Change Of Microbiotic Crust In Shapotou Vegetation Sand Fixation Area In Ningxia

The microbiotic crust is an microecological soil layer composed of mosses,lichens,algae,microfungi and cyanobacteria with the underlying meadows and sand grains,which is helpful to promote for wind prevention and sand fixation,species succession and ecology recovery.According to different dominant species,the microbiotic crust can be divided into algae crust,lichen crust and moss crust,among which lichen crust is most compact,fixing and intertwining sand particles with lobes or rhizines,and morover,lichen crust has stronger carbon-fixation and nitrogen-fixation ability.As part of the preliminary work of the 'biocarpet engineering' project,this study mainly focused on the dynamic change of lichen community and species composition,and correlation analysis based on both biotic(plant and soil microbiology in artificial vegetation region)and abiotic factors(rainfall and soil physiochemical properties in artificial vegetation region).The main results and conclusion obtained are as follows:1.There was significant correlation between lichen species composition and developing time of crusts,and as the establishment time of artificial vegetation regions went by,lichen coverage increased,which was 1.41%,5.73%,5.99%,4.27%and 6.43%(2015-1956),respectively.There include the main lichen species such as Collema coccophorum,C.tenax,Endocarpon adsurgens,E.crystallinum,E.pusillum,E.shapotouenis,E.simplicatum,Fulgensia fulgens,Heppia sp.1,H.sp.2,Placidium lacinulatum,P.sp.1,P.sp.2 and other unknown species,among which the dominant taxa were Collema and Endocarpon,and Collema was a little more predominant.2.There existed positive correlation between lichen coverage and plant coverage.The plant species in artificial vegetation regions included Hedysarum scoparium,Ceratoides arborescens,Artemisia ordosica,moss and short-lived plants.Similar to the development of lichen coverage,the total plant coverage,including vascular plants and moss,varied as 2.56%,42.45%,51.50%,55.35% and 55.05%,respectively.The temporal patterns of the three major biological components of lichens,mosses and typical vascular plants in the artificial vegetation fixation area were basically consistent.However,the variation of the coverage of different vascular plants was similar to that of lichen,and the coverage of Artemisia ordosica and short-lived plants was positively correlated with lichen,and Ceratoides arborescens were generally negatively correlated with lichen,while Hedysarum scoparium cover was not significantly related to lichen relationship.3.It showed the positive correlation between lichen coverage and soil micribiology species compostion and number,which was indirectly proved via the developing time of crust soil.That is,the longer of developing time of crust soil,the lichen coverage would be larger,and correspondingly soil microbiology species would be more.Using the Illumina Miseq high-throughput sequencing platform,the soil fungi and bacteria were sequenced on nrDNA ITS and 16 s rDNA,respectively.999 fungal and 1226 bacterial OTU were identified under 97% sequence similarity,including fungal 7 phyla,20 classes,57 orders,111 families and 166 genera,and bacterial 19 phyla,59 classes,76 orders,85 families and 109 genera,among which involved 4 genera of lichenized fungi,i.e.Catapyrenium,Endocarpon,Glypholecia and Placidium,accounting for 2.2% of all the fungal genera.The species composition and quantity composition of microbial community were positively correlated with time on the time scale of soil development,and the interaction between microbial community composition and soil nutrient factor was different in different developmental extent.Among them,the dynamic changes of bacterial community and soil microbial community development trend is closer.4.There is relationship between lichen distribution and coverage and local rainfall,and positive correlation to soil nutrient content.The effects of lichen and plant cover on precipitation and soil nutrient,annual rainfall,crustal soil thickness(TC),hydrolyzable nitrogen(HN),total nitrogen(N),total carbon(C),organic carbon(OC),phosphorus(P),available phosphorus(AP)and Potassium(K)and other ecological factors to detect and statistical analysis we can see: Shapotou area of water is the main source of natural precipitation,and from 1955 to 2014,the annual rainfall fluctuations,may directly lead to the existence of licorice and other biological components and development The At the same time,with the continuous succession of desert ecosystems,the soil thickness and soil nutrient of microbial crusts increased significantly,and there was no significant correlation between HN,AP,P,OC,N and C were positively correlated with crustal soil development and significantly affected the presence and distribution of lichens,plants and microorganisms.Lichen as an ecological successor of the "pioneer",has an irreplaceable role in the restoration of desert ecosystem.In this study,we focused on the lichen crusts with different development time,and studied lichen community compostion of the microbiotic crust,coverage change and correlation to biotic and abiotic factors based on time scale.This study can help us to find out how to develop and play the ecological function for the lichen community under the effect of two kinds ofecological factors,furthermore,it could provide the necessary theoretical basis and data support for carrying out 'biocarpet engineering' project.