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101.
Hyperspectral remote sensing research was conducted to document the biophysical and biochemical characteristics of controlled forest plots subjected to various nutrient and irrigation treatments. The experimental plots were located on the Savannah River Site near Aiken, SC. AISA hyperspectral imagery were analysed using three approaches, including: (1) normalized difference vegetation index based simple linear regression (NSLR), (2) partial least squares regression (PLSR) and (3) machine-learning regression trees (MLRT) to predict the biophysical and biochemical characteristics of the crops (leaf area index, stem biomass and five leaf nutrients concentrations). The calibration and cross-validation results were compared between the three techniques. The PLSR approach generally resulted in good predictive performance. The MLRT approach appeared to be a useful method to predict characteristics in a complex environment (i.e. many tree species and numerous fertilization and/or irrigation treatments) due to its powerful adaptability. 相似文献
102.
103.
Effects of Crop Growth and Development on Land Surface Fluxes 总被引:2,自引:0,他引:2
In this study, the Crop Estimation through Resource and Environment Synthesis model (CERES3.0) was coupled into the Biosphere-Atmosphere Transfer Scheme (BATS), which is called BATS CERES, to represent interactions between the land surface and crop growth processes. The effects of crop growth and development on land surface processes were then studied based on numerical simulations using the land surface models. Six sensitivity experiments by BATS show that the land surface fluxes underwent substantial changes when the leaf area index was changed from 0 to 6 m2 m-2. Numerical experiments for Yucheng and Taoyuan stations reveal that the coupled model could capture not only the responses of crop growth and development to environmental conditions, but also the feedbacks to land surface processes. For quantitative evaluation of the effects of crop growth and development on surface fluxes in China, two numerical experiments were conducted over continental China: one by BATS CERES and one by the original BATS. Comparison of the two runs shows decreases of leaf area index and fractional vegetation cover when incorporating dynamic crops in land surface simulation, which lead to less canopy interception, vegetation transpiration, total evapotranspiration, top soil moisture, and more soil evaporation, surface runoff, and root zone soil moisture. These changes are accompanied by decreasing latent heat flux and increasing sensible heat flux in the cropland region. In addition, the comparison between the simulations and observations proved that incorporating the crop growth and development process into the land surface model could reduce the systematic biases of the simulated leaf area index and top soil moisture, hence improve the simulation of land surface fluxes. 相似文献
104.
Assessing adaptability of planted trees using leaf traits: A case study with Robinia pseudoacacia L. in the Loess Plateau, China 总被引:1,自引:0,他引:1
Leaf trait patterns and their variations with climate are interpreted as an adaptive adjustment to environment.This study assessed the adaptability of planted black locust (Robinia pseudoacacia L.) based on the analysis of leaf traits and the comparison of its leaf traits with inter-specific ones existing in the same area.We measured some water and N use related leaf traits: leaf dry mass per unit area (LMA) and N,P and K concentrations based on both leaf area (Narea,Parea and Karea) and leaf mass (Nmass,Pm... 相似文献
105.
地磁导航作为一种新的无源导航方式,具有重要的国防意义.构建空间地磁数据库是实现地磁导航的基础,位场延拓是解决地磁数据库构建的有效方法.积分-迭代法是一种解决位场大深度向下延拓的实用方法.本文着重对积分-迭代法的收敛性进行了分析,从数学角度证明积分-迭代法能够收敛到直接下延法理论解.同时对积分-迭代法的抗干扰性进行了初步分析,当观测数据含有噪声时,积分-迭代过程中使得噪声得到累加,影响延拓数据的精度.本文利用正则化方法和递增型维纳滤波方法,提出了波数域位场向下延拓新算法.模型检验表明,新算法稳定、抗干扰能力强、计算速度快. 相似文献
106.
107.
The study developed an integrated reflectance model combining radiative transfer and geometric optical properties in order
to inverse leaf area index (LAI) of semiarid natural grasslands. In order to better link remote sensing information with land
plants, and facilitate regional and global climate change studies, the model introduced a simple but important geometrical
similarity parameter related to plant crown shapes. The model revealed the influences of different plant crown shapes (such
as spherical, cylindrical/cuboidal and conic crowns) on leaf/branch angle distribution frequencies, shadow ground coverage,
shadowed or sunlit background fractions, canopy reflectance, and scene reflectance. The modeled reflectance data agreed with
the measured ones in the three Leymus chinensis steppes with different degradation degrees, which validated the reflectance model. The lower the degradation degree was,
the better the modeled data agreed with the measured data. After this reflectance model was coupled with the optimization
inversion method, LAI over the entire study region was estimated once every eight days using the eight-day products of surface
reflectance obtained by multi-spectral Moderate-Resolution Imaging Spectroradiometer (MODIS) during the growing seasons in
2002. The temporal and spatial patterns of inversed LAI for the steppes with different cover degrees, swamps, flood plains,
and croplands agreed with the general laws and measurements very well. But for unused land cover types (sands, saline, and
barren lands) and forestlands, totally accounting for about 10% of the study region, the reasonable LAI values were not derived
by inversing, requiring further revising of the model or the development of a new model for them.
Supported by the National Natural Science Foundation of China (Grant No. 30500076), the National Basic Research Program of
China (Grant No. 2007CB714407), and the President Foundation of Graduate University of Chinese Academy of Sciences (Grant
No. YZJJ200205) 相似文献
108.
A class of El Nino atmospheric physics oscillation model is considered. The El Nino atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions. The conceptual oscillator model should consider the variations of both the eastern and westem Pacific anomaly patterns. An El Nino atmospheric physics model is proposed using a method for the variational iteration theory. Using the variational iteration method, the approximate expansions of the solution of corresponding problem are constructed. That is, firstly, introducing a set of functional and accounting their variationals, the Lagrange multiplicators are counted, and then the variational iteration is defined, finally, the approximate solution is obtained. From approximate expansions of the solution, the zonal sea surface temperature anomaly in the equatorial eastern Pacific and the thermocline depth anomaly of the seaair oscillation for El Nino atmospheric physics model can be analyzed. El Nino is a very complicated natural phenomenon. Hence basic models need to be reduced for the sea-air oscillator and are solved. The variational iteration is a simple and valid approximate method. 相似文献
109.
负摩擦作用下PCC桩沉降计算 总被引:3,自引:0,他引:3
从桩-土相互作用的机制出发,建立了均质地基中PCC桩负摩阻力传递的弹性微分方程。提出了基于有限差分法的一种桩身位移的迭代算法,计算结果表明,该计算方法收敛性好,且符合实际情况。根据中性点定义得出其位置在桩身中下部,与以往的研究结果相吻合。结果还表明,PCC桩比等截面的实心桩有较小的沉降。 相似文献
110.
叶片化学组分成像光谱遥感探测机理分析 总被引:69,自引:5,他引:64
利用地面光谱仪的测量数据 ,进行了成像光谱遥感探测叶片化学组分的机理性研究。采用多元逐步回归方法 ,分析了鲜叶片 7种化学组分含量与其光谱特性的统计关系 ,分别建立了反射率 ρ及其变化式 1/ρ、logρ和ρ的一阶导数Kρ 与化学组分含量的统计方程 ,并对这 4个指标的性能进行了比较和评价。结果表明 ,在 95 %的置信水平下 ,可以由叶片的精细光谱特征较好地反映出化学组分含量 ;特别是利用Kρ 作为因子 ,使置信水平提高到 99% ,尤以对粗蛋白质、N、K含量反映最好 ,R2 均达到 0 8以上 ,粗蛋白质可达 0 95 6 4,从而为进一步探讨在中国利用成像光谱遥感探测叶片化学组分奠定了基础 相似文献