Abstract: Taking 26-year-old Caragana microphylla, Hedysarum fruticosum, Salix gordeivii, Artemisia halodendron, and Pinus sylvestris var. mongolica plantations and different aged C. microphylla plantations in Horqin Sandy Land as test objects, this paper measured the soil nutrient contents, enzyme activities, and nitrification activity. Among the five 26-year-old plantations, C. microphylia plantation had obviously higher soil organic matter, total N, NH₄⁺-N, and NO₃^--N contents and the highest soil urease, protease, and nitrification activities, and S. gordeivii plantation had the highest soil nitrate reductase activity. The soil urease and protease activities were significantly positively correlated with soil organic matter content. With the increasing age of C. microphylla plantation, the contents of soil organic matter, total N, NH₄⁺-N, and NO₃^--N, the activities of test soil enzymes, and the soil nitrification activity increased, and the soil urease and protease activities had significant positive correlations with the plantation age.

Key words: Reflectivity, Broad-leaved Korean pine forest, Diurnal variation, Seasonal variation