Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Dry matter and nitrogen allocation in western redcedar, western hemlock, and Douglas fir seedlings grown in low- and high-N soils 1. | 529 Ann. For. Sci. 56 1999 529-538 Inra Elsevier Paris Original article Dry matter and nitrogen allocation in western redcedar western hemlock and Douglas fir seedlings grown in low- and high-N soils1 Joseph E. Graff Jr Richard K. Hermann Joe B. Zaerr Department of Forest Science Oregon State University Corvallis OR 97331 USA Received 28 October 1998 accepted 7 June 1999 Abstract - Seedlings of western red cedar Thuja plicata Donn ex. D. Don western hemlock Tsuga heterophylla Raf. Sarg. and Douglas fir Pseudolsuga menziesii Mirb. Franco were transplanted into each of 48 pots with soils of low or high levels of available NO3 and total N and assigned to one of four treatments unamended control amendment with 60 mg kg 1 NH4 SO4 amendment with 15 mg kg-1 of the nitrification inhibitor dicyandiamide DCD or amendment with both NH4 2SO4 and DCD. Dry weight and N content increments of seedling tissues were determined after 8 weeks. Seedlings grown on the low-N soil accumulated 65 of the dry matter and 40 of the N accumulated by seedlings grown on the high-N soil. Retranslocation of N from year-old foliage and the stem branch components of western red cedar and Douglas fir but not western hemlock was an important source of N for cur-rent-year foliage and roots of low-N-grown seedlings. Western hemlock achieved the greatest relative dry-matter increment Loge DMfina - Loge DMinitịa RDMI and relative N increment Logc N inal - Loge Njnjlial RNI in each soil and accumulated 35 more N from the low-N and 10 more N from the high-N soils than the other species. The RDMI of western red cedar was intermediate between that of western hemlock and Douglas fir whereas its RNI on each of the soils was lowest. The results suggest that western hemlock is more efficient than western red cedar or Douglas fir in acquiring inorganic N especially from low-N soils. 1999 Editions scientifiques et medicales Elsevier SAS. foliage mass root nitrogen content relative dry matter increment .
