Abstract: The vertical distribution and latitudinal differentiation of alkali-hydrolyzed nitrogen in the profile down to 100 cm depth of maize soils in Northeast China was investigated along a latitudinal gradient. The results showed that soil alkali-hydrolyzed N was mainly distributed at the depth of 0—60 cm, and decreased with soil depth. Except for the Gongzhuling site, the soil alkali-hydrolyzed N content in other sampling sites was significantly different (P<0.05) among the 3 layers at the depth of 0—60 cm. Soil alkali-hydrolyzed N had a significant positive correlation (P<0.01) with soil organic carbon and total N, indicating that its content and distribution was mainly affected by soil organic matter and total N levels. Soil alkali-hydrolyzed N content increased with increasing latitude, and climate condition and soil type were considered as the main reasons that induced the latitudinal differentiation of soil alkali-hydrolyzed N.

Key words: Taxus cuspidata, Chloroplasts, UV-C radiation, Membrane lipid peroxidation, PSⅡelectron transport activity