| The harm of acid precipitation to forest ecosystem is one of the global environmental problems. Up to now, the effects of acid precipitation to eco-environment have been studied extensively. However, the studies mainly focused on the sensitivity of vegetation to acid precipitation and the effects of simulated acid rain on eco-physiological characteristics of vegetation, very few studies about the chemical properties of acid precipitation in forest ecosystem and the effect of acid deposition to soil and vegetation of forest ecosystem were done. Furthermore, most of these experiments were conducted indoors with strictly controlled conditions. Chemical properties of acid rain in evergreen broad-leaved forest of Simian Mountain and effects to soil and vegetation were studied in this paper according to the guidelines and technical manual for acid deposition monitoring network in East Asia (2001). In this experiment, the rainfall, throughfall and stemflow in evergreen broad-leaved forest in Simian Mountain were measured one year. The results are as follows: (1)The Chemical properties of acid rain in evergreen broad-leaved forest of Simian MountainThe results indicate that: The frequency of acid rain was high in Simian Mountain, which effected of high abundance of long-middle distance-transported acid pollutants and low concentration of alkaline dust in atmosphere. pH values vary between3.33 to 6.20, with an average of 4.45. The frequency of acid rain is 96.1%. The amount of acid rain representsabout 98%of total precipitation. The pH values show a remarkable seasonal variation, with more acid rain fall in winter than that in spring, autumn and summer. The SO42-+NO3-/NH4++Ca2+ ratio ranged from 0.9 to 1.3 was higher than that in northern China and southwest China (with the ranged from 0.4 to 0.7 and 1), this implied that the acid deposition was severe in Simian Mountain.The throughfall and stemflow changed greatly because of the canopy interception. The pH value of throughfall was lower than that of rainfall, and the pH value of stemflow was higher than that of rainfall. The electronic conductivity (EC) of through and stemflow was significantly increased. The pH and EC values of throughfall and stemflow exhibited a strong seasonal pattern. Compared to the atmospheric rainfall, the concentrations of SO42-, K+ in the through-fall and stem-flow in evergreen broad-leaved forests remarkably increased, the concentrations of NH4+, NO3- in the through-fall and stem-flow in evergreen broad-leaved forests decreased.Compared to the atmospheric rainfall, the concentrations of all ions in the through-fall and stem-flow in broad-leaved forests remarkably increased with an exception of NH+, and showed some seasonal trends. The concentrations of Ca2+, SO42-, Mg2+, Na+ , K+ , F-, Cl- in stemflow was more higher than those of in throughfall. Increase of the total ion amount in the rainfall in forest led to the unbalance of cation and anion load in the canopy of forest causing a large amount of nutrient elements leaching and losing. (2)The effect of acid rain on soil of the evergreen broad-leaved forest in Simian MountainIt was found that the pH value of soil was low at the monitoring forested sites, and the pH value of soil in layer A was higher than that of layer B. The base cation saturation (BS) in all sampled layers was less than those in Jinyun Mountain. The effective cation exchange capacity (CEC) was lower than those in Jinyun Mountain sample. The low content of calcium and the high content of aluminum in soils of Simian Mountain led to a high the ratio of Al3+/Ca2+, which was 30 to 40. The C/N ratio of soil was low, and declined with the soil depth, indicating that the organic matter was well decomposed under warm and rainy subtropical climate. The acidification of soil became more serious and the amount of base ions leached from the soils increased due to the long-term acid rain. All of these may led to theacidification of soil, which was harmful to forest ecosystem.(3) The effect of acid rain on...
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