Landscape factors and regional differences in recovery rates of herb layer richness in Flanders (Belgium)

The recovery of understory plants in recent forests is critical for evaluating the overall capacity of landscapes to maintain plant biodiversity. Here we used a large data set of vegetation plots from the Flemish Forest Inventory in combination with maps of forest history and soil-based Potential Natural Vegetation to evaluate regional differences in the rate of recovery of understory plant diversity in three regions of Flanders, Belgium. We expressed the degree of recovery in recent forests using the species richness of ancient forests as a reference point, and found strong differences among regions in the average level of recovery. These differences appeared to be due to regional variation in average patch connectivity and age (ultimately stemming from differences in land use history) and – to a lesser extent – environmental conditions. We also found an increase in the proportional representation of vertebrate dispersed species and species with short-distance dispersal with increasing levels of recovery. Our results highlight the potential drivers of inter-regional variation in the process of recovery of plant diversity during restoration, and they emphasize the importance of historical and spatial context in the recovery process.     

Spatial aspects of metapopulation survival – from model results to rules of thumb for landscape management

The role of spatial configuration for metapopulation survival is analyzed by using a stochastic metapopulation model. This model reveals conditions which must be satisfied by the species' ecology and the landscape settings before a metapopulation can persist over a long term. Taking this as a basis, initial rules of thumb for landscape management are deduced. The following results are highlighted: (1) the critical correlation length d_c of the extinction processes determines a spatial scale of the metapopulation dynamics. (2) Only species with a dispersal range d_r above the correlation length d_c are able to benefit from landscape management at all. (3) A certain metapopulation can only persist over a long term if no patch is inside the range of correlation of another one. (4) There is a hierarchy of importance in the characteristics of a spatial configuration (scale and type) and, hence, in the scopes of landscape management. To conclude, some general consequences for supporting species survival by management are discussed. Some prospects concerning the use of models for decision support in landscape planning are discussed.     

Statistical models of landscape pattern metrics,with applications to regional scale dynamic forest simulations

Forest managers in Canada need to model landscape pattern or spatial configurationoverlarge (100,000 km²) regions. This presents a scalingproblem, as landscape configuration is measured at a high spatial resolution,but a low spatial resolution is indicated for regional simulation. We present astatistical solution to this scaling problem by showing how a wide range oflandscape pattern metrics can be modelled from low resolution data. Our studyarea comprises about 75,000 km² of boreal mixedwoodforest in northeast Alberta, Canada. Within this area we gridded a sample of 84digital forest cover maps, each about 9500 ha in size, to aresolution of 1 ha and used FRAGSTATS to compute a suite oflandscape pattern metrics for each map. We then used multivariate dimensionreduction techniques and canonical correlation analysis to model therelationship between landscape pattern metrics and simpler stand table metricsthat are easily obtained from non-spatial forest inventories. These analyseswere performed on four habitat types common in boreal mixedwood forests: youngdeciduous, old deciduous, white spruce, and mixedwood types. Using only threelandscape variables obtained directly from stand attribute tables (totalhabitatarea, and the mean and standard deviation of habitat patch size), ourstatistical models explained more than 73% of the joint variation in fivelandscape pattern metrics (representing patch shape, forest interior habitat,and patch isolation). By PCA, these five indices captured much of the totalvariability in the rich set of landscape pattern metrics that FRAGSTATS cangenerate. The predictor variables and strengths of association were highlyconsistent across habitat classes. We illustrate the potential use of suchstatistical relationships by simulating the regional, cumulative effects ofwildfire and forest management on the spatial arrangement of forest patches,using non-spatial stand attribute tables.This revised version was published online in May 2005 with corrections to the Cover Date.     

基于用例图呼叫处理场景的不确定性冲突过滤方法

基于用例图建立的呼叫处理模型，针对Nakamura提出的业务冲突过滤方法中基桩配置矩阵合并开销过大和过滤检测结论冗余过多的缺点，从增加排除合并前提条件和增强过滤检测定理两个方面进行了改进，并提出了改进的过滤算法．计算机模拟实验结果证实：该改进算法不仅能够明显提高业务合并的效率，同时还能更加精确地定位冲突，减少不确定性结论，提高过滤检测性能．     

Manipulation of the availability of assimilates for kernel growth in wheat in Japan: Effects of crop thinning and planting geometry

Wheat often overproduces kernels when grown in favorable environments, resulting in low kernel weight with high kernel screenings. This indicates that photoassimilation after heading would not be sufficient to support the growth of a large number of kernels. The objective of this study was to examine the effects of crop thinning at heading (experiment 1) and double-row planting (compared with equidistant row spacing; experiment 2) on kernel weight and yield of Japanese wheat cultivars under different levels of soil fertility. In experiment 1, elimination of aboveground competition for radiation by thinning increased yield by up to 32%, mainly due to increased kernel weight. In experiment 2, double-row planting increased kernel weight significantly (by 4–10%) without yield loss by moderately suppressing maximum stem number (by 7–14%) and spike and kernel number (by up to 14%) under high fertility. In both experiments, the effect of crop thinning or row configuration on wheat yield and kernel weight was negligible under low fertility because of little competition for radiation. The results suggested that control of vegetative growth and kernel production would help avoid the shortage of assimilates for kernel growth in fertile environments. For further increasing wheat yield under favorable conditions in Japan, the appropriate crop management options (e.g., planting geometry) should be combined with the suitable varieties having a more communal ideotype (sparse tillering with upright posture) than a competitive phenotype (profuse tillering with lax posture) to enhance photoassimilation after heading.     

实施农业综合开发，加快产业化经营步伐

三明市结合山区实际，大力实施农业综合开发项目，紧密围绕农业增效、农民增收、农村稳定这一目标，注重土地治理项目和产业化项目的有机结合，加强农业基础设施建设，扶持龙头企业，加快农业产业化经营与新农村建设步伐，农业综合开发工作取得了明显成效。结合三明市工件实际，提出建议。     

Be2+ 1s3d组态能量的变分法研究

利用拉卡方法和对角和不变法则导出铍离子1s3d组态的2个谱项式,利用波动力学的变分法得出两谱项的能量值,结果与实验值相比较符合较好。     

黑河流域水资源供需平衡与配置研究

水资源合理配置是水资源高效利用的重要手段,同时是水资源可持续利用的核心问题。针对黑河流域水资源利用现状与存在的问题,运用系统分析理论与方法,对黑河流域水资源需求、供水能力、水资源配置与供需平衡进行了分析与讨论。结果表明:在50%保证率下,黑河流域2015年、2020年和2030年需水量分别为3.271×10⁹ m³,3.041×10⁹ m³和3.071×10⁹ m³,供水量分别为2.841×10⁹ m³,2.972×10⁹ m³和3.033×10⁹ m³,缺水量分别为4.30×10⁸ m³,0.69×10⁸ m³和0.38×10⁸ m³,缺水率分别为13.15%,2.27%和1.24%。针对流域水资源现状,应采取提高工业用水重复利用率、调整农业种植结构、大力发展高效节水技术等措施。继续加强流域水资源高效管理,改善流域生态环境,提高流域内水资源可持续利用能力。     

宁夏甘草资源的价值和保护利用

通过对甘草Glycyrrhiza uralensis经济价值和生物学、生态学特性的介绍,针对宁夏甘草资源利用现状,提出了甘草资源保护利用的措施.     

新疆农牧灌区建设与水利工程规划设计

新疆土地辽阔,日照充足,光热资源丰富。但降水稀少、气候干旱、春秋季来水与用水矛盾突出,水资源利用不合理。尤其是南疆农牧业基础薄弱,引水保证率低,灌溉工程不配套,工程设施老化,效益低下,灌区及下游生态环境日益恶化。通过分析新疆农牧灌区水利工程现状的主要问题,对新疆水利工程规划设计、灌区及生态建设等方面的问题进行了探讨。