| 土地利用变化对土壤硝化及氨氧化细菌区系的影响 |
| 摘要点击 2290 全文点击 1715 投稿时间：2010-06-20 修订日期：2010-11-22 |
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| 中文关键词 土地利用变化 活性氮 硝化势 氨氧化细菌 |
| 英文关键词 land-use type change reactive nitrogen nitrification potential ammonia-oxidizing bacteria(AOB) |
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| 中文摘要 |
| 以西藏高原相邻的原始森林、天然草原和农田土壤为研究对象，分别采用室内培养法和 nested PCR-DGGE技术，对比研究了这3个生态系统的土壤硝化势、硝态氮浓度以及土壤氨氧化细菌（AOB）菌群区系.结果表明，农田土壤的硝化势和硝态氮（NO-3-N）浓度显著高于相邻的草原和森林土壤，硝化势分别是森林和草原土壤的9倍和11倍，NO-3-N是农田土壤无机氮（Nmin）的主要成分，占无机氮的70%～90%.铵态氮（NH+4-N）则是森林和草原土壤中主要的无机氮形态.原始森林和天然草原间的硝化势和硝态氮浓度没有显著差异.原始森林的土壤AOB菌群数量、多样性及均匀度最低.天然草原生态系统转换为农田后，土壤AOB菌群的多样性和均匀度显著降低，但是农田土壤的AOB菌群结构仍与其前身草原生态系统有较高的相似性.原始森林的AOB菌群数量、多样性及均匀度最低直接导致了其硝化势最低；农田土壤的硝化势和硝态氮浓度最高意味着农田生态系统中优势AOB的活性最高.以上结果表明，土地利用变化导致土壤氮素内循环及其关键微生物AOB的多样性与活性均发生显著变化，这些变化会影响土壤环境质量以及生态系统的持续与稳定. |
| 英文摘要 |
| A comparative study was conducted to determine nitrification potentials and ammonia-oxidizing bacterial (AOB) community composition in 0-20 cm soil depth in adjacent native forest，natural grassland，and cropland soils on the Tibetan Plateau，by incubation experiment and by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA，respectively. Cropland has the highest nitrification potential and nitrate concentration among the three land-use types (LUT)，approximately 9 folds and more than 11 folds than that of the forests and grasslands，respectively. NO-3-N accounted for 70%-90% of inorganic N in cropland soil, while NH+4-N was the main form of inorganic N in forest and grassland soils. Nitrification potentials and nitrate concentrations showed no significant difference between native forest and grassland soils. The native forest showed the lowest nitrification potentials and the lowest AOB diversity and community composition among the three LUT. Conversions from natural grasslands to croplands remarkably decreased the AOB diversity and composition, but croplands remain high similarity in AOB community composition compared with grasslands. The minimal and the lowest diversity of AOB in native forests directly resulted to the lowest nitrification potentials compared to natural grasslands and croplands. From the fact of the highest nitrification potentials and nitrate concentrations in croplands indicated that there were the most substantial AOB with higher activity and priority. The results provide evidence that changes of land-use type can affect both soil nitrogen internal cycling process, the diversity，community and activity of AOB, which further affect soil environment quality and the long-term sustainability of ecosystems. |
