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Conference paper2005

Modeling long-term effects of N fertilization and N deposition on the N balances of forest stands in Sweden

Gärdenäs, Annemieke; Eckersten, Henrik; Lillemägi, M

Abstract

The long-term effects of N fertilization and N deposition on the nitrogen balances of forest stands in Sweden were studied with a coupled nitrogen and carbon model SOILN (Eckersten et al., 1998). Three main forested vegetation zone in Sweden, pine in northern and central Sweden, and spruce in southern Sweden, were represented with their different climate, soil type, stem production and N deposition level. The simulations were done for a whole forest rotation period (75-100 years). The N deposition levels tested were 50 %, 100 % and 150 % of 1996’s levels for each region. The total fertilization dose for central and northern Sweden were 300 and 600 kg N ha-1 respectively and no fertilization for southern Sweden in accordance with the fertilization recommendations by the National Board of Forestry Sweden. The uptake of organic N by symbiosis with mycorrhiza showed to be essential to simulate biomass production and N content in the same levels as found in the literature. The nitrogen balances over a whole rotation period were negative for several scenarios without fertilization. With fertilization, most nitrogen balances were positive. N harvested was of the same magnitude as total amount N added by deposition and fertilization, while N leached was only 1-7 % of total N added. N leaching increased in many cases with increase of total N fertilization dose. However, the second fertilization dose of 150 kg N ha-1added little to total N leached because of the positive effect of fertilizer-induced biomass growth on plant N demand and C/N-ratio of litter layer. Increased N deposition lead to no increase of percentage N leached of total N added by deposition. Increasing deposition level enhanced plant growth and N demand in such a degree that also uptake of organic N by symbiosis with mycorrhiza was stimulated. We conclude that the combined effect of N fertilization and deposition level is complex. The risks of N leaching seemed to be very sensitive for the simulated needle biomass and C/N-ratio of litter and humus. Weather conditions determine whether these risks became a reality or not. Fig

Keywords

SOILN-model; Nitrogen; deposition; fertilization; forest ecosystems; Sweden

Published in

Title: Abstract proceedings ACID RAIN 2005, 7th international conference on acid deposition, Session 20, Nitrogen effects on ecosystems

Conference

ACID RAIN 2005, 7th international conference on acid deposition