Nitrogen mineralization is the soil process which organic nitrogen converted to inorganic nitrogen. This study aimed 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), and Taiwan red pine forest (Pinus taiwanensis Hay.) in the Tatachia area, central Taiwan. A short term laboratory incubation under 25℃ and 55% water holding capacity (WHC, i.e. 1/3 bars) was used to determine the potential of N mineralization of three forest soils. 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 were analyzed. The relationship between different organic N forms with N mineralization under laboratory incubation was evaluated. Soil-organic N contents was highly correlated with inorganic N (r^2=0.77-0.87; p<0.01) except hydrolysable unknown N showing negative correlation. The incubation results showed that NH4(superscript +)-N production was affected by composition of organic nitrogen. The mineralization rate and NH4(superscript +)-N concentration of spruce and pine forest soils were higher than that of pine forest soils.
Nitrogen mineralization is the soil process which organic nitrogen converted to inorganic nitrogen. This study aimed 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), and Taiwan red pine forest (Pinus taiwanensis Hay.) in the Tatachia area, central Taiwan. A short term laboratory incubation under 25℃ and 55% water holding capacity (WHC, i.e. 1/3 bars) was used to determine the potential of N mineralization of three forest soils. 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 were analyzed. The relationship between different organic N forms with N mineralization under laboratory incubation was evaluated. Soil-organic N contents was highly correlated with inorganic N (r^2=0.77-0.87; p<0.01) except hydrolysable unknown N showing negative correlation. The incubation results showed that NH4(superscript +)-N production was affected by composition of organic nitrogen. The mineralization rate and NH4(superscript +)-N concentration of spruce and pine forest soils were higher than that of pine forest soils.