| Plant functional traits are reflected the response and adaptation of plant species to the environment ecosystem and it is the result of their interactions.The 'leaf economic spectrum'(LES)of traits has been established based on six ecophysiological variables on a global scale,e.g.leaf area,leaf mass,photosynthetic capacity,dark respiration,nitrogen(N),phosphorus(P)and leaf lifespan(LL),while this study merely concentrated on terrestrial plant.Compared with terrestrial plants,aquatic plants occupy different ecological niche and invariably receive lower levels of sunlight,oxygen and nutrients in aquatic environment.Therefore,exploring the functional traits of aquatic plants and relationships among traits are extremely important to provide insights into the adaptation strategies and contributed to expand leaf economic spectrum to plant economic spectrum.However,aquatic plants have less academic attention.This study aims to compare variation and co-variation of leaf,stem and root economic traits between hydrophytes and sympatric terrestrial plants,and further to explore the ecological strategies of the aquatic plant.We collected 160 species from 45 sites across north to south of Shaanxi Province,including 73 aquatic plants and 87 terrestrial plants(122 genera and 50 families).The sampling areas included the Yellow river basin,Hanjiang river,Weihe river,Wudinghe river basin and so on.Fifteen plant economic traits of these species were measured,including specific leaf area(SLA),dry matter content and C,N,P stoichiometry in leaf,stem and root.The results indicated that:(1)Hydrophytes performed much higher SLA and lower mean LDMC,SDMC,RDMC,SCC and RCC compared with that of terrestrial plants in order to adapted the aquatic environment,that is,there were differences in mean traits about the economics trade-offs faced by hydrophytes and terrestrial plants.The higher SLA values of hydrophytes is mainly due to hydrophytes tend to increase photosynthetic area to capture more light,CO2 and bicarbonate in order to adapted the aquatic environment with lower levels of sunlight and less oxygen.While the lower mean LDMC,SDMC,RDMC,SCC and RCC may be the water environment resulted.(2)We present for the first time an overall plant economics spectrum,including nitrogen,phosphorus and carbon relationships among leaf,stem and root and meanwhile contributed to expand leaf economic spectrum to plant economic spectrum.The leaf economic spectrum of aquatic plants in this region coincided with the worldwide leaf economics spectrum,while while hygrophytes is located at the extreme of thinner leaves which is conducive to rapid acquisition of resources.(3)By integrating leaf,stem and root economic traits into plant economic spectrum of aquatic plants,aquatic and terrestrial species can be discriminated by fewer functional traits related to the resource acquisition and support tissues(such as SLA and SDMC).(4)As for all pairs of traits,the trade-off in plant resource investment across plant organs within individual plants is constrained within a rather narrow range of variation that associate with carbon and nutrient economy(LDMC vs.RDMC;SLA vs.RNC).(5)The functional traits of submerged plants and free-floating plants were most have significant difference with most of other life-form plant species,while the difference among emergent plants,hygrophytes and terrestrial plants were not significantly in most of variables(especially for emergent plants and hygrophytes).In conclusion,we present for the first time an overall plant economics spectrum and their overlap between hydrophytes and adjacent terrestrial species,including nitrogen,phosphorus and carbon relationships among leaf,stem and root and revealed the adaptation strategies of aquatic plants.These findings are the important complement to the functional traits of aquatic plants and will provide a deeper understanding of hydrophytes adaptation strategies and have an important significance of the plant classification. |
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