昆虫肠道菌对反枝苋的除草活性筛选及菌株JC-03的初步鉴定

利用平板分离法从多种昆虫肠道中分离出14株昆虫肠道菌,活性筛选表明从大黑金龟子肠道分离出的JC-03菌株粗提物对反枝苋具有较好的除草活性,进一步研究表明其活性物质主要集中在中等极性的乙酸乙酯提取物中。安全性实验表明JC-03菌株粗提物对常见作物(油菜、大豆、西红柿、辣椒)的安全性较高。通过形态学特征观察和5.8S rDNA测序分析,初步确定该菌株为赤霉菌(Gibberella intermedia)。JC-03菌株作为微生物源除草剂值得进一步研究。     

Effect of soil management on Heterorhabditis bacteriophora GPS11 persistence and biological control in a vegetable production system

Soil habitat conditions that promote abundance and persistence of entomopathogenic nematodes (EPNs) might be encouraged by reduced tillage and compost amendments. We hypothesized that altered soil management with reduced tillage, cover crops (clover and barley), and compost (100 kg of N/ha), would increase survival and biocontrol services of EPNs, compared with conventional management. Field trials were conducted at the Ohio Agricultural Research and Development Center Muck Crops Research Station, Huron County, OH in 2010 and 2011. Plots were planted with carrots. EPNs, Heterorhabditis bacteriophora GPS11, were released and their survival was compared between the two soil management regimes by sampling over a period of 8 weeks using in situ bait traps containing Galleria mellonella. Repeated measures analysis of variance did not show significant differences between the two soil management regimes in the pattern of H. bacteriophora survival over time or during any evaluation in either year, except 2 weeks after cadaver application in 2010 when the EPN population was significantly greater in the conventional than in the alternative soil management regime. Although treatment effects were generally not significant, statistically significant increase in nematode population densities between the 2 years of the study, despite generally poor weather conditions following EPN release in the second year, provide encouraging evidence that populations of these biological control agents could increase in vegetable production fields. However, longer periods may be required for clearly distinguishable increase in EPN population density, persistence, and biological control services in the alternative soil management treatments.     

Dissolved Organic Matter concentration and composition in the forests and streams of Olympic National Park, WA

Dissolved organic carbon (DOC) concentration and dissolved organic matter (DOM) character were investigated in soil water (15 and 40 cm) and streams at eleven sites in Olympic National Park. In addition, the effect of added nitrogen on soil water DOM concentration and composition was tested. Forested plots covering a gradient of precipitation, climate, slope, and aspect in Olympic National Park were fertilized with the addition of 20, 10 and zero (control) kg urea-N ha^–1 y^–1. Seven sites had the two different fertilizer treatments and control plots, while the additional four sites had no fertilizer treatments. Soil water DOC concentrations ranged from 0.5 mg C/L to 54.1 mg C/L, with an average value of 14.1 mg C/L. Streams had low DOC concentrations ranging from 0.2 mg C/L to 4.4 mg C/L, with an average value of 1.2 mg C/L. DOM composition was examined with regard to molar ratios, H:C, O:C and N:C, index of unsaturation, average carbon oxidation state, and specific absorbance. Fertilizer had no consistent effect on either DOM concentration or composition across the study sites. Soil depth influenced both DOM concentration and composition. Shallow soil water DOM had greater concentrations, higher specific absorbance, a higher degree of unsaturation, and had lower molar ratios compared to deep soil water samples. Overall, changes in DOM stoichiometry and specific absorbance as a function of soil depth were consistent despite the diversity of the forested study sites sampled.     

两种污泥连续施用对潮土重金属含量及酶活性的影响

采用盆栽土培试验,研究了工业污泥(化工厂底泥)及城市污水处理厂剩余污泥中重金属存在的形态与含量,以及两种污泥连续施用对潮土重金属含量及酶活性的影响。结果表明,两种污泥中的重金属主要是以非交换态存在,城市污水处理厂剩余污泥中总的重金属含量比工业污泥低,而重金属的有效性比工业污泥高;污泥的施用能增加潮土中脲酶的活性,多酚氧化酶及中性磷酸酶的活性与污泥的施用量有一定相关性,并与土壤中交换态Zn、Cu含量呈一定负相关,土壤多酚氧化酶及过氧化氢酶活性可作为土壤中重金属Zn污染的指示指标;污泥的施用有提高潮土中交换态Cu、Zn及Pb含量的趋势。     

土壤有机质概念和分组技术研究进展

土壤有机质一直是土壤学研究领域的重点,在过去的50年里,对土壤质量可持续性观念的增强和寻找快速判断人为因素对土壤质量影响方向指标的强烈愿望导致了土壤有机质的研究重点发生了急剧变化：对农业措施反映慢的土壤腐殖质类物质的研究正在退出土壤有机质研究领域,而侧重点逐渐转向了土壤中未受微生物作用或正在受微生物降解的有机残体;也出现了新的土壤有机质研究概念和对应测试手段：土壤有机质的比重分组、与有机质结合的土壤颗粒大小分组、土壤团聚体中的POM和iPOM以及土壤水溶性有机质和微生物体C等概念和测试手段被相继提了出来,土壤有机质的研究重点正在从土壤微生物的作用产物(腐殖质)向土壤微生物作用前的、具有部分生物活性的有机质(轻组有机质、砂粒组和粗粉砂粒组中的有机质、POM和iPOM)和完全具有生物活性的有机质(微生物体C和水溶性有机质)转移,这一过程与土壤有机质概念的拓展密不可分。     

土壤原生动物对环境污染的生物指示作用

土壤原生动物具有丰富的种类和巨大的生物量,在土壤生态系统中具有十分重要的地位．作为指示生物,土壤原生动物具有与其他土壤动物相比更独特的优势．研究它们的群落结构、数量及多样性动态变化,可以很好地评价和监测自然环境变化及人类活动带来的环境污染．本文根据国内外相关文献,简要概述了土壤原生动物在生态系统中的作用．对原生动物的生物指示物优势、土壤原生动物对环境因子响应和污染指示作用及对大气CO2浓度变化的响应等进行了论述,并对土壤原生动物在生态毒理诊断中的应用前景进行了展望．     

非饱和土壤水力参数的模型及确定方法

土壤水力参数的选取和确定是土壤中水分运动和污染物迁移预测的基础,本文在国内外研究成果的基础上,综述了土壤水力参数的模型(土壤水分特征曲线模型、土壤导水率模型)及其直接测定法和间接推求法,并比较了土壤水力参数的模型及确定方法的适用性与局限性,以便为生态环境建设和农业可持续发展研究中土壤水力参数的选取提供依据。     

水分胁迫对羊草光合产物分配及其气体交换特征的影响

 通过对典型草原优势植物种羊草(Leymus chinensis)的盆栽实验,模拟5个土壤水分梯度（分别为土壤持水量的75%～80%(对照)、60%～65%、50%～55%、35%～40%和25%～30% ）对羊草叶片相对含水量、光合速率、光合产物分配和种群CO2交换速率的影响。结果表明：随着土壤水分胁迫的增加,羊草叶片相对含水量呈先增加而后下降的单峰型变化,且在50%～55%处理下达到最大;叶片光合速率随着水分胁迫的增加而减小,且75%～80%、60%～65%、50%～55%的水分处理与35%～40%、25%～30%的水分处理的叶片光合速度日动态规律不同。羊草总生物量及根、鞘、叶生物量均随着水分胁迫的增加呈下降趋势。干旱促进早期羊草根的分配和根冠比增加, 但到后期却使它们降低, 表明羊草在受到较长期的持续干旱后通过增加根部的比重来提高抗旱性的能力逐渐降低。羊草根茎的生物量和分配随着土壤水分含量降低均呈现出先增加而后下降的趋势,羊草根茎的生物量在50%～55%处理下达最大（1.28 g·株-1）,而羊草根茎的分配在35%～40%处理下达最大（48.5%）。羊草种群CO2的净交换速率随着水分胁迫的增加而减小,其日交换量随着水分胁迫的增加而增加,且在60%～65%处理下达到最高,而后呈下降趋势,并在25%～30% 处理下为负值。研究结果表明,土壤持水量的40%可能是羊草对于水分变化响应的阈值。     

土壤水分对单性木兰幼苗光合特性的影响

2001年夏季(7月15-19日)和秋季(10月20-25日)分别测定了在3组土壤水分条件下(高WH、中WM和低WL3种土壤水分处理)单性木兰(Kmeriaseptentrionalis)叶片净光合速率(Pn)、气孔导度(Gs)、潜在水分利用效率(IntrinsicWUE)和叶绿素含量等特性。夏季和秋季土壤水分的减少均引起单性木兰叶片单位面积干重和叶绿素含量的降低。夏季,单性木兰的Pn均在上午900达到峰值,其日进程为鞍型格式,WH、WM和WL处理组的Pn分别为4.41±1.10、4.28±1.23和1.89±0.94μmolm-2s-1,土壤水分的降低限制了单性木兰叶片的Pn,它们的Gs和IntrinsicWUE的日进程与Pn相似。秋季,WH组的Pn在上午1200达到峰值,WM和WL组在900达到峰值,3组的Pn的日进程相似,都为单峰曲线格式。3组的Pn、Gs和IntrinsicWUE的日平均值都是秋季比夏季高。不管夏季和秋季,凡土壤水分低的,其Pn、Gs和IntrinsicWUE都低。因此,调节土壤水分将有助于促进单性木兰的生长和有效提高单性木兰的迁地保护。