The Water Physiological Characteristics And Drought Tolerance Of The Major Tree Species In The Eastern Mountain Region Of Northeast China

Severe droughts have been associated with regional-scale forests mortality worldwide. Drought tolerance for tree species would be an important indicator for trees survival. Forests in northeast China playing a vital role in both China’s economic development and ecological environment construction, which in the region of more summer drought intensity and drought frequency, is deserved to be considered for its drought tolerance assessment. This study selected tree species which widely distributed in natural environment, such as Betula platyphylla, Phellodendron amurense, Juglans mandshurica, Fraxinus mandshurica, Quercus mongolica, Ulmus japonica, Larix gmelinii, and Pinus koraiensis in the eastern mountain region of northeast China, measuring water parameters and indexes at early, middle, and late growing season, and try to explore the difference in water physiology of species, and then makes a comprehensive evaluation on drought tolerance of 8 tree species.In different growing seasons, different species showed different characteristics, either PV curve water parameters which represent the cellular level or dehydration rate, water potential, transpiration rate which represent the branches and leaves level. Water adaptive strategy of tree species at different stage of growing season have been explained, and show the diversity of water utilization. The changes ofψtip in the early, middle and late stages of growth were: 2.15 MPa～-1.48 MPa,-1.97 MPa～-1.24 MPa,-2.10 MPa～-1.70 MPa, changes of εmax in the early, middle and late stages of growth were:4.09 MPa～9.56 MPa,4.70 MPa～16.67 MPa, 4.82 MPa～16.14 MPa, which indicates the tree species have certain osmotic adjustment and elastic adjustment ability in each period, and they work together to maintain cell turgor.The seasonal variation of water parameters of tree species in the eastern mountain region of northeast China have been researched, the results show that:water parameters of different tree species varied with the seasons, and water parameters related to phenology rhythm of tree growth and development.The drought tolerance evaluation of main tree species in the eastern mountain area in the early stage of growth, middle stage and late stage were carried out by using different estimation standards. In different growth stages, the drought resistance of tree species is different so as to adapt themselves to the environment. Drought tolerance of species have a certain seasonal variation, on the whole, the drought tolerance of P. koraiensis, L. gmelinii, Q. mongolica, P. amurense are strong, and B. platyphylla, J. mandshurica are in the middle, the drought tolerance of U. japonica, F. mandshuricais are relatively weak.Comprehensive evaluation of drought tolerance in the whole growing season, the results show that:the order of comprehensive drought tolerance was as following:P. koraiensis> L. gmelinii> P. amurense> Q. mongolica> J. mandshurica> B. platyphylla> U. japonica> F. mandshurica. The result is good agreement with the natural distribution of species in the eastern mountain region of northeast China.