Responses Of Chinese Hickory(Carya Cathayensis) To Soil Acidification And Aluminum Stress

Degradation of Chinese hickory(Carya cathayensis)forests has become a serious problem due to serious soil acidification.On the basis of previous studies,a field survey to the degraded forests in main producing area was conducted.And a pot experiment and a field trial were set up to clarify responses of the Carya cathayensis saplings to aluminum(Al)and low pH stresses.The main results were as follows:(1)Soil survey from the 33 production bases of Lin’an(the majority of Chinese hickory growth area)showed that soil pH varied from 4.0 to 6.5.There was a proportion of 64% of the soil with pH <5.5.There were 97% of the forest soil hydrolytic nitrogen >100.0 mg·kg-1,27% of soil available phosphorus <5.0mg·kg-1,and 27% soil available phosphorus >15.0 mg·kg-1,60% of soil available potassium >80.0 mg·kg-1.(2)The optimal nutrition solution pH was pH 5.5-6.5 for plant growth of the Carya cathayensis saplings.The growth of saplings began to be deteriorated at pH ≤ 5.5.While the worst growth was at pH4.5,membrane permeability of young leaves increased significantly and the enzymes activities decreased significantly(p<0.05).The concentrations of N,P and K in the leaves were decreased significantly.The saplings growth at pH6.5 showed normal appearance,yet the roots indexes were lower than pH 6.0.(3)Plant growth of Carya cathayensis saplings was inhibited at 0.25 g per plant,and significantly injured by higher Al(1.0 g and 0.5 g per plant)in an open field nursery(p<0.05).Lower Al(0.125 g per plant)of saplings growth and roots vitality were not affected.Results from present study indicates that the Carya cathayensis forests degradation is closely related to soil acidification.Soil fertilization structure and soil improvement measures need to be adjusted according to soil testing,to remedy soil acidity and optimize soil nutrient status.