| Shengjin Lake is a typical shallow-water lake connected to the Yangtze River.The flooding and drying zone induced by the seasonal water level fluctuation of the Yangtze River,an ecosystem adapted to the Hydrological situation of lakes connected to the Yangtze River.has been formed by Shengjin Lake.Wetland vegetation play an important role in maintaining the structural stability of ecosystems.In the process of long time natural selection,wetland vegetation adopted special survival strategies to fit water level fluctuation conditions.At present,the studies of wetland vegetation which grow in different habitats are relatively weak.Therefore,research on population regeneration characteristics of dominant species which grow in different habitats is a great significance to investigate community succession and provide scientific basis for revegetation.This paper takes the dominant species Carex thunbergii as the object and use the methods of field investigation and indoor experiments to examine how C.thunbergii growth response to different habitats and allelopathy effect,investigated the the dominance of C.thunbergii in Shengjin Lake.The results as follows:1.There was a significant seasonal dynamics in biomass and antioxidant activity of C.thunbergii which grow in different elevations during October,November,December of flood period end and March,April,may of next year.It was found that a significant effect on biomass and elevations gadient effect with root-shoot ratio of C.thunbergii.The order of root-shoot ratio was low elevations>middle elevations>high elevations.The root-shoot ratio of C.thunbergii.at low elevations increased by 82.66%,4.21%,24.79%,9.21%,28.81%,21.83%,27.43%,44.31% and 22.69% compared with middle elevations,while increased by 39.69%,159.29%,52.78%,47.13%,103.25%,92.49%,69.99%,138.70% and 18.64% compared with high elevations.With the decrease of elevations,the root biomass of C.thunbergii was increased and the shoot biomass was decreased.2.Our results show that C.thunbergii has inhibition effect of seed germination and seedling growth of three accompanying Poaceae species,Lolium perenne,Cynodon dactylon and Phalaris arundinacea.It was found that the extracts of C.thunbergii significantly inhibited the germination rate,germination potential,radicle length and germ length of the three tested grass species.Inhibition of seed germination rate was >95% at the highest extract concentration,for all three tested grasses.At the same concentration,a methanol extract of C.thunbergii had more inhibitory effect than an aqueous extract.The seedling growth was significantly affected by C.thunbergii extracts,and the root-leaf ratio was significantly lower than for control seedlings.Levels of malondialdehyde in L.perenne and P.arundinacea increased with the concentration of extract.Our findings indicate that allelopathy may play a role in the dominance of C.thunbergii in Shengjin Lake.3.According to the study of seedling establishment between C.thunbergii and P.arundinacea,water level had a significant effect on the plant height,root biomass and root parameters of the study species.The two species exhibits different growth strategy under water level and leaf litter.With the increase of water level,the root parameters of the two species decreased,the plant height of C.thunbergii.decreased significantly,while the plant height,specific leaf area,specific root length and root density of P.arundinacea has no significant change.The root biomass and root-shoot biomass of P.arundinacea decreaseed significantly,while biomass of C.thunbergii has no significant change with water level rises.At the same water level,the root biomass of P.arundinacea at litter group were higher than no litter group,and showed significant differences with low water level group.4.With water level increasing,initial fluorescence yield and maximum fluorescence yield at no litter treatment of C.thunbergii decreased significantly under water level and leaf litter of C.thunbergii.The results show that PSⅡ potential activation,photosynthetic electron transport activity,photochemical quenching,non-photochemical quenching and electron transport rate was no significant change.The antioxidant activity and malondialdehyde of the two study species exhibited different response as water level and litter,The malondialdehyde of the two species was positively associated with the water level,the malondialdehyde of root was higher than shoot.It indicates that submergence on root had more stress than shoot.The malondialdehyde of P.arundinacea on root was higher than C.thunbergii,it shows that C.thunbergii has a greater tolerance to the flood stress on root.5.The effects of different plant,water level and litter treatment on soil nutrition were different,Water level has a significant effect on soil total nitrogen,phosphatase and protease,the interaction of plant,water level and litter has a extremely significant effect on soil phosphatase.The high water level increased soil total nitrogen and organic matter,the total phosphorus were all significantly lower than control group.The NaHCO3-P was the most components of soil phosphorus type,the absorbability of C.thunbergii and P.arundinacea are different to soil phosphorus.The soil phosphatase at low water level treatment were lower than control group,while increased at soil protease.The results suggest that the response to water level and litter varies between different soil enzymatic.In conclusion,The C.thunbergii had low root biomass consumptions under flooded conditions,it showed strong ability to tolerate flood and recover growth.While P.arundinacea was more sensitive to water level change and it stored little energy in the root.In all,the adaptation ability of C.thunbergii to submergence stress was better than P.arundinacea under the same conditions. |
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