森林立地学会誌　森林立地49(2), 2007, 123〜131

Jpn.J.For.Environment 49(2), 123−131  2007

 

森林土壌における気候帯別の窒素無機化

−土壌理化学性，気温，土壌型による現地窒素無機化速度の推定−

 

平井敬三^＊・金子真司^＊＊・高橋正通^＊＊

^＊森林総合研究所東北支所・^＊＊森林総合研究所立地環境研究領域

 

日本の気候帯を代表する森林の表層土壌中の現地窒素無機化速度および無機化量を把握することを目的に，レジンコア法による野外培養法で窒素無機化速度を測定した。現地窒素無機化速度や無機化量は温帯土壌で大きく，亜寒帯や亜熱帯土壌で小さかった。現地窒素無機化率は亜寒帯から暖温帯へと大きくなった。一方，室内培養による窒素無機化速度や無機化率は亜寒帯の土壌で高く，気温が高い環境下の土壌ほど小さくなった。室内培養による窒素無機化速度は全窒素含有率と有意な正の相関が認められた。室内培養による窒素無機化速度と，現地と室内培養における積算気温の比から求めた現地の窒素無機化ポテンシャルは現地窒素無機化速度に比べて大きく，より寒冷で室内培養温度と現地の温度差が大きい積算気温比が小さい土壌ほど，窒素無機化ポテンシャルと現地無機化の速度比が大きかった。全窒素含有率，積算気温比および土壌型を要因とした重回帰モデルから現地窒素無機化速度を推定した結果，多くの土壌では推定値と実測値との関係は良好であった。このことから，土壌の全窒素含有率と，アメダスデータや土壌図など容易に入手可能なデータを用いて現地の窒素無機化速度の推定するこの方法は有効であると考えられた。

 

Keizo Hirai, Shinji Kaneko and Masamichi Takahashi：Nitrogen mineralization of forest soil along the climate in Japan−estimation of rate of nitrogen mineralization in the field by soil properties, temperature and soil type−

Field incubation was conducted by resin core method to determine rate and amounts of nitrogen mineralization of top soil under the forest along the climatic zone in Japan. Annual rate of mineralized nitrogen were high in the soils of warm and cool temperate and low in those of to sub arctic and sub tropical. Rate of mineralized nitrogen by laboratory incubation were high in the soils of sub arctic and decreasing to those of warm temperate, and has significant correlation coefficient with organic nitrogen contents in the soil. We estimated nitrogen mineralization potential in the field using rate of mineralized nitrogen of field incubation and ratio of integrated temperature during incubation in the field to laboratory. Nitrogen mineralization potential was higher than rate of nitrogen mineralization measured in the filed in the most of soils and those differences was higher in the soil of lower integrated temperature which located cooler climate. Estimation for rate of nitrogen mineralization in the filed by multiple regression model using organic nitrogen contents, ratio of cumulative temperature and soil type for was done. Estimated values were well correlated with measured values in the field. These results suggest that it was effective to estimate rate of nitrogen mineralization in the field from these factors which were easy to get from AMeDAS(Automated Meteorological Data Acquisition System) and soil map.

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