Ecological adaptation of Reaumuria soongorica root system architecture to arid environments

The architectural parameters of Reaumuria soongorica root system in different habitats of Gansu Province, China were analyzed to examine its ecological adaptability to arid environments. Results show that： （1） Topological indices of R. Soongorica root sys- tem are small in all habitats, and root branching pattem tends to be dichotomous. Also, the indices gradually increase in the Min- qin windblown sand region and the Zhangye Gobi region in Hexi Corridor, which indicates that drought tends to produce her- ringbone-like root branching pattems. （2） Fractal dimension values ofR. Soongorica root system are small and not obvious in the Minqin windblown sand region and the Zhangye Gobi region in Hexi Corridor, with values of 1.1778 and 1.1169, respectively. Fractal dimension values are relatively large in Jiuzhoutai semi-arid hilly and gully region of the Loess Plateau, which indicates that the R. Soongorica root system has better fractal characteristics in this region than in the other regions. （3） Total branching ra- tios of the R. Soongorica root system in arid regions of Hexi Corridor are smaller than that in the Jiuzhoutai semi-arid hilly and gully region of the Loess Plateau. This shows that root branching ability in the semi-arid region is stronger, and it decreases to some degree with increased drought. （4） The root connection lengths of R. soongorica root system are long in all habitats, but there are significant length differences between the different habitats. The root connection length at the Minqin windblown sand region is the longest. It is concluded that R. soongoriea adapts to arid environments by decreasing root branching, decreasing root overlap and increasing root connection length, which makes its root branching pattern tend to be herringbone-like to reduce com- petition in root internal environment for nutrients and to enhance root absorption rate of nutrients, and ensure effective nutrition space. Thus the roots can absorb enough water and nutrients in resource-poor settings to ensure normal physiological requirements.     

Cluster planting impact on cotton growth,yield and biomass accumulation in an arid region oasis

The cluster planting pattern(3 plants per hole) for cotton(Gossypium hirsutum L.) may increase economic yield over those of the traditional planting pattern(1 plant per hole) in arid regions of China. This increase in yield depends on either increased biomass production or greater partitioning to fruit. This study was conducted to determine whether differences in biomass accumulation or partitioning to reproductive growth contributed to higher yield in the cluster planting pattern compared with the traditional one. Growth parameters, biomass accumulation, crop growth rate and partitioning between cluster planting pattern and traditional planting pattern was compared in northwest of China. The biomass production and partitioning in cluster planting plot was higher than in traditional planting one. Biomass accumulation was faster early in the clustered treatment, and it was also higher at harvest time. Total dry matter production per unit area was significantly higher than in the traditional planting. On a per plant basis, dry matter accumulation was faster and total biomass production was significantly higher in the cluster planting pattern. Numbers of sympodia and boll sizes were also larger, indicating that facilitation among plants was promoting crop yield. The increase in yield in the cluster planting treatment occurred through increased partitioning of dry matter to fruits than in the traditional planting pattern, resulting in more bolls and increased lint yield in arid regions.     

Authors' reply to a comment on 'An objective method for smoothing palaeomagnetic data'

Summary. King & Rees (1979), in commenting on our paper (Clark & Thompson 1978), have raised a number of subjects beyond the main theme of our paper. We described a statistical method of smoothing noisy data and illustrated its application using a set of previously published palaeomagnetic declination data. King & Rees acknowledge our success in achieving the main aim of our paper, namely the construction of objective confidence limits for the smooth curve presumed to underlie the data. However, they seem to question the value of our general technique of data-analysis when used to estimate past variations in the geomagnetic field. As they interpose in their comments on our statistical analyses references to 'techniques of sedimentary analysis', 'inclination errors', 'mode of acquisition of remanence' and 'stability tests', we take the opportunity to discuss these additional topics as well as those relating to our original paper.     

Studies on the transfer of mineral nutrients from feed, water, soil and plants to buffaloes under arid environments

Studies were conducted at a Livestock Farm in an arid region of Pakistan, to determine the uptake of mineral nutrients from the food of buffaloes. Samples of feed, water, forage, soil as well as blood, milk, urine, and faeces of the animals were collected and analysed for K⁺, Ca²⁺, and Fe²⁺ during summer and winter. The results showed that the concentrations of K⁺ and Ca²⁺ in plants were low, whereas that of Fe²⁺ was high. In animals, K⁺ was not found in the milk in significant amounts, rather it was excreted in the urine. The calcium taken in by the animals was used for the synthesis of milk, as a result of which low Ca²⁺ concentrations were detected in urine. Mineral nutrient concentrations (K⁺ and Ca²⁺) in forage plants and water were lower than the optimum requirement of the animals, as a result of which blood plasma contained lower amounts of minerals (K⁺ and Fe²⁺) than that of the normal animals or critical limits. From the findings of the present study, it can be concluded that the buffaloes raised at the livestock farm had a severe deficiency of mineral nutrients, particularly K⁺ in lactating and Fe²⁺ in both lactating and non-lactating animals. Feed supplements, that can overcome these deficiencies, should be used for the optimum growth, milk production and resistance to diseases.     

A tool for estimating impacts of woody encroachment in arid grasslands: Allometric equations for biomass,carbon and nitrogen content in Prosopis velutina

Regression equations were developed to estimate above ground biomass and carbon and nitrogen mass of foliage and stem size fractions from plant size dimensions (basal diameter, canopy area, height, canopy volume) for a tall shrub species (Prosopis velutina) that has increased in abundance in arid and semi-arid grasslands in the southwestern United States and northwestern Mexico. Regression equations were also developed to describe relationships among the dimensions of plant size. All equations were significant (p < 0.001); and all but two had r² values >0.72. In addition to species-specific information, we found support for the global patterns of foliar biomass increasing to the ¾ power of stem biomass and height increasing to the ½ power of stem diameter. We provide a comprehensive report of all equations, which can support a variety of in situ (ground-based), modeling, and remote-sensing objectives related to quantifying changes in ecosystem function and carbon sequestration accompanying changes in woody plant abundance. We advocate that comprehensive reporting should become more common for arid and semi-arid woody species in order to support a broad spectrum of users while laying the foundation for the development of global generalizations similar to those available for forest trees.     

干旱区湿地信息的指数提取方法

以和田绿洲湿地为研究靶区,针对干旱区特有的地貌、气候特点,利用热红外波段在解译水体、湿地信息方面具有独特的优势,提出了基于热红外特征的干旱区湿地指数AZWI( Arid Zone Wetlands Index),详细叙述了AZWI的计算方法及过程,在总结传统主流方法的基础上,分别采用非监督分类、监督分类、决策树法和AZ...     

A method to obtain soil-moisture estimates over bare agricultural fields in arid areas by using multi-angle RADARSAT-2 data

Soil moisture is an important parameter for agriculture, meteorological, and hydrological studies. This paper focuses on soil-moisture estimation methodology based on the multi-angle high-and low-incidence-angle mode RADARSAT-2 data obtained over bare agricultural fields in an arid area. Backscattering of the high-and low-incidence angles is simulated by using AIEM(advanced integral equation model), with the surface-roughness estimation model built based on the simulated data. Combining the surface-roughness estimation model with the backscattering model of the low-incidence-angle mode, a soil-moisture estimation method is put forward. First, the natural logarithm(ln) of soil moisture was obtained and then the soil moisture calculated. Soil moisture of the study area in Dunhuang, Gansu Province, was obtained based on this method; a good agreement was observed between the estimated and measured soil moisture. The coefficient of determination was 0.85, and the estimation precision reached 4.02% in root mean square error(RMSE). The results illustrate the high potential of the approach developed and RADARSAT-2 data to monitor soil moisture.     

干旱区内陆河流域中游地区全新世沉积相变与环境变化——以石羊河流域为例

中国干旱区内陆河流域中游地区分布了大量晚第四纪河、湖相交替的沉积地层,这些沉积物被广泛用于古气候和古环境重建。然而,以往的研究较多关注沉积物的理、化、生指标,而忽略了沉积相变的古环境意义,这可能使古环境重建结果产生偏差。针对这一问题,选取干旱区典型内陆河——石羊河中游地区的JDT全新世沉积剖面,进行年代学、沉积相、岩性和粒度的研究,并与该区域已有的HSH全新世剖面的地球化学和古生物指标进行对比,在分析沉积相的基础上讨论二者的环境代用指标,重建石羊河中游地区全新世的古环境。两个剖面在年代和岩性上具有很好的一致性,指示了石羊河中游地区约8500 cal yr BP-3000 cal yr BP以来的沉积过程。两剖面从底部到上部可分为六层：河流相沉积（F层）——河湖相沉积（E层）——湖相沉积（D层）——浅湖—风成沉积（C层）——风成沉积（B层）——风成沉积（A层）,代表了不同沉积相及其转换过程。综合讨论沉积物岩性、沉积相和各种古环境代用指标认为：石羊河中游地区的沉积相体现了从河流相到湖相再到风成沉积物的变化过程,指示了全新世的干旱化过程。这与以往研究中认为石羊河流域全新世气候变化具有波动性的观点存在一定差异。因此,在研究沉积相变化的基础之上讨论沉积物的物理、化学和生物指标的含义,而非简单地研究这些指标的数值,是干旱区流域性气候变化对比研究的新视角。     

估算干旱区地下水依赖型植物蒸散发的White法评述

日尺度上的地下水位波动是干旱区地下水依赖型植物蒸散消耗地下水的直接证据与指示。White通过分析日尺度地下水位波动与植被蒸散之间的关系,提出了利用地下水位观测数据来计算植被蒸散速率的方法,简称White法。该方法由于计算简单,所需数据少,在干旱区河岸林蒸散定量方面得到了广泛的应用。本文通过系统回顾White法的提出、“四大假设条件”及其在实际应用中的不足,梳理了近年来对White法不断修订的总体思路,总结了各种形式White法的特点、使用条件以及存在的主要问题;在此基础上,提出了White法进一步改进的方向。当前,结合地表蒸散发的多尺度观测与模拟,White法不仅可以用来估算区域尺度地下水蒸散,而且能够为定量解析干旱区植物的水分利用来源提供验证与参考。     

Trophic interactions in an arid ecosystem: From decomposers to top-predators

In this review we compile results on interactions above and below ground and food web functioning in an arid environment at the Baza Basin, in the Iberian southeast. Our data reveal that herbivory is difficult to estimate in our system. Some herbivores (rabbits) and granivores (Messor ants) create nutrient and detritus-rich patches, with important effects on the diversity and abundance of species both above and below ground. Fluctuations of prey availability, especially those caused by changes in their circadian rhythms, provoke seasonal migrations and omnivory in predators. We also present experimental evidence of the effects of interactions between aboveground and belowground macroarthropods on litter degradation; belowground detritivores are responsible for a high percentage of ground surface litter decomposition. We demonstrate that belowground herbivores and decomposers can dramatically change aboveground multitrophic interactions. Finally, we identify the biotic and abiotic factors controlling aboveground and belowground macrofaunal distribution at a broad scale. We conclude that trophic interactions in this semi-arid area are numerous and complex with many of the interactions involving more than two or three organisms. The interactions between above- and belowground organisms added complexity to this system. These habitats in which organisms deal with extreme abiotic conditions promote odd interactions resulting in an increase of biodiversity. Finally, despite the large research effort devoted to understanding food web structure and dynamics in this area recently, our state of knowledge is still far from providing a complete picture of interactions and their implications in the regulation and functioning of the system.     

变化环境下基于跳跃分析的水资源评价方法

针对变化环境下的非一致性年径流序列,提出了基于跳跃分析的水资源评价方法.该方法假设非一致性年径流序列由相对一致的随机性成分和非一致的确定性成分两部分组成,采用水文变异综合诊断方法识别与检验年径流序列的变异点,并用变异前后序列均值之间的差值描述序列的确定性成分;根据时间序列分析的分解与合成理论,对年径流序列的随机性成分进行提取,采用有约束加权适线法对其进行频率计算;将确定性的预测值和随机性的设计值进行合成,得到过去、现在和未来不同时期年径流合成序列的频率分布.对无定河流域进行了实例验证,结果表明年径流量序列在1971年前后跳跃变异显著;多年平均地表水资源量在过去(1971年以前)、现在(2000年)和未来(2010年)三个时期的评价结果分别为:15.766×108 m3、10.228×108m3、10.228×108m3,未来与现在相同,而未来与过去相比减小约35.1%,这种情形对无定河流域水资源的开发利用极为不利.     

Linking pesticides and human health: A geographic information system (GIS) and Landsat remote sensing method to estimate agricultural pesticide exposure

Accurate pesticide exposure estimation is integral to epidemiologic studies elucidating the role of pesticides in human health. Humans can be exposed to pesticides via residential proximity to agricultural pesticide applications (drift). We present an improved geographic information system (GIS) and remote sensing method, the Landsat method, to estimate agricultural pesticide exposure through matching pesticide applications to crops classified from temporally concurrent Landsat satellite remote sensing images in California. The image classification method utilizes Normalized Difference Vegetation Index (NDVI) values in a combined maximum likelihood classification and per-field (using segments) approach. Pesticide exposure is estimated according to pesticide-treated crop fields intersecting 500 m buffers around geocoded locations (e.g., residences) in a GIS. Study results demonstrate that the Landsat method can improve GIS-based pesticide exposure estimation by matching more pesticide applications to crops (especially temporary crops) classified using temporally concurrent Landsat images compared to the standard method that relies on infrequently updated land use survey (LUS) crop data. The Landsat method can be used in epidemiologic studies to reconstruct past individual-level exposure to specific pesticides according to where individuals are located.     

两种典型荒漠植被区土壤微生物量碳的季节变化及影响因素分析

选取干旱区准噶尔盆地南缘梭梭和柽柳两类典型荒漠植被区的4种不同地表类型（冠层下、枯枝落叶层、地衣结皮覆盖区、裸地）,对其从6～10月份的土壤微生物量碳季节变化进行动态监测,并在此基础上进行了土壤微生物量碳与各影响因子之间关系的分析,旨在揭示干旱区土壤微生物量碳季节动态变化特征及其主要影响因子。结果表明：两类典型荒漠植被区的土壤微生物量碳均呈现明显的季节变化,但变化趋势并不一致。其中梭梭植被区4种地表类型下的土壤微生物量碳均在8月达到峰值;柽柳植被区冠层下土壤微生物量碳也在8月份达到最大值,但其他3种地表类型下的土壤微生物量碳却在8月降到最低值。通过土壤微生物量碳的影响因子分析表明两类不同植被区土壤微生物量碳与有机碳、全氮均为（P<0.05）正相关,此外,梭梭植被区与土壤湿度存在正相关,而柽柳植被区则与土壤总含盐量呈显著负相关,表明两类荒漠植被区土壤微生物对影响因子的响应并不完全相同。     

干旱区TM图像蚀变信息提取方法研究

围岩蚀变是成矿作用发生的重要标志之一,从遥感图像中提取蚀变信息是遥感找矿的难点和重要手段。遥感TM数据以其丰富的光谱和连续的空间信息被广泛地应用在地质找矿中,在分析TM影像数据的光谱特征的基础上,根据岩矿光谱特征和遥感信息提取理论,利用全波段主成份分析,选择主成份分析和比值增强、主成份分析相结合的直接主成份法分别对研究区进行了提取,并进行了对比分析和探讨,最终表明直接主成份分析在干旱区可以起到良好的应用效果。     

珠穆朗玛峰重力值的推估──兼论推估方法的基本原理

在山区 ,尤其是在有全球第三极之称的喜马拉雅山区 ,当相邻点间距不大时 ,如何利用这些点上的重力与地形 (高程 )数据推估待求点的重力值 ,这对难以攀登和不能用仪器观测的山峰很有意义。研究指出 ,在地形负荷的波长很短时 ,具有一定强度的地壳足以能够支撑这种负荷 ,因此 ,不能用Airy Heiskanen和Pratt Hayford局部补偿模型作重力推估 ;由于空间异常主要受地形起伏制约 ,因此借助于邻近重力点的地形 (高程 )作推估会得到满意的结果。基于这一思路 ,我们采用了 4种有关公式 ,有效地推估了第三极之巅珠穆朗玛峰顶上的重力值 ,该值为(976 970± 7)× 1 0 - 5m·s- 2 。这一结果为精确推求珠峰大地水准面和正高提供了必要的数据 ,若用均衡的方法来推估 ,则可能相差近 1 0 0× 1 0 - 5m·s- 2 。     

基于辐射的潜在蒸散量估算方法适用性分析

根据不同气候区4个站的历史数据,选取8种基于辐射的PET估算方法,以FAO56-PM法计算的PET作为参考值进行比较分析,最后用20 cm蒸发皿蒸发量对所有方法在不同气候区的适用性进行评价.其结果表明,采用初始参数时,Hargreaves法在不同气候区估算的逐月以及多年月平均PET误差均较小,其它方法则产生较大误差.校...     

Comparison of traditional wild plant knowledge between aboriginal communities inhabiting arid and forest environments in Patagonia, Argentina

The Mapuche people have a deeply rooted tradition of wild plant use for their subsistence. In this study we evaluated whether plant selection by the Mapuche is influenced by environmental constraints. Selection patterns of wild plant richness were compared in two Mapuche communities sharing the same traditions and beliefs but inhabiting different environments. Similarities and differences in the use patterns of wild medicinal and edible plants were quantitatively analyzed by using concepts derived from ecological theory. The Cayulef community is settled in the NW Patagonian (herbaceous) steppe while the Curruhuinca community is established near the Andean temperate forest, 100 km away from each other. Free-listing and semi-structured interviews were conducted with 32 families in Cayulef and 39 in Curruhuinca corresponding to 80% and 40% of each population, respectively. Data were analyzed by means of the Jaccard similarity index and statistical tests. The main results of this study showed that the home environment is a determinant factor that influences which plant species are utilized, as is the anthropic environment (with its high exotic species richness) in each community. However, similar patterns were found with respect to plant families, ways of utilization, plant parts and life forms utilized irrespective of where the communities are settled. In addition, in both populations, wild plant richness was significantly higher for medicinal than for edible species. Our results showed that the use of wild plants is primarily based on the utilization of species belonging to the nearest ecological environments that have both therapeutic and dietary functions.