半干旱区土地利用方式对土壤碳氮矿化的影响

发布时间：2019-04-28 14:43

【摘要】：通过研究云雾山草原自然保护区草地、农地、灌木林土壤有机碳和氮的含量和矿化特征,分析了半干旱黄土区不同土地利用方式对土壤碳氮循环的影响。结果表明,土壤有机碳和全氮平均含量在草地转变为农地后分别降低了53%和64%,在转变为灌木林地后分别降低了54%和44%。不同土地利用方式下土壤有机碳矿化速率均随土层深度的增加逐渐降低,降幅介于29%~46%之间;有机碳矿化比例则逐渐增加,增幅介于45%~67%之间。土壤氮素矿化速率、矿化比例和硝化速率均随土层加深逐渐降低,而且0~20 cm土层氮素矿化体现为硝化过程和铵态氮的固定作用,且硝化过程占主导作用;40~80 cm土层硝化过程和铵化过程的比例接近,表明深层土壤氮素矿化由硝化过程和铵化过程共同主导。草地转化为农地和灌木林地后有机碳矿化速率显著降低,其降低幅度随土层加深逐渐减小;但有机碳矿化比例则有所增加,其增幅随土层加深而增大。草地利用方式发生变化后,土壤氮素矿化速率和矿化比例、硝化速率和铵化速率均显著降低,这些指标在表层土壤以草地转变为农地后降低较多,在深层土壤以草地转变为灌木林地降低较多。综上,半干旱黄土区草地转变为农地和灌木林地后,土壤碳氮循环强度和有效性显著降低,因此应避免草地向其它利用方式的转变。
[Abstract]:The contents of organic carbon and nitrogen and mineralization characteristics of soil organic carbon and nitrogen in grassland, farmland and shrub forest in Yunwu Mountain grassland Nature Reserve were studied. The effects of different land use patterns on soil carbon and nitrogen cycle in semi-arid loess region were analyzed. The results showed that the average contents of soil organic carbon and total nitrogen decreased by 53% and 64% in grassland and 54% and 44% in shrub land, respectively. With the increase of soil depth, the mineralization rate of soil organic carbon decreased by 29% ~ 46%, and the ratio of mineralization of organic carbon increased by 45% ~ 67% with the increase of soil depth under different land use patterns, and the mineralization rate of soil organic carbon decreased by 29% and 46% respectively with the increase of soil depth. Soil nitrogen mineralization rate, mineralization ratio and nitrification rate decreased gradually with the deepening of soil layer, and nitrogen mineralization in 0 ~ 20 cm soil layer showed nitrification and ammonium fixation, and nitrification played a leading role. The ratio of nitrification process to ammonium process in 40 ~ 80 cm soil layer is similar, indicating that nitrogen mineralization in deep soil is dominated by nitrification process and ammonium process. The mineralization rate of organic carbon decreased significantly after grassland was transformed into farmland and shrub land, but the ratio of mineralization of organic carbon increased with the deepening of soil layer, and the rate of mineralization of organic carbon increased with the deepening of soil layer, while the rate of mineralization of organic carbon decreased with the deepening of soil layer. The soil nitrogen mineralization rate, mineralization ratio, nitrification rate and ammonium rate decreased significantly after the change of grassland utilization pattern, and these indexes decreased more after the change from grassland to farmland in the topsoil. In the deep soil, the change from grassland to shrub land decreased more. On the whole, the intensity and availability of soil carbon and nitrogen cycle decreased significantly after grassland was transformed into farmland and shrub land in semi-arid loess area. Therefore, the change from grassland to other utilization modes should be avoided.
【作者单位】：西北农林科技大学资源环境学院;中国科学院水利部水土保持研究所黄土高原土壤侵蚀与旱地农业国家重点实验室;
【基金】：国家自然科学基金项目(41471244) 省自然科学基金项目(2015JQ4103)
【分类号】：S153.6

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