Analysing regional-scale patterns of C3 and C4 vegetation in the Inner Mongolia steppe through grazer wool carbon isotope composition.

The Eurasian steppe is the world’s largest contiguous terrestrial biome. Its vegetation is mainly composed of herbaceous species applying either C3 or C4 photosynthesis. The spatial pattern of C3/C4 contributions to aboveground biomass and its variation over time can be estimated from the carbon isotope composition of wool samples. This method exploits the fact that grazers’ foraging activity integrates over their grazing grounds and wool isotope composition integrates over the wool growth period, buffering small-scale spatial (km) and temporal (yr) variation. Wool can be collected easily and samples of old material can often be dated for reconstruction of time series. The theoretical background and the details of the methodology are explained and illustrated with studies from Inner Mongolia grasslands. These works reveal pronounced variation of C3/C4 proportions in space and time.