Impacts of the Yangtze River water transfer on the restoration of Lake Taihu

In order to improve the water quality and to abate the jeopardy of water bloom in Lake Taihu, China, two experimental water transfers from the Yangtze River to Lake Taihu were conducted in winter–spring 2002 and in summer–autumn 2003. In this study, an ecological model (EcoTaihu) was introduced to assess their environmental effects. First, the model was re-calibrated and reverified for the periods of the water transfer, then numerical calculations with and without the water transfer were carried out. The percentage of the area where water quality was improved by the water transfer was calculated in seven sub-zones of the lake. The results show that the experimental water transfers in both of the periods have notable positive effects on debasing the concentration of phytoplankton, total nitrogen and dissolved oxygen in some sub-areas. The positive effects fluctuated with the duration of the water transfer, and were different for different water quality parameters and in different sub-zones. Among the five water quality parameters considered, chlorophyll a achieved the most significant improvement. There are no notable positive effects on the total phosphorus in any sub-zones. Meiliang Bay, Gonghu Bay and Northwest Zone had more positive effects than the east epigeal zone and Dongtaihu Bay. As the water transfer results in net input of nitrogen and phosphorus to Lake Taihu, it can only be used as an emergency measure to abate the jeopardy resulting from water bloom. Otherwise, the water transfer would increase the risk of eutrophication in Lake Taihu if the concentration of phosphorus and nitrogen in the influent water was not cut down to a reasonable level.     

Effects on water quality following water transfer in Lake Taihu,China

To improve lake water quality, two experimental water transfers were conducted in winter–spring 2002 and summer–fall 2003 in Lake Taihu, a large shallow lake in China. Both observed data and estimated nutrient concentration with the elimination of effect from natural factors were used in this research to assess the spatial and temporal variations of water quality improvement induced by the two transfers. Clear improvement of water quality associated with deduction of TN, TP, and chlorophyll a (Chl-a) concentration was observed in many areas of the lake during the two water transfers. The over all reduction in TP concentration was notable in Southwest Zone, Centre Zone, and Dongtaihu Bay during the 2002 transfer, and was more pronounced in Meiliang Bay and Southwest Zone during the 2003 transfer period. However, the reduction in TN and Chl-a concentration was relatively weak. Results indicate a less impressive improvement of water quality from water transfer in large lakes than in small ones as the effectiveness of water transfer in large lakes is generally limited by large size, complex boundaries, and the difficulty of finding proper water source to be transferred. The comparison of observed and estimated water transfer effectiveness suggests a greater improvement of water quality derived from water transfer than appeared from the observation.     

太湖大型底栖动物群落结构及多样性

为揭示现阶段太湖大型底栖动物群落现状及其对生态环境变化的响应, 于2007年2月至2008年11月对太湖大型底栖动物进行为期两周年的季度调查。30个采样点共记录底栖动物3门7纲19科40种, 底栖动物平均密度和生物量空间差异较大, 平均密度高值出现在梅梁湾、竺山湾及河口, 主要为寡毛纲颤蚓类; 平均生物量高值出现在贡湖湾、西湖区、东太湖和东部湖湾, 主要为软体动物。霍甫水丝蚓(Limnodrilus hoffmeisteri)、中华河蚓(Rhyacodrilus sinicus)、河蚬(Corbicula fluminea)、铜锈环棱螺(Bellamya aeruginosa)、中国长足摇蚊(Tanypus chinensis)和钩虾属一种(Gammarus sp.)是现阶段太湖大型底栖动物的优势种。聚类分析将30个采样点分成3组, 相似性分析检验表明各聚类组大型底栖动物群落具有显著差异(P<0.05)。多样性分析结果表明, 东太湖和东部湖湾物种多样性、丰富度和均匀度最高, 优势种为腹足纲螺类; 梅梁湾、竺山湾及河口多样性最低、密度最高, 霍甫水丝蚓和中华河蚓在该区占据绝对优势; 贡湖湾、湖心和西湖区多样性处于中等水平, 其优势种为河蚬。研究结果表明营养水平、底质类型以及水生植被的分布是决定太湖大型底栖动物群落结构及多样性的关键因子。     

Seasonal dynamics and grazing rate of zooplankton in Yueqing Bay,China

The species composition,biomass,abundance,and species diversity of zooplankton were determined for samples collected from August 2002 to May 2003 from 14 stations in Yueqing Bay,China.Phytoplankton growth rate and microzooplankton grazing rate were obtained by using the dilution method developed by Landry and Hassett.The spatial and temporal variations of zooplankton and its relationship with environmental factors were also analyzed.The results showed that the zooplankton in the Yueqing Bay could be divided into four ecotypes,namely coastal low saline species,estuary brackish water species,offshore warm water species,and eurytopic species.A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic larva were identified in the Yueqing Bay.The coastal low saline species was the dominant ecotype in the study area,and the dominant species were Labidocera euchaeta,Acartia pacifica,Acrocalanus gibber,Pseudeuphausia sinica,and Sagitta bedoti among others.There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas.The peak biomass appeared in August,descending in November and in May,and the lowest biomass appeared in February.Similarly,the highest abundance of zooplankton was observed in August,with the abundance descending in the following months:May,November,and February.There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton.They both increased from the upper to the lower bay in February and May,but decreased from the upper to the lower bay in August.Biomass and abundance were evenly distributed in the Yueqing Bay in November.Moreover,there was marked seasonal variation in the species diversity of zooplankton,which conformed to the abundance of zooplankton.Results of the dilution experiments indicated that there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of microzooplankton grazing on phytoplankton varied seasonally.Phytoplanktons were growing at 0.26-2.07/d and grazed by microzooplankton at a rate of 0.15--0.48/d in different seasons.     

三门湾浮游动物的季节变动及微型浮游动物摄食影响

2002年8月、11月、2003年2月和5月,在三门湾进行了4个航次生物、化学和水文等专业综合调查。根据采集的浮游动物样品的分析鉴定及海上现场实验结果,对浮游动物的群落组成、生物量、丰度、多样性指数的分布和季节变动及其浮游动物对浮游植物的摄食影响进行研究。结果表明,三门湾浮游动物有67属,89种,16类浮游幼体,主要可划分为4个生态类群：以近岸低盐类群为主,其优势种为中华哲水蚤Calanus sinicus、真刺唇角水蚤Labidocera etwhaeta、捷氏歪水蚤Tortanus derjugini、太平洋纺锤水蚤Acartiapacifica、中华假磷虾Pseudeuphausia sinica和百陶箭虫Sagitta bedoti等。半咸水河口类群、暖水性外海类群和广布种相对较少。浮游动物生物量和丰度的平面分布趋势除了夏季有所差异外,其它季节基本一致。2月份和5月份,浮游动物生物量和丰度,从湾顶向湾口呈逐渐增加趋势;8月份,湾口区生物量最高,而丰度高值区出现在湾顶部;11月份,生物量和丰度的平面分布相对均匀。浮游动物种类多样性指数有明显的季节变化,其动态变化与浮游动物种数和丰度的变化一致。微型浮游动物对浮游植物存在摄食压力,且有季节变化,摄食率的变化在0．18．0．68d^-1,微型浮游动物的摄食率低于相同季节的浮游植物生长率。微型浮游动物对浮游植物摄食压力的变化范围为16．1％-49．1％d^-1,对初级生产力摄食压力的变化在58．3％-83．6％d^-1。11月份,微型浮游动物对浮游植物和初级生产力的摄食压力均出现最高值。     

太湖湖岸带浮游植物初级生产力特征及影响因素

利用高频溶解氧监测,估算了太湖梅梁湾湖岸带浮游植物初级生产力的高频变化特征。结合同步气象监测及浮游植物、浮游动物和营养盐的周年逐周观测数据,分析了气象和环境条件对富营养化湖泊浮游植物初级生产力的影响。结果发现,高频溶解氧监测估算的初级生产力变化与浮游藻类生物量的变化一致,能够反映出浮游植物生产力的昼夜变化、季节变化等规律。统计分析表明,气温对太湖这一富营养化湖泊初级生产力影响很大;氮的供给与浮游动物的选择性牧食也是影响浮游植物初级生产力的重要因素。湖岸带的水华堆积过程对初级生产力影响巨大,气象、水文过程又加剧了蓝藻水华初级生产力的变化幅度,反映出富营养化湖泊初级生产力可能存在极大的时空不均一性。研究表明,溶解氧高频监测法估算初级生产力能够捕捉到湖泊初级生产力的快速变化过程,可以用于富营养化湖泊初级生产力监测、蓝藻水华灾害预警中。     

基于VGPM模型和MODIS数据估算梅梁湾浮游植物初级生产力

基于MODIS影像数据反演的2009年2月份至12月份太湖梅梁湾水域表面叶绿素a、悬浮物浓度以及水温数据,结合初级生产力垂向归纳模型(Vertically Generalized Production Model:VGPM)估算获得梅梁湾2009年逐月平均日初级生产力时空分布。结果表明,梅梁湾2009年年平均日初级生产力及逐月平均日初级生产力空间分布差异显著,呈现从湾内向湾口逐渐递减的趋势。时间序列分析显示,梅梁湾初级生产力季节差异显著,夏季>秋季>春季>冬季,全年初级生产力主要集中在夏季,占47.4%。通过分析VGPM模型中几个输入参数对初级生产力的影响,发现悬浮物浓度与标准化初级生产力存在显著负冥函数关系,反映沉积物再悬浮引起的悬浮物浓度增加能降低水体初级生产力。温度对初级生产力也有一定的调控与制约,与初级生产力呈现正相关趋势,在低于21℃的温度范围内与最大光合作用速率呈现正相关。     

Does the intermediate disturbance hypothesis comply with thermodynamics?

A unique data set from Keszthely Bay, Lake Balaton has been applied to develop a dynamic structural model able to describe the observed changes in phytoplankton biomass and diversity. We tested whether the model reacts according to the Intermediate Disturbance Hypothesis and according to the hypothesis that ecosystem reactions attempt to maximize the thermodynamic function exergy under prevailing conditions. If the answer to these tests are confirmatory, it can be considered a support for IDH and for the use of the exergy maximization principle as a general principle to explain ecosystem reactions.     

Seasonal dynamics of zooplankton and grazing impact of microzooplankton on phytoplankton in Sanmen Bay, China

The species composition, biomass, abundance and species diversity of zooplankton were determined for samples collected from 12 stations in Sanmen Bay, China, in four cruises from August 2002 to May 2003. Growth of phytoplankton and grazing rates of microzooplankton were measured using the dilution technique. The spatial and temporal variation of zooplankton and its relationship with environmental factors were also analyzed. The results showed that a total of 89 species of zooplankton belonging to 67 genera and 16 groups of pelagic larvae were found in Sanmen Bay. The coastal low-saline species was the dominant ecotype in the study area, and the dominant species were Calanus sinicus, Labidocera euchaeta, Tortanus derjugini, Acartia pacifica, Pseudeuphausia sinica and Sagitta bedoti. Maximum biomass was recorded in August, followed by November and May, and the lowest biomass was recorded in February. Similarly, the highest abundance of zooplankton was observed in August, followed by May, November, and February. Grazing pressure of microzooplankton on phytoplankton in Sanmen Bay existed throughout the year, although the grazing rate of microzooplankton on phytoplankton varied with the season. Estimates for growth rate of phytoplankton ranged from 0.25 d^?1 to 0.89 d^?1, whereas grazing rate of microzooplankton ranged between 0.18 d^?1 and 0.68 d^?1 in different seasons. The growth rate of phytoplankton exceeded the grazing rate of microzooplankton in all the seasons. Grazing pressure of microzooplankton on phytoplankton ranged from 16.1% d^?1 to 49.1% d^?1, and the grazing pressure of microzooplankton on primary production of phytoplankton ranged from 58.3% d^?1 to 83.6% d^?1 in different seasons.     

Seasonal dynamics of zooplankton and grazing impact of microzooplankton on phytoplankton in Sanmen Bay, China

The species composition, biomass, abundance and species diversity of zooplankton were determined for samples collected from 12 stations in Sanmen Bay, China, in four cruises from August 2002 to May 2003. Growth of phytoplankton and grazing rates of microzooplankton were measured using the dilution technique. The spatial and temporal variation of zooplankton and its relationship with environmental factors were also analyzed. The results showed that a total of 89 species of zooplankton belonging to 67 genera and 16 groups of pelagic larvae were found in Sanmen Bay. The coastal low-saline species was the dominant ecotype in the study area, and the dominant species were Calanus sinicus, Labidocera euchaeta, Tortanus derjugini, Acartia pacifica, Pseudeuphausia sinica and Sagitta bedoti. Maximum biomass was recorded in August, followed by November and May, and the lowest biomass was recorded in February. Similarly, the highest abundance of zooplankton was observed in August, followed by May, November, and February. Grazing pressure of microzooplankton on phytoplankton in Sanmen Bay existed throughout the year, although the grazing rate of microzooplankton on phytoplankton varied with the season. Estimates for growth rate of phytoplankton ranged from 0.25 d⁻¹ to 0.89 d⁻¹, whereas grazing rate of microzooplankton ranged between 0.18 d⁻¹ and 0.68 d⁻¹ in different seasons. The growth rate of phytoplankton exceeded the grazing rate of microzooplankton in all the seasons. Grazing pressure of microzooplankton on phytoplankton ranged from 16.1% d⁻¹ to 49.1% d⁻¹, and the grazing pressure of microzooplankton on primary production of phytoplankton ranged from 58.3% d⁻¹ to 83.6% d⁻¹ in different seasons.     

太湖梅梁湾湖岸带浮游植物群落演替及其与水华形成的关系

利用2009～2010年周年观测数据,结合江苏太湖湖泊生态系统研究站15年监测数据,分析了太湖梅梁湾湖岸带浮游植物群落演替及其与蓝藻水华形成的关系.50次周监测结果表明:蓝藻门(Cyanophyta)、绿藻门(Chlorophyta)、硅藻门(Bacillariophyta)分别占浮游植物总生物量的60%、16%和22%.冬春季绿藻、硅藻为主要优势种,夏秋季蓝藻门的微囊藻占绝对优势.4月下旬～6月初,平均温度低于20℃,蓝藻没有大规模生长,硅藻门、绿藻门生物量急剧降低,总生物量小于1mg·L^-1;随后温度超过25℃,蓝藻迅速增长并很快成为绝对优势,蓝藻增加滞后于绿藻、硅藻的减少.在营养盐充足、物理因素合适的条件下,浮游植物群落结构自然演替是蓝藻水华形成的主要原因之一.     

Assessment of ecosystem health during the past 40 years for Lake Taihu in the Yangtze River Delta,China

An assessment of the ecosystem health of Lake Taihu in eastern China from 1960 to 2005 was conducted using separate and aggregated chemical and biological indicators. The chemical oxygen demand, the total nitrogen, total inorganic nitrogen and total phosphorus concentrations, and the molar ratio of TN to TP (N/P) have all significantly increased (P < 0.05) since 1980. The trophic state index increased from 35.0 in 1960 to >60.0 in 1990, confirming that Lake Taihu changed from being oligotrophic to being eutrophic. These changes in water quality have led to corresponding changes in species composition and in the densities and biomasses of many aquatic species. Algal blooms have occurred frequently since the late 1980s, leading to the dominance of small zooplankton and benthic invertebrates. About 41 fish, 65 zooplankton and 16 macrophyte species were estimated to have disappeared from the lake since the late 1980s. Buffer capacity increased for phytoplankton and zooplankton but decreased for zoobenthos. These results suggest that the Lake Taihu ecosystem was in better health in 1960, and has deteriorated since 1980.     

太湖浮游植物优势种长期演化与富营养化进程的关系

利用1991年至2002年每月一次的监测资料,系统分析了浮游植物优势种和生物量的周年变化情况。同时,总氮、总磷和浮游植物叶绿素a含量等相关资料也被用于解释太湖富营养化演化与浮游植物的关系。结果显示,太湖总氮、总磷、叶绿素a和生物量均呈自梅梁湾底至湖心的逐步递减趋势。在20世纪80年代末太湖刚开始富营养化时,浮游植物优势种群从硅藻转变为蓝藻。之后,浮游植物优势种群一直是蓝藻,但各年的浮游植物总生物量有变化。总氮、总磷、叶绿素a和生物量的年均值持续增长至1996年,其后有逐步下降的趋势,究其原因可能和当地政府在太湖流域的控制排污行动有关。微囊藻在太湖的占优是太湖富营养化的标志之一。研究结果说明浮游植物在大型浅水湖泊中可以作为反映富营养化进程的生态指标。     

太湖水华程度及其生态环境因子的时空分布特征

湖泊水华是全世界面临的严重生态环境问题之一,对人类和生态系统健康都有重大影响。由于湖泊水华受流域面源、点源污染、气候、水文因子以及湖泊生态系统自身特征等众多因素影响,水华是否爆发、其严重程度及时空分布特征呈现明显的复杂性。以我国太湖为研究区域,基于近年的水华及水环境的监测数据,用自组织特征映射神经网络对太湖不同监测点的水华程度进行了自动聚类分析。结果表明,太湖水华程度呈现为明显的无水华、轻度、中度和重度水华4类。不同程度水华的叶绿素a、水温、COD_(Mn)、营养盐、浮游植物生物量以及藻种(蓝藻、绿藻、硅藻)结构的时空差异显著,不同变量间的关系复杂,有助于深入认识太湖近年水华发生的时空变异特性。     

太湖西北湖区2003-2012年间氮磷浓度及浮游植物主要类群变化趋势分析

基于2003-2012年太湖竺山湖和西部沿岸区水体理化指标与浮游植物丰度的逐月监测数据,分析了两个湖区氮磷营养盐状态和浮游植物丰度以及浮游植物主要类群的年际变化趋势及季节变化特征,探讨了浮游植物群落变化与水温及营养盐指标间的关系。结果表明：10年间两个湖区氮磷营养盐浓度总体呈下降趋势,以竺山湖TN、NH₃-N浓度和西部沿岸区NO₃-N浓度下降最为显著;浮游植物丰度总体呈上升趋势,蓝藻在群落结构中日益占据绝对优势;季节变化上,氮营养盐浓度表现为春冬季节高于夏秋季节,TP浓度和浮游植物丰度呈相反的变化趋势。Pearson相关分析显示,水温、NH₃-N浓度和TN/TP是影响蓝藻丰度及其在浮游植物群落中所占比例的主要因素。在温度和营养盐结构的共同作用下,10年间两个湖区蓝藻水华暴发时间逐渐提前,而消退时间逐渐滞后,水华持续时间逐年上升。在全球变暖背景下,太湖水华治理需执行更加严格的氮磷限制阈值,且在重污染的西北湖区控磷依然是关键。     

Sedimentation in Arctic Canada: Species composition and biomass of phytoplankton contributed to the marine sediments in Frobisher Bay

Summary Sedimentation of phytoplankton provides food and energy for zoobenthic communities. In this study the rates, species composition and biomass of phytoplankton input to Frobisher Bay sediments were examined during ice (late November to July) and open water (late July to October) periods from 1982 to 1985. The rates were higher on the sea bed than at 20 m. The minimum rate (3x10⁵ cells·m^-2·day^-1) of sedimentation occurred during the early part of the ice period. It increased as the ice thickened and reached a maximum of 2.8x10⁸ cells·m^-2·day^-1 after the phytoplankton bloom at the beginning of the open water period in the first two weeks of August. The sedimented phytoplankton was dominated by diatoms, with a great majority of pennate species during the spring (April to June) and centric forms during the summer (July to August). Green flagellates, dinoflagellates and chrysophytes occurred as a low percentage of the total population in all seasons. Other indicators (chlorophyll a and phaeopigments) showed highest biomass levels in the deepest traps. They were consistently low during the winter (December to March) and reached their maxima during the open-water period of summer. Their abundance was correlated with the seasonal cycle of the phytoplankton in the water column.     

Ecological restoration and factors regulating phytoplankton community in a hypertrophic shallow lake,Lake Taihu,China

A restoration program for the control of cyanobacterial blooms and the re-establishment of submerged macrophytes was conducted in Meiliang Bay of Lake Taihu since 2003. The effect of this ecological projects on plankton community and water quality, and factors regulating phytoplankton community were investigated in 2005. In general, some improvements of water quality occurred in the ecological restoration region, especially in the region of restoring aquatic macrophytes, where we detected significant reduction of nutrients. However, it seems the abundance of phytoplankton cannot be effectively control by the present ecological engineering. The phytoplankton abundance was high in the target restoration zone. Results of CCA and correlation analysis indicate that the phytoplankton community was mainly controlled by physico-chemical factors. Cyanobacteria species were positively related with pH, temperature, TP and TSS, while negatively related with TN, TN/TP and conductivity. The most discriminant variable was TN/TP, which explained 15% of the total variance of phytoplankton. However, TN was more important for the fluctuation of TN/TP than TP. It suggested that TN may be the ultimate factor controlling the phytoplankton community in Lake Taihu. Variation partitioning analysis showed that the pure contribution of crustacean was low for the variation of phytoplankton, suggesting that top-down control by crustacean zooplankton was weak in Lake Taihu. In general, this study suggested the reduction of nutrient load should be more important than top-down control using zooplankton for the ecosystem restoration in Lake Taihu.     

Seasonal dynamics and grazing rate of zooplankton in Yueqing Bay, China

The species composition, biomass, abundance, and species diversity of zooplankton were determined for samples collected from August 2002 to May 2003 from 14 stations in Yueqing Bay, China. Phytoplankton growth rate and microzooplankton grazing rate were obtained by using the dilution method developed by Landry and Hassett. The spatial and temporal variations of zooplankton and its relationship with environmental factors were also analyzed. The results showed that the zooplankton in the Yueqing Bay could be divided into four ecotypes, namely coastal low saline species, estuary brackish water species, offshore warm water species, and eurytopic species. A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic larva were identified in the Yueqing Bay. The coastal low saline species was the dominant ecotype in the study area, and the dominant species were Labidocera euchaeta, Acartia pacifica, Acrocalanus gibber, Pseudeuphausia sinica, and Sagitta bedoti among others. There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas. The peak biomass appeared in August, descending in November and in May, and the lowest biomass appeared in February. Similarly, the highest abundance of zooplankton was observed in August, with the abundance descending in the following months: May, November, and February. There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton. They both increased from the upper to the lower bay in February and May, but decreased from the upper to the lower bay in August. Biomass and abundance were evenly distributed in the Yueqing Bay in November. Moreover, there was marked seasonal variation in the species diversity of zooplankton, which conformed to the abundance of zooplankton. Results of the dilution experiments indicated that there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of microzooplankton grazing on phytoplankton varied seasonally. Phytoplanktons were growing at 0.26–2.07/d and grazed by microzooplankton at a rate of 0.15–0.48/d in different seasons. __________ Translated from Acta Ecologica Sinica, 2005, 25(8): 1853–1862 [译自: 生态学报, 2005, 25(8): 1853–1862]     

The trophic state of Lake Ladoga as indicated by late summer phytoplankton

As a part of the joint Russian-Finnish evaluation of human impact on Lake Ladoga, we studied the phytoplankton of the lake in order to find biological indicators for eutrophication. A second aim of the investigation was intercalibration of sampling and phytoplankton counting techniques between the Russian and Finnish laboratories. Phytoplankton samples were collected from 27 sampling stations in the lake and from the rivers Volkhov and Neva in 9–13 August 1993. In surface water samples the phytoplankton fresh weight biomass varied in the range 218–3575 mg m^–33. Highest biomass values were encountered in Sortavala Bay, and lowest ones in the western central part of the lake. Phytoplankton species composition varied considerably in the lake; blue-green and green algae predominated near-shore areas and Cryptophyceae in the offshore stations. Canonical correspondance analysis revealed close grouping of eutrophy indicating communities, dominated mainly by greens and blue-greens, in the most nutrient-rich parts of Lake Ladoga, the Volkhov and Svir Bays. Samples from the vicinity of the inflows of Vuoksi and Burnaya Rivers and off Pitkaranta formed a separate group, dominated by diatoms, most of which were typical to mesotrophic or eutrophy lakes. As judged by phytoplankton biomass values and chlorophyll a concentrations, Lake Ladoga may generally be classified as mesotrophic. Eutrophicated areas are found in the northern archipelago of the lake and in the areas influenced by large rivers.     

巨桉凋落叶分解对菊苣生长及光合特性的影响

采用盆栽试验,研究了巨桉凋落叶分解初期对菊苣幼苗生长和光合生理特性的影响.试验设置A₁(30 g·pot^-1)、A₂(60 g·pot^-1)、A₃(90 g·pot^-1)和对照（CK）4个凋落叶水平,将各处理的凋落叶分别与12 kg土壤混合后装盆,播种菊苣.待A₃处理植株的第3片真叶完全展开后测定菊苣光合生理指标及相关生长指标.结果表明：巨桉凋落叶分解初期明显抑制了菊苣生物量积累、叶面积的增加及光合色素的合成,且随着凋落叶施入量的增加抑制作用加大;菊苣叶片胞间CO₂浓度增加,而净光合速率、气孔导度和蒸腾速率均显著低于对照;随土壤中凋落叶含量的增加,除CO₂补偿点呈增加趋势外,其他光响应和CO₂响应的特征参数都呈明显下降趋势,并与对照差异显著.巨桉凋落叶分解过程中,其化感物质逐步释放并作用于受体植物,抑制其光合色素合成和光合作用,降低其环境适应能力,从而抑制菊苣的生长.