Effects Of Habitat Change On Sprouting And Growth Of Dominant Plants In Herbaceous Marsh Wetland

With the intensification of global climate change and human activities,the groundwater level of herbaceous marshes has decreased,the climate has significantly warmed,and the exogenous nitrogen input has increased due to farmland water retreat.The wetland habitat has undergone significant changes.Hydrological regime,temperature and nitrogen nutrition are the key environmental factors affecting germination,seedling survival and seedling growth of herbaceous marsh plants.The dominant plants(Glyceria spiculosa,Carex lasiocarpa,Menyanthes trifoliata,Deyeuxia angustifolia,Carex pseudocuraica,Caltha palustris and Iris laevigata)in the herbaceous marsh wetland of the Sanjiang Plain were used as the experimental organisms.The experiment on the effects of water depth and temperature on the rhizome sprouting of dominant plants,the experiment on the effects of water depth and nitrogen addition on the growth of dominant plants,and the field investigation on the functional traits of dominant plants along with the vegetation zone in typical herbaceous marsh wetland of the Sanjiang Plain were conducted.Research showed that:(1)Under different water depth and temperature conditions,the rhizome bud sprouting percentage of G.spiculosa,C.lasiocarpa and M.trifoliata all increased rapidly at first and then slowly with the change of time.Compared with M.trifoliata,the rhizome bud sprouting of G.spiculosa and C.lasiocarpa was more sensitive to water depth and temperature,and the period of sprouting was relatively short.The suitable water depth of G.spiculosa for sprouting was 0 cm,and-5 cm for C.lasiocarpa and M.trifoliata.However,the water depth of 5 cm was not conducive to the rhizome bud sprouting of these three wetland plants.The optimum temperature for rhizome bud sprouting of G.spiculosa was 10-13 ?.The optimum temperature for the rhizome bud sprouting of C.lasiocarpa was 16-22 ?.The optimum temperature for the rhizome bud sprouting of M.trifoliata was 19-22 ?.(2)The response of wetland plants to water depth and nitrogen addition depended on particular species and their functional traits.In terms of species,C.pseudocuraica was more sensitive to water depth,C.lasiocarpa was more sensitive to nitrogen addition,and Iris laevigata had significant response characteristics to the interaction between water depth and nitrogen addition.In terms of traits,leaf area,above ground biomass and root : shoot ratio were sensitive to environmental changes.Above ground traits of dominant plants in herbaceous marsh wetland had more significant effects on above ground biomass of dominant plants.Plant height,leaf area,specific leaf area and ramet number were the main functional traits that affected the above ground biomass of dominant plants in herbaceous marsh.The relationship between functional traits of dominant plants and above ground biomass was species-specific.The plant height,leaf area and ramet number of the grass(G.spiculosa,C.lasiocarpa,D.angustifolia and C.pseudocuraica)were significantly related to the above ground biomass,while the specific leaf area and ramet number of the forb(M.trifoliata,C.palustris and I.laevigata)were significantly related to the above ground biomass.(3)On the vegetation zone in typical herbaceous marsh wetland,there were significant differences in plant height,specific leaf area and above ground biomass of G.spiculosa;leaf area and specific leaf area of C.lasiocarpa;plant height,leaf area,specific leaf area and above ground biomass of D.angustifolia;above ground biomass of C.pseudocuraica.Specific leaf area and above ground biomass were more sensitive traits on the vegetation zone in typical herbaceous marsh.In terms of species,the sensitivity of functional traits of Gramineae(D.angustifolia and G.spiculosa)to habitat change was significantly higher than that of Cyperaceae(C.lasiocarpa and C.pseudocuraica).