Bacterial Diversity Of Biological Soil Crust And Related Ecological Function In Mu Us Sandy Land

Biological soil crust(BSC)is one of common ground cover in arid and semi-arid ecosystem.BSC could acclimatize itself to extreme conditions then survive,meanwhile could affect the surrounding microenvironment via its own activity and metabolism to.Soil bacteria is a biological component of the soil in arid and semi-arid ecosystem,and also play an important role in energy cycling and material transformation.Furthermore,soil bacteria could provide nutrients to sand and then change its physical and chemical properties.As a result,the colonization and growth of higher vascular plants are influenced by the BSC.The study took different types of biological soil crusts and soil underneath as research objects.The bacterail isolation & culture techniques were used to obtain culturable bacteria;at the same time,the C,N,P index of different types of biological soil crusts and soil underneath were detected,then the soil ecological stoichiometry characteristics were analyzed;The Biolog-ECO Micro-plates were applied to study microbial carbon source metabolism and community function in BSCs.The ecological functional characteristics of bacteria in biological crusts were analyzed and the main experimental results were as follows:(1)There were 65 strains,60 strains and 90 strains of culturable bacteria were isolated from the the biological crust,soil underneath and plant samples collected in sunmmer,respectively.104 strains of culturable bacteria were isolated from samples collected in winter.The biomass of culturable bacteria in samples collected in sunmmer was higher than that in winter.The bacterial biomass of algal crusts and moss crusts were significantly higher than that of physical crusts.In summer and winter,bacteria belong to Bacillaceae and Micrococcaceae were always in dominant positions.The diversity index and evenness index of culturable bacteria in summer were significantly higher than that in winter,the dominance index at summer was lower than that in winter.The bacterial biomass in the layer of BSCs were higher than soil underneath,but the diversity index and evenness index shown no significant variation between BSCs and soil.The bacteria genus and family distribution in BSCs related plants was deficient compared to BSCs.(2)Due to the existence and developmental succession of biological crusts,the content of organic carbon(C)and total nitrogen(N)were significantly higher than that of the subsoils(0-20 cm),and the difference values gradually increased with the developmental succession of BSCs.The vertical distribution of C and N in BSCs subsoils was similar to that of bare sand.But the distribution of total phosphorus(P)was different due to the succession of BSCs.The organic matter in biological crusts were degraded during the period of developmental succession.Biological crust in the middle and early stage of succession,the content of available phosphorus in BSCs was higher than in bare sand,this phenomenon was beneficial to the growth of moss and vascular plants.But during the middle and late stages of succession,the content of available phosphorus in BSCs was reduced,which indicated that BSCs might compete with vascular plants in the environment.In the Mu Us Sandland,with the succession of BSCs,phosphorus may be the limiting factor for the further development of BSCs.Biological crusts have limited impact on soil nutrient recovery and can only promote soil restoration within the depth of 10 cm.(3)With the development and succession of BSCs,the ability of bacteria utilize carbon sources in the bio-crust and subsoil was gradually increased;the ability of bacteria utilize carbon sources in the moss crust and the soil underneath was significantly higher than that of bare sand.The trend of the diversity of carbon sources utilization from flora in the biological crusts and soil underneath was consistent with the succession direction of BSCs,which was as the bio-crust progresses to a higher stage,the microbial community gradually increases in the diversity of carbon sources.The bacterial flora in bare sand mainly use three kinds of carbon sources: polymer,carbohydrate and carboxylic acid.But compared to bare sand,the bacterial flora in soil underneath had stronger ability to use phenolic acids.Physical crusts,algae crusts and the soil underneath were similar to bare sand in the structure of microbial carbon metabolism functional groups.Moss crust soil underneath and lichens crust were similar.Butane diamine and D-xylose can be used as indicators to distinguish between various types of crust and underlying soil in Mu Us Sandland.(4)Two new strains were isolated form the sandland environment,strain 1N-3 is a new species in Phyllobacterium.Polyphasic taxonomy shown that cells are aerobic and motile.Colonies on NA are pearl white,bright and convex.The temperature range for growth is 15–40°C(optimal growth occurs at 30°C).The p H range for growth is 5–10(optimal growth occurs at p H 8.0).Can grow with 0–4%(w/v)Na Cl.Gram-stain negative.Oxidase and catalase positive.The nitrate reduction test is positive,and ?-galactosidase hydrolysis and aesculin tests are negative.The major fatty acid present is summed feature 8.The DNA G+C content of the type strain is 60.1%.strain 1N-3 is a new species in Rhizobium.Polyphasic taxonomy shown that cells are aerobic and non-motile.Colonies on YMA are milky,bright and convex.The temperature range for growth is 15–37°C(optimal growth occurs at 30°C).The p H range for growth is 6–9(optimal growth occurs at p H 7.0).Can grow with 0–4%(w/v)Na Cl.Gram-stain negative.Oxidase and catalase positive.The nitrate reduction test is positive,and ?-galactosidase hydrolysis and aesculin tests are negative.The major fatty acid present is summed feature 8.The DNA G+C content of the type strain is 60.0%.