黄河三角洲垦利县夏季土壤水盐空间变异及土壤盐分微域特征

黄河三角洲作为我国重要的后备土地资源区,土壤盐渍化问题突出,切实掌握季节性土壤水盐状况及其微域特征是该区土壤盐渍化防控和土地资源高效利用的重要基础。选择黄河三角洲垦利县,通过野外调查实测与室内化验分析获取土壤水盐含量数据,利用统计分析、GIS空间插值、实地观测与数据分析对比等方法,分析了研究区夏季土壤水盐状况及其微域变异规律。结果显示:研究区夏季土壤水盐含量总体较高,含盐量以中度盐渍化为主,随着土层深度的增加含盐量呈上升趋势,且各层土壤含盐量呈显著正相关性;含盐量较高的地区主要分布在该区东北部和中东部,含盐量较低的地区主要分布在西南部和中部;土壤含盐量从大到小的植被类型依次为光板地→碱蓬→高粱→芦苇→茅草→水稻→棉花→玉米;土壤盐分微域变化特征明显,含盐量受距路边远近、不同耕作措施、地形部位、植被群落等因素影响较大,表现出微域规律性和复杂性。该研究基本摸清了研究区夏季时相的土壤水盐状况及其微域特征,为黄河三角洲农作物栽培管理及土壤资源可持续利用提供了科学依据。     

氚水在模拟水稻－水－土壤生态系统中的行为

采用模拟污染物的同位素示踪技术研究HTO(流水)在水稻-水-土壤模拟生态系统中的迁移、消长行为,并应用三库室开系统模型和非线性回归方法确定了水稻、水和土壤分室的拟合方程．结果表明,田表水中的HTO不仅在系统各分室间转移和分配,而且迅速向系统外散逸;HTO中的流以自由水氚和结合态流形式存在于水稻中,以吸湿性水流和结晶水氚存在于土壤,其中自由水氚(或吸湿性水氚)的比活度大于结合态流(或结晶水氚);水稻植株和土壤中HTO比活度随时间增加至最大值后又趋于下降,而结合态氚则呈缓慢增加;水稻茎秆中的总氚比活度高于其它各部位,而后逐渐趋于动态平衡．对实验数据进行回归分析得：田表水、土壤和水稻植株中的总氚比活度分别为Cw(t)=32.19c^-0.0353t 99.94c^-0.330t、Cs(t)=20.42(e^-0.0353t-e^-0.330t)和Cr(t)=38.49c^-0.0353t-10.13e^-0.330t-28.36c^-2.5744t。方差分析结果表明,各回归方程较好地反映了HTO在水稻-水-土壤生态系统中的行为．     

Composition and spatial heterogeneity of submersed vegetation in a softwater lake in Wisconsin

Big Muskellunge Lake, a softwater lake (pH 7.5–8.0, alkalinity 0.36 meq/L) in northern Wisconsin, harbors a diverse (25 species) submersed macrophyte vegetation. The present submersed flora combines species generally thought distinct in their ecological affinities, and is very similar to that reported in 1935. The only differences are the apparent loss of three previously infrequent Potamogeton species, and the addition to the flora of two infrequent Potamogeton species and the now abundant Elodea canadensis. Dramatic differences in composition and pattern of the vegetation occurred between sites of contrasting exposure and sediment type. Substantial compositional variation, at scales ranging from tens of centimeters to tens of meters, occurred along transects of contiguous quadrats at uniform depth and exposure. Analyses of species sequences along line transects detected significant segregation of species that is most plausibly explained by biotic factors such as colonization, clonal growth, and competition. Heterogeneity at small scales of a few meters or less is common in Big Muskellunge Lake. Such pattern has been neglected in macrophyte ecology, in spite of its significance for neighbor relationships which may critically influence growth and reproduction of aquatic plants.     

京东板栗主产区土壤氮磷钾的空间变异

采用经典统计学和地统计学相结合的方法,对京东板栗主产区迁西县土壤氮、磷、钾的空间变异进行了分析.结果表明：迁西县土壤全量氮、磷、钾和速效氮、钾的含量普遍较低,但表层土壤速效磷含量较高;氮、磷、钾的空间分布均表现为中等变异,且以磷的变异最大.表层土壤全氮和碱解氮的分布符合高斯模型,其空间变异主要由结构性因素决定;全钾和速效钾的分布分别符合球状模型和高斯模型,前者空间变异受结构性因素和随机性因素的共同影响,空间相关性为中等;后者主要受结构性因素的影响,空间相关性强烈.氮、钾在全县范围内的空间分布特征相似,高值区均出现在县域南部和西北部,而中部和东北部的含量较低.全磷的高值区主要分布在该县北部,速效磷高值区则分布在县区南部.氮、钾全量和有效态含量之间存在极显著正相关关系,但全磷和速效磷含量的相关性不显著.     

梨小食心虫化学感受蛋白cDNA的克隆、序列分析及原核表达

为了研究梨小食心虫Grapholita molesta化学感受蛋白（chemosensory proteins, CSPs）在化学感受系统中的作用, 本研究利用RT-PCR和RACE技术克隆到一条梨小食心虫化学感受蛋白的全长cDNA序列, 命名为GmolCSP （GenBank 登录号： JQ821389）。序列分析表明, GmolCSP开放阅读框序列为384 bp, 编码127个氨基酸残基, 预测N末端含有18个氨基酸组成的信号肽序列, 其成熟蛋白的预测分子量为12.80 kD, 等电点为8.33。该基因编码的氨基酸序列与其他鳞翅目昆虫化学感受蛋白的氨基酸序列具有较高同源性。RT-PCR结果显示, GmolCSP在梨小食心虫成虫触角、 去触角的头、 胸、 腹、 足和翅中都有表达。将GmolCSP重组到表达载体pET-32a中, 转入大肠杆菌Escherichia coli BL21（DE3）进行表达。SDS-PAGE和Western 印迹检测结果显示, 梨小食心虫化学感受蛋白基因在大肠杆菌中成功地表达出一个分子量约为29 kD的融合蛋白, 与预测的融合蛋白分子量大小一致。本研究结果为进一步研究该蛋白的分子结构和功能奠定了良好基础。     

Quantifying the evidence for ecological synergies

There is increasing concern that multiple drivers of ecological change will interact synergistically to accelerate biodiversity loss. However, the prevalence and magnitude of these interactions remain one of the largest uncertainties in projections of future ecological change. We address this uncertainty by performing a meta-analysis of 112 published factorial experiments that evaluated the impacts of multiple stressors on animal mortality in freshwater, marine and terrestrial communities. We found that, on average, mortalities from the combined action of two stressors were not synergistic and this result was consistent across studies investigating different stressors, study organisms and life-history stages. Furthermore, only one-third of relevant experiments displayed truly synergistic effects, which does not support the prevailing ecological paradigm that synergies are rampant. However, in more than three-quarters of relevant experiments, the outcome of multiple stressor interactions was non-additive (i.e. synergies or antagonisms), suggesting that ecological surprises may be more common than simple additive effects.