海三棱藨草及互花米草对模拟盐胁迫的响应及其耐盐阈值

盐度作为滨海湿地的关键环境因子之一,影响盐沼植物的存活、生长及分布。未来海平面上升引起的盐水入侵,将导致滨海湿地的盐沼植物面临高盐胁迫的挑战,进而影响滨海湿地生态系统的结构和功能。本研究选择长江口中低潮滩的主要先锋植物海三棱藨草(Scirpus mariqueter)和互花米草(Spartina alterniflora)为对象,通过人工控制实验,比较不同盐度处理下两种盐沼植物存活、营养生长及繁殖的响应,并确定两种盐沼植物存活的耐盐阈值,从而比较未来盐水入侵背景下,本地物种海三棱藨草及外来物种互花米草对盐胁迫的响应和适应性。结果表明:(1)海三棱藨草和互花米草的存活率随着盐度的增加均呈下降趋势,相同盐度处理下互花米草的存活率显著高于海三棱藨草的存活率(P0.05);(2)盐胁迫明显影响了海三棱藨草和互花米草的生长,随着盐度的增加,海三棱藨草株高、地上生物量及地下生物量均呈逐渐下降的趋势,而互花米草株高、地上生物量及地下生物量呈先增加后下降的趋势,均在盐度为10‰时最高;(3)海三棱藨草和互花米草的分蘖数及结穗率均随着盐度增加呈下降趋势,盐胁迫在一定程度上抑制了两种植物的繁殖能力;(4)互花米草存活的耐盐阈值为43‰,高于海三棱藨草存活的耐盐阈值(21‰);(5)外来物种互花米草比本地物种海三棱藨草具有更强的耐盐性,未来海平面上升引起的盐水入侵将对本地物种海三棱藨草产生更加严重的影响。     

崇明东滩湿地不同盐沼植物群落土壤碳储量分布

海岸带盐沼植被的高生产力对湿地土壤碳库的形成具有重要意义.本文研究了长江口崇明东滩湿地3种主要盐沼植物(芦苇、互花米草和海三棱藨草)群落生物量差异、土壤碳储量时空动态和垂向分布特征.结果表明： 湿地盐沼植被总生物量表现为互花米草群落(5750.7 g·m^-2)>芦苇群落(4655.1 g·m^-2)>海三棱藨草群落(812.7 g·m^-2),且地上生物量在夏、秋季最高,地下生物量在冬季最高.湿地土壤碳储量(0～50 cm)在春季最低,随后逐渐增加,至冬季达到最大值.土壤碳储量年增量从高潮滩向低潮滩递减,表现为芦苇群落(711.8 g·m^-2)>互花米草群落(646.2 g·m^-2)>海三棱藨草群落(185.3 g·m^-2)>光滩(65.6 g·m^-2).光滩土壤碳储量在25～30 cm处最高,海三棱藨草、互花米草和芦苇群落土壤碳储量分别在10～15、30～35和30～40 cm处达到最大值,且不同群落土壤碳储量与植被地下生物量具有显著的线性关系.     

崇明东滩南部盐沼植被空间分布及影响因素分析

崇明东滩南部滩面高程、土壤盐度在空间上呈明显的梯度变化规律。高程整体西高东低、北高南低, 盐度东北高、西南低, 两者共同限制着盐沼植物在空间上的分布。该文围绕崇明东滩南部主要植被类群及其空间分布, 探讨了土壤盐度、潮滩高程两大环境因子与植物种群分布的对应关系。基于2013年夏、秋季植被空间网格采样和空间插值, 分析了东滩南部植物的空间分布现状, 发现不同植物类群在高程和土壤盐度上存在极显著的差异(p < 0.01)。高程差异: 莎草科类群主要分布于高程区间2.93-4.07 m的低潮滩, 禾本科主要集中分布在高程3.13-4.31 m的中、高潮滩; 盐度差异: 海三棱藨草(Scirpus mariqueter)和互花米草(Spartina alterniflora)优势种群植被覆盖区表层30 cm的平均土壤盐度为(3.2 ± 0.6) g·kg^-1, 显著高于其他类群植物分布区的平均土壤盐度(2.0 ± 0.3) g·kg^-1 (p < 0.01)。崇明东滩湿地生态系统的关键种兼先锋种——海三棱藨草, 分布高程介于2.53-3.97 m, 而互花米草能适应海三棱藨草80%的高程区间, 两者在高程上存在竞争关系。统计数据显示, 研究区域中近90%的海三棱藨草分布在研究区东北部, 土壤盐度范围为1.6-4.5 g·kg^-1, 海三棱藨草、互花米草能较好地适应该空间内的盐度胁迫, 两种植物在此交替出现。但是在高程和土壤盐度的综合作用下, 互花米草的生长状况更好, 因此该区的海三棱藨草很可能会被互花米草逐步取代。对各类群植被分布和优势面积的研究发现, 海三棱藨草总分布面积为294 hm², 优势群落面积120 hm², 海三棱藨草仅占莎草科植物总优势面积的15.7%, 占研究区总面积的6.9%, 在6种主要植物(芦苇(Phragmites australis)、白茅(Imperata cylindrica)、互花米草、糙叶薹草(Carex scabrifolia)、藨草(Scirpus triqueter)、海三棱藨草)中比重最小, 这给保护区内海三棱藨草种群的恢复和保护带来极大的挑战。     

崇明东滩湿地营养盐与重金属的分布与累积

测定了崇明东滩湿地盐沼植物和沉积物中TN、TP、重金属Cu、Zn、Pb和Cd的含量,阐明了它们在湿地中的分布与累积特征,评估3种盐沼植物对营养盐和重金属的富集能力,并讨论了互花米草入侵对长江口湿地生态系统可能造成的影响.海三棱镳草地上部分的TN、Cu、Pb和Cd的含量均显著高于芦苇和互花米草（p＜0.01）,而地上部分TP和Zn却表现为：海三棱镳草和互花米草无显著性差异（p＞0.05）,但均显著高于芦苇（p＜0.01）.东滩湿地沉积物中TN和重金属的分布与累积特征为：芦苇带＞互花米草带＞海三棱镳草带＞光滩,即随着高程的增加,沉积物中TN和重金属的含量逐步上升;但沉积物中TP含量变化不大,基本维持在0.06%左右.基于盐沼植物地上部分的生物量,估算了3种盐沼植物地上部分的营养盐和重金属库,结果表明：互花米草地上部分的养分库和重金属库均大于芦苇和海三棱镳草,表明收获互花米草对环境的净化效果最佳,特别对磷的去除效率是最高的.     

盐度及种间相互作用对海三棱藨草、互花米草萌发及生长的影响

盐度和种间作用是影响湿地植物群落构建的关键因子。然而,已有研究主要集中于植物成体阶段,我们对生活史早期更新阶段的种间相互作用了解十分有限。崇明东滩国家级自然保护区是位于长江口的重要湿地,外来入侵植物互花米草对优势土著物种海三棱藨草的竞争排斥对当地生态系统造成了严重的负面影响。通过受控实验探讨了盐度及种间作用对海三棱藨草和互花米草种子萌发及生长的影响,以深入了解更新过程在盐沼湿地植物群落构建中的作用。结果表明,在培养皿中盐度对海三棱藨草的萌发有显著抑制作用,互花米草的萌发率受盐度影响不显著但萌发进程被延迟。混种处理对两者的萌发存在一定促进效应,且其作用强度受到盐度的调控。海三棱藨草与互花米草种子在萌发阶段的相互促进并非是通过化感作用实现的,可能是由于萌发过程对盐分的吸收减弱了盐胁迫的影响。盆栽条件下,两物种混种时的萌发及生长表现（高度、地上生物量）较单种时有所下降,但差异不显著。种间竞争受环境胁迫程度及生活史阶段的影响,竞争作用在胁迫较弱的淡水环境及生活史后期更强。盐沼湿地植物群落在形成早期受到盐度等环境因子的影响较大,不同植物对盐胁迫的响应是影响种群建成的主导因素,后期种间竞争的重要性不断增加,最终决定了植物群落的整体格局。     

崇明东滩湿地自然植被演替过程中储碳及固碳功能变化

采用实地调查与实验室测定相结合的方法,研究了崇明东滩湿地植被演替过程中储碳、固碳功能的变化.结果表明：不同演替阶段的湿地植被的现存碳储量及其分配格局特征存在较大差异.先锋物种海三棱藨草的现存碳储量仅占芦苇现存碳储量的13%;地下根茎为芦苇现存碳储量的主要场所,而地上部分是海三棱藨草碳储量的主要场所.处于潮滩湿地演替中后期的芦苇群落比处在生态演替早期的海三棱藨草群落具有更强的固碳能力,芦苇群落和海三棱藨草群落的年固碳能力分别为(1.63±0.39) kg·m^-2和(0.63±0.28) kg·m^-2,说明随着海三棱藨草群落向芦苇群落演替,其固碳能力不断增强.     

九段沙湿地植被群落演替与格局变化趋势

长江口新生湿地九段沙由上沙、中沙和下沙三部分组成。2004年对湿地植被群落的演替与格局变化进行了研究。结果表明,九段沙湿地植被群落由芦苇(Phragmites austra-lis)、互花米草(Spartina alterniflora)、海三棱藨草(Scirpus mariqueter)和藨草(S.triqueter)构成。芦苇和互花米草生长于潮滩高程,海三棱藨草和藨草生长于低潮位。1998—2004年,上沙植被覆盖面积年平均约增长17%,中沙22%,下沙38%~39%,植被群落处于快速增长演替状态,这可能与沙洲发育速度有关。由于在中沙、下沙人为种植过外来物种互花米草,其增长速度最快,覆盖面积占九段沙植被总面积的比例从1998年不足1%上升到2004年的22%,地上部分总生物量的年平均增长率为79.79%,互花米草对藨草-海三棱藨草的竞争压力较大。鉴于互花米草对九段沙的影响尚无定论,本文提出了初步的植被管理措施。     

互花米草与海三棱藨草的生长特征和相对竞争能力

外来物种互花米草(Spartinaalterniflora)已对我国特有种海三棱藨草 (Scirpusmariqueter)发生了竞争取代。作者通过在长江口崇明东滩湿地取样和盆栽竞争实验,比较了二者的主要生长特征和种间相对竞争能力。结果表明:无论是先锋种群还是成熟种群,互花米草的高度、盖度、地上生物量、地下生物量和平均每花序种子数都显著大于海三棱藨草;海三棱藨草的密度和单位面积结实枝条数显著大于互花米草。两种植物成熟种群的单位面积种子产量和种子的萌发率没有显著差异。种内竞争和种间竞争显著降低了两种植物的平均每株产生的无性小株数、结实株数、地上生物量和地下球茎数(海三棱藨草产生球茎),互花米草的种间竞争能力 (相对邻里效应指数 )显著大于海三棱藨草。互花米草在生长上的优势可能导致其在种间竞争上的优势,从而使互花米草能够在海三棱藨草群落中成功入侵。     

崇明东滩盐沼植被成带性对土壤因子的响应

对东滩湿地不同植被带与土壤环境因子的关系进行了探讨,分析植被成带性分布与土壤含水量、土壤盐度、土壤温度之间的关系,研究表明:(1)光滩(TF)、海三棱藨草(Sm)、互花米草带(Sa)土壤含水量差异显著(P0.05),随着土壤含水量的显著变化,海三棱藨草和互花米草种群分布呈现明显带状分布,土壤含水量对植被带的分布起到一定的平衡作用,在土壤经常性淹水下,互花米草种群的海向性拓殖受到一定抑制。(2)光滩带、海三棱藨草带、互花米草带之间的土壤盐分(NaCl)差异极显著(P0.001),从海向陆依次为:NaCl光滩带NaCl海三棱带NaCl互花米草带,NaCl含量增加土壤含水量相对减小,土壤盐度和含水量的差异极大影响了海三棱藨草和互花米草植被带的分布模式,从而进一步制约了其演替进程。不同植被带间温度差异显著,总体趋势为互花米草带最高而潮滩带最低,并且互花米草带土壤温度显著高于其它各带,小尺度空间上植被对环境因子的响应明显。(3)相对于7月份而言,5月份各带内土壤含水量显著较高,但植被带间没有显著性变化。光滩最高,依次为海三棱带和互花米草带。然而,7月份土壤盐度和温度显著大于5月份,互花米草带最高,依次为海三棱和光滩带。     

基于遥感的九段沙湿地植被群落动态变化分析

九段沙是长江口重要的新生湿地.作为主要地物类型之一的植被群落,是反映潮滩湿地生态环境变化重要而又敏感的指标因子.本文通过1987～2008年六景Landsat卫星遥感数据对九段沙植被群落进行了分类提取,并利用ArcGIS软件分析了长江口九段沙植被群落20年来的时空动态变化.结果显示1987～1997年间,九段沙湿地植被以先锋植被海三棱藨草为主,植被面积随潮滩不断淤涨而增长;1997年人工促淤种植了芦苇和互花米草,至2008年,芦苇、互花米草和海三棱藨草三种植被群落所占植被总面积百分比分别为31.47%、39.35%和29.17%,其中外来物种互花米草优势明显,当地植被海三棱藨草所占面积比例显著下降.     

Crustacean metamorphosis: an omics perspective

We quantified the independent impacts of flooding salinity, flooding depth, and flooding frequency on the native species, Phragmites australis and Scirpus mariqueter, and on the invasive species Spartina alterniflora in the Yangtze River Estuary, China. Total biomass of all three species decreased significantly with increasing salinity, but S. alterniflora was less severely affected than P. australis and S. mariqueter. Elevated flooding depth significantly decreased their live aboveground biomass of P. australis and S. mariqueter, while S. alterniflora still had high live aboveground biomass and total biomass even at the highest flooding depth. These findings indicated that S. alterniflora was more tolerant to experimental conditions than the two native species, and an unavoidable suggestion is the expansion of this non-native species in relation to the native counterparts in future scenarios of increased sea-level and saltwater intrusion. Even so, environmental stresses might lead to significant decreases in total biomass and live aboveground biomass of all three species, which would potentially weaken their ability to trap sediments and accumulate organic matter. However, the relatively high belowground-to-aboveground biomass ratio indicated phenotypic plasticity in response to stressful environmental conditions, which suggest that marsh species can adapt to sea-level rise and maintain marsh elevation.     

滨海盐渍土壤中不同类型盐生植物富集镉的效应

为了利用被镉污染的滨海盐渍土壤,通过实验对比分析3种不同类型盐生植物对盐渍土中镉的富集效应,以期初步探明不同类型盐生植物在镉污染盐渍土壤修复中的效果。选择的3种盐生植物类型是:聚盐盐生植物,泌盐盐生植物和避盐盐生植物。通过温室盆栽实验,将植物在不同镉含量的盐渍土壤中种植培养60 d,测定和分析不同类型盐生植物对镉的生物浓缩因子、转移系数以及植株内地上部分和根部生物量和镉含量的变化。结果表明,不同镉含量的土壤对碱蓬和芦苇的生长影响较小,对二色补血草的生长影响较大。不同镉含量的土壤中,芦苇地上部分镉的生物浓缩因子变化差异不显著,并且其地上部分吸收镉的百分率较高。碱蓬和芦苇的转移系数大于二色补血草的转移系数,并且碱蓬的转移系数在不同镉含量的土壤中变化不显著;二色补血草的转移系数随着土壤中镉含量的增加而显著增大。3种盐生植物中,碱蓬最具修复镉污染盐渍土壤的潜力,这可能和它是聚盐盐生植物的生理类型有关。芦苇整个植株的地上部分富集镉的总量在3种植物中是最高的,因此,芦苇在镉含量较低时也可以做为镉污染盐渍土壤的修复材料。     

北部湾大风江口互花米草湿地有机碳储量的分布特征

互花米草被引入我国滨海地区后,经过多年的生长与演替,改变了潮间带原有生态系统的碳储量,而影响机制仍有待深入研究。为进一步探讨互花米草入侵后潮滩有机碳储量演变特征,该文以广西北部湾大风江口入侵约6 a的互花米草湿地为研究对象,分析了2018年8月、11月及2019年1月、3月采集的样品中有机碳及相关理化指标。结果表示:(1)互花米草植物年均地上碳储量为9.68 t·hm~(-2),高于地下根系的5.56 t·hm~(-2);(2)互花米草入侵湿地土壤碳储量显著高于互花米草植物本身,且不同季节中春季土壤碳储量显著高于其他季节;(3)土壤的C/N比值为3.53～9.67,表明互花米草入侵群落有机碳受海源的潮汐输入影响较大;(4)互花米草生态系统总碳储量与土壤碳储量之间呈极显著正相关关系,且季节性变化规律一致;(5)随着入侵时间的延长,互花米草生态系统中有机碳储量呈逐渐增加的趋势,表明互花米草入侵提高了光滩的有机碳储量,并能提高光滩的固碳能力。该文可为科学评价互花米草入侵对光滩碳储量的影响提供参考。     

Effect of oxygen availability and salinity on EARLY LIFE HISTORY STAGES OF SALT MARSH PLANTS. I. Different germination strategies of Spartina alterniflora and Phragmites australis (Poaceae)

Gradients in oxygen availability and salinity are among the most important environmental parameters influencing zonation in salt marsh communities. The combined effects of oxygen and salinity on the germination of two salt marsh grasses, Spartina alterniflora and Phragmites australis, were studied in growth chamber experiments. Germination of both species was initiated by emergence of the shoot and completed by root emergence. Percentage S. alterniflora germination was reduced at high salinity (40 g NaCl/L) and in decreased oxygen (5 and 2.5%). In 0% oxygen shoots emerged, but roots did not. P. australis germination was reduced at a lower salinity (25 g NaCl/L) than S. alterniflora, and inhibited at 40 g NaCl/L and in anoxia. However, a combination of hypoxia (10 and 5% O2) and moderate salinity (5 and 10 g NaCl/L) increased P. australis germination. When bare areas in the salt marsh are colonized, the different germination responses of these two species to combinations of oxygen and salt concentrations are important in establishing their initial zonation. In high salinity wetlands S. alterniflora populates the lower marsh and P. australis occupies the high marsh at the upland boundary.     

Effects of Spartina alterniflora Invasion on Soil Respiration in the Yangtze River Estuary,China

Many studies have found that plant invasion can enhance soil organic carbon (SOC) pools, by increasing net primary production (NPP) and/or decreased soil respiration. While most studies have focused on C input, little attention has been paid to plant invasion effects on soil respiration, especially in wetland ecosystems. Our study examined the effects of Spartina alterniflora invasion on soil respiration and C dynamics in the Yangtze River estuary. The estuary was originally occupied by two native plant species: Phragmites australis in the high tide zone and Scirpus mariqueter in the low tide zone. Mean soil respiration rates were 185.8 and 142.3 mg CO₂ m⁻² h⁻¹ in S. alterniflora and P. australis stands in the high tide zone, and 159.7 and 112.0 mg CO₂ m⁻² h⁻¹ in S. alterniflora and S. mariqueter stands in the low tide zone, respectively. Aboveground NPP (ANPP), SOC, and microbial biomass were also significantly higher in the S. alterniflora stands than in the two native plant stands. S. alterniflora invasion did not significantly change soil inorganic carbon or pH. Our results indicated that enhanced ANPP by S. alterniflora exceeded invasion-induced C loss through soil respiration. This suggests that S. alterniflora invasion into the Yangtze River estuary could strengthen the net C sink of wetlands in the context of global climate change.     

Local competitive effects of introduced Spartina alterniflora on Scirpus mariqueter at Dongtan of Chongming Island, the Yangtze River estuary and their potential ecological consequences

Dongtan of Chongming Island, Shanghai, China is a wetland of international importance, in which dominant vegetation is Scirpus mariqueter community that supports a great diversity of bird species. Spartina alterniflora, native to the eastern and gulf coasts of the USA, was intentionally introduced to the tidelands of Dongtan in May 2001. Field work were conducted at Dongtan from March 2002 to May 2003 to determine how introduced S. alterniflora affects S. mariqueter population dynamics. The results obtained here show that S. alterniflorahad strong competitive effects on S. mariqueter, and that the introduction of S. alterniflora to S. mariqueter community resulted in a significant decreases of S. mariqueter's abundance, coverage, seed and fresh corm output after two growing seasons. A concomitant consequence might be the decline in bird diversity. It is suggested that further introduction of S. alterniflora should be avoided to conserve the wetlands and their associated birds. A plan for controlling further spread of existing S. alterniflora populations in the Yangtze River estuary is urgently needed.     

Impacts of introduced Spartina alterniflora along an elevation gradient at the Jiuduansha Shoals in the Yangtze Estuary,suburban Shanghai,China

Although much research has focused upon the negative impacts of invasive Spartina alterniflora upon salt marshes dominated by other Spartina spp., little is known about its impacts upon native Scirpus mariqueter marshes. In 1997, S. alterniflora was introduced to the Jiuduansha Shoals, Yangtze Estuary, China, to accelerate the formation of marsh habitat via accretionary processes, with the larger goal of drawing waterfowl away from wetlands near the Pudong International Airport, Shanghai, China. In 2000, a nature reserve was established on the Jiuduansha Shoals, making the impact upon the native S. mariqueter community a high priority for research. Our objective was to quantify the impacts of introduced S. alterniflora and Phragmites australis to the native S. mariqueter-dominated community at this site in four elevation zones, as compared with a nearby natural shoal. We found that species diversity was greater in the lower elevations with the engineering, through elimination of the natural dominance of S. mariqueter. We also found that diversity was lessened in the higher elevations, due to rapid growth and exclusion by the planted S. alterniflora in conjunction with the native P. australis. Moreover, we found that the growth of the native S. mariqueter was stimulated when S. alterniflora was planted nearby. It is quite likely that the net effect of these ecological processes will be to accelerate further accretion, leading to an eventual replacement of the S. mariqueter-dominated community in the long-term. Future management approaches should focus upon harvesting, grazing, and perimeter-ditching the S. alterniflora to avoid this situation.     

Relationships between vegetation zonation and environmental factors in newly formed tidal marshes of the Yangtze River estuary

The Yangtze River delta is characterized by rapidly accreting sediments that form tidal flats that are quickly colonized by emergent vegetation including Scirpus mariqueter and the invasive species Spartina alterniflora. We measured soil surface elevation, water table depth, soil salinity, water content and compaction in the tidal flat, the Scirpus and Spartina zones and their borders to identify relationships between environmental factors and colonization by Scirpus and Spartina. With increasing elevation from tidal flat to Spartina, inundation frequency and duration, moisture and depth to water table decreased whereas soil salinity, temperature and compaction increased. High soil moisture and groundwater and low salinity were the characteristics of the tidal flat and its border with Scirpus. The Spartina zone and its border with Scirpus were characterized by greater salinity and elevation relative to the other zones. Our findings suggest that soil salinity controls patterns of plant zonation in the newly formed tidal salt marshes whereas elevation is of secondary importance. Our results suggest that patterns of vegetation zonation in tidal marshes of the Yangtze River delta are controlled by environmental factors, especially (low) salinity that favors colonization by Scirpus in the lower elevations of the marsh.     

Spartina alterniflora invasions in the Yangtze River estuary,China: An overview of current status and ecosystem effects

The Yangtze River estuary is an important ecoregion. However, Spartina alterniflora, native to North America, was introduced to the estuary in the 1990s through both natural dispersal and humans and now it is a dominant species in the estuarine ecosystems, with its invasions leading to multiple consequences to the estuary. S. alterniflora had great competitive effects on native species, including Scirpus mariqueter and Phragmites australis, and could potentially exclude the natives locally. The presence of S. alterniflora had little influence on the total density of soil nematodes and macrobenthonic invertebrates, but significantly altered the structure of trophic functional groups of nematode and macrobenthonic invertebrate communities. The conversion of mudflats to Spartina meadows had significant effects on birds of Charadriidae and Scolopacidae, which might be attributable to the reduction of food resources and the physical alterations of habitats for shorebirds. S. alterniflora invasions increased the primary productivity of the invaded ecosystems, and altered carbon and nitrogen cycling processes. Our studies focused mainly on the effects of S. alterniflora invasions on the structure of native ecosystems; thus further studies are clearly needed to investigate how ecosystem functioning is affected by the modification of the structure of estuarine ecosystems by S. alterniflora invasions.