百菌清对落叶松人工防护林土壤微生物群落的影响

利用稀释平板法和Biolog-Eco检测技术,分析了喷施百菌清对落叶松人工防护林土壤微生物群落的影响。结果表明,土壤微生物中细菌数量占据绝对优势,其数量直接影响落叶松人工防护林土壤微生物总量的变化趋势。总体上,百菌清对细菌的数量具有抑制作用。喷洒后0d,仅抑制表层与上层(0-10cm)土壤细菌的增殖;喷洒后2个月,对表层与上层土壤细菌的抑制作用减弱,而喷洒后4个月时,其抑制作用最强。喷洒后0d与2个月时,百菌清对表层与上层土壤真菌数量的增殖均具有促进作用。喷洒后2个月、4个月时均对下层土壤放线菌数量具有抑制作用。将土壤3大类群微生物数量、土壤理化指标及群落多样性指数进行相关分析表明,土壤中有效磷和速效钾与放线菌数量、水解氮与细菌数量存在显著正相关性,而与群落多样性无显著相关性。喷洒百菌清2个月后,对表层土壤微生物群落碳源利用率的影响不显著,而对上层(0-10cm)土壤微生物存在显著影响,下层(10-20cm)土壤微生物群落的碳源利用率在百菌清喷洒2个月与4个月后具有显著差异;而不同土层微生物群落对碳源利用率的差异不显著。微生物群落利用31种碳源的主成分分析表明,喷洒百菌清后,微生物群落利用单一碳源的能力显著提高,且喷洒2个月后微生物群落对某些碳源如肝糖与2-羟基苯甲酸等的利用率明显增加。方差分析表明,喷洒百菌清后,不同作用时间及不同处理,不同土层间土壤微生物对碳源的利用率具有显著差异。喷洒百菌清前(5月)土壤微生物对多聚物与氨基酸、碳水类、芳香类及胺类的利用率差异较大(P<0.05),且对多聚物的利用率最高;处理组的表层土壤微生物对碳源的利用率高于其它处理组;而喷洒2个月后,对胺类、芳香类的利用率与其它4类碳源具有显著差异。

Effect of chlorothalonil on soil microbial communities of Larix artificial shelter-forest

Chlorothalonil is considered to be a non-selective fungicide and used commonly to control a broad spectrum of plant diseases. Hence, it is important to study its impact on ecological safety. In this study, the recommended dosage of chlorothalonil was sprayed on the soil of larch artificial shelter-forest to evaluate the impact of the fungicide on soil microbial communities. At the same time, analysis of correlations between soil diversity and propertities showed that it can provide basic data of the influence to soil microbial community and thus, provide basic foundings of scientifical usage and crisis managament for the pesticide. Using dilution-plate method, data of culturable microbial populations, soil properties and microbial functional diversity indexes were collected before spraying fungicide, 0 MAT, 2 MAT, 4 MAT and 12 MAT respectively. The results showed that bacterium was the dominant species among soil microbes whose number directly affected the dynamics of total soil microbial amount of larch artificial shelter-forest. As a whole, chlorothalonil had inhibitory effect on the proliferation of the soil bacteria. The inhibition occurred mainly in both the surface and the upper-layer (0-10cm) soils on 0 day after spraying.Moreover, the inhibitory effect on the bacteria in surface soil was significantly different from that in upper soil two months after spraying and the difference reached the climax four months later. At the time of both 0 MAT and 2 MAT, chlorothalonil facilitated the proliferation of the fungi in both the surface and the upper-layer (0-10cm) soils. Nevertheless, it showed little influence on the under layer soil fungi populations. Although the actinomycetes amount in both the surface and upper layer(0-10cm) soils were decreased as a result of the applicaton of chlorothalonil, the inhibition was weaker than those on bacterial populations. Correlation analysis between three main groups of microbial populations, soil propertities and diversity indices showed that the contents of both the effective phosphorus and available potassium in the soil were significantly positively correlated to the numbers of soil actinomycetes. The bacterium count was correlated positively to the content of soil hydrolysable nitrogen as well, whereas not to the soil microbial community diversity. Biolog-Eco Plate detecting showed that, 2 MAT, chlorothalonil had no significant effect on the carbon conversion ratio of the surface soil microbes while significant to that of the upper-layer microbes. And there was significant difference on the carbon conversion ratios of the under-layer microbes between two experiments tested on two months and four months after spraying respectively. Nevertheless, there was no significant difference between different soil layers. Principal component analysis of 31 carbon sources showed that the ability of single carbon conversion ratio of soil microbial community strikingly improved after chlorothalonil spaying. Furthermore, two months after spraying, the conversion ratios of certain carbon, e.g. Glycogen and 2-Hydroxy Benzoic Acid, were strengthened significantly. Analysis of variance proceeded to find that there existed distinguished differences between different action times,different treatments and different soil layers for the ability of single carbon conversion ratio of soil microbial community. There were significant differences among the utilization of Amino acids,Carbohydrates,Polymers,Phenolic and Amines(P<0.05) before spraying,in addition to this,Polymers had a highest availability. The ability of single carbon conversion ratio of surface soil microbial community was higher than other layers whereas the utilization two months after applying chlorothalonil was significantly different between Phenolic,Amines and the other four single carbon sources.