Long-term effects of anthropogenic activities on semi-arid sand dunes

Semi-arid and arid sand dunes are considered sensitive ecosystems which may be affected by external disturbances. As many other semi-arid and arid ecosystems, their recovery ability is in the focus of many studies, whose consequences are important not only for the field of ecology but also for conservation and human welfare. I used aerial photograph analysis to study the effect of anthropogenic disturbance on dunesystem along the border between Israel and Egypt. The political changes in the border status over the last 40 years created a ‘natural’ experiment in the area, which enabled me to compare similar dune ecosystems under various anthropogenic regimes. The findings revealed a significant difference in recovery rate between the two border sides, and along the dune topography, which correspond with differences in human management (i.e. grazing and wood gathering). Nevertheless, a recovery process was detected in all parts of the dune ecosystem, even following long years of heavy anthropogenic use. The results of this study contribute to the ongoing debate about desertification processes, and indicate that some arid ecosystems may exhibit high resilience in the face of long-term exploitation.     

西北干旱半干旱区湿地特征与保护

西北干旱半干旱区湿地包括自然湿地和人工湿地两大类型。在干旱半干旱环境背景控制下发育的湿地具有独特的特点。由于自然与人为因素影响相互叠加,使得湿地退化过程加速和复杂化,表现为湿地面积减小,湿地咸化、沙漠化、盐碱化,湿地生态系统受损,生态调节功能降低。针对目前湿地退化现状,加强我国干旱半干旱地区湿地的保护、恢复及生态系统重建,已成当务之急。     

Soil salinity: A neglected factor in plant ecology and biogeography

This paper argues that soil salinity needs to be more broadly acknowledged as a driving factor in plant ecology—not only in the ecology of halophytes—in order to understand and make more accurate predictions for the impact of environmental change on biodiversity and vegetation patterns throughout the semi-arid world. It summarizes recent research on soil salinity and plant distributions in semi-arid environments throughout the world: there is empirical as well as experimental evidence that soil salinity, even at low levels, is an abiotic stress factor that influences vegetation patterns and diversification. Lines of evidence demonstrating salinity's potential influence as a selective agent in East Africa and North America are presented. The paper then synthesizes recent results from spatial ecology, plant and insect systematics and behavioral ecology, focusing on Australia, that support a role for salinity in evolutionary ecology of Acacia. On a shorter time scale, soil salinity may play a role in weed invasion and woody vegetation encroachment in Australia.     

干旱半干旱区农田土壤风蚀特征及参数化研究进展

干旱半干旱地区是中国的农业后备战略基地,然而近年来该地区农田土壤风蚀现象严重,沙/尘释放量显著增大,威胁农业的可持续发展和生态系统平衡。目前绝大部分的天气和气候模式仅考虑了沙漠地表起沙,忽视退化农田的土壤风蚀起沙,导致起沙通量模拟存在很大的不确定性。对20世纪50年代以来干旱半干旱区农田土壤风蚀起沙特征及参数化做了详细的分析总结,回顾并梳理了干旱半干旱区农田土壤风蚀观测和数值模拟的研究脉络以及存在的问题,为提高农田起沙的模拟精度提供了有效参考,对中国干旱半干旱区农田土壤风蚀防治、土地荒漠化治理以及理解未来土地利用改变对大气污染的影响具有重要意义。     

History and adaptation stories of the vertebrate fauna of southern Spain’s semi-arid habitats

Southern Spain’s semi-arid habitats are a Mediterranean ecosystem modelled mainly by historic factors which make them unique in comparison with North African deserts. Southern Spanish vertebrates have adapted to the recent emergence of semi-arid habitats in varying degrees of success. This paper reviews the current status of these terrestrial vertebrates (amphibians, reptiles, birds and mammals), their origins and their main features in relation to this biogeographic area. The vertebrate fauna of the semi-arid southeast of the Iberian peninsula differs widely from the one in the semi-arid Maghreb mainly because the former is composed by generalist vertebrates and much less so by species adapted to arid conditions. Moreover, a large fraction of the vertebrates in the semi-arid Iberia does not exploit the semi-arid areas but depends on riparian and human-managed habitats. The species diversity is rather low since only a small fraction of Palaearctic, European or Mediterranean species can adapt to the ecological limitations imposed by aridity and dwell in these semi-arid habitats. Such adaptations comprehend features like trophic plasticity, low morphological specialization, high dispersal ability, shortened life cycles and behavioural mechanisms to exploit the limited resources available. This paper identifies major conservation issues and proposes specific courses of action.     

沙质草原灌丛沙堆研究综述

灌丛沙堆是干旱、半干旱及半湿润荒漠地区风沙流遇到灌丛阻拦而堆积形成的一种地貌形态。普遍的研究表明灌丛沙堆是伴随人类不合理的土地利用和环境的变化而出现,是土壤风蚀和土地退化的标志,也是沙漠化的一种表现形式。灌丛沙堆在我国分布范围很广,但目前研究还不够深入。笔者主要阐述了国内外对灌丛沙堆形态、沉积物、演变及其环境意义等几个方面研究所取得的进展及其存在的争议,并提出了灌丛沙堆研究的发展趋势,以期引起国内对灌丛沙堆研究的关注。     

干旱荒漠土壤动物分布格局对降水脉动的响应研究进展

在干旱荒漠区,降水呈现强烈的脉动特征（即降水频率、强度及数量的高度变异性）,降水脉动变化对荒漠土壤动物的分布格局有显著影响。目前对降水脉动如何影响和调控荒漠土壤动物分布格局形成与维持的生态机制的认识非常有限。因此,深入开展干旱荒漠区降水脉动变化对土壤动物群落分布及多样性影响研究具有重要的科学意义。本文围绕“降水脉动驱动资源脉动影响土壤动物食物网结构”这一核心问题,重点从自然降水变化、冬季降雪变化和夏季降雨变化等方面对国内外的研究动态及最新研究进展做比较系统的评述。在此基础上,探索干旱荒漠生态系统响应降水变化研究中应重点关注的几个前沿科学问题,这可为中国干旱荒漠生态系统生物多样性保护管理提供科学依据,促进荒漠生态系统生物多样性保育理论、资源脉动生态学理论和研究方法的发展。     

隐花植物对UV-B辐射响应和适应机制的研究进展

 隐花植物是指不产生种子的植物,是我国干旱、半干旱地区主要表面特征——生物土壤结皮的组成成分,并在其中扮演着独特而重要的生态作用。隐花植物对环境因子变化的响应和适应能力大小对整个生态系统稳定性具有重要影响。因此,有关增强UV-B辐射对隐花植物影响的研究已成为目前UV-B辐射研究领域的发展趋势和热点之一。通过系统地综述国内外有关隐花植物对UV-B辐射响应和适应机制研究方面的进展,分析了研究趋势,讨论了目前该领域研究的一些不足并对未来发展提出了展望,以期促进隐花植物的研究,加深对我国干旱、半干旱区隐花植物在应对UV-B辐射增强的响应和适应机制的认识。     

皇甫川流域降水和人类活动对径流量变化的贡献率分析——累积量斜率变化率比较方法的提出及应用

随着全球或区域气候的变化,加上渐强的人类活动的影响,世界上一些河流的径流量发生了明显减小的变化趋势,这在干旱及半干旱地区的河流中尤其明显。在我国,北方干旱及半干旱地区河流的径流量的减小已经引起了严峻的生活及生态方面的问题。因此查明流域径流量的变化特征、趋势及分析其原因,是流域管理中面临的重要科学问题。该研究以黄河中游一级支流皇甫川流域为例,利用1960-2008 年的数据资料,采用累积距平方法、年际累积量方法,分析了该流域径流量和降水量的变化趋势,识别出径流量变化过程中1979 和1998 为其两个突变年份,而降水量变化过程中仅存在唯一的突变年份1979。利用统计分析法分别分析了1960-1979、1980-1997 和1998-2008 三个时期的累积径流量与年份之间的线性关系,以及1960-1979、1980-2008 两个时期累积降水量与年份之间的线性关系。采用本文提出的新的计算方法——累积量斜率变化率比较方法,以1960-1979 为基准期,在不考虑蒸散总量的影响时,计算得出皇甫川流域径流量减小的降水量和人类活动的相对贡献率在1980-1997 年间分别为36.43%和63.57%,在1998-2008 年间分别为16.81%和83.19%。该研究结果揭示了皇甫川流域近半个世纪以来径流量的变化趋势及其主要影响因素的贡献率,对于该流域未来水资源的开发利用具有重要指导作用。同时,所提出的定量研究方法可以应用在干旱—半干旱地区河流径流量变化及其影响因素的定量评估中。     

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.     

The MaB Reserve of Ñacuñán,Argentina: its role in understanding the Monte Desert biome

Temperate and semi-arid regions of Argentina are undergoing rapid habitat conversion as a result of several human activities (i.e. grazing, logging, agriculture, etc.). These arid ecosystems contain many endemic species and have played an important role in the evolution of South American biota. The Man and Biosphere Reserve of Ñacuñán (12,800 ha) is located in the central region of the lowland Monte Desert. The reserve is a stand within a highly disturbed matrix characterized by deforestation (i.e. mesquite,Prosopis)and overgrazing. Major vegetational and animal communities recovered after the reserve was fenced in 1972, and Ñacuñán thus provides critical data describing the recovery of biotic and abiotic components of the Monte Desert when anthropogenic assaults are minimized. Indeed, the Reserve of Ñacuñán protects many distinctive habitats of the Monte Desert, including mesquite forest, or algarrobal, and several representative animals of the South American biota (i.e. tinamous, rhea, marsupials, edentates and caviomorph rodents). Several research projects on community ecology, herbivory, disturbances, ecology and ecophysiology have been or are being developed in the reserve. Although the town of Ñacuñán lies within the reserve, the link between the research community and the local people has not been strong, persistent or effective. The reserve is the most important site in Argentina for monitoring the ecological health of the Monte Desert and for developing indicators of desertification. Its potential is great for long-term ecological research and for strengthening the infrastructure of science. Sustainable development in the next millennium requires integrating the activities of the research, local people, ranch landowners and governmental sectors so as to infuse science-based proposals into management and conservation initiatives.     

生态系统稳定性若干问题研究评述

稳定性是生态系统重要的特征之一。生态系统稳定性具有很多的概念,但目前生态学家较多地将系统受到干扰时抵抗偏离初始状态的能力和受到干扰后返回初始状态的能力作为生态系统稳定性的定义。对稳定性机制的解释也有很多假设,其中比较重要的有多样性或复杂性理论,反馈控制理论,食物网理论,冗余理论等。本文对这几种理论主要内容做了较为详细的综述。并对动物群落和植物群落稳定性测度的常用方法做了介绍。指出了稳定性评价中存在的一些问题,诸如层次划分比较含混,项目选择不具代表性,缺少纵向和横向比较的可能性等问题。归纳了稳定性研究的野外生态学方法和数学生态学方法。特别强调了干旱区、半干旱区生态系统稳定性研究的重要性。对稳定性研究的发展趋势做了展望和预测。     

模拟增温和改变降雨频率对干旱半干旱区土壤呼吸的影响

温度和降水是干旱半干旱区土壤呼吸的重要扰动因子,全球气候变化导致的未来干旱半干旱区增温和降水变率增大对土壤呼吸有着重要影响.研究通过人工设置P16×2.5mm、P8×5mm、P4×10mm、P2×20mm、P1×40mm的降雨频率梯度和增温2℃左右的控制试验,探讨不同降雨频率和增温处理对干旱半干旱区土壤呼吸的影响,以及...     

科尔沁沙质草甸土壤微生物数量的垂直分布及季节动态

通过对中国农牧交错带科尔沁沙质草甸土壤微生物数量的垂直分布及其季节动态的研究分析表明:(1)微生物总数、细菌和放线菌数量均表现出与降雨量同步的季节动态,即6月份较5月份有所减少,7月份增至最多,7月份以后微生物数量逐渐下降,真菌则表现出从5月份到8月份一直增加,9月份开始回落;(2)土壤微生物具有明显的垂直分布差异.细菌和放线菌的垂直分布表现出随土壤深度增加逐渐减少的趋势,真菌数量表层最高,20 cm以下变化不够规律;(3)土壤微生物的层化比率均大于2(5月份放线菌除外);(4)不同土壤生态因子对微生物的影响不同,相同因子对不同微生物类群的影响也不相同.细菌受水分影响较大,真菌与地温的变化趋势相近,放线菌与水热条件的共同作用有关.土壤养分(有机碳和全氮)与微生物数量呈显著的正相关.     

榆林地区脆弱生态环境的景观格局与演化研究

作为干旱半干旱区农牧交错带的典型代表,榆林地区在自然地理上有其独特的空间分布格局,在生态上具有显著的脆弱生境特征和演化规律。本文运用景观生态学的基本理论与方法,选取分维数、形状指数和景观优势度等指标,对该区脆弱环境的景观格局进行了分析,同时对诱发该区景观生态演化的因素进行了定量诊断,并对区域生态环境的景观过程进行了探讨。     

我国南方山地和丘陵的荒漠化问题

沙漠化问题及其带来的巨大危害与后果已经引起人们的关注。然而, 我国南方许多山地与丘陵区正在广泛、迅速发展的山地荒漠化和谷地沙石化过程, 同样不能忽视。它使这些地区的自然环境变劣、生态平衡严重失调, 土地退化和生产能力衰退或枯谒, 最终导致整个自然环境向恶性循环发展的严重恶果。我国南方山地荒漠化和谷地沙石化的土地面积估计约1.0-1.3亿公顷。主要分布在云南、四川、贵州、江西等十多个省(区), 其中云南的小江流域, 四川的金沙江河谷及岷江上游; 广西的南流江一带, 江西的兴国县和鄱阳湖区等尤为严重和典型。我国南方山地荒漠化的主要原因是人类不合理的经济活动所引起, 而不利的气候和特殊的地质、地貌条件促使其不断加剧和扩展之势。     

Spatial associations between NDVI and environmental factors in the Heihe River Basin

Journal of Geographical Sciences - The Heihe River Basin is located in the arid and semi-arid regions of Northwest China. Here, the terrestrial ecosystem is vulnerable, making it necessary to...     

Use of large Acacia trees by the cavity dwelling Black-tailed Tree Rat in the Southern Kalahari

Recent extensive harvesting of large, often dead Acacia trees in arid savanna of southern Africa is cause for concern about the conservation status of the arid savanna and its animal community. We mapped vegetation and nests of the Black-tailed Tree Rat Thallomys nigricauda to assess the extent to which the rats depend on particular tree species and on the existence of dead, standing trees. The study was conducted in continuous Acacia woodland on the southern and eastern edge of the Kalahari, South Africa. Trees in which there were tree rat nests were compared with trees of similar size and vigour to identify the characteristics of nest sites. Spatial analysis of tree rat distribution was conducted using Ripley's-L function. We found that T. nigricauda was able to utilize all available tree species, as long as trees were large and old enough so that cavities were existing inside the stem. The spatial distribution of nest trees did not show clumping at the investigated scale, and we therefore reject the notion of the rats forming colonies when inhabiting continuous woodlands. The selection of a particular tree as a nest site was furthermore depending on the close proximity of the major food plant, Acacia mellifera. This may limit the choice of suitable nest sites, since A. mellifera was less likely to grow within a vegetation patch containing a large trees than in patches without large trees.     

Comparison of soil bacterial communities associated with actinorhizal, non-actinorhizal plants and the interspaces in the sclerophyllous matorral from Central Chile in two different seasons

The spatial heterogeneity of resources in desert and semi-arid shrubland appears to be important in determining higher soil bacteria abundance around plants than in soil without plant cover. Thus, these bacterial communities could be important contributors to nutrient cycling in arid ecosystems. Bacterial diversity from Chilean sclerophyllous matorral was determined by Terminal Restriction Fragment Length Polymorphism (T-RFLP). Soil samples associated with the actinorhizal plant Colletia hystrix, non-actinorhizal plants and interspace soil without plant cover, were collected in May and October. The non-actinorhizal and interspace soil differed significantly in their potassium content in May and pH in October. The T-RFLP analysis revealed differences in the bacterial community structure from the different habitats. The soil bacterial communities associated with plants were the most similar, whereas the interspace soil community differed in both sampling times. The factors that best explained the groupings were potassium and pH. The greatest diversity was observed in the interspace soil. The Microbial Community Analysis showed a significant proportion of T-RFs identified as Firmicutes and Proteobacteria. Likewise, spatial and temporal differences were observed in the main groups' abundance. The dominance of Firmicutes suggests that the sclerophyllous matorral could be a different ecosystem to other arid and semi-arid soils with respect to the bacterial community structure.