Study On Plant Functional Traits And Their Environmental Adaptation In The Hydro- Fluctuation Belt Of The Three Gorges Reservoir

Plant functional traits,the units within functional classification schemes,can be defined as groups of plant species sharing similar functioning at the organismic level,similar responses to environmental factors and/or similar roles in(or effects on)ecosystems or biomes,including any morphological,physiological,or phenological feature that can be measured at the individual level(from the cell to the organism as a whole).The three gorges reservoir area has a special water transfer mechanism.The water was stored in the winter and be drained in summer.There's a 30-meter drop in the riparian zone.The riparian has become a new wetland ecosystem with anti-seasonal flooding,which is different from the original ecosystem.The original animals and plants will degenerate or decline,because of their inadaptation of survival condition' s change.Then,new species will replace,who adapted to flood and adversity conditions.The main stream,tributaries and islands of the Three Gorges Reservoir from Jiangjin,Chongqing to Yichang,Hubei are selected as the survey area.We analyzed plant functional traits in several major communities and species,from 17 sample sites in the reservoir hydro-fluctuation belt.We will establish a detailed database of typical plant functional traits in the riparian zone of the Three Gorges Reservoir area and expound the variation of functional traits,during the transformation from riparian zone to hydrofluctuation belt.We want to explain the plant adaptive mechanism for different flooding time and depth,by studying the relationship between Water gradient and functional traits,and to expound the trade-off between different functional traits,put forward the ecological restoration and protection measures based on plant functional traits.The research results are as following:1.Functional traits of plant communities are homogeneous along the river gradient.The coefficient of variability of plant functional traits are big.The coefficient of variability of specific root length,leaf water content,stem water content and specific leaf weight was greater than 1.The variation coefficient of main stem mass was the smallest,greater than 50%.The data of whole area index shows high dispersion.The plant functional traits in the main stream increased along the river flow.The functional traits of the surveyed sections of the 3 tributaries are similar to those of the adjacent Yangtze river trunk stream.The 8 traits showed the same characteristics.That is,narrow quartile distance,little difference between mean and median,more outliers,and concentrated in the larger side.The character data has strong dispersion.The difference of plant functional traits along the river flow was not significant.The composition of plant communities in different sections was similar,and the plant communities in the fluctuation zone of the reservoir showed high homogeneity.2.The functional traits of plant communities show the different characteristics under water-flooded gradients.The traits,like plant height,main stem dry matter content and chlorophyll content,increased with the elevation.Root length/plant height and leaf water content decreased with the increase of altitude,and root length/plant height was negatively correlated with altitude,with significant differences among different elevations(P<0.05).Stem moisture content and leaf thickness increases with altitude and down after rising first,appeared a peak in elevation ? places.The dry matter content of main stem and root length/plant height first increased and then decreased in the study area,And reached the maximum at elevation ?.Along the elevation gradient,high temperature and drought had become new limiting factors.At the altitude of 170-175 m,plants increasing the input of tissue construction for adaptation to the stress of high temperature and drought.3.Different kinds of species have different plant traits.They will occupy the appropriate ecological niche by different adaptation strategies.Plant functional traits were significantly different among the 9 typical species.Plants of Gramineae,such as Cynodon dactylon,Echinochloa crusgalli and Setaria viridis,have strong tillering ability and can be propagated by asexual propagation.They have larger root lengths and are more efficient at absorbing and circulating water and nutrients,increasing growth rates and completing life cycles faster.Water and nutrients can be absorbed and circulated more effectively because of their larger specific root length,the growth rate will be increased and the life cycle will be accelerated.The ecological niche in the lower part of the fluctuation zone will be occupied in a very short initial exposure time.The plant adaptations can also be adapted to other ecological environments,so Gramineae plants are widely distributed in the world.Eclipta prostrata that also occupies a low elevation niches are typical hygrophytes.Water content is significantly higher than other species and the main stem dry matter,leaf dry matter,plant height and chlorophyll content are significantly lower than others.The habitat of hygrophytes is usually near the water.They are short plants with undeveloped mechanical tissue and maintain their upright position by high water content.E.prostrata are highly specific and highly dependent on water.Therefore,species with limited resources and slow growth have lower specific leaf area,while plants with high specific leaf area have stronger ability to maintain internal nutrition.4.In this study,chlorophyll content was positively correlated with leaf thickness,root length/plant height,leaf water content,stem water content and root water content.In other words,the plants with higher chlorophyll content have thicker leaves,larger root proportion and more water storage in the plants.The chlorophyll content is significantly negatively correlated with the amount of leaf dry matter,specific root length,and the amount of main stem dry matter.In other words,such plants invest a large amount of energy in tissue construction to improve their own stress resistance,rather than rapidly growing and completing the life cycle by improving the turnover rate.The correlation with other environmental factors was not significant.Leaf dry matter content was positively correlated with the amount of stem dry matter(P<0.05),and negatively correlated with specific leaf area,root length/plant height,and specific root length(P<0.05).The correlation between plant functional traits is universal in biology,which results from the combination of the developmental mechanism of species and the basic adaptive relationship.Leaf dry matter content was significantly positively correlated with specific root length and main stem dry matter content.These plants invest a lot of energy in tissue construction to improve their resistance to stress,instead of increasing the turnover rate to achieve rapid growth and complete life cycle.The correlation with other environmental factors was not significant.There was a significant negative correlation between leaf dry matter content and specific leaf area and root length,which reflected the trade-off between accelerated nutrient turnover rate and input tissue construction.