The challenge of restoring vegetation on tidal,hypersaline substrates

Hypersaline tidal wetland restoration sites are challenging to vegetate, and the specific factors responsible for transplant mortality are difficult to pinpoint. Two southern California sites (Tidal Linkage and Friendship Marsh), planted as large field experiments, had differential transplant survival (93% for a 1997 planting at the first site, and 10% for a 2000 planting in the second site). Multiple stresses (high salinity, sediment deposition, algal smothering and animal activity) are implicated as the cause of mortality in the experimental plantings. Greater hypersalinity and sedimentation appeared to be a function of site context, with greater sediment inflows and salt concentration over the larger (8-ha) marsh plain at the Friendship Marsh. Species differed in establishment rates among sites and years; the regional dominant, Salicornia virginica, performed best as a transplant and in volunteer seedling recruitment in the Tidal Linkage; hence, it was not planted at the larger site, where it has recruited without assistance. Frankenia salina had high survival in the 2000–2001 plantings; this species is also widespread in the region. Our attempts to restore salt marsh plain vegetation in Southern California led to greater appreciation of the importance of environmental stress and stochastic events and their potential for interaction. Hypersalinity and other factors are extremely difficult to ameliorate, especially in large restoration sites.     

Effects of Sewage Sludge on the Growth of Potted Salt Marsh Plants Exposed to Natural Tidal Inundation

Abstract A growth experiment with native plants in pots exposed to natural environmental conditions evaluates the use of sewage sludge as a soil amendment in restoration of a southern California salt marsh. Sludge containing desirable organic matter but also undesirable heavy metal contaminants was mixed with a readily available matrix soil to reduce metal concentrations to levels below legal limits for land applications of sludge. Soil nutrient analysis revealed expected increases in total nitrogen and total phosphorus content with increasing sludge concentration. Soil metals analysis, however, revealed decreases in metal content with increased sludge concentration, a trend evidently caused by higher than expected metal content in the matrix soil. Five artificial soil mixtures ranging from 0 to 70% sludge were accompanied by natural wetland soil controls. Pots containing these soils were placed into a natural salt marsh. The pots were then planted with two native salt marsh plant species, Salicornia virginica and Frankenia grandifolia. Aboveground biomass was harvested after 12 months. Plant growth displayed no obvious change with increasing sludge concentration. Over the concentration ranges used, increased nutrient content did not stimulate plant growth and increased metal content did not inhibit plant growth. Plants grew better in natural wetland soil than in artificial soil mixtures, a trend probably caused by the substantially finer texture and higher organic content of natural soil. All sludge treatments differed more from the natural soil than from each other, implying that within the ranges examined, soil texture and organic content exerted more influence on plant growth than did metal or nutrient concentration. These results suggest that incorporating this sewage sludge in the soil of the restored salt marsh will neither benefit nor harm the plants that will live there and that greatest plant growth will be achieved by mixing the sludge with a fine‐grained matrix soil.     

Restoration principles emerging from one of the world's largest tidal marsh restoration projects

One of the world's largest tidal wetland restorationprojects was conceived to offset the loss of nekton toonce-through cooling at a power plant on Delaware Bay,USA. An aggregated food chain model was employed toestimate the area of tidal salt marsh required toreplace these losses. The 5040 ha was comprised of twodegraded marsh types – Phragmites- dominatedmarshes and diked salt hay farms – at elevenlocations in oligo-mesohaline and polyhaline reachesof the estuary. At a series of summits convened withnoted experts in the field, it was decided to apply anecological engineering approach (i.e., self design,and minimal intrusion) in a landscape ecologyframework to the restoration designs while at the sametime monitoring long-term success of the project inthe context of a bound of expectation. The latterencompassed a range of reference marsh planforms andacceptable end-points established interactively withtwo advisory committees, numerous resource agencies,the permitting agency and multiple-stakeholder groups.In addition to the technical recommendations providedby the project's advisors, public health and safety,property protection and public access to the restoredsites were a constant part of the dialogue between theutility, its consulting scientists and theresource/permitting agencies. Adaptive management wasused to maintain the restoration trajectories, ensurethat success criteria were met in a timely fashion,and to protect the public against potential effects ofsalt intrusion into wells and septic systems, andagainst upland flooding. Herbicide spray, followed byprescribed burns and altered microtopography were usedat Phragmites-dominated sites, and excavation ofhigher order channels and dike breaching were themethods used to initiate the restorations at the dikedsalt hay farms. Monitoring consisted of evaluating therate of re-vegetation and redevelopment of naturaldrainage networks, nekton response to therestorations, and focused research on nutrient flux,nekton movements, condition factors, trophic linkages,and other specific topics. Because of its size anduniqueness, the Estuary Enhancement Program as thisproject is known, has become an important case studyfor scientists engaged in restoration ecology and theapplication of ecological engineering principles. Thehistory of this project, and ultimately theRestoration Principles that emerged from it, are thesubjects of this paper. By documenting the pathways tosuccess, it is hoped that other restoration ecologistsand practitioners will benefit from the experiences wehave gained.     

Coastal vegetation on the Western, Southern, and Eastern coasts of South Korea

We used the Braun-Blanquet method to study the vegetation of coastal wetlands in South Korea. Three habitat types were found, i.e., salt marshes, salt swamps, and sand dunes. These plant communities were classified as: 1) two groups (five associations each) in the salt marshes that comprised either annual herbaceous halophytes (ClassThero-Salicornietea), or biennial/perennial herbaceous species (ClassAsteretea tripolii); 2) one group in the salt swamps consisting of five hydrophilous halo-tolerant associations (ClassPhragmitetea); and 3) three groups in the sand dunes, including one association of annual herbaceous halophytes (ClassSalsoletea komarovii), seven associations of herbaceous perennial halophytes (ClassGlehnietea littoralis), and one association of shrub perennial halophytes (ClassVrticetea rotundifoliae). These three habitat types accounted for the majority of the six main classifications of coastal vegetation distributed in South Korea.     

The influence of tidal channels on the distribution of salt marsh plant species in Petaluma Marsh,CA, USA

Tidal channels influence the distribution and composition of salt marsh vegetation in a San Francisco Bay salt marsh. Two channel networks in the Petaluma Marsh, Sonoma County, CA, were mapped and characterized using global positioning and geographic information systems. Plant species abundance was sampled on transects placed perpendicular to and extending away from the channel banks. The vegetation showed significant increases in species richness along channel banks and larger areas of effect which increased approximately linearly with channel size. Composition of species assemblages varies with distance from the channel bank and channel size. These results demonstrate that salt marsh plant assemblages, composed of both major and minor species, are distributed with respect to the channel network in Petaluma Marsh.     

苏干湖湿地植被覆盖度时空变化格局

植被覆盖度是反映群落外貌特征和影响植被生态系统稳定性的重要因子,其时空异质性演化规律研究有助于认识湿地群落的结构功能及其环境响应机制。采用湿地群落学调查和遥感技术相结合的方法,分析了苏干湖内陆盐沼湿地近30年植被覆盖度的时空变化及其影响因素。结果表明:像元二分模型在内陆盐沼湿地植被覆盖度研究方面具有较高的模拟精度;苏干湖湿地的植被覆盖度在1987—2017年间总体呈上升趋势,年际增幅为0.162%/5a,与气温和降水呈正相关关系;在空间上植被覆盖度与地下水位埋深呈正相关,与土壤全盐量呈负相关,但不同等级植被覆盖度与地下水位埋深、土壤全盐量间的相关性各有差异。苏干湖湿地植被覆盖度受地下水位埋深、土壤全盐量空间异质性的影响,呈现出斑块状镶嵌分布。     

中国海岸带围垦遥感分析

海岸带围垦是沿海区域缓解人口增长与城镇扩张所带来土地压力的重要途径和方式。建国以来,中国大陆沿海围垦大量滨海湿地以满足社会经济发展所导致的土地需求,对滨海湿地的资源、生态和环境造成影响和胁迫。为掌握近35年来中国大陆沿海地区的围填海状况,以5a为间隔,选取1985—2010年间Landsat系列卫星影像数据,基于遥感与GIS技术,解译6个年份的围垦岸线,计算分析围垦面积,研究并提出围垦强度系数。结果表明,1985—2010年,中国大陆沿海共围垦土地755183 hm~2,年均围垦30207 hm~2,围垦强度达到1.7 hm~2a~(-1)km~(-1),围垦总量趋势表现先减少后增加。环渤海经济圈与长三角经济圈围垦强度最大,其围垦总量占到全国总体的85.7%。围垦的时空分布及其利用形式受沿海区域自然地理条件和地区经济发展水平的制约和影响。     

植被类型对盐沼湿地空气生境节肢动物功能群的影响

2007年4-11月,在长江口崇明东滩盐沼湿地的芦苇带、海三棱藨草带和互花米草带设置固定样地,每月小潮期对空气生境的节肢动物进行了扫网取样调查。在此基础上,分析研究了盐沼湿地空气生境节肢动物功能群特征以及植被类型的影响,特别是对互花米草的生态效应进行了进一步讨论。调查期间共获得节肢动物标本3778头,分属2纲11目37科49种。根据不同种类的营养特征将其划分为植食性、捕食寄生性和腐食性三大功能群。其中,植食性功能群的种类、数量最为丰富,涉及1纲6目19科25种,物种数占总数的51.0%,个体数占总数的86.2%;捕食寄生性功能群次之,涉及2纲7目15科21种,物种数占总数的42.9%,个体数占总数的7.8%;腐食性功能群种类、数量最少,涉及1纲1目3科3种,物种数占总数的6.1%,个体数占总数的6.0%。不同植被带捕食寄生性功能群与植食性功能群均具有一定的\"天敌跟随\"特征,但主要表现在物种数上,而在个体数上的对应关系并不明显。不同植被带功能群的组成、多样性及月际变化特征存在一定差异,但是植被类型对功能群的影响并不显著。与已有研究结果不同,研究中外来种互花米草对空气生境的节肢动物并未表现出显著的负面影响,相应节肢动物功能群的物种数、个体数、多样性、月际变化等特征与其他植被带并没有显著差异。就植食性功能群而言,尽管互花米草带植食性功能群的个体数明显低于其它植被带,但是物种数并没有减少,相应的作用机理还有待进一步研究。     

Estuarine and Tidal Wetland Restoration in the United Kingdom: Policy Versus Practice

Restoration of reclaimed marshes in the United Kingdom, referred to as managed realignment, is both a scientific and a political issue. A cross‐party House of Commons report to Government stressed that provision of long‐term sustainable coastal defenses must start with the premise that “coasts need space” and that government must work to increase public awareness, scientific knowledge, and political will to facilitate such a retreat from the almost sacrosanct existing shoreline. Government, in turn, has agreed with the basis of the report but is aware of conflicting interests, not least the European legislation, which has designated large areas of reclaimed marshes as Special Areas of Conservation that cannot legally be restored to their former tidal processes. Against this background, it is essential that scientific research provides convincing arguments for the necessity for managed realignment, the location, extent, and type of marshlands that need to be restored to provide sustainable flood defenses, maintain and enhance conservation status, and ensure a healthy functioning estuarine system. We examine the political and scientific issues involved, discuss model predictions and field experiments into realignment techniques, and outline the preliminary results of such experiments showing the evolution of restored intertidal wetlands in the United Kingdom.     

滨海湿地植被地上生物量遥感反演

盐沼植被生物量是滨海湿地生态系统碳循环研究的重要参数,是湿地生态系统健康评价、资源可持续利用的关键指标,开展盐沼植被地上生物量监测方法研究具有重要意义。目前,遥感技术在湿地生物量监测领域已经得到广泛应用,但反演方法仍以统计模型为主,模型构建需要实测数据支撑,时空拓展性不强。选择江苏盐城丹顶鹤保护区为研究区,基于冠层辐射(PROSAIL)传输模型,通过局部和全局敏感性分析,对模型参数本地化,构建了互花米草地上生物量半经验反演模型,应用于Landsat 8 OLI遥感影像,获得了互花米草地上生物量的时空分布。研究结果表明,利用PROSAIL模型模拟互花米草冠层反射率,叶面积指数(LAI)、叶片干物质含量(Cm)、叶倾角分布参数(LIDF)、等效水厚度(Cw)、叶绿素含量(Cab)、叶片结构参数(N)为高敏感性参数,类胡萝卜素含量(Car)、土壤参数(P_soil)为低敏感性参数;利用不同时刻的遥感影像反演了地上生物量,遥感反演结果与实测数据对比,拟合度R²为0.83,均方根误差(RMSE)为0.43kg/m²,平均相对误差(MRE)为15.7%,精度较高,模型具有较好的时空普适性。研究发展了盐沼植被地上生物量遥感反演方法,解决了以往过于依赖现场实测数据构建反演模型的局限性,该方法可以为研究滨海湿地生态系统碳循环以及准确估算其碳汇潜力提供技术支持。     

Diazotrophic endophytes: progress and prospects for nitrogen fixation in monocots

Spatial variability of plant growth has been a major problem for plant physiologists, agronomists, agro-foresters and soil scientists comparing or modelling treatment effects on acid sandy soils in the Sahel. While aerial photographs from aeroplanes or satellite images may provide valuable information for the surveying of large areas, their use for individual small experiments or farmers' fields has been limited due to high costs, restricted availability, and unsatisfactory resolution. As a simple alternative, a commercially available Zeppelin-type balloon, dragged on a rope by a camel, was fitted with an standard 35 mm camera and a remote control system. Flight altitude varied from 20 m to 500 m above ground. A ground-based camera mounted vertically on a tripod was used to center the Zeppelin over the target area. The high-resolution true colour negatives and colour infrared slides obtained by this device were used to unravel the history of farmers' management strategies for maintaining soil productivity, to monitor treatment effects and crop growth variability in an on-station experiment, and to visualize light absorption by photosynthesis in crops and trees. Such non-destructively collected data may serve as quick but reliable references for ground measurements in a wide range of experiments with loosely-spaced crops, bushes, and trees. ei]B E Clothier