增温对结皮土壤系统氮转化速率及微生物生物量碳氮与酶活性的影响

Effects of Warming on Soil Nitrogen Transformation Rates,Microbial Biomass Carbon and Nitrogen and Enzyme Activity in Crust-covered Soil System

探究增温对结皮土壤系统氮转化速率及微生物生物量碳氮与酶活性的影响,从不同水平(功能基因→微生物生物量→酶活性)揭示结皮土壤系统氮转化特征对增温的响应机制,为进一步认知未来气候变化背景下藓类结皮在土壤氮循环中的生态功能提供理论依据。以藓类结皮土壤为研究对象,采用野外培养原状土柱的方法,研究了温带荒漠生态系统藓类结皮土壤氮转化速率、微生物生物量、酶活性和功能基因对增温的响应。结果表明,增温和土壤类型对土壤净氮转化速率(净氨化速率、净硝化速率和净氮矿化速率)、酶活性(N-乙酰-β-D-葡萄糖苷酶和脲酶)、微生物生物量碳和氮转化功能基因(gdh、hao和amo A)丰度具有显著影响且两者间存在明显交互作用;此外,与对照相比,增温后藓类结皮土壤净氨化速率、净硝化速率和净氮矿化速率分别降低49.5%、63.2%和59.7%;土壤酶活性(N-乙酰-β-D-葡萄糖苷酶、亮氨酸氨基肽酶和脲酶)和微生物生物量碳氮均显著降低;除gdh基因外,增温显著抑制了藓类结皮土壤ureC、hao和amoA丰度;相同处理下,藓类结皮土壤净氮转化速率、酶活性、微生物生物量碳氮和氮转化功能基因丰度均显著高于无结皮土壤。综上,增温通过降低土壤酶活性、微生物生物量和功能基因丰度来抑制土壤氮转化过程,而藓类结皮的退化丧失了对土壤微环境的调节作用,进而加速了该过程。

【Objective】Soil nitrogen transformation is a microbially-mediated biogeochemical process that though strongly influenced by global climate change,is an effective indicator of soil.Nitrogen supplying capacity and soil nitrogen availability of a terrestrial ecosystem.Therefore,the study of characterizing soil nitrogen transformation helps to thoroughly and deeply understand the productivity and nitrogen cycling process in an ecosystem.Biocrusts,making up over 40%of the total area of the land surface cover in the arid region,is an important type of earth surface cover in desert,and a major compositions of the desert surface landscapes in the semi-arid and arid regions as well,so it plays a vital regulatory role in nitrogen cycling in arid area.This study aimed to explore responses of nitrogen transformation rate,microbial biomass carbon and nitrogen and enzyme activity in the crust-covered soil system to global warming,and reveal mechanisms of the responses from different levels(functional gene→microbial biomass→enzyme activity)in an attempt to provide a theoretical basis for studies in future to identify ecological functions of moss crusts in soil nitrogen cycling in temperate desert ecosystems under the background of climate warming.【Method】This study explored responses of soil nitrogen transformation rates,microbial biomass,enzyme activities and functional genes to warming in temperate desert ecosystems with undisturbed soil columns with moss crust cover on the surface collected from the field.【Result】Results show that soil net nitrogen transformation rates(net ammoniation rate,net nitrification rate and net nitrogen mineralization rate),enzyme(N-acetyl-β-D-glucosidase and urease)activities,abundance of microbial biomass carbon/nitrogen transformation function genes(gdh,hao and amoA)responded significantly to warming and soil type,and interactions between the two were apparent.Compared with CK,warmed moss covered soil was 49.5%,63.2%,and 59.7%,respectively,lower in net ammonification rate,net nitrification rate,and net nitrogen mineralization rate and lower in enzyme(N-acetyl-β-D-glucosidase,leucine aminopeptidase and urease)activities.Microbial biomass carbon and nitrogen,and in abundance of ureC,hao and amoA,too(gdh exclusive).Moss crust covered soil was higher in net nitrogen transformation rate,enzyme activity,microbial biomass carbon and nitrogen,and nitrogen transformation function gene abundance than mossless soil under the same treatment.【Conclusion】To sum up,warming significantly inhibits soil nitrogen transformation process by decreasing enzyme activity,microbial biomass,and functional gene abundance,while degradation of the moss crust weakens its role in regulating the soil environment,thus accelerating the process.