Abstract: Aims The type of photosynthetic pathway is an important driver of growth rate divergence between species, and its differences may indirectly affect carbon assimilation capacity through water transport. However, there is still a lack of direct evidence as to whether photosynthetic pathway types diverge in growth rates due to dif-ferences in hydraulic structure. Methods We used nine windbreak afforestation tree species of two photosynthetic pathway types (C₃ and C₄) as research subjects, and measured parameters such as growth rate, hydraulic efficiency and vulnerability curve to analyse the correlation between the growth rate and hydraulic traits of plants with different photosynthetic pathways. Important findings (1) Plant height and basal diameter growth rates were significantly and positively corre-lated with xylem hydraulic conductivity, and growth rates of C₄ plants were more affected by hydraulic con-ductivity than those of C₃ plants. (2) C₃ plants adopted trade-off between plant height and basal diameter growth rate and hydraulic safety, while C₄ plants achieved synergy between efficient hydraulic conductivity and em-bolism resistance. (3) Photosynthetic pathway types regulated the relationship between hydraulic efficiency and security of tree species.C₃ and C₄ plants respectively adopted the strategies of trade-off and decoupling. (4) The interspecific differences in the hydraulic safety boundaries of the nine tree species were significant,and all the hydraulic safety boundaries were negative values. The study showed that hydraulic efficiency could predict the growth of tree species, and C₄ plants (Haloxylon ammodendron and Calligonum mongolicum) had both strong resistance to embolism and high growth rate, which could be used as the main silvicultural species for sand fixation forests.

Key words: growth rate, hydraulic efficiency, hydraulic safety, Photosynthetic pathway types, hydraulic safety margin