添加葡萄糖对杉木人工林土壤氮素转化及净矿化和硝化的影响

以亚热带杉木人工林为研究对象,研究添加葡萄糖(C量水平分别是0,100,300,1 000,2 000,5 000 mg·kg-1)对土壤氮含量、氮素矿化和硝化的影响。结果表明,葡萄糖添加降低土壤无机氮含量和比例,硝态氮的降低幅度大于铵态氮;但是没有降低可溶性有机氮(SON)和pH值,甚至提高SON的比例。添加葡萄糖降低氮素净矿化和硝化速率,氮素矿化作用受到抑制。结果显示,随着葡萄糖添加,亲水性氮所占比例显著降低,这与氮的固持和转化有关,导致SON比例增加;分析表明,硝态氮和可溶性有机氮在提取液全氮中所占比例成显著的线性负相关关系(R2=0.902)。研究发现,1 000 mg·kg-1的葡萄糖C添加量可能是影响杉木人工林土壤氮素转化的分界点。

Effects of Glucose Addition on Soil Nitrogen Transformation and Net Mineralization and Nitrification in Chinese Fir Plantation

In view of the significant role of litter played in regulating forest soil nitrogen transformation, simulating the influence of matrix carbon sources on nitrogen transform in the subtropical coniferous forest acid soil is helpful to deeply understand the mechanism between carbon and nitrogen. The effects of glucose addition (as C of 0, 100, 300, 1 000, 2 000, and 5 000 mg·kg^-1) on soil nitrogen content, nitrogen mineralization and nitrification were studied in the soil under subtropical Chinese fir plantation. The results showed that the glucose addition reduced the soil inorganic nitrogen content and proportion in total soluble nitrogen, and the nitrate nitrogen decreased more than ammonium nitrogen; but the decrease of soluble organic nitrogen (SON) and pH was not found, even the ratio of SON in total soluble nitrogen increased. Glucose addition decreased the net nitrogen mineralization and the nitrification rates for nitrogen mineralization were inhibited. The results showed that hydrophilic nitrogen proportion decreased significantly with the addition of glucose, which was related to nitrogen immobilization and transformation to result in the enhancement of SON proportion. Correlation analysis showed that there was a significantly negative linear relationship (R² = 0.902) between the proportions of nitrate and dissolved organic nitrogen in the total nitrogen of the extract from soil, which indirectly give a evidence of glucose likely promoting the nitrate retaining and transformation by microorganisms involved in soil. The research discovered that the glucose amount (as C) of 1 000 mg ·kg^-1 was the threshold affecting the nitrogen transforms in forest soil under subtropical Chinese fir plantation.