Growth response of young, thinned Douglas-fir stands to nitrogen fertilizer in relation to soil properties and tree nutrition

• Published in: Canadian journal of forest research Vol. 24; no. 8
• Main Authors: Hopmans, P. (Department of Conservation and Natural Resources, Kew, Australia.), Chappell, H.N
• Format: Journal Article
• Language: English
• Published: 01.08.1994
• Subjects: ABONOS NITROGENADOS; ACLAREO; AZOTE; CIENCIA DEL SUELO; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; ECLAIRCISSAGE; ENGRAIS AZOTE; FEUILLE; HOJARASCA FORESTAL; HOJAS; INDICE DE CRECIMIENTO; LITIERE FORESTIERE; NITROGENO; OREGON; PSEUDOTSUGA MENZIESII; SCIENCES DU SOL; TAUX DE CROISSANCE; VALEUR NUTRITIVE; VALOR NUTRITIVO; VOLUME; VOLUMEN; WASHINGTON
• ISSN: 0045-5067; 1208-6037
• DOI: 10.1139/x94-217

Application of 224 kg N/ha to young, thinned stands of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) at 35 sites in western Oregon and Washington significantly increased basal area and volume increment over 8 years following treatment. However, response varied considerably between sites, and relative volume increment exceeded 10% at only 19 of the 35 sites. Response to applied N was evaluated in relation to forest floor and soil variables as well as to levels of N in foliage. Relative responses in basal area and volume were significantly correlated with total N concentration and the C/N ratio of the soil. However, these relationships explained only part (18-22%) of the observed variation in response. In contrast, relative response was strongly correlated with the level of N in the foliage of nonfertilized trees at 11 sites, accounting for 94% of the variation between sites. Use of foliar N data clearly has potential to predict growth responses to N fertilization of young thinned Douglas-fir stands, although further work is needed to test the relationship for a wider range of sites and stands