重庆缙云山酸雨区森林土壤酸缓冲机制及影响因素

Acidic Buffering Capability and Its Influencing Factors of Typical Forests Soil in Jinyun Mountain,Chongqing

为探讨酸雨区森林土壤的酸缓冲机制,采集重庆缙云山4种典型林分(针阔叶混交林、常绿阔叶林、毛竹林和灌木林)不同土层土壤样品,研究森林土壤酸缓冲特性及其影响因素。结果表明:①同一土壤在不同的pH阶段其酸缓冲能力相差很大,这是由于土壤不同缓冲机制所造成的。当pH>3.0时,土壤中起主要缓冲作用的是土壤有机质、CEC、交换性Al 3+等;当pH<3.0时,土壤的主要缓冲机制为土壤矿物质的风化,土壤pH成为影响缓冲作用的主要因素。②在pH>3.0时,不同土壤酸缓冲能力相差较大,4种林分土壤平均缓冲能力大小为灌木林(25.58mmol/kg)>常绿阔叶林(23.81mmol/kg)>针阔叶混交林(19.43mmol/kg)>毛竹林(17.12mmol/kg),且同一林分表层土壤酸缓冲能力大于下层土壤。③当pH<3.0时,所有土壤的缓冲能力都急剧增强,pH越低,土壤酸缓冲能力越强,在同一pH阶段不同土壤酸缓冲能力相近。④按照对酸害容量划分,4种林分土壤全部属于易受害、稍易受害土壤,酸沉降极易对植物造成伤害,强烈建议对缙云山森林土壤进行改良,提高其土壤pH值和酸缓冲能力,同时,加大对环境的监控,减小酸雨发生频率。

In order to study the buffer mechanism of forests soil in acid rain region,four forests soil（mixed woods,broadleaf forests,bamboo forests and shrub forests）were studied in the Jinyun mountain of the Three Gorges Region through acid-base titration.The results showed that：①The soil buffering capability was various with the change of pH due to the mechanism of buffering.When pH3.0,organic matter,CEC and exchangable Al 3＋were the main soil buffer compounds,but when pH 3.0,the main buffering mechanism was weathering of the soil minerals,so soil pH became the mian influencing factor.②When pH 3.0,there was a large diffence between the soil buffering capability.The order of average values of siol pH buffering capacity of the four typical forest stands was shrub forests（25.58mmol/kg）broadleaf forests（23.81mmol/kg）mixed woods（19.43mmol/kg）bamboo forests（17.12mmol/kg）,and the capacity of surface layer was larger than that of subsurface layer.③When pH3.0,the buffering capability of all soils was becoming strongly considerablely.And it was becoming stronger with the decrease of soil pH.④According to the classification of acid-damage intensity capacities of soil,all soils belonged to vulnerable and slightly vulnerable.So the plants growing on them were easy to be hurt by the acidic precipitation.Therefore,the soil should be improved their pH and soil buffering capability,enhanced environmental quality monitoring and reduced the frequency of acid rain.