Abstract:

Aims In this study, we aim to understand how grazing would influence the partitioning of assimilated carbon in an alpine meadow on the Qinghai-Xizang Plateau.
Methods Measurements on carbon partitioning were made in a long-term grazing experiment consisting of light winter grazing and enclosure treatments. The ¹³C tracer method was used to determine the partitioning and transportation of assimilated carbon into different carbon pools.
Important findings On the 30th day following the labeling, shoots retained 32% of the initial ¹³C, and roots and soil together retained 22%; about 30% of the initial ¹³C were lost through shoot respiration. There were significant differences in the retention in soil, and the respiratory emission from soil, of assimilated carbon between the light grazing and enclosure treatments. Under light grazing, plants invested more assimilated carbon into the root and soil carbon pools. The rate of ¹³C transportation from shoots to soil and the rate of respiratory ¹³C release from soil were both greater, and the retention of ¹³C in and respiratory release from shoots were lower, under light grazing than under enclosure. Our results suggest that grazing is an important mechanism for maintenance of grassland. Grazing may cause changes in the structure and functioning of ecosystems, and induce large variations in soil carbon storage. Alpine meadow in the Qinghai-Xizang Plateau is amongst the grasslands with highest elevation in the world, and has large soil carbon storage due to low temperatures. We found no difference in soil C stocks between light grazing and enclosure treatments, indicating that light grazing would have no significant impact on soil carbon stocks.

Key words: grazing, ¹³C isotope labeling, alpine meadow, partitioning of assimilated carbon