Spartina alterniflora invasion affects methane emissions in the Yangtze River estuary

Journal of Soils and Sediments - Wetlands are the largest natural sources of atmospheric methane (CH4) and are often susceptible to plant invasion and hydrological fluctuations. However, the effect...     

Effects of drought stress on the photosynthetic physiological parameters of Populus 3 euramericana ‘‘Neva'

Populus 9 euramericana ‘‘Neva' is the main poplar species in China, where drought stress is becoming extremely urgent. We carried out this research to study the effects of drought stress on the photosynthesis of Populus 9 euramericana ‘‘Neva'. Drought stress was induced by 58–62%(light), 48–52%(moderate), and 38–42%(severe) relative soil moisture content(RSMC). The effects of drought stress on photosynthetic rate, chlorophyll fluorescence parameters, and other related physiological parameters were investigated during treatment. Net photosynthetic rate(PN), and stomatal conductance decreased significantly and intercellular CO_2 concentration initially increased and then declined, whereas the stomatal limitation factors showed opposite trends in the light under moderate drought stress. Photosystem II(PSII) maximum photochemical efficiency, actual photochemical efficiency,and photochemical quenching decreased gradually under drought stress, whereas nonphotochemical quenching initially increased and then declined. Superoxide dismutase,peroxidase, and catalase activities initially increased and then decreased as RSMC was reduced, whereas malondialdehyde(MDA) content and relative electric conductivity(REC) increased gradually. These results suggest that stomatal factors accounted for the decline in PNunder light and moderate drought stress, whereas leaf PNdecreased mainly due to non-stomatal factors under severe drought stress. PSII was damaged; thus, photosynthetic electron transfer was restricted, indicating that heat dissipation is important for the light protection mechanism of plants.Antioxidant enzymes increased at the beginning of treatment, and the increased MDA and REC led to cell membrane damage. These results suggest that poplar seedlings stabilized their photosynthetic apparatus by reducing the light trapping ability under light and moderate drought stress conditions. This helped dissipate heat and enhance antioxidant enzyme activity. Stomatal factors accounted for the decline in P_N, whereas damage to PSII and antioxidant enzymes under severe drought stress suggested that the decline in P_N was caused by non-stomatal restrictive factors.     

陕北榆林地区河川径流变异类型的识别方法

【目的】探索陕北榆林地区河川径流变异类型的识别方法,为进一步了解黄土高原河川径流变化组成及其演变规律与发展机制提供参考。【方法】以陕西榆林22个水文测站的实测年径流序列为研究对象,将经验模态分解(EMD)法与二阶导数法、STARS法、迭代累积平方和(ICSS)法相结合,通过EMD分离径流序列中波动性成分(高频分量)与趋势性成分(低频分量),应用二阶导数法、STARS法和ICSS法对径流序列中趋势变异、均值变异和方差变异进行检验,有效识别不同水文站径流序列的复合变异特征与类型。【结果】陕北榆林地区22个水文站点径流序列总体呈现衰减趋势,年径流衰减速率空间差异较大(-0.06%～-54.73%),对榆林地区的区域用水安全造成了严重的威胁。年径流序列区域变异类型复杂多变,覆盖了未变异,趋势变异,均值变异,方差变异,趋势与均值两重变异,趋势与方差两重变异,均值与方差两重变异,趋势、均值、方差三重变异8种类型。其中,先升后降型和先降后升型的趋势变异主要集中在1960和2000年前后,向下跳跃均值变异主要发生于1970年左右,方差变异则多发于20世纪六七十年代。【结论】陕北榆林地区不同流域的径流时间序列变异程度有差异,且类型复杂多变,趋势变异、均值变异、方差变异基本呈现均势,且复合变异态势显著。在气候变化、下垫面条件变化以及直接人类活动的综合影响下,榆林地区的河川径流变化正在日趋复杂化。     

六个强筋小麦品种不同出粉点面粉和面片的色泽及其褐变特点

为研究不同出粉点面粉面条色泽品质的差异,测定了6个强筋小麦品种通过布勒实验磨制粉获得的不同出粉点面粉的品质特性与面片色泽及褐变情况。结果表明,3道心磨和3道皮磨的面粉和面片色泽的L^*值均随出粉点后移呈下降趋势,而a^*值和b^*值则呈上升趋势;在面片放置过程中,3道心磨和3道皮磨面粉所加工面片色泽亮度的下降值、偏红度的上升值和偏黄度的上升值均随出粉点后移呈加速趋势。面片色泽与蛋白质含量、灰分含量和面粉L^*值关系密切。鲜面片放置24 h后色泽亮度的下降值与面粉粗蛋白质含量和灰分含量均呈极显著正相关,相关系数分别为0.444和0.758,而与面粉L^*值呈极显著负相关,相关系数为-0.681;色泽偏红度的上升值与面粉灰分和破损淀粉含量均呈极显著正相关,相关系数分别为0.834和0.760;色泽偏黄度的上升值与所有指标的相关均不显著。3心粉的色泽差,其所加工的面片色泽也较差,且色泽不稳定,在面片放置过程中色泽的亮度、偏红度和偏黄度保持性最差,褐变程度严重;1心粉的色泽好,其所加工的面色泽好,并在面片放置过程中,色泽的亮度和偏红度保持性较好,而色泽的偏黄度不如1皮粉和2皮粉的稳定。     

日本花柏心材和边材精油的组分

芳香植物日本花柏天然耐久,富含精油。日本花柏心材和边材的精油组分气相色谱-质谱分析结果表明其心材与边材精油组分均主要由醇类和萜烯类化合物组成;心材精油主要挥发性组分为δ-杜松醇(40.64%)和β-荜澄茄油烯(12.67%);边材精油主要挥发性组分为α-杜松醇(29.98%)和α-依兰油烯(10.18%)。日本花柏心材和边材精油的挥发性组分不同,日本花柏心材精油中最高含量的δ-杜松醇为木材抗白蚁活性成分,萜烯类化合物具有化感作用。日本花柏心材精油在环境友好型农药开发上具有潜在价值。     

鸽新城疫油乳剂灭活疫苗的研制

鸽新城疫是流行于鸽群的一种高度接触性急性传染病,对养鸽业威胁巨大,为有效防治鸽新城疫的发生,利用鸡新城疫病毒和分离到的鸽1型副黏病毒JB株研制了鸽新城疫油乳剂灭活疫苗,并对该疫苗的安全性、免疫效力、免疫期及保存期等进行了试验研究。结果表明,该疫苗使用安全,无不良反应;疫苗注射后1周就可检测到HI抗体,4周后达到高峰,HI抗体可持续6个月;免疫后21 d、60 d、120 d、180 d,分别用F48E9株和JB株2种病毒攻毒,其保护率均在80%以上,对照(未免疫)组鸽全部死亡;在2~8℃条件下保存12个月后,性能稳定,免疫肉鸽仍有较高的免疫抗体滴度。     

马来酸酐接枝乙烯与辛烯共聚物对木粉/聚丙烯复合材料力学性能的影响

通过引入马来酸酐接枝乙烯与辛烯共聚物(MA-POE)提高了木粉/聚丙烯(WF/PP)复合材料的韧性,并通过动弹性模量分析探讨了MA-POE对WF/PP复合材料低温力学性能的影响。研究结果表明,加入MA-POE后复合材料冲击强度在-20℃和20℃条件下比未添加MA-POE的空白样分别提高了60%和68%;在常温下弯曲强度从41.70MPa升高到50.86MPa,提高了22%;MA-POE能够有效地降低WF/PP复合材料的弹性模量、储能模量和损耗模量,使三者都向低温偏移;采用MA-POE先与PP熔融共混后再与木粉混合的工艺可以进一步提高复合材的强度。动弹性模量分析证明添加MA-POE能够改善WF/PP复合材料的低温韧性。通过扫描电子显微镜也进一步印证了两相结合得到了改善。     

内蒙古东部湿地植被演替的初步研究

湿地植被是湿地生态系统的基本组分,其演替过程受地表水分、水深浅、水流速度、流向、微地形等诸多因素的影响,伴随着这些因素影响所引起的微生境的变化,湿地植被的类型也发生着相应的变化和迁移,从而沿河湖岸形成一定的梯度变化规律,呈现出一定的空间分布序列,而这一序列恰恰在某种程度上反映出了一些湿地类型的湿地植被的演替过程。因此,本文试图以内蒙古东部区湿地植被现状和类型的调查结果为例描述其湿地植被在不同因素作用下的演替序列。     

中早熟番茄新品种“黄山1号”的选育及 抗青枯病鉴定

番茄青枯病是一个世界性的严重病害,已成为番茄生产上的重要障碍.种植抗病品种是防治植物病害最经济有效的方法,但番茄在抗青枯病品种培育中存在着抗病性与品质和产量相矛盾的问题.对此,该研究采用杂交和回交相结合,并自回交后代参与病理程序的选育方法,获得了具有较高的田间抗病性"黄山1号"番茄新品种.人工接种表明,黄山1号的平均发病率为5.5%,极显著低于对照感病品种强丰的平均发病率(94.6%),且产量和生食风味均优于丰产亲本"强丰".     

Response of fungal and plant communities to management-induced overstorey changes in montane forests of the Western Carpathians

The effect of forest management on biodiversity is a crucial issue for sustainable forestry and nature conservation. However, the ways in which management affects macrofungal and plant communities and diversity of mountain temperate forests still remain poorly understood. We performed a random sampling stratified by stand age and stand type on the sites of temperate montane fir–beech forests. Diversity of macrofungi and the vascular plant understorey in beech- and spruce-dominated managed stands was investigated and compared to primeval forests located in the Po?ana Biosphere Reserve, Western Carpathians. Both the vascular plant and the macrofungal communities were altered by management, and the response of the macrofungal species (especially wood-inhabiting fungi) was more pronounced in terms of species composition change. Species turnover evaluation seems to be an important tool of forest natural status assessment, because alpha diversity did not change as much as species composition. Certain species of Carpathian primeval forests were confirmed as good indicators for natural forest change; others were proposed. Species pool and mean number of species per plot were the highest in unmanaged fir–beech forests, and species diversity significantly decreased in spruce plantations. The number of species decreased significantly due to the change of canopy tree species composition only in the macrofungal communities. As an outcome for forest management, we recommend keeping mixed forests involving all natural tree species and providing at least a minimal amount of dead wood necessary for wood-inhabiting organisms and leaving some area of unmanaged natural forests within complexes of managed stands.