The Stoichiometry Of Carbon,nitrogen And Phosphorus In Soil And Plants In Wetland Of Caohai Lake In Guizhou

Ecological stoichiometry is the study of relationships between organisms and their environment through the lens of energy and elemental balance.Carbon(C),nitrogen(N)and phosphorus(P)are important elements for plant growth,and are also key indicators for judging soil fertility and soil quality.The physical properties of wetland soil and the types and structures of surface plant communities are affected by wetland hydrology.With the development of social economy,human activities in Caohai Wetland in Guizhou,such as tourism development,reclamation of lakes and direct discharge of domestic sewage from villages and towns,have caused the Caohai wetland ecosystem to degenerate.In order to restore the integrity of the Caohai wetland ecosystem,relevant departments have proposed measures such as the construction of sluice gates and ecological water replenishment.However,with the implementation of relevant measures,it is not clear whether the storage function of carbon,nitrogen and phosphorus in Caohai wetland has been improved.However,ecological stoichiometry is an emerging discipline mainly used to study the balance of various chemical elements(mainly C,N and P)and energy balance in ecological processes,which is an effective means to reveal the dynamics of plant populations,the determination of restrictive elements,and the element biogeochemical cycle.The soils and plants were collected along a water gradient in 25 sampling sites in Caohai wetland of Guizhou Province in early August 2017,including agriculturalareas,transition areas,shallow-water areas and deep-water areas.The soil and plant total organic carbon(TOC),total nitrogen(TN),total phosphorous(TP)and their ecological stoichiometry in different water levels were measured to investigate the influence of hydrological conditions on plant population dynamics and the storage functions of carbon,nitrogen and phosphorus in Caohai Wetland.As well as,these data can be used as the basis for the hydrological control of Caohai Wetland.The main conclusions of the study are as follows:1)The highest concentrations of soil organic carbon(TOC),total nitrogen(TN),carbon-to-phosphorus ratio(C/P)and nitrogen-to-phosphorus ratio(N/P)was observed in the deep-water areas of Caohai wetland,and the highest concentrations of soil the total phosphorus(TP)was observed in agricultural areas of Caohai wetland,while the highest of the carbon-to-nitrogen ratio(C / N)was observed in shallow-water areas of Caohai wetland.In addition,the concentrations of TOC?TN?C/P and N/P gradually increased from the transition areas to the Deep-water areas.Meanwhile,the difference of TP and C/N among transition areas,shallow-water areas and deep-water areas were not significant(P>0.05).2)The succession of plants increased from the emergent plants to the submerged plants(reverse succession)along the water depth in Caohai Wetland.Emergent plant communities with the water depth of 10-82 cm were dominated by Juncus effusus,Phragmites communis,Paspalum scrobiculatum,Scirpus yagara,and Scirpus triqueter,while the community with the water depth of 89-132 cmwas dominated by Schoenoplectus tabernaemontani and Typha angustifolia,and the submerged plants with the water depth of 193-282 cm was dominated by Potamogeton lucens,Potamogeton maackianus and Myriophyllum spicatum.3)The TOC,C/N and C/P of different living plants in Caohai Wetland was as follows: Emergent plants> Submerged plants,and the Juncus effusus has the highest TOC,C/N and C/P ratios;while TN,TP and N/P are respectively:Emergent plants < Submerged plants,the concentration of TN and TP was the highest in Potamogeton lucens,while the N/P was the highest in Myriophyllum spicatum.4)The water depth was closely related to the spatial distribution of soil TOC,TN,N/P or C/P ratio in Caohai Wetland,but not significantly related to TP or C/N.In addition,the water depth was also closely related to the plant TOC,TN,TP,C/N or C/P ratio,but the correlation with N/P is not significant.5)In conclusion,on the one hand,the succession law of wetland plants will be from the emergent plants to the submerged plants(reverse succession)when the water level rising in Caohai Wetland;on the other hand,as the water level rising,the accumulation of soil carbon and nitrogen will be enhanced,but the total soil phosphorus content had no obvious changes among transition areas,shallow-water areas and deep-water areas.However,high P could be released from dried sediments on rewetting,so there may be a risk of release of phosphorus in Agricultural areas when the water level rises.