Selecting suitable shrub and herb species to revegetation from the perspective of root exudates: An implication for ecological restoration of desertification in an alpine meadow of the eastern Tibetan Plateau

Till now, the lack of research regard to root exudates is still serious in the restoration process of desertification alpine meadow in the eastern Tibetan plateau, although recovery of desertification land resulted from overgrazing and climate change is known to be shaped by the rhizosphere. Therefore, we measured root carbon (C) exudate rates of Kengyilia rigidula (Keng) S. L. Chen., Rhodiola kirilowii (Regel) Maxim., Elymus nutans Griseb., Hippophae rhamnoides L. and Salix cupularis Rehd. by sampling root exudates in situ in a desertification alpine meadow, as well as determined the volatile components using GC-MS. The results showed that 1) Root C exudate rates were as follows: R. kirilowii > K. rigidula > E. nutans > S. cupularis > H. rhamnoides, and R. kirilowii was significantly higher than H. rhamnoides (p < 0.05). 2) Common volatile substances of the five plants mainly contained hydrocarbons (above 13.16%), esters (above 11.83%) and phenols (above 6.27%), and the relative amounts of hydrocarbons and phenols were the highest in R. kirilowii respectively, while esters were the highest in S. cupularis among the five plant species. Thereinto, 2-hydroxy-1-(hydroxymethyl) ethyl ester was the highest content in R. kirilowii while 2,4-di-tert-butyl phenol was the highest content in S. cupularis. 3) As the specific allelochemical components of herbs and shrubs, heptadecane was the highest content in R. kirilowii among the three herb species while pentacosane was relatively high content in S. cupularis between the two shrubs, and the relative amount of palmitic acid in R. kirilowii was about twice that in H. rhamnoides and S. cupularis, accounting for 1.64%. Collectively, our results suggest that S. cupularis and R. kirilowii should be regarded as the better choice of pioneer plant species to be applied to ecological restoration of desertification alpine meadow.