Mountainous landscape vegetation and species composition at Wadi Helo: A protected area in Hajar Mountains,UAE

Wadi Helo (WH), in the United Arab Emirates, is a famous archeological site and protected area in the Hajar Mountains in the Arabian Peninsula. We investigated effects of topography, aspect, and altitude on floral diversity and species composition in this heterogeneous, mountainous, and highly arid environment. Using twenty transects distributed from the mountains top to the wadi bed; eighty plots, 100 m² each, were selected for vegetation analysis. Classification of vegetation using TWINSPAN showed three groups in the wadi bed and five in the mountains, each distinguished by different dominant species. Forsskaolaea tenacissima, Rhazya stricta, Tephrosia apolina, Notoceras bicorne, Acacia tortilis, and Fagonia indica were dominants of the microhabitats of the wadi bed. Gorges were dominated with Dodonaea viscosa and Lavandula subnoda. The other four groups were found on the mountain slopes and were associated with particular aspects (being north-, south-, west-, or east-facing). The dominant species for these different aspects were, respectively: Boerhavia elegans; Ochradenus aucheri and Helianthemum lippii; Moringa peregrina; and Euphorbia larica and Cenchrus ciliaris. Altitude showed highly significant positive relationship with species frequency (P < 0.001). South-facing slopes had the highest species richness and concentration of dominance. We concluded that the distribution of dominant species was a reflection of their ecological requirements and adaptations. Seven plant species were recorded as new to the flora of the UAE. These, plus ten additional species that had been reported as rare in only one of the two published floras of the UAE were highlighted as meriting greater priority in conservation.     

新疆荒漠一年生植物区系组成、分布及资源类型

荒漠一年生植物生长速度快、繁殖力强,具有重要的饲用、药用和生态价值.通过文献资料与标本采集信息的考证和野外调查,明确了新疆荒漠一年生植物的物种数量、分布特征及资源类型.结果 表明:新疆荒漠一年生植物共有236种,隶属于20科109属,其中藜科为优势科,猪毛菜属为优势属.科可划分为4个分布区类型,以世界广布科为主,占总科...     

汾河水库湿地植物区系组成及物种多样性研究

在野外78个植物样方调查数据的基础上,采用吴征镒、王荷生区系分析方法和丰富度指数(Ma、Pa)、均匀度指数(JP、EA)和综合多样性指数(H'、DS)分析方法,对汾河水库湿地植被物种区系成分和多样性进行了研究。结果表明:1)该湿地共有湿地植物72种,分别隶属于28科58属。优势科、单种属现象明显,其中以菊科(Compositae)种数为最多,植物水分生态类型多样,中生植物占有明显优势;2)植物分布区系类型多样,以世界分布属为主,占属总数的34.48%,反映了该湿地植被的隐域性特征明显,其次是北温带分布占总属数的24.14%,显示北温带区系的区域性;3)在研究区0～400m的范围内,随着离水库边缘距离的递增,物种多样性呈先增高后降低的趋势,且土壤水分条件是影响研究区物种多样性变化的主要环境因子。     

Endemics and endangered species in the biodiversity hotspot of the Shada Mountains,Saudi Arabia

Shada Mountains in Saudi Arabia, separated by Maleel Wadi into twin mountains(i.e., Shada Alalah and Shada Asfal), are rich in biodiversity. We investigated the diversity of endemics and endangered species of the mountains based on the data collected from 38 stands falling in 8 elevational zones ranging from 500 to 2215 m a.s.l. Results indicated that 495 plant species falling in 314 genera and 76 families occurred in the Shada Mountains, including 19 endemic species and 43 endangered species, and accounting for 22% of the total flora in Saudi Arabia. Canonical correlation analysis indicated that physiographic features, particularly altitude play an important role in the frequency and abundance of species. Endemics were not evenly distributed in the Shada Mountains and mostly restricted in the elevation zone of 1000–1500 or 1500 m a.s.l. When the altitude reached up to 2000 m a.s.l., the endemics decreased substantially due to the significantly low temperature. The endangered species existed three different distribution patterns:(i) most endangered species distributed in the altitudes of 1000–1800 m a.s.l.;(ii) endangered trees, lianas, and shrubs occupied the altitudes 1000–1300 m a.s.l.; and(iii) endangered subshrubs and herbs inhabited the altitudes 1500–2100 m a.s.l. The results demonstrated that the biodiversity of endangered species in the Shada Mountains is high and undisturbed by invasive species, and protective measures should be taken against human disturbances to the small-scale hotspot.     

Spatial and temporal variations of vegetation cover and the relationships with climate factors in Inner Mongolia based on GIMMS NDVI3g data

Variation in vegetation cover in Inner Mongolia has been previously studied by the remote sensing data spanning only one decade. However, spatial and temporal variations in vegetation cover based on the newly released GIMMS NDVI3g data spanning nearly thirty years have yet to be analyzed. In this study, we applied the methods of the maximum value composite(MVC) and Pearson's correlation coefficient to analyze the variations of vegetation cover in Inner Mongolia based on GIMMS NDVI3g data spanning from 1982 to 2013. Our results indicate that the normalized difference vegetation index(NDVI) increased at a rate of 0.0003/a during the growing seasons despite of the drier and hotter climate in Inner Mongolia during the past three decades. We also found that vegetation cover in the southern agro-pastoral zone significantly increased, while it significantly decreased in the central Alxa. The variations in vegetation cover were not significant in the eastern and central regions. NDVI is positively correlated with precipitation(r=0.617, P=0.000) and also with air temperature(r=0.425, P=0.015), but the precipitation had a greater effect than the air temperature on the vegetation variations in Inner Mongolia.     

Weed species composition of conventional soyabean crops in Hungary is determined by environmental,cultural, weed management and site variables

The goal of this study was to identify factors determining weed species composition in soyabean crops in Hungary, where its expanding production faces difficult weed problems. The abundance of weed flora was measured in 262 fields across the country, along with 38 background variables. Using a minimal adequate model containing 24 terms with significant net effects, 21.6% of the total variation in weed species data could be explained. Plot location (edge vs core position, the single site variable in our analysis) was found to be the most important explanatory variable that was followed by a set of environmental (temperature, precipitation, altitude, soil texture, pH, Ca, K, Na and humus content), cultural (cultivar maturity, organic manure, fertiliser P and N, row spacing) and weed management (flumioxazin, pendimethalin, dimethenamid, propaquizafop, bentazone, quizalofop‐p‐ethyl, quizalofop‐p‐tefuril, linuron, thifensulfuron) factors. Variation partitioning revealed that environmental variables accounted for about four times more variance than cultural and about two and half times more than weed management variables. Chenopodium album, Ambrosia artemisiifolia, Hibiscus trionum, Echinochloa crus‐galli and Convolvulus arvensis were the most dominant and frequent weeds, but their abundance was influenced by different factors. The responses of weed species to the studied variables provide new information about their ecological behaviour, and our findings also can be used to develop better weed management strategies.     

博尔塔拉河与精河流域绿洲植被盖度变化特点及其驱动力分析

绿洲是维系干旱地区人类生存、活动与发展的基本场所。探讨植被盖度在时间和空间尺度上的动态变化及由此所引起的环境效应,对合理利用绿洲国土资源具有重要战略意义。本研究利用1990年到2005年遥感数据资料,计算了博尔塔拉河、精河流域绿洲植被盖度,分析了该地区植被盖度的历史演变特征。结果显示:(1)1990~2000年期间,植被退化型所占比例最大,弃耕型所占比例最低;(2)2000~2005年期间,植被恢复型所占比例最大,弃耕型所占比例最低;(3)1990~2005年的16年间,研究区总体呈现植被恢复趋势。结果也表明:影响研究区绿洲植被盖度的主要自然因素是年降水量和年蒸发量,而人口剧增带来的水土资源开发强度增大则是主要人文因素。     

Response of riparian vegetation to the removal of the invasive forb,Solidago gigantea,and its litter layer

In order to explore the methods of recovering native grasses into exotic vegetation, the response of riparian vegetation to the removal of the above‐ground shoots and/or litter of Solidago gigantea in a flood plain in Hokkaido, northern Japan, was investigated. The four treatments were: the removal of the above‐ground shoots of S. gigantea (A); the removal of the litter of S. gigantea (L); the removal of both the above‐ground shoots and litter of S. gigantea (AL); and a control (C). The vegetation cover and S. gigantea cover decreased in the A and AL treatments and increased in the L and C treatments. The understory plant cover increased in the A and AL treatments, but did not change in the L and C treatments. The increases in the understory cover in the A and AL treatments were associated with increases in Phalaris arundinacea. The seedling emergence of P. arundinacea was promoted by AL. In a greenhouse, the S. gigantea litter tended to decrease the seed germination of P. arundinacea. The AL treatment also increased the abundance of the other exotic plant, Solidago altissima. The continuous removal of the above‐ground shoots and litter of S. gigantea long term is effective for promoting the recovery and emergence of native riparian grassland vegetation. However, this method also promotes the recovery of other exotics.     

Distribution patterns and traits of weed communities along an urban–rural gradient under rapid urbanization in Shanghai,China

In order to better understand the effects of urbanization on weed communities, the distribution of weed communities in Shanghai, China, was systematically investigated. The diversity of weed communities and four environmental factors, including the relative light intensity, soil moisture, soil compaction and soil pH, were measured in 1375 plots along an urban–rural gradient. The species diversity indices in each area along the urban–rural gradient were compared by using a one‐way ANOVA. The weed communities were identified by using clustering methods that were based on relative dominance information. A canonical correspondence analysis was used to reveal the relationships between the species composition and the environmental factors at the community level and the Spearman's rank correlation test was used to test the relationship between the number of weed communities and each environmental factor. A total of 183 species, belonging to 41 families and 123 genera, was recorded. It was found that the species richness, Shannon–Wiener diversity index and Pielou evenness index followed a unimodal curve along the urban–rural gradient. The 1375 plots were divided into 133 weed community types. All four environmental factors significantly affected the species composition of the weed communities, but only soil compaction had significant effects on the number of weed communities. It was concluded that the diversification of habitat type and environmental change along the urban–rural gradient led to more weed communities in rural areas and fewer weed communities in urban areas. Based on the species' habitats and distribution patterns, the weeds were divided into “widespread”, “urban” and “rural”.     

宁南山区植被恢复模式对土壤主要酶活性、微生物多样性及土壤养分的影响

探究不同植被恢复模式对土壤主要酶活性、微生物多样性及养分的影响,可为当地选择最适宜的植被恢复模式提供理论依据。利用野外取样与室内实验相结合的方法,研究了宁南山区4种植被恢复模式(7a生刺槐、落叶松、油松)以及荒地的土壤酶活性、微生物多样性、土壤养分特征,并利用Illumina-Miseq高通测序技术对土壤中细菌的16SrDNA基因V3～V4区片段和真菌的18SrDNA基因V4区片段进行了测序分析。结果表明：(1)在0～30 cm土层,荒地和刺槐土壤的脲酶、蔗糖酶活性较强,油松、落叶松的碱性磷酸酶、过氧化氢酶活性较强;(2)土壤真菌多样性对植被恢复模式的响应强于土壤细菌,土壤细菌的ACE、Chao l和Shannon指数高于土壤真菌,其多样性在4种植被恢复模式间无显著差异,油松显著提高了土壤真菌多样性;(3)荒地土壤全磷、碱解氮、速效磷、有机质含量最低,刺槐土壤的速效养分和有机质含量最高,土壤脲酶、过氧化氢酶与土壤养分相关性显著,土壤微生物多样性与土壤有机质、全磷含量密切相关。刺槐在改善多种土壤养分、酶活性上效果明显,是当地植被恢复可以优先考虑的树种。     

Characteristics and mineralogy of desert alluvial soils: Wadi Zegrir,Northern Sahara of Algeria

Few studies on the characteristics and mineralogical trends of the soils in the Sahara Desert have been reported in the literature. This work aims at studying the morphology, the classification, and the mineralogy of desert alluvial soils of the Mzab region in the Northern Sahara, Algeria. Morphological and analytical studies carried out on fourteen pedons of wadi Zegrir over a range of elevations (250–850?m) indicate that the soils are sandy to silty clay, nonsaline (electrical conductivity, EC?相似文献   

Effects of vegetation near-soil-surface factors on runoff and sediment reduction in typical grasslands on the Loess Plateau,China

Vegetation near-soil-surface factors can protect topsoil from erosion, however, their contributions to the reduction of soil erosion, especially under natural rainfall events, have not been systematically recognized. This study was performed to quantify the effects of near-soil-surface factors on runoff and sediment under natural rainfall events on grasslands dominated by Bothriochloa ischaemum(Linn.)Keng(BI grassland) and Artemisia gmelinii Thunb.(AG grassland) in two typical watersheds on the ...     

Vegetation composition differentiation and species-environment relationships in the northern part of Isfahan Province,Iran

A considerable proportion of Iran's territory is covered with arid and semi-arid rangelands and mismanagement and overexploitation of those rangelands have resulted in serious ecological degradation. Thus, the need is pressing to examine the present species composition and the relationships with environmental factors for providing the needed scientific references to species conservation and ecological rehabilitation efforts. The aims of this study were to examine the species composition and to delineate the most important factors influencing the distributions of plant species and groups in the northern rangelands of Isfahan Province(Iran) using two-way indicator species analysis(TWINSPAN), detrended correspondence analysis(DCA), principal component analysis(PCA), and canonical correspondence analysis(CCA). Field investigations were conducted in the growing season of 2014 using stratified random method in 22 homogeneous sampling units. In total, 75 plant species belonging to 52 genera and 19 families were identified. The most important families were Asteraceae and Papilionaceae, the most important genera were Astragalus, Cousinia, and Acanthophyllum, and the most important species were Artemisia aucheri and Artemisia sieberi. Plant species were classified into 10 groups using TWINSPAN. DCA was used to estimate the magnitude of changes in species composition along the first two ordination axes to provide gradient length estimations for PCA and CCA ordinations. The first three PCA axes and the first three CCA axes demonstrated similar cumulative percentage of variance, indicating that the environmental factors(selected by PCA) used in CCA ordination were acceptable for explaining the species composition and the distributions. CCA ordination showed that the first axis was closely related to elevation, slope, surface bare soil cover, surface litter cover, gravel proportion, organic matter, total nitrogen, Ca CO3 content, and grazing intensity and that the second axis was closely related to sand proportion, silt proportion, clay proportion, and saturation percentage. Among these factors, elevation was the most effective factor to separate the plant groups and grazing was the major cause of rangeland degradation.     

Vegetation composition and distribution on the northern slope of Karlik Mountain to Naomaohu basin, East Tianshan Mountains

This paper reports the characteristics of plant flora in the region of the northern slope of Karlik Mountain to Naomaohu basin,based on field investigation of the vegetation and referring to relevant literature. The results show that the flora of the study area mainly consists of communities of single species or a limited number of species,genera and families. The flora composition is marked by the phenomenon of dominant families and genera;the temperate element occupies a dominant position,while in terms of the genera the Tethys element is an important component. Areal-types of the species are dominated by the floral element of Asian Central-part with xerophytic characteristic,and the life-forms of plants are mainly perennial and herbaceous. These characteristics reflect that the compositions of the species in this region possess both ancient and young elements. Analysis of the relationship between the species composition,plant community diversity and altitude gradient,we found that the structure of the vegetation has an obvious vertical distribution. The lower and higher altitude areas,where the climate conditions are relative inclement,are mainly occupied by the plant communities with simple structure and single dominant population,while the species richness in the mid-altitude area increases with favorable temperature and precipitation. Consequently,the species diversity and evenness indices show single-peak distribution with increasing elevation(about < 2500 m) ,while the dominance indices decrease in elevation from 500 m to 2500 m and increase in elevation of > 2500m.     

Response of soil nitrogen,phosphorous and organic matter to vegetation succession on the Loess Plateau of China

 Revegetation is a traditional practice widely used for soil protection. We evaluated the effect of natural revegetation succession on soil chemical properties and carbon fractions (particulate organic carbon (POC), humus carbon (HS-C), humic acid carbon (HA-C) and fulvic acid carbon (FA-C)) on the Loess Plateau of China. The vegetation types, in order from the shortest to the longest enclosure duration, were: (a) abandoned overgrazed grassland (AbG3; 3 years); (b) Hierochloe odorata Beauv. (HiO7; 7 years); (c) Thymus mongolicus Ronnm (ThM15; 15 years); (d) Artemisia sacrorum Ledeb (AtS25; 25 years); (e) Stipa bungeana Trin Ledeb (StB36; 36 years) and (f) Stipa grandis P. Smirn (StG56; 56 years). The results showed that the concentrations of soil organic carbon, total nitrogen and available phosphorus increased with the increase of restoration time except for ThM15. The concentration of NH₄-N increased in the medium stage of vegetation restoration (for ThM15 and AtS25) and decreased in the later stage (for StB36 and StG56). However, NO₃-N concentration significantly increased in the later stage (for StB36 and StG56). Carbon fractions had a similar increasing trend during natural vegetation restoration. The concentrations of POC, HS-C, FA-C and HA-C accounted for 24.5%–49.1%, 10.6%–15.2%, 5.8%–9.1% and 4.6%–6.1% of total carbon, respectively. For AbG3, the relative changes of POC, HS-C and FA-C were significantly higher than that of total carbon during the process of revegetation restoration. The higher relative increases in POC, HS-C and FA-C confirmed that soil carbon induced by vegetation restoration was sequestrated by higher physical and chemical protection. The increases of soil C fractions could also result in higher ecology function in semiarid grassland ecosystems.     

Assessing the effects of vegetation and precipitation on soil erosion in the Three-River Headwaters Region of the Qinghai-Tibet Plateau,China

Soil erosion in the Three-River Headwaters Region (TRHR) of the Qinghai-Tibet Plateau in China has a significant impact on local economic development and ecological environment. Vegetation and precipitation are considered to be the main factors for the variation in soil erosion. However, it is a big challenge to analyze the impacts of precipitation and vegetation respectively as well as their combined effects on soil erosion from the pixel scale. To assess the influences of vegetation and precipitation on the variation of soil erosion from 2005 to 2015, we employed the Revised Universal Soil Loss Equation (RUSLE) model to evaluate soil erosion in the TRHR, and then developed a method using the Logarithmic Mean Divisia Index model (LMDI) which can exponentially decompose the influencing factors, to calculate the contribution values of the vegetation cover factor (C factor) and the rainfall erosivity factor (R factor) to the variation of soil erosion from the pixel scale. In general, soil erosion in the TRHR was alleviated from 2005 to 2015, of which about 54.95% of the area where soil erosion decreased was caused by the combined effects of the C factor and the R factor, and 41.31% was caused by the change in the R factor. There were relatively few areas with increased soil erosion modulus, of which 64.10% of the area where soil erosion increased was caused by the change in the C factor, and 23.88% was caused by the combined effects of the C factor and the R factor. Therefore, the combined effects of the C factor and the R factor were regarded as the main driving force for the decrease of soil erosion, while the C factor was the dominant factor for the increase of soil erosion. The area with decreased soil erosion caused by the C factor (12.10×10³ km²) was larger than the area with increased soil erosion caused by the C factor (8.30×10³ km²), which indicated that vegetation had a positive effect on soil erosion. This study generally put forward a new method for quantitative assessment of the impacts of the influencing factors on soil erosion, and also provided a scientific basis for the regional control of soil erosion.     

Tobamoviruses of pepper,eggplant and tobacco: Comparative host reactions and serological relationships

Using test plants and serology six tobamoviruses of pepper (FO, Ob, P8, P11, P14 and SL) and one of eggplant (A1) were compared with common tobacco mosaic virus (TMV-WU1). WU1, A1 and FO were closely similar in their reactions inCapsicum spp. as were P14 and SL. Ob, P11 and P8 were also similar in this respect except inC. frutescens Tabasco in which P8 differed from Ob and P11.Using micro-precipitation tests the virus strains could be roughly divided into three serological groups: Group I consisted of WU1, group II of A1, FO, P8, P14 and SL, and group III of P11 and Ob. With ELISA group II was further divisible into two subgroups, including A1 and FO, and P8, P14 and SL.It was concluded that similarities of strains in their reactions inCapsicum spp., were not necessarily confirmed by their serological relationships.Samenvatting Zes tobamovirussen uit peper (FO, Ob, P8, P11, P14 en SL) en één uit aubergine (A1) konden met behulp van toetsplanten alle van elkaar worden onderscheiden. In hun reacties inCapsicum-soorten, kwamen A1 en FO sterk overeen met elkaar en met het gewone tabaksmozaïekvirus (WU1). Ob, P11 en P8, die in dit opzicht onderling veel overeenkomst vertoonden, verschilden duidelijk van alle andere. Hetzelfde gold voor P14 en SL.Ook met behulp van de micro-precipitatietoets konden de virusstammen in groepen worden ingedeeld. Groep I werd gevormd door WU1, groep II door A1, FO, P8, P14 en SL en groep III door P11 en Ob. Met behulp van ELISA kon groep II worden onderverdeeld in twee ondergroepen, namelijk A1 en FO enerzijds en P8, P14 en SL anderzijds.De nauwe serologische verwantschap van A1 met FO is conform de grote overeenkomst in waardplantreacties. Hetzelfde geldt voor P11 en Ob, wanneer we alleen hun reacties inCapsicum-soorten beschouwen. P8 echter, die wat het laatste betreft meer op Ob en P11 lijkt, vertoonde serologisch meer overeenkomst met P14 en SL. WU1 verschilde serologisch zeer sterk van alle andere onderzochte virusstammen.Geoconcludeerd kan worden dat de waargenomen overeenkomst tussen de onderzochte virusstammen in hun reacties inCapsicum-soorten niet altijd gesteund wordt door hun serologische verwantschappen.Guestworker from September 1981 till January 1982 as a fellow of the International Agricultural Centre, Wageningen, the Netherlands, from the Vegetable Crops Research Institute, Budapest, Hungary.Seconded to the Glasshouse Crops Research and Experiment Station, Naaldwijk, the Netherlands.     

Leafminers in vegetables,ornamental plants and weeds in Indonesia: Surveys of host crops,species composition and parasitoids

Extensive surveys of vegetable, ornamental and weedy plant species were conducted in highland and lowland vegetable production areas in Indonesia with the aim of recording leafminer species present and their associated natural enemies. The most common dipterous species reared from samples was the pea leafminer, Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae). This introduced pest was particularly serious in highland vegetables in Java, Sumatra and South Sulawesi, causing yield losses as high as 60-70%. Another alien species, the vegetable leafminer, Liriomyza sativae Blanchard, contributed to problems in lowland areas on the north coast of West Java, where cucumbers were heavily damaged. An Asian leafminer species, Chromatomyia horticola Goureau, was more common in snow peas (Pisum sp.). Intensive sampling of leafminer-infested leaves from surveyed host plants yielded 11 species of hymenopteran parasitoids: 10 eulophids (Asecodes sp., Chrysocharis sp., Cirrospilus ambiguus (Hansson and LaSalle), Closterocerus sp., Hemiptarsenus varicornis (Girault), Neochrysocharis formosa (Westwood), Neochrysocharis sp., Pnigalio sp., Quadrastichus sp., Zagrammosoma sp.) and 1 eucoilid (Gronotoma sp.). The most abundant parasitoid species was H. varicornis. Levels of parasitism varied among crops and growing seasons, but were usually low, especially on potato (< 3%). Surveys revealed that most farmers (63%) attempted to control leafminers by applying insecticides twice weekly although these applications were neither effective nor economical according to responses of about 72% of the farmers. An integrated pest management approach is suggested that emphasizes IPM training for vegetable farmers and includes reductionor elimination of broad spectrum chemicals that would adversely affect parasitoids that may already be present as well as those that may be introduced. The initiation of a classical biological control programme is recommended to enhance the limited parasitoid complex present in Indonesia and increase levels of biological control.