| Carex tussock wetland is the one of the important types of herbaceous peat swamp and are also iconic wetland flora landscapes.It has multiple ecological functions such as maintaining biodiversity,providing habitat for rare birds and sequestering carbon,which plays an important role in maintaining regional ecological security and supporting biogeochemical cycles.Due to the combined effects of extreme climate change and human social activities,abnormal fluctuations in wetland hydrology have caused different degrees of degradation and even extinction of Carex tussock wetland in many areas.In this study,the Carex tussock wetland in Momoge national natural reserve in the westen Songnen plain was used as the research object.Through the integration of multidisciplinary theories of physical geography,ecology,hydrology,botany and seed biology,and the combination of literature collection,field observation experiments,indoor simulation experiments and microcosmic simulation experimental methods to analyzed the developmental characteristics of Carex schmidtii seed and spikes in response to hydrological changes,studied the coupling relationship of soil seed bank distribution patterns and ecological characteristics of multi-level C.schmidtii communities,elucidated the developmental characteristics of C.schmidtii seedlings and their physiological and ecological characteristics in response to hydrological changes,revealed the role of hydrological conditions on the sexual reproduction activities of C.schmidtii The mechanism of hydrological conditions on the sexual reproduction activity of C.schmidtii was revealed,and the hydrological control strategy for the suitability of Carex tussock wetlands with sexual reproduction of C.schmidtii have been presented.The conclusion is as below:1.Hydrological conditions have significant effects on the developmental traits of spike of C.schmidtii(number of spikes per plant,number of spikes per tussock,spike length,spike diameter,spike fresh weight,spike dry weight)and seed ecological characteristics(length,width,height,volume,thousand seed weight,capacity)(p<0.05).The response of morphological and structural traits of seed and spike of C.schmidtii to changes in hydrological conditions was consistent during the execution of the experiment,and the best morphological and structural development results of seed and spike of C.schmidtii were concentrated in the wet treatment.The M-H15 treatment effectively promoted the phenotypic structural development of seeds and improved the material accumulation capacity of seeds of C.schmiditii,with the length(2.89 mm),width(1.83 mm),height(0.72 mm),volume(3.81±0.14 mm~3),thousand seed weight(0.72 g)and bulk weight(0.51 kg/L)of the seeds were significantly higher than those of the other hydrological treatments(p<0.05).There was a significant linear correlation(p<0.05)between the developmental traits of spikes and the ecological characteristics of seeds,and a significant positive correlation(p<0.05)between the number of spikes per plant and the number of spikes per tussock,morphological indicators of seed and spike,structural traits of seed and spike,seed height,seed thousand seed weight,and seed capacity.2.Hydrological conditions significantly affected the ecological characteristics of tussock-population-community and the species composition of the soil seed bank(p<0.05).A total of 63 species in 44 genera and 23 families of wetland plants were recorded in the field survey,and C.schmidtii were the dominant species in all hydrological environments.The population density(810.8±27.88 plants/m~2)and cover(71.4±5.78%)of C.schmidtii in sample site M were significantly higher than those in other hydrological conditions(p<0.05),and the morphological development of tussock in sample site M was significantly better than those in other hydrological conditions(p<0.05).A total of 65 species in 42 genera and 26 families of wetland plants were recorded in the soil seed bank,and Comarum palustre and C.schmidtii were the dominant species in the soil seed bank in sample plots D,M and F,respectively.Soil water content and soil bulk density are the key environmental factors driving the variation of ecological characteristics and species composition of the soil seed bank at multiple levels,respectively.The degree of similarity between the species composition of the soil seed bank and the community was low under different hydrological conditions due to the combination of hydrological and environmental factors and plant reproduction strategies.3.Hydrological conditions have significanted effects on seed germination,seedling growth,reserve mobilization,and photosynthetic pigment accumulation of C.schmidtii(p<0.05).The germination peak and vigor index of C.schmidtii seeds were significantly greater under 100%-HT1 treatment and 50%-RT3 treatment conditions than under other hydrological conditions(p<0.05),and the maximum seedling biomass,appeared within the 100%-HT1 treatment under the water fluctuation treatment,while the maximum seedling length,root length,seedling biomass,root biomass,and the total biomass appeared within the 50%-RT3 treatment under drought and re-flooding treatment.The During seed germination,starch,soluble protein,and fat contents was fluctuating decline during the fluction of seed germination of C.schmidtii,while soluble sugar contents continued to accumulate and all showed significant level differences within the early seedling stage(p<0.05),and the maximum soluble sugar contents appeared in 100%-HT1(25.76±2.04 mg/g Fw)and 50%-RT3(31.25 mg/g Fw)treatment groups and their increases were significantly higher than other hydrological conditions(p<0.05).The maximum Chl a:b ratio and carotenoid content were found in the 100%-HT1 treatment with 2.63±0.19 mg/g and 0.25±0.02 mg/g,respectively,under hydrological fluctuation conditions,and the Chl b content,chl content,Chl a:b ratio and car content of seedlings of C.schmidtii were significant differences affected by the AT treatment,RT treatment and their interaction(p<0.05)4.Hydrological conditions drive the developmental activity of seed and spike of C.schmidtii by dual pathways.Hydrological conditions directly influence the developmental traits(number of spikes,spike morphology,spike biomass)and seed ecological characteristics(seed morphology,seed capacity,seed weight)of seed spikes,which regulated by the possible presence of transposon-derived gene homologs in C.schmidtii,and the improvement of tussock substrate driven by hydrological changes provides the nutrient base for spike growth and seed germination of C.schmidtii.Hydrological conditions promoted the synergistic development of multilayered ecological traits of tussock-population-community of C.schmidtii,and the connected hydrological environment provides multiple input channels for structural scale replenishment of the soil seed bank,and there are reciprocal feedbacks between the C.schmidtii community and the soil seed bank under hydrological driving effects.Both Hydrological fluctuation,drought and re-flooding conditions significantly affected the seedling growth process of C.schmidtii.Hydrological conditions contributed to the seedling growth level by affecting the germination quality of C.schmidtii seeds,while hydrological changes also indirectly influenced the seed germination and seedling growth by affecting the reserve mobilization of C.schmidtii seed storage material and photosynthetic pigment accumulation content.5.The organic combination of self-design and design theory,flood pulse theory and invasion theory within the framework of nature-based solution concept is the key scientific basis for achieving ecological restoration of degraded Carex tussock wetlands.For light and moderately degraded Carex tussock wetlands,a staggered water recharge during the initial developmental stage can promote the seed germination and spike growth of C.schmidtii,and the synergistic development of multi-level community ecological components,while for heavily degraded Carex wetlands,microtopography creation,soil seed bank introduction and seed dispersal,and staged hydrological control techniques are recommended in sequence.For potential future extreme hydrologic events,it is recommended to implement targeted drainage programs and strategies to mitigate abiotic stresses caused by extreme flooding and drought events,such as deploying surrounding wetland water bodies,diverting water for winterization,and sowing seeds that priming treatment. |
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