基于NDVI时间序列影像的张掖市农作物种植结构提取   总被引：1，自引：0，他引：1  

程良晓  江涛  谈明洪  肖兴媛 《地理信息世界》2016,(4):37-44

HJ卫星(环境与灾害监测预报小卫星)数据具有较高的时间和空间分辨率,可以有效地进行农作物种类识别,利用其时间序列数据进行作物信息提取具有很大优势。以甘肃省张掖市为研究区,利用2012年4月~2012年10月15个时相的HJ卫星CCD(电荷耦合元件,charge-coupled device)数据,通过分析玉米、油菜、大麦和小麦农作物在整个生长阶段的时间序列NDVI(归一化植被指数,normalized difference vegetation index)变化特点,提取四类农作物NDVI随时间变化的特征曲线,利用决策树分类方法,对2012年张掖市农作物进行分类,并以外业调查得到的实际地面验证点对分类结果进行验证。验证结果表明,可以有效地识别玉米、油菜、大麦和小麦4类农作物,制图精度分别为94.74%、82.35%、78.95%和90%;总体分类精度达到86.43%。而后提取了张掖市2014年农作物种植面积和分布格局,通过对比分析发现,2012~2014年,张掖市玉米、油菜的种植面积有不同程度的增加,大麦和小麦的种植面积各有一定程度的较少。可以为张掖市主要作物的种植结构调整提供科学依据,还可以为黑河流域农作物信息提取研究提供参考。  相似文献   

Exploring the potential of perennial crops in reducing soil erosion: A GIS-based scenario analysis in southern Tuscany,Italy     

《Applied geography (Sevenoaks, England)》2016

Preserving soils is a major challenge in ensuring sustainable agriculture for the future. Soil erosion by water is a critical issue in the Mediterranean regions and usually occurs when high-erosive precipitation is in temporal association with poor vegetation cover and density. Modelling soil erosion risks over large spatial scales suffers from the scarcity of accurate information on land cover, rainfall erosivity and their intra-annual dynamics. We estimated the soil erosion risk on arable land in a Mediterranean area (Grosseto Province, southern Tuscany, Italy) and investigated its potential reduction as a response to the change in intra-annual distribution of land cover due to the increase of perennial forage crops. A GIS-based (R)USLE model was employed and a scenario analysis was performed by setting criteria for raising the performance of perennial forage crops. Statistical data on agricultural crops provided an insight into current intra-annual land cover dynamics. Rainfall erosivity was computed on the basis of 22-year hourly precipitation data. The model was used to: i) quantify the potential soil losses of arable land in the study area, ii) identify those areas highly affected by erosion risks iii) explore the potential for soil conservation of perennial crops, thereby enabling appropriate preventive measures to be identified. The erosion rates, averaged over an area of about 140’000 ha, are estimated to 33.42 Mg ha⁻¹ y⁻¹. More than 59% of the study area was subjected to soil losses higher than 11 Mg ha⁻¹ y⁻¹ (from moderate to severe erosion) and the highest rates are estimated for steep inland areas. Arable land with severe soil erosion rates (higher than 33 Mg ha⁻¹ y⁻¹) represent about 35% of the whole study area. The risk of soil loss by water erosion in the study area is estimated to be reduced on average by 36% if perennial crops are increased in terms of 35% of the total arable land. The soil erosion data produced compared well with the published local and regional data. This study thus provides useful preliminary information for landscape planning authorities and can be used as a decision support tool in quantifying the implications of management policies.  相似文献   

Size fractionated biomass and productivity of phytoplankton and new production in the Prydz Bay and the adjacent Indian sector of the Southern Ocean during the austral summer 1998/1999     

Cai Yuming  Ning Xiuren  Zhu Genghai  Shi Junxian 《海洋学报(英文版)》2003,22(4):651-670

INTRODUCTIONComparedwithotheroceansintheworld ,thereisrelativelyhigherlevelofnutrients (ni trate ,phosphate ,silicate)intheSouthernOcean .Butprimaryproductivitiesarelow ,andnewproductionisalsoonlyinthemiddlelevelthere .Itiscommonlyconsideredthatthelowerpro ductivitiesintheSouthernOceaniscausedbylowtemperature ,lowlight,lowstabilityofwa ter,scarcityoftraceelementsuchasironandgrazingbyzooplankton (Burkilletal.,1 995) ,etc.ThemostexistedstudiesconcentratedontheAtlanticSectoroftheSouthernO…  相似文献   

通过训练样本采样处理改善小宗作物遥感识别精度   总被引：1，自引：0，他引：1  

樊东东  李强子  王红岩  张源  杜鑫  沈宇 《遥感学报》2019,23(4):730-742

训练样本质量是决定农作物遥感识别精度的关键因素,虽然高空间分辨率卫星的发展有效地解决了农作物遥感识别过程中的混合像元问题,但是当区域内不同作物种植面积差异较大时,训练集中不同类别样本数量往往相差较大,这样的不均衡数据集影响分类器的训练,导致少数类别的识别精度不理想。为研究作物遥感识别过程中的不均衡样本问题,本文基于GF-2号卫星数据,首先挖掘了地物的光谱信息、纹理信息,用特征递归消除RFE (Recursive Feature Elimination)方法进行特征优选,然后从数据处理的角度采用了5种采样算法对不均衡训练集进行处理,最后使用采样后的均衡数据集训练分类器,对比数据采样前后决策树与Adaboost(Adaptive Boosting)两种分类器的识别结果,发现:(1)经过采样处理后两种分类算法明显提升了小宗作物的分类精度;(2)经过ADASYS (Adaptive synthetic sampling)采样处理后,分类器性能提升最多,决策树的Kappa系数提高了14.32%,Adaboost的Kappa系数提高了10.23%,达到最高值0.9336;(3)过采样的处理效果优于欠采样,过采样对分类器的性能提升更多。综上所述,选择合适的采样方法和分类方法是提高不均衡数据集遥感分类精度的有效途径。  相似文献   

Hydraulic redistribution by deeply rooted grasses and its ecohydrologic implications in the southern Great Plains of North America     

Erik Oerter  Eric Slessarev  Ate Visser  Kyungjin Min  Megan Kan  Karis J. McFarlane  Malay C. Saha  Asmeret Asefaw Berhe  Jennifer Pett-Ridge  Erin Nuccio 《水文研究》2021,35(9):e14366

Perennial bioenergy crops with deep (>1 m) rooting systems, such as switchgrass (Panicum virgatum L.), are hypothesized to increase carbon storage in deep soil. Deeply rooted plants may also affect soil hydrology by accessing deep soil water for transpiration, which can affect soil water content and infiltration in deep soil layers, thereby affecting groundwater recharge. Using stable H and O isotope (δ²H and δ¹⁸O) and ³H values, we studied the soil water conditions at 20–30 cm intervals to depths of 2.4–3.6 m in paired fields of switchgrass and shallow rooted crops at three sites in the southern Great Plains of North America. We found that soil under switchgrass had consistently higher soil water content than nearby soil under shallow-rooted annual crops by a margin of 15%–100%. Soil water content and isotopic depth profiles indicated that hydraulic redistribution of deep soil water by switchgrass roots explained these observed soil water differences. To our knowledge, these are the first observations of hydraulic redistribution in deeply rooted grasses, and complement earlier observations of dynamic soil water fluxes under shallow-rooted grasses. Hydraulic redistribution by switchgrass may be a strategy for drought avoidance, wherein the plant may actively prevent water limitation. This raises the possibility that deeply rooted grasses may be used to passively subsidize soil water to more shallow-rooted species in inter-cropping arrangements.  相似文献   

河南省主要农作物虚拟水空间分布及水资源配置研究     

白景锋  杨杰 《地域研究与开发》2012,31(3):167-171

虚拟水是当今水科学的研究热点,被认为是解决粮食与水资源安全的重要策略。在计算河南省2009年3种主要农作物生物需水量的基础上,结合作物单产得到初级产品单位虚拟水含量,明晰了这3种主要农作物的"虚拟水"空间分布格局。研究结果表明:河南省3种主要农作物中,棉花的单位虚拟水含量最高,玉米最小。空间上小麦的单位耗水量在三门峡最高,漯河最低;玉米的单位耗水量在三门峡最高,许昌最低;棉花的单位耗水量在鹤壁最高,信阳最低;3种作物单位虚拟水含量从东南向西北增加,尤其在东西方向最明显,但是不同作物又有细微差别。中东部水资源短缺区应提高玉米和小麦的种植面积,丘陵和山前平原单位耕地地表水丰富区可种植虚拟水含量较高的作物。提供了从虚拟资源视角认识水资源消耗的实证,可以对河南省农作物布局提供科学依据。  相似文献   

1998-2008年中国农作物化肥消费的时空分异(英文)     

辛良杰  李秀彬  谈明洪 《地理学报(英文版)》2012,22(4):643-652

The agricultural and land policies in China are always focused on protecting its food supply and security because of the country’s large population and improved diets.The crop production guide ’Take Grain as the Key Link’ prompted peasants to plant grain on most of the agricultural land,leading to the majority of fertilizer being used in grain crops for many years in China.This situation has changed dramatically in recent years.Based on data pertaining to provincial crops sown area and fertilizer use per unit area in 1998 and 2008,the temporal and spatial variations of China’s fertilizer consumption by crops were analyzed at the provincial level,and the results are presented here.(1) Fertilizer consumption in China grew strongly in the last decade,while the growth was mainly attributable to the increase of fertilizer con-sumption by horticultural crops.The fertilizer consumption of grain crops dropped from 71.0% in 1998 to 57.8% in 2008.Thus,it is concluded that the emphasis of fertilizer consumption is shifting toward horticultural crops.(2) There were marked differences in the growth rates of fertilizer consumption from the regional point of view.The national average growth rate of fertilizer consumption was 31.9% during 1998-2008.The western and northeastern parts of the country came close to the national average,while the eastern part was lower,with an average of 13.0%,and central China was much higher(50.8%).The increase of fertilizer consumption in central and west China was higher than the other zones,which already ac-counted for 77.9% of the national total.Thus,it is concluded that the consumption emphasis of chemical fertilizer shifts toward the central and western regions.(3) The decline of fertilizer consumption by grain crops was largely due to the decrease in sown area compared with the increase by vegetable crops attributable to the enlarging sown area;the increase by orchard crops was affected by both expanding the sown area and fertilizer use per unit area.  相似文献   

土壤干旱对作物生长过程和产量影响的研究进展   总被引：3，自引：0，他引：3  

赵鸿  李凤民  熊友才  王润元  杨启国  邓振镛 《干旱气象》2008,26(3):67-71

水分短缺是作物生长中最大的限制因子,土壤干旱胁迫使植物的长势、生理机制、激素水平等都会发生一系列变化。在干旱半干旱地区,土壤水分亏缺能明显抑制作物根系和地上部生长,显著降低作物的生物量、产量和收获指数。禾谷类作物小麦（Triticum aestivum）在灌浆期遇到水分胁迫时,会引起光合速率降低、灌浆时间缩短、灌浆速率下降、植株老化提前,但是它能增加营养组织到籽粒中非结构性碳水化合物的再代谢。土壤水分和植物激素共同调控作物的灌浆过程,当遇到土壤干旱时,作物叶片、花、籽粒发育过程中植物生长调节剂ABA浓度明显增加,且ABA、乙烯、ACC等的浓度随着干旱程度而变化。植物对干旱的适应性主要表现在植物生理、形态上的改变,比如植株结构、干物质积累、植物组织渗透势、气孔导度等的变化。土壤干旱不利于植物生长,但有利于胁迫临界点的产生,这就有可能利用土壤干旱条件下在灌浆较慢时诱导整个植株衰老和更好地进行碳代谢来提高籽粒产量,如果在作物灌浆后期适度控制土壤干旱可以增加籽粒产量和收获指数,有助于农业生产中的节水,这对于发展可持续农业是迫切需要的。  相似文献   

浒苔纤维吸声的测评研究     

傅圣雪  么光  冯遵成  李钢  王欢  郭克涛 《中国海洋大学学报(自然科学版)》2009,39(2)

采用驻波管法对不同厚度、不同结构的浒苔样品进行吸声系数的测定,并与相近的有机和无机纤维吸声材料进行了对比.试验结果表明,浒苔具有很好的吸声性能,并且其微管结构对吸声性能的提高有较大的贡献.这些新的发现将给研制新型无机纤维吸声材料提供有益的仿声学启示.  相似文献   

Wave Run-up on A Vertical Seawall Protected by An Offshore Submerged Barrier     

张景新  刘桦 《中国海洋工程》2009,23(3):553-564

Submerged barriers are constructed in coastal zones for shoreline or harbor protection or to prevent the beach erosion. In the present study, the wave run-up on a vertical seawall protected by a submerged barrier is analyzed. The physical configurations include a rigid barrier and a long channel of finite depth. For linear water waves, by matching the velocity along the barrier and along the gap, the systems of linear equations about the velocity potentials are obtained. The wave run-up is further analyzed ...  相似文献