Frost sensitivity and nutrient status in a fertilized Norway spruce stand in Denmark Anna Maria Jo ¨nsson * , Morten Ingerslev, Karsten Raulund-Rasmussen Forest and Landscape Denmark, Hørsholm Kongevej 11, DK-2970 Hørsholm, Denmark Received 5 June 2003; received in revised form 22 April 2004; accepted 8 June 2004 Abstract The aim of this study was to assess the effect of the N, P and K status on frost sensitivity of Norway spruce needles in a fertilization experiment situated in a nutrient poor 29-year-old Picea abies stand in western Denmark. The relative difference in frost sensitivity among trees was assessed by an index of injury, based on conductivity measurements of ion leakage from needles. Despite fertilization, all trees indicated N, P and K deficiency. The foliage, collected in late winter, was generally not very frost sensitive, but foliage from trees with the lowest K and P status were more sensitive to frost, and the current year needles were more sensitive than the second and third year needles. The advancement of bud burst was assessed in May. Trees with a relatively high N concentration in the current year needles had a more advanced bud burst than trees with a lower N concentration, increasing the risk for frost damage by a temperature backlash. # 2004 Elsevier B.V. All rights reserved. Keywords: Frost hardiness; Index of injury; Nitrogen; Phosphorus; Picea abies; Potassium 1. Introduction Nitrogen is the nutrient that most commonly limits the growth of forest trees, and the trees are sensitive to nutrient imbalance induced by a high nitrogen deposi- tion (Nihlga ˚rd, 1985). On the nutrient poor sandy soils in mid and western Denmark, K and P are the two elements that most probably will, and at some forest sites already have become deficient relative to N (Dralle and Larsen, 1995). Fertilization with a balanced composition of mineral nutrients, except N, is a way to counteract nutrient deficiencies or imbalances in the trees (Hu ¨ttl, 1989; Nilsson and Wiklund, 1995). Spruces retranslocate easily move- able nutrients, such as N, P and K, from older to younger needles, and deficiencies of these elements are thus often more pronounced in older needles (e.g. Weikert et al., 1989; Marschner, 1995). The frost hardiness can be affected by the nutrient status through changes in the timing of hardening and dehardening, or by changes in the ability to harden (Bigras et al., 2001). A high concentration of N in the www.elsevier.com/locate/foreco Forest Ecology and Management 201 (2004) 199–209 * Corresponding author. Present address: Department of Eco- logy, Plant Ecology and Systematics, Lund University, Ecology Building, 223 62 Lund, Sweden. Tel.: +46 46 222 4247; fax: +46 46 222 4423. E-mail address: anna_maria.jonsson@ekol.lu.se (A.M. Jo ¨nsson). 0378-1127/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2004.06.030