塔塔加長期生態研究地區 四種植生土壤之氮礦化及硝化作用

Abstract

無機態氮（硝酸態氮和銨態氮）是植物重要的養分之一，尤其對於不施肥的森林土壤更具重要性，而氮礦化及硝化現象則是重要氮肥力指標，但目前多用少量變數或單一時間(當月或當季)去研究礦化和硝化作用，忽略氣候因子的綜合影響。有鑑於無機態氮對於森林的重要性，故本研究目的為綜合多量、不同時間點的氣象因子，以進一步研究森林土壤的礦化和硝化作用。研究以台大實驗林-塔塔加之四主要植被區草原、鐵杉、雲杉和二葉松為試驗區，阿里山氣象站的氣象資料為材料，並透過逐步迴歸法篩選出最主要的影響氮礦化和硝化的氣候因子，後透過複因子迴歸建立推估模式，此外並檢視能否用土樣之pH、EC和土壤含水量等簡易偵測之項目研究土壤氮礦化及硝化作用。 試驗結果顯示利用氣候因子推估無機態氮含量，鐵杉和雲杉的銨態氮濃度有適合的氣候因子可以建立相關高的迴歸式，鐵杉的硝酸態氮主要與採樣當月~前一月的氣壓累積值有關（R2 =0.97），雲杉的硝酸態氮與採樣當月~前一月的濕度累積值有關（R2 =0.93），草原和二葉松的氮濃度主要與採樣前一~二月的雨量有關（R2 >0.90）。而利用氣候因子推估土壤礦化和硝化速率結果顯示，草原的礦化速率主要與採樣當月~前一月的溫差累積值有關（R2 =0.99），硝化速率主要與採樣當月的降水日數有關（R2 =0.92），鐵杉的礦化速率則和採樣前一個月的平均最大風速有關（R2 =0.99），雲杉和二葉松的礦化和硝化速率則和採樣前2個月的降雨比率有關（R2 >0.90）。利用pH、EC和含水量可建立鐵杉和雲杉的硝酸態氮和無機態氮濃度的迴歸式（R2 >0.74）。

Ammonium and nitrate are important plant nutrients of plants. Especially to forest soil of no fertilization. Nitrogen mineralization and nitrification are important index of fertility. But now people often use many number of variables or single period to study mineralization and nitrification, and ignore the synthetically infections of climate. Respecting the importance of inorganic nitrogen to forest, the aim of this study is using multiple kinds and variable climate factors, to discuss the mineralization and nitrification of forest soil further. The determination of experiment area according to the four main vegetation areas of Ta-Ta-Chia forest. The test result showed that we could use the climatic factors to estimate the inorganic nitrogen content. The ammonium concentrations of hemlock and spruce soils have the suitable climatic factors to establish a high correlation regression equation.The nitrate concentration of hemlock soil is mainly related with the pressure accumulation from sampling month to preceding of sampling same month（R2 =0.97）.The nitrate concentration of spruce soil is mainly related with the humidity accumulation from sampling month to preceding sampling same month（R2 =0.93）.The nitrogen concentration of grassland and pine soil is mainly related with the precipitation preceding ~ first two month（R2 ＞0.90）.We also could use the climatic factors to estimate the soil mineralization and the nitration rate.The net mineralization rate of grassland soil is mainly related with the temperature difference accumulation of the sampling month ~ preceding of the sampling month（R2 =0.99）.The net nitrification rate of hemlock soil is mainly related with the rainy days of the sampling month（R2 =0.92）.The net mineralization rate of hemlock soil is mainly related with the average maximum wind speed of the preceding of the sampling month（R2 =0.99）.The net mineralization rate and net nitrification rate of spruce and pine soils are mainly related with the rains ratio of the first two of the sampling month（R2 =0.99）.Using pH, EC and the water content, we may establish the regression equation of hemlock and spruce's nitrate and inorganic nitrogen concentration.