Study On Plant Ecological Stoichiometry In The Riparian Zone Of The Three Gorges Reservoir

The riparian zones of the Three Gorges Reservoir is an artificial water-frozen belt formed by the high water level?175 m?water storage in the winter after the completion of the Three Gorges Dam,and it has certain ecological fragility.Ecological chemometrics combines the basic principles of biology,chemistry,and physics to study the energy balance of biological systems and the balance of multiple chemical elements?mainly C,N,P?.The characteristics of plant community evolution,the response of vegetation to the environmental change of the riparian zone,and the adaptation mechanism of the suitable plant in the riparian zone are the central theme in the study of the decline zone of the Three Gorges Reservoir.However,the research on the biochemical characteristics of plant ecology is relatively lacking.In this study,plant communities and individual were used as the target,and the C,N,P,K and their measurement ratios in the riparian zone of the Three Gorges Reservoir were studied,as well as the distribution of vertical watershed scale and lateral flooding gradient.Analyzes:The effects of flooding and different flooding gradients on the ecological stoichiometric characteristics of plant communities,the spatial regularity of plant ecological stoichiometry in the vertical watershed scale,and the various organs in typical plants of the riparian zone are analyzed.The controlling factors and formation mechanism of the ecological stoichiometry of plant communities in the riparian zone of the Three Gorges Reservoir were discussed.The results show that:1)The C content of plant communities in the riparian zone of the Three Gorges Reservoir is 362.68⁴39.79 g?kg^-1,the N content range is4.64³4.40g?kg^-1,and the P content range is 1.01⁵.80g?kg^-1,K content range is 10.09³8.17g?kg^-1;C/N range is 10.91⁹0.20,C/P range is 64.21⁴34.43,N/P range is1.38⁹.89.The cumulative ability of herb community C in the riparian zone of the Three Gorges Reservoir is comparable to that of wetland plants,but not as good as forest plants,and lower than the global plant C content.Plant community N is similar to the N content in the aboveground part of wetland plants,but lower than the N content in Chinese forest ecosystems,terrestrial plants and global terrestrial plants.The P content is much higher than that of wetland ecosystems,forest ecosystems,and in China's terrestrial and global terrestrial plants.The C/N values of plant communities are similar to those of other terrestrial plants,but the C/P and N/P values are much lower than those of wetland ecosystems,forest ecosystems,and Chinese terrestrial and global terrestrial plants.Therefore,the plant communities in the riparian zone of the Three Gorges Reservoir showed high P and low N/P characteristics.The average N/P of the plant community in the riparian zone was 4.41±2.00,which was less than the minimum threshold of N/P,indicating that the plant community in the riparian zone of the Three Gorges Reservoir was restricted by N.2)Compared with the plant community above175m control area,the content of the community elements in the riparian zone and its measurement ratio are special.The content of C in the community of the riparian zone is lower than control area,but the closer to the downstream sampling section,the smaller the gap is.The N content of the plant community in the riparian zone is lower than the control area in the west of the Daning River section,and is higher in the east;In the whole section,the P content of the plant community in the riparian zone is always higher than that of the control area;the K content of the plant community in the riparian zone is higher than the control area east of the Daning River,east of the Daning River.The K content of the plant community in the riparian zone is more sensitive to flooding and is more different from the control area.The C/N of the plant community in the riparian zone is lower than that of the control area,and the gap is larger in the east of the Baijiaxi section;the C/P of the planting community in the riparian zone is lower than the control area to the west of the population,and higher than the east.The N/P of the fading zone is lower than the control area in the west of the Xiangxi estuary section,and higher than the control area in the east,indicating that the planting community of the fading zone west of the Xiangxi estuary section is more restricted by N.3)Affected by the topography and soil types of different sampling areas,the C,N,P,K content and its measurement ratio of the plant communities in the riparian zone of the Three Gorges Reservoir showed a certain change in the space of the whole section,and the overall trend of this space not affected by flooding.The C content and C/N of the plant community in the riparian are lower in the two sections?Jiangjin,Nan'an,Fuling and Xiangxi River,Zigui,Yichang?,and the middle section?Yunyang,Fengjie,Wushan?is higher.The spatial law is“parabola with opening downwards”;the spatial variation of N content and N/P in the community of the riparian zone is opposite to that of C,which is the“parabola of opening up”,which reaches the minimum value near Yunyang;P The spatial variation trend of K content is relatively flat,and the performance is the lowest in the middle section?Yunyang,Fengjie,Wushan?,and the relatively high regularity of the two sections?Jiangjin,Nan'an,Fuling and Xiangxi River,Zigui,Yichang?.The spatial variation trend of C/P is also relatively flat,showing that the middle section?Yunyang,Fengjie,Wushan?is relatively high,and the two sections?Jiangjin,Nan'an,Fuling and Xiangxi River,Zigui,Yichang?are relatively low.4)Among the four typical plants in the riparian zone,the C content of C,N,P and K in different plants showed root>stem>leaf,and the other elements N,P and K were all leaves>stem roots,showing The characteristics of leaf enrichment of nutrients.C/N and C/P in different organs of different plants showed roots and stems larger than leaves.N/P of different plant species showed leaf>root>stem.The results of comparison of similar elements and ratiometric parameters of four plant organs were as follows:the content of C and the content of root N in roots and stems of Cynodon dactylon were the highest,the root C/N was the lowest,the leaf C/N was the highest,the root C/P was the highest,and the leaf C/P was the highest.The highest,roots and stems N/P was the highest;the leaves of Bidens tripartita were the highest N content,the highest stem C/N,the lowest C/N content,the highest C/P content,the highest N/P content in leaves;and the P content of Xanthium sibiricum root,the content of N,P,K,leaf N and K were the highest,stem C/N was the lowest,root C/P was the lowest,stem C/P was the lowest;Abutilon theophrasti C,K content and leaf P content were the highest,root C/N The highest,leaves C/P,N/P lowest.5)The ecological stoichiometry of the four typical plant roots,stems and leaves showed a certain regularity in the spatial distribution.The content of C is consistent with the spatial variation trend of different plants and organs.From the upstream to the downstream of the reservoir,the C content is generally the same as the“opening parabola”of the“opening parabola”.The N content is in different plants and organs.The spatial variation trend is also consistent,but contrary to the change trend of C content,from the upstream to the downstream of the reservoir,the N content shows a pattern of decreasing first and then increasing;the variation of P content is inconsistent between different plants and organs;The spatial variation of K content in different plants and organs was similar to that of C content,and the overall performance showed a trend of increasing first and then decreasing.The spatial variation trend of C/N in different plants and the same organs is consistent.From the upstream to the downstream of the reservoir,the C/N of the roots is similar to the law of“opening parabola”.The stem C/N showed a gradual increase.Leaf C/N was significantly lower than roots and stems,and spatial changes were not obvious.Affected by P content,C/P and N/P have inconsistencies in the spatial variation of different plants and organs.6)Under different flooding gradients in the lateral space of the riparian zone,the response results of plant communities C,N,P and K were not all the same.The C and N contents of plant communities were not significantly different under different flooding gradients?p>0.05?,and the P and K contents were significantly different?p<0.05?,indicating that the submerged gradient was in the lateral space of the Three Gorges Reservoir.The distribution of C and N contents in the community had little effect,but had a great influence on the distribution of P and C contents in plant communities.Under different flooding gradients,the C/N value of plant communities was not significantly different?p>0.05?,and the difference of C/P and N/P values was significant?p<0.05?,indicating that the planting community C/N was in lateral space.The distribution has little effect,but the distribution of plant communities C/P and N/P in lateral space has a great influence.These phenomena indicate that:1)the ecological stoichiometric characteristics of the plant communities in the riparian zone have wetland characteristics,which are subject to spatial variability due to changes in the geographical environment factors of the Three Gorges reservoir area;2)water-flooding has an important influence to the stoichiometry.The plant community has higher N/P above 175m control area;3)the flooding gradient has some influence on the plant community ecological stoichiometric parameters;?4?the ecological stoichiometric characteristics of typical plants in space is affected by both the flooding gradient and the longitudinal dimension.Finally,in the future,we should carry out research on soil nutrients in habitat soil nutrients and watershed spatial scales under different flooding gradients,and supplement the understanding of the elemental response relationship in plant-soil systems.