共查询到20条相似文献，搜索用时 0 毫秒
1.
Ilona Leyer 《河流研究与利用》2004,20(7):813-827
The effects of floodplain fragmentation by dykes on grassland vegetation were evaluated through field studies along the Middle Elbe River (federal states Saxony‐Anhalt and Brandenburg, Germany). Plant species composition was examined in 206 sites between 1996 and 1998 in the entire floodplain, which can be divided into the floodplain types ‘recent floodplain’, ‘older floodplain’ (which is separated from the recent one by dykes) and the ‘margin of the floodplain’ (which is the part of the older floodplain that forms the boundary and is furthest from the river). Dynamics in hydrology were examined weekly between November 1996 and February 1999 with the help of 40 water level wells which were installed near the studied sites. The hydrological parameters ‘average water level’, ‘average groundwater level’, ‘flooding duration’, ‘flooding depth higher 50 cm above soil surface’ and ‘standard deviation of the water level line’ were calculated to characterize the considered floodplain types and to relate species composition to hydrology. Furthermore several parameters of current management of the vegetation were recorded to evaluate the importance of land use versus hydrology for floodplain grasslands. Detrended and canonical correspondence analysis (DCA, CCA) were used to identify major environmental gradients governing the vegetation and to determine if there is a relationship between the different locations within the floodplain, variation in species composition, and gradients of measured environmental variables. The results indicate that the vegetation is closely related to a combination of water level fluctuations, which are different among the floodplain types, and soil moisture, while type and intensity of current management are not important in this context. The results of contingency tables underline the significance of dykes for the occurrence and absence of individual species among the floodplain types. The observed patterns can also be explained by the different hydrological properties of the recent and older floodplain as the results of logistic regression reveal. Furthermore, disturbance and dispersal processes and their alteration by dykes have to be taken into account to explain the pattern of species occurrence. Partial ordination detected residual differences in vegetation among the different floodplain types after accounting for the effects of the measured environmental variables. Grain size distribution is discussed as a further factor that might influence species composition. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
2.
Although soil seed banks are understood to be integral to the vegetation dynamics and restoration of many ecosystems, little is known of their role in riparian zones. In this study, we investigated soil seed banks of riparian zones of contrasting condition in an agricultural landscape and evaluated their potential to influence riparian restoration. We examined the composition and structure of germinable soil seed banks along lateral gradients from stream channels in both cleared and wooded riparian zones of three lowland creeks within the Goulburn Broken catchment in temperate southeastern Australia. Environmental correlates of soil seed bank characteristics and similarity to extant vegetation were also examined. We found an abundant and species‐rich soil seed bank mostly comprising propagules of perennial rushes and sedges and annual and perennial grasses with many species of annual forbs. While the majority of identifiable germinants and species were native, exotic species were common at all locations. Soil seed bank composition was relatively homogeneous among streams and along lateral gradients from the channel. Riparian condition (i.e. cleared or wooded), however, had a strong influence on soil seed bank composition and structure with cleared reaches containing more species, more germinable annual grasses and higher total numbers of germinable seeds. Soil seed bank composition was correlated with site openness suggesting that extant vegetation structure plays an important role in soil seed bank dynamics. Recruitment from the in situ soil seed bank will help restore only some components of the riparian plant community and may hinder restoration by introducing undesirable species. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
Floodplain habitats of the Xilin River in Inner Mongolia, China, were overgrazed by sheep and cattle until fencing of the floodplains was implemented in 2000. Carbon cycling of three plant communities of differing floodplain elevation after fencing showed that biomass in low‐elevation wetlands increased fastest until reaching its maximum at 20 years in the future, while a slower increase in biomass existed in high‐elevation and ‘hummock’ wetlands. Modelling and field experiments revealed differences between the three plant communities that were primarily attributed to different elevation levels and inundation periods. This study also determined the carbon sequestration capacity of the three floodplain wetland types (0.18 kg C m?2 year?1 in low‐elevation wetlands, 0.09 kg C m?2 year?1 in high‐elevation wetlands, and 0.05 kg C m?2 year?1 in hummock wetlands). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
4.
Streams and rivers constitute a dense network with a large interface to the surrounding landscape and are thus highly susceptible to anthropogenic pressures related to land‐use activities in adjacent riparian and upland areas. In the present study, we investigated the influence of catchment characteristics on potential propagule and species recruitment from sediment in lowland stream ecosystems. We tested the following hypotheses: (1) catchment characteristics affect species recruitment from stream sediment in both stream and riparian habitats and (2) recruitment of species associated with undisturbed fen‐meadow habitats is higher in places with natural vegetation in the riparian zones. A large number of wetland species emerged from the stream sediment and sediment recruitment and therefore can act as an important dispersal corridor for common species in stream ecosystems. The recruited propagules were dominated by terrestrial species, but amphibious and aquatic species also appeared, particularly in the artificial stream channels. These included among others species within the genera Ranunculus sp., Callitriche sp. and Potamogeton sp. The large between‐site differences in land‐use characteristics in the riparian zones of the studied stream reaches, both locally and along upstream reaches, were not reflected in species recruitment from the stream sediments. Thus, most recruited species were common and widely distributed, and they were dominated by species with ruderal and competitive life history strategies, whereas only few species associated with fen‐meadow vegetation were recruited. From these findings, we infer not only that hydrochorous dispersal of species can be a potential efficient dispersal vector in agricultural landscapes but also that limitations can exist as to which species can be recruited. We suggest that further studies are performed to elucidate this issue further. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
6.
Phytoplankton communities along the river Yamuna in Delhi stretch and its associated floodplain lakes showed considerable spatio‐temporal variations. Most of the species identified were cosmopolitan and typical of highly polluted rivers in tropical ecosystems. All the groups of phytoplankton with predominance of Cyanophyceae and some species of Chlorophyceae were distributed within the river stretch though with varying diversity and density. Relatively cleaner sites supported larger phytoplankton assemblages compared to those subjected to sewage outfalls and industrial effluents. Species elimination was observed mainly in the mid‐stretch and downstream of Okhla subjected to high loads of pollution. Co‐inertia analysis indicated significant co‐structures between water quality and species richness and density indicating water quality as the governing factor for phytoplankton distributions in the river stretch. Floodplain plays an important role in regenerating water quality thereby enhancing species richness and density. Floods play an important role in seasonal dynamics through dilution effects and promoting connectivity between river channel and floodplain lakes thereby facilitating species exchanges. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
7.
The aim of this study was to investigate and compare the flora and vegetation of three well‐preserved hardwood floodplain forest areas along the river Danube and to discuss whether possible differences between the floodplain forests can be linked to river eutrophication. Flora and vegetation data from three study areas located on the Upper, Middle and Lower Danube in Central and Eastern Europe were compared using univariate and multivariate statistical methods. Special attention was paid to floristic composition, plant functional types, and ecological indicator values. We found that the three studied hardwood floodplain forests appeared to be rather different regarding floristic composition and herb‐layer vegetation. Despite the high beta diversity, the distribution of the plant functional types indicated generally equal habitat conditions, which were quite stable. The diversity of herb‐layer vegetation decreased downstream, while the indicators of nutrient availability pointed to increasing nutrient supply. The factor light apparently played a minor role for herb‐layer diversity. There is a remarkable congruence between the results of our floodplain vegetation analysis and the longitudinal river eutrophication patterns as described in the literature. We conclude that the nutrient input into Danubian hardwood floodplain forests increased downstream, resulting in higher nutrient availability for plants. This promoted especially the growth of tall and competitive forbs, which outcompeted other plant species. Even if the importance of the various eutrophication patterns is difficult to quantify, our study provides evidence that anthropogenic eutrophication has a distinct effect on the flora and vegetation of Danubian hardwood floodplain forests. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
8.
Eric Tabacchi Eduardo Gonzlez Dov Corenblit Virginia Garfano‐Gmez Anne‐Marie Planty‐Tabacchi Johannes Steiger 《河流研究与利用》2019,35(8):1228-1240
Plant communities and dynamics can be characterized according to species composition or plant traits. Here, we used species composition and plant traits to compare their effectiveness in discriminating the biogeomorphological (involving reciprocal feedbacks between physical and biological processes) and ecological (mainly biologically driven) phases of the fluvial biogeomorphological succession (FBS) model. The comparison was done between two French rivers, the largely unchannelized lower Allier and the channelized middle Garonne. One reach representative of each river section was selected for the study. Within each river reach, we chose two contrasted study sites in terms of channel and floodplain dynamics: a reference site (least altered channel and floodplain dynamics) and an altered site (laterally stabilized by riprap and constrained). In the four study sites, we sampled vegetation in 402 plots of 4 m2. The 512 species identified in the plots were characterized in terms of plant traits (20) from a literature review. When comparing reaches in unconstrained ordinations and permutational multivariate analyses of variance, both species composition and plant traits led to a similar identification of the biogeomorphological and the ecological successional trajectories. Nevertheless, the trait approach was less influenced by local and regional bioclimatic, hydrogeomorphological, and anthropogenic settings and thus produced a more comprehensive and general classification of the biogeomorphological and ecological phases of the FBS model. A lower than expected contrast between the four sites was found, because neither species composition nor plant traits could entirely characterize distinct successional trajectories occurring in our reference or altered sites. Furthermore, our results contributed to a better understanding of the multiple successional trajectories that can occur in midlatitude river corridors. It also showed that relating plant traits to their effects on fluvial landform dynamics remains a core challenge in explaining succession including feedback mechanisms between hydrology, morphodynamics, and vegetation dynamics. 相似文献
9.
L. A. Toth 《河流研究与利用》2015,31(10):1319-1327
An understanding of the processes that determine plant community structure is a requisite for the planning and evaluation of restoration efforts on river floodplains. Variable disturbance regimes derived from flood pulses increase the susceptibility of river floodplains to colonizations by new species and establish invasibility as a potentially important factor in plant community assembly and dynamics. The role of invasibility in the restoration of a wet prairie community on the Kissimmee River floodplain in central Florida was evaluated by quantifying temporal species turnover rates during wet and dry season sampling over a 12‐year pre‐restoration and post‐restoration period. Turnover rates increased with reestablishment of annual inundation regimes and were significantly greater on the reflooded floodplain than on the drained, channelized floodplain. Recurrent periods of increased invasibility were associated with repeated high‐amplitude flood pulses and accompanied by increased diversity of plant communities within the wet prairie landscape. Neither invasibility nor beta diversity was strongly related to the variable hydroperiods or depths provided by local topography and restoration of seasonal hydrologic regimes. Results suggest that invasibility is a functional process by which the restored flood pulse has reestablished the structure and diversity of the wet prairie. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
Dams may impact the health of downstream riparian vegetation communities through flow modifications such as decreased flood frequency and duration. Without historical vegetation data, however, it is difficult to relate changes in vegetation composition to hydrology patterns downstream of dams. We studied bottomland hardwood forests downstream of Toledo Bend Dam on the Sabine River in Texas and Louisiana to determine their sensitivity to minor changes in river hydrology with a particular focus on floods. Current riparian vegetation was characterized within three topographic zones at three selected sites below the dam. Using 80 years of hydrologic records from two gauging stations downstream of the dam, we evaluated trends in flood frequency, flood duration, peak discharge and total flood discharge in those periods before (1926?1965) and after (1971?2005) dam construction, as well as related flood stage to floodplain elevations to link topography to flood frequency. Plant species diversity in this system is highly dependent on minor changes in elevation, and the proportion of wetland‐dependent species changes rapidly with only a few centimeters difference in elevation. Although 50% of trees, shrubs and herbs in the sloughs were wetland adapted, their numbers were only 21% in the levees (74–284 cm higher in elevation) and 14% in the mid‐floodplains. Since dam construction, total flood discharge and duration at the most upstream gauge on the Sabine River decreased by 49%. At both gauges, mean discharge was also altered with higher summer flows. Patterns of tree regeneration point to less recruitment by wetland‐dependent species in the years following dam construction. These results suggest that minor changes in flood magnitude might limit occurrence of wetland species to the lowest topographic zones and illustrate the need to analyse sensitivity of plants to minor changes in flood characteristics when historical data for the vegetation community are lacking. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
11.
Management methods to control or eradicate invasive alien species should be guided by research into their efficacy in relation to the target species as well as their wider effects on the community. Impatiens glandulifera Royle (Balsaminaceae) is an invasive alien species, which has spread rapidly across Europe and North America, particularly colonizing riverbanks, wet woodlands, and wastelands. The effectiveness of two mechanical control measures and their impacts on community plant species richness and diversity within the riparian zone of the urban river Brent, London, England, was assessed. Over 2 years, an experiment was performed across three sites that exhibited contrasting levels of invasion of I. glandulifera: high, moderate and low. The experiment involved three treatments on replicated plots at all three sites: pruning at 6‐week intervals, weeding at 6‐week intervals, and a control. The effects of these control measures were most clearly seen at the site with the highest level of invasion and, to a smaller extent, at the moderately invaded site. Weeding was more successful in controlling the species than pruning, and the greatest impact of these treatments on community plant species richness and diversity was only apparent after 2 years of the experiment. Although seedlings of 10 other alien species were found, there was no evidence that their presence on the plots was detrimental to native species during the experimental period. Three common native species each approached 10% cover on the weeded plots at the heavily invaded site by the end of the experiment: Poa annua, Rumex obtusifolius, and Urtica dioica. These assessments provide guidance for implementing mechanical control of I. glandulifera in riparian zones. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
12.
阿什河某支流河岸带植物群落多样性差异研究 总被引：1，自引：0，他引：1
本文对阿什河某支流不同区域河岸带植物多样性和植物群落结构差异进行了研究。从α多样性上来看,上游和中游河岸带物种丰富度和均匀度差异不显著,下游丰富度指数明显低于中上游;从稳定性上来看,河岸带植物群落结构稳定性为下游 < 中游 < 上游;草地早熟禾为本流域中各区域河岸带植被的优势种群,上游受外界影响及水力冲刷较小,植物有向陆生演替的趋势,下游受外界影响及水力冲刷较大,植物有向水生及耐冲刷物种演替的趋势。 相似文献
13.
为探究北方缺水地区湿地植物物种多样性变化,选取北京市延庆区妫水河为研究区,采用物种丰富度(R),Shannon-Wiener指数(H),Simpson指数(D)和Peilou均匀度指数(J)作为植物群落多样性指标,使用方差法和典型对应分析(CCA)对不同河段和区域间湿地植物物种分布与环境因子之间的响应关系进行研究。研究结果表明:研究区现有湿地植物93种,隶属于44科76属,优势科有菊科(Asteraceae)、禾本科(Poaceae)、豆科(Fabaceae)和莎草科(Cyperaceae); 93种植物的Shannon-Wiener指数(H)小于3,Simpson指数(D)和Peilou均匀度指数(J)介于0. 5～0. 75之间,物种数量总体不多,但分布较均匀,处于中等水平;对湿地植物群落形成及生长影响较大的水质因子依次为全氮(TN)、p H和化学需氧量(COD)。 相似文献
14.
In this study, we compare the ability of two riverine flood control approaches: channelization and stream preservation/setbacks, to alleviate the adverse impacts of rapid urbanization. To study the effects of structural intervention and urban development on the evolution of the floodplain, we have chosen two neighboring urban watersheds in Houston, TX: Brays Bayou and Buffalo Bayou. While the two watersheds are similar in size, topography, and development level, they have contrasting riverine flood management approaches. Brays Bayou is channelized, whereas Buffalo Bayou remains mostly unchannelized. We use the distributed hydrologic model, Vflo®, and the hydraulic model, HEC‐RAS, to analyze channel hydraulics and floodplain extent in the two watersheds under the 10‐ and 100‐year rainfall scenarios at three points in time: 1970s (early development), 2011 (current development), and 2040 (future development). We find that, while floodplain extent in both watersheds increases over time, the relative change in floodplain extent for Brays Bayou (channelized) is substantially larger than that for Buffalo Bayou (unchannelized). The results in this study contribute to a better understanding of the long‐term performance of two flood mitigation approaches (channelization and setbacks) on riverine flood risk and provide insight into best management practices for cities experiencing rapid urban growth. 相似文献
15.
天津滨海新区湿地植物群落特征及植被演替过程 总被引：1，自引：0，他引：1
为了研究滨海新区湿地植物的特征和生态效益,更好的了解湿地植物群落的价值,研究了湿地植物的种类及区系组成、植物多样性及其分布、湿地植被的演替规律,研究得出本区湿地植物种类较多,共232种,科属种分布广泛,植物丰富度较高,均匀度一般,湿地植物受水盐程度影响较大,演替过程主要由水盐程度主导;水分多时向湿生水生植物演替如碱菀、芦苇等,水分少盐度高时多发生向中生盐生植物的演替如獐毛等。 相似文献
16.
土壤机械组成是土壤最基础的资料之一,在土壤结构性等方面扮演重要角色,它受到成土母质、气候、地形、生物和人类活动等因素影响。根据《中国土种志》及部分地方土壤志记载的333个红壤剖面数据,研究了红壤机械组成受成土母质和土地利用的影响程度。结果表明:成土母质和土地利用均可以对红壤机械组成产生影响;成土母质与土地利用相比,前者对于红壤机械组成的影响更为深刻;土地利用对红壤机械组成影响不大。成土母质对红壤机械组成的解释程度随着深度的增加而增大,可解释红壤机械组成变异的25%左右。研究成果可为红壤性质的研究以及红壤的改良与农业利用提供理论支持。 相似文献
17.
以南水北调北京段PCCP管线工程的植被恢复区为研究对象,基于南水北调中线北京段PCCP管线工程特点及其穿越地区的环境特点,通过野外调查与室内分析方法,对不同植被恢复措施的植被配置模式以及草本植物多样性和生物量进行了研究。结果表明:工程绿化模式在短期内能取得较好的恢复效果,复层和混交模式下草本植物多样性指数和生物量均较高;封育模式的草本植物生物量大但是种类较少;复耕复林模式下的草本植物多样性指数和生物量则较为平均和稳定。 相似文献
18.
Claudia Angiolini Leopoldo de Simone Tiberio Fiaschi Giuseppe Pio Cifaldi Simona Maccherini Emanuele Fanfarillo 《河流研究与利用》2023,39(8):1616-1628
In riparian forests, clear-cutting causes long-lasting changes in both riparian and aquatic biota. In this work, we examined if past clear-cutting events occurred at different times have imprints on riparian forests in a Mediterranean river in central Italy. We carried out a randomized, plot-based vegetation survey of riparian forests in systematically sampled 500 m-long sectors along the whole river, dividing the riparian zone into two internal and two external strips. From historical aerial photos, past clear-cutting events within plots were detected and classified in age classes: (i) cut in the past 8 years (recent); (ii) cut between 8 and 19 years ago (intermediate); (iii) no signs of clear-cutting in the last 19 years (distant). We analyzed the responses of vegetation to clear-cutting and strip position. Alien species richness was higher and woody species richness was lower in recently clear-cut areas compared to those with a distant clear-cutting event. Moreover, recently cut woods had more alien and synanthropic species. Intermediate clear-cut areas had higher levels of invasion by alien species compared to areas with distant cut. Riparian forests of internal strips are impacted by clear-cutting, but seem to recover in 8–19 years thanks to their natural resilience. Conversely, recent or intermediate clear-cutting events did not affect any of the investigated vegetation attributes in the external strips since such forests were already invaded by alien and synanthropic species after human disturbance. Our results confirm that clear-cutting events can have long-lasting effects on Mediterranean riparian forests, confirming the vulnerability of river ecosystems to clear-cutting and suggesting the need for more caution in management practices to improve the conservation status of riparian forests. 相似文献
19.
20.
土壤侵蚀是内蒙古自治区十大孔兑区域最严重的环境问题之一。为该区域生态环境的健康发展,本研究基于多源数据结合多种土壤侵蚀模型对2021年十大孔兑区域的土壤侵蚀做出评估,评估结果显示：2021年十大孔兑区域土壤侵蚀面积为4398.85 km2,占区域总土地面积的40.86%,其中轻度、中度、强烈、极强烈和剧烈等级的土壤侵蚀面积分别为2614.38 km2、1328.74 km2、276.29 km2、194.45 km2和40.15 km2,区域整体以中度和轻度侵蚀为主。基于评估结果本研究总结了十大孔兑区域土壤侵蚀的空间分布特点,并综合多因素对侵蚀特征进行分析,最终得到如下结论：(1)十大孔兑区域的水力侵蚀离散分布于孔兑上游,这是由地形地貌、植被覆盖等多个因素共合同作用导致的,其中地形地貌对侵蚀分布的影响相对较大;(2)十大孔兑区域的风力侵蚀聚集分布于孔兑中下游,中游的库布齐沙漠是孔兑中风力侵蚀最为严重的区域,风力侵蚀的分布受到土地利用类型和植被覆盖的影响较大;(3)十大孔兑区域的土壤侵蚀集中在达拉特旗、东胜区和杭锦旗境内,但由于各县区部分覆盖的侵蚀地貌不同,各县区在水力和风力侵蚀面积占比上有很大差异。 相似文献