title: Effect of aridification on the replacement of zonic species, Stipa baicalensis Roshev., by azonic species, Leymus chinensis Tzvel., in the steppe of China.
abstract: The perennial grass Stipa baicalensis is the zonic species in the steppe of China, but is currently being replaced by the azonic species of Leymus chinensis. In this area, aridification is on the increase; therefore, we hypothesize that water competition plays a significant role in this succession. The limit of osmotic adjustment in S. baicalensis (13.94%-16.30% PEG) was much lower than that in L. chinensis (17.20%-24.50% PEG) in response to drought. The synoptic causal model accounted for most of the variation in the process of physiological regulation as indicated by the small residual effect (0.121-0.161). These results demonstrated that the two species dealt with drought in different ways. Stomata of L. chinensis acted more directly on transpiration, and the advantage in water competition resulted from the powerful stomatal control. On the other hand, S. baicalensis was more easily affected by non-stomatal limitation which was physiologically inactive in response to drought. Results supported the hypothesis above. S. baicalensis was more susceptible to the damage of aridification and was less competitive to water than L. chinensis.
authors.affiliation: School of Municipal and Environmental Engineering, Harbin Institute of Technology, State Key Laboratory of Urban Water Resource and Environment, 150090 Harbin, China. wli@hit.edu.cn
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Ji-Xian
authors.initials: JX
authors.lastname: Yang
authors.forename: Fang
authors.initials: F
authors.lastname: Ma
authors.forename: Yun-Fei
authors.initials: YF
authors.lastname: Yang
authors.forename: Chein-Chi
authors.initials: CC
authors.lastname: Chang
authors.forename: Chong-Wei
authors.initials: CW
authors.lastname: Cui
mesh_terms: D002681:China; D003889:Desert Climate; D004777:Environment; D006109:Poaceae / Q000254:growth & development*; D011157:Population Dynamics; D014867:Water
chemical_list: D014867:Water