EFFECT OF BIOLOGICAL PROCESSES ON GEOCHEMICAL CYCLING OF MATERIALS IN BIOSPHERE

对某些森林生态系统的物质循环过程进行了观测，并讨论了酸性沉降对物质循环过程的影响。林冠中有机化合物的积累、摄入、碱释放和排泄对酸性沉积物的组成和pH有强烈的影响。在落叶林下，穿透ph显著高于降雨ph，而针叶林下的穿透ph普遍低于降雨ph。显然，针叶树作为空气污染物的收集者更有效。油松的效率是混交林的3倍以上。森林地面0层表现出较强的ph缓冲作用，特别是在落叶林下。据估计，该地区的酸中和能力可达目前H^+负荷的20 - 30倍。另一方面，土壤溶液的ph值主要受硝化作用和碱交换现象等土壤过程的控制。到目前为止，森林生态系统中硫和氮的循环不受大气输入的影响，而是受森林生态系统特有的生化过程的自我控制。河流河道的流量和水质也受到林分和表层土壤生物过程的影响。此外，干沉降到雪表面的通量相当大，主要离子为30 ~ 100mumolc m^<-2> day^<-2>。冬季，酸性大气污染物在积雪中的积累和输送增强了其影响。

Observations on the material cycling in some forest ecosystems were conducted and the influences of acidic deposition on the processes were discussed. The composition and pH of acidic deposition were strongly modified by accumulation, intake, base release, and excretion of organic compounds from forest canopy. Under deciduous forests, throughfall pHs were significantly higher than rainfall pHs, but those under coniferous forests were generally lower than rainfall pHs. Apparently, conifers were more effective as the collector of air pollutants. The efficiency of Pinus strobus were more than three times of mixed deciduous forests. The O horizon of forest floor showed strong pH-buffering, especially under deciduous forests. It acid neutralizing capacity was estimated as large as 20 - 30 times of present H^+ load in the area under consideration. On the other hand, the pHs of soil solution were largely controlled by soil processes, such as nitrification and base exchange phenemena. The cycling of sulfer and nitrogen in the forest ecosystems was not, so far, affected by atmospheric inputs, but self-controlled by characteristic biochemical processes of the forest ecosystems. The discharge and water quality of stream channels were also affected by biological processes in forest stand and surface soil horizons. In addition, the flux of dry deposition onto snow surface was considerable, 30-100mumolc m^<-2> day^<-2> for major ions. The influence of acidic air-pollutants was enhanced by accumulation and transport in snow-pack during winter time.