Abstract: Aims Plant root exudates play important roles in the feedback of plant-soil-microbes interactions. However, the responses of root carbon (C), nitrogen (N) and phosphorus (P) exudate rates and their stoichiometric characteristics in the alpine steppe to long-term grazing exclusion and relationships between them and environmental factors are still poorly understood on the Qingzang Plateau. Methods In the study, we evaluated the root C, N and P exudate rates and their stoichiometric characteristics at plant community and species level, and further reveled the relationships between root exudate characteristics at plant community level and plant community characteristics, soil factors at long-term grazing exclusion field experimental site in the alpine steppe on the Qinghai-lake Basin. Important findings Our results showed that: (1) Root C and N exudate rates and their C:P and N:P at plant community level decreased in long-term grazing exclusion treatment, but root P exudate rate and their C:N were not significantly changed. (2) The long-term grazing exclusion exerted negative effects on root C, N and P exudate rates at species species, and has significant effects on their C:P and N:P simultaneously, especially them of Leymus secalinus were decreased in grazing exclusion treatment. (3) The root exudate ability of forb species was stronger than that of grass and sedge species, mainly presenting that the root C and N exudate rate of the Aster altaicus was overwhelming higher than other species. (4) The root C and N exudate rate and N:P of exudation at plant community level were significantly related with plant diversity, plant community composition, soil water content and soil N content. The further analysis illustrated that the key factors affecting root C, N and P exudate rate were different, showing that the root C exudate rate was most affected by soil factors, while root N and P exudate rate were most affected by the plant community composition. In conclusion, the long-term enclosure has been imposing significant effects on the root exudate rate and their stoichiometry in the alpine steppe, which is of great significance for understanding the changes of other ecosystem functions after grassland enclosure management in the future.

Key words: root exudation, stoichiometric characteristics, grazing exclusion, plant community composition, alpine steppe, Qinghai-Tibetan Plateau