Field estimates of scalar advection across a canopy edge

Measurements of the horizontal and vertical fluxes of energy and mass were taken at a crop canopy edge and downwind of it to examine the effects of inhomogeneity on surface-atmosphere exchange, for the ideal case of flat uniform terrain. Energy balance closure was also examined and the effects of the often-neglected advection terms on the energy budget were evaluated. The results show that neither vertical nor horizontal advection should be neglected for moderate distances downwind from heterogeneous boundaries, with the energy budget closure near the leading edge improved by more than 20% with the inclusion of the horizontal and vertical advection of latent and sensible heat. Significant mean advective horizontal and vertical flux divergences of water vapor and temperature were found even in typical daytime conditions. In stable conditions horizontal advection can be responsible for more than 15% of the scalar (water vapor) transport 136 canopy heights downwind of a change in water vapor source density and surface roughness.     

基于红边参数的棉花冠层叶片氮积累量之估算研究

测试了棉花2个品种4水平种植密度的4个关键生育时期冠层反射光谱,应用微分技术处理棉花冠层反射光谱,提取了红边(680～750nm)波段范围的最大一阶微分值(Dr)和红边面积(SDr)参数。分析了棉花冠层红边参数在不同生育期的变化特征和棉花吐絮期的两种生长类型的冠层红边状况,表明红边位置可以指示它们的氮素状况。以新陆早8号的SDr为自变量与对应的LNA为因变量进行相关分析,SDr与冠层LNA达1%极显著相关(R=0.9186**,n=32),利用其构建的模型方程估算新陆早6号的LNA,实测LNA和估测LNA的估计标准差为0.8909g/m2,估算精度为88.1%(R=0.9277**,n=32),说明采用高光谱提取的红边参数信息是无损实时、快捷评价棉花氮素状况的有效方法。     

分形与形态学在原木漏节图像边缘检测中的应用

采用X射线无损检测系统透射被检测的原木,根据检测透射物体后射线强度的差异,得到漏节图像。将图像分割成若干子区域,应用最小盒计数法计算每个子区域的分形维数,将图像从空域描述变换到分形域描述。进而应用数学形态学对得到的分形维数图进行有效的边缘检测,以确定原木缺陷的种类。检测结果表明：将分形理论和数学形态学结合起来的边缘检测方法,可以快速、准确地检测出原木漏节图像边缘。     

贺兰山东坡直翅目昆虫群落的边缘效应(英文)

[目的]探讨边缘效应对贺兰山东坡直翅目昆虫群落的影响。[方法]样带法采集取样,采捕过程中针对采捕的不同种类及生境中的具体情况,采用网捕法、徒手捕捉、诱捕法等。采集时将昆虫标本毒死后带回实验室,制作针插标本,根据相关文献专著鉴定并记录直翅目昆虫的种类和数量。并通过物种丰富度、Shannon-Wiener多样性指数、均匀性指数、优势度指数、群落相似性指标和多度值对调查数据进行了分析。[结果]斑翅蝗科、斑腿蝗科和癞蝗科个体数量分别占总数的42.65%、29.15%和12.76%,构成研究区域直翅目昆虫的优势类群。直翅目昆虫数量沿疏林草地、边缘和荒漠草地依次增加,边缘多样性高于疏林草地和荒漠草地内部,且边缘与疏林草地差异显著;无论是疏林草地还是荒漠草地,直翅目昆虫群落多样性都是随着距边缘距离的增加而降低。在疏林草地-荒漠草地过渡带出现了栖息地广布种、利用边缘的栖息地广布种、利用边缘的栖息地特异种和逃避边缘的栖息地特异种4种边缘反应类型。[结论]该研究可为直翅目昆虫生物多样性的保护和开发利用及保护生物学的发展提供数据和理论基础。     

基于最大类间方差法的黄瓜病害叶片分割

以黄瓜病害叶片为研究对象,采用直方图阈值分割法去除背景,分别采用最大类间方差法(Otsu)和边缘检测法来分割黄瓜叶片中的病害部位,对比这2种方法的分割效果。最后,对已有的最大类间方差法进行了改进,对病害叶片图像的红色分量进行了病斑分割。结果表明,边缘检测法分割出来的病斑部位轮廓具有不完整性,而最大类间方差法的分割效果较好。采用最大类间方差法对黄瓜病害叶片分割取得了较理想的效果,为后续病害识别奠定了基础。     

Habitat Selection and Breeding Success in a Forest-nesting Alcid, the Marbled Murrelet, in Two Landscapes with Different Degrees of Forest Fragmentation

We studied habitat selection and breeding success in marked populations of a protected seabird (family Alcidae), the marbled murrelet (Brachyramphus marmoratus), in a relatively intact and a heavily logged old-growth forest landscape in south-western Canada. Murrelets used old-growth fragments either proportionately to their size frequency distribution (intact) or they tended to nest in disproportionately smaller fragments (logged). Multiple regression modelling showed that murrelet distribution could be explained by proximity of nests to landscape features producing biotic and abiotic edge effects. Streams, steeper slopes and lower elevations were selected in both landscapes, probably due to good nesting habitat conditions and easier access to nest sites. In the logged landscape, the murrelets nested closer to recent clearcuts than would be expected. Proximity to the ocean was favoured in the intact area. The models of habitat selection had satisfactory discriminatory ability in both landscapes. Breeding success (probability of nest survival to the middle of the chick rearing period), inferred from nest attendance patterns by radio-tagged parents, was modelled in the logged landscape. Survivorship was greater in areas with recent clearcuts and lower in areas with much regrowth, i.e. it was positively correlated with recent habitat fragmentation. We conclude that marbled murrelets can successfully breed in old-growth forests fragmented by logging.     

Post-fire habitat restoration of sables during winter season in northern slope of the Great Xing＇an Mountains

Habitat loss and fragmentation have been associated with the decline of endangered species. In 1987, a catastrophic fire in the northern Great Hing＇an Mountains of China, where the main habitat of sables （Martes zibellina） is located, aggravated the loss and fragmentation of the forest landscape. Due to restricted distribution and low population density, sables were listed in the national first-grade protected species in China. The objective of this paper was to identify to what extent the habitat of sables had been restored 13 years after the fire. Based on the behavioral data, which came from field survey information by radio-tracking, GPS （Global Positioning System） and forest inventory data, suitability habitat maps were derived using the Ecological Niche Suitability Model （ENSM）. In addition, the habitat structure was analyzed with selected landscape indices. Although forest cover mostly had been restored by 2000, the results indicated that, compared to the pre-fire situation, the areas of suitable habitat had been reduced significantly, especially those of less suitable, marginally suitable and moderately suitable designation. Fragmentation was aggravated, and suitable patches were found to be further isolated with the exception of those in most suitable areas. The ratio of the patch perimeter to area in unsuitable, moderately suitable and suitable areas decreased, while the ratios within other suitability types increased. Moreover, the percentage of soft boundaries decreased slightly, which can influence the redistribution of sables. The results above indicated that the suitable habitat had deteriorated, and the restoration of the sables＇ habitat remained to be done.     

Regional and local patterns of soil nutrients at Rocky Mountain treelines

The soils across treeline should vary because of direct effects of biological differences of coniferous subalpine forest and the herbaceous alpine tundra in Colorado. In addition, the change in life form may indirectly affect soils because of interactions of the vegetation and wind-driven deposition processes. This is particularly important as nitrogen (N) saturation is a growing concern in high elevation ecosystems, and treeline is predicted to be a deposition hotspot. The vegetation transition at treeline provides an opportunity to test the effects of vegetation, topography, and external inputs on soils at three spatial scales. First, a regional evaluation of soils at eleven abrupt treeline sites was made comparing sites on east and west aspects both east and west of the Continental Divide (CD). Second, soils were compared in the adjacent forest and tundra. Finally, edge effects were assessed along transects spanning treeline. At the regional scale, total soil N was higher east of the CD and on east aspects while exchangeable calcium was higher on east aspects and at sites west of the CD. Higher lead (Pb) concentration in the forest organic horizon was associated with lower ²⁰⁶Pb/²⁰⁷Pb ratios, an indication of greater anthropogenic Pb inputs. However, the spatial pattern in soil Pb suggests a different source area or transport mechanism than N. Within individual sites, the soils differed between the forest and tundra in almost every measured variable, but edge effects were minimal on both sides of these abrupt treelines. While a direct link between the observed soil patterns to deposition of external inputs cannot be made based on the study design, the observed soil patterns suggest that the impacts of acid deposition are amplified or attenuated by processes such as dust deposition.     

垄作模式下冬小麦边际效应研究

对边行和内行设置了不同密度水平,研究了垄作模式下小麦的边际效应。结果表明,垄作模式下小麦的边行优势较为突出,边行较内行增产较多,最优群体产量较常规方式增产,内行小麦在大群体下产量显著下降。试验范围内T5处理的群体结构最为合理,个体和群体生产力得以协调发展,产量最高。     

图像形态学在苹果自动分级视觉信息处理中的应用——以果梗判别与边缘检测为例

首先指出果梗判别在苹果自动分级系统中的研究意义;进而列出4种有代表性的判别果梗的方法;在此基础上提出了利用图像形态学可以更好地判别果梗,同时还能检测边缘;最后对该算法进行了系统评估,并为提高处理速度进行了改进.