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Research article2004Peer reviewed

Interactive effects of soil warming and fertilization on root production, mortality, and longevity in a Norway spruce stand in Northern Sweden

Majdi H, Ohrvik J


The effects of soil warming and nitrogen availability on root production, longevity and mortality were studied using minirhizotrons in irrigation (C), fertilized (F), heated (H), and heated-fertilized (HF) plots in a Norway spruce stand in northern Sweden from October 1996 to October 1997. Irrigation was included in all treatment plots. Heating cables were used to maintain the soil temperature in heated plots at 5degreesC above that in unheated plots during the growing season. A Kaplan-Meier approach was used to estimate the longevity of fine roots and Cox proportional hazards regression to analyze the effects of the H, F, and HF treatments on the risk of root mortality. The proportion of annual root length production contributed by winter-spring production amounted to 52% and 49% in heated plots and heated-fertilized plots, respectively. The annual root length production in C plots was significantly higher than in other treatments, while the HF treatment gave significantly greater production compared with the F treatment. The risk of mortality (hazard ratio) relative to C plots was higher in H plots (358%) and F plots (191%). The interaction between heating and fertilizing was strongly significant. The increase in the risk of root mortality in combined fertilization and heating (103%) was lower than that in the H or F plots. The results show that nitrogen addition combined with warmer temperatures decreases the risk of root mortality, and fine root production is a function of the length of the growing season. In the future, fertilization combined with the warmer temperatures expected to follow predicted climatic change may increase root production in boreal forests at low fertility sites

Published in

Global Change Biology
2004, Volume: 10, number: 2, pages: 182-188

      SLU Authors

    • Majdi, Hooshang

      • Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Environmental Sciences related to Agriculture and Land-use
    Forest Science

    Publication identifier


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