逐步判别的一种快速算法

本文给出了逐步判别的一种快速算法及其计算机程序框网,并给出了应用实例     

Temporal change in land use and its relationship to slope degree and soil type in a small catchment on the Loess Plateau of China

We sought to detect the temporal change (1958–1999) in land use patterns and its relationship to physical landscape parameters in a small catchment in the semi-arid hilly area of the Chinese Loess Plateau. Degree of slope and soil type were selected as stable discriminating parameters that might constrain land use. With the help of GIS and canonical correspondence analysis, the relationship between rural land use distribution or transformation and the selected physical parameters was examined. The land use had undergone a general shift from farmland to woodland or grassland. Canonical correspondence analyses (CCA) indicated that a relationship between land use and the selected physical parameters was evident, farmland coincided with favorable conditions of fertile soil and gentle slope, while grassland and woodland were associated with conditions of poorer soil and steep slope. In the more favorable conditions the main land use change process was the intensification of farming, while in the less favourable conditions it was the abandonment of farmland. A thorough understanding of the relationship between land use temporal or spatial patterns and landscape physical parameters in the Loess Plateau of China, like degree of slope and soil type, will enhance our capability to predict landscape dynamics and lead to more sound and effective land use management strategies.     

Relationships between microbial community structure and soil environmental conditions in a recently burned system

Most wildfires, even the most severe, burn at mixed intensities across a landscape, depending on local fuel loads, fuel moistures, and wind strength and direction. This heterogeneous patchwork of fire effects can influence the patterns of above- and belowground biotic recovery through altered environmental conditions, nutrient availability, and biotic sources for microbial and vegetative re-colonization. We quantified the effects of low- and high-severity fire 14 months post-burn on key environmental variables typically limiting to microbial activity. We characterized the soil microbial community structure through ester-linked fatty acid analysis (EL-FAME) and identified the soil environmental factors that best explain the pattern of microbial community profiles through canonical correspondence analysis (CCA). Low-severity burning caused no change in soil moisture, pH or temperature while high-severity burning caused an increase in soil moisture, temperature, and a decrease in pH levels, relative to the unburned sites. Soil respiration rates were significantly lower in both the low- and high-severity burn sites, relative to unburned sites, likely due to initial root and microbial death. Overall microbial biomass did not change with either low- or high-severity burning, but the microbial community ordination biplots showed separation of communities by fire, and slight separation by fire severity along three axes. This community separation was driven primarily by a decrease in fungal biomarkers (18:2ω6c, 18:3ω6c) with both low- and high-severity fire. Only 23% of the variation in the microbial community distribution could be explained by three environmental variables: soil pH, temperature, and carbon. These results suggest that the microbial communities in both the low- and high-severity burn sites are structurally different from the populations in the unburned sites.     

Can conversion to organic farming restore the species composition of arable weed communities?

Benefits of organic cropping for biodiversity have usually been demonstrated in relation to modern conventional cropping. In this study, the ability of organic cropping to restore species composition of weed communities was explored by comparing weed communities of present day organic cropping with weed communities at the beginning of the application of modern cropping measures in the 1960s. The data of two weed surveys of spring cereals (conducted in 1961-1964 and 1997-1999) in Finland were utilized for a comparison. Frequency of occurrence and density (plants m⁻²) of 41 weed species were compared between decades. Partial canonical correspondence analysis (pCCA) was applied to explore the relationship between species composition, management and non-management variables. Eight species had lower and 30 species higher or similar frequency of occurrence in the 1990s’ organically cropped fields than in the fields of the 1960s. However, 18 species had lower and 20 species had higher or similar density in the organically cropped fields than in the fields of the 1960s. Three species were not detected at all in the organically cropped fields. Crop and under-sown grass explained more of the variation in species composition in the 1990s than in the 1960s. The role of drainage and pre-crop was more important in the 1960s than in the 1990s. The most immediate benefit was gained by nitrophilous species that had suffered from herbicide application. The recovery of perennials and non-nitrophilous species will take a longer time. The results suggest that despite some benefits for biodiversity, organic farming at early phase cannot recover weed populations to the same level as before application of intensive cropping measures.     

Strong effects of a plantation with Pinus patula on Andean subpáramo vegetation: a case study from Colombia

The effect of a pine plantation on a native subpáramo system in the Andes of Colombia (3100 m above sea level) was studied. The vegetation of an 8 year-old plantation with Pinus patula was compared to that of the surrounding native subpáramo. 59 plots made in the subpáramo vegetation contained 121 vascular plant species. These plots were classified into three subpáramo communities and one Andean scrub community. Sixty-four plots made in the pine plantation contained 76 vascular plant species and were subdivided into four classes of pine cover. With increasing pine cover, pine plantation plots tended to become less similar to the subpáramo communities. Habitat-specific subpáramo species tended to disappear with increasing pine cover. After controlling for the effects of environmental variables in a partial canonical correspondence analysis, pine cover had a significant impact on plant species patterns. It is concluded that afforestation with Pinus patula resulted in strong negative effects on diversity and composition of the subpáramo vegetation at the study site.     

泌阳县肉牛常用饲料原料营养成分检测分析

[目的]分析夏南牛主产区主要饲料原料营养成分,为草食动物饲养提供参考数据。[方法]采集了全株玉米青贮、花生秧、麦秸、玉米秸秆黄贮、稻草、酒糟、干玉米秸秆7个粗饲料样品及玉米、麸皮2个精饲料共28个样品,委托郑州奥瑞森生物科技有限公司,采取概略养分分析法,进行了主要营养成分的分析检测。[结果]结果表明,全株玉米青贮、花生秧、麦秸、玉米秸秆黄贮4种主要粗饲料的干物质、粗蛋白、粗灰分、酸性洗涤纤维、中性洗涤纤维、钙、磷平均含量分别为:27.49%,8.22%,6.55%,54.05%,36.23%,0.35%,0.38%;89.24%,8.36%,12.11%,61.87%,56.35%,1.38%,0.33%;92.13%,3.49%,8.41%,78.98%,55.89%,0.30%,0.13%;31.87%,7.44%,6.85%,55.70%,35.95%,0.38%,0.30%。[结论]全株玉米青贮的综合营养价值最高,其次是玉米黄贮,第三是花生秧,麦秸粗蛋白含量最低。花生秧和麦秸钙磷比例不平衡,比例分别达到4.18∶1和2.31∶1。在肉牛饲养中,不提倡单一粗饲料饲喂,为实现营养均衡,建议2种或2种以上粗饲料合理塔配饲喂。     

华东3省1市加拿大一枝黄花分布和发生规律的定量调查研究

对华东3省1市(安徽、江苏、浙江和上海)的加拿大一枝黄花群落进行定量的生态学调查,将各环境生态因子量化,进行主成分分析(PCA)和典范对应分析(CCA),结果表明,入侵生境的植物群落均以加拿大一枝黄花为优势种,与加拿大一枝黄花频繁伴生的植物中藤本植物为常见的一类,它们能利用加拿大一枝黄花植株作为攀爬物,获取阳光。在23个生态因子中,土壤类型、湿润度、荫蔽度对加拿大一枝黄花分布的影响最大,加拿大一枝黄花趋向于入侵沙壤、湿润和开阔的生境。因此,推测江河湖泊的岸堤、沼泽、沿海滩涂、高速公路、铁路边、人工裸地极易受到加拿大一枝黄花的入侵,应该加强对这些生境的监管。     

县域农村金融排斥地域差异及影响因素研究

利用灰色关联分析法和灰色聚类分析法,基于吉林省39个县的数据,对县域农村金融排斥地域差异及影响因素进行测度,结果表明:1)吉林省县域金融排斥严重,金融排斥指数FEI(Financial exclusion index)0.5的县占44%;2)县域农村金融排斥存在显著的地域差异,FEI0.5的县,50%以上分布在东部地区;3)东部地区半数以上的县FEI≥0.5;4)第一产业比重越高、城乡收入差距越大,则农村金融排斥越严重;5)工资性收入的比重越高、农村金融贡献度越大、农户人均收入水平越高,则金融排斥程度越低。缓解农村金融排斥应该根据影响因素的作用方向采取针对性措施。     

水稻品种产量性状的遗传相关及通径分析

通过对水稻品种的几个主要产量性状的遗传相关和通径分析表明,结实率、每穗实粒数、穴穗数与产量间有较高的遗传相关和通径系数。在选育水稻新品种中,应在稳定千粒重和较高结实率的基础上,把穗实粒数和穴穗数作为重点选择指标,可望选育出高产水稻品种。     

对承德市主城区行道树的调查与分析

行道树作为道路功能的配套设施,在城市道路绿化与园林绿化中起着重要作用,也是城市森林的重要组成部分。通过行道树释义和对承德市主城区行道树的调查与分析,提出其存在的问题和发展建议,旨在提高其相应防护、美观、特色等效果,促进承德主城区行道树向健康有序的方向发展。