Spectroscopy-Based Soil Organic Matter Estimation in Brown Forest Soil Areas of the Shandong Peninsula, China

Soil organic matter (SOM) is important for plant growth and production. Conventional analyses of SOM are expensive and time consuming. Hyperspectral remote sensing is an alternative approach for SOM estimation. In this study, the diffuse reflectance spectra of soil samples from Qixia City, the Shandong Peninsula, China, were measured with an ASD FieldSpec 3 portable object spectrometer (Analytical Spectral Devices Inc., Boulder, USA). Raw spectral reflectance data were transformed using four methods:nine points weighted moving average (NWMA), NWMA with first derivative (NWMA + FD), NWMA with standard normal variate (NWMA + SNV), and NWMA with min-max standardization (NWMA + MS). These data were analyzed and correlated with SOM content. The evaluation model was established using support vector machine regression (SVM) with sensitive wavelengths. The results showed that NWMA + FD was the best of the four pretreatment methods. The sensitive wavelengths based on NWMA + FD were 917, 991, 1 007, 1 996, and 2 267 nm. The SVM model established with the above-mentioned five sensitive wavelengths was significant (R²=0.875, root mean square error (RMSE)=0.107 g kg^-1 for calibration set; R²=0.853, RMSE=0.097 g kg^-1 for validation set). The results indicate that hyperspectral remote sensing can quickly and accurately predict SOM content in the brown forest soil areas of the Shandong Peninsula. This is a novel approach for rapid monitoring and accurate diagnosis of brown forest soil nutrients.     

农业综合产出对投入资源的敏感性研究

用弹性系数讨论农业产出对投入资源的敏感性和资源投入的合理性,采用加权TOPSIS法综合多种产出,分析安徽省农业资源利用情况。结果表明：从全省来看,农业综合产出对农药、从业人员和灌溉等资源投入的敏感性较高;2003、2005和2007年的资源投入不尽合理,而2004、2006和2008年的资源投入比较合理。从皖南山区来看,2002、2003、2005和2007年的资源投入不尽合理,2001、2004、2006和2008年的资源投入则比较合理。安徽省农业实践说明,适度减少投入仍有可能提高产出。     

基于综合灰色关联度加权法的玉米品种评价

【目的】利用综合灰色关联度加权法对玉米品种的各主要性状进行综合评价分析,为农作物新品种评价提供科学参考。【方法】采用2008年广西玉米区域试验数据,利用决策分析中的多属性决策理论,运用综合灰色关联度的方法确定各性状的客观权重,然后对玉米品种进行评价。【结果】玉米品种HM-2的综合评价值最大,其次是哈宝7号,最小的是XQ-9;玉米品种HM-13产量最高,其次为联玉19,产量最低的是KY116。【结论】在实际生产中,不能只考虑产量这一单一性状来选育新品种,应尽量选择对产量和环境的互作有影响的几个重要性状进行综合评价。综合灰色关联度加权法可有效减少某些人为的设定因素,使新品种的选育、评价和鉴定更科学、客观、符合实际。在玉米的育种实践工作中,其可作为辅助工具,以选育出高产、稳产、低风险、综合性状优良的玉米新品种。     

Modelling within‐field spatial variability of crop biomass – weed density relationships using geographically weighted regression

The objective of this study is to offer a new framework for exploring and modelling the spatial variation in crop biomass – weed density relationships, adapting geographically weighted regression (GWR) to include a non‐linear regression model. The relationship between crop biomass and weed density is usually modelled by non‐linear regression models, in which the spatial heterogeneity of the relationship is ignored, although the effect of weeds on crop can differ in relation to topographic and edaphic variability. GWR attempts to capture spatial variability by calibrating a regression model to each location in space. We show the application of the method in different cereal cropping systems, with one or two weed species. The results indicate that GWR can significantly improve model fitting over non‐linear least squares (NLS) in some situations. Furthermore, the parameter estimates can be mapped to illustrate local spatial variations in the regression relationship under study and eventually to relate the spatial variability of the model to the environmental heterogeneity. We discuss the value of the GWR for analysing the observed spatial variability and for improving model development and our understanding of spatial processes.     

Localization of growth estimates using non-parametric imputation methods

The purpose of this study was to examine different non-parametric imputation methods to reduce regional biases in growth estimates. Growth estimates were obtained using non-parametric k-nearest neighbour imputation (k-NN) to predict future 5-year diameter increment over bark at breast height for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies). The Mahalanobis distance function was chosen as the most suitable measure of similarity, and then it was modified using weights provided by linear regression analysis. The use of weights from linear regression facilitated the examination of the correlation structure of the variables and allowed for transformations of the independent variables. Localization of the non-parametric estimates was obtained through a variety of methods, in particular, by using spatial coordinates as independent variables, by restricting the selection of neighbours to a circular area around the target tree, and by restriction the selection of neighbours to a local database. The localized estimates using spatial measures were then compared with non-spatial imputation and also with estimates from a parametric growth model. Results were then compared by vegetation zones in Finland. The differences between the non-spatial k-NN estimates and the localized spatial estimates were negligible when summarized to the stand level, and localization did not reduce the regional biases relative to the non-spatial k-NN estimates. Regional biases in northern Finland and in south-western Finland were reduced substantially using the non-parametric estimates rather than the parametric growth models, however, and the mean biases in all of the regions were quite similar, while the mean biases of the growth estimates obtained with the parametric model varied notably between the regions.     

顶点赋权图分析法在沼气工程系统中的应用研究

利用顶点赋权反馈图分析法分析江苏某猪场沼气系统工程的效益,并建立猪场排泄物无污染的仿真学模型。根据2011年江苏某猪场与年猪粪尿和沼气效益有关的顶点赋权反馈图对其中的权值进行量化,采用量化结果和农户液化气消耗情况及耕地面积,建立猪场排泄物无污染的仿真学模型。结果表明：2011年该系统中含有3条正反馈环（沼气能源效益正反馈环、施肥面积正反馈环和沼渣效益正反馈环）及2条负反馈环（沼气浪费负反馈环和沼肥浪费负反馈环）。建立了两套排泄物无污染的仿真学模型的调整方案：一是在平均存栏量（1 728头）不变的情况下与168户农户建立输气管道,供农户使用;二是按比例扩大规模至3 721头,并建立与周边所有361户农户的输气管道,进一步健全沼液灌溉渠,扩大沼液灌溉面积。     

Normative considerations for recreational fishery management: a bioeconomic framework for linking positive science and normative fisheries policy decisions

Fishery science and management are concerned with both positive, what happens in a fishery system, and normative, what management should do, questions. Rarely are normative criteria discussed as openly and transparently as the positive techniques and assumptions. Instead, normative criteria are often held implicitly, and often goals, and objectives are defined without careful thought about the normative criteria from which such goals, and objectives derive. Management involves three components: system attributes and dynamics, management options and goals and objectives that stem from normative criteria by which outcomes are judged. There is a need to consider normative frameworks and criteria carefully because normative criteria are intrinsic to any management process. This paper motivates the need to consider normative frameworks and criteria carefully, explores issues associated with developing normative frameworks and criteria that articulate positive science, discusses specific issues to consider when developing normative frameworks for recreational fisheries and provides the bioeconomic framework as an example of a normative framework useful for recreational fisheries.     

Spatial and Temporal Dynamics of Stink Bugs in Southeastern Farmscapes

A 3-yr study (2009–2011) was conducted to examine the spatial and temporal dynamics of stink bugs in three commercial farmscapes. Study locations were replicated in South Carolina and Georgia, in an agriculturally diverse region known as the southeastern coastal plain. Crops included wheat, Triticum aestivum (L.), corn, Zea mays (L.), soybean, Glycine max (L.), cotton, Gossypium hirsutum (L.), and peanut, Arachis hypogaea (L.). Farmscapes were sampled weekly using whole-plant examinations for corn, with all other crops sampled using sweep nets. The predominant pest species of phytophagous stink bugs were the brown stink bug, Euschistus servus (Say), the green stink bug, Chinavia hilaris (Say), and the southern green stink bug, Nezara viridula (L.). Chi-square tests indicated a departure from a normal distribution in 77% of analyses of the variance to mean ratio, with 37% of slopes of Taylor’s power law and 30% of coefficient β of Iwao’s patchiness regression significantly greater than one, indicating aggregated distributions. Spatial Analyses by Distance IndicEs (SADIE) indicated aggregated patterns of stink bugs in 18% of year-end totals and 42% of weekly counts, with 80% of adults and nymphs positively associated using the SADIE association tool. Maximum stink bug densities in each crop occurred when the plants were producing fruit. Stink bugs exhibited greater densities in crops adjacent to soybean in Barnwell and Lee Counties compared with crops adjacent to corn or fallow areas. The diversity of crops and relatively small size of fields in the Southeast leads to colonization of patches within a farmscape. The ecological and management implications of the spatial and temporal distribution of stink bugs within farmscapes are discussed.     

圆锥空腔内涡破裂现象的数值模拟

采用三维非定常的Navier-Stokes方程对底面驱动的密闭圆锥室内旋转层流流动中的涡破裂现象进行了数值模拟,分析了雷诺数和几何结构对圆锥空腔内涡破裂现象的发展规律的影响.利用有限体积法离散控制方程和SIMPLE算法实施计算,计算网格采用非结构化网格.根据数值模拟结果得出了圆锥室内涡破裂现象的发展特性.研究结果表明:当达到一定雷诺数时,圆锥室内中心轴线附近会出现一个低压的涡破裂区域,并伴随着局部流体回流;在所研究的雷诺数范围内,随雷诺数的增加,涡破裂气泡的尺寸先增大后减小直至消失,涡破裂气泡的位置沿中心轴向远离驱动面的方向移动;对于相同高径比的圆锥室,涡破裂现象出现和消失时的临界位置不随圆锥室几何形状的变化而变化;由涡破裂现象出现时的临界雷诺数的大小可知,圆锥室模型相对于圆柱室模型抑制了涡破裂现象的产生,且顶面直径最大时的圆锥室(H_{1/H=0)的抑制效果最好.}     

基于条件植被温度指数的冬小麦主要生育时期干旱监测效果评价——Ⅱ.改进的层次分析法和变异系数法组合赋权

运用改进的层次分析法、变异系数法及主客观组合赋权法确定关中平原冬小麦越冬后主要生育时期干旱对产量的影响权重,建立关中平原五市2002—2009年每年的加权条件植被温度指数(VTCI)与冬小麦单产的一元线性回归模型,分析VTCI与产量间的线性关系。结果表明,变异系数法确定的加权VTCI与小麦单产的线性相关性不显著,渭南、咸阳及铜川的决定系数R²值均低于0.5;改进的层次分析法和组合赋权法确定的加权VTCI与小麦单产的线性相关性显著,除铜川外其余四市的R²值接近0.5,或者高于0.6,且组合赋权法的结果中西安的R²值达到0.7。基于改进的层次分析法和变异系数法的归一组合赋权法的结果优于其它 主客观组合赋权法的结果,为最优赋权方法,可用于评价冬小麦主要生育时期的干旱监测效果。