Characteristics Of Soil Microbial Community Along Altitudinal Gradient In Karst Graben Basin,A Case Study In Yunnan Province

Distribution pattern and maintenance mechanism of biological communities along the altitudinal gradient are hot topics targeting ecosystem function.Compared with the altitudinal distribution pattern of animal and plant communities,the study on the altitudinal distribution pattern of soil microbial communities is still in the initial stage.Although there were studies on mountain system in non-karst areas,there are few studies on the karst graben basin with large altitude span and high habitat heterogeneity.So,we measured soil organic carbon,total nitrogen,total phosphorus,available potassium,soil moisture,soil temperature and electrical conductivity and studied the structure and diversity of microbial communities by using 16S rRNA and 18S rRNA high-throughput sequencing techniques along altitudinal gradient in Yunnan karst graben basin.The main findings are:(1)The content of soil organic carbon,total nitrogen and available potassium in 0?10 cm was abundant,total phosphorus was intermediate or above.Nutrient deficiency was observed in 10?20 cm samples.The nutrients of 10?20 cm was from the downward migration of 0?10 cm soil layer,therefore,the distribution trend of soil nutrients along altitude gradient in 10?20 cm was similar to that in 0?10 cm.In addition,the soil organic carbon and total nitrogen at high altitude were high under the influence of temperature,while soil erosion driven by altitude resulted in accumulation of available potassium at low altitude.(2)The results of high throughput sequencing analysis showed that Proteobacteria was the most abundant phylum in high altitude and Acidobacteria was the most abundant phylum in low altitude.The relative abundance of Proteobacteria had the greatest correlation with altitude in 0?10 cm,and had the greatest correlation with soil temperature in 10?20 cm.The relative abundance of Acidobacteria and Actinobacteria was positively correlating with soil temperature.The dominant fungal group was Agaricomycotina.In addition,the same microbial group had different trends with altitude.Differences in environmental factors led to different relationships between microorganisms and environmental factors in the same group.(3)The distribution pattern of a diversity showed no trend along altitudinal gradient.The results of ?diversity showed that the ? diversity of prokaryotes moves strongly in different directions at large altitudes span.Relative frequency heat maps of dominant OTUs showed that the microbial community structure was different in the two transects.(4)Soil moisture was highly correlated with a diversity of prokaryotes and eukaryotic microorganisms in environmental factors.The most significant correlations with prokaryotic dominance OTUs were altitude,soil moisture,soil temperature and conductivity.The most significant correlation with the dominant OTUs of eukaryotic microorganisms was altitude and soil temperature,but the correlation was weaker than that of prokaryotes.To some extent,prokaryotes are more sensitive to environmental factors than eukaryotic microorganisms,and the influence of each factor on microorganisms was weaker in 10?20 cm than in 0?10 cm.(5)The partial least squares path model(PLS-PM)showed that altitude exerted the greatest direct impact on the community structure of prokaryotes and eukaryotic microorganisms in 0?10 cm layer,and soil physical properties exerted the greatest impact on a diversity.The results showed that the community structure of prokaryotes and eukaryotic microorganisms was directly affected by temperature and the diversity of microorganisms was indirectly affected by altitude through affecting soil physical properties(soil moisture).In 10?20 cm,the most significant impact on the community structure of prokaryotes and eukaryotic microorganisms also was altitude,but the direct effect of altitude was reduced.Soil physical properties(soil moisture)also exerted the greatest impact on prokaryotic a diversity.Altitude indirectly affects a diversity of prokaryotes by affecting soil physical properties(soil moisture).The results showed that soil moisture was the main factor affecting the non-trend change of a diversity along altitudinal gradient.The response of different microorganisms to altitude gradient depends on their sensitivity to different environmental factors and the limitation of specific environmental factors.In addition,altitude exerted direct or indirect effects on the structure and diversity of prokaryotic and eukaryotic microbial communities.