Effects Of Regional Climate Conditions Change On Photosynthesis Of Dominant Plants In Plateau Wetland

Climate change has a huge impact on the global ecosystem.Yunnan plateau wetland is an important part of the plateau wetland in China.Compared with other ecosystems,the plateau wetland is more sensitive to climate change,and global warming has a more severe impact on it.As the primary producer,the plant in plateau wetland is the basis for maintaining the normal functioning of the whole plateau wetland ecosystem,and the most intense part to the affect.This study using the unique attitudinal topography and climate in Yunnan Plateau,we selected the world widely-distributed plants Schoenoplectus tabermamontani and Zizania caduciflora in Napahai,a representative plateau wetland in Northwest Yunnan province.These two plants together with their growing soil units in situ were respectively moved to Lashihai wetland and Dianchi watershed in Kunming where their altitude are gradually decreasing,to analyze the impacts on the photosynthesis of these two plants during their growth cycles along with differences in regional climatic conditions caused by attitudinal decline.The results showed that:1.Along with the change of regional climate conditions and climatic factors caused by the decline of altitude gradient.Along the Napahai,Lashihai and Dianchi basin,the air temperature and the air CO₂ concentrations gradually increased,and the solar radiation gradually decreased and their regularity of changes were obvio us,although the rainfall and relative humidity also changed,but its regularity of change was not obvious.Among these climatic factors,some were the major influencing factors and some were not the major influencing factors.Through the correlation analysis showed that the air temperature,solar radiation and air CO₂ concentration were the major influencing factors,while the rainfall and relative humidity were not the major influencing factors.Moreover,among these several major influencing factors,the air temperature had the highest correlation with these indices,so the air temperature was the most important climatic factor to affect wetland plant growth.2.Along with the altitude decline,the air temperature gradually increased.After moving to the Lashihai wetland and Dianchi basin,compared with that in Napahai where they were transplanted,in the stage of plant germination,the content of chlorophy?a,chlorophy?b,total chlorophy?and chlorophy?a/b of Schoenoplectus tabermamontani increased 10.2%and 50.5%,8.66%and 23.47%,22.54%and68.77%,1.42%and 21.91%respectively,the content of chlorophy?a,chlorophy?b,total chlorophy?and chlorophy?a/b of Zizania caduciflora increased 45.19%and87.88%,16.77%and 35.06%,11.17%and 29.2%,12.99%and 26.4%respectively.The changes of chlorophy?content of Schoenoplectus tabermamontani and Zizania caduciflora in the growing and aging stages had the similar variation tendency as the germination,but the increase amplitude of indexes during the growing stage were higher than the germination,while the increase amplitude of indexes during the aging stage were lower than the germination.3.Along with the altitude decline,the air temperature gradually increased.During the stage of plant germination,compared with that in Napahai where they were transplanted,the value of Fv/Fm of Schoenoplectus tabermamontani which was moved to Lashihai and Dianchi basin increased by 1.99%and 5.98%respectively,the value of PhiPS?increased by 36.65%and 95.78%respectively,the value of ETR increased by 36.71%and 96.17%respectively,the value of qP increased by 32.17%and 67.55%respectively,while the value of NPQ decreased by17.13%and 59.1%respectively;the value of Fv/Fm of Zizania caduciflora increased by 9.4%and 12.06%respectively,the value of PhiPS?increased by43.52%and 87.29%respectively,the value of ETR increased by 42.71%and87.12%respectively,the value of qP increased by 23.59%and 51.47%respectively,and the value of NPQ decreased by 19.28%and 34.09%respectively.The chlorophy?fluorescence parameters of two plants in the growing and aging stages also increased with the decrease of altitude and the increase of temperature,however the growth rates or the decline rates of these values during the growing stage were higher than that of the germination stage,and the aging stage were lower than that o f the germination stage.4.Along with the altitude decline,the air temperature gradually increased.During the stage of plant germination,Schoenoplectus tabermamontani and Zizania caduciflora which were moved to Lashihai and Dianchi basin compared with that in Napahai where they were transplanted,the PhiPS?_maxax of Schoenoplectus tabermamontani increased 13.96%and 24.09%respectively,the PhiCO_2maxmax increased 89.87%and 114.77%respectively,the PhiPS?_maxax of Zizania caduciflora increased 25.42%and 46.48%respectively,the PhiCO_2maxmax increased 27.08%and84.33%respectively.The changes of these two parameters of the growing and the aging stages of the two plants also showed an upward tendency,which were the same as the germination stage.The dissimilar was that the increase amplitude of PhiPS?_maxax and PhiCO_2maxmax during the growing stage of two plants were higher than that of the germination stage and such change was significant,while the increase amplitude of these values during the aging stage were lower than that of the germination stage.5.Along with the altitude decline,the air temperature gradually increased.Compared with that in Napahai where they were transplanted,during the stage of plant germination,the plant height of Schoenoplectus tabermamontani which was moved to Lashihai and Dianchi basin increased by 12.05%and 42.17%,and the plant height of Zizania caduciflora increased by 19.1%and 62.69%,the difference in plant height was significant.The stem diameter of Schoenoplectus tabermamontani increased by 2.89%and 4.74%,the stem diameter of Zizania caduciflora increased by 4.64%and 14.99%,the difference in stem diameter growth was not significant.The ratio of stem diameter to plant height was 2 to 3 times higher than that of healthy wetland plants under norma l growth conditions.The incongruous growth of this palnt height and stem diameter will laed to the stem to be not strong enough and prone to lodging.In addition,along with the altitude decline,the biomass of Schoenoplectus tabermamontani increased by 39.49%and 98.27%,the biomass of Zizania caduciflora increased by 47.19%and 146.49%.The plant height,stem diameter,and biomass of the two plants had the same change regularity as the germination period during the growth and the litter stages,but the growth rates during the growing stage were higher than that of the germination stage and such change was significant,while the growth rates of these indexes during the aging stage were lower than that of the germination stage.6.The changes in chlorophyll fluorescence characteristics and growth indicators of the two plants during the growth cycle indicate that,in the same period,except for NPQ,the change of these indexes were Dianchi basin>Lashihai>Napahai,this is because the Dianchi basin had better temperature conditions than the other two studies.While in the different periods,the changes of these indicators were growing stage>germination stage>aging stage,the reason was that the growing stage was in the best period of rain and heat in Yunnan,a nd it had better temperature conditions than the other two stages.And further research found,the increase in plant height,stem diameter,biomass and chlorophyll content of Zizania caduciflora was greater than that of Schoenoplectus tabermamontani in the growth cycle,also the gap of increase or decrease between regions of the chlorophy?fluorescence parameters of Zizania caducifera was less than that of Schoenoplectus tabermamontani in the growth cycle.Therefore,overall,Zizania caducifera had a stronger ability to adapt to the rised of temperature caused by the drop in altitude.