Responds Of Songnen Grassland Photosynthetic Characteristics To Warming And Nitrogen Addition

A profound impact on global climate change in the pattern of warming and nitrogen ecosystem photosynthetic capacity, the long-term continuous simulation of atmospheric temperature and nitrogen deposition experiments predict ecosystem photosynthetic capacity of great significance to future global climate change on grassland ecosystem productivity and carbon deficit. This study is based on the results in Songnen grassland in northeast China set field analog control experiments, the system of our temperate semi-humid and semi-arid grassland ecosystem carbon and water cycle of warming and nitrogen addition. Determination of the Songnen grassland constructive species Leymus chinensis and Phragmites australis photosynthetic characteristics, the determination of photosynthetic characteristics of Leymus chinensis community, and the determination of the constructive species of photosynthetic products. The main conclusions are as follows:(1) The growth of L. chinensis and P. australis are C3plants in Songnen grassland, but not exactly the same, but the impact of climate change on the L. chinensis, and P. australis individual assimilation ability. Warming increased the L. chinensis net photosynthetic rate, stomatal conductance reduced L. chinensis. Warming P. australis net photosynthetic rate, stomatal conductance and transpiration rate, reduces the the P. australis water vapor pressure deficit. Reduces the the L. chinensis photosynthetic rate and stomatal conductance nitrogen application, on the contrary, nitrogen fertilization increased the the reeds net photosynthetic rate, stomatal conductance and transpiration rate. Warming plus nitrogen application significantly reduced the the L. chinensis net photosynthetic rate, stomatal conductance and transpiration rate, improve water use efficiency of raising grass; P. australis of light and ability to influence is not significant. This is mainly because chinensis, P. australis compared to higher net photosynthetic rate, light saturation point of the P. australis is higher in the state of nature, the Songnen grassland daylight quantum intensity can not make the P. australis photosynthetic rate reaches a maximum, Therefore, warming increased significantly improve the photosynthetic rate of the P. australis.(2) in the the four2006-2009growing season, climate change chinensis Community reduced performance is simulated global warming the Songnen grassland net ecosystem CO2exchange (NEE), ecosystem respiration (ER), but had no significant effect on the total ecosystem productivity (GEP). Nitrogen fertilization increased NEE, ER and GEP, but no significant interaction between warming and nitrogen fertilization. Four growing season changes in the ecosystem NEE and soil moisture changes are positively correlated, especially in the early spring, the soil moisture availability is the Songnen grassland decided the main driver of the carbon sink capacity factor. Reduce ecosystem transpiration role (ET) is warming, increased ecosystem respiration (ER) and water use efficiency (WUE); nitrogen treatments stimulate the WUE. Grassland ecosystem carbon fluxes and increased nitrogen deposition is very sensitive to temperature increases, by affect Cingluo moisture available to adjust, carbon, water flux response to global change is by changing the dominant species in the biomes sheep number of grass, the global change in the short term, rapidly changing the Songnen grassland carbon flux.The influence of temperature on soil respiration showed warming of the soil respiration rate increase of19.31%, and nitrogen fertilization of soil respiration to warming nitrogen application together soil respiration increased by12.29%, an increase of16.25%. This may be because and warming stimulates the activity of soil animals and soil microbial activity, soil respiration rate increased. Applied nitrogen to stimulate root growth and therefore increased soil respiration. Compared with the control, warming of the L. chinensis grassland temperature sensitivity increased to32%; nitrogen application the Q10increased16.2%, warming plus nitrogen fertilization on the Q10impact was not significant. The trend of the warming process soil respiration rate decreases with the soil temperature increases. The range is25-35℃, widely distributed and warming plots of soil respiration soil respiration rate higher than that of the control plots. Nitrogen application on soil respiration rate trend is also decreased with increasing temperature, and nitrogen fertilizer to the plots of soil respiration to warming plots magnitude smaller than the variation with temperature. Warming plus nitrogen treatment, soil respiration increased with increasing temperature, and control ground consistent trend.(3) Songnen grassland constructive species of photo synthetic products are not the same response to climate change. Warming increased chlorophyll A, chlorophyll B, carotenoids and total chlorophyll, and warming significantly increased of L. chinensis chlorophyll A and chlorophyll B ratio. N treatment, warming plus nitrogen treatment significantly increased the chlorophyll A, chlorophyll B, carotenoids and total chlorophyll However, due to the significant increase in nitrogen fertilization on chlorophyll B than chlorophyll A nitrogen application reduced of L. chinensis chlorophyll A and chlorophyll B ratio. Warming reduces P. australis of chlorophyll A, chlorophyll B content also reduced chlorophyll A/B, increased the carotenoid content has little effect on total chlorophyll. The nitrogen application P. australis carotenoids significant but reduce the other several Chlorophyll parameters. Warming increased total soluble sugar and sucrose content of L. chinensis, lower fructose content; nitrogen treatment significantly increased the of L. chinensis soluble sugar and fructose content but lower fructose; warming plus nitrogen treatments significantly improve the content of the L. chinensis soluble sugar, fructose and sucrose. Warming significantly reduces P. australis fructose content of soluble sugar and sucrose was not significant. N treatment and warming plus nitrogen treatment does not significantly affect P. australis soluble sugar content of the growing season. Warming significantly reduce nitrogen and phosphorus content of L. chinensis leaves organic carbon content was not significantly nitrogen application significantly improve the nitrogen content of L. chinensis, reduce the phosphorus content. The organic carbon content and phosphorus content had no significant effect. Warming plus nitrogen application significantly increased leaf nitrogen content, and reduced the phosphorus content. The impact of climate change on of L. chinensis C, N and P differences warming or nitrogen applied to change the original C/N ratio of N/P ratio of plant to achieve a new balance of climate change response result is also different. Warming significantly increased the reed leaves organic carbon and phosphorus content, no significant increase in leaf nitrogen content. N treatment and warming plus nitrogen treatment significantly improved P. australis nitrogen, phosphorous and organic carbon content.