Effects Of Precipitation And Nitrogen Variations On Physiology And Ecological Indicators Of Fraxinus Mandshurica Seedlings In Changbai Mountain Under Different Temperatures Control By Altitudes

Taking Fraxinus mandshurica, a main tree species in the temperate zone of NortheastChina, as test material, two experimental sites were installed at the altitudes740m and1200m in Changbai Mountains, the Simulated soil1.47℃, air temperature is1.98℃. respectively,two nitrogen level incluing+10gN m^-2（+N） and no nitrogen（CK）, and three precipitationregimes incluing30%precipitation enhancement（+W）,30%precipitation deduction（-W）, andnaturally occurring precipitation（CK）,6treatments were designed, incluing CK、+W、-W、+N、+N+W、+N-W. and the photosynthetic parameters, plant growth and the main substanceswere determined. aimed to investigate the effects of the variations in temperature, nitrogenand precipitation on the growth and photosynthesis in Fraxinus mandshurica seedlings, withtheir growth, leaf photosynthetic parameters, leaf soluble protein soluble sugar andphotosynthetic pigment contents examined. The main conclusions were as follows:（1） Temperature variation had significant effects on the growth and photosynthesis of theseedlings. For the seedlings growing at altitude1200m, their stem basal diameter, plant height,and leaf chlorophyll contents, soluble protein contents, leaf net photosynthesis rate, maximalphotosynthetic capacity and apparent quantum efficiency under the six treatments hadsignificant decrease, dark respiration rate had significant increase, as compared with theseedlings growing at altitude1200m. Non-stomatal factors limitation was the main reason forthe decrease of the seedlings photosyntheticcapacity.（2） N addition had significant effects on photosynthetic physiological indicators of theseedlings, soluble protein contents, Nitrate reductase had significant increase. N addition hadinsignificant improving on plant photosynthetic capacity, Moreover, the plant growth hadsignificant promoting effects by N addition.（3） Precipitation variation had significant effects on photosynthesis indicators ofseedlings.30%precipitation enhancement had significant effects on photosynthesis indicators,whereas different Precipitation treatment had lesser effect on the growth. Compared with the response to the precipitation variation of the seedlings growing, the photosynthesis indicatorshad more sensitive.（4） Coupling effect of water and nitrogen had more sensitive on the indicator ofphotosynthetic physiological characteristics of seedlings. Relatively high temperature and Naddition had increased significant effects on seedlings. Precipitation variation had significanteffects on N absorption and using. Whereas, the multiple interaction of the temperature、Naddition and precipitation variation had little effects on Fraxinus mandshurica seedlings.