Photosynthetic response characteristics and water use efficiency of Haloxylon ammodendron under different stubble treatments

Understanding the photosynthetic characteristics, water use efficiency (WUE) and their differences of Haloxylon ammodendron under different stubble treatments is helpful to understand the adaptation strategies of Haloxylon ammodendron to the environment under different stubble treatments. It provides a theoretical basis for the tending management of shrubs in arid areas and is of great significance for ecological restoration in arid areas.

The light response curves of Haloxylon ammodendron (0%, 25%, 50%, 75%) under different light intensities were measured by Li-6800 portable photosynthesis instrument, and water use efficiency of different stubble Haloxylon ammodendron were analyzed.

In the range of photosynthetically active radiation (PAR)0-2 000 μmol·m^-2·s^-1, the net photosynthetic rate, transpiration rate and stomatal conductance of different stubble Haloxylon ammodendron increased with the increase of photosynthetically active radiation, and the intercellular CO₂ concentration decreased with the increase of photosynthetically active radiation. When photosynthetically active radiation was greater than 600 μmol·m^-2·s^-1, the net photosynthetic rate values showed stubble 75% > stubble 0% > stubble 25% > stubble 50% > no stubble, and the difference was significant (P < 0.05). The light saturation rate (A_max) and light compensation point (LCP) of stubble 75% were the highest, the apparent quantum efficiency (AQY) of stubble 25% was the highest. When the photosynthetically active radiation was less than 600 μmol·m^-2·s^-1, the water use efficiency of different stubble Haloxylon ammodendron increased rapidly. When it was greater than 600 μmol·m^-2·s^-1, it continued to rise slowly with the increase of light intensity. Stubble 25% increased water use efficiency by reducing transpiration rate. The water use efficiency of different stubble Haloxylon ammodendron was stubble 25% > stubble 75% > stubble 50% > no stubble > stubble 0%.

The water use efficiency of stubble 25% is the highest. The most suitable management of Haloxylon ammodendron is stubble 25%. This study reflects that after different degrees of stubble of Haloxylon ammodendron, its own drought resistance mechanism and water regulation strategy are formed in arid environment.