| Minqin Oasis is located between Tengger Desert and Badain Jaran Desert,is the entrance of China for sandstorm in Northwest China,It blocked the merger of the two deserts,also blocked the sandstorm from the west,has a very important ecological strategic position.The establishment of sand-fixing forest can prevent wind erosion,promote the accumulation of soil organic matter and clay,and promote the formation of surface crust.It not only has a fixed effect on the sand dune,but also promotes aeolian sand soil forming process.In recent years,because of uncontrolled exploitation on groundwater resources,and natural causes,the sand-fixing forest in Minqin oasis was degraded in a large area,and the ecological problems are becoming more and more serious.Therefore there is important theory value and practical significance to do a systematic research on the degenerated sand-fixing forest.In this study,by the means of field investigation and laboratory analysis,the temporal and spatial dynamics of soil microbial biomass,soil enzyme activities and soil nutrientsthe of four different degree of degradation sand-fixing forest on the edge of Minqin oasis had been studied,and the correlation between them had been analyzed.The study aimed to explore the degradation mechanism of sand-fixing forest on the edge of Minqin oasis,and to provide reference for the restoration and reconstruction of vegetation.Main conclusions are as follows:1.There were obvious vertical distribution patterns of three kinds of microorganisms in soil: soil microbes were concentrated distributed in 0-10 cm soil layer and decreased with the increase of soil depth.In different seasons,there were significant differences in the number of three kinds of microorganisms in the soil.The seasonal dynamics were: low in spring,high in summer and low in autumn and winter.In all of the degenerated sand-fixing forest,bacteria occupied the dominant position,followed by actinomycetes and fungi is the least.The size relationship of the number of bacteria and the total microorganisms in different degree of degradation was: SLD>ND>MD>SD,and the The size relationship of the number of actinomycetes and fungi were: ND>SLD>MD>SD.2.The activity of urease,invertase and catalase in soil decreased with the increase of soil depth,soil enzyme activity was highest in the crust,and the vertical distribution of soil polyphenol oxidase activity was not obvious.0-10 cm soil urease,invertase,catalase and polyphenol oxidase activity of different degree of degradation sand-fixing forest showed a significant seasonal variation,the seasonal dynamic of soil urease,invertase and catalase activity were as follows: in the crust,high in spring,low in summer,autumn and winter,in 1-10 cm,high in summer,low in spring,autumn and winter.The seasonal dynamics of polyphenol oxidase activity in the soil was high in spring,low in summer,high in autumn and low in winter.With the increase of the degree of degradation,except for catalase,soil enzyme activity of 0-10 cm showed an increasing trend,and there was no significant difference between different degree of degradation in the levels of 10-40 cm.3.The vertical distribution of the content of soil organic matter,total N,available P and available K was obvious,highest in the crust,with the increase of soil depth,showed a decreasing trend.In different seasons,the contents of soil organic matter,total N and available P of 0-10 cm were different,the seasonal dynamics were as follows: high in summer,low in spring and autumn,the content of available K changed little,and the seasonal dynamics was not obvious.With the increase of the degree of degradation,the content of soil organic matter,total N,available P and available K in crust increased,and there was no significant difference between different degree of degradation in the levels of 1-40 cm.4.The correlation between the number of soil bacteria and the activity of soil urease,invertase and catalase,or the content of organic matter,total N,available P and K showed a significant positive correlation(p<0.01),the activity of urease,invertase and catalase were significantly positively correlated with the content of soil organic matter,total N,available P and available K(p<0.01).This showed that there is a close connection between the number of soil bacteria and the activity of soil urease,invertase and peroxidase or soil nutrient,moreover the soil enzyme is relatively stable,therefore,we can use the number of soil bacteria,and the activity of soil urease,invertase and peroxidase as indicators to evaluate the soil fertility of sand-fixing forest on the edge of Minqin Oasis. |
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