土壤有機氮形態對臺灣中部三種針葉林土壤氮礦化作用之影響

Effects of Soil Organic Nitrogen forms on Nitrogen Mineralization of Three Coniferous Forests Types in Central Taiwan

翁菁羚(Jing-Ling Weng)

指導教授 ： 關秉宗

共同指導教授 ： 王明光(Ming-Kuang Wang)

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.02243

摘要

森林生態系內，氮常成為植物生長的限制因子。而可供植物利用的無機態氮來自於氮礦化作用的進行，因此評估森林土壤的氮礦化潛勢，可作為管理林地生產力的指標。本研究目的在於研究造成塔塔加地區三林區內氮礦化速率差異的主要因子，期望將來能夠藉由控制林地氮礦化速率來提高林地生產力。本研究先進行一年的現地孵育試驗以瞭解雲杉林區、鐵杉林區以及二葉松林區氮礦化速率的差異，結果顯示雲杉林區的氮礦化速率最高。而後分析三林區土壤的基本理化性質及有機態氮組成，再進行短期室內孵育以評估各林區的氮礦化潛勢及氮礦化速率，以探討礦化基質與氮礦化作用的關係，最後再以此為依據討論造成三林區氮礦化速率差異的主因。觀察各樣點四週室內孵育的無機態氮濃度與土壤基本理化性質及氮劃分間的相關性，四週礦化出的無機態氮濃度與全碳及陽離子置換容量呈正相關(r2=0.88, 0.79, p<0.01)，與黏粒含量呈負相關(r2=-0.71, p<0.01)。而氮劃分方面，除了水解未知氮，與各類型有機態氮皆呈正相關(r2=0.77~0.87, p<0.01)。除此之外，不同於傳統簡單函數模式估算法，本研究利用三參數漸進混合效應模式估算四週無機態氮濃度隨時間的變化，估算結果顯示所有樣點氮礦化潛勢在時間無限大時會趨近一個定值，而影響氮礦化速率的最顯著的因子為胺基酸態氮含量，此外本模式較傳統估算法多了初始礦化濃度的估算，而影響初始礦化濃度最顯著的因子為全碳量。綜合以上結果與其他在塔塔加地區的相關研究，探討造成現地雲杉林區氮礦化速率較高的原因。由室內孵育結果顯示，雲杉林區與二葉松林區的全碳量及各有機氮的含量皆比鐵杉林區高，因此造成礦化速率較高。而室內孵育結果顯示二葉松林區因含有較高的胺基酸態氮而使氮礦化速率較雲杉林區高，然現地的雲杉林區土壤較二葉松林區有較高的通氣量及含水量，使得硝化速率較快，因此造成現地的氮礦化速率以雲杉林區最高。

關鍵字

土壤有機氮 ； 氮劃分 ； 氮礦化 ； 非線性混合效應模式

並列摘要

Nitrogen mineralization is the soil process which organic nitrogen converted to inorganic nitrogen. The purposes of this study are to investigate the effects of soil organic N forms on N mineralization of three coniferous forests, Morrison spruce forest (Picea morrisonicola Hay.), Chinese hemlock forest (Tsuga chinensis var. formosana), Taiwan red pine forest (Pinus taiwanensis Hay.) in the Ta-Ta-Chia area, central taiwan. First, the N mineralization rate of mineral soil (10-20 cm) in spruce, hemlock and pine forest sites was monitored by field incubation for one year. Secondly, the content of different organic N forms, including total hydrolysable N, acid insoluble N, ammonium N, amino sugar N, amino acid N, hydrolysable unknown N, of three forest soils was analyzed. Thirdly, a short term lab incubation under 25oC and 55% WHC was used to determine the kinetics of N mineralization of three forest soils. The N mineralization potential and N mineralization rate constant is estimated through fitting N mineralization curve by the three parameter asymptotic mix effect model. The relationship between different organic N forms with N mineralization under lab incubation was evaluated to find out the major factor for soil N mineralization. Finally, the observation in lab incubation was adapted to explain the effect of different N species on the N mineralization in field. The results of lab incubation show the most important factor influencing the N mineralization rate is the content of amino acid N. However, the N mineralization rate by field incubation showed following trends : spruce forest > pine forest ≒ hemlock forest. Although the content of amino acid N in pine forest was higher than that of spruce forest, the N mineralization rate was still lower than spruce forest. It may be because spruce forest soils has better aeration and higher water content leading higher mineralization and nitrification rates.

並列關鍵字

soil organic nitrogen ； nitrogen fraction ； N mineralization ； nonlinear mix-effect model

參考文獻

林珈吟。2003。塔塔加地區土壤中氮的礦化與硝化作用。國立臺灣大學森林學研究所碩士論文。

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