崇明东滩围垦湿地芦苇光合作用对模拟升温的响应初探

采用开顶式气室法(Open top Chamber, OTC)模拟升温，分别于升温1 a和升温2 a后，测定崇明东滩围垦湿地代表植物--芦苇快速生长期叶片的光响应进程，分析最大净光合速率(Pmax)、暗呼吸速率〖WTBX〗(Rd)、表观量子效率(AQY)、光补偿点(LCP)、光饱和点(LSP)等光合参数对升温时间的累积响应。结果表明：与对照样地相比，升温1 a后Pmax、〖WTBX〗LSP显著增加，Rd、LCP显著降低，表现出正效应，而升温2 a后结果相反；升温条件下〖WTBX〗AQY的年际差异不显著；非线性拟合芦苇叶片光合 光响应(Pn PAR)曲线，结果显示其在升温第一年和第二年分别发生上调和下移现象；蒸腾速率(Tr)对升温表现增加趋势；气孔导度(Gs)、胞间CO2浓度(Ci)对升温的响应与光合有效辐射(PAR〖WTBZ〗)强度有关。这可能意味着长时间升温条件下芦苇叶片因非气孔因素限制发生光合适应现象     

长江口潮滩芦苇根表铁膜磁性特征及其环境意义

湿地植物根表铁膜对包括重金属在内的物质迁移转化具有重要作用,其氧化铁组成研究备受重视,但利用环境磁学方法进行表征的研究还未见报道.本文对长江口潮滩植物芦苇根系及周边沉积物进行了磁学分析,并结合沉积物粒度、漫反射光谱等测试,对芦苇根表铁膜的磁性矿物组成进行了系统研究.结果表明,芦苇根表铁膜磁性矿物主要包括磁铁矿和赤铁矿.由于沉积物不同深度氧化还原环境的不同,铁膜磁性矿物组成存在垂向差异.研究柱样24 cm深度以上,由于相对氧化的环境,铁膜磁性矿物除磁铁矿外,还有较多的赤铁矿贡献;24 cm深度以下,因根系处于相对还原的环境,磁性矿物以磁铁矿为主.与沉积物相比,24 cm以上深度铁膜中亚铁磁性矿物含量较低,24 cm深度以下则相反,反映铁膜和沉积物磁性矿物来源不同.本项研究表明,磁性测量方法有助于认识湿地植物根表铁膜的矿物组成,对湿地生物地球化学过程研究具有重要价值.     

Synchrotron micro-scale measurement of metal distributions in Phragmites australis and Typha latifolia root tissue from an urban brownfield site

Liberty State Park in New Jersey,USA,is a "brownfield" site containing various levels of contaminants.To investigate metal uptake and distributions in plants on the brownfield site,Phragmites australis and Typha latifolia were collected in Liberty State Park during the growing season(May–September)in 2011 at two sites with the high and low metal loads,respectively.The objective of this study was to understand the metal(Fe,Mn,Cu,Pb and Zn)concentration and spatial distributions in P.australis and T.latifolia root systems with micro-meter scale resolution using synchrotron X-ray microfluorescence(μXRF)and synchrotron X-ray computed microtomography(μCMT)techniques.The root structure measurement by synchrotron μCMT showed that high X-ray attenuation substance appeared in the epidermis.Synchrotron μXRF measurement showed that metal concentrations and distributions in the root cross-section between epidermis and vascular tissue were statistically different.Significant correlations were found between metals(Cu,Mn,Pb and Zn)and Fe in the epidermis,implying that metals were scavenged by Fe oxides.The results from this study suggest that the expression of metal transport and accumulation within the root systems may be element specific.The information derived from this study can improve our current knowledge of the wetland plant ecological function in brownfield remediation.     

芦苇化感物质对藻类细胞膜选择透性的影响

以藻类渗出的K⁺、Mg²⁺、Ca²⁺浓度为表征,以ICP-MS检测为手段,研究了芦苇抑藻化感物质2-甲基乙酰乙酸乙酯(eathyl-2-methyl acetoacetate, EMA)对铜绿微囊藻、蛋白核小球藻和普通小球藻细胞膜选择透性的影响. 结果表明, 在实验条件下, 铜绿微囊藻和蛋白核小球藻细胞经煮沸完全破坏细胞膜时K⁺渗出量为1 .45、1 .59 μg·(10⁹ cell)^-1, 当EMA浓度为2 mg·L^-1时, 铜绿微囊藻和蛋白核小球藻的K⁺渗出量为1 .38、1 .40 μg·(10⁹ cell)^-1,当EMA浓度为4 mg·L^-1时, 铜绿微囊藻和蛋白核小球藻的K⁺渗出量为1 .44、1 .58 μg·(10⁹ cell)^-1,离子渗出量达到完全破坏细胞膜最大渗出量的95%以上. EMA浓度为4 mg·L^-1时,普通小球藻的细胞内K⁺渗出量为0 .64 μg·(10⁹ cell)^-1, 仅为完全破坏细胞膜后K⁺渗出量的31 .5%. EMA对Mg²⁺、Ca²⁺的渗出量的影响规律与K⁺相同. EMA破坏了铜绿微囊藻和蛋白核小球藻的细胞膜,但对普通小球藻的细胞膜透性没有显著影响.这是EMA选择性抑藻的机理之一.     

Mapping Locust Habitats in the Amudarya River Delta,Uzbekistan with Multi-Temporal MODIS Imagery

Reed beds of Phragmites australis in the River Amudarya delta near the Aral Sea constitute permanent breeding areas of the Asian Migratory locust, Locusta migratoria migratoria. Every year, thousands of hectares are treated with broad-spectrum insecticides to prevent locust swarms from damaging crops in adjacent areas. To devise efficient locust monitoring and management plans, accurate and updated information about the spatial distribution of reeds is necessary. Given the vast geographic extent of the delta, traditional, ground survey methods are inadequate. Remotely sensed data collected by the MODIS sensor aboard the TERRA satellite provide a useful tool to characterize the spatial distribution of reeds. Multi-temporal MODIS data, collected at different times of the growing season, were used to generate spectral-temporal signatures for reeds and other land cover classes. These spectral-temporal signatures were matched with reed phenology. MODIS information was digitally classified to generate a land cover map with an overall accuracy of 74%. MODIS data captured 87% of the ground-verified reed locations. Estimates derived from MODIS data indicate that 18% of the study area was covered by reeds. However, high commission error resulted from misclassification of reeds mixed with shrubs class and shrubs class as reeds. This could have resulted in overprediction of the area covered by reeds. Additional research is needed to minimize the overlap between reeds and other vegetation classes (shrubs, and reed and shrub mix). Nevertheless, despite its relatively low spatial resolution (250 m), multi-temporal MODIS data were able to adequately capture the distribution of reeds. Instead of blanketing the fragile wetland ecosystem of the Amudarya delta with chemical anti-locust treatments, plant protection specialists can use this information to devise ecologically sound pest management plans aimed at reducing the adverse environmental impact in the zone of the Aral Sea ecological catastrophe. MODIS methodology to identify reed stands can be applicable to the Migratory locust habitats in other geographic areas.     

Shoreline Development Drives Invasion of Phragmites australis and the Loss of Plant Diversity on New England Salt Marshes

Abstract:  The reed Phragmites australis Cav. is aggressively invading salt marshes along the Atlantic Coast of North America. We examined the interactive role of habitat alteration (i.e., shoreline development) in driving this invasion and its consequences for plant richness in New England salt marshes. We surveyed 22 salt marshes in Narragansett Bay, Rhode Island, and quantified shoreline development, Phragmites cover, soil salinity, and nitrogen availability. Shoreline development, operationally defined as removal of the woody vegetation bordering marshes, explained >90% of intermarsh variation in Phragmites cover. Shoreline development was also significantly correlated with reduced soil salinities and increased nitrogen availability, suggesting that removing woody vegetation bordering marshes increases nitrogen availability and decreases soil salinities, thus facilitating Phragmites invasion. Soil salinity (64%) and nitrogen availability (56%) alone explained a large proportion of variation in Phragmites cover, but together they explained 80% of the variation in Phragmites invasion success. Both univariate and aggregate (multidimensional scaling) analyses of plant community composition revealed that Phragmites dominance in developed salt marshes resulted in an almost three-fold decrease in plant species richness. Our findings illustrate the importance of maintaining integrity of habitat borders in conserving natural communities and provide an example of the critical role that local conservation can play in preserving these systems. In addition, our findings provide ecologists and natural resource managers with a mechanistic understanding of how human habitat alteration in one vegetation community can interact with species introductions in adjacent communities (i.e., flow-on or adjacency effects) to hasten ecosystem degradation.     

Plants' use of different nitrogen forms in response to crude oil contamination

In this study, we investigated Phragmites australis’ use of different forms of nitrogen (N) and associated soil N transformations in response to petroleum contamination. ¹⁵N tracer studies indicated that the total amount of inorganic and organic N assimilated by P. australis was low in petroleum-contaminated soil, while the rates of inorganic and organic N uptake on a per-unit-biomass basis were higher in petroleum-contaminated soil than those in un-contaminated soil. The percentage of organic N in total plant-assimilated N increased with petroleum concentration. In addition, high gross N immobilization and nitrification rates relative to gross N mineralization rate might reduce inorganic-N availability to the plants. Therefore, the enhanced rate of N uptake and increased importance of organic N in plant N assimilation might be of great significance to plants growing in petroleum-contaminated soils. Our results suggest that plants might regulate N capture under petroleum contamination.     

Effectiveness of vegetation on phosphorus removal from reclaimed water by a subsurface flow wetland in a coastal area

This work was conducted to evaluate the effectiveness and influence factors of vegetation on phosphorus (P) removal from reclaimed water in constructed wetlands. Comparisons were conducted between one pilot scale subsurface flow wetland (P-SSFW) and two demonstration subsurface flow wetlands, which were series-wound and named as first subsurface flow wetland (F-SSFW), and second subsurface flow wetland (S-SSFW), respectively. The three wetlands had the same vegetation and substrate, but different pH values, total dissolved solids (TDS) and P loads. Results showed that the P content in the vegetation shoots of the F-SSFW was 2.16 mg/g, while 2.31 mg/g in the S-SSFW and 2.69 mg/g in the P-SSFW. These differences were likely caused by the higher pH and TDS in the reclaimed water. The P content also differed among the tissues of the plant, which were 5.94-6.44 mg/g, 2.20-2.77 mg/g, 1.31-1.46 mg/g and 1.53-1.88 mg/g in the flowers, leaves, stems, and roots, respectively. The greatest discrepancy was observed in the leaves, indicating that the environment of the wetlands had the greatest influence on the leaves. When the total phosphorus (TP) load was lower, the proportion of P removed by vegetation assimilation was 16.17% in the P-SSFW, 12.90% in the F-SSFW and 13.29% in the S-SSFW. However, the relative removal efficiency by vegetation among the three wetlands did not vary greatly from that observed in other studies. Moreover, the influence of pH, TDS and TP load was not as great as the influence of the vegetation species, type of substrate, influent style or climate.     

崇明滩涂湿地不同盐度梯度下芦苇种群及土壤的生态化学计量学特征

为了研究不同盐度梯度下芦苇(Phragmites australis)的生态适应性及其生长的限制因子,对崇明盐度梯度下的3个滩涂湿地生长的芦苇及土壤生态化学计量学指标进行测定;分析不同盐度下芦苇种群的生态化学计量学之间的差异,及土壤与芦苇元素、元素比之间的相关性。结果表明:(1)崇明滩涂湿地土壤C、N、P含量和C/N、C/P、N/P平均值分别是15.01、0.69、0.86g/kg,22.09、21.87、0.96。芦苇的C、N、P含量及C/N、C/P、N/P平均值分别为413.17、10.75、2.53g/kg,41.49、293.58、7.29。(2)随着崇明滩涂湿地土壤盐度增加,土壤的C、N含量及芦苇的C含量、C/N先降低后增加;土壤的C/N、C/P、N/P及植物的C/P、N/P增加;土壤的P含量及植物N、P含量降低。(3)盐度梯度下滩涂湿地土壤与芦苇生态化学计量学中的C、P、C/P、N/P之间均正相关关系,土壤N含量与植物的C/P正相关,与N/P负相关;而C/N与植物P含量之间有负相关性。(4)该研究区土壤的C、N元素较为匮乏,P含量较高;植物的N/P值小于14,说明崇明芦苇生长主要受到N的限制。     

太湖湖滨湿地沉积物氮磷与2种挺水植物氮磷的关系

在无锡太湖湖滨带布设3条样带、36个样点进行了调查,分析了表层沉积物（0~15 cm）和芦苇（Phragmites australis（Cav.）Trin.）、茭白（Zizania latifolia（Griseb.）Turcz.）2种挺水植物w（N）、w（P）的变化,揭示了沉积物N、P的空间分布以及与2种挺水植物N、P的关系。结果表明：（1）表层沉积物w（N）自上而下分别为7.89~4.24 mg.g-1（0~5 cm）、7.56~3.81 mg.g-1（0~10 cm）、7.61~3.77 mg.g-1（0~15 cm）,w（P）分别为1.293~0.532 mg.g-1（0~5 cm）、1.112~0.497 mg.g-1（0~10 cm）、0.952~0.471 mg.g-1（0~15 cm）。（2）生态修复区表层沉积物N、P的水平变化规律一致,按陆向辐射区-水位变幅区-水向辐射区依次递减,而从垂直变化来看,w（N）、w（P）均以表层最高,并依次向下层递减;硬质护坡区P的变化与之一致,但N的水平分布却按陆向辐射区-水位变幅区-水向辐射区依次递增,垂直分布呈现表层最低,并依次向下层递增变化。（3）2种挺水植物w（N）、w（P）不同,芦苇对N、P的吸收明显高于茭白（芦苇地上部分w（N）31.75~42.61 mg.g-1,地下部分w（N）13.57~18.21 mg.g-1;茭白地上w（N）14.78~23.57 mg.g-1,地下部分w（N）13.57~18.21 mg.g-1,而芦苇地上部分w（P）3.62~5.08 mg.g-1,茭白地上部分w（P）1.42~1.93 mg.g-1,地下部分w（P）0.35~0.57 mg.g-1）。2种挺水植物地上部分N、P吸收量远远大于地下部分吸收量。（4）相关分析表明,2种植物地下部分w（TP）与沉积物w（TP）呈正相关,而芦苇地下部分w（TP）与沉积物w（TP）相关性显著（P〈0.05）,说明芦苇根系对沉积物中的P具有强烈吸附作用。（5）2种植物对太湖中沉积物N、P分配有显著影响,生态恢复区沉积物中w（N）显著高于硬质护坡,而w（P）较硬质护坡显著降低,适度恢复水生植被可有效缓解湖泊水体的富营养化。