| Saibei desert grassland was a typical desertification region in northern China,where the ecological environment was fragile and the desertification was serious.Due to the dry and windy conditions,the unique plant diversity and vegetation zonality were formed in this region.The cloned plant Psammochloa villosa and Artemisia sphaerocephala,as pioneer plants in the desertification region,were the main vegetation types in the study area.They could resist sand burial and occupy new niches through their unique clonal integration characteristics,and provide a special living environment for the arbuscular mycorrhizal fungi at the same time.Slope position,as an important topographic factor,affected the soil microenvironment.The microbes could be affected directly by the climatic factors,vegetation types,and soil physical and chemical properties at different slope positions in the soil.In this study,the symbiotic relationship between clonal plants and arbuscular mycorrhizal fungi in Saibei desert was taken as the entry point,and the soils of rhizosphere and sand wormwood rhizosphere were taken as the research object,the arbuscular mycorrhizal colozation rate was measured by Pillips and Hayman staining method and spores of AM fungi were isolated and counted by wet-seiving method.Meanwhile,the morphological method was used to identification and classification of AM fungi spores.PLFA method was applied to determine the microbial community structure diversity,soil physical and chemical indicators were measured by conventional assay methods.The impact of slopes and seasons on AM fungi in the rhizosphere soil of P.villosa and A.sphaerocephala were investigated,and the correlation of AM fungi and soil factors were analyzed,respectively.The purpose of this study was to explore the effect of clonal plant growth on Soil Microenvironment on the slope scale.A theoretical basis for vegetation restoration in desert ecosystems was period by the study.The main experimental results are as follows:1.P.villosa and A.sphaerocephala could be infected by AM fungi,forming typical symbiotic structures,such as septate hyphae,microsclerotia,vesicle and so on in Saibei sandland.The average hyphal colonization rate and total colonization rate were 63.05% and 68.76% for P.villosa,and 63.07% and 67.95% for A.sphaerocephala.The hyphal colonization rate and total colonization rate of AM fungi at the bottom slope were significantly higher than those of middle slope and top slope,and the colonization rate decreased with the deepening of soil layer.In terms of temporal distribution,mycelial colonization and total colonization rates were significantly higher in June and October than in August when P.villosa and A.sphaerocephala were vigorously growing.The colonization rate of AM fungi was closely related to soil factors.2.The density of spores in the rhizosphere of P.villosa and A.sphaerocephala were about 143/100 g soil and 273/100 g soil.The density of spores in the bottom slope was significantly higher than that in the middle slope and the top slope.The spore density gradually decreased with the deepening of the soil layer.In temporal distribution,the density of spores reached the highest value in October.Correlation analysis showed that spore density of AM fungi was closely related to soil factors.3.The contents of total glomalin(TG)and easily-extracted glomalin(EEG)were 1.075 and 0.442 mg/g in the soil of P.villosa rhizosphere and 1.082 and 0.520 mg/g in the soil of A.sphaerocephala rhizosphere,respectively.The content of glomalin gradually decreased with the deepening of the soil layer,and it was significantly higher in August than that in June and October.The ratio of TG and organic carbon(SOC)in the soils of P.villosa and A.sphaerocephala were about 16.65% and 16.20%.4.The soil physical and chemical factors of P.villosa and A.sphaerocephala have obvious spatial and temporal heterogeneity.The average soil organic carbon of P.villosa and A.sphaerocephala in the study area was 6.523 and 6.662 mg/g,and the available nitrogen was 17.449 and 16.540 ?g/g,and the available phosphorus was 4.527 and 2.011 ?g/g.Soil organic carbon,available phosphorus and available nitrogen was significantly higher at the bottom slope than that at the middle slope and top slope.The soil acid phosphatase and alkaline phosphatase also showed the same trend.With the soil layer deepened,the soil factor content gradually decreased.In terms of temporal distribution,organic carbon,available phosphorus and phosphatase reached the highest level in August,while available nitrogen was lower in October than in June and August.The principal component analysis showed that phosphatase,organic carbon and alkali-hydrolyzed nitrogen were the main factors.5.In Saibei sandland,27 AM fungal species belonging to four genera were identified in thesoil of the P.villosa and A.sphaerocephala.16 species belonged to Glomus,2 species belonged to Funinciliformis,6 species belonged to Acaulospora,and 3 species belonged to Scutellospora.6.The spatial and temporal distribution of soil microbial community structure in the roots of P.villosa had heterogeneity.The average content of gram-negative bacteria(G-),gram-positive bacteria(G+),fungi,arbuscular mycorrhizal fungi,and actinomycetes in the soil in the study area were 7.908,9.046,0.719,0.370,and 4.238 nmol/g,respectively.G-,G+,fungi,and AM fungi at the bottom slope were significantly higher than in the middle slope and top slope.G-,G+,and actinomycetes were higher in June than in August and October,but there was no significant difference between months for the content of fungi and AM fungi.7.With the extension of sampling time,the count of P.villosa invaded the vacant patches was gradually increased.By September 2015,the average number of sand ramets was 8.5,10.3 and 23.0 in the bottom,middle and top slope,respectively.In addition,the colonization rate of AM fungi,spore density,species diversity,soil organic carbon,alkalinity N,and effective P content were all increased after invasion,and they were all higher than those of the control group. |
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