Vegetation dynamics of coal mining city in an arid desert region of Northwest China from 2000 to 2019

Coal mining has led to serious ecological damages in arid desert region of Northwest China. However, effects of climatic factor and mining activity on vegetation dynamics and plant diversity in this region remain unknown. Wuhai City located in the arid desert region of Northwest China is an industrial city and dominated by coal mining. Based on Landsat data and field investigation in Wuhai City, we analyzed the vegetation dynamics and the relationships with climate factors, coal mining activity and ecological restoration projects from 2000 to 2019. Results showed that vegetation in Wuhai City mostly consisted of desert plants, such as Caragana microphylla, Tetraena mongolica and Achnatherum splendens. And the vegetation fractional coverage(VFC) and greenness rate of change(GRC) showed that vegetation was slightly improved during the study period. Normalized difference vegetation index(NDVI) was positively correlated with annual mean precipitation, relative humidity and annual mean temperature, indicating that these climate factors might play important roles in the improved vegetation. Vegetation coverage and plant diversity around the coal mining area were reduced by coal mining, while the implementation of ecological restoration projects improved the vegetation coverage and plant diversity. Our results suggested that vegetation in the arid desert region was mainly affected by climate factors, and the implementation of ecological restoration projects could mitigate the impacts of coal mining on vegetation and ecological environment.     

西鄂尔多斯天然荒漠灌丛光合生态适应性

为了探究西鄂尔多斯地区荒漠灌丛的光合生态适应性,以4种天然荒漠灌丛半日花(Helianthemum songaricum)、红砂(Reaumuria songarica)、沙冬青(Ammopiptanthus mongolicus)、霸王(Sarcozygium xanthoxylon)为研究材料,利用Li-6400便携式光合测定仪野外原位测定荒漠灌丛日光合动态和季节动态规律。结果表明:①不同季节灌丛光合作用适宜的温度存在差异,高温环境使灌丛净光合速率最适温度升高,低温环境使其降低。②不同季节4种灌丛的净光合速率、蒸腾速率、水分利用效率和气孔导度日变化曲线趋势为"双峰形",胞间CO2浓度日变化曲线趋势为"W形",但不同季节各指标平均日变化趋势表现各异。③不同季节灌丛净光合能力表现为:沙冬青>霸王>红砂>半日花,说明沙冬青具有较强的生态适应性。④净光合速率和蒸腾速率日变化趋势几乎保持同步状态,表明4种灌丛叶片气孔对外界环境变化反应敏感。⑤水分是限制荒漠灌丛生长发育的关键因素。为了保证荒漠植物的群落稳定性和生物多样性,在夏、秋季需对沙冬青、半日花、红砂和霸王进行水分管理。     

Response of ants to grazing disturbance at the central Monte Desert of Argentina: community descriptors and functional group scheme

Livestock ranching is one of the main productive activities in arid regions of the world.Grazing produces changes in animal as well as plant communities(e.g.richness,abundance and species dominance relationships).Ants are good biological indicators due to the environmental fidelity of some of their community parameters.We described the functional structure of the ant community in the central Monte of Mendoza,Argentina,and examined the effect of grazing using richness,diversity and the functional group scheme.We used pitfall traps to sample ants at a reserve with 30-year cattle exclusion and at an adjacent ranch.Eleven of the 27 recorded species showed significant differences in their abundance and two species were absent at the ranch.While richness and diversity did not reflect these differences,functional groups did.Hot Climate Specialists were more abundant at the ranch while Cryptic Species and Generalized Myrmicinae increased at the reserve.This study supports the utility of the functional group scheme to study the effects of grazing disturbance in ant communities of arid regions.     

Grazing and heat stress protection of native grass by a sand-fixing shrub in the arid lands of northern China

Shrub species are used in restoration projects on dryland for their facilitation effects, which include environmental improvements and protection from herbivore feeding. Facilitation effects on forage grasses are potentially important in improving grazing capacity on rangelands. However, the morphology-dependent performance of benefactor plants in facilitating forage species growth and supplementation under moderate grazing intensity remains unclear. Here, our main purpose was to measure facilitation performance in terms of the survival of a native forage grass, Agropyron cristatum (L.) Gaertn. (Gramineae)., in accordance with the growth conditions of a sand-fixing benefactor shrub, Caragana microphylla Lam., in the Hulun Buir Grassland, northern China. Six study sites with patches of A. cristatum and C. microphylla were established at the foot of fixed sand dunes. At each site, five quadrats were set in places where C. microphylla coverage was 100% and A. cristatum grew among the shrubs (shrub quadrats), and another five were set where A. cristatum grew alone without C. microphylla (grass quadrats). We measured the morphological traits of C. microphylla and A. cristatum in all 60 quadrats, along with the soil water content and soil temperature. The data were compared between the shrub and grass quadrats by generalized linear mixed-effect models to assess the shrub's facilitation effects. We also used such models to elucidate the relationship between the average height of C. microphylla and the morphological traits of A. cristatum in the shrub quadrats. The maximum height, average grazed height, and the number of seed heads of A. cristatum were greater in the shrub quadrats than in the grass quadrats. The soil surface temperature was lower in the shrub quadrats. The maximum height and seed head number of A. cristatum were positively associated with the average height of C. microphylla. These results suggest that the grazing impact and heat stress were smaller in shrub quadrats than in grass quadrats, and that the degree of this protective effect depended on the shrub height. The shrub canopy seemed to reduce the increase in soil temperature and keep the grass vigorous. Livestock likely avoided grazing grasses in the C. microphylla patches because of the shrub's spiny leaves; only the upper parts of the grass stems (including the seed heads) protruding from the shrub canopy were grazed. The sand-fixing shrub thus moderates the grazing impact and soil temperature, and contributes to vegetation restoration and grazing system sustainability.     

Prioritizing woody species for the rehabilitation of arid lands in western Iran based on soil properties and carbon sequestration

Plants are an important component in many natural ecosystems. They influence soil properties, especially in arid ecosystems. The selection of plant species based on their adaptations to site conditions is essential for rehabilitation of degraded sites and other construction sites such as check-dams. Other factors to be considered in species selection include their effects on soil properties and their abilities to meet other management objectives. The purpose of this study was to assess the effects of native (Populus euphratica Oliv. and Tamarix ramosissima Ledeb.) and introduced (Eucalyptus camaldulensis Dehnh. and Prosopis juliflora (Swartz) DC.) woody species on soil properties and carbon sequestration (CS) in an arid region of Iran. Soil sampling was collected at three soil depths (0-10, 10-20 and 20-30 cm) at the sites located under each woody species canopy and in an open area in 2017. Soil physical-chemical property was analyzed in the laboratory. The presence of a woody species changed soil characteristics and soil CS, compared with the open area. For example, the presence of a woody species caused a decrease in soil bulk density, of which the lowest value was observed under E. camaldulensis (1.38 g/cm³) compared with the open area (1.59 g/cm³). Also, all woody species significantly increased the contents of soil organic matter and total nitrogen, and introduced species had more significant effect than native species. The results showed that CS significantly increased under the canopy of all woody species in a decreasing order of P. euphratica (9.08 t/hm²)>E. camaldulensis (8.37 t/hm²)>P. juliflora (5.20 t/hm²)>T. ramosissima (2.93 t/hm²)>open area (1.33 t/hm²), thus demonstrating the positive effect of a woody species on CS. Although the plantation of non-native species had some positive effects on soil properties, we recommend increasing species diversity in plantations of native and introduced woody species to provide more diversity for the increased ecosystem services, resilience, health and long-term productivity.     

Grazing intensity effects on the vegetation in desert rangelands of Southern Tunisia

@Mouldi GAMOUN$Laboratory of Range Ecology, Arid Regions Institute (IRA)!Medenine 4119, Tunisia     

黄土高原的植被演替研究现状及发展趋势

从地质、历史时期黄土高原植被演替研究和现存植被的群落演替及群落结构特征 演化研究两方面论述了黄土高原的植被演替研究现状及发展趋势,认为黄土高原植被演替研 究对黄土高原的生态建设尤其是退耕还林还草工程建设具有重要意义,建议基于黄土高原的 植被演替规律进行仿自然植被林草建设。     

荒漠草原不同植被类型土壤微生物群落功能多样性

利用Biolog EcoplateTM技术通过对荒漠草原生态系统中沙米、白沙蒿、柠条、沙冬青和人工乔木林5种植被类型土壤微生物群落功能多样性分析,以探讨不同植被类型对土壤微生物群落代谢功能多样性的影响.结果表明,5种植被类型土壤微生物群落代谢活性有显著的差异(P＜0.01),5种植被类型土壤微生物群落利用碳源的种类也存在差异,氨基酸类、羧酸类和糖类是其主要的碳源利用类型.在Biolog ECO板培养基接种培养96 h后,5种植被类型土壤微生物群落多样性显示,物种丰富度指数(R)和均匀度指数(EH)差异显著,Shannon 指数(H′)差异不显著.     

Urban ants of the city of Buenos Aires,Argentina: species survey and practical control

ABSTRACT

Ants are among the most diverse, abundant and ecologically significant organisms on earth. They have colonized almost all existing habitats, including urban areas, where they may pose serious problems for human activities. Here, we present different aspects of our studies on urban ants in the city of Buenos Aires aimed at collecting information on the species present in the city and at improving bait control strategies via laboratory assays. The use of these baits represents a control strategy that is environment-friendly as it avoids indiscriminate pesticide release. Moreover, we show that our baits exhibit higher efficiency when compared to a commercial bait, as it is optimized in terms of the ants’ feeding behavior even when both have the same active compound and at the same concentration. This work represents the first integrative study on urban ants in the city of Buenos Aires and indicates that the control of invasive species in urban settings may be improved by increasing the scientific knowledge of the biology of the target species.     

Land cover change detection based on satellite data for an arid area to the south of Aksu in Taklimakan desert

An experiment is made to detect the land-cover change in the area located to the south of Aksu in the northern Taklimakan desert through analyses of satellite data pixel by pixel basis. The analyzed data are those observed in the late summer and early autumn of 1973, 1977, 1993 and 1995. As a parameter of land-cover, SAVI (Soil Adjusted Vegetation Index) derived from the data of Landsat MSS and JERS-1 OPS (Optical Sensor) is used. The result indicates the increase of vegetation in the oasis areas, confluent area of the Yarkant and Kashgar Rivers and around reservoirs while little change occurs in the desert area. The 1973 satellite image shows the abundant flow in the Yarkant River while the river is almost dried up in the satellite images of later years. The trend of the decrease in the Hotan River flow is recognized although not so dramatic as that of the Yarkant River.     

陕北黄土高原生态资产与区域生态安全程度研究

在GIS支持下,通过测定陕北黄土高原植被生产和生态调节的物质量及生态资产价值.结果表明:①通过计算,陕北黄土高原每年的生态资产总价值为7.00×1010元,其中释放氧气的价值最高,占总价值的29.51%;土壤保持价值最小,占总价值的1.5%.而就植被类型而言,果树的生态价值最高,占总价值的43.89%;最小是沼泽,占总价值的0.4%.②通过地理信息系统与生态学的结合,对陕北黄土高原的生态资产进行定量测量,并利用GIS软件的空间分析功能,绘制了陕北黄土高原生态资产价值空间分布图.③陕北黄土高原生态安全程度为0.45,处于生态不安全状态,负荷超载,要狠抓生态建设.④针对陕北黄土高原环境现状,提出相应的治理对策.     

干旱区沙漠化逆转过程中优势种群及其根系特征研究

根系是植物群落演替的重要内容,对植被演替过程具有十分重要影响作用。采用时空替代法,选择不同恢复阶段,研究了干旱荒漠区植被恢复演替不同阶段优势种群及其根系生态特征。结果表明:沙漠化逆转过程中,优势种群更替过程为:沙米-沙蒿-油蒿-紫婉木、针茅;在恢复演替初期(初始阶段,先锋阶段)植被根系浅(平均<50 cm)而水平分布范围广,侧根数量少但生长旺盛;随着恢复时间的加长,优势种群根系分布深度增加,侧根数量增加但水平生长受到一定的抑制,根幅逐渐减小;优势种群根冠比的变化趋势为沙米(初始阶段)<沙蒿(先锋阶段)<油蒿(发展阶段)<针茅(原生群落)。研究同时发现,同一种群在不同的演替阶段具有不同的根系分布特征和规律。对于沙蒿种群来说,根冠比是发展阶段(0.56)>先锋阶段(0.36),而地上、地下生物量却是先锋阶段(360.83g,161.33g)>发展阶段(32.8g,16.81g);而油蒿根冠比则是发展阶段(0.61)>相对稳定阶段(0.21)。各演替阶段根系和土壤环境因子之间存在相互影响,优势种群根系生物量及生物量分布与土壤颗粒组成、土壤水分的空间分布有着密切的关系。     

西北半干旱区湿地生态系统植物群落多样性的研究

为了研究西北半干旱区湿地植被多样性差异,以宁夏盐池县四儿滩湿地为例,采用样线法,从湿地中央辐射向四个方向,布设东、南、西、北四条样线,共取样方88个,主要调查植被的盖度、高度、频度、株数等,计算每种植被的重要值,运用SPSS软件进行聚类,分析了该湿地的植被组成和群落特征。采用Shannon-Wiener指数、Simpson指数、群落均匀度指数和丰富度指数对植物多样性进行研究分析,并结合多年的气象数据,分析结果为:碱蓬和盐爪爪群落为湿生带的代表群落,白刺和沙鞭群落与芨芨草、猪毛蒿和苦豆子群落为交错带的代表群落,阿尔泰狗哇花、赖草和砂兰刺头群落为旱生带代表群落;四儿滩湿地四条样线之间植被多样性的差异主要受四儿滩湿地本身的地理环境和人类生产活动的影响。年际植被多样性差异主要受月降雨量分配的影响。     

Hyper-spectral characteristics of rolled-leaf desert vegetation in the Hexi Corridor,China

Desert plants survive harsh environment using a variety of drought-resistant structural modifications and physio-ecological systems. Rolled-leaf plants roll up their leaves during periods of drought, making it difficult to distinguish between the external structures of various types of plants, it is therefore necessary to carry out spectral characteristics analysis for species identification of these rolled-leaf plants. Based on hyper-spectral data measured in the field, we analyzed the spectral characteristics of seven types of typical temperate zone rolled-leaf desert plants in the Hexi Corridor, China using a variety of mathematical transformation methods. The results show that:(1) during the vigorous growth period in July and August, the locations of the red valleys, green peaks, and three-edge parameters, namely, the red edge, the blue edge, and the yellow edge of well-developed rolled-leaf desert plants are essentially consistent with those of the majority of terrestrial vegetation types;(2) the absorption regions of liquid water, i.e., 1400–1500 and 1600–1700 nm, are the optimal bands for distinguishing various types of rolled-leaf desert plants;(3) in the leaf reflectance regions of 700–1250 nm, which is controlled by cellular structure, it is difficult to select the characteristic bands for differentiation rolled-leaf desert vegetation; and(4) after processing the spectral reflectance curves using a first-order differential, the envelope removal method, and the normalized differential ratio, we identify the other characteristic bands and parameters that can be used for identifying various types of temperate zone rolled-leaf desert plants, i.e., the 510–560, 650–700 and 1330–1380 nm regions, and the red edge amplitude. In general, the mathematical transformation methods in the study are effective tools to capture useful spectral information for species identification of rolled-leaf plants in the Hexi Corridor.     

玉米地昆虫及捕食性节肢动物群落结构及动态研究

南宁市郊玉米地害虫、捕食性昆虫、蜘蛛及中性昆虫由90科315种组成,害虫、蜘蛛及捕食性昆虫是玉米地节肢动物群落组成及功能作用的主要群落。禾谷缢管蚜(Rhopalosiphum padi)、玉米螟(Ostrinia furnacalis)、六斑月瓢虫(Menochilus sexmaculata)、龟纹瓢虫(Propylaea japonica)、食虫沟瘤蛛(Ummeliata insecticeps)、锥腹肖蛸(Tetragnatha maxillosa)、八斑鞘腹蛛(Coleosoma octomaculatum)、类奇异獾蛛(Trochosa ruricoloides)和脉娲蛛(Wadicosa fidelis)等是群落的主体。分析了4个亚群落的时空格局及数量变动规律以及天敌对害虫的控制作用。     

放牧与刈割对科尔沁草甸植被演替的影响

本文研究了放牧与刈割两种草地利用方式对科尔沁草甸植被演替的影响。结果表明:1)在自由放牧干扰下,优势度最大的前五个种为虎尾草(27.8)、蒲公英(3.52)、狼毒(3.42)、野韭菜(3.03)、鹅绒委陵菜(2.67);在秋季割草干扰下,优势度最大的前五个种为大油芒(9.57)、狗尾草(7.36)、野古草(6.36)、洽草(4.85)、芦苇(4.74)等五种禾本科植物;2)在自由放牧干扰下,一年生植物在群落中占据重要地位,其优势度为35.0,小于多年生植物的优势度55.9;在割草干扰下,多年生植物在群落中占据绝对优势,其优势度为82.9,大于一年生植物优势度10.6;3)在放牧扰动下,草地群落物种替代表现在不同植物生活型之间,主要是多年生草本为一年生草本和灌木所替代;表现在同一生活型不同物种之间,主要是多年生优质牧草为多年生劣质牧草或有毒有害杂草替代。     

植物根系水力提升作用研究进展综述

植物根系水力提升作用是植物深层根系吸收深层土壤水分,再通过浅层根系释放到较干燥浅层土壤中的过程。水力提升作用所释放的水分可缓解干燥土层水分匮乏,对改善自身及邻近植物的水分亏缺、促进植物养分吸收、促进土壤养分分解和矿化过程具有重要意义。随着对植物生态系统水分平衡问题的关注和研究手段的发展,水力提升作用日益成为干旱、半干旱区植物生态学与水文学共同关注的重要研究内容之一。通过回顾和分析水力提升作用的研究历史、影响因素、提升数量、研究方法、生态作用等,特别阐述了水力提升作用在半干旱区人工固沙植被恢复中的潜在应用价值,改善人工固沙植被区土壤水分条件,提高固沙植物群落的稳定性。     

河西走廊中段干旱荒漠区土壤水热状况初步分析

通过对位于干旱荒漠区的张掖国家气候观象台土壤温湿度、土壤温度梯度、土壤导热率分析,结果表明:该地区土壤温度年变化、日变化较明显,受辐射变化影响大;土壤湿度年变化、日变化不明显,受降水影响较大.不管冬、春、夏季,土壤温度在晴天日变化较明显,但在雨(雪)天,日变化不明显.土壤湿度在晴天和雨(雪)天日变化均不明显,对降水有一...