Analysis on Food Web Structure in Alpine Meadow Ecosystem:Evidence from Stable Carbon Isotope Signatures

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.