- 學位論文
塔塔加地區土壤中氮的礦化和硝化作用
Soil nitrogen mineralization and nitrification in the Ta-Ta-Chia district
摘要
本研究目的是在探討塔塔加高海拔森林生態系試驗地中，A層 ( 10-20 cm ) 土壤中無機態的銨態氮與硝酸態氮濃度變化，並且估測土壤中無機態氮素的淨礦化速率和淨硝化速率，以及一些環境因子對無機態氮生成的影響。研究時間從2002年的3月至2003年的3月，共採集12次，每次採樣皆三重覆。試驗地分為高山草原 ( 玉山箭竹及紅毛杜鵑灌叢 ) 、台灣鐵杉林區及台灣雲杉林區三個試驗地，並利用野外埋藏袋孵育方法測定土壤中淨礦化及淨硝化速率。結果顯示，土壤中的銨態氮含量，在高山草原區介於 0.79 ~ 12.23 mg N kg -1 之間，台灣鐵杉林區介於 0.96 ~ 16.99 mg N kg-1 之間，雲杉林區則介於 0.71 ~ 9.02 mg N kg-1 之間 ; 土壤硝酸態氮濃度方面，高山草原區介於 0.1 ~ 12.07 mg N kg-1 之間，台灣鐵杉林區介於 1.43 ~ 14.92 mg N kg-1 之間，雲杉林區則介於 8.34 ~ 35.65 mg N kg-1 之間，其中硝酸態氮濃度以雲杉林區的較高。 另外高山草原區的土壤淨礦化速率介於 -0.20 ~ 0.25 mg N kg-1 d-1之間，台灣鐵杉林區介於 -0.32 ~ 0.48 mg N kg-1 d-1之間，雲杉林區則介於 0.23 ~ 5.03 mg N kg-1 d-1之間 ; 高山草原區的土壤淨硝化速率介於 -0.26 ~ 0.23 mg N kg-1 d-1之間，台灣鐵杉林區介於 -0.37 ~ 0.53 mg N kg-1 d-1之間，雲杉林區則介於 0.31 ~ 4.86 mg N kg-1 d-1之間，三個試驗區中以雲杉林區的淨礦化及淨硝化速率為最快，最可能的影響因子包括土壤碎石含量 ( > 2 mm ) 與微生物活性。雲杉林區的總礦化速率對總氮濃度的比例也是三個試驗區中最高。
並列摘要
The objectives of this study were to measure the variation of inorganic nitrogen ( ammonium and nitrate ) concentrations in the soil A horizon ( 10-20 cm depth ), and to determine the net nitrogen mineralization and nitrification rates at Ta-Ta-Chia site of high elevation forest ecosystem. The period of study was from March, 2002 to March, 2003, there were twelve times of sample collections in triplicated of each sampling. The influences of climate and rainfall also were under consideration. The three study sites were covered with different vegetations, including grassland ( Yushania niitakayamensis and Rhododendron rubropilosum Scrub type ), hemlock ( Tsuga chinensis var. formosana ), and spruce ( Picea morrisonicola ) stands. An in-situ buried bag approach was employed to estimate the rates of net N mineralization and nitrification. The soil ammonium concentrations ranged from 0.79 to 12.23 mg N kg-1 soil in grassland, 0.96 to 16.99 mg N kg-1 soil in hemlock, and 0.71 to 9.02 mg N kg-1 soil in spruce stands. Soil nitrate concentrations of grassland, hemlock and spruce ranged from 0.1 to 12.07, 1.43 to 14.92 and 8.34 to 35.65 mg N kg-1 soil, respectively. There were shown a trend of higher soil nitrate concentrations in spruce stand. On the other hand, the net mineralization rate ranged from -0.20 and 0.25 mg N kg-1 d-1 in grassland, -0.32 to 0.48 mg N kg-1 d-1 in hemlock, and 0.23 to 5.03 mg N kg-1 d-1in spruce stand. The net nitrification rates in grassland, hemlock and spruce ranged from -0.26 to 0.23, -0.37 to 0.53 and 0.31 to 4.86 mg N kg-1 d-1 , respectively. Rates of net N mineralization and nitrification, and the ratio of total net N mineralization amount to total nitrogen content in spruce site were higher than those in grassland and hemlock sites. The possible factors influenced these N variations included soil N content, amounts of pebbles ( > 2 mm ) and microbial activity.