广东近40年来5～9用气候变化及与主要农作物关系     

刘黎明  陈创买 《热带地理》1996,(2)

本文以广东省４７个测站近４０年来６～９月降水量、平均气温、总日照时数和一些主要农作物逐年单产量资料为基础，用主分量分析、周期回归等方法，分析广东全省性的气候时空变化特征；分析一些主要农作物逐年单产的变化规律．用多元逐步回归分析方法探讨了广东全省性气候变化与同期及后期（１～３年）主要农作物单产量间的关系并作了预报．  相似文献   

地表水资源与天津粮食产量的宏观分析     

梁平德  刘爱霞 《气象》1995,21(6):44-47

分析了１９６３－１９９０年天津粮食产量与地表水资源的关系，同时计算了粮食产量随时间增长的趋势议程及扣除增长趋势的粮食相对产量序列。结果表明，由于天津地势低洼易涝，地表水资源量大于３５亿ｍ＾３的丰水年，粮食减产；而当年地表水资源量在３５亿ｍ＾３以下，前一年地表水资源量大于２０亿ｍ＾３，尤其是前一年为丰水年最有利于粮食增产。还分析了地表水资源对水稻、小麦、玉米等三种主要粮食作物的不同影响，揭示了地表水  相似文献   

Seasonal patterns of suspended sediment load and erosion-transport assessment in a Mediterranean basin     

A. Millares  H. A. Chikh  M. Habi  B. Morsli  J. P. Galve  J. V. Perez-Peña 《水文科学杂志》2020,65(6):969-983

ABSTRACT

To assess seasonal patterns of suspended sediment load and its erosion–transport interactions, 17 years of river monitoring data from the Isser River Basin (northwest Algeria) were studied, considering continuous and event-scale approaches. The results show significant differences in sediment yield and transport processes between dry and wet periods. A rate of 8 t ha^?1 year^?1 was estimated from continuous analysis, with values of 4.3 and 13 t ha^?1 year^?1 for wet and dry periods, respectively. Estimates of soil delivery ratio pointed to higher values during dry periods and the dominance of hillslope erosion processes. At the event scale, the hysteresis loops confirmed these seasonal patterns in transport dynamics. The calibration of the MUSLE model highlighted the severity of rainfall during the dry period. These results emphasize the importance of seasonality in erosion and transport processes with special relevance in terms of climate change predictions.  相似文献   

A workflow for Sustainable Development Goals indicators assessment based on high-resolution satellite data     

Nataliia Kussul  Andrii Kolotii  Sergii Skakun  Olena Rakoid  Leonid Shumilo 《International Journal of Digital Earth》2020,13(2):309-321

ABSTRACT

For evaluating the progresses towards achieving the Sustainable Development Goals (SDGs), a global indicator framework was developed by the UN Inter-Agency and Expert Group on Sustainable Development Goals Indicators. In this paper, we propose an improved methodology and a set of workflows for calculating SDGs indicators. The main improvements consist of using moderate and high spatial resolution satellite data and state-of-the-art deep learning methodology for land cover classification and for assessing land productivity. Within the European Network for Observing our Changing Planet (ERA-PLANET), three SDGs indicators are calculated. In this research, harmonized Landsat and Sentinel-2 data are analyzed and used for land productivity analysis and yield assessment, as well as Landsat 8, Sentinel-2 and Sentinel-1 time series are utilized for crop mapping. We calculate for the whole territory of Ukraine SDG indicators: 15.1.1 – ‘Forest area as proportion of total land area’; 15.3.1 – ‘Proportion of land that is degraded over total land area’; and 2.4.1 – ‘Proportion of agricultural area under productive and sustainable agriculture’. Workflows for calculating these indicators were implemented in a Virtual Laboratory Platform. We conclude that newly available high-resolution remote sensing products can significantly improve our capacity to assess several SDGs indicators through dedicated workflows.  相似文献   

流域物质与水系及产沙间非线性关系实验研究   总被引：7，自引：0，他引：7  

金德生  陈浩  郭庆伍 《地理学报》2000,55(4):439-448

在３５．５６ｍｍ／ｈ．ｃｍ＾２定雨强的人工降雨条件下,组成物质中径分别为０．０２１ｍｍ、０．０６６ｍｍ及０．０７６ｍｍ的发育对比实验表明,产沙过程具有波动振荡衰减特征;水系发育以增加河道（沟道）数目及弯曲拉伸长度两种方式进行最小消能。水系分形维数正是这种消能的量度。水系分数维值随时间呈不对称上凹型曲线。对比分析表明：产沙过程的振荡性、衰减率,随物质变粗而加强,水系河道数目随物质变细而增多,河道随物  相似文献   

SEDIMENT YIELD AND HYDROLOGY IN NORTHWESTERN RANGELANDS     

Charles W. Slaughter 《国际泥沙研究》2000,(2)

lINTRODUCTIONRangeandforestlandsofnorthwesternNorthAmericahavebeenutilizedforres0urceextracti0nandproductionsinceinitialhuman0ccupationofthecontinent.Intensive"managed"utilizati0nofec0systemsforspecificbenefitsincludingcattle,sheep,t1sh,w00dandagriculturalpr0ductshasbeenong0ingfornearly0ne-and-haIfcenturies.Intensiveresourceproducti0nhasto0oftenbeenacc0mpaniedbyunwanted"sideeffects"includingacceleratederosion,s0illossandsedimentdeliveredoffsitetod0wnstreamlocati0ns,estuariesandoceanicsin…  相似文献   

Model study of the relationship between sediment yield and river basin area     

S. J. Birkinshaw  J. C. Bathurst 《地球表面变化过程与地形》2006,31(6):750-761

The SHETRAN physically based, spatially distributed model is used to investigate the scaling relationship linking specific sediment yield to river basin area, for two contrasting topographies of upland and more homogeneous terrain and as a function of sediment source, land use and rainfall distribution. Modelling enables the effects of the controls to be examined on a systematic basis, while avoiding the difficulties associated with the use of field data (which include limited data, lack of measurements for nested basins and inability to isolate the effects of individual controls). Conventionally sediment yield is held to decrease as basin area increases, as the river network becomes more remote from the headwater sediment sources (an inverse relationship). However, recent studies have reported the opposite variation, depending on the river basin characteristics. The simulation results are consistent with these studies. If the sediment is supplied solely from hillslope erosion (no channel bank erosion) then, with uniform land use, sediment yield either decreases or is constant as area increases. The downstream decrease is accentuated if rainfall (and thence erosion) is higher in the headwaters than at lower elevations. Introducing a non‐uniform land use (e.g. forest at higher elevations, wheat at lower elevations) can reverse the trend, so that sediment yield increases downstream. If the sediment is supplied solely from bank erosion (no hillslope erosion), the sediment yield increases downstream for all conditions. The sediment yield/basin area relationship can thus be inverse or direct, depending on basin characteristics. There still remains, therefore, considerable scope for defining a universal scaling law for sediment yield. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Response of canopy quantum yield of alpine meadow to temperature under low atmospheric pressure on Tibetan Plateau     

《中国科学D辑(英文版)》2006,(Z2)

An open-path eddy covariance system was set up in Damxung rangeland station to measure the carbon flux from July to October, 2003. The canopy quantum yield (α) of alpine meadow was calculated by the linear function between the net ecosystem carbon dioxide exchange (NEE) and the photosynthetic active radiation (PAR) under low light, and how it was influenced by the temperature was also discussed. Results showed that the canopy or decreased almost linearly with temperature, with the decrease in every 1℃increase of temperature similar to those measured on leaf level of C3 plant. At the beginning, the decrease of canopyαwith temperature was 0.0005 umol CO2·μmol-1 PAR; while it increased to 0.0008μmol CO2·μmol-1 PAR in September, showing a rising trend with plant growing stages. Compared with the canopy a calculated with rectangular hyperbola function, the value in the paper was lower. However, the method advanced here has the advantages in examining the relationship betweenαand the key environmental factors, such as temperature.  相似文献   

流域水文模型研究进展   总被引：7，自引：0，他引：7  

石教智  陈晓宏 《水文》2006,26(1):18-23

本文介绍了流域水文模型的分类,论述了流域水文模型基础理论——产汇流理论的发展及其自身的研究进展,探讨了流域水文模型的研究趋势和发展困境,并对未来做出了展望,以期能推进流域水文模型的研究。  相似文献   

生态足迹分析的资源产量法研究     

谢鸿宇  刘年丰  姚瑞珍  宋巍巍 《武汉大学学报(信息科学版)》2006,31(11):1018-1021

提出以资源生产量作为生态足迹分析中生态容量计算依据的资源产量法。该方法更全面地考虑了林地、可耕地、水域等具有的多重生态生产性功能，扩大了生态容量的内涵，将可再生能源、可回收利用废物等作为生态容量的供给，使生态容量与生态足迹的计算依据更为协调。以湖北省襄樊市2001年的生态容量计算为实例，说明了资源产量法的合理性。  相似文献