干旱半干旱地区河流健康评价指标研究分析

干旱半干旱地区是生态系统和水资源系统最脆弱的地区之一, 也是降水变率最大的地区, 对这一地区河流健康的研究, 可为生态系统的管理与恢复等提供非常有价值的见解。因此, 确定影响干旱半干旱地区流域健康的主要因素、制定可快速监测与检测其健康状况的生态指标, 并对其发展趋势进行诊断与预测, 随时采取可行的干预措施是至关重要的。以河流健康的定义与评价内涵、评价指标研究态势为根本, 在分析干旱半干旱地区河流的生态系统特征、河流关键生态环境机理及表现、社会-生态-文化系统长期相互影响的基础上, 从水资源、植被、物理化学特性、社会经济等方面出发, 提出了适用于干旱半干旱地区河流健康评价的关键控制性指标。     

基于空间小波变换的生态地理界线识别与定位

为了提高生态地理分界线识别和定位的客观性,探讨了通过空间小波变换获取多尺度模极大值定位过渡带的方法.以NDVI和降水作为小波多尺度分解的对象,应用db3小波核函数分别对49条样带的模极大值进行了多尺度检测,并在GIS中确定其地理坐标.研究结果表明:识别半干旱半湿润生态地理分界线的最佳空间尺度为20～40 km,小于这一尺度定位过程容易受到局部地表覆被因素如城市区域或地形的影响,大于这一尺度由于要素被过度平滑,造成定位不准;从定位点的聚集度分析,NDVI的定位效果好于降水,特别是在较大空间尺度上.而与综合自然地理区划方案中的半干旱半湿润分界线比较,从定位点的方向性、平均最短距离以及均衡度三项指标综合判断,小波变换对于降水过渡带的定位优于对NDVI的定位.研究证实,空间小变换与GIS结合是提高生态地理分界线识别与定位科学性的重要途径,是对专家系统划分界线方法的有力补充和完善.     

水分亏缺对作物的伤害

全世界干旱、半干旱地区的总面积约占总陆地面积的1/3。中国是世界上主要的干旱国家之一,全国干旱、半干旱地区约占总国土面积的一半左右。干旱是制约我国西北和整个北方地区农业生产发展的基本自然因素,其他地区在作物生长季节也发生不同程度的干旱危害。研究作物水分胁迫及其伤害生理,不仅在理论上而且在实践中都有重要意义。     

生态原则在沙漠化土地整治中的应用——以内蒙古东部干草原地区为例

一、引言土地沙漠化是本世纪六十年代以来引起人们十分关注的干旱、半干旱地区环境退化问题。我国沙漠化土地约为17万平方公里(其中约5万平方公里为近半个世纪内形成),分布在新疆、内蒙古、陕西、辽宁等12个省(区)的207个县(市、旗),涉及约3500万人口,尤以半干旱草原地带及荒漠草原地带为严重。沙漠化是干旱、半干旱地区生态环境退化的     

1951—2018年中国年降水量及气象干旱的时空变异

探求降水量及干旱时空变化特征及规律是当前水文学研究的重要课题。基于中国619个气象站1951—2018年的降水量数据,采用距平百分率法和Morlet小波分析等方法,揭示年降水量及干旱的时空变异。结果表明: 研究期间,中国年降水量空间上呈东南至西北阶梯递减的特征,多年降水量变化剧烈程度反之;地势二、三阶梯分界线左右区域降水量呈下降趋势,且多于20世纪60—70年代发生突变,其余地区呈上升趋势,大多数突变发生于20世纪90年代;温带大陆和温带季风气候区降水量主周期小。20世纪60年代至21世纪10年代,中国干旱区面积减少,半干旱区面积增加,特别是近10年干旱和半干旱区面积减小,半湿润区面积增大。在30°—40° N之间发现一条干旱南北差异分界线,分界线以北干旱次数远多于以南;干旱的主体区域在年代际的转移方向为西北中部→华北南部→华北北部,发生次数及分布范围逐渐减小。     

不同作物在不同土壤水分条件下的耗水特性

本文系用盆裁法,对在干旱半干旱地区种植的八种主要作物——玉米、高粱、谷子、糜子、春麦、扁豆、胡麻、苜蓿等在适宜水分,轻度干旱、中度干旱、严重干旱、极严重干旱等五种土壤水分条件下的耗水特性进行了系统研究,比较了它们在耗水特性上的差异,并寻找了这种差异与需水日变化的关系,为其在干旱半干旱地区的合理布局与结构及其提高水分利用效率、旱作栽培提供了科学依据。     

秦岭山地生态分界线的论证

山地自然生态分界线,实际为一条生态过渡带。分界线位置的准确划分,有助于把握现代气候-植被-土壤的敏感变化特征,也是指导当地大农业生产的基础依据。秦岭山地长期以来被认为是中国东部重要的南北生态分界线,即亚热带和暖温带的分界线。但对该界线的具体位置,历来存在着北坡、分水岭和南坡3种争议。根据作者多年的工作积累和对相关问题的思考,以文献评析为基础,以气候-植被参数计算结果为依据,并通过对秦岭山地不同区域植物区系和植被垂直带谱已有研究结果的比较分析,从中得出如下主要结论:(1)根据秦岭地区气候-植被参数等值线的分布,整个秦岭山地都应属于暖温带,这一结论可与国际有关研究相互接轨。(2)根据对秦岭不同区域植物区系调查结果的比较分析,秦岭南坡大部分区域都应属于暖温带,而南麓海拔1000m等高线附近很可能是暖温带的南缘。(3)根据对秦岭南北坡植被垂直带谱的比较分析,南麓海拔1000m等高线应该是一条重要的生态分界线。综合来看,将秦岭山地的南北分界线放在南坡海拔1000m附近比较适宜。上述归纳研究所获结论,将通过在秦岭山地深入开展现代"3S"技术支撑下的植被、土壤、气候等生态与地理方面的综合研究,最终得到完全验证。     

一种从土壤生物结皮中有效提取DNA的方法

在干旱、半干旱地区稀疏的高等植被间, 常有一层生物土壤结皮。       

干旱地区农业生态建设战略探讨

我国广大的干旱和半干旱地区,在国民经济建设中具有重要的战略意义。而干旱和半干旱地区地处边陲,交通不便,因此农业生态建设战略的制定对该地区的全面开发至关重要。本文仅就我国最典型的干旱地区新疆维吾尔自治区为研究对象,对干旱地区农业生态建设作初步探讨。     

农业非点源污染研究现状与发展趋势

水危机已成为世界上最引人关注的问题之一。无论是发达国家,还是发展中国家,都已经或即将面临着这一危机。而在干旱与半干旱地区尤为紧迫。引起水危机的主要原因有二：一是从长远来讲,水资源是有限的,而目前由于世界人口持续增加引起对水资源需求的膨胀使得这一危机加...     

干旱半干旱区生态系统凝结水的影响因素及其作用研究进展

凝结水是干旱半干旱生态系统重要的水分补给来源,对于维持生态系统功能具有重要意义。综述了干旱半干旱生态系统气象条件、地形环境和植被属性等因素对凝结水形成的影响,以及气候和环境变化对凝结水产量的影响机制。在此基础上,进一步从植被生长、生物土壤结皮、小型动物、微生物和地表水热平衡过程等方面,探讨了凝结水产量变化对干旱半干旱生态系统组成和过程的重要作用。最后对未来相关研究提出以下建议：（1）增加长时间序列的凝结水观测数据分析,（2）系统探讨凝结水对干旱半干旱区生态系统功能的综合影响,并（3）完善气候变化背景下凝结水与生态系统关系的相关研究。本文旨在对该领域的未来研究提出综述、建议和展望。     

Effects of nitrogen addition and mowing on nitrogen- and water-use efficiency of Artemisia frigida in a grassland restored from an abandoned cropland

氮添加和刈割对内蒙古弃耕草地冷蒿氮和水分利用效率的影响 在氮和水分限制的区域，植物氮利用效率(NUE)和水分利用效率(WUE)决定了它们在群落中的竞争优势。冷蒿(Artemisia frigida)是半干旱草地重度退化的先锋物种，在不同退化程度的草地中具有不 同的优势度，经常被认为是退化草地群落演替的指示物种。退化草地恢复过程中，氮添加和割草如何影响冷蒿的NUE和WUE尚不清晰。以内蒙古多伦县弃耕草地为研究对象，选取两个不同群落斑块(禾草和冷蒿为优势物种的斑块)，经过长期(2006–2013)氮添加和刈割(对照、氮添加、刈割、氮添加+刈割)处理后，研究冷蒿的NUE (叶片碳氮比)和WUE (叶片碳同位素，δ¹³C)对氮添加、刈割及其交互作用的响应； 结合植物和土壤的碳、氮同位素(δ¹³C和δ¹⁵N)及碳、氮库探究退化草地恢复过程中植物的资源利用策略及其机制。研究结果表明：(1)氮添加对冷蒿的WUE没有显著影响(P > 0.05)，但NUE 在禾草和冷蒿斑块 中分别显著降低了42.9%和26.6% (P < 0.05)；(2)植物对不同氮源(NH₄₊或NO_3-)的利用会引起植物和土壤δ¹⁵N的分馏，研究表明叶片和土壤的δ¹⁵N与NUE呈现相反的变化趋势，因此冷蒿的NUE对氮添加的响应与不同氮源的利用有关；(3)刈割不影响冷蒿的NUE (P > 0.05)，但在禾草斑块，冷蒿的WUE在刈割处理下显著提高了2.3% (P < 0.05)；(4)在禾草斑块，氮添加减缓了割草对冷蒿WUE的促进作用；(5)结构方程模型显示，土壤含水量直接或间接的调控着冷蒿的WUE和NUE。综上所述，在禾草斑块，氮添加+刈割处理维持较低的NUE和WUE，不利于冷蒿对资源的竞争，进一步降低其优势度，这也预示着氮添加+ 刈割处理会促进退化草地的恢复。     

Water and energy economy of an omnivorous bird: population differences in the Rufous-collared Sparrow (Zonotrichia capensis)

We investigated the intraspecific variation in basal metabolic rate (BMR) and total evaporative water loss (TEWL) in the omnivorous passerine Zonotrichia capensis from two populations inhabiting regions with different precipitation regimes and aridity indices. Values of TEWL in birds from the semi-arid region were significantly lower than those found in sparrows from the mesic region. TEWL in birds from the semi-arid site was 74% of the expectation based on body mass for passerines from mesic areas and similar to the allometric expectation for passerines from arid environments. In sparrows from the mesic area, TEWL was higher than predicted by their body mass for passerines from arid environments (133%), but very close (97%) to the expectation for passerines from mesic areas. BMR values were 25% lower in sparrows from the semi-arid region. The lower TEWL and BMR of birds from the semi-arid region may be a physiological adjustment that allows them to cope with fewer resources and/or water. We propose that the lower endogenous heat production in birds from the semi-arid environment may decrease their water requirements.     

Spatial Patterns and Natural Recruitment of Native Shrubs in a Semi-arid Sandy Land

Passive restoration depending on native shrubs is an attractive approach for restoring desertified landscapes in semi-arid sandy regions. We sought to understand the relationships between spatial patterns of native shrubs and their survival ability in sandy environments. Furthermore, we applied our results to better understand whether passive restoration is feasible for desertified landscapes in semi-arid sandy regions. The study was conducted in the semi-arid Mu Us sandy land of northern China with the native shrub Artemisia ordosica. We analyzed population structures and patterns of A. ordosica at the edges and centers of land patches where sand was stabilized by A. ordosica-dominated vegetation. Saplings were more aggregated than adults, and both were more aggregated at the patch edges than at the patch centers. At the patch edges, spatial association of the saplings with the adults was mostly positive at distances 0.3–6.6 m, and turned from positive to neutral, and even negative, at other distances. At the patch centers, the saplings were spaced almost randomly around the adults, and their distances from the adults did not seem to affect their locations. A greater number of A. ordosica individuals emerged at the patch edges than at the patch centers. Such patterns may have resulted from their integrative adjustment to specific conditions of soil water supply and sand drift intensity. These findings suggest that in semi-arid sandy regions, native shrubs that are well-adapted to local environments may serve as low-cost and competent ecological engineers that can promote the passive restoration of surrounding patches of mobile sandy land.     

Cellular Responses,Osmotic Adjustments,and Role of Osmolytes in Providing Salt Stress Resilience in Higher Plants: Polyamines and Nitric Oxide Crosstalk

Journal of Plant Growth Regulation - Salinity stress is a chief abiotic hindrance affecting crop productivity and yield particularly in arid and semi-arid regions across the globe. Plants have...     

Phenotypic and genetic diversity in <Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis> and <Emphasis Type="Italic">S. medicae</Emphasis> from drought and salt affected regions of Morocco

Background  

Sinorhizobium meliloti and S. medicae are symbiotic nitrogen fixing bacteria in root nodules of forage legume alfalfa (Medicago sativa L.). In Morocco, alfalfa is usually grown in marginal soils of arid and semi-arid regions frequently affected by drought, extremes of temperature and soil pH, soil salinity and heavy metals, which affect biological nitrogen fixing ability of rhizobia and productivity of the host. This study examines phenotypic diversity for tolerance to the above stresses and genotypic diversity at Repetitive Extragenic Pallindromic DNA regions of Sinorhizobium nodulating alfalfa, sampled from marginal soils of arid and semi-arid regions of Morocco.     

Callus culture and plantlet regeneration in date palm (Phoneix dactylifera L.): an important horticultural cash crop for arid and semi-arid horticulture

Physiology and Molecular Biology of Plants - Phoneix dactylifera L. commonly called date palm is a highly valuable horticultural cash crop for arid and semi-arid regions. The availability of...     

Effect of Water Stress on Photosynthesis,Chlorophyll Fluorescence Parameters and Water Use Efficiency of Common Reed in the Hexi Corridor

Russian Journal of Plant Physiology - Water stress is the major environmental stress that affect agricultural production worldwide, especially in arid and semi-arid regions. This research...     

Silent metabolism and not-so-silent biological activity: possible molecular mechanisms of stress response in edible desert legumes

Journal of Plant Biochemistry and Biotechnology - In the arid/semi-arid regions of India, there are many legumes often growing in the wild like Prosopis cineraria, Cyamopsis tetragonoloba and...     

Geographical divergence of species richness and local homogenization of plant assemblages due to climate change in grasslands

Biodiversity and Conservation - In arid and semi-arid regions worldwide, grassland plant species richness is highly sensitive to climate change. Studies assessing local grassland richness patterns...