叶尔羌河流域荒漠河岸林胡杨根际微生物数量时空变化及其与根际土壤环境因子的关系

Temporal and spatial variation of numbers of rhizosphere microorganisms of Populus euphratica in desert riparian forest of Yarkant River Basin and their relationships with rhizosphere soil environmental factors

以叶尔羌河流域荒漠河岸林胡杨(Populus euphratica Oliv.)为研究对象,对不同河段、土层和季节的根际细菌、放线菌和真菌数量进行比较,对根际土壤环境因子特征进行分析,并对根际土壤环境因子与根际微生物数量进行Pearson相关性分析。结果表明:3个河段的根际细菌、放线菌和真菌数量的均值分别为49.50×10^(6)、8.32×10^(6)和4.52×10^(6)cfu·g^(-1),3种根际微生物数量的变异系数均在25%以上;并且,3种根际微生物数量在中游与上游和中下游间存在极显著(P<0.01)差异,但在上游与中下游间无显著差异。夏季3个河段及秋季上游和中游的3种根际微生物数量均随着土层深度增加而增大。比较而言,秋季各河段的根际细菌、放线菌和真菌数量高于夏季相应河段,并且,2个季节的根际微生物数量均表现为细菌最多、真菌最少,夏季和秋季的根际细菌数量分别占相应季节根际微生物总数的89.7%和72.4%。土壤环境因子检测结果显示:上游、中游和中下游的根际土壤总盐含量在夏季分别为0.8705、3.7186和2.6722 g·kg^(-1),在秋季分别为3.4367、2.9662和4.5915 g·kg^(-1),属于轻度盐渍化土壤,且根际土壤阳离子主要为K^(+)和Na^(+),阴离子主要为Cl^(-)和SO_(4)^(2-);除pH值外,其余9个土壤环境因子的变异系数多在20%以上。相关性分析结果表明:根际细菌数量与根际土壤含水率和CO_(3)^(2-)含量分别呈极显著正相关和极显著负相关;根际放线菌和真菌数量与根际土壤总盐含量和CO_(3)^(2-)含量呈极显著负相关,与根际土壤Ca^(2+)含量呈显著(P<0.05)负相关,与根际土壤HCO_(3)^(-)含量、含水率和pH值呈极显著正相关,与根际土壤Cl^(-)含量呈显著正相关,此外,根际放线菌数量还与根际土壤K^(+)和Na^(+)的总含量呈显著正相关。研究结果显示:叶尔羌河流域荒漠河岸林胡杨根际微生物数量分布极不均匀,具有明显的垂直分布特征和季节变化特征,而且其分布受到根际土壤环境因子的影响,其中,根际土壤放线菌和真菌数量受影响较大。

Taking Populus euphratica Oliv.in desert riparian forest of Yarkant River Basin as research object,the numbers of rhizosphere bacteria,actinomycetes,and fungi of different reaches,soil layers,and seasons were compared,the characteristics of rhizosphere soil environmental factors were analyzed,and the Pearson correlation analysis was performed between rhizosphere soil environmental factors and numbers of rhizosphere microorganisms.The results show that the means of numbers of rhizosphere bacteria,actinomycetes,and fungi are 49.50×106,8.32×106,and 4.52×106 cfu·g^(-1),respectively,the coefficients of variation of numbers of three types of rhizosphere microorganisms are all greater than 25%;in addition,there are extremely significant(P<0.01)differences in numbers of three types of rhizosphere microorganisms between middle reach and upper and lower-middle reaches,but there is no significant difference between upper reach and lower-middle reach.Numbers of three types of rhizosphere microorganisms in three reaches in summer and those in upper and middle reaches in autumn all increase with the increase of soil layer depth.In comparison,numbers of rhizosphere bacteria,actinomycetes,and fungi in each reach in autumn are larger than those in corresponding reach in summer,in addition,numbers of rhizosphere microorganisms in the two seasons all show that bacteria are the most and fungi are the least,and numbers of rhizosphere bacteria in summer and autumn account for 89.7%and 72.4%of the total numbers of rhizosphere microorganisms in corresponding seasons,respectively.The test results of soil environmental factors show that the total salinities of rhizosphere soil in upper,middle,and lower-middle reaches in summer are 0.8705,3.7186,and 2.6722 g·kg^(-1),respectively,and those in autumn are 3.4367,2.9662,and 4.5915 g·kg^(-1),respectively,which belongs to mild salinization soil.The cations in the rhizosphere soil are mainly K^(+)and Na^(+),and the anions are mainly Cl^(-)and SO_(4)^(2-);except pH value,the coefficients of variation of the other nine soil environmental factors are mostly greater than 20%.The correlation analysis result shows that number of rhizosphere bacteria shows an extremely significant positive correlation and an extremely significant negative correlation with rhizosphere soil water content and CO_(3)^( 2-) content,respectively;numbers of rhizosphere actinomycetes and fungi show extremely significant negative correlations with rhizosphere soil total salinity and CO_(3)^( 2-) content,a significant(P<0.05)negative correlation with rhizosphere soil Ca^(2+)content,extremely significant positive correlations with rhizosphere soil HCO_(3)^(-)content,water content,and pH value,and a significant positive correlation with rhizosphere soil Cl^(-)content,in addition,number of rhizosphere actinomycetes shows a significant positive correlation with the total content of K^(+)and Na^(+)in rhizosphere soil.It is suggested that the distribution of numbers of rhizosphere microorganisms of P.euphratica in desert riparian forest of Yarkant River Basin is extremely uneven,which has evident vertical distribution pattern and seasonal variation characteristics,and its distribution is affected by rhizosphere soil environmental factors,in which,numbers of rhizosphere actinomycetes and fungi are greatly affected.