Research advances on drought resistance mechanism of plant species in arid zones of China

Drought and shortage of water resources, which restrict the economy, society development and environmental protection, are key factors in arid zones of China. In the arid zones of Western China, researching plant drought resistance mechanism, selecting plant species with higher drought resistance, and developing water-saving techniques, are important for environmental improvement and economic development. This paper reviews research advances on drought resistance mechanism of plant species, based on research of morphological, physiological, and ecological adaptation mechanism of plant species under drought stress, such as anatomical structure of root systems and leaves, photosynthesis, antioxidant enzyme system, malondialdehyde (MDA), osmotic adjustment, endogenous hormone, drought-induced proteins and δ¹³C. Finally, this paper points out the key field of future research.     

Seed biology of Australian arid zone species: Germination of 18 species used for rehabilitation

Revegetation of disturbed land, particularly in arid environments, is often hindered by low seedling establishment. Information on seed biology and germination cues of keystone species is lacking, particularly in arid Australia; a major zone for mining developments. This study investigated seed characteristics and germination of 18 common species required for rehabilitation of disturbed areas at Shark Bay Salt in the Shark Bay World Heritage Area, Western Australia. Untreated seeds of seven species (Aphanopetalum clematideum, Atriplex bunburyana, Austrostipa elegantissima, Melaleuca cardiophylla, Pembertonia latisquamea, Rhagodia baccata, Salsola tragus) exhibited high germination percentages. Seeds of two species (Acacia tetragonophylla, Stylobasium spathulatum) had low imbibition, which increased with hot-water treatment, hence require scarification for germination. Gibberellic acid, smoke water and karrikinolide (a butenolide isolated from smoke) substantially increased germination percentages of three species (Anthocercis littorea, Diplolaena grandiflora, Solanum orbiculatum). Seeds of the remaining six species (Dioscorea hastifolia, Eremophila oldfieldii, Nitraria billardierei, Ptilotus exaltatus, Thryptomene baeckeacea, Zygophyllum fruticulosum) had low germination percentages regardless of treatment. Most species germinated equally well at 26/13 °C and 33/18 °C, however seven species had improved performance at 26/13 °C. This study is significant to land managers and conservation agencies with an interest in optimising germination of arid zone seeds for restoration.     

中国北方干湿过渡区生态系统生产力的气候变化风险评估

气候变化风险是人类社会发展面临的严峻挑战,评估识别对气候波动响应敏感且复杂的干湿过渡区生态系统所面临的气候变化风险是一个重要科学问题,对区域气候治理和风险管理具有科学意义.本文利用参与耦合模式比较计划第五阶段(CMIP5)的多气候模式多情景数据,通过改进和验证Lund-Potsdam-Jena(LPJ)动态全球植被模型...     

Intensified risk to ecosystem productivity under climate change in the arid/humid transition zone in northern China

Assessing the climate change risk faced by the ecosystems in the arid/humid transition zone(AHTZ) in northern China holds scientific significance to climate change adaptation. We simulated the net primary productivity(NPP) for four representative concentration pathways(RCPs) using an improved Lund-Potsdam-Jena model. Then a method was established based on the NPP to identify the climate change risk level. From the midterm period(2041–2070) to the long-term period(2071–2099), the risks indicated by the negative anomaly and the downward trend of the NPP gradually extended and increased. The higher the scenario emissions, the more serious the risk. In particular, under the RCP8.5 scenario, during 2071–2099, the total risk area would be 81.85%, that of the high-risk area would reach 54.71%. In this high-risk area, the NPP anomaly would reach –96.00±46.95 gC·m~(-2)·a~(-1), and the rate of change of the NPP would reach –3.56±3.40 gC·m~(-2)·a~(-1). The eastern plain of the AHTZ and the eastern grasslands of Inner Mongolia are expected to become the main risk concentration areas. Our results indicated that the management of future climate change risks requires the consideration of the synergistic effects of warming and intensified drying on the ecosystem.     

干旱区城镇主导产业选择模型及评价体系分析与实证——以新疆鄯善县为例

根据干旱区城镇区域的特色,干旱区城镇在进行主导产业的选择时必须遵循生态保护原则.依据此原则,以新疆干旱区城镇鄯善县为例,在数据较易获取的基础上,建立了适用于干旱区城镇进行主导产业选择的Weaver-Thomas模型及其评价的指标体系,运用MATLAB软件进行计算.结果表明:石油和天然气开采业、黑色金属冶炼及压延加工业为...     

Physical, chemical and faunal characteristics of a perennial stream in arid northern Oman

A study of a 1·5 km stretch of a perennial stream in arid northern Oman describes the physical, chemical and faunal characteristics of riffles, runs and pools. Air temperature seems to influence invertebrate recruitment. Flooding is the most important catastrophic event that alters the physical and chemical environment. Current velocity and substrate composition are also probable factors affecting the community structure. All other chemical conditions except nitrate (–N) were significantly similar in all biotopes. Three vertebrate and 33 invertebrate taxa were recorded. The low faunal diversity is a reflection of a physically controlled system.     

Influence of multipurpose trees on agricultural crops in arid regions of Haryana, India

The effects of multipurpose trees on the productivity of agricultural crops were studied in the arid regions of Haryana. In one of the experiments, wheat was grown on irrigated farms having scattered trees ofDalbergia sissoo, Azadirachta indica, Prosopis cinerariaandAcacia nilotica. Data of wheat yield for each tree species at different distances (1, 3, 5, and 7 m) and four directions (East, West, North and South) from the tree bases and control (no trees) were collected. Results indicate thatAzadirachta indicaandProsopis cinerariadid not produce any significant difference in the wheat yield while the other two species (Dalbergia sissooandAcacia nilotica) gave a reduction in yield.A. niloticahad a more significant and prominent effect and a reduction of 40 to 60 % wheat yield was observed.Dalbergia sissooreduced yield by 4 to 30 % but the reduction was only up to a distance of 3 m. In general, the impact of trees on productivity was observed up to 3 m distance and there was little, if any, impact up to 5 m and almost no impact at 7 m.In another experiment,D. sissoo(18-years-old) was raised as windbreak and productivity of cotton was assessed. The tree belt reduced the wind speed by 15 to 45 %, depending on season and wind speed. The influence of trees on cotton yield was observed to be negative up to 2H (36 m), where H is tree height, i.e. 18 m. Cotton productivity was observed to be maximum between 2H and 5H. Depending upon orientation of tree belt, the increase in cotton yield was found to be 4 to 10 %.     

温带干旱地区近地层空气二氧化碳浓度的变化特征

选定我国温带干旱地区的四种植被类型:典型草原(内蒙古)、荒漠草原(宁夏)、榆树林(宁夏)和油松林(宁夏)为观测样地,观测研究了近地层空气CO2浓度的变化特征,结果表明:(1)干旱地区近地层空气CO2年平均浓度为323.49±21.36×10-6,是一种自然状态下的本底数据,其平衡受当地植被覆盖程度和种类控制.(2)近地层空气CO2浓度随植被类型不同存在差异,灌草丛生的榆树林最低297.92±15.56×10-6,裸露的荒漠草原最高331.82±19.17×10-6,植被的种类控制着地表面空气CO2浓度的大小,灌木杂草有利于吸收近地层空气的CO2,裸露的地表不利于CO2浓度的吸收和调节,植被在空气组成平衡过程中,起着"汇"的作用,尽管干旱地区植被稀少.(3)干旱地区近地层空气CO2浓度存在明显的季节变化,11月份浓度最高336.54±27.12×10-6,7月份最低305.05±15.45 × 10-6;呈"S"型曲线变化趋势,这种季节变化十分有利于调节地表空气CO2的浓度.(4)干旱地区近地层空气CO2浓度存在日变化,变化范围261.0×10-6～384.0×10-6,均值为323.5×10-6.一天中,平均CO2浓度最低时间在下午的16:00时,最高时间是在半夜0:00时.变化趋势呈"沟谷"状,两头高,中间低.(5)在人烟稀少的温带干旱地区,植被、土壤和气候相互作用,调节和控制差近地层空气CO2的浓度变化.     

干旱区典型流域近30年土地利用/土地覆被变化的分形特征分析——以玛纳斯河流域为例

利用1976、1989、2005年三期遥感影像,运用GIS和分形理论研究干旱区典型流域——玛纳斯河流域近30年的土地利用/土地覆被变化的复杂性和稳定性。结果表明:玛纳斯河流域各时段的土地利用/土地覆被类型分布具有分形结构,土地利用/土地覆被类型形状复杂性和斑块的稳定性波动变化,1976、1989、2005年三时期的各种土地利用/土地覆被类型总平均分维值分别为1.394 0、1.363 4和1.389 9。总平均稳定性指数分别为0.606 0、0.636 6、0.610 1。三期土地利用/覆被类型平均稳定性排序为:沙地>未利用土地>居民点工矿用地>水域>林地>草地>耕地>盐碱地。耕地、林地、草地、盐碱地稳定性相对较差。通过对流域土地利用/土地覆被类型变化复杂性和稳定性的研究,可以为政府协调水土开发和调整土地利用结构提供支持。     

Use of three widely spread plant species from American arid regions for exploration of tin mineralizations

The ability to accumulate trace element contents of three plant species of widespread occurrence in the semi-arid regions of middle and southern South America (Larrea cuneifolia Cav., Cercidium praecox (Ruiz & Pav.) Harms, and Bulnesia retama (Gillies ex Hook. & Arn.) Griseb.) has been considered in order to determine their application to the exploration of tin mineralizations. Two of the three studied species can be considered as suitable for biogeochemical exploration (L. cuneifolia and C. praecox). Concentrations of As, Cd, and Mo reflect the known tin mineralization. L. cuneifolia and B. retama showed the highest and lowest trace element accumulation rates. Only zinc is preferentially accumulated in C. praecox. In addition, L. cuneifolia and C. praecox could be of environmental interest in As-bearing areas due to the accumulation capability for such element.     

Is the analysis of plant community structure better than common species-diversity indices for assessing the effects of livestock grazing on a Mediterranean arid ecosystem?

Grazing in arid Mediterranean ecosystems brings about changes in species diversity, but the best way to measure such changes is unclear. In this study we compared various methods in order to identify indicators that might be useful for the management and conservation of grazed arid Mediterranean ecosystems.Changes in community structure and composition were compared along a previously studied grazing gradient in Cabo de Gata-Nijar Natural Park. Plant diversity was measured by calculating diversity (Shannon information index), evenness (Pielou index) and richness (species number). Rarefaction curves were used to measure plant species richness and the results were compared with traditional richness values. Community structure was measured as the percentage of bare ground and the coverage of overall perennial grasses, Stipa tenacissima L., perennial shrubs and annual plants. Our results showed that the proportion of bare ground, the cover of perennial shrubs and the relative abundance of S. tenacissima are good indicators of grazing effects on vegetation. Overall plant community structure was more sensitive to the grazing gradient than were the diversity indices. Finally, the adequacy of standardized methods for comparing species richness (i.e. rarefaction curves) along a grazing gradient are discussed.     

Short-term effects of shrub control on two different plant communities in Argentina

The aim of this work was to study the effect of controlling jarilla (Larreaspp.), nonforage shrubs for livestock, on two plant communities with different forage production in the arid mid-west of Argentina. Total vegetation cover, forage species cover and carrying capacity were determined during three growing seasons, for cleared and uncleared plots. At the end of the study, significant differences were found in theLarrea cuneifoliacommunity, where average forage species cover increased by 156% over the control, and greater carrying capacity (129%) was also obtained from the cleared treatment. No significant differences were found in theLarrea divaricatacommunity. Data lead us to recommend shrub control as an improvement practice only in areas with low forage species cover and poor carrying capacity.     

Supply and accumulation of metals in two Egyptian desert plant species growing onwadi-fill deposits

Sandy soils of thewadisin the Eastern Desert of Egypt have a poor retentive capacity for metals. The contents of Ca, Mg, K, Na, Fe, Al, Mn, Co, Ni, Cu and Zn in 37 soils from this area were highly variable. The metal contents of two dominant plant species of the Eastern Desert (Senna alexandrinaandCleome droserifolia) showed no correlation with soil metals. Metals accumulated in the leaves, withCleomehaving overall higher contents of Fe, Al, Mn, Co, Ni, Na and Si thanSenna, even thoughCleometended to grow in soil with low contents of these metals.     

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.     

Arbuscular mycorrhizal associations in Solanum centrale (bush tomato), a perennial sub-shrub from the arid zone of Australia

Arbuscular mycorrhizal (AM) fungi convey well documented benefits to plant growth in domesticated species. We investigated AM in Solanum centrale, a desert shrub of central Australia and traditional food for Indigenous Australians. AM were observed in roots of S. centrale from wild and cultivated stands of different ages and management regimes. Greenhouse seedlings grown in sterilised sand were provided with no or minor additions of phosphorus, with or without AM fungi. Inoculated seedlings not fertilised with phosphorus exhibited moderate AM formation. Added phosphorus resulted in an absence of AM. Inoculation did not significantly affect dry weight, root length and plant height of seedlings fertilised with phosphorus but significantly increased the size of unfertilised seedlings. Inoculation significantly increased root phosphorus content, decreased root to shoot ratio and decreased root biomass at all phosphorus additions, despite the absence of observable AM. Thus it appears AM fungi in the root zone influenced certain plant characteristics, regardless of phosphorus nutrition. Overall, S. centrale benefited from the presence of AM through increased phosphorus uptake, but only when the seedlings were growing in soil with extremely low available phosphorus. The response was immediate in our experimental system and is likely to be important in the wild.     

Influence of cattle grazing on population density and species richness of granivorous birds (Emberizidae) in the arid plain of the Monte, Argentina

Cattle grazing is an important disturbance in the Monte plain, reducing grass biomass and rates of fruit setting. Grass seeds are the most important food for granivorous birds (Emberizidae) during winter. The objective of this study was to test whether granivorous bird populations (Emberizidae), grass seed production, and vegetation structure differed at sites with different intensities of grazing. Emberizid density and species richness were higher in the ungrazed site than in the two grazed paddocks. Seed abundance was also higher in ungrazed vs. grazed sites. Woody vegetation, that serve as safe nest sites, did not differ among treatments. Granivorous bird populations seemed to be affected by cattle grazing; however, the main mechanisms of this process remain unknown.     

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。     

水热条件共同驱动新疆湿地植物丰富度空间分布格局

在地理空间尺度上,气候因素（如热量、降水量等）一直被认为是物种多样性的主要驱动因素。然而,气候因素能否解释湿地植物多样性格局仍不清楚。研究探讨了环境因素尤其水分和热量条件对湿地物种分布的影响,具体包括经度、纬度、海拔、年平均降水量、年平均气温、年平均蒸发量和年平均日照时数总计7个指标,研究对象涉及新疆3个二级流域的26处湿地公园,应用结构方程模型分析了各指标对湿地植物丰富度影响的相对大小及其相互作用关系。另外,还利用莫兰指数（Moran’s I）对各变量残差进行了空间相关性分析,以评估空间相关性的影响。结果表明：（1）结构方程模型总计解释了41.8%的物种丰富度变异,以年平均降水量对物种丰富度总效应最高,为0.47,其次是年平均日照时数,为-0.42,其中年平均降水量为正效应,年平均日照时数为负效应。其他各指标对物种丰富度的效应均不显著。（2）年平均降水量对植物丰富度的影响主要表现为直接效应,占总效应的92.86%,年平均日照时数对植物丰富度的影响主要是间接效应,占总效应的54.76%。（3）空间相关性分析表明年平均降水量和年平均日照时数的残差均不存在空间相关性,莫兰指数在-0.15～...     

The study of artificial intelligence for predicting land use changes in an arid ecosystem

Journal of Geographical Sciences - During the 21st century, artificial intelligence methods have been broadly applied in geosciences to simulate complex dynamic ecosystems, but the use of...