The mixed community of C₃ and C₄ plants is easily seen in grassland ecosystem, but hardly seen in desert ecosystem. In desert regions of China, some C₃ and C₄ shrubs coexist in particular manners in some specific habitats and adapt to the extreme arid environment, which is associated with high temperature and intensive radiation. The mixed communities of C₃ undershrub Reaumuria soongorica and C₄ subshrub Salsola passerina in the Heihe River Basin in Hexi Corridor were investigated. The physiological characteristics of gas exchange of R. soongorica and S. passerina in the mixed community were determined under different drought degrees. Results showed that net photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (Gs) of R. soongorica were all higher than S. passerina, while water use efficiency of S. passerina was higher than R. soongorica. The differential responses of the two species to severe habitat shows that R. soongorica and S. passerina take different strategies for survival when suffering water scarcity in the same desert habitats: R. soongorica uses the means of maintaining a higher net photosynthetic rate and a higher transpiration rate to survive, while S. passerina survives here through the higher water use efficiency.

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Diurnal changes of photosynthetic photon flux density(A),air temperature(B),air relative humidity(C),and vapor pressure deficit from leaf to air(D)