川南地区森林养分输入量与大气降水的关系

Forest nutrient input from rainfall in southern Sichuan

在长期经营过程中，对川南地区的人工林，多注重砍伐（养分输出）而忽视养分输入（施肥），导致了土壤生态系统的养分失衡，以及土壤的酸化和贫瘠化。大气降水是目前该地区林地生态系统的主要养分来源。对川南地区森林生态系统中水分输入的分析结果表明：pH值随降水量的增加而增大，小雨呈酸性，中雨和大雨趋于中性；氮、磷、钾、镁、硅的质量浓度随降水量的增加而降低，降水中养分质量浓度的大小排序为：钙〉氮〉钾〉镬〉磷〉硅；川南林区降水中养分的输入量：氮为12．27kg·hm^-2a^-1，磷为0．84kg·hm^-2·a^-1，钾为12．27kg·hm^-2·a^-1，钙为23．90kg·hm^-2·a^-1，镁为2．53kg·hm^-2·a^-1，硅为0．33kg·hm^-1·a^-1。这些营养元素输入总量为52．26kg·hm^-2·a^-1。与国内外其他地区相比，处于中上水平；降水中硅的年输入量仅占竹材硅输出量的1．2％～5．5％。

In silviculture, timber cutting （nutrient output） has been studied extensively, whereas nutrient input （fertilization） has been ignored. This has led to unbalanced nutrient concentrations in soil ecosystems as well as acidic and barren soils. In southern Sichuan, an important tree plantation base in China, rainfall is the main nutrient input source for the forest system. Results of a rainfall input analysis indicated that pH increased with rainfall, was slightly acidic with light rain, and was neutral with medium and heavy rain. Also, N, P, K, Mg and Si decreased with rainfall in the order of： Ca 〉 N 〉 K 〉 Mg 〉 P 〉 Si. The 52.26 kg· hm^-2·a^-1 of nutrient input from rainfall in the forests of southern Sichuan was partitioned as： N 12.39 kg·hm^-2 ·a ^-1, P 0.84 kg·hm^- 2 ·a ^-1, K 12.27kg·hm^-2·a^-1, Ca23.90kg·hm^-2·a^-1, Mg2.53 kg·hm^-2·a ^-1, and Si0.33 kg·hm^-2·a^-1 with nutrients higher than average. In addition, the annual Si input from rain was 1.2% -5.5% of the Si output of timber.