喀斯特山地草地土壤酶活性及土壤微生物碳代谢活性研究

Soil Enzyme Activity and Microbial Carbon Metabolism Along an Altitudinal Gradient in Grasslands of Karst Mountain

为了明确喀斯特山地草地土壤微生物碳代谢功能,研究采用经典统计分析与排序分析,连续3年研究了桂西北喀斯特山地草地不同海拔土壤酶活性和土壤微生物碳代谢活性,并探讨了二者的相关关系。结果表明:(1)不同海拔喀斯特山地草地土壤养分含量(全氮、全碳、全钾、速效磷、碱解氮)呈一致的变化趋势,表现为中海拔>高海拔>低海拔,并且在不同海拔差异均显著(p<0.05);而土壤pH值表现为中海拔<高海拔<低海拔。(2)不同海拔喀斯特山地草地土壤微生物碳源利用差异较大,其中羧酸类和碳水化合物是主要的碳源类物质,其次为氨基酸类、酚酸类和聚合物类,胺类碳源的利用率最小。(3)不同海拔喀斯特山地草地土壤微生物群落多样性指数随年份的增加而增加(2015-2017年),平均碳源利用丰富度指数(S)、均匀度指数(E)和物种丰富度指数(H)均表现为低海拔>中海拔>高海拔。(4)不同海拔喀斯特山地草地土壤酶活性(几丁质酶、糖苷酶、碱性磷酸酶、亮氨酸氨基肽酶、过氧化物酶δ和酚氧化酶δ)随年份的增加而增加,平均酶活性均表现为低海拔>中海拔>高海拔。(5)土壤微生物量碳、微生物呼吸和土壤微生物代谢熵从2015-2017年均呈增加趋势,3年内土壤微生物呼吸平均值基本表现为中海拔>高海拔>低海拔。(6)RDA排序分析表明:土壤微生物群落多样性与土壤酶活性呈显著或极显著的相关关系,其中土壤微生物代谢熵和微生物呼吸是土壤微生物多样性分布的主要影响因子,而土壤全碳和全氮与土壤微生物群落功能多样性呈显著的正相关,由此表明土壤全碳和全氮是造成不同海拔喀斯特山地草地土壤微生物群落多样性差异的重要原因。

In order to clarify soil microbial carbon metabolism and enzyme activity along an altitudinal gradient in grasslands of karst mountain, we used classical statistical analysis and sequencing analysis to study soil microbial carbon metabolism and enzyme activity in the karst mountains for three consecutive years(from 2015 to 2017), and discussed the relationship between microbial community diversity and soil nutrient. The results are as follows.(1) The contents of total carbon, total nitrogen, total potassium, alkali-hydrolyzed nitrogen and available phosphorus in the soils of grasslands at different elevations decrease in the order: medium elevation>low elevation>high elevation, and the contents of total carbon, total nitrogen, total potassium, alkali-hydrolyzed nitrogen and available phosphorus in the soils at different elevations are significantly different(p<0.05). The pH values of soils show an opposite trend, while the difference of total phosphorus in soils is not significant at different elevations(p>0.05).(2) There are significant differences in functional diversity of microbial communities along the altitudinal gradient. The carbon sources mostly used by soil microbes are carbohydrates and carboxylic acids, followed by amino acids, phenolic acids and polymers, the lowest is amines.(3) The Simpson index, Shannon-Wiener index, richness index and McIntosh index gradually increased in the period from 2015 to 2017, following the order: intermediate altitude>high altitude>low altitude.(4) Soil microbiomass carbon, microbial respiration, microbial metabolic entropy, soil glycosidase, chitinase, leucine aminopeptidase, alkaline phosphatase, phenol oxidase and peroxidase assay gradually increased during the period from 2015 to 2017, following the order: intermediate altitude>high altitude>low altitude.(5) Soil microbial biomass carbon, microbial respiration and soil microbial metabolic entropy gradually increased in the period from 2015 to 2017, following the order: intermediate altitude>high altitude>low altitude.(6) Redundancy analysis indicates that the soil microbial carbon metabolism and enzyme activity are different along an altitudinal gradient, and microbial respiration, microbial metabolic entropy have the more positive contribution to soil microbial carbon metabolism, which are the main driving factors on soil microbial carbon metabolism. Soil total carbon and soil total nitrogen are the reasons for variation of soil microbial communities along an altitudinal gradient.