| In this paper,the method of field investigation and indoor experiment is used to analyze the typical karst area of Guizhou-Maolan Nature Reserve as the main research object,to staton the soil microbial diversity,the effects of soil nutrient,agglomerate total carbon,total nitrogen and total phosphorus,agglomerate activity,soil microbial biomass carbon,microbial biomass nitrogen,soil microbial population and microbial diversity were studied systematically under different land use patterns in Maolan Nature reserve.The relationship between soil nutrient and soil enzyme activity,the distribution of soil aggregates,the correlation between soil microbial biomass carbon,microbial biomass nitrogen and microbial diversity were studied,at the same time,comparison of Huajiang Canyon demonstration area,provide scientific basis for the protection of soil microbes and the rational use of soil resources in karst mountainous areas.The main conclusions are as follows:?1?The effects of four main communities,such as arbor forest,Frozen forest,shrub forest and returning farmland,on the litter and soil physical and chemical properties were studied in the typical karst of Maolan in Guizhou.The results show that the karst area under different disturbance degree of soil nutrient and enzyme activity levels decrease with the increase of soil depth,and the interference degree different degree of its reduction.Litter factor and the correlation between soil nutrient showed that litter factor and the close relation between soil nutrient.Litter total nitrogen content and soil total nitrogen content was significantly positively related,litter total phosphoruswith soil organic carbon,total nitrogen,total potassium,calcium,magnesium,and water content was significantly correlated;urease activity,sucrase activity and soil organic carbon,total nitrogen,total potassium,calcium,magnesium,and water content significantly related.Size analysis results show that the direct effect of soil nutrients of urease activity in order for the calcium<carbon /nitrogen < total potassium < total nitrogen < total phosphorus < soil organic carbon<magnesium<water content,total potassium have direct influence on sucrase,total nitrogen,water content,magnesium is the main factor affecting the catalase,soil and soil urease and sucrase,catalase activity has good correlation between.To sum up,the degree of interference in karst areas of vegetation and soil has obvious effect,reflect the niche characteristics of the karst area.?2?Taking the cultivated land,returning farmland to grassland returning farmland to forest land,shrub and primary forest in Maolan Karst Nature Reserve of Guizhou as the research object,the distribution of soil organic carbon,total nitrogen and total phosphorus in layer of 0 20 cm soil layer and the ecological and economical characteristics of soil were analyzed.The results show: compared with the original forest,the cultivated land,returning farmland to grassland,returning farmland to forest land and shrub significantly reduced the content of soil organic carbon and total nitrogen in the original soil and aggregates,and increased the total phosphorus content.With the gradual reduction of particle size,and in 0.50.25 mm size agglomerates organic carbon and total nitrogen content of the highest.The contribution rate of aggregate to organic carbon,total nitrogen and total phosphorus was> 5 mm,and the contribution rate of <0.25 mm grain size to aggregate soil organic carbon,total nitrogen and total phosphorus was the smallest.The correlation analysis shows that soil aggregates soil organic carbon,total nitrogen and aggregate content of each grade were positively correlated or extremely significant,while the total phosphorus was opposite.The variability of carbon /nitrogen ratio was 14.32%,soil carbon/phosphorus ratio and nitrogen/ phosphorus ratio were the highest in small particle size,and the soil carbon/nitrogen ratio,carbon/phosphorus ratio and nitrogen/phosphorus ratio can be used as a sensitive index to measure the dynamics of soil organic carbon in the subtropical karst area ofChina.?3?In order to study the distribution characteristics of soil nutrients and enzyme activities under different land use patterns in karst flower and dry valley,the relationship between soil enzyme activity and soil nutrient was studied.The results show: there were significant differences in soil nutrient content and soil enzyme activity between land use types,the changes of soil microbial biomasscarbon,microbial biomass nitrogen,urease and invertase were shrubs>Zanthoxylum bungeanum Maxim>Pennisetum sinese Roxb>Pennisetum alopecuroides?L.?Spreng>grassland,compared with the grassland,the soil microbial biomass carbon and microbial biomassnitrogen contents of shrubs,Zanthoxylum bungeanum Maxim,Pennisetum alopecuroides?L.?Spreng,and Pennisetum sinese Roxb were 2.57 times,2.01 times,1.15 times,1.21 times and 1.86 times,1.44 times,1.20 times,1.26 times;soil urease activity shrubs were up to 247.13 ug·g-1 Zanthoxylum bungeanum Maxim,Pennisetum sinese Roxb,Pennisetum alopecuroides?L.?Spreng and grassland were 62.01%,75.77%,87.95% and 46.50%;the content of soil sucrase was 37.31%,80.42%,70.12% and 48.09,respectively,in the shrub land of 121.37 ug·g-1·h-1,which was higher than that of the Zanthoxylum bungeanum Maxim,Pennisetum sinese Roxb,Pennisetum alopecuroides?L.?Spreng and the grassland;the changes of soil phosphatase and urease and sucrase were basically inconsistent,there was no significant difference in soil phosphatase activity between Pennisetum alopecuroides?L.?Spreng and Pennisetum sinese Roxb,respectively 0.5111 ug·g-1·h-1,0.5471 ug·g-1·h-1,and the grassland and the Zanthoxylum bungeanum Maxim were 41.71% and 72.24% of the shrub respectively.Relevance analysis: urease and sucrase were significantly correlated with soil organic carbon,total nitrogen and total potassium;there was a significant positive correlation between enzyme activity and microbial biomass carbon and microbial biomass nitrogen.?4?The soil particle size,agglomerate nutrient content and soil enzyme activity distribution were studied under different land use patterns in Maolan Karst Nature Reserve,which provided scientific basis for maintaining and improving soil fertility.The results show: the regularity of the agglomerates after the dry sieves is:?>5 mm?>52 mm>10.5 mm>21 mm>0.50.25 mm>?<0.25 mm?;soil urease,sucrase and phosphatase activity were basically the same,the soil enzyme activity was the lowest,the highest was the primary forest;the variation of enzyme activity in different land use patterns was basically inconsistent,but the soil enzyme activity was the highest in agglomerate <0.25 mm.From the different size of agglomerates can be seen,urease,phosphatase activity rate of change in the size of the same law,are both:?<0.25 mm?<10.5 mm<21 mm<0.50.25 mm<52 mm<?>5 mm?;the variation of sucrosease activity was?< 0.25 mm?<21 mm< 10.5 mm<0.50.25 mm<52 mm<?>5 mm?,the activity of soil enzymes in the agglomerates showed a significant positive correlation between the three enzyme activities.The soil enzyme activity of agglomerates under different land use patterns is a good basis for improving soil aggregate structure,improving soil enzyme activity and rapid vegetation restoration.?5?The relationship between soil microbial species distribution and soil nutrient ecosystem under different land use patterns in Maolan Nature Reserve was discussed.The results show: the number of soil microbial carbon and nitrogen and microbes increased with the increase of age,the soil microbial biomass was the highest in winter and summer,followed by primary forest>cultivated land>cropland to grassland>shrub> returning farmland to forest land,the variation of carbon content in winter was between 21.26662.73 mg·kg-1,and the variation of summer was between 7.27267.22 mg·kg-1;The content of nitrogen in microbial biomass was mainly distributed among 89.38-312.99 mg·kg-1 in summer and 76.00267.32 mg·kg-1 in summer.The number of soil microbes was related to the distribution of soil and the ecological environment,and the difference of soil microbes was significant under different land use patterns.The number of microbes in winter was between 2.54118.19 nmol·g-1,and the number of microbes in summer was between 1.64106.27 nmol·g-1;Relevance analysis: There was a significant positive correlation between soil microbial biomass and microbial biomass carbon and nitrogen.The amount of microbial biomass carbon and nitrogen and microbes can be used as a reference index for evaluating soil fertility. |
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