Effects of Different Soil Temperature on Photosynthetic Characteristics of Malus transitoria in Alpine Permafrost

With the purpose of promoting the growth of Malus transitoria in high-altitude tundra, the self-adjusting heat tape used to heat soil is employed to execute soil warming test. 4 warming gradients, namely, 2.0 ℃ (S₁), 3.0 ℃ (S₂), 4.0 ℃ (S₃), 5.0 ℃ (S₄) and 1 CK are presented in the test to measure P_n, T_r, G_s as well as C_i of M.transitoria under different temperature gradients. The result is achieved that among the 4 group of experimental objects, the leaves of S₄ enjoy the highest P_n, T_r and C_i with a respective growth rate at 13.88%, 58.55% and 18.42%, S₃ boasts the highest G_s with a growth rate at 8.68%. Besides, the soil temperature is significantly correlated to P_n, G_s as well as C_i of M.transitoria leaves and is correlated to T_r of the plant. Compared with CK, S₄ and S₃ can prominently improve P_n and T_r while S₄, S₃ and S₂ can obviously raise G_s and C_i. After a comprehensive analysis of all indicators, the result is achieved that a raise of 4.0-5.0 ℃ of soil temperature is mostly suitable for M.transitoria to grow.