Skip to main content
Doctoral thesis, 2016

Nitrogen in soil water of coniferous forests

Rappe George, Martin


In boreal and temperate forests, long-term elevated nitrogen (N) load may eventually saturate forest ecosystems with N, i.e. total N ecosystem input exceed ecosystem sinks for N, and N losses via soil water transport may then increase and negatively impact environmental quality. This thesis is based upon four studies (reported in papers I-IV), and the overall aims were to assess and analyse effects on soil water N in coniferous forests of two types of anthropogenic disturbance: “chemical disturbance” (long-term experimental N addition and N deposition), and “physical disturbance” (clear-cutting and subsequent soil scarification). Effects of these disturbances were addressed in both field experiments and process-based ecosystem modelling. In the field experiments, soil water N was collected from both organic (O) horizons and mineral soil, at 0.5 m depth, during several growing seasons to assess temporal variation in the N concentration (Paper I). In addition, microbial variables in soil samples of the O-horizon were analysed in the laboratory to assess responses of the soil microbial community to long-term N addition in forest experiments and along a N deposition gradient (Papers II and IV). In the modelling, a process-based ecosystem carbon and N model (CoupModel) was calibrated to measurements obtained during the regeneration phase of a Scots pine (Pinus sylvestris L.) forest in an N fertilization experiment where soil scarification was applied (Paper III). The results showed that long-term N addition to a boreal Norway spruce (Picea abies (L.) Karst) forest can alter the quantity and seasonal dynamics of dissolved organic nitrogen (DON) concentrations in soil water collected from the O-horizon. However, DON concentrations were low in soil water collected from mineral soil under all N treatments and probably only contributed to small net N losses in this forest. Although microbial variables of the O-horizon were affected by N loading they were similar under N loading that resulted in the leaching of small amounts of nitrate (<2 kg ha⁻¹ year⁻¹ of NO₃-N) and those that resulted in the leaching of large amounts (>15 kg ha⁻¹ year⁻¹ of NO₃-N). Further, soil scarification increased soil water N leaching from a Scots pine forest, as calculated with the CoupModel, during the regeneration phase, particularly in previously N-fertilized pine stands.


nitrogen; forest; water

Published in

Acta Universitatis Agriculturae Sueciae
2016, number: 2016:10
ISBN: 978-91-576-8522-3, eISBN: 978-91-576-8523-0
Publisher: Department of Soil and Environment, Swedish University of Agricultural Sciences

Authors' information

Rappe George, Martin
Swedish University of Agricultural Sciences, Department of Soil and Environment

UKÄ Subject classification

Soil Science

URI (permanent link to this page)