Growth And Response Mechanism Of Carex Schmidtii To Hydrological Fluctuation: Implacation For Wetland Restoration And Management

Carex schmidtii tussock wetland is a very important wetland type and is also the symbolic scenery of marsh wetland,playing vital roles in water conservation and purification and supporting rich biodiversity.In recent years,due to the influence of human activities and climate change?for example drought and extreme rainfall events?,the varying level of degeneration,even the death appeared in C.schmidtii wetlands.This study takes the C.schmidtii in the Momoge natural reserve in Sonhnen Plain as the object.Based on the field survey/laboratory simulation/model extrapolation,analyzed the multilevel ecological features and aspect change of C.schmidtii under different hydrologic conditions according to the systematic thinking,and the response process against hydrologic changes of morphological features/plant structure traits/nutrient content of C.schmidtii have been studied.The responding mechanism against hydrologic changes of C.schmidtii has been illuminated.Structured the structural equation model through the ecological and physiological features of C.schmidtii and varied hydrologic conditions,then the adaptive mechanism against hydrologic changes of the ecologic and physiological features of C.schmidtii was revealed,and the ecological restoration and management strategy for tussock wetlands based on hydrological management have been presented.The conclusion is as below:1.The coverage/plant height and biomass of C.schmidtii in drowned-wet environment are obviously higher than in dry environment,and the trend of increase first then decrease would be presented during the whole growth season.The highest above-biomass of C.schmidtii is 1106.29 g/cm² recorded in drowned-wet environment,which is 29.57%higher than the highest value recorded in dry environment.As time goes by,the importance value of C.schmidtii will decrease,and it will decrease fast in dry environment.The C.schmidtii community possesses rich biodiversity,and species richness?15?17?of the community in drowned-wet environment ranged from 15 to 17.The similarity index between the dry C.schmidtii community and drowned-wet C.schmidtii community will decrease from 55.17%to 30.77%along with the time.2.Both the morphological features?plant height/stem diameter/leaf area/leaf length/leaf width?and plant structure traits?plant dry weight/dry leaf weight/dry matter content/specific leaf area?will be obviously influenced by the hydrologic changes.Both the morphology and plant structure traits of C.schmidtii adapt the early hydrologic change.In the end of growth stage,the height and leaf area of C.schmidtii under DW0AW0 treatment are 69.4 cm and 10.02 cm²,respectively,which are significantly higher than other treatments.The growth of C.schmidtii is restrained by the long-time drought treatment,and the influence on the C.schmidtii morphology due to the long-time drought can be relieved by drought-wet treatments?DF30,DF40,DF60?.Along with that the C.schmidtii adapt to the drought-drowned environment,the function of plant and leaf of C.schmidtii can be recovered,and the matter content of plant dry weight start to increase.3.The hydrologic change has obvious influence on nutrient content of C.schmidtii.The highest N content were recorded in DW0AW0 treatment with a range of 13.91 to17.97 mg g^-1.As the initial water level increasing,plant N content,K content and K:P ratio decrease obviously.The K content of C.schmidtii under DW0 treatment is 10.69mg g^-1,which is 20.18%higher than DW5 treatment and 26.45%higher than DW10treatment.The N:K ratio of C.schmidtii is promoted by the water-level amplitude,but the K:P ratio of plant is decreased.After drought-flooding treatment,all the nutrient element content of C.schmidtii will get a recovery.The N and K contents of C.schmidtii first decrease before increase to high values.4.All the photosynthetic traits of C.schmidtii?chlorophyll content/chlorophyll a content/chlorophyll b content/chlorophyll a:b ratio/carotenoid content/max photosynthetic rate/actual photosynthetic rate/photochemical quenching/non photochemical quenching?are influenced by the hydrologic change.The highest chlorophyll content and max photosynthetic rate and actual photosynthetic rate of C.schmidtii were found in DW0AW0 treatment with a value of 2.36 mg g^-1,0.756 and0.581,respectively.Both the chlorophyll and photosynthetic parameter of C.schmidtii will efficiently be recovered by the drought-flooding treatments.The chlorophyll content of C.schmidtii under DF60 treatment recoveries to 2.42 mg g^-1.The max photosynthetic rate of C.schmidtii ranges from 0.759 to 0.779,and there no significant differences among drought-flooding treatments.In the end of experiment,the actual photosynthetic rate of C.schmidtii of DF30,DF40 and DF60 were 97.35%,72.00%and 90.47%of W treatment.5.The internal of the following eco-physiological indicators of C.schmidtii,like morphology/biomass/nutrient element and photosynthesis,have relative dependency.The first principle component of morphology indicator is closely related to height,stem diameter and leaf area of C.schmidtii.The first principle component of plant strcture traits is closely related to plant mass,leaf mass,leaf dry matter content and specific leaf area of C.schmidtii.The first principle component of nutrient element indicator is closely related to K content,K:P ratio,N:K ratio and N content of C.schmidtii.The first principle component of photosynthesis is closely related to the max photosynthetic rate and actual photosynthetic rate of C.schmidtii.Both the principle component of morphology indicator and principal component of nutrient element indicator are influenced mainly by the initial water level and the treatment time.Both of the principal component of plant dry weight and leaf structure character and the principal component of photosynthesis are influenced mainly by the treatment time.During the responding process of physiological and ecological characteristics of C.schmidtii,the phenotypic plasticity of C.schmidtii will become the important hub to connect other physiological and ecological indicators.The mutual connection in the indicator system of C.schmidtii plays the critical role in the coordination response process of the C.schmidtii against the hydrologic changes.The internal adjustment of C.schmidtii can keep the stability of internal environment,which is an effective protection mechanism.6.The protection and management of tussock wetlands are more important.Tussock wetlands can be efficiently by combining the making use of natural recovery and artificial hydrologic adjustment.For the degradation area of C.schmidtii tussock wetland,the degradative status should be reasonably identified.For the degradation area of C.schmidtii tussock wetland,the degradative status should be reasonably identified.When protection and management measurements are applied to the C.schmidtii tussock wetland,the propagule quantity of C.schmidtii can be increased by artificial transplant,and hydrologic adjustment in the following period will be contributed to the recovery of tussock wetlands.When ths soil water content is below30%,hydrological management is conducted to make the soil water content reach more than 40%.