Abstract:In order to investigate the transpiration and water consumption mechanism of orange trees, a typical economic forest tree in dry-hot valley region of Southwest China was taken as object, and the thermal diffusion probe TDP, soil moisture sensor TDR, automatic weather station and canopy analyzer were used to obtain long-term data on transpiration, soil water content, and temperature, radiation, vapor pressure deficit, precipitation and leaf area index. Through a systematic study on the environmental control and physiological regulation of orange transpiration, the results showed that compared with the dry season and rainy season, the dry-hot season showed a more conservative water utilization mechanism, and the daily transpiration, canopy conductivity and decoupling coefficient were significantly lower than those of the other two seasons. In the dry season and rainy season, the transpiration of orange trees was alternately controlled by solar radiation and the vapor pressure deficit, while the transpiration in the dry-hot season was mainly affected by the vapor pressure deficit. There was a time lag effect between the intraday dynamic change characteristics of the canopy conductance and meteorological factors, and this effect varied in different weather and seasons. The vapor pressure deficit was negatively logarithmically correlated with canopy conductance as influenced by the leaf area index, and other environmental factors also were negatively logarithmically correlated with canopy conductance at leaf area indexes less than 4m2/m2 and quadratically correlated at greater than or equal to 4m2/m2. Although the sensitivity of canopy conductance to saturated water vapor pressure difference varied under different environmental conditions, transpiration basically followed the isohydric regulation strategy under most environmental conditions, but there were individual environmental conditions presenting the risk of environmental stress imbalance. The results can provide a direct basis for the diagnosis of environmental stress in orange orchards in the dry-hot valley area, which was conducive to the scientific optimization of irrigation systems and the efficient formulation of water-saving regulation technology system.
