Researches On Influence Of Planting Pepino On Soil Ecological Stoichiometry And Microbial Community In Shilin Karst Area

In the adverse effects of natural conditions and human activities,land original balance was broken,besides,the utilization efficiency of land and available agricultural field also were both reduced.Karst rocky desertification was one of the major degraded land types in China,which was very meaningful to study the characteristic of ecological stoichiometry and microbial community for the utilization of degraded land and improvement of agricultural field.In this study,the key limiting factors of soil nutrient and soil rhizosphere and non-rhizosphere microbial community were preliminarily explored in Shilin Country,Yunnan province,to illustrate the main limiting factors of soil and the superiority bacteria,and provide certain theory basis for the environment restoration.In this study,the advantaged crop(Solarium muricatum,pepino)of Shilin was selected as test material to reveal the main limiting nutrient by studying the nutrient element stoichiometry in soil and plant.By the second generation sequencing technology,the rhizosphere and non-rhizosphere soil microbial community,the correlations between soil physicochemical properties and bacteria were revealed.Besides,the effects of pepino on soil enzyme activity,physicochemical properties and mineral composition were also studied.The main results were listed below:(1)The soil nutrient content in karst rocky desertification was very low.The mean content of organic carbon was 4.5 g·kg-1.The total nitrogen content was 0.9 g·kg-1.The total phosphorus content was 0.5 g·kg-1.The average N:P ratio of pepino leaf was 7.64 in karst rocky desertification area,and was significant lower than 14(N limit boundary values),which revealed that the main soil limiting factor was nitrogen.Plant root K:Ca ratio had significant positive correlation with soil K content,and significant negative correlation with soil Ca content.It also had significant negative correlation with foliar Ca content,and significant positive correlation with foliar K:Ca ratio.(2)In karst rocky desertification soil,the mean content of urease activity was 0.03 mg·g-1·day-1,catalase activity was 15.3 mL g-1·-30 min-1,and invertase activity was 12.5 mg·g-1·day-1.The growth of pepino significantly improved the urease activity in rocky desertification soil(0.09 mg·g-1·day-1);and significantly decreased catalase activity(4.04 mL·g-1·30 min-1).But there was no significant change with invertase.The growth of pepino significantly improved the soil microbial community Shannon and Chao 1 index,and significantly increased the diversity.The rhizosphere soil microbial diversity was higher than normal planting environment.(3)The composition of soil bacteria was similar,but the proportion of each phylum was certain different.The soil superiority phyla were Proteobacteria,Acidobacteria,Actinobacteria and Bacteroidetes,accounting for more than 80%.The growth of Pepino could increase the proportion of Proteobacteria significantly,and decrease Acidobacteria,Actinobacteria,Gemmatimonadetes,Chloroflexi and Firmicutes significantly.Total 625 different genera were found,and 63 genera showed significant differences.The growth of Pepino could significantly increase the proportion of 22 genera in soil,and significantly decrease the proportion of 18 genera.(4)The soil bulk density in 10-20cm layer was greater than 0-10cm layer in karst rocky desertification,and soil porosity showed the opposite trend.The sand proportion in rocky desertification soil was more than 70%,and clay proportion was lower than 15%,which presented an unreasonable structure of soil particles.The growth of pepino could decrease sand and increase clay proportions.The main minerals of rocky desertification soil in shilin were quartz,calcite and muscovite.Quartz had significantly positive correlation with calcite(r=0.97),and had significantly negative correlation with muscovite(r=0.98),calcite had significantly negative correlation with muscovite(r=0.99).The above results showed that the main limitation was soil nitrogen.The growth of pepino significantly benefited the soil microbial community diversity.Proteobacteria,Acidobacteria,Actinobacteria and Bacteroidetes were superiority phyla in the soil,accounting for more than 80%.The main minerals in rocky desertification soil were quartz,calcite and muscovite.