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The SwissForestLab Inauguration Symposium will take place on 05.09.2017 at the Eidgenössische Forschungsanstalt WSL in Birmensdorf.

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Member and Partner Institutions

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Research Projects

Here we present SwissForestLab research projects of our members. To get more detailed information please contact us or directly the corresponding PIs.

THE EFFECTS OF DROUGHT ON THE INTERACTION BETWEEN CARBON AND NITROGEN RELATIONS IN TREES

 

Corresponding authors: Arthur Gessler and Jobin Joseph

Summary

The Global Climate Change is projected to increase the frequency and intensity of weather extremes in Central Europe. As one consequence extreme drought events will occur more often with potential negative effects on the growth and performance of trees and forest ecosystems.

Mainly two complementing mechanisms leading to growth impairment, reduction of physiological performance and mortality upon drought are discussed at present, namely hydraulic failure (as a result of xylem embolisms) and carbon starvation (due to insufficient photosynthetic carbon assimilation). In addition, the negative impacts of drought on nutrient uptake may lead to disturbed nutrient balance of trees and ecosystems. Hence, nutrient uptake is an additional important parameter affecting tree performance under drought and there is only little information available on the underlying mechanisms.

The research proposed here will thus shed light on the effects of drought and recovery from drought on the nitrogen uptake of trees. Nitrogen is the major growth limiting nutrient in natural temperate terrestrial ecosystems and has thus been chosen as model nutrient. The proposed project consists of three modules: in module 1 we will screen the importance of physiological restrictions of nitrogen uptake capacity (Jmax (maximum ammonium and nitrate net uptake capacity) and C50 (nitrate or ammonium concentration where 50% of the maximum net uptake is observed)) under drought for seven different tree species. Module 1 will also assess the plasticity of tree species to compensate for a decreased soil nitrogen availability with biomass allocation to the mycorrhizal fine roots. Module 2 will build upon this screening and consist of an in-depth analysis of the mechanisms that control the nitrogen uptake capacity under restricted water supply, with a particular focus on the interplay between transport of recent assimilates belowground and nitrogen uptake. In module 3, we will extend the mechanistic analysis of module 2 to the phase of recovery from drought and will focus on the re-establishment of transport of recent assimilates and nitrogen uptake capacity.

By linking nutrient uptake with the carbon and water balance this work will complement and extend the existing conceptual models on drought effects on tree physiology.

 

PRO3FILE

Predicting Ozone Fluxes, Impacts, and Critical Levels on European Forests

 

Corresponding author: Marcus Schaub

Summary

Tropospheric ozone (O3) is considered to be more damaging to vegetation than any other air pollutant. Public concerns, evidence from research, and increasing scientific knowledge are all driving widespread discussions on ozone risk assessment and dose-response relationships for European forests. In particular, there is high uncertainty concerning the effect of ozone on individual tree diameter increment and forest growth. However, the contrasting results may arise from the different data used as input in terms of sample size and characteristics, and/or from differing methodological choices. This study therefore aims to make use of over 200 long-term monitoring plots across Europe where ozone concentrations have been measured since 2000, in parallel to forest and vegetation variables. Ozone related effects and critical levels on selected endpoints such as tree growth will be derived by quantifying ozone fluxes, and by (i) applying multiple and various statistical techniques that also consider for other abiotic and biotic environmental factors. The outputs will be validated and up-scaled in space and time by (ii) developing an “Ozone-version” of the physiological process-based model CASTANEA, and (iii) coupling the DO3SE model with the forest succession (“gap”) model ForClim. Data sources from various networks will be explored and applied for model calibrations, validations, and applications. The outlined ensemble of statistical and mechanistic model simulations will allow us to detect environmental tipping points leading to strong decrease in stand productivity. This allows for the determination of species-specific, site-specific, and climate change-specific critical ozone levels, which will be an important contribution to the objectives of the UNECE WG on Effects.

 

QUPFiS

Quantifying, understanding and predicting forest growth in Switzerland

 


Corresponding author: Werner Eugster

Summary

Forests world-wide are known as an important net carbon sink and are thus a key component of the terrestrial carbon cycle. However, carbon fluxes and storage vary regionally and with inter-annual to long-term environmental change. A higher frequency of drought events and other negative impacts on growth (increased autotrophic respiration and disturbances) are predicted to outweigh enhanced productivity as a result of increasing temperatures or CO2 and nitrogen fertilization. Existing models of forest growth dynamics include large uncertainties, which ramify and lead to divergence in forecasts how climate change will impact the future terrestrial carbon cycle. To reduce these uncertainties, it is necessary to extend and combine assessments of current observation networks using novel analytical approaches and data sources. Swiss forests are of particular interest: the climatic, pedologic and biogeographical conditions of Switzerland correspond closely with the European gradient, on a relatively small geographical scale.

WSL and its partners own a wealth of diverse data on forest growth and health in Switzerland. We plan to exploit this data treasure in our SwissForestLab project. Our aim is to estimate Swiss forest net ecosystem productivity (NEP) at monthly or seasonal resolution in order to link biomass changes over time with global drivers (climate, soils, landscapes, N deposition). We hypothesize that a combination of available high-quality long-term data sets provides an excellent data basis for a data-model-fusion approach within SwissForestLab. This activity is expected (a) to merge data with different temporal and spatial resolution so that they can be used more easily by SwissForestLab members, and (b) to provide a first visible result from SwissForestLab that will foster follow-up research projects focusing on different aspects of forest growth and development.