Abstract: Pinus sylvestris var. mongolica seedlings were collected from three diverse geographic populations, Honghuaerji, Heihe and Mohe of Northeast China. As the study subjects, these seedlings were grown up for four years in greenhouse of Northeast Forestry University under the stress of long-term high-temperature cultivation experiments by artificial control. The effects of long-term extreme high-temperature stress (+15℃, +18℃, +21℃) on plant height, base diameter, root-shoot ratio, biomass allocation and non-structure narbohydrates (NSC) of P.sylvestris var. mongolica seedlings were studied, The degree of P.sylvestris var. mongolica tolerance to high temperature was ascertained. Our results showed that significant differences (P<0.05) was found among the different geographic populations of plant height, base diameter, root-shoot ratio, biomass allocation. Among diverse geographic populations, the largest plant height, base diameter and biomass allocation was found in Heihe population, the lowest was in Mohe population. But the largest root-shoot ratio was in Honghuaerji population, the lowest was in Mohe population. There were significant differences among both soluble carbohydrate and starch of different organs in the same population and different populations of the same organ. The largest proportion of soluble carbohydrate and starch content among the three different populations was in Heihe, and the lowest proportion was in Mohe. Among the different organs, the largest proportion of soluble carbohydrate and starch content was in the foliage, and the lowest proportion was in stem. Our study demonstrated that the P.sylvestris var. mongolica seedings from Heihe showed strong ability to adapt long-term high temperature stress, had stronger physiological basis of resistance to high temperature stress compared with the other two populations, it indicated that P.sylvestris var. mongolica seedlings can adapt the temperature rise in 15℃, while the temperature rise in 20℃ could produce severe stres, which was the ideal P.sylvestris var. mongolica provenance in the future of the global climate warming of Northeast China.

Key words: high-temperature stress, Pinus sylvestris var. mongolica, diverse geographic populations, biomass, non-structure carbohydrates