黄山松土壤可溶性有机质对氮添加的响应及其与细菌群落的关联

Responses of soil dissolved organic matter to nitrogen addition and its correlation with bacterial communities in Pinus taiwanensis forest

为探究黄山松土壤可溶性有机质(DOM)数量和质量对短期氮(N)添加的响应及其与细菌群落的关联,在福建戴云山自然保护区设置不同N添加水平(0、40和80 kg N·hm^(-2)·a^(-1))试验,采用三维荧光与平行因子联用法,并结合高通量测序手段分别对土壤DOM和细菌群落进行分析。结果表明:与对照相比,N添加整体降低了0~10和10~20 cm土层可溶性有机碳(DOC)含量和DOM腐殖化指数(HIX),其中,高氮(80 kg N·hm^(-2)·a^(-1))添加下均显著降低。平行因子分析法进一步表明N添加下DOM中类腐殖质组分(C1、C2)的相对含量降低。此外,N添加减少了富营养细菌(变形菌门、酸微菌纲)的相对丰度,而增加了贫营养细菌(斯巴达杆菌纲)的相对丰度。富营养细菌的相对丰度与HIX、C1、C2呈显著正相关,与相对易分解的类富里酸组分(C3)呈显著负相关;而贫营养细菌的情况则相反。说明N添加下不同生活策略的细菌类群对DOM中难分解和易分解组分存在明显的偏好性。我们推测N沉降加剧背景下土壤微生物生活策略的转变可能有助于DOM组分的塑造。

We explored the responses of the quantity and quality of soil dissolved organic matter(DOM) to short-term nitrogen(N) addition across an addition gradient(0, 40, and 80 kg N·hm^(-2)·a^(-1)) and their correlation with bacterial communities in Pinus taiwanensis forest in the Daiyunshan Nature Reserve, Fujian, China. Soil DOM and bacterial community composition were measured using three-dimensional fluorescence and parallel factor analyses combined with high-throughput sequencing. The results showed that compared with the control, N-addition reduced the content of dissolved organic carbon(DOC) and the humification index(HIX) of DOM in the 0-10 and 10-20 cm soil layers, with significant reduction under the high N addition(80 kg N·hm^(-2)·a^(-1)). Results of parallel factor analysis further showed that the relative content of humus-like components(C1, C2) in DOM decreased following N addition. Short-term N addition reduced the relative abundance of copiotrophic bacteria(Proteobacteria and Acidimicrobiia), but increased the relative abundance of oligotrophic bacteria(Spartobacteria). The relative abundance of copiotrophic bacteria were positively correlated with the HIX and refractory humus-like components(C1, C2) and negatively correlated with the relatively easily decomposed fulvic acid-like component(C3), whereas the pattern was opposite for oligotrophic bacteria. It is indicated that bacterial communities with different life strategies had obvious preference for difficult-and easy-to-decompose components in DOM under N addition treatments. We speculated that the transformation of soil microbial life strategies under the background of increasing N deposition might alter DOM components.