Direct and indirect pressures of climate change on nutrient and carbon cycling in northern forest ecosystems : Dynamic modelling for policy support
Författare
Summary, in English
This thesis aimed to compare, quantify and analyze the effects of direct and indirect pressures of climate change on forest soil and vegetation processes, and indicators related to nutrient and C cycling in forests, focusing on three of the EQOs that relate to forests, Natural Acidification Only, Zero Eutrophication and Reduced Climate Impact. The dynamic ecosystem model ForSAFE was applied on sites in different climate regions in Sweden, with different exposure to deposition. First, the effect of historical land use change on nitrogen (N) leaching and the risk of eutrophication was studied. Then, effects of intensified forest management on tree growth and concentrations of base cations (BC) and N in the soil solution were investigated. Finally, ForSAFE was used to study the effect of climate change on weathering of BC, which is an important process for providing vegetation with nutrients and for buffering against acidification.
Using a combined approach with empirical data and the ForSAFE model, we could conclude that present environmental conditions alone are not enough to predict the risk of N leaching from two geographically close and comparable forest sites. Information about previous land use and moisture conditions was required to be able to correctly model the current dynamics of the soil organic matter. The effect of N fertilization on tree growth and N leaching was studied at three sites in areas with high, intermediate and low nitrogen deposition. The tree growth was the largest at the low deposition site, whereas the effect on N leaching was more pronounced at the high deposition site. These results support the Swedish Forest Agency´s current recommendations for N fertilization, which differ between regions depending on historical and present N deposition. Whole-tree harvesting (WTH), i.e. harvesting of not only stems but also branches and tops at final felling, led to a temporary reduction (20-30 years) of BC concentrations in the soil solution compared to stem only harvesting, in a study on six sites all over Sweden. This could not be explained by higher weathering rates after WTH, which has been suggested in earlier studies. Instead, it could be explained by higher BC leaching and BC uptake in trees during a period after stem only harvesting. Direct effects of climate change led to an increase in weathering rates in all of Sweden, with increased weathering rates year around in southern Sweden but not in winters in Northern Sweden. Future droughts may reduce weathering due to reduced soil moisture, and the risk is the highest in southern Sweden, where low soil moisture during summers already inhibits weathering. The study also highlighted the importance of soil texture and mineralogy for predicting weathering throughout Sweden, moderating the strong effect of temperature on weathering.
The results highlighted the potential of using process-based models with high temporal resolution on well-investigated sites, for increasing the process knowledge and providing results useful for policy makers. An important message to policy makers is that site history and soil properties should be taken into account when planning for future forest management recommendations to reach the EQOs.
Avdelning/ar
Publiceringsår
2022
Språk
Engelska
Fulltext
Dokumenttyp
Doktorsavhandling
Förlag
Lund University
Ämne
- Environmental Sciences
Nyckelord
- Forest
- boreal ecosystems
- Forest biogeochemistry
- Forest bioenergy
- Boreal coniferous forest
- base cations
- Biogeochemical cycles
- Dynamic Modelling
- Carbon cycle
- nitrogen cycle
- decision support
- policy-making
- Weathering
- Forestry
- Land use change
Status
Published
Projekt
- Dynamic modelling as a basis for policy decisions - Reducing the gap between modelling and policies through stakeholder interactions
Handledare
- Cecilia Akselsson
- Salim Belyazid
- Åsa Knaggård
- Giuliana Zanchi
ISBN/ISSN/Övrigt
- ISBN: 978-91-8039-366-9
- ISBN: 978-91-8039-365-2
Försvarsdatum
30 september 2022
Försvarstid
10:00
Försvarsplats
Pangea, Geocentrum II, Lund. Join via zoom: https://lu-se.zoom.us/j/62731534252?pwd=QytYcnh0TEloL0ZnRVJNRlRkMUJEUT09
Opponent
- Claus Beier (Professor)