To understand the role of denitrifying microbes during vegetation recovery in karst regions, we determined the basic physicochemical properties and abundance of denitrifying microbial functional genes (nirS, nirK, fungal nirK, p450nor, and nosZ) of 13 collected soil samples under three land use types (cropland, grassland, and plantation) in Northwest Guangxi, and investigated the changes in the abundance of denitrifying microbial functional genes and their driving factors. Results showed that soil pH, soil organic carbon, total nitrogen (TN), and exchangeable calcium (Caexe) in plantation soil were significantly higher than those in cropland and grassland. The abundance of nirS, nirK, p450nor, and nosZ in plantation soil were significantly higher than those in cropland and grassland. Soil pH, TN, and Caexe were positively correlated with the abundance of denitrifying functional genes nirS, nirK, and p450nor. Results of redundancy analysis showed that soil Caexe, pH and TN were the primary factors influencing the abundance of denitrifying functional genes, which accounted for 34.1%, 20.1%, and 16.1% of the total variation, respectively. Such a result suggested that Caexe was the main driver of changes in denitrifying functional genes under different land use types. Overall, vegetation restoration (plantation) could effectively increase soil denitrifying microbe genes abundance in the karst region of Northwest Guangxi, and consequently influence soil nitrogen cycling.
为深入了解反硝化微生物在喀斯特区域植被恢复过程中的重要作用,本研究在桂西北采集3种土地利用方式(农田、草地、人工林)的13个土壤样品,测定土壤基本理化性质和反硝化微生物功能基因(nirS、nirK、Fungal nirK、p450nor和nosZ)丰度,研究不同土地利用方式下土壤反硝化微生物功能基因丰度变化及其驱动因素。结果表明: 人工林土壤的pH、有机碳、全氮(TN)、交换性钙(Caexe)含量显著高于农田和草地;其土壤nirS、nirK、p450nor和nosZ丰度也显著大于农田和草地。相关性分析显示,pH、TN和Caexe与反硝化功能基因nirS、nirK和p450nor丰度呈显著正相关。冗余分析发现,Caexe、pH和TN是反硝化功能基因丰度变化的主要影响因素,分别占总解释变量的34.1%、20.1%和16.1%,表明Caexe是驱动不同土地利用方式下反硝化功能基因变化的主要因子。综上,桂西北喀斯特区域植被恢复(人工林)能够显著增加土壤反硝化微生物基因丰度,进而影响该生态系统的氮循环过程。.
Keywords: denitrifying bacteria; denitrifying fungi; exchangeable calcium; land use pattern.