喀斯特生态系统中乔木和灌木林根际土壤微生物生物量及其多样性的比较

我国喀斯特区域面积分布较广,而喀斯特生态系统的退化已成为当前西南地区面临的严重的生态问题。本研究选取贵州中部两种不同植被类型的生态系统—乔木林和灌木林,以乔木林中的白栎、园果化香和灌木林中的火棘、竹叶椒等主要优势树种为对象,研究不同的植物树种对根际土壤微生物生物量及其细菌群落结构的影响。结果显示:乔木林系统中根际土壤微生物生物量碳、氮显著性高于灌木林,植物的根际效应在乔木林中表现更为显著;同时乔木林中的优势树种通过根系分泌物的作用显著提高根际土壤细菌多样性指数,而灌木林中优势树种的根际土壤微生物量及多样性均未表现出明显的根际效应。因此,植被的演替通过改变土壤微生物的特性影响植物-微生物-土壤之间的物质和能量循环,进一步影响喀斯特生态系统的稳定和健康功能。

Comparison of microbial biomass and community structure of rhizosphere soil between forest and shrubbery in karst ecosystems

The degradation of karst ecosystem in Southwest China has been a serious ecological problem. To research the effects of different vegetation types on microbial biomass and bacterial community structures of rhizosphere soil, we selected the dominant tree species, Quercus fabri, Platycarya longipes in forest and Pyracantha fortuneana, Zanthoxylum planispinum in shrubbery, in two typical karst ecosystems. The results showed that microbial biomass carbon and nitrogen of rhizosphere soil in forest were higher than those in shrubbery, and the effects of the dominant tree species of Quercus fabri and Platycarya longipes in forest was more obvious compared to shrubbery. Bacterial diversity indexes of rhizosphere soil of dominant tree species in forest were significantly higher than those of bulk soil by the root exudates, but in shrubbery, there was no significant difference in both microbial biomass and diversity indexes between rhizosphere soil and bulk soil. It suggests that the vegetation succession could affect the cycle of substance and energy among plant-microbe-soil system by changing the characters of soil microbe, even affect the stabilization and health of karst ecosystems.