| Mangroves are important wetland types in tropical and subtropical coasts and have powerful ecological functions.Mangroves in China belongs to the northern margin of mangrove distribution,the ecosystem and community structure are relatively simple,and its stability is relatively low,which is easy to be affected by various disturbances.Due to the ponds deforestation at the end of last century,as well as the typhoon and Sphaeroma disasters in recent years,the mangroves in Dongzhaigang formed a large area of forest GAPs.At present,the restoration is mainly carried out by artificial planting,but the artificial restoration has the deficiency of single tree species,destroying benthic habitat and so on,and the concept of natural restoration is more and more favored by managers.However,the process of natural restoration of mangroves and its influencing factors are not clear,so it is necessary to carry on the research on mangroves natural restoration.Based on Google Earth primary election,field investigation and communication with the staff of the reserve,13 natural restoration forest GAPs formed at different times were selected for community structure investigation,the composition and structure of mangrove plants were analyzed,and the natural restoration process and law of mangrove communities were discussed.At the same time,according to the reproductive body characteristics of common mangrove plants in the recovery process,this study evaluated the natural regeneration ability of common mangrove plants in the reproductive body stage through control experiments,and further explained the process and law of natural recovery.The details are as follows:1 Restoration process of mangrove communityA total of 12 species of true mangrove plants were found in 39 samples of 13 plots,including Rhizophora stylosa,bruguiera sexangula,Bruguiear gymnorrhiza,Kandelia candel,aegiceras corniculatum,Acrostichum aureum,sonneratia caseolaris,Sonneratia apetala,Avicennia Marina,Acanthus ilicifolius,Bruguiear sexangula var.and Ceriops tagal.Using principal component analysis,13 plots could be divided into three groups : recovery group phases 1(2-4 years),recovery group phases 2(4-7 years),and recovery group phases3(7-30 years).In the early stage of recovery,aegiceras corniculatum,bruguiera sexangula, Rhizophora stylosa and Kandelia candel were dominant species;in the middle stage of recovery,aegiceras corniculatum was still dominant species,and the growth of sonneratia caseolaris and Sonneratia apetala,was rapid;in the later stage of recovery,Rhizophora stylosa,bruguiera sexangula and Bruguiear gymnorrhiza,were dominant,and the community structure tended to stabilize at this time.With the restoration of mangrove plants,the Shannon-Wiener and simpson diversity index,total number of individuals and tree species of mangrove plant community gradually increased,slightly decreased after reaching the maximum value in about 7 years,and then tended to stabilize;the Pielou uniformity index gradually increased,reached the maximum value and tended to be flat in about 7years,when the community structure was relatively stable.2.The main factors affecting the recovery processThere was a very negative significant correlation between the relative elevation and the number of plants and trees in the mangrove community(P<0.01),that is,the lower the terrain,the more plants and tree species;however,the maximum value of biomass appeared at a height of 10-15 cm(distance from the tidal creek surface).There was a significant negative correlation between the tidal creek distance and the number of plants and trees in the mangrove plant community(P<0.05),that is,the closer to the tidal creek,the more plants and tree species in the mangrove plant community;but the biomass was the maximum at 5-10 m distance from the tidal creeThere was a significant negative correlation between the distance of the mother tree and the number of plants(P<0.01),that is,the farther away from the parent tree,the less the number of plants;however,the maximum values of species and biomass appeared 5-10 m.There were significant positive correlation between Shannon index,Pielou index and N:P,and significant negative correlation between Simpson index and soil density.RDA ranking analysis showed that mangrove plants were mainly affected by relative elevation at the initial stage of restoration,and the middle stage of restoration was mainly affected by soil density,moisture and salinity,while the late recovery stage was affected obviously by distances to tidal creeks.3.Effects of propagule characteristicsThe order of natural regeneration ability of mangrove plant was obtained by comprehensive evaluation of reproductive period,productivity,floating ability,and germination rate: aegiceras corniculatum(0.89)> Kandelia candel(0.65)>Rhizophora stylosa(0.56)> Ceriops tagal(0.50)> Bruguiera sexangula(0.42)> Bruguiear gymnorrhiza(0.39)> Bruguiear sexangula var.(0.33)> Avicennia Marina(0.25). |
