Study On Photosynthetic Physiological Ecology Of Main Species Of Closing Land For Forest In Semiarid Loess Hilly Area

Aim at the contradiction of water supplement and growth of vegetation, in the loess hilly region in semi-arid area, with CIRAS-2 portable photosynthesis system made in PPS company of England, response characteristics to light and diurnal change of gas exchange parameters of Platycladus orientalis,Robinia,Acer mono,Syringa sp.,Prunus davidiana,Prunus sibirica L.,Rosa xanthina Lindl.,Caragana korshinskii in three years old were studied under different soil moisture content. The ration connections between soil moisture and the process of photosynthetic physiological were discussed. The results will provide scientific steering function to the choice of species and site disposition in closing land for forest and vegetation reconstruction in the loess hilly region in semi-arid area. The next are the main results: (1)The diurnal change rule of the process of photosynthetic physiological of different trees has the connection with the characteristics of trees and soil moisture. When Wr>65%, the diurnal changes of Pn of Platycladus orientalis Robinia,Acer mono,Syringa sp. Prunus davidiana,Prunus sibirica L. are single peak model, Rosa xanthina Lindl.,Caragana korshinskii are double peak model, the reasons of photosynthetic midday depression are stomatal limitation and nonstomatal limitation. When the range of Wr is 40%~65%, the diurnal changes of Pn of all measuring species are double peak model, the affect factors are different. When Wr<40%, the diurnal changes of Pn of all measuring species are also double peak model. The affect factor of Platycladus orientalis,Syringa sp. ,Prunus davidiana,Rosa xanthina Lindl. is stomatal limitation, others is nonstomatal limitation. These showed that the fitting soil moisture management range of Wr is 40%~65%, out of the range, Pn and WUE will descend obviously. Platycladus orientalis,Syringa sp. ,Prunus davidiana and Rosa xanthina Lindl. have higher ability to resisting high light stress under aridity stress condition. The sequence of the productivity of tolerant to drought of the measuring species is Syringa sp.