不同土地利用类型对城市地表温度的影响——以广东东莞为例

利用Landsat TM6热红外遥感数据、土地利用专题图件、气象观测资料反演了快速城市化的典型地区东莞市的城市地表温度。构建了三个热效应评价指数:热效应贡献度指数、热像元权重指数和区域热像元权重指数,来定量分析不同土地利用类型对城市地表温度的贡献度,发现城乡工矿居民用地、林地和耕地的热效应贡献度较大,水域和草地的热效应贡献度较小,未利用地对区域热环境的贡献最小。此外,研究表明,随着平均温度的升高,东莞市水面和陆面1988~1998年的温度反差明显增大。     

Use of multimetric indices to classify estuaries with different hydromorphological characteristics and different levels of human pressure

The assessment of estuaries based on benthic communities is widely used to determine impacts caused by human pressure and is one of the required tools for the implementation of the European Water Framework Directive (WFD). Our study compared multimetric approaches (B-IBI and TICOR) to assess the benthic condition of three Portuguese estuaries (Mondego, Tejo, and Mira rivers) with different levels of natural and human induced stress. Benthic community condition was classified into quality status categories of the WFD and compared for consistency with a priori status categories based upon physical-chemical criteria. Both multimetric indices discriminated equally well between locations classified above or below the good status category but were unable to provide good separation between other quality classes (high/good, moderate, poor/bad). Metrics included in these indices are greatly affected by natural stress and we recommend the development of habitat-specific thresholds to increase the discriminatory ability of any benthic condition index.     

Efficacy of adapted estuarine fish-based multimetric indices as tools for evaluating ecological status of the marine environment

The assessment of ecological status of marine fish communities required by the marine strategy framework directive (MSFD) emphasises the need for fish-based ecological indices in marine waters. In this study we adapt five estuarine multimetric indices to the marine environment and apply them in three types of substrates, analysing the metrics responsible for the obtained patterns of ecological status. The results show inefficiency of the community degradation index (CDI) and the biological health index (BHI) in ecological status assessment and disagreement between the estuarine biotic integrity index (EBI), the estuarine fish community index (EFCI) and the transitional fish classification index (TFCI). Analysis of individual metrics suggests lack of representativeness and consideration for the particularities of each substrate’s typical fish communities. None of the tested indices were efficient on the marine environment, urging the need for new marine indices that account for differences between types of substrate and depth.     

新的锚固体抗拔力测试系统及应用

针对我国锚固体抗拔力现场检测方法中的不足,借助压力传感器、位移传感器、数据采集盒等电子元件,建立了一个新的抗拔力测试系统。该测试系统首先利用数据采集盒将传感器传递过来的反映压力和变形的电流信号转换为数字信号,再由相关程序对数据进行降噪处理并绘制测试曲线。系统实现了测试过程中数据的自动采集和成图,有助于测试人员及时了解锚固体的受力状况,避免了锚固体张拉破坏。以惠莞高速公路ZK26+231～ZK26+520压力分散型锚索抗拔力检测情况为例,验证了该系统的实用性和可靠性。     

石漠化土地分级指征及其遥感影像特征分析——以粤北岩溶山区为例

建立准确的石漠化土地分级指征及其卫星遥感影像特征是提高石漠化土地监测与评价的基础和关键。以生态基准面概念为理论依据,在综合性、主导性、可操作性原则指导下,选取基岩、植被、土壤、土地利用等指标,建立了粤北山区石漠化土地分级指征,并提出了各级石漠化土地的解译标志。结果表明：选取的分级指征及解译标志能够有效地揭示粤北石漠化土地的现状。     

鳗鲡(Anguilla japonica)性腺发育和饥饿胁迫下生物学指标及体内蛋白质与氨基酸含量变化

自然条件下, 鳗鲡(Anguilla japonica)自降河入海至性腺发育成熟需洄游数千公里、耗时半 年以上, 且整个过程中不摄食。本文以降海洄游、人工促熟和长期饥饿(20 个月)三种状态下的鳗鲡 为材料, 研究其在性腺发育和饥饿胁迫时的主要生物学指标(包括肥满度、肝体比、脏体比、性腺指 数、含肉率)以及肌肉、肝脏和性腺中的粗蛋白与氨基酸含量的变化情况, 以探讨鳗鲡性腺发育和饥 饿胁迫下的营养物质来源与变化。结果发现: 人工促熟鳗鲡的肝体比、脏体比和性腺指数显著高于 降海洄游鳗鲡(P<0.05), 而含肉率、肝脏和卵巢内的粗蛋白含量、氨基酸总量、必需氨基酸总量以及 非必需氨基酸总量均显著低于降海洄游鳗鲡的含量(P<0.05); 长期饥饿鳗鲡的肥满度、肝体比、含肉 率、肌肉(鲜样)、肝脏内的粗蛋白、氨基酸总量、必需氨基酸总量以及必需氨基酸占氨基酸总量的 比值显著低于降海洄游鳗鲡(P<0.05).结果表明, 鳗鲡性腺发育所需要的营养物质主要来源于肌肉, 其性腺的发育依赖自身营养物质在体内的流动和转化, 肌肉中的必需氨基酸和非必需氨基酸均被利 用, 转化成性腺发育所需要的物质。     

Nonstationarity and clustering of flood characteristics and relations with the climate indices in the Poyang Lake basin,China

The magnitude, occurrence rate and occurrence timing of floods in the Poyang Lake basin were analysed. The flood series were acquired by annual and seasonal maximum flow (AMF) sampling and peaks-over-threshold (POT) sampling. Nonstationarity and uncertainty were analysed using kernel density estimation and the bootstrap resampling methods. Using the relationships between flood indices and climate indices, i.e. El Niño/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO), the potential causes of flooding were investigated. The results indicate that (1) the magnitudes of annual and seasonal AMF- and POT-based sampled floods generally exhibit an increasing tendency; (2) the highest occurrence rates of floods identified were during the 1990s, when the flood-affected crop area, flood-damaged crop area and crop failure area reached the highest levels; and (3) ENSO and IOD are the major climate indices that significantly correlate with the magnitude and frequency of floods of the following year.

EDITOR A. Castellarin ASSOCIATE EDITOR T. Kjeldsen     

Time-transgressive cryoplanation terrace development through nivation-driven scarp retreat

Cryoplanation terraces are elevated bedrock features resembling giant staircases, with alternating steep scarps and shallow sloping treads. These landscape-scale features have long been associated with periglacial environments, but the processes involved in their formation remain vaguely specified and contentious. The two leading hypotheses for the formation of cryoplanation terraces are centered on: (1) geologic structure; and (2) nivation-driven scarp retreat. The nivation-formation hypothesis invokes scarp retreat under erosion processes associated with late-lying snowbanks. To test whether cryoplanation terraces develop through scarp retreat, six relative weathering indices (fracture counts, Cailleux roundness, Cailleux flatness, Krumbein sphericity, rebound, and weathering rind thickness) were measured across well-developed terraces in unglaciated eastern Beringia (central and western Alaska) at Mt Fairplay, Eagle Summit, and Skookum Pass. Statistically significant differences in relative weathering indices detected through chi-square and multiple-comparison procedures indicate that material is less weathered closer to scarps, i.e. that these areas were more recently exposed than those distant from the scarp. Based on these findings, a refined model of time-transgressive cryoplanation terrace development through nivation-driven scarp retreat is proposed. This new qualitative model addresses the removal of weathered material from terrace treads down side slopes through piping and gravity-driven mass-wasting processes. © 2019 John Wiley & Sons, Ltd.     

老挝VIIRS活跃火的主要自然地理要素特征

利用美国国家航空航天局火灾信息资源管理系统（FIRMS）VIIRS V1活跃火、先进星载热发射和反射辐射仪全球数字高程模型（ASTER GDEM）、MODIS NDVI/LSWI与土地覆被数据产品（FROM-GLC）,基于GIS定量分析老挝2012—2017年从分省到国家不同空间尺度活跃火频次的动态变化,并重点分析2015厄尔尼诺年活跃火频次及其与海拔、坡度、植被-水分（NDVI ^*、LSWI）指数、土地覆被等主要自然地理要素的相关特征。结果表明：① 老挝活跃火频次呈先增后减的趋势,峰值在2015厄尔尼诺年,主要集中在上、中寮,其中琅勃拉邦、沙耶武里与沙湾拿吉三省居前三位,而万象市、塞公和赛宋本则居后三位。② 老挝2012—2017年活跃火发生频次与地形因素（海拔、坡度）的关系基本相同,活跃火集中在海拔1000 m以下、坡度小于30°的低山-丘陵区。其中,上寮活跃火集中分布在500~1000 m、10~30°的斜陡坡山地,中、下寮集中在500 m以下、2~20°的缓斜坡丘陵。③ 活跃火高度集中在旱季,以3月、4月最多,并集中分布在NDVI为0.4~0.8和LSWI为0.2~0.6的中高覆盖度植被区。④ 老挝活跃火主要发生在森林这一土地覆被类型中,且以上寮最为集中,而中寮多以农田、草地和灌丛活跃火为主。综上,基于自然地理要素的活跃火特征分析可以有效识别其发生类型,即老挝活跃火主要由刀耕火种农业所引起。     

结合Sentinel-2光谱与纹理信息的冬小麦作物茬覆盖度估算

作物茬覆盖度的估算对于探究农业耕作方式对周围环境的影响具有十分重要的意义。目前,基于多光谱影像的作物茬指数是作物茬覆盖度估算的常用方法。然而,在作物茬高覆盖区域,指数法容易出现“饱和”现象。已有研究结果表明结合影像的光谱与纹理信息有助于改善指数法的“饱和”问题。Sentinel-2作为一颗多光谱卫星,空间分辨率可达10 m,与Landsat OLI相比,具有更丰富的纹理信息。因此,探究Sentinel-2光谱与纹理信息相结合在作物茬覆盖度估算上的潜力具有重要意义。本文以山东省禹城市为研究区,分析了Sentinel-2各波段反射率、归一化差值指数以及不同窗口大小下灰度共生矩阵统计量等遥感因子与野外实测作物茬覆盖度的相关性,并利用最优子集法对遥感因子进行筛选,构建作物茬覆盖度的最优估算模型。同时,使用留一法交叉验证对模型进行评价。结果表明在单因子分析中,归一化差异耕作指数NDTI（Normalized Difference Residue Index）与作物茬覆盖度的相关性最好,相关系数达0.735。使用NDTI、5×5窗口下Sentinel-2 8A波段的相关性统计量以及12波段的方差统计量构建的多元方程是作物茬覆盖度估算的最优模型,相关系数为0.869,均方根误差为11%。与仅使用光谱信息的最优模型相比,相关系数提高了0.094,均方根误差下降了3.5%。可见,结合Sentinel-2的纹理信息有助于提高作物茬覆盖度的估算精度。