| Comparing with the native trees of Rhus chinensis and Cotinus coggygria, the biological characteristics, impact on natural and semi-natural eco-system and invasive ability to natural vegetation of Rhus typhina were studied by labotory test and filed survey in order to elucidate wether R. typhina could threat the natural and semi-natural ecosystem and provide academic basis for its rational utilization.Seed yield and germination rate of of R. typhina was compared with those of R. chinenesis.The results showed that the average seed yield of individual tree of R. typhina and R. chinensis was respectively 18,708 and 33,765 and their average seed amount of single fruit was respectively 576 and 812.The average seed yield of individual tree, seed amount of single fruit and fruit axis length of R chinensis were significantly higher than those of R. typhina. After 90 mins concentrated sulphuric acid etching, the average seed germination rate of R.typhina was 83.8%, higher than that of R chinensis(53.0%). Although large seed yield of R chinensis, seed germination of R. typhina was easier than that of R.chinensis.Comparing with native trees Rhus chinensis, Cotinus coggygria, Ailanthus altissima and Acer truncatum Bung,biological characteristics of R. typhina, such as growth feature, drought tolerance, salt tolerance, shade-tolerant ability, photosynthetic feature and light demand of seedling growth were measured. The anatomical structure of R. typhina,R chinensis and Cotinus coggygria were carried out through Paraffin sections.The results indicated that growth rate of R. typhina was similar to that of Ailanthus altissima, which was higher than that of the other species.Three species of drought-resistant capacity from weak to strong is R. chinensis, R. typhina and Cotinus coggygria. Anatomy test showed that the average thickness of leaves: Rhus typhina (113.67μm)> Rhus chinensis (108.33μm)> Cotinus coggygria (89μm);Fence thickness/leaf thickness values: R. typhina (0.56μm)> Cotinus coggygria (0.53μm)> R chinensis (0.48μm). Salt-tolerant capacity of R. typhina was lower than that of R. chinensis with higher Na+ accumulation in the roots of R typhina(6603.96 mg / kg ) and in leaves of R. chinensis, as high as 10560.34 mg/kg.Trees of R typhina under low light intensity grew slower than those under the high light intensity.Seedlings of R.typhina were more sensitive to light intensity than those of R chinensis because light intensity influnced the morphology development of seedlings of R .typhina,but not R. chinensis. The light saturation point(1588.89μmol·m-2·s-1), light compensation point (39.42μmol·m-2·s-1) and the largest photosynthetic rate(22.72μCO2mol·m-2·s-1) of R. typhina were slightly higher than those of R. chinensis,indicating that light utilization efficiency of R. typhina was higher than that of R. chinensis.Impact of R .typhina on ecosystem was studied through florescence phenology observation,allelopathic activity determination and leaf toxicological analysis.The results indicated that the AE of fresh leaf of R. typhina showed significantly negative influence on the growth of hypocotyl and radicle of wheat.The AE of fresh leaf of R. typhina and R. chinensis showed strong inhibition to root growth of Brassica chinensis.. The AE of fresh leaf of R. typhina and Cotinus coggygria restrained root elongation of Platycladus orientalis, Toona sinensis and Ailanthus altissima significantly. Except to Pinus tabulaeformis, the AE inhibition of R. typhina to Platycladus orientalis, Toona sinensis and Ailanthus altissima was stronger than those of Cotinus coggygria.The allelopathic effect of AE from dry leaf of R. typhina was not as strong as that of AE from fresh leaf.Leachates of surface layer soil obtained from understory of R. typhina promoted root growth of wheat obviously.The seedlings of Toona sinensis grew better in the soil collected from understory of R typhina stands planted 14 years ago than those seedlings grew in the soil from barren hill.Feeding rabbit and rat with fresh and dry leaves of R. typhina showed that leaves of R. typhina had no acute toxicity.Invasion of R. typhina to ecosystem was simulated by artificial seed banks and artificial afforestation.Comparison reforestation of one-year seedlings trial showed that height and diameter growth of R. typhina was superior than those of R chinensis. Growth performance of seedlings from different blocks was different due to different light of different blocks;Trees of R. typhina under strong light grew faster and accumulated more biomass than those under weak light. Survival percent of R. typhina in the forest understory and open space were repectively 75.61% and 67.86%, while R. chinensis were 63.89% and 35.00%. Stem-cut reforestation trial showed that the survival percent was 70.00% in the stand of canopy density of 0.40,while was 18.00% in the stand of canopy density of 0.60. With canopy density increase, biomass accumulation and the survival percent of R. typhina decreased,indicating that R. typhina was sun species. Seeds of R. typhina did not survive under natural conditions. Seeds treated by sulfuric acid were sowed on the steep slopes of Badaling in 2006 summer rain season and results in spring of 2008 showed that many seedlings of Cotinus coggygria survived,but no seedlings R. typhina and R. chinensis.R. typhina has shown many good characteristics since it was introduced into China, however, it seems that it have some trends of invasion.Research should be implemented further to reveal its more advantages and values and to eliminate its disadvanteges in the process of its application. Precautionary measures should be taken to exploit the uses of Rhus typhina gradually on the basis of more comprehensive tests.The habitat conditions should be fully considered before its introduction and cultivation because the growth performance of R. typhina was close related to it. As a pioneer tree species, it could be applied to poor regions, such as barren hills, gravel flood land, gangue and other poor habitat conditions. As a ornamental plant, R. typhina could be used under special engineering technology. R.typhina could be mixed with native dominant species to form stable community in future.
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