Soil Microbial Group And Its Seasonal Dynamics In Different Vegetation Restoration Areas In South Mountain Of Lanzhou City

In this study,15 years of planted forest and grassland wasteland restoration were selected as the research objects in the vegetation restoration areas of south mountain areas in Lanzhou.Through field sampling and laboratory experiments,the seasonal dynamics of the soil microbial groups(bacteria,fungi and actinomycetes)and soil physicochemical properties(soil water content?soil organic carbon?total nitrogen?total phosphorus?p H?soil temperature?unit weight?soil conductivity)were analyzed.The correlations between soil factors and soil microbial groups in different seasons were also analyzed.Aims to explore the relationship between environmental factors and soil microorganisms in semi-arid areas,and to evaluate the greening projects from the perspective of microbiology so as to improve the biological functions of forestlands,to guide future ecological restoration planning and environmental policies.At the same time,it provides a scientific theoretical basis for exploring the influence of environmental factors in different regions on the distribution of microbial flora.The main results of the study are as follows:(1)According to soil fertility index of artificial forestland in loess hilly region,the content of soil organic carbon in south mountain of Lanzhou was at a low level,ranging from 4.18 g·kg-1 to 41.50 g·kg-1.The contents of total nitrogen and total phosphorus were at intermediate level,ranging from 0.34 g·kg-1 to 2.14 g·kg-1,and from 0.28 g·kg-1to 0.53 g·kg-1.Soil nutrient content as a whole was higher in the planted forest than in the wasteland.With the change of seasons,the contents of soil organic carbon and total nitrogen in planted forest and wasteland all showed the highest in spring.The soil water content appeared the maximum value in summer.The soil water content of planted forest was slightly higher than that of wasteland.The soil of Lanzhou City was weakly alkaline.There was no significant difference in the p H value of the soil between different vegetation types with the seasons.The soil conductivity of planted forest and wasteland in the study area varied with the seasons.In the planted forest,soil conductivity was significantly higher in spring and summer than in autumn and winter,while in the wasteland,soil conductivity was significantly higher in summer than the other three seasons.The principal component analysis showed that the seasonal variation had a greater influence on soil environmental factors than the differences of vegetation on soil environmental factors.Soil organic carbon,total nitrogen and soil conductivity contributed significantly to the seasonal dynamics of soil microbial community in different vegetation types.(2)The three groups of soil microorganisms showed quite different changes with the seasons.Bacteria in the total number of microorganisms occupy an absolute advantage,accounting for more than 97%.The number of bacteria was significantly different in each season(P<0.05),showed summer> winter> autumn> spring.The number of fungi accounted for 0.04% ~ 0.63% of the total number of microorganisms,with the seasonal variation is small,the number of fungi appeared the lowest value in summer.The number of actinomycetes accounted for 0.03% ~ 2.28% of the total number of microorganisms,with the seasonal variation was significantly different(P<0.01),actinomycetes was significantly higher in spring and summer than in autumn and winter.In spring and summer,the total number of microbes in each sample area showed a markedly higher of wasteland than the planted forest(P<0.05).In autumn,there was no significant difference of soil microorganisms in planted forest and wasteland in sample area 1,and the total number of microorganisms in wasteland in sample area 2was significantly higher than that in planted forest.In winter,soil microorganisms of planted forest was significantly higher than that in wasteland in sample area 1,and the sample area 2 showed that the wasteland was significantly higher than that in planted forest.Multivariate analysis of variance showed that the change of vegetation and season had a significant effect on soil microorganisms,and the influence of seasonal change was greater than that of vegetation.The total number of microbes and bacteria caused by vegetation change and the estimated trend of marginal mean change of each group are roughly the same,showing that the wasteland is higher than the planted forest.Actinomycetes are less affected by forest stand.Seasonal changes in both vegetations cause significant changes in the estimated marginal mean of bacterial?fungi and microbial population,and in wasteland,the seasonal effect is greater than that in the planted forest.(3)The correlation between soil microbial groups and environmental factors varied greatly in different seasons.Redundancy analysis showed that there was a negative correlation between soil microorganisms groups and soil water content?soil organic carbon ? total nitrogen and soil conductivity in spring,but the correlation was not significant;The correlation between soil microbes and soil environmental factors in summer was roughly same with spring.The correlations between bacteria and fungi and soil water content ? soil organic carbon ? total nitrogen and unit weight were negative,and there was a significant negative correlation between bacteria and soil organic carbon and total nitrogen(P<0.05).There was a significant positive correlation between fungi and soil temperature(P<0.05).There was a significant positive correlation between the actinomycetes and soil temperature in autumn(P<0.05).There was no significant negative correlation between bacteria and fungi in winter and most soil factors,and there was a significant positive correlation between actinomycetes and unit weight(P<0.05).There was a significant positive correlation(P<0.05)between soil organic carbon and total nitrogen and soil water content in different seasons.And they were mainly distributed around plantation sample plots.There are significant differences in the correlation between soil environmental factors and species axis at different seasons.