长期放牧荒漠草原6种优势植物的光合气体交换特征OA

The desert steppe of Inner Mongolia constitutes an important ecological barrier in northern China.Understanding the photosynthetic efficiency of dominant species and their response to long-term dif-ferent grazing intensities is of great significance for elucidating how this ecosystem adapts to human activi-ties and climate change.This study was conducted in the Stipa breviflora desert steppe with a 20-year graz-ing history.Net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),and intercel-lular CO2 concentration(Ci)were measured for six dominant plant species under four different grazing inten-sities.The results showed that:(1)among the six dominant species in the desert steppe,Convolvulus ammannii exhibited the highest Pn,Gs,and Tr.Regarding the overall effect of grazing intensity,the val-ues of Pn,Gs,Tr,and Ci under light grazing treatment were significantly higher than those under heavy grazing(P<0.05),showing a pattern of stimulation under low grazing intensity and impairment under high grazing intensity;(2)From the perspective of plant photosynthetic pathway,C4 species generally showed higher Pn,Gs,and Tr than C3 species,indicating that C4 plants have stronger photosynthetic capacity and greater environmental adaptability in the desert steppe ecosystem;(3)In terms of different life forms,forbs had the highest Pn,Gs,and Tr,while subshrubs had the lowest.Moreover,as grazing intensity increased,forbs remained relatively stable,showing stronger grazing tolerance,whereas subshrubs exhib-ited greater fluctuations and were more sensitive to changes in grazing intensity.In summary,among the six dominant species in the desert steppe,C.ammannii has exhibited the strongest photosynthetic capac-ity.Grazing intensity,photosynthetic pathway,and life forms jointly shaped the adaptive strategies of dominant species in response to grazing disturbance in the desert steppe.