Fixed location hydroacoustic monitoring of fish populations in the tidal River Hull, north-east England, in relation to water quality

Abstract  Fixed location hydroacoustic fish monitoring was carried out at a series of sites in the tidal River Hull, north-east England, in July 1996 during periods of moderate freshwater flows and spring tides. This was followed by a corresponding series during a period of lower freshwater flows and spring tides in autumn 1996. The surveys indicated substantial numbers of fish living upstream and downstream of a depleted oxygen zone which exists in the tidal Hull. Conditions in this zone of poor water quality deteriorated further during low flow periods due to reduced dilution of effluents. Fish populations moved with the tide apparently in response to gradients of dissolved oxygen and salinity. Under conditions of low freshwater flow and high tides, gradients of salinity and oxygen were steeper and fish responses appeared more marked: at higher salinities, the response to increasing salinity overrode the response to decreasing oxygen availability.     

不同基因型水稻镉吸收差异及镉对水稻的影响研究进展

研究镉对水稻污染的生理生物学的作用机制,筛选富镉或低吸镉的水稻基因型品种对保护生态环境和生产绿色食品都具有重要的理论意义和实用价值。综述了稻田镉污染的现状、危害,水稻镉吸收积累差异以及镉对水稻生长发育的影响等方面的研究成果,并提出了今后的研究方向。     

Multi-Temporal Detection of Rice Phenological Stages Using Canopy Spectrum

Information on rice phenology is essential for yield estimation and crop management. To test the ability of remote sensing in detecting multiple phenological stages, paddy rice canopy spectrum was measured by a hand-held radiometer. Normalized difference vegetation index(NDVI) was calculated from spectrum, and the slope of NDVI was obtained as its difference. We evaluated the response of NDVI and its slope to rice growth with a comparison of two late-season rice cultivars. The results showed that NDVI and its slope curves had distinct variation corresponding to rice development and they could be used as cultivar-independent phenological indicators. The dates of flooding and transplanting, tillering, panicle development, heading and flowering, maturity, harvest stages, and even field management practices, could be deduced from these indicators. ‘NDVI ≤ 0' could be used as a single threshold for the detection of flooding and transplanting. The largest spike in the curve of the NDVI slope indicated the duration of tillering stage. The next spike corresponded to panicle development. The heading and flowering stage was characterized by the maximum NDVI and the change of NDVI slope from positive to negative. At the maturity stage, NDVI decreased continuously, and its slope fluctuated just below zero. When rice grains were completely mature and ready for harvest, NDVI decline was accelerated. At harvest, NDVI slope reached its minimum value. The distinction between heading and maturity stages was obscure, most likely due to NDVI saturation at high biomass. The study might provide references for paddy rice phenology determination through remote sensing images.     

基于MGWR的渭河流域TRMM降水产品空间降尺度分析

高分辨率降水数据有助于刻画降水的时空分异特性,对流域水文、气象和生态等过程的精准模拟具有重要作用,因此对低分辨率降水产品开展空间降尺度,提高其分辨率十分必要。鉴于此,本文在充分考虑热带降雨测量卫星（Tropical Rainfall Measuring Mission,TRMM）降水产品在渭河流域适用性的基础上,引入归一化差分植被指数（Normalized Difference Vegetation Index,NDVI）、数字高程模型（Digital Elevation Model,DEM）、坡度、坡向和经纬度等地理环境因子,构建了多尺度地理加权回归（Multi-scale Geographically Weighted Regression,MGWR）模型用以分析不同因子对渭河流域降水空间格局影响的尺度差异;进一步提出了一种针对TRMM降水产品的空间降尺度方法,并透过精度评价验证了降尺度结果的可靠性。结果表明：1）TRMM降水产品数据相较于站点实测数据存在一定精度误差,年尺度上R2=0.807,BIAS=2.909%,RMSE=83.477 mm,表现较好;季尺度上秋季R2最高,为0.847,夏季RMSE最大,为62.393 mm,四季的BIAS均较低;月尺度R2为0.456～0.815,BIAS介于±0%～8%之间,多数月份为正值,RMSE值域范围为3.019～37.841 mm,精度较好;总体而言,TRMM降水产品数据在年、季和月尺度上均表现出良好的整体适用性。2）不同因子在干湿年份对降水空间分异格局的影响呈现出不同的尺度特征,其中湿润年的DEM、NDVI、坡向和经纬度对降水呈现局部影响,坡度影响具有全局性,而干旱年各因子均表现为局部影响。3）流域和站点尺度上,降尺度TRMM数据相较于降尺度前产品数据精度得到一定改善,其中流域尺度上,R2整体提升3%,RMSE降低1mm;站点尺度上,各站点统计指标变化各异,但降尺度后统计指标整体优于降尺度前,并且由于时间尺度上的误差累积,站点年尺度数据精度相比月尺度数据稍差（R2由0.8～0.91变为0.4～0.95,RMSE从11～17变为32～150）。4）降尺度TRMM数据相比于降尺度前产品数据,空间分布更细腻,细节特征表现更好,且在年、月时间尺度上均具有较高的精度,可为渭河流域资料短缺地区的水文设计提供数据支撑。     

低成本小型无人机遥感定位病死木方法

松材线虫病造成了我国大量的松树死亡,带来了严重的经济损失.及时发现并定位松材线虫感染的病死木,采取焚烧、就地砍伐等措施是有效阻止疫情扩散的可行方法.笔者利用低成本小型无人机采集疫情地区的高空间分辨率影像,并经摄影测量软件LPS正射处理后,导入到美国GeoLink软件中,实现病死木位置信息的采集.经地面差分GPS测量验证,水平位置偏差在0.24～2.82 m之间,精度均方根误差为1.565 m.该方法比传统病虫害监测实施效率高,系统维护和使用成本较低,可为疫情区域判断疑似病死木位置提供定位技术支持.     

热棒位置与热棒效果关系的研究

热棒主要是在冬季将地下的热通过热棒导向大气,使冻土范围和冻土上限都变大,这样使冻土路基更加稳定.由于热棒只能影响一定的区域,所以热棒的埋设位置对热棒保护路基土有很大的影响,本文通过MRDT600温度监测系统对埋设直插型热棒的试验路路基与埋设了斜插型热棒的试验路路基进行温度监测.通过对监测的温度数据进行分析和对比,总结直棒、斜棒与L型热棒在保护冻土路基方面的优缺点.     

一种土壤重金属污染源位置的分析方法

对某城市表层土壤中As、Cd、Cr、Cu、Hg、Ni、Pb、Zn等8种重金属元素的含量进行了采样分析,采用域法识别特异值进行数据处理。采用坐标平移法,修正高斯扩散方程,利用MATLAB软件进行拟合,得到了这8种重金属污染源的空间位置坐标。     

锦州地区温度差异特点及影响因素分析

通过统计锦州地区2004—2013年5个地面大气观测站的观测资料,分析锦州地区5个地面观测站日最高温度和日最低温度差异特点和日最高、最低温度升降温的极端变化情况。结果表明:锦州地区最高温度差异不大,为0~2℃,季节变化不明显,最低温度差异较大,有明显的季节变化;冬季最大,春秋次之,夏季最小;极端升降温日幅度变化相似,在冬季和春秋季较大,夏季较小。     

峨山彝语地名的文化语言学解读

峨山自古就是彝族聚居的地方,传承了众多的彝语地名,其命名与彝族所处自然环境、社会生活和历史文化密切相关,体现出明显的区域特征和民族特征,从中可以看到峨山彝族社会历史风貌、语言文化和多民族文化的交流与融合.     

膜下滴灌棉花叶温变化规律及其与气象因素关系的研究

通过对新疆石河子市148团膜下滴灌棉花灌区实验地各行棉花叶片温度及土壤含水率的测定、各行棉花发育情况的调查和当地气象资料的收集,利用Origin7.5的函数拟合功能,分析了棉花叶温与当地气象资料的关系。并且分析了棉花叶温与土壤含水率和棉花生长发育情况的关系,以便讨论在本研究种植模式下如何提高棉花产量。结果表明：棉花叶温与气象因素的相关性从高到低排列顺序依次为气温、空气饱和水汽压差、空气相对湿度、日照时数、风速。其中,棉花叶温与气温的相关系数为0.91327,其拟合方程可以用来预测棉花叶片温度。另外,棉花叶片的温度会随土壤含水率的增高而降低,在本研究“一膜两管,一管三行”,“66+10”的种植模式下,棉花叶片温度较低的那行生长发育情况较好,且产量也较高。建议在本研究种植模式下将中行棉花适当向滴灌管附近移动,以此来提高棉花产量。