多参数冬小麦估产模型研究及产量影响因素分析   总被引：1，自引：0，他引：1  

赵亚光  张粲  候璠  张喜旺 《中国农学通报》2015,31(29):241-247

产量估算研究对制定粮食政策和经济计划,科学地进行粮食宏观调控有着重要意义。针对以往线性遥感估产模型中多是基于NDVI和LAI的研究,且参数间存在多重共线性等问题,该研究以河北省南部石家庄、保定、邯郸、邢台、衡水、沧州六市为研究区,选用2000—2008 年的种植区最佳时相NDVI、LAI累加值,并引入与小麦生物量积累密切相关的不同月份地表温度作为原始估产指标,针对参数累加值存在的误差,提出一个修正公式对NDVI、LAI 进行修正,再对选用参数进行主成分分析,将结果与冬小麦产量数据建立出4 个多参数综合作用的冬小麦遥感估产模型。结果表明,利用2009 年数据对模型进行验证,结果表明4 个模型的R2介于0.714~0.818 之间,估产精度均在93.0%以上,其中,综合所有遥感参数的模型拟合效果最好,R2为0.818,估产精度达95%,而且引入温差主成分的模型精度高于仅用NDVI、LAI作参数的模型,另外深入分析各参数对产量估测的影响可知4 月中旬和5 月中旬的地表昼夜温差对冬小麦的后期产量具有较大影响。  相似文献   

太行山南麓气象灾害风险区划——以河南省卫辉市为例          下载免费PDF全文

田晓璐 《农学学报》2017,7(2):42-47

为充分了解卫辉市气象灾害的时空分布特征,揭示太行山南麓复杂地形与气象灾害分布间的关系,选取卫辉市1961—2014年各乡镇灾情、DEM、GDP、辖区内19个自动气象站的降水及风速数据等,利用层次分析法及主成分分析法构建冰雹、大风、暴雨和综合气象灾害风险评估指标体系,并依托ArcGIS绘制分辨率为30 m×30 m的灾害风险区划图。结果表明:卫辉市冰雹灾害风险较高的地区主要分布在2条冰雹移动路径上;大风灾害风险分布较分散,除狮豹头、汲水镇、后河镇、李源屯镇之外的乡镇均偏高;暴雨灾害风险集中在卫河、共产主义渠附近;安都、顿坊店、上乐村镇、孙杏村镇的综合气象灾害风险较高。该研究可以提高当地气象服务的针对性和指导性,为制订防灾减灾措施提供科学依据。  相似文献   

Soil quality assessment under shifting cultivation and forests in Northeastern Himalaya of India     

Gaurav Mishra  Rossana Marzaioli  Krishna Giri  Rinkumoni Borah  Antara Dutta  R.S.C. Jayaraj 《Archives of Agronomy and Soil Science》2017,63(10):1355-1368

The study aimed to evaluate the impact of shifting cultivation on soil quality, in Wokha district of Nagaland, using weighted soil quality index (SQIw). Four forest sites and three sites under shifting cultivation were selected and physical (texture and bulk density) and chemical (pH, electrical conductivity, cation exchange capacity, organic carbon, available N, P, K, exchangeable cations) parameters were analyzed. The SQIw was calculated on a minimum data set selected by principal component analysis, followed by varimax rotation algorithm and through subsequent normalization of the parameters using the linear scoring function. Significant (P < 0.05) variations in SQIw were found across the depth of the soil and land use according to severity of factors associated with land use. Three different classes of soil quality were also identified: high quality (SQIw > 0.70) for two forest soils (FS1 and FS2) and land under shifting cultivation (JH1), low quality (SQIw < 0.50), only to FS3, and intermediate quality (0.50 < SQI < 0.70) in all other soils. The approach used in this study proved to be sensitive to evaluate the soil quality, however further research is required to better understand the sustainability of shifting cultivation by including more physical, biological and chemical indicators.  相似文献   

基于改进主成分分析和AdaBoost算法的运动虾苗识别方法   总被引：2，自引：2，他引：0  

刘世晶  王帅  陈军  刘兴国  周海燕 《农业工程学报》2017,33(1):212-218

针对虾行为量化过程中运动虾苗较难检测与识别的问题,该文以南美白对虾虾苗为例,提出了一种基于改进主成分分析(principal component analysis,PCA)+AdaBoost算法的运动虾苗自动识别方法。在室内自然光条件下,利用工业相机采集承装容器中虾苗的灰度图像。提取图像中大小为100×100像素的不同运动状态的虾苗图像,首先使用改进PCA算法进行主成分分析,并进行特征提取。根据特征参数的分布情况,对其进行归一化处理,利用归一化的特征构建多个弱分类器,利用Adaboost方法将弱分类器构建成强分类器。最后,利用强分类器对运动虾苗进行识别。试验结果表明,在150幅不同运动状态虾苗测试样本中,基于改进PCA+Adaboost方法的识别正确率98%,平均每个样本识别时间为0.027 898 s,满足行为量化中的自动识别要求。  相似文献   

Retention of native vegetation within the plantation matrix improves its conservation value for a generalist woodpecker     

Rafael Barrientos 《Forest Ecology and Management》2010

The suitability of plantation monocultures for the conservation of forest animals is an issue under continous debate. The adaptability of forest dwellers and the forest management regime seem to play key roles. In this study, I investigated the habitat selection of a generalist bird, the great spotted woodpecker (Dendrocopos major), within a pine (Pine spp.) monoculture, as well as the importance of the native habitat features within the pine matrix for the species’ conservation. I compared 52 plots with woodpecker presence against 121 plots where the species was absent, as well as 68 nest-trees against 90 random ones. Regression analyses were used to investigate the habitat attributes involved in the habitat selection. Although the great spotted woodpecker is considered a generalist forest dweller, it shows a marked habitat selection. Based on presence/absence records, the woodpecker prefers well-forested patches with high levels of tree diversity and with good coverage of a secondary species such as the strawberry tree (Arbutus unedo). To excavate their nests, woodpeckers select large trees in patches where other trees are also larger, rejecting patches with a high number of small trees. The most striking conclusion from this work is the preference shown for native trees, especially Portuguese oaks (Quercus faginea), as nest-trees. This is noteworthy because native trees are smaller and they are surrounded by smaller trees than pines. These findings support that woodpecker conservation benefits from an increase of habitat heterogeneity, particularly by the retention of native woodland patches within the plantation matrix.  相似文献   

Analysis of phenetic relationship between Citrus indica Tanaka and a few commercially important citrus species by ISSR markers     

Chibame K. Marak  M.A. Laskar 《Scientia Horticulturae》2010

Analysis of polymorphism in ISSR amplicons revealed diverse genetic relationship between Citrus indica and five other citrus species. In a consensus UPGMA dendrogram, based on Nei and Li's distance matrices, the C. indica samples from three different sites of Meghalaya, India were clustered together with 99% bootstrap support. C. reticulata, C. sinensis, C. aurantifolia formed a cluster with 67% bootstrap separation. C. macroptera and C. maxima samples from two sites of Meghalaya formed separate clusters with respectively 100% and 98% bootstrap supports. Principal Components Analysis projected C. indica to be more closely related to C. aurantifolia than to the other citrus species of the study. PCA also exposed variations within the C. maxima and C. macroptera samples.  相似文献   

基于主成分分析的叶面积指数尺度效应   总被引：1，自引：0，他引：1  

董莹莹  王纪华  李存军  杨贵军  徐新刚  王慧芳  黄文江 《农业工程学报》2012,28(11):164-169

为描述多空间尺度观测数据在表达同一区域农作物叶面积指数(LAI)分布特征时存在的差异,该文提出了一种基于主成分分析(PCA)的LAI尺度效应分析方法。该方法充分考虑了多尺度数据的相关性与差异性,从统计分析角度出发,采用PCA进行数据挖掘和信息重组,引入动态多元线性回归模式基于主成分信息(PCs)反演估算LAI,进而定量描述尺度效应。选取大麦和玉米为试验对象,先以地面最细空间尺度观测数据为基准,通过尺度上推构建一系列不同空间尺度数据;再依据上述尺度效应分析方法进行有效信息提取和LAI估算,并纳入有效主成分个数(NEPCs)、决定系数(R2)和平均相对精度(MRA)等参数定量描述尺度效应。理论分析和数值实践证实了该方法在农作物LAI尺度效应定量分析中的可行性和有效性。  相似文献   

Empirical modeling of spatial and temporal variation in warm season nocturnal air temperatures in two North Idaho mountain ranges, USA     

Zachary A. Holden  Michael A. CrimminsSamuel A. Cushman  Jeremy S. Littell 《Agricultural and Forest Meteorology》2011,151(3):261-269

Accurate, fine spatial resolution predictions of surface air temperatures are critical for understanding many hydrologic and ecological processes. This study examines the spatial and temporal variability in nocturnal air temperatures across a mountainous region of Northern Idaho. Principal components analysis (PCA) was applied to a network of 70 Hobo temperature loggers systematically distributed across 2 mountain ranges. Four interpretable modes of variability were observed in average nighttime temperatures among Hobo sites: (1) regional/synoptic; (2) topoclimatic; (3) land surface feedback; (4) canopy cover and vegetation. PC time series captured temporal variability in nighttime temperatures and showed strong relationships with regional air temperatures, sky conditions and atmospheric pressure. PC2 captured the topographic variation among temperatures. A cold air drainage index was created by predicting PC2 loadings to elevation, slope position and dissection indices. Nightly temperature maps were produced by applying PC time series back to the PC2 loading surface, revealing complex temporal and spatial variation in nighttime temperatures. Further development of both physically and empirically based daily temperature models that account for synoptic atmospheric controls on fine-scale temperature variability in mountain ecosystems are needed to guide future monitoring efforts aimed at assessing the impact of climate change.  相似文献   

Empirical downscaling of daily minimum air temperature at very fine resolutions in complex terrain     

Zachary A. Holden  John T. AbatzoglouCharles H. Luce  L. Scott Baggett 《Agricultural and Forest Meteorology》2011,151(8):1066-1073

Available air temperature models do not adequately account for the influence of terrain on nocturnal air temperatures. An empirical model for night time air temperatures was developed using a network of one hundred and forty inexpensive temperature sensors deployed across the Bitterroot National Forest, Montana. A principle component analysis (PCA) on minimum temperatures showed that 98% of the spatiotemporal variability could be accounted for using the first two modes which described the coupling and decoupling of surface temperature from free air temperatures, respectively. The spatial character of these modes were strongly correlated with terrain variables and were then modeled to topographic variables derived from a 30 m digital elevation model. PCA scores were modeled using independent predictors from in situ observations and regional reanalysis that incorporate temperature, solar radiation and relative humidity. By applying modeled PC scores back to predicted loading surfaces, nighttime minimum temperatures were predicted at fine spatial resolution (30 m) for novel locations across a broad (∼45,000 km²), topographically complex landscape. Our results suggest that this modeling approach can be used with retrospective and projected predictors to model fine scale temperature variation across time in regions of complex terrain.  相似文献   

青海省大黄中微量元素的主成分分析     

多杰扎西 《安徽农业科学》2007,35(26):8265-8266

用主成分分析法对青海省各地种植的大黄中的微量元素特征进行了研究,以微量元素Cu、Zn、Fe、Mn、Cr为评价指标,对其质量进行了综合评价。结果表明,青海省各地种植的大黄中的微量元素Zn、Mn、Fe对大黄的质量具有重要的作用和意义。  相似文献