耕地细碎化对可持续集约利用的影响机理与治理框架   总被引：2，自引：0，他引：2  

刘晶  金晓斌  徐伟义  周寅康 《地理学报》2022,77(11):2703-2720

科学调适耕地细碎现象使其益于耕地可持续集约利用且与环境背景相适应是细碎化治理研究及实践长期努力的目标。从耕地细碎化与耕地可持续集约利用的理论内涵出发,剖析细碎化影响耕地可持续集约利用的理论机理,构建面向可持续集约利用的耕地细碎化“特征—影响—环境”综合治理分析框架,探讨细碎化治理中的关键问题、情景决策机理及空间尺度效应,希冀为优化细碎化治理提供理论借鉴。结果表明：① 耕地细碎化是涵盖资源、空间、利用及权属等多维属性特征的复合体系,对资源利用、农业生产、景观生态等影响广泛且复杂,并通过多尺度全方位、差异性和不确定性、交互式级联传导等作用路径成为影响耕地可持续集约利用的核心和关键。② 耕地细碎化本身并不具备明显的问题/价值倾向,其成为问题或有益的情形和程度取决于其影响及当地自然地理、农业生态、社会经济等环境背景及农业发展定位。③ 以细碎化特征表现为基础,以其对耕地可持续集约利用多维影响为依据,以其与地方环境背景相适应为准则的耕地细碎化“特征—影响—环境”综合治理框架通过解构复杂细碎化情景治理决策中的5个关键问题、两个关系、两个倾向及3级空间尺度互联互通机理,为从多维度、复合视角科学诊断细碎化治理导向、优化治理模式提供新思路,有益于完善细碎化治理体系、促进耕地可持续集约利用。  相似文献   

IMPACT OF ROAD CONSTRUCTION ON VEGETATION ALONGSIDE QINGHAI-XIZANG HIGHWAY AND RAILWAY   总被引：1，自引：0，他引：1  

CHENHui LShuang-cheng ZHANGYi-li 《中国地理科学(英文版)》2003,13(4):340-346

Based on the field investigation in August 2001 and August 2002, digital China Vegetation Map in 2001 and Qinghai-Xizang(Tibet) Plateau Vegetation Regionalization Map in 1996, vegetation characteristics along two sides of Qinghai-Xizang highway and railway are studied in this paper. Meanwhile, the impact of Qinghai-Xizang highway and railway constructions on the vegetation types are analyzed using ARCVIEW. ARC/1NFO and PATCH ANALYSIS. It was found that: 1) Qinghai-Xizang highway and railway span 9 latitudes, 12 longitudes and 6 physical geographic regions (East Qinghai and Qilian mountain steppe region, Qaidam mountain desert region,South Qinghai-Xizang alpine meadow steppe region. Qiangtang alpine steppe region, Golog-Nagqu alpine shrubmeadow region and South Xizang mountain shrub steppe region); 2) the construction of Qinghai-Xizang highway and railway destroyed natural vegetation and landscape, especially in 50m-wide buffer regions along both sides of the roads, it was estimated that the net primary productivity deceased by about 30 504.62t/a and the gross biomass deceased by 432 919.25-1 436 104.3t. The losing primary productivity accounted for 5.70% of the annual primary productivity within lkm-wide buffer regions (535 005.07-535 740.11t/a), and only 0.80%-0.89% of that within 10km-wide buffer regions (3 408 950.45-3 810 480.92t/a). The losing gross biomass was about 9.47%-17.06% of the gross biomass within lkm-wide buffer regions (7 502 971.85-25 488 342.71t), and only 1.47%-2.94% of that within 10km-wide buffer regions (43 615 065.35-164 150 665.37t).  相似文献   

Distribution Law For Particle Fragmentation Times In A Theory For Striated Tails Of Dust Comets: Application To Comet Hale-Bopp (C/1995 O1)     

Z. Sekenina  J. Pittichová 《Earth, Moon, and Planets》1997,78(1-3):339-346

Sekanina and Farrell's model for the striated dust tails of comets describes the formation of striae as a two-step fragmentation process that is characterized by an ejection time t_e of parent particles, by their radiation pressure acceleration β_p, and by their fragmentation time t_f. Of these three, t_f is the weakest parameter in that a range oft_f offers a set of nearly equivalent solutions. In this context, we comment on Nishioka et al.'s finite-lifetime model, which is a modification of the fragmentation model. We propose a truncated Gaussian function as a first-approximation distribution law for particle fragmentation times. We apply this generalized model to a stria in comet Hale-Bopp detected on March 5–15, 1997 and analyzed by Pittichová et al. in a recent paper. We find that in order to fit the stria's estimated width of ∼150 000 km, the fragmentation times cannot be distributed over a period of more than approximately 2 to 3 days. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

HIGH SPATIAL AND TEMPORAL RESOLUTION OPTICAL SEARCH FOR EVIDENCE OF METEOROID FRAGMENTATION     

R. L. Hawkes  P. G. Brown  N. R. Kaiser  A. J. Faloon  K. A. Hill  L. A. Rogers 《Earth, Moon, and Planets》2004,95(1-4):587-593

A digital image intensified CCD camera with an electronically gated image intensifier was used to produce very short duration images of meteors. The observational system employed a 0.40 m F/4.5 Newtonian telescope to obtain high spatial resolution. A second intensified CCD camera was used to yield height information using parallax. At a typical meteor height one pixel (for the vertically oriented system) corresponded to about 1.1 m. A sampling of 59 mainly sporadic meteors was analyzed. There is clear variability from meteor to meteor, with many meteors (nearly 50%) showing only a small amount of wake, while some meteors (approximately 20%) have the off segments completely filled in.  相似文献   

基于COMSOL的高压放电破碎岩石仿真研究          下载免费PDF全文

马宁  金博  周鹏  钱阳  薛启龙 《探矿工程》2022,49(6):62-70

常规旋挖钻机在钻进硬岩地层钻孔桩时存在进尺困难,钻头磨损大等问题。高压脉冲放电岩石破碎技术作为一种新型非机械式岩石破碎技术,在硬岩钻进领域具有广阔的应用前景。本文在分析高压脉冲放电破碎岩石机理的基础上,运用COMSOL Multiphusics软件,建立电-热-力多物理场耦合模型,开展花岗岩和砂岩在电压、电极间距、电解质等条件下的破碎规律仿真研究。结果表明,随着电压的增大,岩石产生的破碎区域呈线性增大;电极间距的增大导致岩石破碎区域减小;液体介质的电导率大小对放电结果的影响不大;选用多电极对放电可有效增加岩石的破碎面积。研究结果可为高压放电破碎岩石技术提供参考。  相似文献   

粒子重复冲击破岩细观损伤及破碎特征试验研究     

鞠明和  陶泽军  李晓锋  蔚立元  姜礼杰  李晓昭 《岩土力学》2022,43(12):3281-3293

粒子冲击破岩作为一种新型辅助破岩技术已在钻探和油气开采等领域得到有效运用,其在极坚硬岩层中隧（巷）道辅助掘进方面具有广阔的应用前景。从试验角度研究了粒子的冲击次数、颗粒强度及冲击速度等因素对极坚硬花岗岩表面冲击坑损伤破碎特征的影响,对冲击坑三维形貌、岩石碎屑及坑内矿物破碎特征进行了定量分析。结果表明：成坑最大深度随冲击次数增加呈抛物线趋势增大,而成坑体积和坑顶面积随冲击次数增加呈线性增长;成坑体积随冲击速度呈先增大后减小的规律,该临界冲击速度约为82.5 m/s;冲击坑中心与外部的细观破碎机制差异导致岩石碎屑平均尺寸具有明显的双峰特征。从能量角度分析发现,成坑体积、坑顶面积和最大深度随粒子动能在双对数坐标系下线性增长。基于图像处理方法获得了冲击坑周边主要矿物内部裂纹分布随冲击速度和次数增加的分形维数变化规律。破岩效果表明,增大粒子冲击速度和冲击次数能有效扩大岩石冲击坑的损伤范围,但冲击速度的影响程度显著大于冲击次数。  相似文献   

A quantitative performance comparison of paddy rice acreage estimation using stratified sampling strategies with different stratification indicators   总被引：2，自引：0，他引：2  

Peijun Sun  Russell G. Congalton  Yaozhong Pan  Xiufang Zhu 《International Journal of Digital Earth》2018,11(10):1001-1019

Various indicators derived from thematic maps have been widely used to determine the strata needed to perform stratified sampling. However, these indicators typically do not quantify the spatial errors in the crop thematic maps that are needed to reduce the uncertainty. To address this lack of error information, this paper introduces a hybrid entropy indicator (HEI). Two conventional indicators, the acreage indicator (AI) and the fragmentation indicator (FI), were also evaluated to compare the results of the three indicators in a homogeneous agricultural area (Pinghu, PH) and a heterogeneous agricultural area (Zhuji, ZJ). The results show that HEI performs the best in heterogeneous areas with the lowest coefficient of variation (CV) (as low as 1.59%) and also has the highest estimation accuracy with the lowest standard deviation of estimation. For both areas, the performances of HEI and AI are very similar, and better than FI. These results highlight that the HEI should be considered as an effective indicator and used in place of AI and FI to help improve sampling efficiency of crop acreage estimation, while FI is not recommended. Furthermore, the positive performance achieved using HEI indicates the potential for incorporating thematic map uncertainty information to improve sampling efficiency.  相似文献   

解决土地碎片化的制度框架设计   总被引：1，自引：0，他引：1  

郧宛琪  朱道林  梁梦茵 《地域研究与开发》2015,(4)

为解决土地碎片化问题,采用文献统计和比较分析等研究方法,在对土地碎片化现状、原因与问题分析的基础上,通过总结国内外实践经验,提出了解决土地碎片化的制度框架。研究结果表明,土地碎片化的产生既有自然原因也有制度原因,所带来的问题主要包括:1田埂面积多而导致的耕地资源浪费;2地界纠纷多而导致新技术新产品难以推广;3谈判成本高导致农地资源无法合理进行配置;4机械水平低导致劳动生产率、土地生产率和成本产值率也随之下降等。必须要通过明晰产权关系、构建市场平台、创建新型农业经营体系、推广"良田良种良法"等政策措施来逐步破解中国土地碎片化难题。  相似文献   

长沙城市空间破碎化的格局特征及其影响因素   总被引：1，自引：1，他引：1  

朱佩娟  郎泽慧  贺清云  张美芳  吴国权 《地理研究》2020,39(8):1739-1754

空间破碎化是城市空间结构研究亟待深化的重要课题。从形态、联系以及功能3个维度构建城市空间破碎化测度指标,并运用地理探测器模型,探讨长沙城市空间破碎化的格局特征及其影响因素。主要结论：① 城市空间破碎化可从形态分割、联系阻隔、功能失序三方面进行测度,形态分割可用平均地块面积指数表征,联系阻隔可用平均阻抗指数刻画,功能失序可用功能多样指数、邻接冲突指数来反映;② 长沙城市空间破碎化呈现圈层式分异为主、扇形扩展分异为辅的格局特征,低破碎化区主要分布在城市核心区,高破碎化区沿着特定的扇面向外围扩展,且主要分布在大型封闭社区、工业园区、山地绿地及大型站场等区域;③ 长沙城市空间破碎化的空间分异是多因素综合作用的结果,其中海拔、坡度等自然因素是基础因素,土地价格、人口密度、设施投入是主导因素;④ 长沙城市空间破碎化治理可从突破市场供给约束、市场需求约束和设施丰度约束三方面着手,采取针对性调控对策,以最大程度地消减空间破碎化带来的负面效应。  相似文献   

Movement patterns of four coral reef fish species in a fragmented habitat in New Caledonia: implications for the design of marine protected area networks     

Chateau  Olivier; Wantiez  Laurent 《ICES Journal of Marine Science》2009,66(1):50-55

  相似文献