Adapted Species Selection For Vegetation Restoration And Reconstruction Of Freshwater Forested Wetlands

Based on the investigations of floristic composition, vegetation type and soil physicochemical properties of Shengjin Lake Nature Reserves in Anhui Province, eight native species and seven exotic species were planted in three different water-table plots in order to observe their water-resistant. Seven adapted species were suggested, they are Liquidambar formosana, Salix babylonica, Ascendens×mucronatum, Salix×aureo-pendula, Populus deltoids, Taxodium distichum and Taxodium ascendens for the vegetation restoration and reconstruction of the freshwater forested wetlands. These results would provide a technical supports and fundamental theories for species selection for vegetation restoration and reconstruction of the freshwater forested wetlands in the middle and lower reaches of the Yangtze River. The main results are as the follows:1) The wetland herbages were very abundant in Shengjin Lake Nature Reserve, with 275 species of Spermatophyte belonged to 173 genera in 59 families and 15 species of Pteridophgtes belonged to 13 genera in 13 families. The flora was of biodiversity and ancient origin. The floristic geographical components were multiform with obvious transitions where were charactered with the main subtropic type and followed by the temperate. Furthermore, this flora had multiple characters of the tropic, subtropic and temperate, of which the subtropic was most evident. The environmental habitat was complex with high biodiversity. The vegetations were classified into 2 vegetation types, 4 sub-vegetation types and 12 formations.2) The soil in the low water-table plot was loam and stiffness, but in the middle and high water-table plots were clay loam soil in the experiment site. The soil water contents in three levels were all high and increased rapidly with the water table rised. The bulk density was over 1.3g/cm3 except 0-10cm layer, and decreased with the increased water-table. The soil non-capillary porosity was very low, indicating that it was difficult for roots to spread to soil. The capillary porosity accounted for 94.54% of the total porosity, suggesting the soil had strong water capacity. The total porosity in middle and high water table sites was higher than that in low water table plot, where were suitable for crop to grow. Meanwhile, the pH, organic matter, total nitrogen, total phosphorus and potassium in soil of all our experimental area satisfied common trees to grow. Therefore, the soil physics properties should be taken into account in the species selection in the important place.3) The survival rate of the seedlings were observed after 14 months since they were planted. The survival rates of eights native species were Liquidambar formosana(99.0%), Salix babylonica(98.3%), Salix×aureo-pendula(91.3%), Ascendens×Mucronatum(51.2%), Sapium sebiferum(50.0), Metasequoia glyptostroboides(7.3%), Alnus trabeculosa(4.0%) and Pterocarya stenoptera(1.8%). The survival rates of seven exotic species were Populus deltoids(79.7%), Taxodium asendens(72.4%), Salix integra'Hakuro Nishiki'(56.8%), Diospyros kaki(55.6%), Taxodium distichum(34.6%), Carya illinoensis(15.8%) and Nyssa aquatica(6.3%). So we can see that Liquidambar formosana, Salix babylonica, Salix×aureo-pendula, Populus deltoids and Taxodium asendens were of strong adaptability and water-resistant. In contrast, Metasequoia glyptostrobides, Alnus trabeculosa, Pterocarya stenoptera and Nyssa aquatica were of weak adaptability and water-resistant.4) The relationships between the flooded survival rate and flodded depth and flooded duration were explored. Within the native species, the flooded survival rates of Liquidamba formosana and Salix babylonica were 100% in the 80cm depth flood of 86 days duration. The flooded survival rate of Salix×aureo-pendula was 100% in the flood of 51.3cm depth flood of 64 days duration. The flooded survival rate of Ascendens×mucronatum was 95.8% in the 1/2 seedling height depth flood(51.3cm) of 64 days duration. The livability of Metasequoia glyptostrobides, Alnus trabeculosa and Pterocarya stenoptera were low, suggesting that their water-resistant were weak and not adapted to grow in this wetland. Within the exotic species, the flooded survival rate of Populus deltoids was 100% in the 67.2cm depth flood of 85 days duration and 83.3% in the 83.3cm depth flood of 87days duration. But Populus deltoids could not adapt to live at dry and cold environment after long flooded. The flooded survival rate of Taxodium asendens was 100% in the 65.9cm depth flood of 84 day duration. But its survival rates decreased with the flood time when the flooded depth below 90cm, it maybe because of the soil was too clay. The flooded survival rate of Taxodium distichum was 70.6% in the 70cm depth (1/2 of seedling's height) flood of 85 day duration. But Taxodium distichum could only live 30 days in the 100cm depth(2/3 of seedling's height) flood with 87.1% flooded survival rate. Salix integra'Hakuro Nishiki'could only survived 30 days at the depth of 52.9cm flood.