海南省农业结构调整对农业经济发展的实证分析

通过Pearson相关系数值以及建立回归模型2种方式分别对农业经济增长的关系进行分析。结果表明,海南省农业（种植业）与农业经济增长并无明显的相关性;林业比重与农业经济增长有显著的负相关关系;牧业、渔业比重与农业经济增长有显著的正相关关系。2008年海南省的农业产业结构与1990年农业产业结构相似系数为0.93,说明在1991～2008年期间的海南省农业结构调整对其农业经济发展有很大的贡献。     

基于PCCs-DEMATEL指标筛选的BP神经网络用水量预测

以面向决策支持的用水量趋势预测为研究目标,采用从定性到定量的综合集成方法,将各指标变化率作为处理单元,运用PCCs-DEMATEL(皮尔逊相关系数-决策试验评估)方法对统计指标筛选,以BP神经网络构建预测模型,与赋权指数平滑法预测模型进行比较分析。模型在广州市的运用实例表明,基于PCCs-DEMATEL指标筛选的BP神经网络用水量预测模型可以更好地预测以年为单位的地区用水量,为水资源决策分析提供可靠的数据支撑。     

Soil carbon dioxide and nitrous oxide emissions during the growing season from temperate maize‐soybean intercrops

The Argentine Pampa is one of the major global regions for the production of maize (Zea mays L.) and soybean (Glycine max L. [Merr.]), but intense management practices have led to soil degradation and amplified greenhouse‐gas (GHG) emissions. This paper presents preliminary data on the effect of maize‐soybean intercrops compared with maize and soybean sole crops on the short‐term emission rates of CO₂ and N₂O and its relationship to soil moisture or temperature over two field seasons. Soil organic carbon (SOC) concentrations were significantly greater (p < 0.05) in the maize sole crop and intercrops, whereas soil bulk density was significantly lower in the intercrops. Soil CO₂ emission rates were significantly greater in the maize sole crop but did not differ significantly for N₂O emissions. Over two field seasons, both trace gases showed a general trend of greater emission rates in the maize sole crop followed by the soybean sole crop and were lowest in the intercrops. Linear regression between soil GHG (CO₂ and N₂O) emission rates and soil temperature or volumetric soil moisture were not significant except in the 1:2 intercrop where a significant relationship was observed between N₂O emissions and soil temperature in the first field season and between N₂O and volumetric soil moisture in the second field season. Our results demonstrated that intercropping in the Argentine Pampa may be a more sustainable agroecosystem land‐management practice with respect to GHG emissions.     

The effects of carotenoids in quail breeder diets on egg yolk pigmentation and breeder performance

The effects of supplementation of 10?mg/kg (i) apoester, (ii) canthaxanthin, (iii) 3% clover extract, (iv) paprika oleoresin and (v) aztec marigold extract pigments to a wheat-based non-pigmented feed on hatchery performance and egg yolk pigmentation in quail breeders were investigated. At six weeks of age a total of 432 Japanese quail breeders were randomly divided into 6 treatments, each of which was replicated 3 times, with 24 birds (18 female:6 male) per replicate. Hatchability was significantly better in the apoester treatment compared to the control, canthaxanthin, clover extract and paprika oleoresin treatments (p?p?>?.05). Total carotenoids concentration, YCF score, yellowness (b*) and redness (a*) of egg yolk were significantly higher in pigment-supplemented treatments compared to the control treatment (p?a*) were highly correlated in all treatments (0.94; p?相似文献   

新疆天山北坡3种地表植被指数检测方法与监测

应用3种地表植被检测方法计算了2000—2004年间新疆北部地区植被的变化状况,总结了计算结果的相关特征。综合统计结果显示,5a来植被生长状况总体要好于前8a(1991—1999年);但中、高山带的林地和乌鲁木齐—石河子绿洲上的农用地都发生了不同程度、高比例、大面积的退化,只有很小比例的植被得以改善,表现出局部恶化,总体改善的局面。     

林木直径分布的研究——Ⅱ.极大似然估计

本文在拟合直径分布时对给定的样本资料按判别准则来选择总体分布类型的方法取得了满意的结果。对所讨论的7种分布,给出了参数的极大似然估计,比较了不同的分布类型及不同估计方法的拟合效果。     

Peak functions for modeling high resolution soil profile data

Parametric and non-parametric depth functions have been used to estimate continuous soil profile properties. However, some soil properties, such as those seen in weathered loess, have anisotropic peak-shaped depth distributions. These distributions are poorly handled by common parametric functions. And while nonparametric functions can handle this data they lack meaningful parameters to describe physical phenomena in the depth distribution of a property such as a peak, an inflection point, or a gradient. The objective of this work is to introduce the use of asymmetric peak functions to model complex and anisotropic soil property depth profiles. These functions have the advantages of providing parameters, which quantify or describe pedogenic processes. We demonstrate the application of the Pearson Type IV (PIV) and the logistic power peak (LPP) functions to high resolution soil property depth profiles measured by diffuse reflectance spectroscopy in a claypan soil landscape of Northeastern Missouri, USA. Both peak functions successfully fit clay, silt, and pH data for an example soil profile from a summit landscape position (R² = 0.90 for pH and 0.98 for silt and clay). The LPP function was further demonstrated to fit clay depth distribution for a shoulder, backslope, footslope, and a depositional landscape position (R² = 0.98, 0.96, 0.96, 0.91). Relationships between the fitted parameters of these profiles were useful to describe landscape trends in their morphological features and show promise to continuously describe pedogenic processes in three dimensions. Peak functions are a useful companion to high-resolution soil profile data collected by sensors and their combined use may allow more intensive mapping and better explanation of soil landscape variability.     

砂壤质褐土饱和导水率与物理性质的多尺度关系——小波分析法

正确估算土壤水力特性是准确了解土壤水分运动和溶质运移过程的前提。土壤水力特性具有明显的空间变异特征,由于其空间异质性是各种物理、化学和生物过程(如生物活动、耕作、地形、土壤侵蚀)在不同尺度下综合作用的产物,导致其变异     

林木直径分布预测动态模型的研究

林木直径分布及其变化规律的研究,至今并未很好解决。本文对单一林分总体提出一套对直径分布一致性和非一致性林分具有兼容性的模型,将有助问题的解决。一、分布预测模型的构造 (一)分布函数的选择和参数估计 1.分布函数的选择本文采用K.Pearson分布系来描述直径分布,所选6种分布函数详见表1。其中,x是随机变量,a、b、c、p和q是参数。且     

闽北天然针阔混交林优势乔木树种间协变研究

采用Pearson积矩系数、Spearman秩相关系数和方差分析，对闽北天然针阔混交林15个优势乔木树种间的协变进行了研究．结果表明，除甜槠与木荷、苦槠与冬青、润楠与米槠间表现出显著的正协变，马尾松与栲树、木荷和若槠、锥粟间表现出显著负协变外，多数种群间的协变不显著，趋于各自独立．这反映出闽北天然针阔混交林群落的不稳定性．研究结果对混交林树种配置和抚育管理都具有理论指导作用．