| The Stipa grandis is endemic plant species of typical steppe in Central Asia. Stipa grandis is one of the key community types of Inner Mongolia grassland ecosystem. Zonal Stipa grandis steppe distribute in east part of Xilinhot and middle part of Hulunbuir. Stipa grandis steppe was originally a high quality natural pasture. Animals like to eat the Mowing hay, and are an important winter forage grass. This experiment samples selected in43million mu ecological protection zone of Mao Deng pasture, Xilinhot, Inner Mongolia Autonomous Region. Stipa grandis community characteristics, growth environment, photosynthetic and water use efficiency of characteristics are studied. The results showed as following:(1) No significant difference between community quantities character of perennial mowing and don’t have to mowing Stipa grandis steppe. Mowing disturbance on community characteristics has little effect. This result shows that the annual mowing is better use pattern on Stipa grandis steppe.(2) Significant correlation was found in the growth of peak period of the Stipa grandis steppe between the dry matter yield and soil water status, whether mowing or before it.In this study, the ratio of the amount of water consumed on the production of dry matter and dry matter to determine the size of the plant water use efficiency. Therefore, August ecological water demand is high, but production of dry matter a lot. So water use efficiency is significantly higher. For the semi-arid grasslands, How to improve the efficiency of water use is the key to plant adaptation to arid environments and an important safeguard of coordinated development of regional economy and ecological protection.(3) Under natural conditions, in the two plots (M, NM), Diurnal variation of Stipa grandis’s net photosynthetic rate (Pn), transpiration rate (Tr), water use efficiency (WUE), stomatal conductance (Gs), intercellular CO2concentration (Ci) and other characteristic parameters, some took on a curve with only one peak, some took on a curve with two peaks and showed midday depression of photosynthesis.(4) Under the condition of the different ranges of CO2contents(Cco2), CO2contents in the range (0-1500μmol-mol-1) within net photosynthetic rate, water use efficiency, transpiration rate and stomatal conductance took on a single peak curve, with the increase in Cco2increased. With the increase of CO2concentration, Pn and WUE significantly improved. Tr and Gs, there was a decrease with the increase of Cco2.Photosynthetically active radiation in the range (0-3000μmol·m-2· s-1) within, net photosynthetic rate, water use efficiency, transpiration rate and stomatal conductance took on a single peak curve, with the increase in PAR increased, and then began to decline when PAR increases to a certain value. Too strong light influence on plant photosynthesis, because of the formation of photo inhibition.(5) Under the condition of the different intensities of photosynthesis active radiation (PAR) and different ranges of CO2contents(Cco2), the characteristics of leaf photosynthesis and water physio-ecology of Stipa grandis were studied. The results showed as following:the regressive equation between Pn and (Cco2)was Pn=-1.451+0.032[CO2]-1.379×10-5[CO2]2, CO2compensation point (CCP)was46.27pmol CO2·mol-1CO2saturation point (CSP)was1160.26μmol CO2·mol-1; the regression equation between net photosynthesis rate (Pn) and photosynthesis active radiation (PAR) was Pn=-1.099+0.019PAR-5.461×10-6PAR2, light compensation point (LCP)was58.84μmol·m’2·s-1, the light saturation point (LSP)was1739.61μmol·m-2·s-1。... |
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