贺兰山不同海拔植被下土壤微生物群落结构特征

Abstract

为明确海拔变化对干旱区山地森林土壤微生物群落的影响, 揭示环境因子改变后土壤微生物群落结构特征及影响因素。对贺兰山5个海拔梯度土壤理化性质进行测定, 同时采用磷酸脂肪酸(PLFA)图谱法分析土壤微生物群落组成, 通过主成分分析、冗余分析(RDA)探究土壤理化性质与土壤微生物群落相对丰度之间的相关关系。结果表明：土壤养分含量在不同海拔之间差异性显著(P < 0.05), 土壤有机碳和全氮含量随海拔的升高而升高, 全磷含量随海拔升高先升高再降低再升高；土壤微生物量随海拔升高先升高后降低, 土壤微生物的相对丰度在不同海拔之间存在差异(P < 0.05)；主成分分析表明, 与第1主成分相关性较强的微生物类群为革兰氏阳性细菌(G⁺)、革兰氏阴性细菌(G^-)和真菌；与第2主成分相关性较强的微生物类群为放线菌、原生动物和非特异性细菌。非特异性细菌和真菌与各土壤因子之间均有显著相关关系, 而放线菌、G⁺和G^-与各土壤因子相关性较弱, 原生动物与土壤全磷含量的关系密切。海拔是影响特征微生物分布的重要因素, 特征微生物的含量和相对丰度随海拔的升高先升高后降低, 符合山地生态学中的“中部膨胀”理论。探明了贺兰山不同海拔土壤微生物结构特征及与土壤理化性质之间的相关关系, 对维持干旱区山地森林生态系统功能稳定及养分循环具有重要意义。;To understand the impacts of altitude change on soil microbial community in mountain forest in arid region, and to reveal the structural characteristics and influencing factors of soil microbial community after environmental factors change. In this study, the physicochemical properties of soil were measured at five altitudinal gradients in Helan Mountain, and the composition of soil microbial community was determined using phospholipid fatty acids (PLFA) spectrum analysis. The correlation between soil physicochemical properties and the abundance of soil microbial community was explored by principal component analysis and redundancy analysis. The results showed that soil nutrients were significant difference at different altitudes (P < 0.05). The content of soil organic carbon and total nitrogen increased with the increase of altitude. The total phosphorus content increased first, then decreased and increased with altitude. The content of soil microorganism first increased and then decreased with altitude, and the abundance of soil microorganism was significant difference among different altitudes (P < 0.05). Principal component analysis showed that the microbial groups, which play a major role on first principal component, were gram-positive bacteria (G⁺), gram-negative bacteria (G^-) and fungi, and which play a major role on second principal component, were actinomycetes, protozoa and non-specific bacteria. Non-specific bacteria and fungi had significant correlation with soil factors, actinomycetes, G⁺ and G^- bacteria had weak correlation with soil factors, while protozoa had close relationship with soil total phosphorus content. Altitude was an important factor affecting the distribution of characteristic microorganisms. The content and abundance of characteristic microorganisms first increased and then decreased with the increase of altitude, which basically accorded with the theory of central expansion in mountain ecology. This study explored the relationship between soil microbial structure characteristics and soil physicochemical properties at different altitudes in Helan Mountain, which is great significance for maintaining the functional stability and nutrient cycle of mountain forest ecosystem in arid areas.