Stormflow threshold behaviour in a subtropical mountainous headwater catchment during forest recovery period     

Lezhang Wei  Zhijun Qiu  Guangyi Zhou  Tsuyoshi Kinouchi  Yu Liu 《水文研究》2020,34(8):1728-1740

Forest ecohydrological feedbacks complicate the threshold behaviour of stormflow response to precipitation or wetting conditions on a long-term scale (e.g. several years). In this study, the threshold behaviours in an evergreen-deciduous mixed forested headwater catchment in southern China were examined during 2009–2015, when damaged vegetation was recovering after the great 2008 Chinese ice and snowstorm. The non-uniqueness of the thresholds and the slow and rapid responses of stormflow at the outlet of the catchment in different hydro-climate datasets with different maximum values of gross precipitation (P) and sums of precipitation and antecedent soil moisture index (P + ASI) were assessed. The thresholds of P and P + ASI required to trigger stormflows (i.e. ‘generation thresholds’) and the transition from slow to rapid responses of stormflow (i.e. ‘rise thresholds’) were compared both seasonally and annually. The results indicated significant differences in the analysed datasets, highlighting the need to compare thresholds with care to avoid misinterpretation. Seasonal variations in threshold behaviours in the catchment suggested that vegetation canopy interception contributed to higher rise thresholds, and wetter conditions resulted in higher runoff sensitivity to precipitation during the growing and rainy seasons. Furthermore, the generation thresholds were higher in the dormant season, possibly due to drier soil moisture conditions in the near-channel areas. During the vegetation recovery period, the annual generation thresholds increased, however the rise thresholds did not exhibit a similar trend. The rapid stormflow response above the threshold decreased, possibly due to transpiration and interception of the recovered vegetation. However, the slow stormflow response to small rainfall events below the thresholds was higher in wetter years but lower in drier years, suggesting that the total water input dominated the stormflow response during small rainfall events. In conclusion, the seasonal and annual variations in threshold behaviours highlight that vegetation recovery and hydro-climatic conditions had a notable impact on the stormflow response.  相似文献   

GRACE时变信号恢复方法对比分析     

刘冰石  邹贤才 《大地测量与地球动力学》2019,39(2):204-209

针对利用GRACE重力数据反演地表质量变化过程中产生的时变信号削弱和泄露现象，分别采用尺度因子法和迭代恢复法对信号进行恢复，并选用CSR Mascon产品从时间序列变化和空间分布两个角度对两种恢复方法的效果进行对比分析。结果表明：1)尺度因子法虽实现上较为简单，但其计算结果完全依赖于所选的先验模型，当所选模型的可靠性较差时，会影响到GRACE反演结果的可靠性。2)迭代恢复法的恢复过程仅受GRACE原始观测值的约束，能较好地恢复研究区域的长期趋势信号和周期信号，但在部分区域可能存在信号过量恢复的现象。建议采用迭代恢复法进行GRACE时变信号恢复。  相似文献   

“一带一路”成员国居民健康状况的时空统计分析     

郭文杰  秦昆  毛宗福  王一喆  汪瑶  许刚  马露 《地球信息科学学报》2020,22(5):1133-1141

健康是影响不同国家和地区发展的关键因素,全面了解“一带一路”成员国的居民健康状况,是探讨“一带一路”成员国之间健康医疗合作的重要基础。本文选择了4个代表性的健康状况指标（出生期望寿命、总生育率、过早非传染性疾病死亡率和结核病发病率）,利用Moran's I指数、Getis-Ord G指数对“一带一路”135个成员国的健康状况进行时空统计,分析了健康状况的空间相关性和空间分布模式,研究了健康状况的时空格局。研究发现：① 2000—2016年“一带一路”大部分成员国的各项健康状况指标均朝着改善和优化方向发展;健康状况指标均呈现显著的正空间自相关性;② 总体而言,在“一带一路”成员国中,欧洲国家的居民健康状况最好;南北美洲和大洋洲国家的居民健康状况良好;亚洲国家的居民健康状况总体良好,但东南亚部分国家的结核病发病率较高;非洲国家的居民健康状况虽有明显改善,但仍处于较低状态。因此,“一带一路”成员国应进一步加强健康医疗合作,共同推动健康丝绸之路的发展。  相似文献   

Evaluating post-wildfire logging-slash cover treatment to reduce hillslope erosion after salvage logging using ground measurements and remote sensing     

Peter R. Robichaud  Sarah A. Lewis  Robert E. Brown  Edwin D. Bone  Erin S. Brooks 《水文研究》2020,34(23):4431-4445

Continuing long and extensive wildfire seasons in the Western US emphasize the need for better understanding of wildfire impacts including post-fire management scenarios. Advancements in our understanding of post-fire hillslope erosion and watershed response such as flooding, sediment yield, and debris flows have recently received considerable attention. The potential impacts of removing dead trees, called salvage logging, has been studied, however the use of remotely sensed imagery after salvage logging to evaluate spatial patterns and recovery is novel. The 2015 North Star Fire provided an opportunity to evaluate hillslope erosion reduction using two field experiments and coincidental remotely sensed imagery over 3 years. Simulated rill experiments with four flow rates were used to quantify hillslope erosion on skidder trails with and without added logging slash compared with a burned-only control. Seven replicated hillslope silt fence plots with the same treatments were also evaluated for natural rainfall events. WorldView-2 satellite imagery was used to relate ground cover and erodible bare soil between the two experiments using multi-temporal Normalized Differenced Vegetation Index (NDVI) values. Results indicate that the skid trails produced significantly more sediment (0.70 g s⁻¹) than either the slash treated skid trail (0.34 g s⁻¹) or controls (0.04 g s⁻¹) with the simulated rill experiment. Similarly, under natural rainfall conditions sediment yield from hillslope silt fence plots was significantly greater for the skid trail (3.42 Mg ha⁻¹) than either the slash treated skid trail (0.18 Mg ha⁻¹) or controls (0 Mg ha⁻¹). An NDVI value of 0.32 on all plots over all years corresponded to a ground cover of about 60% which is an established threshold for erosion reduction. Significant relationships between NDVI, ground cover, and sediment values suggest that NDVI may help managers evaluate ground cover and erosion potential remotely after disturbances such as a wildfire or salvage logging.  相似文献   

欠发达农区家庭贫困的动态转变分析——以河南省为例     

蔡磊  罗庆  李孟林 《地理科学进展》2021,40(3):468-476

精准扶贫战略实施以来,以收入标准衡量的农村贫困人口大幅下降,但贫困具有多维性、动态性的特点,开展农户贫困动态变化研究对新时期农村贫困的有效治理具有重要的指导意义。论文基于2010—2018年河南农村固定观察点数据,从收入、生活条件、教育3个维度构建农户多维贫困评价指标体系,并运用马尔科夫概率转移矩阵和面板Logit模型对贫困状态类型转移及家庭陷入贫困的影响因素进行实证分析。结果表明：① 多维贫困比单维贫困(尤其是收入贫困)更能准确反映农区贫困状况;② 2010—2018年间,单维贫困发生率与多维贫困发生率之间差距不断扩大,这很大程度与教育贫困发生率大幅上升,而生活条件贫困、收入教育贫困和三维贫困明显下降有关;③ 单维贫困家庭更易转入教育贫困,多维贫困家庭更容易转入教育生活条件贫困;④ 农户贫困的发生是户主特征、家庭特征和村庄特征共同作用的结果,但不同类型贫困发生的影响因素有显著差异。与单维贫困发生相比,多维贫困发生受到更少因素的显著影响,并且各影响因素的作用更大。上述结论意味着新时期扶贫工作重点转向多维贫困的同时,应依据贫困类型制定具体扶贫措施,尤其重视教育等公共服务的供给。  相似文献   

浙江省重要湿地生态状况评价     

吴伟志  梁立成 《湿地科学与管理》2021,(1)

以浙江省80个重要湿地为研究对象,综合考虑景观、生物多样性及社会发展等多种因素,构建湿地生态状况评价指标体系。采用层次分析法(AHP)和德尔菲法,对13个评价指标进行分级和赋值,计算每处重要湿地生态状况的综合得分,定量表征湿地的生态状况。结果表明:浙江省生态状况评级为“好”的湿地有20个,评级为“中”的湿地有36个,评级为“差”的湿地有24个,分别占浙江省重要湿地总数的25%、45%和30%。浙江省重要湿地生态状况总体良好,但部分湿地存在水质污染、富营养化和外来物种入侵等问题。  相似文献   

耦合手机信令数据和房价数据的城市不同经济水平人群行为活动模式研究   总被引：1，自引：0，他引：1  

关庆锋  任书良  姚尧  梁迅  周剑锋  袁泽皓  戴良洋 《地球信息科学学报》2020,22(1):100-112

有效分析城市不同经济水平人群的分布特征和活动模式对优化城市资源配置和揭示空间隔离现象有着极高的价值。但人群活动和社会经济等级数据较敏感,使得以往研究仅停留在宏观层面,难以合理划分人群经济等级并对其空间分布和活动模式进行定量分析。本研究以深圳为研究区,基于空间位置关联分析方法,耦合手机信令数据和细尺度房价数据实现了人群经济水平的准确划分,通过计算活动指标定量的分析了不同经济水平人群的空间分布和行为活动特征。研究表明：深圳市不同经济水平人群活动分布与各行政区经济发展相关,呈现“南高北低,西高东低”的格局;深圳市不同经济水平人群之间活动模式存在差异,活动范围、出行距离、出行速度与经济水平存在正向相关;高经济水平人群职住地点相距较远,存在跨行政区分布的现象。本研究分析了城市不同经济水平人群的空间分布特征和活动模式,对城市规划和解决社会不平等问题具有重要的参考价值。  相似文献   

一种用于篡改定位及近似恢复的水印算法     

侯翔  杨辉 《测绘科学技术学报》2017,34(3)

针对遥感影像易被非法篡改的问题,提出了一种用于篡改定位及近似恢复的遥感影像半脆弱水印方案。首先将二值伪随机矩阵作为认证水印,通过量化Contourlet变换各方向子带中绝对值最大的系数将其嵌入,然后采用影像4×4分块后的灰度平均值作为恢复水印,将其嵌入到最低有效位。水印检测不需要原始遥感影像参与,实现了盲提取。实验结果表明,算法对于噪声、JPEG压缩等合理性失真具有一定的鲁棒性,而对于恶意篡改等攻击具有脆弱性,能够实现篡改区域的精确定位和近似恢复,使恢复后的遥感影像满足基本的视觉要求,可有效保护遥感影像的安全。  相似文献   

Fishing in the Amazonian Forest: A Gendered Social Network Puzzle     

I. Díaz-Reviriego  Á. Fernández-Llamazares  P. L. Howard  J. L. Molina  V. Reyes-García 《社会与自然资源》2017,30(6):690-706

We employ social network analysis (SNA) to describe the structure of subsistence fishing social networks and to explore the relation between fishers’ emic perceptions of fishing expertise and their position in networks. Participant observation and quantitative methods were employed among the Tsimane’ Amerindians of the Bolivian Amazon. A multiple-regression quadratic assignment procedure was used to explore the extent to which gender, kinship, and age homophilies influence the formation of fishing networks. Logistic regressions were performed to determine the association between fishers’ expertise, their sociodemographic identities, and network centrality. We found that fishing networks are gendered and that there is a positive association between fishers’ expertise and centrality in networks, an association that is more striking for women than for men. We propose that a social network perspective broadens understanding of the relations that shape the intracultural distribution of fishing expertise, as well as natural resource access and use.  相似文献   

中国住宅出让地价发育特征及其影响因素分析   总被引：6，自引：2，他引：4  

韩娟  金晓斌  张志宏  孙伟  徐心茹  周寅康 《地理科学》2017,37(4):573-584

基于中国土地市场网2009~2013年招、拍、挂出让的住宅用地数据,以县级行政区域作为研究单元,建立区域住宅地价综合模型,选取地价水平、地价增长率和交易宗数作为评价指标,采用Ward系统聚类法,综合分析了中国住宅出让地价的发育特征,利用多分类Logistic回归模型探索了各类地价发育形态的潜在影响因素。结果表明：① 研究期内中国住宅出让地价总体呈现东高西低、沿海高于内陆、城市群带动周边区域发展、城市群内部围绕中心城市增长等空间格局特征;中西部地价高增长的单元多于东部,西北、东北中南部、四川盆地、河西走廊以及长江中下游地区是地价高增长的聚集区;住宅市场活跃度呈阶梯状变化,活跃度较高的地区主要分布在山东半岛、长三角、长江中游、辽宁中部、哈尔滨、成渝、滇中、呼包鄂等城市群。② 根据综合特征,中国住宅出让地价空间发育可分为成熟稳健型、发展完善型、成长发展型、萌芽起步型和成长受阻型5类,相邻发育形态在空间关系上表现出互为邻里的特征。③ 各类发育区的主要影响因素差异显著。区位条件、居民收入和财政收入是地价发育成熟度的主要影响因素;人均GDP、国土开发度提升将促进地价形态发育程度;而人口吸引力不足、基础设施建设相对滞后等将导致地价形态发育受阻。  相似文献