tailieunhanh - Báo cáo lâm nghiệp: "Late-season fertilization of Picea mariana seedlings: intensive loading and outplanting response on greenhouse bioassays"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:"Late-season fertilization of Picea mariana seedlings: intensive loading and outplanting response on greenhouse bioassays" | Ann. For. Sci. 61 2004 737-745 737 INRA EDP Sciences 2005 DOI forest 2004073 Original article Late-season fertilization of Picea mariana seedlings intensive loading and outplanting response on greenhouse bioassays Joseph R. Boivin K. Francis Salifu Vic R. Timmer Faculty of Forestry University of Toronto 33 Willcocks Street Toronto M5S 3B3 Canada Received 5 January 2004 accepted 11 May 2004 Abstract - Traditional greenhouse culture involves a late-season hardening period that withholds irrigation and fertilization from black spruce seedlings to promote frost-hardiness. Since nutrient uptake is limited without supplemental fertilization growth during hardening may lead to internal nutrient dilution a condition detrimental to field performance of seedlings. We examine whether late-season fertilization applied as intensive loading will counter dilution and build up nutrient reserves in seedlings reared conventionally or nutrient loaded before hardening. A mixed NPK fertilizer delivering 0 12 24 or 48 mg N-seedling-1 for 9 weeks after bud set was tested. Root and shoot dry mass increased as much as 104 and 42 during hardening. Seedling biomass however was unchanged by late-season fertilization but N uptake was increased 44-167 signifying induced luxury consumption. Extra K supplementation of treatments averted K dilution in plant tissues often occurring with high N addition. A 13-week outplanting trial on intact soil bioassays retrieved from a boreal site showed that growth and nutrient allocation were significantly enhanced by larger N reserves built up after intensive nutrient loading. About 72-80 of N required for new shoot growth was met from internal cycling demonstrating the capacity of loading to enhance retranslocation. Intermediate loading 24 mg N was most effective in promoting N accumulation and outplanting growth of both seedling types. Survival was reduced 30 only at the highest dose. Study results demonstrate the potential advantage of these .