Abstract: Nitrogen and phosphorus (NP) deposition can change the nutrient input of forest ecosystems. The effects of NP deposition on soil aggregate need to be analyzed to propose effective environmental management strategies. In this study, representative Korean pine mixed forests and Korean pine plantations in northeastern China were selected. Soil samples were sieved to obtain four different particle sizes of soil aggregates (> 2, 2–0.25, 0.25–0.053, and  < 0.053 mm). Four NP treatments were applied to simulate N and P deposition, and an indoor incubation experiment was conducted over a period of 360 d. Total nitrogen, microbial nitrogen, dissolved organic nitrogen, hydrolyzed nitrogen, NH₄⁺–N, NO₃⁻–N content, and extracellular enzyme activities of NAG, LAP, and AP were determined. Different fractions of N responded differently to NP addition. Lower NP addition had a greater promoting effect on aggregate N compared to higher NP addition. NAG was the main extracellular enzyme affecting N in both forest types. NP addition had a greater effect on the extracellular enzyme activities of the soil aggregates from the Korean pine plantations. These results enhance our understanding of the effects of NP addition on soil nitrogen within temperate forest ecosystems.

Key words: Korean pine, Nitrogen-phosphorus addition, Soil aggregate, Nitrogen fractions, Extracellular enzymes