食物资源的枯竭对丹顶鹤营养位的影响

随着扎龙湿地生物资源的迅速减少,在该地栖息的丹顶鹤种群的营养关系可能发生显著的变化.本文使用稳定同位素(δ¹⁵N和δ¹³C)监测食物资源的枯竭对丹顶鹤营养位的影响.结果表明:丹顶鹤种群的δ¹⁵N和δ¹³C的丰度范围分别为6.9‰～8.1‰和-17.8‰～-18.5‰.扎龙湿地系统以大型水禽为食物顶端的食物链长度为3.8±0.2,其中丹顶鹤种群所处的平均营养位为3.1(范围在2.9～3.3).丹顶鹤的δ¹⁵N的丰度近年波动范围为7.4‰～8.8‰(波动幅度1.4,小于营养位发生显著变化的阈值3.4),这说明在该地区活动的丹顶鹤的营养位并没有随着大面积的栖息地和食物资源的消失而发生显著变化.然而,随着本地区生物资源的枯竭,丹顶鹤种群规模迅速减少,当前必须合理解决当地居民从湿地获取生活资源的需求与丹顶鹤觅食之间的矛盾,从而更好地保护这种濒危种群.     

基于稳定同位素的湿地食物源判定和食物网构建研究进展

湿地生物营养动力学是湿地生态系统结构和功能评价研究的基础.碳、氮稳定同位素作为识别营养关系的方法,已在湿地生态系统食物来源、组成和食物链传递研究中得到广泛运用.本文系统综述了稳定同位素食物贡献度计算模型和营养级确定的基本方法和理论;讨论了动物营养分馏值和基线的选择依据;概括了湿地生态系统典型食物源及其稳定同位素变化特征;总结了草食、杂食和肉食等不同营养级动物的食物来源.指出了稳定同位素在湿地食物源溯源和食物网研究中的不足;基于国内外研究现状和发展趋势及需求,展望了未来同位素技术在湿地食物网生态学研究中的运用前景和研究重点,提出需要加强稳定同位素营养分馏和基线的影响因素、样品处理和保存方式研究以及胃含物、分子标记物和多元素同位素结合分析.     

Influence of lateral gradients of hydrologic connectivity on trophic positions of fishes in the Upper Mississippi River

1. Riverscapes consist of the main channel and lateral slackwater habitats along a gradient of hydrological connectivity from maximum connection in main channel habitats to minimum connection in backwaters. Spatiotemporal differences in water currents along this gradient produce dynamic habitat conditions that influence species diversity, population densities and trophic interactions of fishes. 2. We examined the importance of lateral connectivity gradients for food web dynamics in the Upper Mississippi River during spring (high flow, moderately low temperatures) and summer (low flow, higher temperatures). We used literature information and gut contents analyses to determine feeding guilds and stable isotope analysis to estimate mean trophic position of local fish assemblages. During June and August 2006, we collected over 1000 tissue samples from four habitats (main channel, secondary channels, tertiary channels and backwaters) distributed within four hydrologic connectivity gradients. 3. Mean trophic position differed among feeding guilds and seasons, with highest values in spring. Mean trophic position of fish assemblages, variability in trophic position and food chain length (maximum trophic position) of the two dominant piscivore species (Micropterus salmoides and M. dolomieu) in both seasons were significantly associated with habitat along the lateral connectivity gradient. Food chain length peaked in tertiary channels in both seasons, probably due to higher species diversity of prey at these habitats. We infer that food chain length and trophic position of fish assemblages were lower in backwater habitats in the summer mainly because of the use of alternative food sources in these habitats. 4. A greater number of conspecifics exhibited significant among‐habitat variation in trophic position during the summer, indicating that low river stages can constrain fish movements in the Upper Mississippi River. 5. Results of this study should provide a better understanding of the fundamental structure of large river ecosystems and an improved basis for river rehabilitation and management through knowledge of the importance of lateral complexity in rivers.     

三亚蜈支洲岛海洋牧场区域夏季食物网研究

三亚蜈支洲岛海洋牧场在针对珊瑚礁修复工作、热带海洋牧场建设等方面取得了不错的效果,但海洋牧场区域的营养结构仍需要长期的监测评估。于2020年7月海洋生物调查共采集52种主要消费者,以碳(δ¹³C)、氮(δ¹⁵N)稳定同位素技术为基础,首次构建三亚蜈支洲岛海洋牧场区域食物网并进行研究。结果表明：(1)主要消费者的δ¹³C值范围在-19.10‰—-12.74‰之间,平均值为(-16.99±1.52)‰;δ¹⁵N值范围为6.43‰—14.03‰,平均值(11.24±1.70)‰。单因素方差分析结果显示,不同类群之间碳氮稳定同位素均有显著性差异(P<0.01)。(2)大型海藻和底栖微藻对主要消费者的贡献率最大为41.50%,沉积有机物(SOM)和浮游植物也是消费者的重要碳源(贡献率分别为20.05%、19.97%),悬浮颗粒有机物(POM)对消费者的碳源贡献率最低,为18.48%。(3)三亚蜈支洲岛牧场区域主要消费者的营养级范围为1.53—3.76,主要消费者营养层次分布两端少,中间多。通过系统聚类分...     

群落水平食物网能流季节演替特征

稳定碳、氮同位素比值分析技术是研究生态系统中物质循环与能量流动的有效技术.δ13C可以用来判断食物网中不同生物的能量来源;δ15N主要用于确定生物在食物网中所处的营养位置.通常用δ13C—δ15N图来表征某一特定时间或空间的食物网结构,但是这种方法在比较不同时间和空间食物网结构中功效较差.同时这种定性描述食物网结构也无法满足食物网复杂变化下的假说验证.应用环形统计方法,以太湖梅梁湾鱼类群落为例,定量评价了群落水平食物网能流季节演替特征.结果表明太湖梅梁湾鱼类营养生态位移动的季节特征明显.进一步物种水平分析结果表明,各种鱼类角度和幅度随季节均有变化.Rayleigh检验结果表明,群落中不同种类在秋冬、冬春和夏秋均有显著的一致的方向变化;而春夏期间不显著.Watson-William检验结果表明,群落水平的鱼类营养生态位移动在秋冬和冬春季节转换中有显著差异.引起鱼类群落水平营养生态位在食物网空间中季节性移动的主要因素为可利用资源稳定同位素的季节变化和不同鱼类种群自身的食性季节性转变.同时,由于梅梁湾食物网鱼类群落杂食性水平高,季节性浮游初级生产力成为食物网能量流动的重要驱动作用.因此,在富营养化生态系统中,食物网群落水平营养生态位季节波动也暗示了系统稳定性的下降.定量评价食物网变化有助于认识和理解食物网结构与功能在生态学和生态系统管理等方面的重要.     

Linking aquatic and terrestrial food webs – Odonata in boreal systems

1. It is increasingly realised that aquatic and terrestrial systems are closely linked. We investigated stable isotope variations in Odonata species, putative prey and basal resources of aquatic and terrestrial systems of northern Mongolia during summer. 2. In permanent ponds, δ¹³C values of Odonata larvae were distinctly lower than those of putative prey, suggesting that body tissue comprised largely of carbon originating from isotopically light carbon sources. Presumably, prey consumed during autumn and winter when carbon is internally recycled and/or methanotrophic bacteria form an important basal resource of the food web. In contrast, in a temporary pond, δ¹³C values of Odonata larvae were similar to those of putative prey, indicating that their body carbon originated mainly from prey species present. 3. Changes in δ¹⁵N and δ¹³C values between larvae and adults were species specific and reflected differential replacement of the larval isotopic signature by the terrestrial diet of adult Odonata. The replacement was more pronounced in Odonata species of permanent ponds than in those of the temporary pond, where larvae hatched later in the year. Replacement of larval carbon varied between tissues, with wings representing the larval isotopic signature whereas thoracic muscles and eggs reflected the δ¹⁵N and δ¹³C values of the terrestrial diet of adults. 4. The results suggest that because of their long larval development, Odonata species of permanent ponds carry the larval signature, which is partly replaced during their terrestrial life. Terrestrial prey forms the basis for egg production and thus the next generation of aquatic larvae. In temporary ponds, in contrast, Odonata species rely on prey from a single season, engage in a prolonged aquatic phase and hatch later, leaving less time to acquire terrestrial prey resources for offspring production. Stable isotope analysis provided important insights into the food webs of the waterbodies and their relationship to the terrestrial system.     

天然次生林和4种人工林树冠层蚂蚁功能多样性研究

为了探讨不同类型林地中树冠层蚂蚁功能多样性的变化,本研究采用树栖蚂蚁陷阱法调查云南省绿春县天然次生林和4种人工林的树冠层蚂蚁群落,并调查了植物多样性及植物垂直密度变化。测定54种蚂蚁的头长、头宽、胸长和后足腿节长,并计算和比较了不同类型样地间的功能丰富度、功能均匀度和功能离散度的差异。结果表明:(1)不同类型林地间树冠层蚂蚁的功能丰富度指数(FR_ic)有显著差异,紫胶林和紫胶林-玉米混农林显著高于桉树林、天然次生林和橡胶林,同时橡胶林显著高于桉树林;不同类型林地间树冠层蚂蚁的功能均匀度指数(FE_ve)有显著差异,天然次生林和紫胶林显著高于桉树林。不同类型林地间树冠层蚂蚁的功能离散度指数(FD_iv)有显著差异,桉树林、橡胶林和紫胶林显著高于紫胶林-玉米混农林,且橡胶林显著高于天然次生林。(2)树冠层蚂蚁功能均匀度随枯落物盖度的增加而升高;功能离散度随枯落物盖度、草本植物盖度和>300 cm处的垂直密度的增加而升高。不同林地类型中紫胶林的树冠层蚂蚁功能多样性相对较高,而这其中枯落物盖度、草本植物盖度和>300 cm处的垂直密度等环境因素起到一定积极的作用,因此对人工林进行合理的管护有利于生态系统功能的实现和保护。