考虑气候时滞效应的河北山区 NDVI 演变归因

从植被类型、植被物候、气候因子时滞效应等方面研究 2001 年以来河北山区归一化植被指数（normalized difference?vegetation?index，NDVI）演变规律，并将气候因子时滞效应引入多元线性回归方法中，识别气候因子和人 类活动对河北山区 NDVI 演变的贡献。结果表明：2001—2022 年河北山区 NDVI 呈持续增长趋势，平均增速为 0.003?7/a，其中乔木林、灌木林和草地 3 种植被类型增速分别为 0.003?5/a、0.004?0/a 和 0.003?8/a；受气候变化影响， 河北山区植被生长季变长，生长季开始时间平均提前 9?d，而生长季结束时间仅提前 1?d；降水对植被 NDVI 的影响 主要发生在当月，而气温和潜在蒸散发对植被 NDVI 的影响存在 1 个月的滞后性，考虑气候因子的时滞效应后，气 候变化和人类活动对河北山区 NDVI 演变的贡献分别为 39% 和 61%，与不考虑气候因子时滞效应对比，多元线性 回归的决定系数由 0.80 提高到 0.87。人工水保措施是河北山区植被 NDVI 增长的主导因素，对快速改善山区生 态环境至关重要，同时 2001 年以来降水、气温等气候因素也有利于植被恢复，对植被条件较好的区域，应以自然 恢复为主，实现自然条件下的生态平衡。研究结果对优化山区水土保持工作方案，提高植被修复措施效果具有重要意义。     

陕西省NDVI时空变化及其对气候和人类活动的响应

利用2001—2020年MODIS NDVI数据，结合降水、气温等资料，采用Sen趋势分析、Mann-Kendall检验、Hurst指数、Pearson相关分析以及多元回归残差分析等方法，研究陕西省近20 a归一化植被指数NDVI的时空变化特征及未来变化趋势，探讨省内气候因素及人类活动对NDVI变化的影响以及NDVI对降水和气温响应的时滞效应。研究结果表明：(1)2001—2020年陕西省NDVI整体呈上升趋势，增长速率为0.004 7/a,NDVI在不同生态区有所差异，空间异质性明显；(2)陕西省NDVI变化的反持续性强于持续性，未来NDVI变化趋势以反持续改善(退化)为主；(3)陕西省降水和气温对NDVI变化均产生了正向影响，且NDVI与气温的相关性强于降水；(4)陕西省NDVI对降水的响应不存在明显的时滞效应，对气温响应的滞后期以0～1个月为主；(5)陕西省大部分地区NDVI残差呈增大趋势，人类活动对植被覆盖变化起到了显著促进作用。     

雅鲁藏布江流域近18年来植被变化及其对气候变化的响应

基于MODIS(moderate resolution image spectroradiometer) NDVI(normalized difference vegetation index)数据、DEM数据、1∶100万中国植被类型图,运用Mann-Kendall趋势及突变点检验法对2001—2018年雅鲁藏布江流域不同海拔梯度和植被类型的NDVI进行提取,分别在时间和空间尺度上分析其年际变化并探究流域NDVI变化与植被类型和气候因子的相关性。结果表明:全流域尺度、不同海拔梯度和不同植被类型近18年的NDVI年际变化均呈增长趋势且在2013年之后呈现明显的增长趋势。在空间尺度上,80%的流域近18年来NDVI呈增长趋势,植被状况得到较好的改善;流域NDVI在海拔小于等于3 500 m时主要受针叶林和阔叶林的影响,大于3 500 m且小于等于5 000 m主要受灌丛、草原及草甸的影响,大于5 000 m受高山植被和草甸影响较大;流域植被的NDVI受降水和气温的影响较大,其中温度的影响略强于降水;气候变化对流域植被的影响具有滞后效应,在该条件下流域植被的NDVI与气候因子的相关系数由大到小为草原、草甸、灌丛、高山植被、针叶林、其他植被、阔叶林。若一种植被类型受气温的影响大于降水,其对气温变化的响应也会更为敏感;反之,若该植被类型受降水的影响大于气温,则会对降水变化的响应更为敏感。     

滹沱河流域植被覆盖时空演变及其与 SPEI 的相关关系

选择2001-2015年MODIS NDVI(250m)及14个气象站点气温、降水数据,通过计算标准化降水蒸散指数(SPEI),探究滹沱河流域近15年植被覆盖时空演变特征,分别从月、季节、年等尺度探究植被覆盖与SPEI的相关关系。结果显示:(1)近15年滹沱河流域归一化植被指数(NDVI)呈显著增加趋势,增速为0.024/(10a)。(2)植被恢复以明显改善为主,覆盖范围占整个流域面积的51.58%,主要分布于流域中、上游。(3)滹沱河流域SPEI总体上呈波动上升趋势,干旱程度有所降低,流域中游变湿趋势最显著。(4)6月、7月是干旱条件对植被覆盖影响最显著的月份,其中,6月气温对NDVI的影响大于降水,而7月降水对NDVI的影响大于气温;夏季干旱程度对植被覆盖度的影响最为明显;NDVI年际变化与SPEI具有显著正相关关系,干旱对植被生长状态有较大影响。     

锡盟草地NDVI时空变化与气象因子关系

根据锡林郭勒盟1998—2007年NDVI数据集和18个气象站点的月气温和降水资料,分析了研究区草地植被NDVI值的年际、年内变化特征和不同季节NDVI值的变化特征,以及NDVI值与气温、降水变化的相关性。结果表明:研究区草地植被NDVI值具有相对稳定性,但整体呈下降趋势;春季、夏季和秋季草地植被NDVI值均处于下降过程中,下降趋势由小到大依次为秋季、春季、夏季;气温对植被覆盖状况的影响作用不显著,降水对植被覆盖状况的影响作用显著;植被的生长不仅受当月气象因子的影响,而且受上月气象因子的影响。     

渭河流域多时间尺度径流变化特征及主控因子

为研究变化环境下渭河流域多时间尺度径流变化特征及影响因素,基于渭河流域咸阳水文站1961—2015年实测径流量数据,分析不同时间尺度上径流的变化趋势,并选取多个气象要素与归一化植被指数（normalized difference vegetation index,NDVI）构建向量自回归（vector autoregression,VAR）模型,量化各影响因素对径流变化的贡献程度,探讨全年、汛期和非汛期径流变化主控因子的差异性。结果表明,1961—2015年渭河流域径流整体呈下降趋势,汛期径流量占比为65.5 %。在年代尺度上径流的丰枯变化存在差异,1970—1979年和1990—1999年径流量呈显著减少趋势;影响汛期和全年尺度径流变化的主控因子均为降水,贡献率达50%,其次是太阳辐射,在汛期和全年的贡献率分别为14.37%、18.45%。非汛期影响径流变化的主控因子为NDVI（贡献率30.08%）与太阳辐射（贡献率30.05%）,且NDVI对径流变化的滞后效应更明显,其他因子贡献大小依次为降水、空气比湿、气温。     

气候变化对雅鲁藏布江流域植被动态的影响机制

基于雅鲁藏布江流域1981—2015年长时间序列植被、降水、气温和干旱数据集,采用非参数统计方法Sen’s slope和Mann-Kendall趋势检验法识别了各要素时空变化特征,采用Pearson相关性分析和地统计学方法分析了植被覆盖对气候变化响应的时滞效应,探讨了气候变化对植被动态的影响机制。结果表明：归一化植被指数(NDVI)大体由上游至下游呈逐渐增大的空间分布特征,且中游部分地区植被有所改善,下游地区存在一定退化现象;流域上游主要受气温影响呈干旱化,中游和下游地区受降水影响趋于暖湿化;流域上游和中游地区NDVI与降水和干旱呈显著正相关关系,且主要在滞后1月时相关性最高,中游及下游东南部NDVI与气温呈显著负相关关系,滞后0～3月的区域均有分布。     

1982—2015年永定河山区植被变化及对天然径流的影响

采用归一化植被指数NDVI和气温、降水、径流等监测资料,在分析永定河山区NDVI时空变化的基础上,通过构建地理加权回归模型,研究了流域内NDVI和降水、平均气温的回归参数及残差的空间关系特征,定量估算了永定河山区NDVI变化对天然径流量衰减的影响。结果表明： 1982—2015年永定河山区在土地利用格局总体变化不大的情况下,年、季尺度的NDVI均显著增加,NDVI和降水、平均气温的空间回归参数及残差的均值、趋势均具有显著的空间异质性,降水、气温等气候因素和人类活动对NDVI均表现为促进作用,但各影响因素趋势变化的时空分布差异显著。永定河山区天然径流量具有显著的衰减趋势,结合Budyko方程发现流域天然径流量对植被变化具有高度敏感性,以植被变化为突出特征的下垫面变化对永定河天然径流衰减的贡献率达到了80%,流域植被保护和水土保持对天然径流量衰减的这种影响应给予高度重视。     

黄河流域1982—2015年不同气候区植被时空变化特征及其影响因素

研究不同气候区植被覆盖的时空变化及气候因子与植被生长的关系,对生态环境建设与治理具有重要意义。基于1982—2015年GIMMS NDVI 3g数据集,运用均值法、Sen+Mann-Kendall趋势分析、偏相关系数、多元线性回归模型+残差法等方法,分析了黄河流域不同气候区生长季植被时空变化特征及气候因子与人类活动对植被变化的影响。结果表明:①1982—2015年黄河流域及不同气候区归一化植被指数(NDVI)年际变化呈缓慢上升趋势,干旱区变化波动平稳,半湿润区变化较明显。②34 a来各气候区大部分地区植被呈显著增加,半干旱区所占面积比例最大,不显著减少主要分布在半湿润区西南部及南部。③各气候区降水、气温、日照时数对NDVI表现出正影响,且日照影响最大;在半干旱区降水对NDVI影响最大,在半湿润区影响最小,在半湿润区气温对NDVI影响最大,在干旱区影响最小。④34 a来,人类活动对各气候区植被的积极影响明显大于消极影响。     

秃尾河流域植被覆盖变化及其对径流的影响

黄土高原地区水土流失严重,生态环境脆弱。随着退耕还林还草政策的有序实施,区域植被覆盖率从90年代末开始显著提高,但河川径流也随之显著减少,对黄土高原区的水资源安全造成了重要影响。选取陕北秃尾河流域为研究对象,通过分析流域植被变化特征,检验径流序列趋势变化、变异特征以及其与降水、植被指数(NDVI)的相关关系,探讨了降水与植被覆盖变化对径流的影响,并使用基于Budyko假设的弹性系数法对不同时段的贡献率进行了定量分析,指出其影响径流缩减的物理机制。研究结果表明:(1)秃尾河流域植被覆盖格局总体为东南高、西北低,且近年来逐渐趋好,特别是2000年后流域植被覆盖率显著上升,到2013年年均NDVI值已达0.45,其变化主要表现为西北部未利用土地转化为草地和林地;(2)近年来秃尾河流域径流显著持续减少,且以1983和1997年为拐点呈三阶段变化,而降水、潜在蒸散发呈不显著减少,且潜在蒸发量和径流量的下降趋势将可能持续;(3)1984—1997年间流域降水驱动径流减少,两者呈现较强的正相关性,1997年后流域植被覆盖变化显著,表现为与径流的强烈负相关性,并成为引发径流显著减少的主因;(4)由Budyko方程计算得到的下垫面参数n与年NDVI值具有相同的变化趋势,验证了弹性系数法的适用性。定量分析结果表明1984—1997年间气候变化与覆被变化对径流变化呈异向影响,气候变化使径流减少而覆被变化使径流增多,且前者贡献率明显高于后者。之后,覆被改变对径流缩减的影响显著增强,贡献率高达75%以上。由物理解析可知,当前气候环境下植被覆被变化正在逐渐主导流域的径流变化,"地表变绿"可能对流域水安全造成潜在威胁。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry,Arizona, USA

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following long- and short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined. Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged <30% of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50% of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77% of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species. There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C. glomerata and Oscillatoria. Cladophora was the dominant phytobenthos species on cobbles below the baseflow and Oscillatoria was dominant on cobbles in the varial zone. In general, the Cladophora biomass decreased under intermittent drying conditions, while Oscillatoria declined under permanently wet conditions. Diatom composition was not significantly different between treatments; however, their density was lower on desiccated cobbles. Diatom density on desiccated cobbles in the submerged and varial zones averaged 69 and 42% of that of the controls, respectively. Recovery and maintenance of benthic resources are hindered by fluctuating flow regimes driven by electricity and irrigation requirements. Repeated desiccation of the phytobenthos has major effects on the bottom-up interactions in the Colorado River ecosystem. © 1998 John Wiley & Sons, Ltd.