重庆缙云山地区森林土壤酸化特征

通过在2010～2012年8月份对重庆缙云山4种典型林分土壤进行野外取样和室内分析，研究了酸沉降对研究地森林土壤酸化的影响，并从多角度深入分析了4种林分土壤在时间和空间上的酸化机理。结果表明：（1）在常年酸沉降的影响下，缙云山森林土壤酸化现象非常严重，pH值较低，表层土壤pH值为387~447，4种林分土壤pH值都随土层加深递增；（2）4种林分有机质含量相差较大，灌木林最高（377 g/kg），毛竹林最低（1144 g/kg），且随土层增加而降低，这主要是受枯落物类型和来源的影响；（3）由于长期酸雨淋溶作用，4种林分土壤CEC含量均较低为1276~1973 cmol/kg，表层含量最高，随土层加深递减；（4）4种林分Al3+含量均较高，阔叶林（4097 mmol/kg）>灌木林（3132 mmol/kg）>针阔混交林（3006 mmol/kg）>毛竹林（2615 mmol/kg）。Al3+含量与土壤pH值呈显著负相关关系

ANALYSIS ON THE FOREST SOIL ACIDIFICATION AND MECHANISMS IN CHONGQING JINYUN MOUNTAIN

In order to study the effects of acid deposition on the soil acidification, this paper analyzed the conditions of acid deposition of Chongqing area and the soil acidification trend of four kinds of typical forest (shrubwood, evergreen broad leaf forest, mixed coniferous broad leaved forest and Phyllostachys pubescens forest) by the method of soil sampling and laboratory analysis from 2010 to 2012 in August of each year. This study divided the soil of the four kinds of typical forests into four layers according to the soil forming process and analyzed the physical and chemical properties, respectively. The results showed as follows. (1) Although the sulfur dioxide levels in the atmosphere was going down with each passing year and the nitrogen dioxide levels was in a very steady state, the acid rain condition was very serious in Chongqing area and indicated that the type of acid rain was turning to mixed acid rain from typical sulfate acid rain. (2) Because of the effects of acid deposition for decades, the soil acidification phenomenon was very serious in the four kinds of typical forest. The surface soil pH was various from 387 to 447 and with the increase of soil depth, soil pH value decreased. All stands surface soil pH values reduced year by year, but the subsurface soil layers pH values of evergreen broad leaf forest and mixed coniferous broad leaved forest increased. (3) The organic matter content existed significant difference between the four forests, indicating that the stand type had a very important effect on soil organic matter. Because the litter is the main source of organic matter, the surface soil had the highest content and decreased with the soil depth. The content of surface soil of four typical forests were ranked as follows: 〖JP2〗shrubwood （8845 g/kg）> mixed coniferous broad leaved forest (5565 g/kg) > evergreen broad leaf forest (4087 g/kg) > Phyllostachys pubescens forest (2469 g/kg). (4) Under the influence of the leaching of acid rain for a long time, cation exchange capacity (CEC) was very low. For the same kind of stand, the change trend of cation exchange capacity was the surface soil had the highest content and decreased with the depth of soil. The content of CEC of surface soil of four typical forests were ranked as follows: evergreen broad leaf forest (2765 g/kg) > shrubwood （2319 g/kg）> mixed coniferous broad leaved forest (1971 g/kg) > Phyllostachys pubescens forest (1519 g/kg). (5) The content of exchangeable Al3+ of the four typical forests was very high under the effect of acid rain for a long time, and ranked as follows：evergreen broad leaf forest（4097 mmol/kg）> shrubwood（3132 mmol/kg）> mixed coniferous broad leaved forest（3006 mmol/kg）> phyllostachys pubescen（2615 mmol/kg）.In this study, there was a negative correlation between exchangeable Al3+ and soil pH