Effect Of Eutrophication On Defenses Of Submerged Macrophyte Against Herbivores

Subsubmerged plants are important primary producers in shallow lakes and play an important role in maintaining clear water homeostasis.But submerged plants are often fed up by fish,snails and other animals.Pastoral food will affect the growth of submerged plants,resulting in the decline of submerged plant biomass,and serious grazing food will even cause devastating damage to the submerged vegetation.For the damage of grazing food,submerged plants have evolved various traits to resist grazing food.Water eutrophication can affect the ability of submerged plants to resist animal husbandry by changing the physical characteristics of submerged plant species and the nutrient element content of submerged plants.In addition,according to the resource availability hypothesis,under nutrient-rich conditions,the plant community has a fast growth rate,the species with poor resistance to animal husbandry,the community has a low resistance to animal husbandry,and the community is more likely to be fed by animal husbandry.However,there are very few studies on the influence of eutrophication on the anti-grazing resistance of submerged plants,and the law of change with the change of eutrophication gradient is unclear,and the mechanism is unclear.In this background,the determination of grazing animals to grow in different nutrient environment and different kinds of submerged plants of grazing rate,plant trait index,analysis of submerged plant species level and community level resistance ability in the process of eutrophication change trend and mechanism,to the protection and management of lake submerged plant community is of great significance.In this study,by growing submerged plants under different nutrient conditions,Non-selective feeding experiments were used to determine the rate of animal grazing animals(Pomacea canaliculata)to these submerged plants,To analyze the influence of eutrophication on the ability of submerged plants;Selected submerged plant species-rich lakes to collect a variety of submerged plants,Determine the grazing rate of animals(Pomacea canaliculata,grass carp)and the characteristics of each submerged plant,And combining the species composition and relative abundance data of submerged plant communities in different nutrient gradient lakes obtained from field surveys,Calculate the weighted average food resistance of submerged plant community,To assess the impact of eutrophication on the community-level animal grazing resistance of submerged plants,Finally,the effect of eutrophication on the food resistance ability of submerged plants was clarified.The main results obtained are as follows:1.There are significant differences in the ability of submerged plants cultivated under different nutrient water and sediment conditions,and the plant trait analysis results also show that the phosphorus and dry matter content and carbon and nitrogen content ratio in different nutrient treatment groups are significantly different;but there is no significant difference in the ability of submerged plants cultivated under different nutrient sediment conditions.2.The results of non-selective feeding experiments of Pomacea canaliculata and grass carp showed that the resistance to animal herbivory was significantly different among different submerged plants,with the lowest rate and the strongest ability to animal herbivory,the highest rate and the weakest ability against animal herbivory.The analysis of the correlation between plant traits and animal grazing rate showed that plant ash content and animal grazing rate and phenol content.3.The increase in nutrition will lead to a change in the community structure of the submerged plants,and the species structure will change to the dominant plants with high relative growth rate,and the weighted average rate of the submerged plant community decreases,which is contrary to the hypothesis of resource availability.With the increasing nutrient level,the proportion of Myriophyllum verticillatum L biomass in the submerged plant community also increases and gradually becomes the dominant species,and the rate of animal feeding by animals is low,so the submerged plant community shows both high relative growth rate and strong resistance to animal grazing.This paper analyzes the eutrophication on submerged plant species and community level of resistance ability,found that increased nutrition will change submerged plant traits(carbon and nitrogen content ratio,dry material content)to affect its resistance to animal husbandry,submerged plant ability will change with the change of lake nutrition level.This paper can provide scientific support for species selection and lake management in the restoration work of lake submerged plants.