华北平原夏玉米潜在产量时空演变及其对气候变化的响应

华北平原是我国的粮食主产区,为探讨气候变化可能对该地区粮食产量产生的影响,本文以中国科学院青藏高原研究所的中国区域地面气象要素数据集为基础,对作物生长模型WOFOST(WOrld FOod STudy)进行面域化,模拟华北平原1979—2015年夏玉米的生长情况;利用一元线性回归、经验正交分解(EOF)分析了华北平原夏玉米潜在产量的时空变化,利用逐个栅格相关性分析、奇异值分解(SVD)分析了华北平原不同区域夏玉米潜在产量与全生育期、吐丝前和吐丝后平均温度及日均太阳总辐射的相关性。结果表明,研究区夏玉米潜在产量大致呈现从南向北逐渐升高的特点,大部分地区夏玉米潜在产量为7 000~9 000 kg?hm~(-2);研究区西北部夏玉米潜在产量波动较大,波动较小的地区在北京南部、天津以及河北中部一带,标准差在500 kg?hm~(-2)以下;研究区西北部及河北唐山北部以及山东半岛东部夏玉米潜在产量呈上升趋势,这些地区的夏玉米潜在产量上升幅度大部分在200~600 kg?hm~(-2)?(10a)~(-1);研究区的其余大部分地区夏玉米潜在产量呈下降趋势,其中河北中南部、天津、鲁西北以及皖北的部分区域下降较明显,变化幅度在-250 kg?hm~(-2)?(10a)~(-1)左右。河北西部和东北部、北京西北部以及山东中部和东部等地区的夏玉米潜在产量与气温具有较显著的相关关系,相关系数在0.9以上,这些地区的夏玉米潜在产量在过去37年呈上升趋势,表明这些地区夏玉米潜在产量的增加可能是由气温上升导致的。北京东部和南部、天津、河北中南部及秦皇岛唐山南部、山东、河南东部、皖北和苏北等地区的夏玉米潜在产量与太阳总辐射具有较好的相关关系,相关系数在0.8左右,其中,吐丝后通过显著性检验的区域较吐丝前大,相关系数也较吐丝前大,该区域大部分地区夏玉米潜在产量呈下降趋势,可能是由该区域太阳总辐射下降导致的,且总辐射的下降主要对夏玉米的生殖生长阶段构成影响。总的来说,研究区夏玉米潜在产量上升的区域与温度的上升有关,温度的变化是这些地区夏玉米潜在产量变化的主导因子;研究区夏玉米潜在产量下降的区域与太阳总辐射的下降有关,太阳总辐射的变化是这些地区夏玉米潜在产量变化的主导因子。因此,气候变化背景下针对华北平原不同地区制定不同的合理应对措施显得尤为重要。     

基于PPC模型与RI指数法的茶产地土壤重金属污染评价

以某喀斯特山区茶产地表层土壤为研究对象,依托GIS空间分析技术,采用投影寻踪聚类(PPC)模型和潜在生态风险指数(RI)法两种较新的评价方法对土壤重金属污染进行综合评价。投影寻踪聚类模型将236个土壤样本中的Hg、As、Cd、Pb、Cr含量指标作为多维投影参数寻求其最优投影方向,由投影指标函数得出土壤重金属污染投影值来反映重金属含量的特征,建立投影寻踪聚类模型,从而得出研究区土壤重金属污染实际现况,结合潜在生态风险指数法,进一步对研究区土壤重金属污染风险程度和演变趋势进行预测。结果表明:(1)在指标投影方向上Hg和As对研究区土壤污染影响最大,Cd对土壤污染影响最小;(2)根据PPC评价标准,研究区土壤环境质量状况良好,无污染的样点区域达到96.61%,清洁占总样点数的30.08%,尚清洁占总样点数的66.53%;(3)在潜在生态风险上存在低度、中度,分别占采样点的89.41%和10.59%,风险程度较低,但有向中度演变的趋势;(4)在污染情况上,清洁和尚清洁的空间分布广阔,轻度污染进行内插后空间分布不明显。本文研究结果有利于综合评价该地的土壤环境质量状况,在实践中将为喀斯特山区的土壤资源的管理和茶叶种植区的合理布局起到参考作用。     

气候变化对黑龙江省自然植被气候生产潜力的影响

为了解1970—2014年黑龙江省自然植被气候生产潜力的分布规律和变化趋势及其对气候变化的响应,利用黑龙江省80个气象站观测数据,结合Miami模型,通过小波分析和EOF分析等方法,对黑龙江省自然植被气候生产潜力的变化特征进行分析.结果表明:1970年以来,气温、降水、蒸散和标准气候生产潜力呈增加趋势,2000—201...     

试论高校图书馆中的危机管理

论述了地方高校图书馆实行危机管理的意义及实施措施。     

甜高粱作为优质饲草在我国草牧业发展中的潜力分析

随着我国节粮型畜牧业结构调整和不断发展,以粮换畜逐渐转变成以草换畜,因此对优质粗饲料的需求日渐增加.甜高粱作为一种新兴的高能非粮作物,因其生物产量高、营养丰富、光合效率高、抗逆能力强等特性,成为我国干旱、半干旱和高盐碱地区畜牧业的优质饲草来源.动物养殖中使用甜高粱,不仅可以缓解畜多草少的压力,还可以充分利用盐碱地和其他...     

浅析广州市行道树引起的交通安全隐患及防范措施

由于多种原因,时有行道树倒伏压车、影响交通或折枝伤人等事故的发生。该文从茂密树冠造成视觉盲区,滥用大苗,树穴与花基设计不周;管理养护中修剪不当,浇灌不合理,病虫害防治不力;该文还从树穴土壤质量差或地下水位高,地面铺装不透水不透气,人为损坏严重及树体衰老等多个方面,探讨了行道树引起交通安全隐患的原因。并从技术和管理两个方面提出了相应的防范措施：在视距三角形范围内采用通透式配置,慎用大树,改地适树;采用透水透气铺装,加强管理和养护,加强衰老树木的管养和复壮;加强行道树的巡查处理,降低人为损坏的影响等。     

子产理政对现代社会灾疫救治与公共危机应对的启示

灾疫属于非常危急的公共事件。灾疫救治是一种特殊状况下的社会治理。春秋时期著名政治家子产的理政思想对现代社会公共危机应对中出现的问题仍具有镜鉴意义。子产"学而后入政,未闻以政学"的理政观念启发人们,灾疫防治机制既要事先规划和构想,更要在灾情发生前进行必要的"实操演练",真正做到"有备无患"。灾疫救治要打破常规思维,"因时制宜,因势而变",危急时要有子产"坏晋馆垣"那样的果断举措。子产"闻忠善以损怨,不作威以防怨"的舆情应对之道说明强化"显政"是引导舆情的关键。在灾疫救治中,行政官员的责任担当意识和执行能力至关重要。危难之际,"苟利社稷,死生以之"的胆识和魄力是应对危机的关键。     

Crisis mediated new discoveries,claims and encounters: Changing use and perception of residential greenery in multistory housing in Berlin,Germany

With the stay at home orders during the pandemic, the often semi-public green spaces of the residential environment, usually created during the building of the houses, became our literal spheres of experience. In our study, we explored use and perceptions of local greenery by residents after sixteen months of the COVID-19 crisis, using face to face questionnaires in eight socially disadvantaged neighborhoods of Berlin, all exposed to high loads of environmental stressors and belonging to four relevant building types of Central European cities. Residential greenery was highly appreciated by residents during COVID-19, and fostered a more active appropriation such as meeting neighbors to reduce the sense of loneliness, doing sports and co-creating refugia in challenging times (e.g. greened balconies). Having children or doing home office/schooling encouraged people to use the green in front of the door in more active ways, such as gardening or even during winter. A minor proportion of respondents reduced contacts mainly due to fear of infections, underlining the need to overcome those distances and to re-connect neighbors and living inside and outside the houses in a post-pandemic city. Our data prove the functionality of residential greenery as ‘social tissue’ or ‘social hubs’ of neighborhoods by fostering attachment to place and people and, at the same time, as healthy environment for practices such as enjoying nature and physical activity in fresh air.     

组合压气机中尾迹与势流同频/异频干涉的叠加特性

为揭示多级压气机中上下游叶轮对中间叶片叠加气动影响特性,阐述不同叠加干涉情况下下游叶轮进气角度变化,采用数值方法模拟了一级轴流和一级离心组成的组合压气机非定常流场。详细讨论了上游动叶尾迹和下游动叶势流对中间导流叶栅段气流非定常流动的异频和同频叠加干涉特性,依据计算结果,直观地展示了静叶通道中两种干涉间相互激励和抑制作用的位置和时间,与数学公式的推导结果相互印证。研究结果表明:当上下游动叶对中间静叶段异频干涉时,干涉的激励、抑制区域的轴向位置随时间发生变化；当上下游动叶对中间静叶干涉频率相同时,干涉的相互激励、抑制区域的轴向位置不随时间发生变化,但干涉的激励、抑制区域的轴向位置受时序位置影响。另外,上游动叶尾迹与下游离心叶轮势流的不同叠加情况,决定着下游离心叶轮进口相对气流角的大小及波动幅值。      

Forest conversion adversely affects native Macrobrachium shrimp assemblages in tropical Malaysian streams

1. Commodity-driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species.
2. Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans.
3. This study evaluated the impact of forest conversion and land-use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia. Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small-scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings.
4. Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non-native species abundance. Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non-native species abundance, with non-native species abundance increasing along the human disturbance gradient.
5. These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non-native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment-based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.