Financial appraisal of date-frond mat fence systems for wind erosion control and sand dune stabilization in the arid region of the United Arab Emirates

A discounted cash flow model was employed to assess the viability of four wind barrier systems. The systems were utilized for wind erosion control and sand dune stabilization in the Al-Ain region of the United Arab Emirates. These systems consisted of four densities of date-frond mat fences erected in the form of checker board grids between rows of two local tree species:Prosopis spicigeraandAcacia tortilis. Analysis of cost estimated was based on the annual equivalent value of costs for each system. The economic life of the systems varied as a function of the time needed for the different trees in the different systems to reach the self-support stage. Results indicated that the systems’ ranking according to the minimal costs varied among the different tree types and the number of fences; but there was a general decrease in cost with increased fence density using the same tree, and this was due mainly to the effect of the fence on reducing the cost of tree development and maintenance as a result of reducing accumulated eroded sand. The minimal cost was recorded in D-10 treatment (seven fences) usingProsopis spicigera.     

The use of plant water relations to characterize tree species and sites in the drylands of northern Ethiopia

Water relations of four tree species were studied in four sites in the drylands of northern Ethiopia. Predawn water potentials were significantly higher at all sites as compared to midday measurements for Acacia etbaica and Boswellia papyrifera. In contrast, Lannea fruticosa revealed this significant difference only once, while Terminalia brownii at only two of the four sites. An analysis of variance showed that A. etbaica has a wider tolerance range as compared to the other species. There was no significant difference among the four sites in terms of predawn, midday and diurnal ranges of water potential. The study revealed that A. etbaica and B. papyrifera are performing better as compared to T. brownii and L. fruticosa under the current climatic conditions. Understanding the physiological basis of survival, productivity, ability to cope with low moisture availability, and growth potential of indigenous species in the drylands is essential for the utilization and promotion of these and other species.     

地理作用和集聚演化：基于数据挖掘的分析

经济集聚是工业社会中一种普遍存在的地理现象。它可以发生在不同的地理层面上,具有多种空间组织结构。在回答地理是否会影响集聚演化的问题上存在着两种不同的观点。其一是认为良好的地理环境将有助于经济集聚的产生,并且地理作用在其发展过程中持续存在;其二是认为地理仅是集聚形成的一个触发因子,其发展可以依赖纯经济因素而不是比较优势。本文运用数据挖掘技术,将演化时段分成集聚形成和集聚发展二个阶段,从另一个角度详细分析这两种观点。研究结论表明,集聚的形成受到自然地理要素的影响比经济地理要素要大。但经济地理要素对集聚增长具有显著的作用,经济因素和交通因素是集聚规模增加的关键所在,而自然地理因素作用被削弱了。     

寒地山区果林工程实例及推广应用前景

本文运用生态经济学原理,以黑龙江省东部低山丘陵区的光恩乡建设果林工程的经验为实例,分析寒地山区果林工程建设的生态、经济、社会效益。结果表明,果林工程是山区水土流失快速治理,自然资源合理开发利用,摆脱林业资源危机和经济危机,加快群众致富奔小康的有效途径,具有广阔的推广应用前景。     

Significance tests for multivariate normality of clusters from branching patterns in dendrograms

A significance test is presented for whether, based on levels of branches in a dendrogram, a cluster is from a multivariate normal distribution. The method compares the observed cumulative graph of number of branches with a graph derived from a simple logistic function. Provided the number of objects or variables is not small, the difference between graphs can be tested by the Kolmogorov-Smirnov, Cramér-von Mises, and Lilliefors statistics.Logistic functions were obtained by simulation and are available for three similarity measures: (1) Euclidean distances, (2) squared Euclidean distances, and (3) simple matching coefficients, and for five cluster methods: (1) WPGMA, (2) UPGMA, (3) single linkage (or minimum spanning trees), (4) complete linkage, and (5) Ward's increase in sums of squares. For simple matching coefficient, the mean intracluster similarity also is required.The method allows a test of whether the dendrogram could be from a cluster of smaller dimensionality due to character correlations. Good fit of the data to abnormally large or small dimensionality provides an important warning to interpretation of the dendrogram. Quantiles of test statistics were found by simulation to be well-approximated by logistic functions. The Lilliefors test is recommended for general use; if a conservative test is required, the two-tailed Kolmogorov-Smirnov test is most suitable. The method is suitable for use with a hand calculator, and a computer program for it is available from the author.     

用树木物候期做玉米播种期预报

利用呼和浩特1971—2007年气象资料与1988—2007年物候资料,分析了玉米适宜播种期与春季树木物候期的相互关系。结果表明:春季树木物候期与气温存在很好的相关性,用冬春季气温预报春季树木物候期,再由树木物候期确定玉米适播期,或用树木已出现的物候期预测下一个物候期,从而预报玉米适播期等方法均取得较好的预报效果。     

Event-scale floodplain accretion revealed through tree-ring analysis of buried plains cottonwoods,Powder River,MT, USA

Six plains cottonwoods along the axis of a meander were excavated to determine if dendrochronology could identify the year and location of germination and date past overbank sedimentation events. Samples from all excavated trees showed clear anatomical changes associated with burial, including increased vessel size, decreased definition of annual ring boundaries, and decreased ring widths. Some of these burial signatures were created by deposition of only a few centimeters of sediment, and most burial events were detected by multiple samples from the same tree. Four of the trees germinated at or near the upper surfaces of bar deposits, while two germinated within thin overbank deposits draped over bar deposits, indicating that germination is closely associated with bars. Dates and inferred thicknesses of overbank sedimentation events are consistent with repeated topographic surveys and data obtained from cesium-137 (¹³⁷Cs) analyses. However, the record of overbank sedimentation extracted from the trees does not entirely reflect the history of past peak discharges documented by stream gaging, largely because individual trees are progressively less likely to be flooded through time as the river migrates farther away. Germination dates and locations closely track past positions of the river channel. Germination elevations and the elevations of the tops of point bars appear to be decreasing with time as the bend migrates, implying vertical incision by Powder River at a rate of 7.1 ± 4.3 mm/yr. The rate of floodplain growth determined by elevation changes decreases progressively through time, ultimately reaching an apparent plateau after 0.8–1.3 m of vertical accretion. While similar patterns of vertical accretion have previously been interpreted as resulting from decreasing flood probability with increasing floodplain elevation, distance from the channel is also a first-order control on vertical floodplain growth. © 2019 John Wiley & Sons, Ltd.     

Comparison of data-driven modelling techniques for river flow forecasting

Abstract

Accurate forecasting of streamflow is essential for the efficient operation of water resources systems. The streamflow process is complex and highly nonlinear. Therefore, researchers try to devise alterative techniques to forecast streamflow with relative ease and reasonable accuracy, although traditional deterministic and conceptual models are available. The present work uses three data-driven techniques, namely artificial neural networks (ANN), genetic programming (GP) and model trees (MT) to forecast river flow one day in advance at two stations in the Narmada catchment of India, and the results are compared. All the models performed reasonably well as far as accuracy of prediction is concerned. It was found that the ANN and MT techniques performed almost equally well, but GP performed better than both these techniques, although only marginally in terms of prediction accuracy in normal and extreme events.

Citation Londhe, S. & Charhate, S. (2010) Comparison of data-driven modelling techniques for river flow forecasting. Hydrol. Sci. J. 55(7), 1163–1174.     

The relationship between sap flow of intercropped young poplar trees (Populus×euramericana cv. N3016) and environmental factors in a semiarid region of northeastern China

Estimating transpiration of the trees in agroforestry system is important in water management of the site. Sap flow of intercropped fast‐growing young poplar trees and microclimate factors in semiarid northeastern China was measured in two growing seasons (2008 and 2009). Sapwood growth and water storage of wood and leaf increment during the growing season were involved in the calculation of sap flow. The results showed that diurnal variation of sap flow followed to that of short wave solar radiation. Sap flows both in 10 min mean and daily gross values mainly depended on solar radiation and vapor pressure deficit, and the relations well fit hyperbolic function. The regression coefficients of monthly window data indicated that the seasonal variation of sap flow capacities decreased gradually from June to September. Moderate soil water stress of upper soil layer (0–50 cm) did not constrain the sap flow because the trees could use the water at deeper soil layer. The daily sap flow per tree ranged 0.8 to 18.1 and 3.7 to 23.8 kg d^?1 tree^?1, with averages of 8.7 and 14.3 kg d^?1 tree^?1 in 2008 and 2009 respectively. An empirical model was established to estimate the sap flow of the poplar trees by solar radiation, vapor pressure deficit, leaf area index and Julian days. Copyright © 2011 John Wiley & Sons, Ltd.