长期养分添加对贝加尔针茅草原土壤微生物群落的影响

土壤微生物是土壤生态系统的重要组成部分,是土壤生态系统物质循环和能量流动的主要参与者,在维持土壤生态系统过程和功能方面发挥着关键作用。以内蒙古贝加尔针茅草原为研究对象,采用磷脂脂肪酸(PLFA)技术,探讨连续12年氮(N)、磷(P)、钾(K)养分单一添加和复合添加条件下草地土壤理化性质、微生物群落结构特征的变化及其主要影响因素。结果表明,长期养分添加条件下,土壤有机碳和全氮均无显著变化,但磷(P、NP、PK、NPK)和钾(K、NK、PK、NPK)添加处理分别显著提高了土壤速效磷和速效钾含量(P < 0.05)。单一氮添加显著增加了土壤硝态氮和铵态氮含量,并显著降低了土壤pH值(P < 0.05)。单一磷和钾添加均提高了土壤细菌、真菌、放线菌和总PLFA含量,而单一氮添加和复合养分添加(NP、NK、PK、NPK)均显著降低了以上指标的含量(P < 0.05)。此外,各养分添加处理均未显著改变革兰氏阳性细菌与革兰氏阴性细菌比(G⁺/G^-),但含氮的复合添加处理(NP、NK、NPK)均显著降低了真菌与细菌比 (F/B) (P < 0.05)。相关性分析结果表明,多种微生物PLFA含量与速效磷和铵态氮显著负相关,与土壤pH值显著正相关。基于冗余分析和随机森林模型分析发现土壤pH值和土壤磷含量是影响土壤微生物群落特征的主要驱动因素。综上,长期养分添加显著改变了土壤速效养分含量和土壤pH值,并显著影响了土壤微生物群落结构。

Effects of long-term nutrient addition on microbial community in soil of Stipa baicalensis steppe in the Inner Mongolia, China

Soil microbes are an important component of terrestrial ecosystems connecting energy flows and matter cycles between the atmosphere and the soil. They play crucial roles in maintaining ecosystem function by driving a variety of complex ecological processes in soil. Here we report a field experiment on Stipa baicalensis steppe in the Inner Mongolia. The phospholipid fatty acids (PLFA) method was used to explore the effects of long-term different nutrient treatments (i.e. N, P, K in isolation and NP, NK, PK, and NPK in combination) on soil physical and chemical properties and microbial community structure. The results showed that the long-term nutrient addition did not significantly alter soil organic carbon and total nitrogen content, while P addition (P, NP, PK, NPK) and K addition (K, NK, PK, and NPK) significantly increased soil available phosphorus and available potassium content, respectively (P < 0.05). Single-N addition significantly increased soil ammonium nitrogen and nitrate nitrogen contents, but soil pH value decreased significantly. To a certain extent, Single-P and Single-K addition enhanced the total PLFA contents, the PLFA contents of bacteria, fungi, and actinomycetes. The Single-N and Multiple nutrient (NP, NK, PK, and NPK) addition significantly decreased the total PLFA contents, the PLFA contents of bacteria, fungi and actinomycetes. There were no significant differences under different nutrient addition treatments for the PLFA ratio of Gram-positive bacteria and Gram-negative bacteria (G⁺/G^-), while multiple nutrient (NP, NK and NPK) significantly decreased the PLFA ratio of fungi and bacteria (F/B). Correlation analysis indicated that soil microbial groups were positively correlated with soil available phosphorus and ammonium nitrogen content, and soil pH were negatively correlated with soil microbial groups. Redundancy analysis (RDA) and Random Forest (RF) analysis showed that soil pH and phosphorus content were found to be significant driving factor affecting soil microbial community structure. In summary, the long-term nutrient addition significantly changed soil available nutrients and soil pH, and then affected the microbial community structure.