摘要
稳定性同位素技术应用于生态系统物质流动和食物链营养关系的研究方法 ,是基于生物体内天然存在的同位素比值与它们食物密切相关这一原理建立起来的。即将生物体内的稳定性同位素比值 (如δ1 3C)作为一自然标记 ,根据物种间该值的相对差异 ,追踪生态系统中的主要物质 (如碳源 )的来源和物质流动。于 2 0 0 2年 4～8月测定了高寒草甸生态系统主要生物群落中物种的稳定性碳同位素比值 (δ1 3C) ,依据得到的系统的富集因子( 1 0 5± 0 4 5 )‰ ,分析并确定了所测物种间的取食与被取食关系。结果发现 :高寒草甸生态系统由 5条主要的食物链构成 ,其中 1条为“植物→小型哺乳类→食肉兽 /猛禽”的三节点食物链 ,2条为“植物→牲畜和植物→植食性鸟类”的二节点食物链 ,2条分别为“植物→昆虫→雀形目鸟类→猛禽 /食肉兽”和“植物→昆虫→两栖类→猛禽 /食肉兽”的四节点食物链 ;系统食物链的最大长度为 3 5 3 ,与系统的最大节点数相近。表明稳定性碳同位素可以作为分析高寒草甸生态系统食物网和食物链结构以及食物链长度的有效代理 (proxy)。
The stable isotope approach is based on the fact that naturally occurring stable isotope ratios in consumer tissues can be related to those in consumers'diets.Changes in,or fractionation of,stable carbon isotope ratios ( 13C/ 12C) occur with trophic level and are of the order of 1‰-2‰.Thus,isotope measurement of consumers'tissues can reveal information about their ingested foods in ecosystems that are relatively simple.Determination of stable carbon isotope signatures in the alpine meadow ecosystem demonstrated that the ecosystem was composed of five main food chains,one was three-noded food chain characterized by “plants → small mammals → raptors (or carnivorous mammals)”;two each were two-noded characterized by “plants → vegetarian passerine birds or livestock”;and two each were four-noded and composed of “plants → insects → passerine birds → raptors (or carnivorous mammals)” or “plants → insects → amphibians → raptors (or carnivorous mammals)”,respectively.The maximum length of food chain in the alpine meadow ecosystem was 3.53,which was grossly equal to maximum node number,i.e.,4.In summary,stable carbon isotope ratios can be used as a proxy to analyze food chains and food webs in the alpine meadow ecosystems.
基金
国家自然科学基金资助项目 ( 3 0 2 70 2 17)
