vegetation responses; climate change; eddy covariance; ecophysiology; carbon balance; tree water relations; wood growth; net ecosystem productivity; gross primary production; ecosystem respiration; forest carbon dynamics; net ecosystem CO2 bdget; dendrometer; forest response; decidous forest; coniferous forest
Haeni M Zweifel R Eugster W Gessler A Zielis S Carrara A Knohl A Havránková K Herbst M Ibro (2017), Winter respiratory C losses provide explanatory power for net ecosystem productivity, in Journal of Geophysical Research – Biogeosciences
, 122, 243-226.
Zweifel R Haeni M Buchmann N Eugster W (2016), Are trees able to grow in periods with shrunken stems?, in New Phytologist
, 211, 839-849.
Zielis S Etzold S Zweifel R Eugster W Haeni M Buchmann N (2014), NEP of a Swiss subalpine forest is significantly driven not only by current but also by previous year’s weather, in Biogeosciences
, 11, 1627-1635.
Reichstein M Bahn M Ciais P Frank D Mahecha MD Seneviratne SI Zscheischler J Beer C Buchmann (2013), Climate extremes and the carbon cycle, in Nature
, 500, 287-295.
Wolf S Eugster W Ammann C Häni M Zielis S Hiller R Stieger J Imer D Merbold L Buchmann N (2013), Contrasting response of grassland versus forest carbon and water fluxes to spring drought in Switzerland, in Environmental Research Letters
, 8, 035007.
Zielis S Etzold S Zweifel R Eugster W Haeni M Buchmann N (2013), Forest NEP is significantly driven by previous year’s weather, in Biogeosciences Discussion
, 10, 15587-15611.
Etzold S Zweifel R Rühr N Eugster W Buchmann N (2013), Long-term stem CO2 concentration measurements in Norway spruce in relation to biotic and abiotic factors, in New Phytologist
, 197, 1171-1184.
Haeni M Zweifel R Eugster W Gessler A Zielis S Carrara A Knohl A Havránková K Herbst M Ibro, Compensation of net carbon loss after wintertime explains annual net ecosystem productivity of European forests, in Journal of Geophysical Research – Biogeosciences
Churakova OV (Sidorova) Eugster W Etzold S Cherubini P Zielis S Saurer M Siegwolf R Buchmann, Increasing relevance of spring temperatures for Norway spruce trees in Davos, Switzerland, after the 1950s, in Trees
, 28, 183-191.
RelevanceThe project Forest Ecosystem Responses to Climatic Drivers aims at understanding time lags between climatic drivers and the respective ecosystem responses in terms of net ecosystem productivity (NEP) at the two Swiss Fluxnet sites Davos and Lägeren. The project has a highly interdisciplinary character and brings together detailed knowledge from plant physiology, forest ecology and meteorology to disentangle the effects on NEP of (i) actual physical drivers, and (ii) biotic conditions determined by past and recent climatic conditions. Understanding the natural processes determining the carbon balance of forest ecosystems is of great global interest for estimating country-specific carbon budgets within the United Nations Framework Convention on Climate Change (UNFCCC). The topic is a current hotspot at which precise questions from politics meet the incomplete knowledge of various environmental science disciplines. Working HypothesesWe hypothesize that the current year NEP is significantly driven by climatic drivers of the recent past (month to years) and not only by present conditions as typically assumed. Furthermore we hypothesize that observed time lags between climatic drivers and NEP are due to storage dynamics of carbon and water in trees.Specific AimsOur specific aims are to (i) identify climatic drivers of NEP at two contrasting forest sites, (ii) to quantify the impact of the climatic drivers on observed time lags of ecosystem responses, and (iii) to assess the underlying physiological mechanisms explaining such time lags and therefore flux partitioning. Experimental Design and Analysing ConceptIn order to address these aims, we plan:- to measure microclimate profiles, eddy covariance net ecosystem CO2 and H2Ovapor exchange, continuous stem radius changes, and [CO2] in tree stems at two Swiss Fluxnet sites Davos and Lägeren. - to analyse statistical patterns of historic time series which quantify the time-dependent weight of climatic drivers on ecosystem responses.- to compare the results of two forest types from the Swiss Fluxnet sites Davos and Lägeren.- to test the applicability of physiological concepts to explain the observed time lags and thus flux partitioning of CO2 and H2Ovapor fluxes at the ecosystem level.Our long-term forest ecosystem research sites (Davos since 1997; Lägeren since 2005) are predestined locations to address topics that depend on temporally and spatially highly resolved field data at different integration levels with long-term records. Expected Value of the Project ProposedOur project will contribute to fill the gaps in our knowledge of how tree physiological processes (particularly growth and tree water relations) are linked to ecosystem-level gas exchange (investigated by eddy covariance) and their respective dependencies on climatic drivers. Such mechanistic understanding is urgently needed to advance climate impact science and to decrease uncertainties in current vegetation-climate models. Since understanding the role of ecosystems in global climate change is currently a hot topic in science and for society concerned about climate change, we expect to provide relevant information to national administrations and to satisfy their demand for more precise, country-wide forest ecosystem carbon budgets.