Trait Differences Between Invasive And Native Plants And Their Response To Water Flooding Intensity In The Three Gorges Reservoir Riparian Zone

After the impoundment of the Three Gorges Reservoir,with the disappearance of the original Yangtze River natural riparian zone and the interference of human activities,significant changes have occurred in the plant community in the Three Gorges Reservoir area,which also brings new opportunities for the entry of exotic plants.The riparian zone,as the ecotone,has become a hot area for exotic plants to invade.Currently,invasive plants are widely distributed in the Three Gorges Reservoir riparian zone,and the invasion situation is not optimistic.Under the unique hydrological operation mode of the Three Gorges Reservoir,the distribution and characteristics of exotic and native plants in the fluctuation area are strongly influenced by the differential hydrological rhythm.Therefore,through multiple field surveys and sampling analyses from 2021 to2022,this article investigates and studies the species composition and distribution status of invasive plants in the Three Gorges Reservoir riparian zone,and compares the differences in characteristics between invasive plants and native plants at different flood gradients in the Three Gorges Reservoir riparian zone from both community and species levels.To answer two scientific questions,what are invasive plants’ composition and distribution characteristics in the Three Gorges Reservoir riparian zone? What are the differences in the effects of different degrees of flooding stress on invasive plants and native plants? The main research results are as follows:(1)There are 71 species of invasive plants in the Three Gorges Reservoir riparian zone;Among them,Compositae,Amaranthaceae,Solanaceae,Leguminosae,and Gramineae are the dominant families of invasive plants in the Three Gorges Reservoir,with Compositae accounting for 31% of the total number of species;The invasive plants in the riparian zone are mostly annual plants that grow and reproduce quickly,with strong survival ability and good adaptability to the habitat in the riparian zone;The origin is mainly the American continent;The flowering and fruiting period is mostly concentrated in the summer autumn festival(May-October).(2)The most widely distributed species were Bidens frondosa L.,Alternanthera philoxeroides(Mart.)Griseb.,Bidens pilosa L.,Symphyotrichum subulatum(Michx.)G.L.Nesom,Erigeron canadensis L.and Dysphania ambrosioides(Linnaeus)Mosyakin &Clemants,all of which belong to malignant invasive plants,which will cause significant impact and damage to the local ecological environment;There are many invasive plants distributed in the riparian zone in the head and middle of the Three Gorges Reservoir,and the invasive trend of alien plants in the perennial backwater area is relatively serious.Both exotic invasive and native plants had the highest abundance in moderate-intensity flooded communities.(3)There was no significant difference in the functional difference index of various functional traits between invasive plants and native plants at different flood gradients,and the functional traits of plants under flood stress showed a general convergence in the riparian zone,mainly due to environmental filtering effects;The species diversity index and community functional diversity have significant differences under different flooding intensities in the riparian zone,with moderate stress effects.In moderately flooded communities,the plant height traits of invasive plants and native plants tend to converge,with a high degree of convergence.(4)Trait differences between invasive and native plants were influenced by the intensity of flooding,invasive plants were the most invasive in medium intensity flooded communities and the most competitive between invasive and native plants in higher-intensity flooded communities.Within lower and moderate intensity flooding communities,exotic invasive plants are more important than native plants and are more adapted to flooding stress in the riparian zone.The invasive plants have the highest relative importance and the strongest competitiveness;the plant height is the key trait of the invasive plant,and the growth strategy of the invasive plants in the riparian zone is in line with the evolutionary hypothesis of enhanced enhancement.To sum up,under varying degrees of flooding stress in the Three Gorges Reservoir riparian zone,both invasive plants and native plants are strongly affected by flooding stress,mainly due to environmental filtering effects,with certain convergence in functional traits.However,the competitiveness of invasive plants in medium intensity flooded communities is significantly higher than that of native plants,and they are more adaptive to this flooding intensity.At the same time,there are many types of invasive plants in the riparian area,and most of them are malignant invasive plants with high harm.Therefore,it is necessary to increase attention to the issue of alien plant invasion in the riparian area,strengthen research on the mechanism of alien plant invasion in the riparian area,and provide support and assistance for the construction of the ecological restoration system and vegetation management in the reservoir area.