| As a special ecological transition zone in the northern inland sandy areas of our country,the MU US Sandy Land has remarkable eco-environmental sensitivity and vulnerability.Current studies have shown that the construction of soil microbial communities in desert ecosystems is closely related to plants,however the understanding and research on soil bacterial communities and their functional characteristics of different sand-fixing plants are not sufficient,the interaction mechanism between plant and bacterial communities is even less clear.Thus in this study,the soil bacteria of five typical sand-fixing plants in the southeastern margin of Mu Us were used as the research objects.Through field investigation and indoor analysis,the differences in their soil physicochemical properties and soil bacterial community structure were clarified,and the relationships among sand-fixing plants,soil physicochemical properties and bacterial communities were initially revealed.The response of soil physicochemical propertiesbacterial communities to groundwater depth was also investigated,using Artemisia desertorum Spreng(Ard)and Salix psammiphlia(Sap)as representatives.The main conclusions are as follows:(1)The soil physicochemical properties of five typical sand-fixing plants were analyzed by one-way ANOVA and multivariate statistics,etc.The results showed that total soil nitrogen,organic carbon and available phosphorus in soil of Caragana korshinskii(Cak)were significantly higher than those of other plants,more adaptable to sandy environments.Correlation analysis and redundancy analysis(RDA)revealed that changes in soil nutrients(TN,SOC and AP)had stronger effects on soil bacterial community composition than soil p H and soil moisture,with a highly significant positive correlation between soil total nitrogen and soil organic carbon,which could jointly promote changes in soil bacterial diversity.Partial least squares regression analysis(PLS)indicated that the effect of soil moisture on soil bacterial community was related to groundwater depth.(2)PCR and high-throughput sequencing techniques were used to analyze the structure and potential function of soil bacterial communities in different plants.The results showed that the structure and function of soil bacterial communities differed significantly among plants,but the network structure can be closely linked to maintain the stability of bacterial community.The dominant phyla of soil bacteria of five typical sand-fixing plants were Actinobacteria,Proteobacteria and Chloroflexi.The alpha diversity of soil bacteria was as follows: Caragana Korshinskii(Cak)>Hedysarum mongolicum Turez.(Hem)>Salix psammophila(Sap)>Artemisia desertorum Spreng(Ard)> Pinus sylvestnis var.mongolica Litv.(Piv),among which the soil bacterial diversity of Cak showed significant differences with the other four plants.The relative abundance of phototrophy functional flora in soil bacteria of Ard was significantly higher than that of other four plants,while nitrogen metabolism functional flora of Cak was significantly higher.The correlation network analysis showed that the collinear network of soil bacterial communities of the five plant species was mainly positive correlation.The network structure of Piv was relatively simple,while that of Cak was mainly formed by the cooperation of soil bacterial communities,co-occurrence networks are the most complex.(3)Structural equation modeling(SEM)was used to analyze the interaction between sandfixing plants,soil physicochemical properties and bacterial communities,the results showed that plant types directly regulate soil bacterial community through synergistic interactions between soil physicochemical properties,thus indirectly affecting community diversity and its potential functional flora.Soil physicochemical properties had significant positive effects on the relative abundance of potential functional microbial communities for hydrocarbon degradation,aromatic compound decomposition,nitrification and nitrogen respiration,which were beneficial to accelerating soil carbon and nitrogen cycling.The soil physicochemical properties mainly had direct regulation of soil alpha diversity mainly by negative effects,while soil beta diversity was only directly affected by significant positive effects of total nitrogen and available phosphorus.(4)The response relationship between soil physicochemical properties and bacterial community to groundwater depth was studied by multivariate statistical analysis and potential functional flora analysis,the response of soil physicochemical properties,bacterial functional flora and co-occurrence network complexity to groundwater depth is obvious.The results show that the optimum water and nutrient conditions for the growth of Artemisia desertorum Spreng(Ard)and Salix psammophila(Sap)are provided when the groundwater depth is between 4.7m and 5.2 m.The ASVs of Ard and Sap were significantly higher and the alpha diversity of bacteria was relatively higher at the groundwater depth less than 5 m.The soil bacteria of Ard were more stable and its functional flora was more favorable to carbon metabolism.The relative abundances of functional flora involved in nitrogen cycling and phototrophy in Sap soils bacteria were significantly higher when the groundwater depth was more than 5 m.This study confirmed that different plants have specific soil microbial community composition and functional characteristics.The Cak is more adaptable to the current growing environment of the study area,priority should be given to planting in the Mu Us Sandy Land“Prevention of secondary desertification” action.In the ecological construction of the restored sand area,suitable sand-fixing plants should be planted according to the burial depth of the groundwater level,which ranges from 4.7 to 5.2 m to provide the most suitable water and nutrient conditions for the growth of Ard and Sap.This study provides a new theoretical support for desertification control from the perspective of soil bacteria,and has some practical significance for vegetation restoration and management. |
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