| Due to changes in the natural environment and intensified human activities,global climate change is becoming increasingly significant.Climate change is one of the driving forces for changes in natural ecosystems and has an important impact on the succession of vegetation and soil communities.In recent years,affected by climate change,extreme precipitation events in the arid regions of northwest China have occurred frequently.The spatial and temporal distribution of precipitation has been uneven.And the degree of drought has become severe.The variation of precipitation above has a great impact on the local ecological environment.Grassland ecological conditions in the arid region of Northwest China are fragile and very sensitive to climate change,and changes in precipitation patterns are bound to affect grassland plant community succession and soil nutrient cycling.In order to investigate the impact of precipitation changes on the stoichiometric and photosynthetic characteristics of dominant plants and rhizosphere soils in grassland ecosystems in the arid region in Northwest China,a manipulating precipitation experiment was conducted in Yunwu Mountain,Guyuan city,Ningxia.The self-flow and drip system was set up to construct three precipitation gradients:normal precipitation reduced by 50%(DP),normal precipitation(CK),and normal precipitation increased by 50%(IP).Under different precipitation gradients,three dominant plant species Artemisia sacrorum Ledeb.(AS),Stipa bungeana Trin.(SB)and Potentilla acaulis L.(PA)were selected.The overground and underground parts of the plants were collected to determine total carbon(C),total nitrogen(N),and total phosphorus(P)contents.The rhizosphere soils of three dominant species were collected to determine the content of organic C,total N and total P.The photosynthesis instrument was used to determine the photosynthetic rate,inter-cellular CO2 concentration,stomatal conductance and transpiration rate of the three dominant species.The main results were as follows:(1)Under short-term(two-year)changes in precipitation,there was no significant change in the eco-stoichiometric characteristics of the overground and underground parts of the dominant species of AS,SB,and PA.The eco-stoichiometric characteristics of rhizosphere soils of dominant plant species changed significantly.Organic C,total P,and C/P in rhizosphere soil of AS had significant differences(p<0.05).C/N in rhizosphere soil of SB had significant differences(p<0.05).Organic C,total N,total P,C/N,N/P and C/P in rhizosphere soil of PA had no significant difference.Precipitation changes have no significant effect on the plant's eco-stoichiometric characteristics,but have a significant effect on the rhizosphere soil's eco-stoichiometric characteristics.(2)Photosynthetic characteristics changed significantly under the change of precipitation.Photosynthetic rate,transpiration rate and stomatal conductance of SB,photosynthetic rate,transpiration rate,inter-cellular CO2 concentration and stomatal conductance of PA were significantly different(p<0.05),and photosynthetic characteristics of AS were not significantly different.(3)The eco-stoichiometric characteristics of C,N and P in the overground part of dominant plant species,as well as underground part,were significantly correlated respectively(p<0.05).But there was no correlation between the eco-stoichiometric characteristics of the above-ground part and the underground part.The eco-stoichiometric characteristics of rhizosphere soil C,N and P were significantly correlated(p<0.05),and the eco-stoichiometric characteristics of rhizosphere soil were significantly correlated with those of overground and underground parts of the dominant plant species respectively(p<0.05).Plant photosynthetic rate,transpiration rate,inter-cellular CO2 concentration and stomatal conductance were significantly correlated(p<0.05).The eco-stoichiometric characteristics of overground and underground parts of plants,and of rhizosphere soils were significantly correlated with photosynthetic characteristics of plants respectively(p<0.05).Under different precipitation gradients,the changes in the eco-stoichiometric characteristics of plants and rhizosphere soil and the photosynthetic characteristics of plants are related to each other.(4)The eco-stoichiometric characteristics and photosynthetic characteristics of different plant species responded inconsistently to changes in precipitation,and the coupling relationship between eco-stoichiometric characteristics and photosynthetic characteristics was also inconsistent. |
PDF Full Text Request