Study On Evaluation And Selection Of Tree Species For Costal Protection Forest In Hangzhou Bay

Considering the shortage of tree species for Shelter-forest and landscape forest on the coastal area of Hangzhou Bay.and focusing on the issue of tree species selection, we conducted the vegetation investigation, tree species evaluation, as well as the tree and clone saline-resistance physiological research. Based on the current situation, the establishment method for saline-resistant tree species evaluation indicator system was discussed. The dynamic of growth and physiological indicators of Fraxinus pennsylvanica clones under the salt stress were studied. The micro-structure and ultrastructure of root and stem of Fraxinus pennsylvanica were observed. The indicators for saline resistance and evaluation method were discussed. The research results will lay a theoretic foundation for saline resistance tree species selection for sea front of Hangzhou Bay.1. Investigation for current situation of natural vegetation and protection forest on the coastal area of Hangzhou Bay.The higher plant species is not rich in the investigation site in newly-enclosed tidal flats in Cixi, with the total species of 59 under 45 genera and 21 families. The main community is Scirpus mariqueter-reed, the natural vegetation are mainly the shrubs of Salix matsudana Koidz and Tamarix chinensi. There is a few herb communities. The main driving vegetation for silt-forming are Scirpus mariqueter and reed. There is no effective wave-provention forest belt, and the bottomland environment need to be protected by artificial promotion.The main natural vegetation in Dainshan Island include MalIotus japonicus, Cyclobalanopsis glauca (Thunb.) Oerst-Stellaria media (L.) Cyr.- Dryopteris spp and Persea thunbergii, Cyclobalanopsis glauca (Thunb.) Oerst.- Stellaria media (L.) Cyr.-Dryopteris spp. They are on succession for regional forest community with the species in Fagaceae as the dominance. Due to the weak natural basis on the sea island, it is necessary to accelerate the natural succession process with artificial method.The remaining stand type is few on the coastal area of Hangzhou Bay with low survival rate and serious diseases and insect pests. The investigation for the protection forest with different tree species and type as well as poplar protection forest with different age Showed that the poplar grows the fastest, followed by Metasequoia glyptostroboides and Robinia pseudoacacia in pure forest. The undergrowth biodiversity in Robinia pseudoacacia forest is high. The structure, volume, wind-shield and disease and pest attack of mixed forest are better than those of pure forest. The remaining rate of poplar decreases year by year, with the wind-shield effect weakening. With the human disturbance, it is difficult for the poplar protection forest to form multiple-layer structure. It is necessary to improve the forest with artificial measurement, increase the biodiverty and form stable multiple layer structure.2. The comprehensive evaluation and selection of salt-resistant trees on Coastal Shelter-forest of Hangzhou BayBy means of establishment of comprehensive evaluation index, including tree-growth, tree-resistance capacity and sight-view etc., method by Analytical Hierarchy Process and factor weight, 54 tree species in Cixi county, Hangzhou Bay and 32 tree species which were under water-salt stress experiment in Fengxian county, Shanghai, the pro-tection forest and sight-view forest were evaluated as follows: the 54 tree species under salt stress of 0.4% content in Cixi could be divided into four categories, 11 tree specie were excellent, 13 tree species were good, 20 tree species were suitable and 10 tree specie were not suitable. Based on the comprehensive evaluation result, the following 15 tree species, which were recommended as arbor tree of protection forest, were Casuarina equisetifolia, Salix matsudana Koidz, Taxodium distichum×T.mucronatu, Quercus virginiana, Gleditsia triacanthos, Sophrajaponica L., Cladrastis platycarpa, Pistacia chinensis Bunge, Fraxinus pennsylvanica, Ligustrum lucidum, Taxodium mucronatum, Acacia dealbara Link, Sapium sebiferum, Callistemon rigidus R.Br, Koelreuteria paniculata. The following 4 trees species which were recommended as shrub tree of protection forest, were Nerium indicum Mill., Viburnum odoratissimum, Pittosporum tobira (Thunb.) Ait., Hibiscus hamabo. There was no significant difference among these tree species for sight-view, except the selection sequence. The 32 tree species in FenXian county were divided into four categories, 3 tree specie were excellent, 5 tree species were good, 6 tree species were no bad and 18 tree specie were not suitable. Based on the comprehensive evaluation result,, the following 5 tree species which were recommended as arbor tree of water-salt resistant forest, Pistacia chinensis Bunge, Sapium sebiferum, Gleditsia triacanthos, Platycladus orientalis (L.) Franco., Ailanthus altissima Swingle v. and two shrub trees, which were Elaeagnus pungens Thunb, and Hibiscus hamabo, but due to short introduction period, further observation was suggested.3. Growth and Physiology reaction of 6 tree species under salt stressIt was found that growth was inhibited apparently in all species. Permeability of cell membrane, Proline content, SOD activity, soluble protein and Na+ content increased under the stress of NaCl in most species. They were obviously elevated with higher Na+ concentration, but not with lower Na+ concentration. However, there were differences among the species in response time. Through PRLNCIPAL Component analysis, factors such as height growth rate, Proline content, SOD activity, index of salt harm, biomass, relative conductivity could be used for selection of tree species under salt stress. Based on Analysis of growth rate and physiology indexes, tree species were arranged in ordering according to their tolerance as Salix matsudana Koidz., Quercus virginiana, Fraxinus pennsylvanica, Gleditsia triacanthos, Myrica cerifera and Platanus occidenntalis.4. Growth and physiology reaction of Fraxinuspennsylvanica clones under salt stressThe tolerance of Eight clones of Fraxinus pennsylvanica were analyzed using solution curare system. It was showed that there were obvious difference among the clones in Biomass, chlorophylls content, electrolyte leakage, Proline content, MDA content, Na+ content and root characters. However, no apparent differences were observed in net photosynthetic rate, stomatal conductance and SOD activity. Growth and photosynthesis decreased significantly under higher salinity. In contrary, permeability of cell membrane, Proline content, MDA content and Na+ content increased with salt treatment, the most variances appeared among Fraxinus pennsylvanica clones when the concentration NaC1 increased to 4g/L～6g/L. As the result, it was sutible to select clones in the salinity zone The best model was exponent equation for biomass decrease with salinity. 8 clones could be classified into 4 families by Cluster analysis, indexes of net growth, permeability of cell membrane, chlorophylls content and Na+ content could be used for selection. 4-20 and 1-17 were the best clones.5. The changes of root and stem in Fraxinus pennsylvanica under salt stress on microscopic structural and untrastrueturalIn the research on microscopic structural and untrastructural changes of root and stem in Fraxinus pennsylvanica under 6%Nacl stress, the cambium activity and secondary tissues differentiation were observed by light microscopy (LM) and transmission electron microscopy (TEM), respectively. The present results indicated the remarkable impact of salt stress on cambium cell activity and secondary xylem cell differentiation of both root and stem. In comparison with control samples, cambium cells of salt treated materials appeared low activity without any new differentiating phloem and xylem cells under LM. In the samples under salt stress, TEM observations shown the large central vacuole in active cambial cells divided into smaller ones and apparent plasmolysis. Protoplast of fusiform cell formed into strip membrane structure with slight degeneration. The fine structure of cell organelles appeared rough and unclear, and even disaggregating.