Investigation Of Evergreen Broad-Leaved Tree Species In Central Shaanxi Area And Study On Cold Resistance

Evergreen broad-leaved treees distribute in the subtropical warm and moist regions of Yangtze River Valley in China.They are the main elements of subtropical forest vegetation and the most important trees in the south gardening because of their special view.But their species and numbers decease obviously as the latitude rises from south to north.It is possible to introduce,tame and apply evergreen broad-leaved trees in recent years with the globle warming.In fact, some evergreen broad-leaved treees have been widely applied in the northern city of gardens.However,the ablility to adapt to the enviroment of evergreen broad-leaved species is still a problem in the northern city and temperature as limitation to introduce to higher latitude regions for evergreen broad-leaved trees is one of the important envrionment factors.In order to put forward scientific consulting for forecasting,choosing,cultivating and applying of subsequently introduced evergreen broad-leaved trees,the article firstly study on wintering compatibility,physiology and ecosystem research of freezing resistance of some evergreen broad-leaved trees in Guanzhong of the south warm temperate zone.The main results indicate:1. There are 24 branches,44 genus and 129 kinds of evergreen broad-leaved tree species altogether in central Shaanxi area, among which have 23 kinds of arbors, 62 kinds of shrubs, 14kinds of vines and ground-covers,30 kinds of bamboos.2. In central Shaanxi area,the main branches of evergreen broad-leaved plants are Oleaceae,Celastraceae,Rosaceae,Magnoliaceae,Fagaceae,Berberidaceae,Gramin-eae and so on. As for the genus distribution type, there are 18 genera of tropic type, accounting for 40.91% of the total, and 26 genera of temperate type, accounting for 59.09% of the total.3. Eight evergreen broad-leaved tree species are most widey applied in Guanzhong area, inculding Ligustrum lucidum, Magnolia grandiflora, Trachycarpus fortunei, Photinia serrulata, Osmanthus fragrans, Eriobotrya japonica, Pittosporum tobira, Nandina domestica.4. Wintering compatibility of eight evergreen broad-leaved trees was observed in the introduced region, tree leaves of different freezing resistance appeared different freezing symptoms. Some species'most leaves remained light and green which have stronger freezing resistance as Photinia serrulata,Eriobotrya japonica, Magnolia grandiflora and Pittosporum tobira. Some species leaves layers appeard brown and dead spot which have middle freezing resistance as Ligustrum lucidum, Osmanthus fragrans.Most leaves tips of some species were dry and recovered slowly after spring and some species leaves were all like cooked and dropped at last although the new leaves grow faster, the former was as Trachycarpus fortunei and the later was as Nandina domestica, the two of which have weaker freezing resistance.5. Researching the cold resistance of eight evergreen broad-leaved trees which have higher important value, relative electrical conductivities of leaf were combined with Logistic, lethal tempetature 50(LT50) which were calculated could correctly indicate freezing resistance of these trees in quantitative determination. The results of freezing resistance of leaf are almost corresponding to observation of wintering in the Central Shaanxi area. The results showed that the ablility of cold resistance is that Eriobotrya japonica, Photinia serrulata > Magnolia grandiflora, Trachycarpus fortunei, Pittosporum tobira > Ligustrum lucidum, Osmanthus fragrans.6. The application forms of evergreen broad-leaved trees in Central Shaanxi area include that road greening, foundation planting, courtyard greenery, hedge and land virescence, among which hedge forms are most widely applied.7. Problems and suggestions to introducing and applying evergreen broad-leaved species in Central Shaanxi area were proposed.