Effect of Stubble Treatment on the Physiological Characteristics of Ammopiptanthus mongolicus

Ammopiptanthus mongolicus (Maxim.) Cheng f. is a Chinese secondary rare and endangered plant. The continuous deterioration of the natural environment of the Western Ordos Plateau National Nature Reserve threatens populations of this plant. A mechanical stubble measure was conducted as a treatment. Physiological characteristics such as leaf relative water content (RWC), leaf water potential (WPB), net photosynthetic rate (Pn), transpiration rate (Tr), water utilization efficiency (WUE), stomatal conductance (Gs) and intercellular CO₂ concentration (Ci) were measured. Results showed that the biomass of A. mongolicus could completely return to pre-stubble level after three years of growth. There was no significant difference (P > 0.05) in relative water content of leaves between stubble and non-stubble, but leaf water potential and water use efficiency (WUE) were significantly different (P < 0.05). The leaf water potential of stubble treatment was significantly higher than that of non-stubble treatment. The diurnal change in the photosynthetic and transpiration rates between these two different treatments presented as typical "twin peak" curves and they showed an obvious "lunch break" phenomenon. The stubble treatment exhibited 15.73%, 15.57%, 13.92% higher Pn, Tr and WUE, than that of non-stubble treatment, respectively. Gs of the stubble treatment was the same as Pn and Tr, but Ci was completely different. This indicated that stubble treatment for A. mongolicus had obvious advantages in growth and physiological characteristics and improved productivity potential.