Exploring the spatio-temporal impacts of farmland reforestation on ecological connectivity using circuit theory: A case study in the agro-pastoral ecotone of North China   总被引：1，自引：0，他引：1  

Liu  Xiaojing  Liu  Dianfeng  Zhao  Hongzhuo  He  Jianhua  Liu  Yaolin 《地理学报(英文版)》2020,30(9):1419-1435

Farmland reforestation can contribute substantially to ecological restoration.Previous studies have extensively examined the ecological effects of farmland reforestation,but few of them have investigated the spatiotemporal responses of broad-scale landscape connectivity to reforestation.By using a typical agro-pastoral ecotone in northern China as a case study,we addressed this issue based on an innovative integration of circuit theory approach and counterfactual analysis.The forest connectivity through multiple dispersal pathways was measured using the circuit theory approach,and its spatiotemporal changes after reforestation were evaluated by counterfactual analysis.The results showed that from 2000–2015,the reforested farmland occupied 2095 km~2,and 12.5% was on steeply sloped land.Farmland reforestation caused a greater increase in ecological connectivity by adding new ecological corridors and stepping stones in scattered forest areas rather than in areas with dense forest distributions.The newly added corridors and stepping stones were fragmented,short and narrow and thus deserve powerful protection.Future reforestation to improve landscape connectivity should highlight pinch point protection and obstacle removal as well as the tradeoff between farmland loss and farmer survival.Our findings are expected to inform the optimization of the Grain for Green policy from the perspective of broad-scale biodiversity conservation.  相似文献   

基于电流理论识别多物种扩散廊道的优先度——以西南西双版纳为例（英文）   总被引：1，自引：1，他引：0  

尹艺洁  刘世梁  孙永秀  赵爽  安毅  董世魁  Ana COXIXO 《地理学报(英文版)》2019,29(7):1228-1242

Ecological corridor networks can efficiently improve regional landscape connectivity. Corridors for multiple faunal species movements are receiving increasing attention and graph theory is considered a promising way to explore landscape connectivity. In Xishuangbanna, the circuit theory was applied to explore the corridor networks for biodiversity for the first time. In addition, disturbances caused by the road network and the protection efficiency of National Nature Reserves and planned area for corridors were evaluated. Results indicated that the regional corridor networks could be estimated using a modified circuit method and Zonation model. Spatially, the key corridors were concentrated in the central-western, southeastern and northern regions. We detected 66 main intersections between key corridors and the road buffer. Of these points, 65% are forest, 23% grassland and 12% farmland. More than half of the area of National Nature Reserves constituted the top 50% of the corridors, and the planned corridor areas could efficiently protect some key corridors. However, these reserves only protected about 17% of regional key corridors, and the corridor conservation area in the western and northern regions were absent. The issues addressed in our study aided in the elucidation of the importance of regional landscape connectivity assessments and operational approaches in conservation planning.  相似文献   

珠江三角洲城际轨道网络结构：基于连接、容量和流量的对比   总被引：2，自引：2，他引：0  

李涛  张维阳  曹小曙  汪丽  张隆 《地理研究》2019,38(11):2730-2744

城际交通网络包含提供联系可能性的基础设施连接网络（铁轨等）,反映承载容量的组织网络（列车班次等）与实际需求的流量网络（客货流等）3类,分别从连接可能性、潜力容量和实际流量三方面映射了网络发育的不同特征。理清城市在这3种维度网络中的不同位置,对分辨城市的节点位势和城市系统构造具有重要意义。以珠三角城市群城际轨道网络为研究对象,本文系统分析了3种网络整体结构、城市的节点位置和城际连接性的差异。结果表明：虽然3种网络城镇地方中心度均呈现出显著的等级差异特征,相较于需求网络,设施网络和组织网络扁平化特征更为显著;组织网络和需求网络均表现出了以广深为核心、以广深、广珠和广佛为主要联系的结构体系,设施网络则呈现出明显的“沿线效应”,突出了珠江口西岸广珠城际沿线的骨干地位;与组织和设施网络相比,需求网络突出了肇庆、江门等城市的重要性,轨道沿线中小城镇位势则逐渐降低。研究一方面通过区分3种铁路交通网络强调了城市网络研究中明确“刻画何种网络”的重要性;另一方面通过对比城市节点和城际连接在不同网络中的位置,识别出可能性、利用潜力和实际流量的差异,为交通线路规划和区域空间优化政策制定提供依据。  相似文献   

水利工程对长江荆南三口水系连通功能变化的影响     

李景保  何蒙  吕殿青  于丹丹  杨波 《热带地理》2019,39(1):135-143

为了揭示荆南三口地区水利工程与水系连通功能的定量关系,基于1954、1975、1990、2008和2016年5期的水利工程与水系连通功能的相关数据,运用集对分析和相关分析等方法,定量评价了水利工程对长江荆南三口水系连通功能的影响,结果表明：1）区内外水利工程与多年日均径流保证率、河道断流率、输沙效率的相关系数（R²）均＞0.5,皆达到显著性水平。2）自然功能3个模块的联系主值数基本呈下降趋势,但物质能量传递功能与生态维系功能下降尤为明显。1990年之前物质能量传递与生态维系功能处于一个较好的状态,1990年后这2项功能的等级已下降至“差”;社会功能3个模块的联系主值数的变化各不相同。洪涝防御功能一直处于上升状态,而水资源调配功能和水能与水运资源利用功能都在1954-1990年呈下降趋势,1990年后,水资源调配功能逐渐回升,水能与水运资源利用功能持续下降。3）1954-2008年自然功能等级和综合功能等级都有所下降,直到2016年才稍有回升,但升幅较小,等级较低;社会功能等级在1954-1990年较低,2008年以后回升,且明显高于自然功能等级。  相似文献   

兼顾几何连通性与名称一致性的城市道路实体构建     

李元復  孙群  季晓林  周炤  吕铮 《测绘通报》2019,(4):115-118

提出了一种兼顾几何连通性与名称一致性的实体化构建方法。首先,对城市道路的实体化原则进行描述;其次,提出基于反比例函数的归一化的几何连通度度量方法,以及基于语义切分的名称匹配度度量方法;最后,通过路口提取、综合匹配度计算、路段匹配、路段连接及借道处理等步骤,实现完整的城市道路实体化构建流程。以郑州市主城区为试验区域进行具体构建试验,验证了本方法的准确性。试验结果表明,利用本文提出的算法进行实体化匹配的总体准确率为99.89%。  相似文献   

Clastic injectites,internal structures and flow regime during injection: The Sea Lion Injectite System,North Falkland Basin     

Thomas J. H. Dodd  Dave J. McCarthy  Stuart M. Clarke 《Sedimentology》2020,67(2):1014-1044

This paper details and describes a suite of 143 sub-seismic-scale clastic injectites encountered within the early Cretaceous, early post-rift of the deep-lacustrine North Falkland Basin. The injectites, referred to here as the Sea Lion Injectite System, are encountered below, above and in between the hydrocarbon-bearing, deep-lacustrine turbidite sandstones of the Bleaker 30, Sea Lion North, Sea Lion, Casper and Beverley fans. Sedimentary structures are documented within the injectites including: planar laminations, mud-clast imbrication and clast alignment. Clasts align along centimetre-scale foresets formed through ripple-scale bedform migration in a hydraulically-open fracture. The style of flow within the injectite system is interpreted as initially through fluid turbulence during an open fracture phase, which was followed by a later stage where laminar flow dominated, most likely during the closing phase of the fracture system. The host rocks display evidence for ductile deformation, which along with ptygmatic folding of dykes and internally injected mud-clasts, suggests a period of injection into relatively uncompacted sediments. Evidence for brittle fracturing, in the form of stepped margins may be indicative of a separate phase of emplacement into more-compacted sediments. This variability in deformation styles is related to multi-phased injection episodes into host strata at different stages of consolidation and lithification at shallow burial depths. Injectites have been identified in four stratigraphic groupings: above the Bleaker 30 Fan and within/above the Sea Lion North Fan; within the hydrocarbon-bearing Sea Lion Fan; overlying the Sea Lion Fan; and above/below the hydrocarbon-bearing Casper and Beverley fans. This spatial association with the hydrocarbon-bearing fans of the North Falkland Basin is important, considering the ability of injectite networks to form effective fluid-flow conduits in the subsurface. Consequently, the findings of this study will improve the characterization of sub-seismic scale injectites (and therefore fluid conduits) within otherwise impermeable strata.  相似文献   

DTM resolution controls the accuracy of estimating surface runoff indicators in flat,lowland landscapes     

Peter Schaap  Ype van der Velde  Perry de Louw  Harm Bartholomeus 《水文研究》2024,38(5):e15173

Surface runoff plays an important role in contaminant transport, nutrient loss, soil erosion and peak discharges in streams and rivers. Because it is the result of a variety of complex hydrological processes, estimating surface runoff using physically based hydrological models is challenging. Upscaling of physical soil properties is necessary to cope with the limits of computational power in surface runoff modelling. In flat landscapes, the (micro)topographic surface controls the onset and progression of surface runoff on saturated soils during rain events. Therefore, its proper representation is crucial when attempting to model and predict surface runoff. In this study, the influence of microtopography (centimetre scale) on estimations of maximum depression storage (MDS), random roughness (RR) and the connectivity threshold (CT) is explored. These properties are selected because they often serve as surface runoff indicators in hydrological modelling. To characterize microtopography, a terrestrial laser scanner (TLS) is used to generate a digital terrain model (DTM) of the study site with a horizontal spatial resolution of 5 cm. MDS, RR and CT are then calculated and compared to the values generated from the publicly available Dutch national DTM dataset with a resolution of 50 cm. Our results show considerable differences in MDS, RR and CT when calculated for the different input resolution datasets. Using DTMs that do not sufficiently capture microtopography leads to underestimation of MDS and RR, and to overestimation of CT. Our findings indicate that surface runoff indicators, and thereby the surface runoff response of a saturated surface to rainfall events, are defined at scales smaller than the scales of typically available DTMs. Understanding surface runoff through modelling studies therefore requires a framework that accounts for this lack of information arising from using coarser resolution DTMs. We demonstrate a linear relationship between MDS values generated from the different resolution DTMs. This opens the possibility of using empirical scaling relationships between high- and lower-resolution DTMs to account for microtopography. Repetition of our measurements on similar surfaces would contribute to establishing such empirical scaling relationships. Our results should be seen as indicative of flat landscapes and surfaces where centimetre scale microtopography is relevant.  相似文献   

Characterizing stream temperature hysteresis in forested headwater streams     

Lorrayne Miralha  Austin D. Wissler  Catalina Segura  Kevin D. Bladon 《水文研究》2023,37(1):e14795

Stream temperature (T_s) is a key water quality parameter that controls several biological, ecological, and chemical processes in aquatic systems. In forested headwaters, exchanges of energy across air-water-streambed interfaces may influence T_s regimes, especially during storm events as the sources of runoff change over space and time. Analysis of the hysteretic behaviour of T_s during storm events may provide insights into rainfall-runoff responses, but such relationships have not been thoroughly investigated. As such, our objectives were to (a) quantify the variability of stream temperature hysteresis across seasons in different sub-regions and (b) investigate the relationship between the hysteretic response and catchment characteristics. T_s hysteresis during storm events was assessed based on the hysteresis index (HI), which describes the directionality of hysteresis loops, and the temperature response index (TRI), which indicates whether T_s increased or decreased during a storm event. We analysed T_s data from 10 forested headwater reaches in two sub-regions (McGarvey and West Fork Tectah) in Northern California. We also performed a clustering analysis to examine the relationship amongst HI, TRI, topographic metrics, and meteorological characteristics of the study areas. Overall, the hysteretic behaviour of T_s varied across seasons—the greatest HI occurred during spring and summer. Interestingly, in the McGarvey streams the variability in T_s hysteresis co-varied strongly with topographic metrics (i.e., upslope accumulative area, average channel slope, topographic wetness index). Comparatively, in West Fork Tectah the variability of T_s hysteresis co-varied most strongly with meteorological metrics (i.e., antecedent rainfall events, solar radiation, and air temperature). Variables such as the gradient between stream and air temperatures, slope, and wetted width were significant for both sub-regional hysteretic patterns. We posit that the drivers of T_s response during storms are likely dependent on catchment physiographic characteristics. Our study also illustrated the potential utility of stream temperature as a tracer for improving the understanding of hydrologic connectivity and shifts in the dominant runoff contributions to streamflow during storm events.  相似文献   

基于生态网络功能辨识的海坛岛生态保护和修复策略          下载免费PDF全文

陈鹏  吴剑  傅世锋  潘翔 《应用海洋学学报》2021,40(1):82-90

优化国土空间开发格局和生态保护修复成为推进生态文明建设的重要举措,构建区域生态网络并识别其关键生态功能区域,是开展国土空间格局优化和生态修复工作的重要切入点.选择海坛岛为研究案例,利用遥感信息源和GIS空间分析等技术方法,辨识出区域潜在的生态网络功能结构.通过景观连接度的重要值评价,揭示海坛岛生态源地和生态节点的重要性...  相似文献