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通过野外模拟试验,选择中亚热带针叶林(杉木林)和阔叶林(浙江桂林和罗浮栲林)森林生态系统,设3个施氮水平CK(对照)、低氮〔30 kg(hm2·a)〕和高氮〔100 kg(hm2·a)〕及2个凋落物处理,研究施氮对土壤主要形态氮质量分数的影响、动态变化及凋落物在其中的作用.结果表明:与CK相比,高氮处理可瞬时(3 d)提高森林土壤氮质量分数,但施氮后持续效应的影响降低.与保留凋落物相比,去除凋落物在施氮的持续效应中,可降低阔叶林土壤w(铵态氮)18.2%,而杉木林土壤的氮质量分数则略有升高.去除凋落物下施氮的持续和瞬时效应可增加各种林下土壤的w(硝态氮),其中浙江桂林土壤w(硝态氮)分别增加58.9%和38.2%,罗浮栲林土壤分别增加7.0%和30.0%,杉木林土壤分别增加-17.1%和9.0%.可见凋落物在施氮连续事件中存在复杂的短期和长期相互影响.阔叶林土壤w(SON)(SON为可溶性有机氮)较高,并且其微生物w(SON)及其占微生物w(TN)的比例高于杉木林土壤,而杉木林土壤微生物w(铵态氮)及其占微生物w(TN)的比例高于阔叶林土壤.
Through the field experiment, the forest ecosystem of middle-subtropical coniferous forest (Cunninghamia lanceolata) forest and broad-leaved forest (Zhejiang Guilin and Luofuangliu forest) were selected and three CK (control) and 30 kg (hm2 · A)] and high nitrogen [100 kg (hm2 · a)] and two litters were used to study the effects of nitrogen application on soil nitrogen content, dynamic changes and litter in the soil. The results showed that: Compared with CK, the treatment with high nitrogen could increase the nitrogen content of forest soil instantaneously (3 d), but the effect of persistent effect decreased after the application of nitrogen.Compared with the retained litter, the removal of litter in the persistent effect of nitrogen application The content of w (NH4 + -N) in broad-leaved forest decreased by 18.2%, while that in Cunninghamia lanceolata forest increased slightly.The sustained and transient effects of nitrogen removal under litter could increase the contents of w (nitrate The soil w (nitrate nitrogen) increased by 58.9% and 38.2% respectively in Guilin, Zhejiang Province and 7.0% and 30.0% respectively in the Loessial Fractional Plantation, and increased by -17.1% and 9.0% in the Chinese fir plantation respectively. There were complex short-term and long-term interactions in the succession of nitrogen application. The soil SON (SON) of broadleaved forest was higher than that of soluble organic nitrogen , And the proportion of soil microbial biomass w (SON) and microbial biomass w (TN) was higher than that of Chinese fir plantation. However, the ratio of soil microbial biomass w (ammonium nitrogen) and microbial biomass w (TN) soil.