ENSO classification indices and summer crop yields in the Southeastern USA

This research uses a quantitative methodology for directly comparing the responses of observed crop yields in the SE USA to ENSO phenomena classified using dissimilar ENSO indices. ENSO condition has been related to agricultural yields in many parts of the world. It has been generally recognized that the strongest effects on spring and summer crops occur during the boreal winter, and therefore most directly affect spring-summer field crops in the southern hemisphere. However, some ENSO effects on northern hemisphere spring and summer crops have been found, particularly when researchers have used sub-annual indicators of ENSO conditions that, unlike annual ENSO indices, distinguish between continuity and change prior to or during the crop season. To evaluate the utility of such sub-annual ENSO indicators for agriculture in the SE USA, a tercile-based scoring system was devised to compare four distinct ENSO indices: three monthly ENSO indices and the JMA annual ENSO index. Each index was scored in its ability to predict crop yields differing from the historically normal tercile for corn (Zea mays L.), cotton (Gossypiumhirsutum L.), and peanut (Arachis hypogaea L.). Annual crop yield data were used from selected counties in five Southeastern USA states. No geographic differentiation among the data was included in the analysis. This aggregation of county data increased the sample size for each crop, to address the limitation of a short time-series (47 years) distributed among up to 9 ENSO categories. Statistical significance was compared using contingency tables and the Fisher exact test. Peanut and corn yield response matched best to the Multivariate ENSO Index (MEI) and cotton, to the Oceanic Niño Index (ONI). The MEI and ONI are quantitative indices, while the lower-scoring JMA and Modified-JMA indices are categorical. Therefore, future efforts may reduce the focus on categorical (Niño, Niña, Neutral) classification, and explore the response of crop yields to quantitative ENSO data.     

Use of multivariate analysis to assess phenotypic diversity of date palm (Phoenix dactylifera L.) cultivars

Twenty one date palm (Phoenix dactylifera L.) accessions originated from different date palm groves were studied to assess the overall degree of polymorphism, detect similarities between genotypes and assess important agronomic traits. Thirty vegetative and reproductive variables were scored and subjected to multivariate analysis. Results showed a considerable phenotypic diversity among local date palm germplasm. Principal component analysis (PCA) revealed that characters related to leaflets length and spine, fruit and seed sizes accounted for a large proportion of the observed variability. Cluster analysis (CA) showed a typically continuous phenotypic diversity among date palm accessions and little associations between accessions from same geographic origin. Also, some heterogeneity within accessions that received the same denomination was evidenced.     

试论市场网络在县域经济发展中的作用──满城县农村市场网络的调查分析

伴随着商品生产的发展，在经济发展内部机制的推动下，农村、山区出现了林果专业市场。并以自然市场──规范市场──网络市场为序发生着升华、演变，最终在县域经济整体中，形成市场网络。这种市场网络对县域经济会产生显著的拉动效应。作为服务于农村经济的市场网络，其建设目标应该包括产业目标、绿色目标、小城镇建设目标。     

灌溉经济效益模拟计算及群决策优选灌溉方案

在对灌溉效益特点进行分析的基础上，指出灌溉方案决策中存在两种不确定性，即随机不确定性和模糊不确定性。并针对灌溉方案决策的这一特点，使用模拟方法，以经济净现值为指标对研究区的农业灌溉方案的经济效益进行模拟求解；使用群决策的方法对灌溉方案进行多人多目标决策，将个人的偏好集结成群体的偏好，避免各决策者因知识结构等因素的不同，做出不符合实际的决策。研究结果表明：该模型简单、通用，基于此模型做出的决策更符合实际。     

咸海中下游流域水质空间分布特征及其与土地覆被的关系

中亚咸海流域的资源和环境问题一直是全球关注的热点。为揭示咸海流域水环境变化及其成因,本文利用2019年中下游流域21个采样点水质数据,通过主成分、聚类和秩次等多元统计分析方法相结合,分析了水体的基础理化属性、氮磷营养元素、其他元素和离子等20种指标的空间分布特征,辨识了该流域主要水质类型、空间分布及成因,探索了不同空间尺度土地覆被类型对水质类型的影响。结果表明:1)电导率、总溶解性固体物质和离子浓度越往河流下游数值越高,其中在咸海最大;不同形态磷元素浓度在阿姆河中游较高,硝态氮浓度在锡尔河较高;碳元素浓度也在阿姆河,特别是阿姆河下游三角洲地区较高。2)所有采样点水体根据水质指标相似性聚类可划分为3种综合性水质类型。第1类型为水质指标浓度均偏低的水体,分布在锡尔河中游和咸海;第2类型为氮磷营养元素浓度偏高的水体,分布在阿姆河中下游;第3类为碳元素和离子浓度均偏高的水体,分布在咸海。第1和2类型水体的元素浓度主要受荒漠地区岩石风化过程控制,阴阳离子来源于硅酸盐岩和蒸发岩的风化;第3类型水体主要受气候干燥导致的蒸发-结晶过程控制,阴阳离子除来源于硅酸盐岩和蒸发岩的风化外,还受碳酸盐岩风化影响。3)当各采样点缓冲区半径从0.5 km增加到10 km时,对第1类型水质浓度变化影响显著的土地覆被类型逐渐从荒地变为水域、灌木、草地和农田与植被混合,其中水域的影响最大;第2类型水质浓度变化与土地覆被类型无显著性关系;对第3类型水质浓度变化影响显著的土地覆被类型从水域变为水域、农田与植被混合等,其中水域的影响最大。因此,咸海流域水质浓度变化与当地干旱缺水和蒸发剧烈等气象条件以及土地覆被类型有密切关系。为改善咸海中下游流域水环境状况,在增加中下游河道流量和咸海的补给,减弱下游和咸海蒸发-结晶作用的同时,还需加大河岸带的植被修复和退耕还林还草,特别是在阿姆河和锡尔河中下游农业区、咸海等地区。     

电子鼻在芒果采后病原菌种类判别中的应用研究

利用电子鼻对胶孢炭疽菌(Colletotrichum gloeosporioides Penz.)、可可球二孢(Botryodiplodia theobromae Pat.)、芒果小穴壳(Dothiorella dominicana Pet.et Cif.)和芒果拟茎点霉(Phomopsis mangiferae Ahmad.)4种芒果采后病害病原菌发酵液的挥发性气味进行检测,以评估电子鼻用于芒果不同真菌病原菌种类判别的可行性。结果表明,对气味响应值进行的主成分分析(PCA)、线性判别分析(LDA)及聚类分析均能够正确区分不同病原菌种类。多因素方差分析(MANOVA)结果显示,不同病原菌之间的差异显著(p0.05)。结果为芒果采后病原菌种类判别提供新的方法,为其他病原菌的种类判别提供参考。     

科尔沁沙丘-草甸相间地区表土饱和导水率的土壤传递函数研究

本研究以科尔沁沙地典型坨-甸相间地区为研究区,野外布设240个采样点,对流动沙丘、半固定沙丘、固定沙丘、沙丘区杨树林、沙丘区耕地、低覆盖度草甸、高覆盖度草甸、草甸区耕地、撂荒地九种地貌类型下的表层土壤进行了采样,测定了这些样点的含水率、干容重、有机质、饱和导水率等理化特性参数,分析了不同地貌类型下表层土壤理化参数差异。选取Campbell、Cosby、Wosten1997/1999、Saxton四种土壤传递函数,对该地区表土饱和导水率进行了预测,结果显示这几种土壤传递函数预测值与实测值偏差较大,相关系数均小于0.3,由此可见这几种传统的土壤传递函数在本地区应用具有一定的局限性。在此基础上,选取土壤容重、有机质含量、饱和含水率、平均粒径、粒径标准偏差五种土壤特性参数作为输入变量,采用逐步多元统计回归、主成分分析及非线性回归分析相结合的方法,重新建立了预测本地区表土饱和导水率的土壤传递函数,结果显示预测值与实测值相关系数为0.648,该传递函数可应用于科尔沁沙地表层土壤饱和导水率的预测。     

Statewide modeling of bobcat, Lynx rufus, habitat in Illinois, USA

We used sighting location and remotely sensed habitat data, multivariate statistical techniques, and a geographic information system to model bobcat (Lynx rufus) habitat in Illinois, thereby providing state wildlife managers with information to review the listing of bobcats as a state-threatened species and contribute to the development of a statewide management plan. We used canonical discriminant function analysis to model presence/absence and relative abundance of bobcats statewide. These models suggested that bobcats occurred in moderate to high abundance in 23 of 98 counties statewide (23%). We used stepwise logistic regression (SLR) analysis to model statewide habitat suitability. Spatial modeling of the SLR equation predicted that 29% of Illinois contained suitable habitat classified as P>0.50. Models were accurate when validated with an independent data set and indicated the importance of woods-related habitat variables to bobcats. In conclusion, these models provided tools to rapidly assess status that contributed to delisting bobcats as a threatened species in Illinois and provided further information to guide conservation efforts.     

Outcomes of longterm deciduous forest restoration in southwestern Ontario, Canada

At present, forest cover in southwestern Ontario, Canada, remains at less than 5% due to intensive agricultural and urban land use. Although much of the extant forest is increasingly protected by legislation, remnants continue to be degraded by the spread of non-native plant species, overgrazing, and recreational use. Some parks in the region have adopted management programs aimed at mitigating this degradation. Over the last 35 years, cottages and roads at Point Pelée National Park have been removed and sites either passively restored (i.e. road or cottage eliminated and vegetation allowed to regenerate) or actively restored (i.e. road or cottage eliminated, exotic vegetation removed, and native species planted). In 1994 and 1995, we assessed the effectiveness of restoration by comparing the understorey plant communities in 28 restored sites with those in less disturbed reference sites. There was a significant increase (P<0.0001) in the similarity of understorey plant communities between restored and reference sites as time-since-restoration increased. Soil moisture, canopy cover, distance to continuous forest, and site-shape all significantly affected plant species composition. Former road sites recovered significantly (P<0.05) more rapidly than former cottage sites, and the former lawns of passively restored cottage sites were the slowest to recover. Five years following active restoration, non-native ruderal species continued to dominate restored sites. The observed recovery of understorey plant communities in restored sites is attributed to their proximity to natural vegetation, and its function as a seed source. In some sites, recovery is substantial and, assuming present trajectories of change are maintained, we predict that recovery could occur in many mesic sites within the next 20 years. Restoration activity facilitates forest recovery and would appear to have a valuable function in mitigating ongoing conflicts between conservation and human use in this region.     

基于灵敏度分析的木薯精播机机架结构优化设计

木薯生产机械化程度低是制约我国木薯产业发展的瓶颈之一,研究高性能的木薯精播机对于促进木薯产业稳定发展具有重要推动作用。木薯精播机结构组成复杂,为提高工作性能,机架必须具有良好的结构与力学性能。本文以课题组研制的双行木薯播种机均匀精量自动排种装置的机架为研究对象,采用UG联合ANSYS软件建立机架的有限元模型,使用ANSYS Work Bench对机架进行静力学分析、约束模态分析以及灵敏度分析。通过模态分析确定优化响应,灵敏度分析确定设计变量,模型建立确定优化目标,多目标优化设计数学模型计算得到6组非劣解。在所得6组方案和初始方案中,基于熵权的模糊物元模型抉择出最优的机架结构方案。双行木薯播种机均匀精量自动排种装置机架优化前后对比分析表明,第一阶模态频率提升3.60%,机架质量减轻8.76%,最大变形减小5.08%,较好的达到了机架轻量化结构优化目的,研究结果可为木薯精播机的设计提供参考。