The Comparison Of Drought-resistant Eco-physiological Characteristics Between Pinus Densiflora Var. Zhangwuensis And Pinus Sylvestris Var. Mongolica At Different Growth Stages

Through pot experiment in different moisture gradient and field investigation, MDA, catalase, chlorophyll, proline, and leaf water content of the 4-year-old Pinus densiflora var. zhangwuensis and Pinus sylvestris var. mongolica were measured, and individual photosynthetic, physiological indicators of water, biomass, micro-climate conditions, soil moisture and nutrient status of 16-year-old mature stands were measured and investigated. Simultaneous with determination of the physical indicators, cut branch transpiration method was used to define stomatal and cuticular transpiration and evaluate the sensitivity of stomatal opening and closing.The results showed that: in different water gradient, MDA contents of Pinus densiflora var. zhangwuensis seedlings were less than those of Pinus sylvestris var. mongolica, and both catalase and proline contents of the former were higher than the latter. MDA, catalase and proline contents of Pinus densiflora var. zhangwuensis from CK (100% FMC) to A stage (40% FMC) decreased, from A stage-B stage (30% FMC) began increasing, and reached the maximum during C stage( 20% FMC). These three physiological indicators of Pinus sylvestris var. mongolica had increased during A stage, and reached the maximum during C stage. At different moisture gradient, both chlorophyll and leaf water contents of Pinus densiflora var. zhangwuensis were more than those of Pinus sylvestris var. mongolica, and these two indicators in the same species changed in the same trend, which is : CK> A> B> C. The results of mature forest survey showed that Pn and water use efficiency(WUE)of Pinus densiflora var. zhangwuensis were bigger than those of Pinus sylvestris var. mongolica. In the same habitat conditions, transpiration intensity of Pinus densiflora var. zhangwuensis was smaller than that of Pinus sylvestris var. mongolica. From June to August, the daily transpiration rates(Tr) of Pinus densiflora var. zhangwuensis were doublet. The correlation degree between rhizosphere soil water content and Tr of these two species was the highest,and rhizosphere soil water content was the main environmental factor that influcing Tr,another important factor was mean wind velocity. Stomatal conductance(Gs) of Pinus sylvestris var. mongolica was bigger than that of Pinus densiflora var. zhangwuensis at random measured time, and the average of the former was 1.9 times of the latter.The smaller Gs of Pinus densiflora var. zhangwuensis may be direct cause of its smaller Tr.The stomatal and cuticular Tr of Pinus densiflora var. zhangwuensis were smaller which made this tree species be able to adapt to a stronger long-term drought stress environment, and in the same drought conditions, the sensitivity of stomatal opening and closing of it was higher. Pinus densiflora var. zhangwuensis had deeper root system and greater biomass of tree layer. The humidity was highest and temperature was smallest, and small variation on temperature and humidity turned out, at the same time wind speed, light intensity and water surface evaporation were considerably smaller in mature stand of Pinus densiflora var. zhangwuensis. The soil water, nitrogen and phosphate content of the Pinus densiflora var. zhangwuensis forest was higher than those of Pinus sylvestris var. mongolica forests and vacant land in the growing season.In this paper the extention status of Pinus densiflora var. zhangwuensis in the three north areas of China was also summited. By investigating the growth potential of Pinus densiflora var. zhangwuensis in the extention domins, we found this tree species could grow healthily in Liaoning, Heilongjiang, Shanxi, Shaanxi and Gansu provinces and the south-eastern edge of Inner Mongolia Autonomous Region, indicating the drought-resistant adaptive areas of this tree species should be expanded to most areas in three north areas.