Study On The Vegetation Characteristics And Its Influencing Factors Of The Chilling-injured Sonneratia Caseolaris Forest At The Early Recovery Stage On Qi'ao Island, Zhuhai

In this study, in order to ascertain the vegetation characteristics, the main factors of vegetation distribution on the mudflats, and effects of vegetations on the growth of mangroves planted, vegetation and soil were investigated in the chilling injury areas of Sonneratia caseolaris plantation, and simulated tide-inundate tests had been done in the greenhouse. Conclusions could be concluded as follows:(1)Nature vegetation in the chilling injury areas of S. caseolaris plantation were chiefly Acanthus ilicifolius and Spartina alterniflora, with a few other plants associated, such as Aegiceras corniculatum, Derris trifoliate, Cyperus malaccensis, and Phragmites communis 1.5 years after the chilling injury. Vegetation on the chilling injury areas could be divided into five types according to its characteristics, they were A. ilicifolius + S. alterniflora community, the consociation S. alterniflora community, the consociation A. ilicifolius community, A. ilicifolius sparse community and bare flat. A. ilicifolius and S. alterniflora could occupy the mudflats rapidly after the chilling injury.(2)The re-establish of wetland plants in the S. caseolaris plantation after the chilling injury was in chronological as the following order, A. ilicifolius and A. corniculatum, P. communis, S. alterniflora, and the density of A. ilicifolius and A. corniculatum was increased. Bare flat bad the possibility of evolving to A. ilicifolius sparse community, and A. ilicifolius sparse community bad the possibility of evolving to the consociation A. ilicifolius community if there had no human activity.(3)The surface soil (30 cm) of each vegetation plot was low in salts,rich in nutrient,and it was suitable for the growth of wetland plants in the mudflats. There would be the consociation A. ilicifolius communities in the S. caseolaris plantation if A. ilicifolius had been grown under the S. caseolaris forest before the chilling injury, and there would be A. ilicifolius + S. alterniflora community, the consociation S. alterniflora community, A. ilicifolius sparse community or low elevation bare flat if there had no or few plants. The distribution of main types of vegetation was zonality according to the elevation of beach, sort by elevation: A. ilicifolius + S. alterniflora community(196.03 cm) > the consociation S. alterniflora community(193.35 cm)>the consociation A. ilicifolius community(177.38 cm)>A. ilicifolius sparse community(152.58 cm) > bare flat(145.15 cm). Nature vegetation under the S. caseolaris forest before the chilling injury and elevation of beach were the main factors that influenced the ecesis and growth of A. ilicifolius and S. alterniflora in the mudflats of S. caseolaris plantation after the chilling injury.(4)In comparison with S. caseolaris, the consociation S. alterniflora community was not conducive to planting Kandelia candel and the consociation A. ilicifolius community was not conducive to planting Bruguiera gymnorrioza. It had been evolving to a multi-storied plantation 2 years later after S. apetala and S. caseolaris planted in the A. ilicifolius community, and it's the best of the four recovery methods. The consociation A. ilicifolius community had been relatively beneficial to the Survival and growth of mangrove plants compared to the consociation S. alterniflora community, S. apetala and S. caseolaris could be planted in order to restructuring A. ilicifolius and S. alterniflora community.(5)The results showed the seed germination of A. ilicifolius was delayed and its germination rate was reduced under more than 15h·d^-1 waterlogging treatments. The waterlogging time of less than 15h·d^-1 was suitable for seed germination of A. ilicifolius. The chlorophyll content, dry weight of root, stem, shoots and the total biomass under 0³ h·d^-1 waterlogging treatment was significantly higher than the other treatments. In contrast, the total biomass, leaf area and chlorophyll content under more than 18 h·d^-1 waterlogging treatment decreased remarkably and the root shoot ratio of the treated seedlings increased gradually. Our results indicated that A. ilicifolius grew best under 0-3h·d^-1 waterlogging treatment in the artificial cultivation (the artificial seawater salinity was 2‰). The 18 h·d^-1 was the critical waterlogging time of A. ilicifolius. The growth of A. ilicifolius was inhibited significantly under more than 18 h·d^-1 waterlogging treatment.(6)Wetland plants A. ilicifolius and S. alterniflora were planted in a full competition condition. The tiller of each thicket and basal diameter of A. ilicifolius appears negative growth with no less than 18h·d^-1 waterlogging treatments, meanwhile the height growth, dry weight of root, stem, leaf and the whole plant of A. ilicifolius decreased remarkably. The tiller of each thicket a of S. alterniflora appears negative growth with no less than 15 h·d^-1 waterlogging treatments, meanwhile the height growth, the dry weight of root, stem, leaf and the whole plant of A. ilicifolius decreased remarkably. Under the cultivation with artificial seawater salinity of 2‰, the 18 h·d^-1 was the critical waterlogging time of A. ilicifolius, and the 15 h·d^-1 was the critical waterlogging time of S. alterniflora. it was conducive to the growth of S. alterniflora when waterlogging time less than 9 h·d^-1, while it was conducive to the growth of when the waterlogging time 9≤t<18 h·d^-1. In comparison with S. alterniflora, A. ilicifolius had a higher tolerance of waterlogging.