Effects Of Simulated Acid Rain With Different S/N Ratio On Schima Superb Seedings Treated By Different Spraying Methods

Acid rain is one of the ten environmental problems in the world, and its effects on plants have become research subject that has gained much attention. Effects of acid rain on plants include direct effect and indirect effect through soil acidification. Lots of simulated acid rain leaching experiments based on pot-grown plants previously often mixed the effect of acid rain on plant and on soil together, and this maked it hard to disclose the change of plant physiology and plant growth under acid rain stress. Moreover, acid rain with different S/N ratio has different effects on plants. Therefore, to research the mechanism of direct effect and indirect effect through soil acidification of acid rain with different S/N ratio is of great significance.This research taked the seedlings of Schima superb which is the dominant tree species in east China sub-tropical area as research material, and used the two spraying methods of canopy spraying and soil spraying to investigate the change of indexes including apparent injure symptom, growth and biomass allocation, photosynthetic physiology as well as soil and leaf elements during one and a half years’ treatment by sulfuric acid rain(S/N=8/1) and nitric acid rain(S/N=7/10)(moderate acid rain pH3.5,severe acid rain pH2.5).1. When sprayed acid rain with different S/N ratio to canopy, the leaves of Schima superb only appeared apparent injure symptom treated by severe acid rain. The two kinds of acid rain with different S/N ratio both restrained the growth of Schima superb stem and reduced photosynthetic rate by causing the close of stoma.(1)Treated with sulfuric acid rain, Mg, K and the Chlorophyll content of Schima superb seedlings decreased, while the water use efficiency, root shoot ratio and specific leaf area didn’t get significant influence; moderate acid rain treatment increased photosynthetic active area so as to improve biomass by stimulating the growth of lateral branch; severe acid rain decreased the biomass of root, stem and leaf of Schima superb seedlings.(2)Effects of nitric acid rain treatment on chlorophyll, root shoot ratio and specific leaf area was not significant. Moderate acid rain decreased the biomass of the Schima superb seedling organs in the following order:root, leaf, and stem; severe acid rain increased the biomass of different organs.2. Spraying acid rain to soil, different S/N ratio will incur soil acidification and the decrease of soil Ca2+, thus will make the soil Al and Ca2+transfer into Schima superb seedlings on the one hand, and promote the nitrogen absorption of Schima superb seedlings by increasing soil nitrogen on the other hand.(1) Treated by sulfuric acid rain, the change of chlorophyll content and net photosynthetic rate of Schima superb seedling was not significant. Moderate acid rain restrained the growth of Schima superb seedling at first, then changed to promoted its growth. Severe acid rain showed promotion effects at first and then changed to restrain its growth.(2) Nitric acid rain treatment showed great add-nitrogen effects to soil and Schima superb seedling leaf. It promoted the synthesis of photosynthetic pigments, and improved photosynthetic rate and increased biomass. The higher the acidity, the more obvious the promotion was.3. The influence of acid rain to Schima superb seedlings had inter-year difference and accumulative effect. Schima superb seedlings showed slower response to acid rain stress under soil spraying than under canopy spraying.