Applications of stable isotopes to study plant-animal relationships in terrestrial ecosystems

As natural tracers, stable isotopes have been extensively used in plant physiological, ecological and envi- ronmental research. Recently, animal physiological ecologists have also applied stable isotope techniques to study plant- animal relationships. The isotopic compositions of animal body generally reflect and integrate their diets over a time period ranging from hours to years to the lifetime of an indi- vidual. When animal living habitat changes or animals move to a new environment, the animal isotopic compositions will shift accordingly. Thus, stable isotope signatures of an ani- mal can truly reflect its food sources, habitat, distribution and movement patterns during a given time period. More- over, by analyzing animal-tissue isotopic compositions at different temporal scales, we can improve our understanding of animal adaptation to environmental changes. Stable iso- tope technique also provides an ideal tool to study animal foodweb relationship and community structure because of isotopic fractionation during the processes of nutrient as- similation by animals. Stable isotope technique can continu- ously measure animal trophic position in a foodweb, which can eventually reveal the predator-prey relationship and its role in determining matter balance and energy flow in the entire ecosystem. Stable isotope technique has been one of the most important and efficient tools in studying plant-animal relationship. In this paper, we first review recent advances in the application of stable isotope techniques to plant-animal relationship research then evaluate their advantages and disadvantages, and finally discuss some future directions associated with stable isotope applications to plant-animal relationship research.