中国植被对氮和盐基阳离子吸收速率及其在土壤酸化中的作用

植被对氮和盐基阳离子的吸收是除酸沉降外另一个重要的土壤酸度来源.本研究基于中国植被的净初级生产力和元素化学组成确定了中国植被对氮和盐基阳离子的吸收速率.结果表明中国东南部,包括东北、华北、华东和华南地区,植被对氮的吸收速率普遍较低,而在中国的西北部吸收速率较高,并且由东南向西北逐渐递减对盐基阳离子来说,吸收速率较高(>2.0 keq·(hm²·a)^-1)的植被有亚热带、热带常绿阔叶林、温带石灰岩落叶阔叶林、温带落叶灌丛和亚热带、热带稀树灌木草原等,它们主要分布在华北西北部、云南南部和海南岛西部,而吸收速率较低(<0.5 keq·hm²·a)^-1)的植被则主要包括分布在东部亚热带地区的常绿针叶林以及分布在西部干旱地区的各种荒漠和草原尽管中国大多数地区不会因为植被吸收而造成显著的土壤酸度增加,但在少数地区,植物吸收造成的土壤酸度输入却不容忽视(>0.5 keq·(hm²·a)^-1)由于这些地区植被吸收造成的土壤酸度输入已经大于或相当于目前的酸沉降水平,而且两者之和也超过了土壤的风化速率,这些地区可能面临土壤的酸化问题.

Vegetation Uptake of Nitrogen and Base Cation in China and Its Role in Soil Acidification

Vegetation uptake of nitrogen and base cation, as well as acid deposition, is an important source of soil acidity. Based on the net primary productivity and elemental composition, the uptake rate of nitrogen and base cation was estimated for each vegetation type in China. Result showed that the uptake rate of nitrogen was commonly low in southeast China and high in northwest China, and decreased gradually from southeast to northwest in northwest China. In addition, the uptake rate of base cation was very high (>2.0 keq·(hm²·a)^-1) for subtropical/tropical broadleaf evergreen forest, temperate limestone broadleaf deciduous forest, temperate deciduous shrub, and subtropical/tropical savanna in the northeast of Huabei Plain, the south of Yunan province, and the west of Hainan Island respectively, and low (<0.5 keq·(hm²·a)^-1) for subtropical evergreen coniferous forest in east China and deserts and steppes in arid region of west China. Although vegetation uptake caused no increase of soil acidity in almost all areas in China, the acidity input caused by vegetation uptake was quite high (>0.5 keq·(hm²·a)^-1) and even higher than the current acid deposition in some areas, where soil acidification might happen because the total acidity input exceeded the alkalinity produced by soil weathering.