Canopy attributes of desert grassland and transition communities derived from multiangular airborne imagery

The surface bidirectional reflectance distribution function (BRDF) contains valuable information on canopy physiognomy for desert grassland and grass-shrub transition communities. This information may be accessed by inverting a BRDF model against sets of observations, which encompass important variations in viewing and illumination angles. This paper shows that structural canopy attributes can be derived through inversion of the Simple Geometric Model (SGM) of the BRDF developed in this paper. It is difficult to sample BRDF features from the ground because of the discontinuous nature of the canopies and long intrinsic length scales in remotely sensed spectral measures (>10 m). A multispectral digital camera was therefore used to derive spatial multiangular reflectance data sets from the air and the SGM was validated against and inverted with these. It was also validated using 3-D radiosity simulations driven with maps of field-measured plant dimensions. The interpretation of the retrieved parameter maps (shrub density, shrub width and canopy height) reveals variations in canopy structure within desert grassland and grassland-shrubland transition communities, which are clearly related to structural and optical features in high resolution panchromatic and vegetation index images. To our knowledge, this paper reports on the first attempts to acquire structural canopy attributes of desert landscapes using multiple view angle data at scales less than 1 km. The results point to further opportunities to exploit multiangular data from spaceborne sensors such as the Multiangle Imaging SpectroRadiometer (MISR) and the Compact High Resolution Imaging Spectrometer (CHRIS) on the NASA Terra and European Space Agency's PROBA satellites, respectively.     

戈壁地区可控震源线性干扰波衰减方法探讨

柴窝堡工区地震测线线性干扰大,尤其是浅层的干扰。去除干扰、优化叠前数据是保证地震剖面成像效果的关键。经对比研究后认为,"开时窗道组合+面波衰减"处理方式适宜用于柴窝堡工区及相似地区地震资料的叠前处理,处理后的叠加剖面,在同相轴的连续性和能量上都有所改善和提高。     

运用EXCEL提高沙漠地区地震勘探井深设计效率的方法

沙漠地区三维地震勘探井深设计的数据量较大。鉴于EXCEL的公式、函数、逻辑判断、自动填充及图表等数据处理功能,研究出一套较为实用的计算方法及流程,并在地震项目的井深设计中加以运用,实现了成果检查自动化,取得了较好的应用效果。井深设计的主要步骤是分别建立原始、设计、井深、表用和任务5个数据文件。     

Experimental and numerical analysis of a tube-type networked solar still for desert technology

A tube-type solar still is proposed to integrate a conventional still and a water distribution network suitable to our concept of desert plantation. This still is directly set up on ground-like pipelines connecting brackish water or seawater ponds. The distilled water is immediately supplied to the plants under the ground by penetration without any extra water pipelines. The still is made of metal-free materials, e.g., plastic as vinyl chloride or PET resin which are inhibited from corrosion by seawater. Experimental data measured in our laboratory using infrared lamps showed the effectiveness of the method for productivity, the design of the basin tray and thermal efficiency up to 12.5%. Numerical simulations with experimental data as the temperature profiles at the tube walls estimated heat convection occurring within the still for modification of the Dunkle's model. Active convection over the basin was predicted in the half-cut tube type of the basin as compared with a conventional flat basin. The secondary convective circulations under the basin in case of the flat basin promote bulk flow from the upper part of the basin to the lower part, which suggests the necessity of insulating the lower part of the still. On the other hand, the tube basin enlarges the evaporative area over the basin and restricts the vapor circulation under the basin. Simulated results show that the performance of this type is not necessary for the insulation of a still and possible for setting up the lower part of the still under the ground. The tube-type solar still is very simple and has been researched, but further research is needed to make it a suitable technology for desert plantations.     

Bringing water markets down to Chile’s Atacama Desert

The Chilean water model has been described as a textbook example of a successful free water market system. This paper analyses water-rights transactions to determine how this water market has behaved in the northern Atacama Desert. It questions the neoliberal assumption that Chile’s unregulated water market has acted as an active tool to reallocate water towards uses that provide the highest economic value. Instead, it argues that the state is the central actor in water allocation. This problematizes the notion that the Chilean water model is one of the most unregulated in the world.     

全掏挖基础在戈壁滩地区输电线路中的应用

基于戈壁滩输电线路碎石土地基全掏挖基础试验,在戈壁滩地区全掏挖基础上拔破坏模式研究的基础上,对土体剪切面半径影响参数n、上拔剪切范围内土重等方面进行了研究分析,提出了抗拔承载力修正公式;同时建议戈壁滩碎石土地基中的掏挖基础按摩擦端承桩进行抗压承载力计算;利用上述成果,对±800kV输电线路全掏挖基础几何参数采用遗传算法进行优化,结果表明,按推荐的全掏挖基础与按规范通用计算公式(n=1.5)设计的全掏挖基础相比,综合造价节约20%以上。     

水化学成分聚类法分析干旱区地下水补给

以巴丹吉林沙漠及邻区为例,基于距离空间基本原理,对水样化学成分进行了离散性、主成分和相关性分析,指导样品数据采集和化验。计算结果表明,祁连山冰川融水自身化学成分在该地区聚类最高,多次聚合说明祁连山冰川融水是该地区地下水补给源。由聚类图推测:祁连山冰川融水通过地下首先经过诺尔图,然后到达古日乃和拐子湖;古日乃和拐子湖地下水某些样品聚合距离大,可能是由黑河水渗入引起的,少量黑河水可通过古日乃渗入拐子湖引起地下水成分变化;没有迹象显示黑河水补给巴丹吉林沙漠(以诺尔图为代表)地下水。     

毛乌素沙地喷灌蒸发漂移损失试验研究

对毛乌素沙地喷灌条件下蒸发漂移损失进行了试验研究,经数据分析,得出风速和空气相对湿度是影响当地灌水损失的重要因素,当风速<3 m/s时,喷灌水的利用率可达80%以上,此气象条件下适宜进行灌溉。     

Premating Isolation is Determined by Larval Rearing Substrates in Cactophilic Drosophila mojavensis. VII. Effects of Larval Dietary Fatty Acids on Adult Epicuticular Hydrocarbons

Low concentrations of dietary triacylglycerols including tristearin, triolein, and tripalmitolein, were assessed to determine their effects during egg to pupal stages on adult epicuticular hydrocarbon (EHC) variation in cactophilic Drosophila mojavensis. Triacylglycerols were added singly and in combination at concentrations of 1%, 3%, and 9% to a lipid-free culture medium. Control diets included Carolina Drosophila and lipid-free media. Egg to adult viability was reduced at triacylglycerol concentrations greater than 1%, except for tristearin. Both triolein and tripalmitolein increased EHC amounts to levels similar to those in combination and control diets. Tristearin caused significantly lower quantities of EHCs in adult flies than triolein or tripalmitolein, consistent with previous studies on reduced tristearin assimilation into adult EHCs. We rejected the hypothesis that unsaturated and saturated triacylglycerols were assimilated into unsaturated and saturated adult EHCs, respectively. Since these triacylglycerols comprise a fraction of known lipids in the columnar cacti used for breeding in nature, and EHCs serve as contact pheromones in D. mojavensis, these and other naturally occurring triacylglycerols may provide a direct causal link between host plant use and patterns of chemically mediated mate choice. Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

基于纹理的乌兰布和沙漠地区植被信息提取

乌兰布和沙漠是我国主要的沙漠之一,近年来,其快速扩张已严重影响当地的生态安全。荒漠植被是该地区最重要的生态防护屏障,准确掌握植被分布状况具有重要意义。以乌兰布和沙漠的典型地区为研究对象,通过NDVI计算、主成分分析以及基于灰度共生矩阵纹理特征相结合的方法,对ALOS多光谱影像进行分析,综合NDVI和均值纹理作为分类指标,确定合适的阈值范围,采用决策树分类方法进行植被信息提取。研究表明,决策树分类可有效运用纹理等辅助信息,与传统分类方法相比能够取得更好的分类效果。