Studies On Photosynthetic Ecophysiological Characteristics Of Predominate Shrub-grass In Rocky Mountains Of Northern China

This paper takes the Vitex negundo, Commelina communis, Agrimonia pilosa, Setaria viridis, Lespedeza davurica, Artemisia lavandulaefolia, Helianthus tuberosus, Amphicarpaea trisperma and Clematis brevicaudata these nine dominant shrub-grass in different ecological position in rocky mountain area of northern China as the research object, using Li-6400 photosynthesis measuring instrument system to study the dynamic change law of photosynthesis under the special environmental condition. The related mathematical models about the response characteristics of photosynthesis to the light and CO2 were established. The corresponding ecophysiological factors responsible for photosynthesis and transpiration of the nine plant species were analyzed via Stepwise Multi-variable regression methods. The results are as follows:1 The diurnal changes of photosynthetic active radiance of Artemisia lavandulaefolia and Helianthus tuberosus were single peak type in sunny days of their vegetal environment. But the curve of diurnal variation of Lespedeza davurica , Amphicarpaea trisperma, Clematis brevicaudata, Vitex negundo, Commelina communis, Agrimonia pilosa and Setaria viridis leaf photosynthesis showed two peaks. The photosynthetic rate of Amphicarpaea trisperma, Commelina communis and Agrimonia pilosa decline by means of stomatal limitation. But Vitex negundo and Setaria viridis was caused by non-stomatal limitation.2 The AQY of nine plants are Artemisia lavandulaefolia> Vitex negundo > Setaria viridis > Commelina communis > Agrimonia pilosa > Amphicarpaea trisperma > Helianthus tuberosus > Lespedeza davurica > Clematis brevicaudata. The CE of nine plants are Artemisia lavandulaefolia> Helianthus tuberosus > Vitex negundo > Agrimonia pilosa > Setaria viridis > Lespedeza davurica > Commelina communis> Amphicarpaea trisperma.3 Multi-linear regression equations of Pn to ecological and physiological factors were set up. Importances of the factors were arrayed according to partial coefficients in corresponding equations. The sorted order of importance for all factors is: VpdL> Ci> CO2 concentration > Cond> PAR> Tair> RH. So physiological factors may have more direct and significant affects on photosynthetic courses.4 The fluorescent kinetic analysis showed that Artemisia lavandulaefolia, Vitex negundo and Setaria viridis have high photosynthetic capacity and potential. Clematis brevicaudata, Agrimonia pilosa and Amphicarpaea trisperma can use the weak light resource effectively. The adversity stress had little influence on photosynthesis of Helianthus tuberosus and Lespedeza davurica.5 In this research, Vitex negundo, Artemisia lavandulaefolia, Lespedeza davurica and Setaria viridis had rather broad ecological niche for light intensity, air temperature and CO2 concentration. So, they have strong ability of accommodation in the changing environment in the future. The Amphicarpaea trisperma's niche overlapping Clematis brevicaudata' niches are large in the mass which show keen competition for one kind of resource. According to physioecological characters of photosynthesis, the composition of species in different succession stages also changed significantly.