The Research Of Wetlands Communities Structure And Interspecific Relation In Sanjiang Plain

The most important component of wetlands ecosystem is the plants,which is a key factor of wetlands ecological function.The distribution of wetlands plants and structures of wetlands communities are influenced by hydrological processes.The changes of hydrological regimes may be the key factor determining wetlands plants species diversity and vegetation succession,which is also a hot issue in wetlands ecology at present.However,due to the lack of long-term continuous in situ observations,there is still a great uncertainty in the cognitions of this scientific problem.The Sanjiang Plain is the largest concentrated distribution area of freshwater wetlands in China,where human activities such as wetland drainage reclamation are the most intense in recent decades.Based on the above background,typical wetlands in Sanjiang Plain,Honghe National Reserve in Heilongjiang Province was selected as the research object.Plant observation of a transect belt was deployment in 8 years and observation of 44 communities was deployment once.Combining the experiments of cultivations,we studied the effects of water regimes to community structures and interspecific relationships,etc.The succession laws and key species of plant communities of wetlands were revealed in the context of water regimes changes.The effects of interspecific relationships on community stabilities were clarified,and the effects of water level gradients on interspecies competitiveness of typical marsh plants were discussed.Ultimately,we summarized some conclusions:(1)Based on the long-time observation,we conformed that the current plants community structures are affected not only by water regimes of the same year,but also by the water regimes of previous year in a great extent.Inundation duration,inundation frequency and fluctuation of water level are the key characteristics of water regimes that affect community structure besides water level characteristics.(2)In the conditions that water levels increased year by year,seven communities in the transect belt had succession to hygrophytic direction in some degrees.Anemone dichotoma,Deyeuxia angustifolia,Glyceria spiculosa,Carex lasiocarpa and Carex pseudo-curaica were the key species in the succession process.The changes of Anemone dichotoma and Deyeuxia angustifolia resulted the successions of Deyeuxia angustifolia community,Spiraea salicifolia-Deyeuxia angustifolia community and Deyeuxia angustifolia-Carex appendiculata community.The changes of Glyceria spiculosa,Carex lasiocarpa and Carex pseudo-curaica resulted the succession of Deyeuxia angustifolia-Carex lasiocarpa community,Carex lasiocarpa-Glyceria spiculosa community and Carex pseudo-curaica community.(3)The changes of the overall species diversity and internal heterogeneity of the community were different in different water level environments in the succession processes.The trend of Salix rosmarinifolia community was completely opposite to that of Carex lasiocarpa-Glyceria spiculosa community and Carex pseudo-curaica community.(4)Stability of community structure has changed during the processes of succession.The stabilities of Salix rosmarinifolia community,Deyeuxia angustifolia community and Spiraea salicifolia-Deyeuxia angustifolia community declined.The stabilities of Deyeuxia angustifolia-Carex appendiculata community reached a new steady state,after declined.The stability of Deyeuxia angustifolia-Carex lasiocarpa community declined again after reaching steady state.The stability of Carex lasiocarpa-Glyceria spiculosa community and Carex pseudo-curaica community increased gradually to reach stable states.At the same time,the interspecific relationships of main species in the communities changed from facilitation to competition or from competition to facilitation.(5)Generally,the α diversities of communities formed by emergent species were higher than that of communities formed by submerged or floating species.The dominant species of communities formed by submerged or floating species were highly specific to the habitats and distributed evenly in their specific habitats.The structures of these communities were stable relatively.Carex schmidtii,Carex meyeriana and Betula fruticose were highly specific to the habitats and distributed evenly in their specific habitats,and the structures of communities formed by them were steady.Deyeuxia angustifolia,Glyceria spiculosa,Carex lasiocarpa and Carex pseudo-curaica distributed widely and unevenly in same habitat.(6)Glyceria spiculosa,Carex lasiocarpa and Carex pseudo-curaica were the key species to determine the community structures in alternate dry and wet habitats.In the absence of interspecific competition,Carex lasiocarpa and Carex pseudo-curaica exhibited similar survival strategy generally,which was tending to conserve physiological individuals to improve survival in flooded environments.When the full competition with Glyceria spiculosa was present,the inhibition of Glyceria spiculosa to Carex lasiocarpa was decreased and the inhibition of Glyceria spiculosa to Carex pseudo-curaica was increased with the increase of flooding stress.