石灰土演替过程中颗粒态有机质和矿物结合态有机质的微生物群落特征

Characteristics of soil microbial communities in particulate organic matter and mineral-associated organic matter along calcareous succession process

摘要:

碳酸盐岩经风化作用并在地形、植被、气候、时间及生物等因素的影响下逐渐演替出黑色石灰土、棕色石灰土、黄色石灰土和红色石灰土。【目的】研究不同演替阶段石灰土颗粒态有机质(particulate organic matter, POM)和矿物结合态有机质(mineral-associated organic matter, MAOM)的微生物群落特征，为岩溶土壤有机质稳定机制研究提供理论依据。【方法】以广西弄岗国家级自然保护区的黑色石灰土、棕色石灰土、黄色石灰土和红色石灰土为研究对象，运用湿筛法将土壤有机质(soil organic matter, SOM)分为POM和MAOM，分析其理化性质以及微生物群落特征。【结果】石灰土演替过程中POM和MAOM的有机碳、总氮、交换性钙含量均呈下降趋势，且MAOM的C/N均大于POM，POM的C/P均大于MAOM。细菌α多样性在黑色石灰土POM和MAOM中最高，且四类石灰土MAOM的真菌多样性比POM要高。Acidobacteria、Proteobacteria、Ascomycota均为石灰土演替过程中POM和MAOM的优势菌门。总磷是影响石灰土演替过程中POM和MAOM细菌群落变化的关键因子，溶解性有机碳和土壤有机碳分别是影响石灰土演替过程中POM和MAOM真菌群落变化的关键因子。POM和MAOM中黑色石灰土的微生物可能发生了生态位分化，随着石灰土演替细菌与真菌更倾向于协作关系。【结论】岩溶土壤演替过程中POM和MAOM的养分及微生物多样性降低，POM可能是微生物养分的主要来源，MAOM更有利于碳的长期稳定积累。本研究可为岩溶土壤演替过程中微生物在有机质形成过程中的作用提供理论依据。

Abstract:

After undergoing weathering and being influenced by topography, vegetation, climate, time and biology, the carbonate rocks gradually evolved into black calcareous soil, brown calcareous soil, yellow calcareous soil and red calcareous soil. [Objective] This study aims to investigate the microbial community characteristics of particulate organic matter (POM) and mineral-associated organic matter (MAOM) in calcareous soil at different succession stages, providing a theoretical basis for the study of organic matter stability mechanism in karst soil. [Methods] Black calcareous soil, brown calcareous soil, yellow calcareous soil, and red calcareous soil from the Nonggang Nature Reserve in Guangxi were chosen as the research objects, and soil organic matter (SOM) was divided into POM and MAOM by using wet screening method. The soil physicochemical properties and soil microbial community characteristics were analyzed. [Results] During the succession process of calcareous soil, the soil organic carbon, total nitrogen, and exchangeable calcium contents of POM and MAOM showed a decreasing trend, and the C/N of MAOM was greater than that of POM, whereas the C/P of POM was greater than that of MAOM. The bacterial diversity was higher in black calcareous soil of POM and MAOM, and the diversity of bacteria and fungi in the four type calcareous soil of MAOM was higher than that in POM. Acidobacteria, Proteobacteria, and Ascomycota were the dominant phyla in POM and MAOM along the succession process of calcareous soil. Total phosphorus was a key factor affecting the changes of bacterial communities in POM and MAOM during calcareous soil succession, while dissolved organic carbon and soil organic carbon were key factors affecting the changes of fungal communities in POM and MAOM during calcareous soil succession, respectively. The microorganisms from black calcareous soil in POM and MAOM may have undergone ecological niche differentiation, and bacteria and fungi tend to cooperate more closely along calcareous soil succession. [Conclusion] During the succession process of calcareous soil, the nutrients and microbial diversity of POM and MAOM decrease. POM may be the main source for microbial nutrients, and MAOM is more conducive to be the long-term stable accumulation of carbon. This study can provide a theoretical basis for the role of microorganisms in the formation of organic matter during the succession process of karst soil.