鼎湖山酸沉降背景下主要森林类型水化学特征初步研究

雨水的水质在通过森林后会发生变化．如果雨水是酸性的，这种变化会更加明显．通过一年多时间在鼎湖山主要森林类型采样分析发现，鼎湖山大气降水pH值低，酸雨频率高；阔叶林穿透雨pH值比大气降水高，树干径流和地表水pH值比大气降水低，土壤自然酸化非常严重；混交林穿透雨和地表水酸度比大气降水低，树干径流酸度则大于大气降水；针叶林穿透雨和树干径流都有进一步酸化趋势，但地表水pH值比大气降水高．3种林型比较，阔叶林林冠缓冲能力最强，针叶林土壤缓冲能力最大．3种林型，林内降水和地表水养分N、P、K、Ca、Mg和Na含量除N外都明显高于大气降水．各林型树干径流对养分富集能力强于穿透水，养分在大气降水中的浓度低于在地表水中的浓度．针叶林林内降水比混交林和阔叶林养分含量高，但地表水中养分浓度比后两者低．从地表水的养分浓度看，阔叶林和混交林养分亏损更为严重．

A preliminary study on the chemical properties of precipitation, throughfall, stemflow and surface run-off in major forest types at Dinghushan under acid deposition

Studies on the chemical properties of precipitation, throughfall, stemflow and surface run off in major forest types at Dinghushan under acid deposition showed that the pH value of precipitation was about 4.90,and the frequency of acid rain was over 62%. In broad leaved forest, the pH value of precipitation was lower than that of throughfall, but higher than that of stemflow and especially the surface run off, indicating that the soil was naturally acidified. In mixed forest, both throughfall and surface run off had a higher pH value,but stemflow had a lower pH value than precipitation. The throughfall and stemflow were more acidified than precipitation in coniferous pine forest, but the surface run off had a higher pH value than precipitation. These results suggested that among the three major forest types at Dinghushan,the canopy of broad leaved forest had the highest buffering ability,whereas for the soil,the coniferous forest had the highest soil buffering capacity. The concentrations of nutrient elements, such as P, K, Ca, Na and Mg in the throughfall, stemflow and surface run off were higher than those in bulk precipitation in all forests at Dinghushan, some even 10 times higher, indicating that a large amount of nutrients were leached from the canopy. The concentrations of nutrient elements in stemflow were higher than those in throughfall in all forests, and the concentration of nutrient elements in surface water was higher than those in atmospheric rainfall. Coniferous forest had a higher concentration of nutrients in the throughfall and stemflow and a lower nutrient concentration in the surface run off than other forest types,which implied that nutrient loss was more serious in broad leaved and mixed forests than in coniferous forests.