Data_Sheet_1_Agriculture by Irrigation Modifies Microbial Communities and Soil Functions Associated With Enhancing C Uptake of a Steppe Semi-Arid Soil in Northern Patagonia.PDF

The transformation of the semiarid steppe soil after 5 years of intensive irrigated agriculture in Northern Patagonia was analyzed in an on-farm study. The private grower venture used conservative practices, including no-till to maintain soil structure, high crop rotation and cover crops. To characterize steppe soil changes by irrigated agriculture, we analyzed the enzymatic activities involved in the biogeochemical cycles (carbon, nitrogen, phosphorus and sulfur), the whole soil fatty acids profile, the state of soil aggregation, and the bacterial and fungal microbiota through DNA sequencing methods. After 5 years of management, irrigated agriculture soil increased organic matter (25–33%), enzymatic activities -Cellobiose-hydrolase (60–250%), Phosphatase (35–60%), Xylanase (101–185%), Aryl-sulphatase (32–100%), Chitinase (85%), β-Glucosidase (61–128%), Leucine-aminopeptidase (138%)—depending on soil series, and macro-aggregate formation at the expense of the abundance of micro-aggregates in the first 0–5 cm of soil. Whole soil fatty acids profiles changed, enhancing mono-unsaturated, branched, cyclic and methylated fatty acids. Microbial communities showed significant differences between irrigated agriculture sites and pristine valleys. The richness-based alpha-diversity established increased bacterial communities but decreased fungal communities in cultivated soil. Indicators selected using the LEfSe method revealed the bacterial taxa Acidothermus, Conexibacter and Thermoleophilum, associated with semiarid steppe soil while Asticcacaulis, Aquicella and Acromobacter with irrigated agriculture. Ascomycota Phylum changed its community composition, being both taxa Aspergillus and Alternaria reduced while Stagonospora and Metarhizium were enhanced in irrigated agriculture. Taxa belonging to Acidobacteria, Chloroflexi, and Betaproteobacteria, that were enriched in irrigated agriculture soils, were associated with higher capture of C but smaller values of aggregation, while taxa abundant on steppe soils belonging to Actinobacteria, Alphaproteobacteria, and Firmicutes were positively associated with soil aggregation but negatively with C uptake.

本田间研究分析了巴塔哥尼亚北部半干旱草原土壤经过5年集约化灌溉农业后的演变情况。该私人种植企业采用了保护性耕作措施，包括免耕以维持土壤结构、多元化作物轮作及覆盖作物种植。为表征灌溉农业对草原土壤的改变，我们分析了参与生物地球化学循环（碳、氮、磷、硫循环）的酶活性、全土壤脂肪酸谱、土壤团聚体状态，以及通过脱氧核糖核酸（DNA）测序技术解析的细菌与真菌微生物群落。经过5年的耕作管理后，灌溉农业土壤的有机质含量提升25%~33%，相关酶活性亦发生显著变化：纤维二糖水解酶（Cellobiose-hydrolase）提升60%~250%、磷酸酶（Phosphatase）提升35%~60%、木聚糖酶（Xylanase）提升101%~185%、芳基硫酸酯酶（Aryl-sulphatase）提升32%~100%、几丁质酶（Chitinase）提升85%、β-葡萄糖苷酶（β-Glucosidase）提升61%~128%、亮氨酸氨肽酶（Leucine-aminopeptidase）提升138%，具体提升幅度因土壤系列而异；同时在0~5cm表层土壤中，大团聚体形成量增加，而微团聚体丰度降低。全土壤脂肪酸谱发生改变，单不饱和脂肪酸、支链脂肪酸、环状脂肪酸及甲基化脂肪酸占比得以提升。微生物群落在灌溉农业样地与原生河谷样地间存在显著差异。基于丰度的α多样性分析显示，耕作土壤中的细菌群落丰富度提升，而真菌群落丰富度则出现下降。通过线性判别分析效应大小（LEfSe）方法筛选得到的指示类群表明：酸热菌属（Acidothermus）、锥杆菌属（Conexibacter）及嗜热脂杆菌属（Thermoleophilum）与半干旱草原土壤相关；而柄杆菌属（Asticcacaulis）、水胞菌属（Aquicella）和无色杆菌属（Acromobacter）则与灌溉农业土壤相关。子囊菌门（Ascomycota）的群落组成发生变化：曲霉属（Aspergillus）与链格孢属（Alternaria）的丰度降低，而柱隔孢属（Stagonospora）和绿僵菌属（Metarhizium）的丰度在灌溉农业土壤中得到提升。隶属于酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）及β-变形菌纲（Betaproteobacteria）的类群在灌溉农业土壤中富集，它们与更高的碳摄取量相关，但与土壤团聚体指标呈负相关；而草原土壤中占优势的放线菌门（Actinobacteria）、α-变形菌纲（Alphaproteobacteria）及厚壁菌门（Firmicutes）类群则与土壤团聚体呈正相关，与碳摄取量呈负相关。