首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
As dams across the country continue to age, successful restoration of dewatered reservoirs remains a critical factor in decisions regarding dam removal. Freshly exposed reservoir sediment may not support rapid reestablishment of native plant species due to poor fertility or absence of arbuscular mycorrhizal fungi propagules. This field study evaluated treatment effects involving combinations of native plants, mycorrhizal inoculum, and mulch on restoration of dewatered reservoir sediment over 20 months. Most plants, even those uninoculated, became mycorrhizal. In all treatments, sediment pH decreased, as did nitrogen and organic matter, compared to original reservoir sediment, while aggregate stability doubled from original anaerobic sediment. Revegetated plots with mulch had significantly greater vegetation cover and more native volunteer species compared to plots without mulch. The planted mulch treatment also decreased plot runoff tenfold, reducing erosion to the same degree. Indicators suggest that the primary benefit of mulch resulted in increased moisture retention making the planted mulch treatment most successful for restoration of reservoir sediment due to extensive native plant growth, improved soil characteristics, and reduced runoff and erosion compared to nonmulched plots. While results from this plot‐scale study suggest commercial mycorrhizal inoculum is unnecessary since natural inoculum sources sufficiently colonized plants, reservoir‐scale restoration may require creation of additional source areas to encourage rapid reestablishment of native plants and mycorrhizal fungi.  相似文献   

2.
1. The single station diel oxygen curve method was used to determine the response of system metabolism to backfilling of a flood control canal and restoration of flow through the historic river channel of the Kissimmee River, a sub‐tropical, low gradient, blackwater river in central Florida, U.S.A. Gross primary productivity (GPP), community respiration (CR), the ratio of GPP/CR (P/R) and net daily metabolism (NDM) were estimated before and after canal backfilling and restoration of continuous flow through the river channel. 2. Restoration of flow through the river channel significantly increased reaeration rates and mean dissolved oxygen (DO) concentrations from <2 mg L−1 before restoration of flow to 4.70 mg L−1 after flow was restored. 3. Annual GPP and CR rates were 0.43 g O2 m−2 day−1 and 1.61 g O2 m−2 day−1 respectively, before restoration of flow. After restoration of flow, annual GPP and CR rates increased to 3.95 O2 m−2 day−1 and 9.44 g O2 m−2 day−1 respectively. 4. The ratio of P/R (mean of monthly values) increased from 0.29 during the prerestoration period to 0.51 after flow was restored, indicating an increase in autotrophic processes in the restored river channel. NDM values became more negative after flow was restored. 5. After flow was restored, metabolism parameters were generally similar to those reported for other blackwater river systems in the southeast U.S.A. Postrestoration DO concentrations met target values derived from free flowing, minimally impacted reference streams.  相似文献   

3.
植被恢复对干热河谷退化土壤改良的影响   总被引:5,自引:0,他引:5  
唐国勇  高成杰  李昆 《生态学报》2015,35(15):5157-5167
土地退化和土壤恶化是我国干热河谷主要环境问题。树种筛选及树种与土壤关键限制因子间的相互作用是生态恢复的基础和前提。对比研究了干热河谷地区植被恢复22年间不同时期(1991、1997、2005和2013年)5种人工林(新银合欢Leucaena leucocephala,苏门答腊金合欢Albizia kalkora,大叶相思Acacia auriculiformis,印楝Azadirachta indica和赤桉Eucalyptus camaldulensis)和1种自然恢复样地中土壤主要物理、化学和微生物性质。结果表明植被恢复处理和取样时间对土壤性质有显著影响。在22a的植被恢复期内,土壤物理性质提高幅度为3.0%—20.2%,远不及土壤微生物和化学性质。通过自然恢复机制改良的退化土壤,其改良率(63.6%)高于印楝(54.9%)、苏门答腊金合欢(54.3%)和赤桉(53.2%)人工林,但改良率不及新银合欢(68.2%)和大叶相思(67.3%)人工林。研究得出造林树种类型决定干热河谷土壤改良进程。与自然恢复相比,人工植被恢复(如造林)并不一定能加速退化土壤改良。新银合欢和大叶相思适合作为改良干热河谷退化土壤的先锋树种,而生态系统自然恢复也可作为改良干热河谷退化土壤的一种适宜方式。  相似文献   

4.
Restoration of the Kissimmee River should have multiple ecological benefits including improved dissolved oxygen (DO) within the river channel. Channelization of the Kissimmee River virtually eliminated flow through the natural river channel. After channelization, chronically low DO concentrations were observed in the stagnant remnant channel. Although no DO data from before channelization exist, reference estimates of pre‐channelization conditions were derived from seven relatively unimpacted streams. Stations along the Kissimmee River were sampled for 3 years before construction of the first phase of the restoration project began and for up to 8 years after the completion of construction. After Phase I construction, DO concentrations in the area of the river channel to which flow had been restored increased significantly from 2.2 to 4.9 mg/L, which is similar to DO concentrations observed in the reference streams. Mean DO concentrations for the reference streams ranged from 4.6 to 6.7 mg/L. Comparison of reference data to data from the pre‐Phase I and post‐Phase I system suggests that channelization had a negative impact on DO and that DO concentrations in the post‐Phase I Kissimmee River channel have made a significant recovery. Long‐term data trends demonstrate that DO concentrations can be negatively impacted by high flow events and that recovery from these events is generally quick, suggesting some degree of resilience in the system.  相似文献   

5.
Abstract Interest in restoring native ecosystems is resulting in conversion of marginal agricultural lands to bottomland hardwood‐dominated forests in the midwestern and midsouthern United States. Growing stock for these efforts typically consists of planted oak (Quercus spp.) and volunteer vegetation. Reports of mixed reforestation success and the lack of post‐establishment tree growth data prompted this evaluation of vegetation characteristics of 5‐ to 7‐year‐old operational restorations in the Lower Cache River Watershed in southernmost Illinois, U.S.A. Fraxinus pennsylvanica (green ash), Acer negundo (box‐elder), and Liquidambar styraciflua (sweetgum) together comprised 77% of all tree stems observed. Full stocking of overstory tree species can be expected to produce a closed canopy stand within 160 m of a forested edge, due primarily to the abundance of rapidly growing volunteer‐origin trees. Planted oaks contributed minimally to total tree stocking but were present in sufficient numbers to eventually improve wildlife habitat, and therefore satisfied restoration objectives. Oak height was 23% greater when in the presence of a non‐oak tree species. Herbaceous cover was dominated by Solidago gigantea (late goldenrod) and Juncus spp. (rushes). Solidago gigantea was associated with poor growth and low density of non‐oak stems, whereas Juncus dudleyi (Dudley's rush) was associated with taller non‐oak stems. These results suggest that the presence of volunteer‐origin trees is crucial for the creation of full stand stocking that will result in rapid development of a closed canopy forest. Improved success of future reforestation efforts will require more intensive methods to establish adequate stocking beyond 160 m of a forest edge. Methods described here could be adapted for agricultural field to forest restorations in other regions to predict critical distances from volunteer seed sources within which supplemental planting would be unnecessary to meet tree stocking objectives.  相似文献   

6.
In the Mississippi River Alluvial Valley (MAV), complete alteration of river‐floodplain hydrology allowed for widespread conversion of forested bottomlands to intensive agriculture, resulting in nearly 80% forest loss. Governmental programs have attempted to restore forest habitat and functions within this altered landscape by the methods of tree planting (afforestation) and local hydrologic enhancement on reclaimed croplands. Early assessments identified factors that influenced whether planting plus tree colonization could establish an overstory community similar to natural bottomland forests. The extent to which afforested sites develop typical understory vegetation has not been evaluated, yet understory composition may be indicative of restored site conditions. As part of a broad study quantifying the ecosystem services gained from restoration efforts, understory vegetation was compared between 37 afforested sites and 26 mature forest sites. Differences in vegetation attributes for species growth forms, wetland indicator classes, and native status were tested with univariate analyses; floristic composition data were analyzed by multivariate techniques. Understory vegetation of restoration sites was generally hydrophytic, but species composition differed from that of mature bottomland forest because of young successional age and differing responses of plant growth forms. Attribute and floristic variation among restoration sites was related to variation in canopy development and local wetness conditions, which in turn reflected both intrinsic site features and outcomes of restoration practices. Thus, understory vegetation is a useful indicator of functional progress in floodplain forest restoration.  相似文献   

7.
In this study, effect of ecological water diversion on vegetation restoration in the lower reaches of Tarim River is assessed by coupling remote sensing techniques and a field-based survey. Land use/cover and fractional vegetation coverage (Fvc) maps derived from remote sensing images, ground validation data, and hydrological observation data are adopted to analyze the responses of Ecological Water Diversion Project (EWDP). The results indicate that, the EWDP has showed a positive effect on vegetation restoration in the lower part of Tarim Basin. During 2001 to 2013, transformation from unused land to nature vegetation (i.e. forest land, grassland and scrubland) was the major process of land use/cover change; the area of natural vegetation showed a 4.7% increase, and the area of unused land reduced by 6.8%. Landscape patch size was decreased, the degree of fragmentation and diversity of landscape was increased, and landscape structure in the study area became more complex. Moreover, vegetation coverage promoted from 2001 to 2013; average Fvc in 2013 was 1.5 times greater than that in 2001. The results can provide not only an accurate assessment for the EWDP, but also a visual insight for the water resources management practices in the study area, such that the sustainability for local ecosystem can be facilitated.  相似文献   

8.
Abstract Cades Cove, Great Smoky Mountains National Park, U.S.A. was historically cleared largely for pastoral purposes; it is now comprised of recently abandoned pastures dominated by non‐native pasture species. To investigate the potential for reducing non‐native species relative to native species, park managers initiated an experiment in 1995 that included mowing, herbicide application, planting of seed, and burning of replicate 20 × 50–m plots at each of two sites within Cades Cove. Between 1995 and 2001 we evaluated the response of the plant community (i.e., species‐specific cover and frequency, biomass, diversity) to this suite of treatments and compared it with unmanipulated control plots at each site. Four years after treatment initiation abundance measures of Plantago lanceolata, Setaria geniculata, and Trifolium spp. averaged one‐third lower in treated than control plots. Frequency of Festuca pratensis was lower in treated than in control plots for 2 years, but after 4 years its frequency, cover, and biomass did not differ between treated and control plots. By 2000 the cover of Sorghastrum nutans in treated plots increased to 23–47%, depending on the site. Total biomass and diversity increased in treated plots. The dominance of Lespedeza cuneata at one site apparently reduced planting success, biomass production, and diversity and evenness. Post‐treatment lags in response for several species, coupled with interannual variation in response to environmental conditions, suggest that evaluations of treatment success would differ greatly depending on when the evaluation was conducted.  相似文献   

9.
Man-made changes in the hydrological regime of South Florida have significantly altered the conductivity and ionic composition of water in the Shark River Slough system of Everglades National Park. The shift in water inputs from unregulated marsh water flow to regulated delivery of canal water has resulted in a 140% increase in conductivity and 149% increase in total ionic concentration since the early 1960s. Associated with this change has been a 300–400% increase in sodium and chloride concentrations in the waters entering the Shark River Slough of Everglades National Park.  相似文献   

10.
新安江屯溪水力自控翻板坝蓄水期浮游植物的变化研究   总被引:1,自引:0,他引:1  
2006年3月至4月底,在新安江屯溪水力自控翻板坝蓄水期和非蓄水期定点进行浮游植物调查,共采集到浮游植物39属种,隶属于4门。主要优势种为硅藻和绿藻。蓄水期的藻类丰度高于非蓄水期。依据调查结果选用"污染指示种"对翻板坝上游水域水质污染状况进行评价,结果表明:新安江屯溪城区段水质属乙型中污水。  相似文献   

11.
基于地下水恢复的塔里木河下游生态需水量估算   总被引:4,自引:0,他引:4  
白元  徐海量  张青青  叶茂 《生态学报》2015,35(3):630-640
为探明生态输水后地下水响应带范围及地下水恢复下生态需水量,以塔里木河下游大西海子水库至台特玛湖段为研究区,基于2000—2010年生态输水和地下水埋深分布特征,分析了塔里木河下游生态输水后两岸地下水位恢复状况,并借助遥感和地理信息系统技术对研究区生态需水量进行了研究。结果表明:塔河下游地下水位的抬升幅度与输水量的大小呈一定的正相关关系,并存在一定的时效性。2004—2010年地下水处于长期的负均衡状态,多年下降幅度明显。塔河下游英苏、喀尔达依、阿拉干和依干不及麻断面地下水响应幅度分别为1195、1050、2281 m和1000 m。历经11a输水后,塔里木河下游地下水总恢复需水量为7.06×108m3,其中,齐文阔尔河段为4.98×108m3,老塔里木河段为2.09×108m3,地下水恢复至生态水位4.5m需要5—8a的时间。保护塔里木河下游大西海子以下所有天然植被面积(96114.09 hm2)的生态需水量为0.587×108m3,保护下游地下水响应带天然植被面积(41439.85 hm2)的生态需水量为0.21×108m3。  相似文献   

12.
Jilmoe Moor, a montane peatland found in Mt. Odae National Park, Korea, has been influenced by a surrounding pasture-land for more than 30 years. Here, we used multivariate analyses to study the vegetation structure at that Moor. Four distinct communities were consistently separated (82.2% of the total variance): two wetland communities --Sphagnum palustre (SP) andPersicaria nepalensis-Persicaria thunbergii (PNPT). In addition, we recorded two invaded upland communities:Phleum pratense (PP) andFestuca ovina-Artemisia feddei (FOAF). Of those pasture species, timothy (Phleum pratense) was most dominant in all wetland communities except SP. Our data demonstrate that the pasture has affected the settlement and expansion of two pasture communities on the moor by acting as a propagule source and also through the input of nutrients in the form of fertilizer and waste from cattle. Moreover, this enrichment of the moor habitat may have facilitated replacement of the original wetland community. That is, its unusually high levels of phosphorus and potassium may have resulted in the dominance ofPersicaria nepalensis, andP. thunbergii, which often occur on nutrient-rich sites. Therefore, proper policies should be enacted to restore Jilmoe Moor as a montane peatland by eliminating the effect of the surrounding pasture.  相似文献   

13.
许炯心 《生态学报》2005,25(6):1233-1239
以退耕还林还草为主要内容的大规模的生态环境建设正在我国兴起,如何进行科学的植被配置规划,是一个急待解决的理论和实践问题。以自然植被初级生产力(NPP)表征潜在的即最大可能的植被条件,并与现在的森林覆盖率分布以及植被构成特征进行了比较。通过大量实测资料的分析,查明了降水条件对森林覆盖率和NPP的影响及其临界条件。研究表明,以NPP表征的天然植被特征值在黄土高原地区的分布具有显著的地带性。NPP与年平均降水量的关系中存在着两个临界点,分别代表着植被类型的变化,Pm=250mm可视为荒漠与草原植被之间的临界点,而Pm=480mm则为草原(森林草原)与森林(落叶阔叶林)之间的临界点。尽管次生的人工植被受人为因素的控制,由于存在着自然稀疏化过程,将使人工林地最终达到某种与水分承载能力相一致的平衡状态,自然条件如年降水仍然是决定其覆盖度的重要因素。在森林覆盖率与年平均降水量的关系中表现出一个临界点。当Pm<480mm时,森林覆盖率很低,且随年降水的增大而增大的速率很慢;当Pm>480mm时,森林覆盖率随年降水量而急剧增大。人为建造的水土保持植被,是一个自然的人工生态系统,也是一个自组织系统,它通过自我调节而趋向于达到某种平衡,建立一定的群落结构甚至于趋向于某种顶极群落,从而实现乔木、灌木、草本植物组成的最优组合。从这一原理出发,提出了一个基于实测资料进行统计分析的方法,来确定使乔木面积在乔木、灌木、草本总面积中的最优或较优的比例,得出了具体的数据。  相似文献   

14.
Ecological restoration has become increasingly important in conservation. Yet, synthesized statistics are scarce with respect to essential characteristics of restoration activities. We surveyed restoration stakeholders in the U.S. states of Arizona and California to evaluate key attributes in restoration activities including ecosystems of focus, goals, size, cost, duration, and the prevalence of recommended restoration practices. We also examined how some of the attributes varied with size of restoration, ecosystem type, and state identity. While enhancing biodiversity and increasing plant cover were common goals in the two states, restoration in California also focused more on wildlife habitat re‐establishment and weed control. Restoration in Arizona was implemented more in arid/semiarid systems, larger in size, shorter in duration, used more passive restoration, spent more on equipment, and was less likely to source plants from native plant nurseries. Labor was the most expensive restoration component regardless of state identity and ecosystem type. Per unit area cost of restoration decreased with increasing size of restoration. Yet, the decline in this cost was more strongly explained by moving from mesic to arid/semiarid ecosystems. Duration of restoration projects increased with size of restoration and in more mesic ecosystems. Overall, restoration in mesic ecosystems, compared to arid/semiarid systems, was smaller in size, higher in cost, and longer in duration. These results confirmed that ecological and socio‐political conditions impact restoration goals and practice, with implications of how research can further support practitioners to achieve restoration success under practical constraints revealed by these results.  相似文献   

15.
Dissolved organic carbon (DOC) concentration and dissolved organic matter (DOM) character were investigated in soil water (15 and 40 cm) and streams at eleven sites in Olympic National Park. In addition, the effect of added nitrogen on soil water DOM concentration and composition was tested. Forested plots covering a gradient of precipitation, climate, slope, and aspect in Olympic National Park were fertilized with the addition of 20, 10 and zero (control) kg urea-N ha–1 y–1. Seven sites had the two different fertilizer treatments and control plots, while the additional four sites had no fertilizer treatments. Soil water DOC concentrations ranged from 0.5 mg C/L to 54.1 mg C/L, with an average value of 14.1 mg C/L. Streams had low DOC concentrations ranging from 0.2 mg C/L to 4.4 mg C/L, with an average value of 1.2 mg C/L. DOM composition was examined with regard to molar ratios, H:C, O:C and N:C, index of unsaturation, average carbon oxidation state, and specific absorbance. Fertilizer had no consistent effect on either DOM concentration or composition across the study sites. Soil depth influenced both DOM concentration and composition. Shallow soil water DOM had greater concentrations, higher specific absorbance, a higher degree of unsaturation, and had lower molar ratios compared to deep soil water samples. Overall, changes in DOM stoichiometry and specific absorbance as a function of soil depth were consistent despite the diversity of the forested study sites sampled.  相似文献   

16.
We report on spontaneous and directed succession on a dry sandy landfill site of low fertility at Berlin‐Malchow, Germany. Changes in species composition and cover were followed on unmown and mown permanent plots of 2 × 2 m size through 5 years of vegetation development. Species richness on unmown plots was relatively constant during the time of observation, with 20 to 25 species per 4 m2. Total cover of unmown plots continuously increased from approximately 10% in the first year to 80% in the fifth year. There are no clearly discernible sequential successional stages until present. The species composition includes species of all life forms, which colonized the site immediately after the initiation of the succession process representing the initial floristic composition type of vegetation development. However, perennial grasses and herbs gradually increased in cover up to approximately 40%. Woody plants were also present from the first year of succession and increased up to more than 20% cover in the fifth year, forming a shrub layer (>0.5 m) after the second year. Mowing significantly increased species richness, which was evident from the third year onward. This effect was mainly due to the reduction of the tall perennial grass Calamagrostis epigejos. Solidago canadensis and woody species were also significantly affected (lower cover and height), whereas short perennial herbs like Plantago lanceolata and Trifolium repens benefited from mowing.  相似文献   

17.
The hypothesis that temperate stream fishes alter habitat use in response to changing water temperature and stream discharge was evaluated over a 1 year period in the Neosho River, Kansas, U.S.A. at two spatial scales. Winter patterns differed from those of all other seasons, with shallower water used less frequently, and low‐flow habitat more frequently, than at other times. Non‐random habitat use was more frequent at the point scale (4·5 m2) than at the larger reach scale (20–40 m), although patterns at both scales were similar. Relative to available habitats, assemblages used shallower, swifter‐flowing water as temperature increased, and shallower, slower‐flowing water as river discharge increased. River discharge had a stronger effect on assemblage habitat use than water temperature. Proportion of juveniles in the assemblage did not have a significant effect. This study suggests that many riverine fishes shift habitats in response to changing environmental conditions, and supports, at the assemblage level, the paradigm of lotic fishes switching from shallower, high‐velocity habitats in summer to deeper, low‐velocity habitats in winter, and of using shallower, low‐velocity habitats during periods of high discharge. Results also indicate that different species within temperate river fish assemblages show similar habitat use patterns at multiple scales in response to environmental gradients, but that non‐random use of available habitats is more frequent at small scales.  相似文献   

18.
王凯利  王志慧  肖培青  王铁生  张攀 《生态学报》2022,42(20):8352-8364
为了科学评价黄土高原林草措施的可持续性,基于林草生态系统蒸散发(ET)与降雨补给之间的水量平衡动态关系,开展林草植被覆盖度恢复潜力研究具有一定的现实意义。利用实测水文气象要素数据和PML_V2 ET、GRACE和MOD13 A1 EVI等遥感产品,阐明了增强型植被指数(EVI)与ET的时空变化特征,构建了ET和EVI的定量响应关系,定量估算了不同降雨情景下黄土高原林草植被覆盖度恢复阈值与恢复潜力。研究结果表明:(1)PML产品基于通量站点观测值与水量平衡公式验证的误差分别为4.5 mm/8d、34.3 mm/a,产品精度优于MOD16 A2 GF。黄土高原2000—2018年多年平均ET为445.36 mm,多年平均EVI为0.17;黄土高原林草植被ET和EVI的增长速率分别为5.08 mm/a和0.0026/a。(2)利用多元逐步回归方法逐像元构建了ET与气象要素和EVI的最优响应关系模型,平均均方根误差(RMSE)为44.5 mm。(3)丰水年、平水年、枯水年不同降雨情景下黄土高原林草植被覆盖度平均恢复阈值为(71.5±37.3)%、(55.6±35.9)%和(22.4±26.0)...  相似文献   

19.
湿地是自然界最富生物多样性的生态景观和人类社会赖以生存和发展的环境之一,对维护生态系统功能和区域生态安全有着重要意义。为阐明不同湿地恢复方式对土壤和植被的影响,以黑河中游地区张掖国家湿地公园为研究对象,比较了自然恢复方式、恢复利用方式和恢复保护方式下植物多样性、植物生长状态、土壤pH、盐分、容重、水分含量、有机碳、全氮、全磷、速效氮、速效磷的变化特征,研究结果表明:在自然恢复方式下,湿地各层土壤全磷、土壤速效磷、土壤速效氮、物种多样性值最高,反映出自然恢复方式可能成为干旱区土壤磷固存的有效手段,适当干扰可能成为干旱区提高物种多样性的有效方法;恢复保护方式下,湿地植物多度最高165.67±25,表明恢复保护方式有助于植被的生长繁殖;恢复利用方式下,湿地各层土壤含水量、土壤有机碳、土壤全氮、植被盖度值最高,土壤盐分含量、土壤pH值最低,湿地物种多样性较高。表明恢复利用方式可以有效降低湿地土壤盐分,提高土壤碳、氮含量的潜力,适当人为管理可能成为干旱区湿地恢复过程中提高湿地物种多样性的有效管理方法。该研究结果对于干旱区湿地恢复、保护与重建的效应评估和恢复方式的选择提供一定的理论支持和决策参考。  相似文献   

20.
We analysed the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the water, sediments, fish and plants of the River Hindon, U.P., India, at seven sampling stations, in the year 1982. Considerable variation in concentration between water, sediments, fish and plants were noted. The concentration in the water was in the order Fe > Zn > Cr > Mn > Cu > Pb > Ni > Co > Cd, in the sediments, Fe > Mn > Zn > Ni > Cr > - Co > Cu > Pb > Cd; in a fish (Heteropnuestes fossilis) Fe > Zn > Mn > Pb > Ni > Co > Cu > Cd > Cr, and in a plant (Eicchornia crassipes) Fe > Mn > Zn > Ni > Cu > Cr > Pb > Co > Cd.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号