The Effect of Increasing Soil Temperature on Photosynthetic Characteristics of Syringa reticulata in Alpine Permafrost

In order to promote the growth of Syringa reticulata in the high altitude permafrost areas, this study increased soil temperature artificially through the system of ceramic solar collectors, and set up 4 warming gradients of 2.0 ℃ (S₁), 3.0 ℃ (S₂), 4.0 ℃ (S₃), 5.0 ℃ (S₄), and 1 CK control group, respectively, to analyse the changes of photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO₂ concentration changes under different soil temperatures of S.reticulata's leaves. The results showed that in 4 treatments, the net photosynthetic rate of the group of S₃ andS₄ were larger, and the growth rate was 13.16% and 16.65%, respectively. The transpiration rate and stomatal conductance of S₄ were the largest and the growth rate was 58.89% and 9.17%, respectively. The intercellular CO₂ concentration of S₃, S₄ were the highest, and the growth rate was 14.63% and 20.43%, respectively. It was indicated that soil temperature has a very significant relation with net photosynthetic rate, stomatal conductance and intercellular CO₂ concentration, and soil temperature and the transpiration rate were significantly related. Based on the analysis of the indicators all above, it showed that it was the most appropriate condition for S.reticulata growth to increased soil temperature by 4.0 ℃ to 5.0 ℃.