Discrimination of native and exotic forest patterns through shape irregularity indices: An analysis in the landscapes of Galicia,Spain

Landscapes resulting from human activity may be expected to present simpler shapes than more natural landscapes. In the case of forest landscapes, the boundaries of native forest patches may be more irregular than those of exotic forest plantations. There is however a lack of quantitative results to this respect, and it is not clear which shape indices are more adequate for such discrimination. In this study, we analysed the shape of a large number of forest classes in the region of Galicia (Spain) using the Spanish Forest Map at a scale 1:50000 as the spatial information source. We considered a set of fifteen shape irregularity indices including those that have been commonly used in landscape ecology studies. We found systematic differences in the shape of the analysed forest classes, with native forests presenting both more complex and elongated boundaries than exotic forests. We suggest that these differences are due to the combined effects of human action and other topographical and hydrological factors. The only index that perfectly discriminated both types of forest was the mean circumscribing circle index. Other six indices provided also a significantly good discrimination: density of shape characteristic points, area-weighted mean perimeter-area ratio, area-weighted mean contiguity index, mean shape index, perimeter-area fractal dimension and mean largest axis index. Comparisons of pure and mixed forests with the same dominant species indicated that an increase in tree species richness is in general associated with more irregular boundaries in the forest. Discarding indices on the basis of a high statistical correlation may not be an adequate procedure to retain the best-performing indices. Finally, we discussed several limitations of some frequently used indices that may be relevant to prevent an improper characterization of landscape shape.     

求解凸二次规划的一种改进的原-对偶内点算法

基于牛顿方向,给出了求解凸二次规划问题的改进原对偶可行内点算法。若获得算法的初始可行内点,则该算法经过多次迭代之后收敛到原问题的一个最优解。数值试验表明了该算法的有效性。     

Songbird response to experimental retention harvesting in red pine (Pinus resinosa) forests

Traditional harvesting practices frequently result in simplification of the structure and composition within managed forest stands in comparison to their natural counterparts. In particular, loss of heterogeneity within stands may pose a problem for maintaining biodiversity in perpetuity. In this study, we survey breeding bird diversity and abundance in response to different spatial harvesting patterns in mature red pine forests located on the Chippewa National Forest of northern Minnesota, USA. Treatments are designed to increase structural complexity over time and include three overstory manipulations (dispersed retention, aggregate retention with small gaps, and aggregate retention with large gaps), one understory manipulation (brush removal), and controls (no harvesting, and/or no brush removal). In 2003, the first breeding season following the harvest, we found little difference in bird community composition between control and treatment stands. In 2005, the third breeding season following harvest, avian abundance, richness, and diversity were all greater within treatments. Species associated with edge, shrub, and early successional habitats generally show positive response to treatments (e.g. Chestnut-sided Warbler [Dendroica pensylvanica], Mourning Warbler [Oporornis philadelphia], Chipping Sparrow [Spizella passerine]), as do some species associated with mature forest (e.g., Pine Warbler [Dendroica pinus], Rose-breasted Grosbeak [Pheucticus ludovicianus]). Ovenbirds (Seiurus aurocapilla) and Black-throated Green Warblers (Dendroica virens) were more abundant in control stands. There are, as of yet, no discernable differences in avian community composition among the three overstory treatments or between the single understory treatment and the understory control, but differences are expected as the treatments diversify due to understory development. While overstory retention harvests provide habitat for a diverse and abundant bird community, the temporal divergence in avian community composition that we observed between treatment and control stands reveals the importance of uncut, mature red pine forest as a component of a biodiverse landscape.     

基于块排序的降噪方法及其在农业图像中的应用

农业图像采集过程中,环境因素常会带来噪声干扰,图像噪声又会对最终信息的分析结果带来影响,因此降噪对提高农业图像处理质量具有重要意义。基于块排序的非局部均值算法是一种有效的图像降噪方法,但是存在处理时间长,对大图像的处理内存要求高等问题。提出了分块优化方法,首先对大图像进行了适应于图像纹理丰富度的图像分块研究,然后分别对每个图像块进行处理。针对处理后的图像块再组合引起的边界效应,采用图像延拓的方法,有效地消除了边界影响,提高了图像降噪效果。实验结果表明,对于一般的硬件设备,改进的块排序非局部均值降噪算法能够快速处理农业中常用的图像。对于尺寸大小为512像素×512像素图像,当噪声标准偏差为50,分块数为16时,改进后的块排序降噪方法能够有效处理噪声图像。分块数为64时的处理速度是分块数为16时的1.89倍。     

周口市滨河公园大型土壤动物调查

2011年3～5月对周口市滨河公园绿地生境中的大型土壤动物进行了调查,共采获到土壤动物967只,隶属3门9纲17目.其中优势类群为后孔寡毛目、膜翅目和蜘蛛目,常见类群为等足目、膜翅目幼虫、柄眼目、鞘翅目、双尾目、鞘翅目幼虫、鳞翅目、双翅目和直翅目,其余类群为稀有类群.多样性指数分析结果表明,群落复杂性指数(Gj)表征的土壤动物多样性比多样性指数(H')更能客观反映土壤动物分布的真实情况.     

基于近似熵的径流序列复杂性研究

在引入近似熵并给出人类活动影响程度E的基础上,对黄河径流序列的复杂性进行了分析。结果认为,对黄河上游实测径流变化的研究应以洪水的变化为主,对天然径流变化的分析应以干旱(断流)为重点;而对黄河下游实测径流变化及天然径流的研究均应以干旱(断流)为主。     

基于无监督和YOLOX的农村房屋建设状态识别算法

【目的】 为了提升自然场景中农村在建房屋的识别准确率,并为后续的农村违建房屋智能化监管提供技术支撑。【方法】 文章基于无监督聚类和YOLOX目标检测算法,发展了一种乡村房屋在建状态识别方法。首先,构建在建房屋无监督聚类模型,并以此对在建房屋进行类别精细划分,使得不同类别之间特征差异较大,相同类别特征差异较小,其次,再使用划分好的类别制作房屋检测数据集,并训练YOLOX目标检测模型对在建房屋进行识别,最后,在在建房屋数据集上设计模型对比实验,以此验证算法有效性。【结果】 实验结果表明：在在建房屋识别任务中,基于无监督聚类和YOLOX的在建房屋识别算法mAP为83.27%,比采用原始数据（不进行在建房屋类别划分）训练的YOLOX算法mAP提升了7.91%,同时比采用人工划分类别的YOLOX算法mAP提升了5.08%。【结论】 因此该文方法有效提升了乡村房屋在建状态的识别精度,同时也为具有复杂场景和多个不同状态的目标进行识别时,提升识别准确率提供一种有效且可靠的解决思路。     

一种改进的混沌序列生成方案及性能分析

对一种混沌序列码的构造作了简单说明.在此基础上,提出了一种改进的生成方案.仿真和数据测试表明,改进后的序列不仅保持了原有序列的优点,具有良好的随机性,周期也得到了显著的扩展.     

城市公园鸟类群落多样性与复杂性初探

2013年1月至2015年3月采用样线法在北京地坛公园调查鸟类27次,利用多样性和复杂性指数研究了鸟类群落结构,探讨了群落多样性和复杂性随月份变化的规律,并分析了复杂性和多样性的相关性及影响因素,结果如下：（1）鸟类共计7目20科43种,优势种8种。群落丰富度在春季或秋季迁徙季节达到峰值。（2）总复杂性、无序复杂性和香农-维纳指数随月份变化趋势大致相同,春夏较高,秋冬较低,结构复杂性则不同,春秋季较高,盛夏和冬季最低。（3）群落总复杂性、无序复杂性以及香农-维纳指数随均匀度和丰富度的增加而增加,随优势度的增加而降低。结构复杂性与丰富度呈极显著相关（R=0.834, P<0.01）,丰富度越高,结构复杂性越高;优势度越高,结构复杂性越低。（4）香农-维纳指数与总复杂性相关性接近1（R=0.993, P<0.01）,说明总复杂性受香农-维纳指数影响很大。（5）结构复杂性和无序复杂性无明显相关（R=0.180, P=0.400）,不能用无序复杂性测度结构复杂性。     

Selecting the optimum genetic background for transgenic varieties, with examples from Brassica

Summary The performance of transgenic varieties depends not only upon the stable and correctly-regulated expression of specific transgenes but also upon the agronomic potential of the background genotype. Ideally, transgenes should be introduced into agronomically-superior cultivars and transgenic varieties will become out-classed if their agronomic properties are not continually improved. It will often prove desirable to use conventional breeding techniques, as opposed to new cycles of transformation, to carry out this process of varietal improvement.Continuing advances in marker-assisted selection have made possible the selection and manipulation of an entire genetic background. This means that transgenes can be transferred to new and often untransformable varieties with relative ease. To carry out this process efficiently requires the correct choice of male and female parents, the use of appropriate marker-systems and the concentration of selection on the most appropriate generations.Efficient, phenotypically-neutral marker-systems have revolutionised the identification and manipulation of quantitative trait loci (QTLs). The loci which modify the expression of transgenes are a form of QTL. Desirable alleles at modifier QTLs can be transferred to new varieties along with the transgenes themselves, using marker-assisted breeding.The strategies for maker-assisted selection are becoming ever more sophisticated. A range of complementary marker systems allows the selection of desirable genotypes. In addition, the meiotic reassortment and recombination of chromosomes which produces new genotypes is becoming better understood. The most efficient plant breeding methods and the most powerful genetics will make optimal use of both markers and meiosis.