The Buffering Capacity Of Acid Rain And It's Chemical Composition Research Of Common Species Forest Litter Leaves In Subtropical Area

Because of the rapid development of economic society, the using of fossil fuel has increased greatly, and with more and more oxysulfide and nitrogen oxides released, which produced sulfuric acid and nitric in the atmosphere, forming acid rain and producing a series adverse effects on the ecological system. The acid rain is one of the world hotspots. Its damage to the forest ecosystem has been widely attentioned and consensus has been formed. But it still hasn't got enough attention to the research of forest ecological system's feedback mechanism to acid deposition.By laboratory leaching experiments, the role of forest litter as an acid-base buffering system was assessed by 9 common plantation from subtropical areas in China : Michelia chapensis, Elaeocarpus decipiens, Schima superb, Cyclobalanopsis glauca, Photinia serrulata Lindl, Castanopsis sclerophylla, Cinnamomum camphora,Pinus massoniana and Cunninghamia lanceolata. Based on the data, chemical characteristics of Schima superba , Elaeocarpus decipiens , Michelia chapensis and Pinus massoniana was studied in order to find out the effect of litter as a strong acid-base buffering system.The results showed that: (1) Forest litter has a certain buffering on acid rain. By clustering analysis of buffering capacity, the nine kinds of litter could be divided into three categories: Cinnamomum camphora, Michelia chapensis, Photinia serrulata Lindl as the first class; Elaeocarpus decipiens, Pinus massoniana as the second class; Schima superba, Cunninghamia lanceolata, Castanopsis sclerophylla, Cyclobalanopsis glauca as the third class. Elaeocarpus decipiens showed the different buffering capacity to acid rain. Its litter could make the pH of their living environment lower, which was disadvantageous to other organisms; Michelia chapensis showed a stronger buffering capacity than other species and its litter could be a good acid-base buffering system.(2) The buffering capacity of litter was relevant to its own pH. In low acidity, the higher pH litter had a stronger buffering capacity. (3) According to the data of Schima superb, Elaeocarpus decipiens, Michelia chapensis and Pinus massoniana, the four kinds litters which had different buffering capacity had the same distribution mode of base cations: K> Mg > Ca > Na.The base cation (K⁺,Ca²⁺,Na⁺,Mg²⁺) was the most important inorganic cations that could control the pH of biological materials. The concentration of base cations in litter was Consistent to its buffering capacity.(4)The eluviation of Ca²⁺, K⁺, Mg²⁺ is a reason for litter's buffering capacity. Different acidity processing had an obvious influence on their eluviation. The lower pH was, the easier base cations leached.(5) However, the inorganic composition in litter couldn't explain its buffering mechanism completely. It's the joint effort of its inorganic and organic ingredients. Some organic ingredients (e.g. alkaloids) also participated in the buffering process of acid rain.