Lukas Hörtnagl
A5061037819- Plant Water Relations and Carbon Dynamics
- Atmospheric and Environmental Gas Dynamics
- Plant responses to elevated CO2
- Peatlands and Wetlands Ecology
- Atmospheric chemistry and aerosols
- Climate variability and models
- Fire effects on ecosystems
- Soil Carbon and Nitrogen Dynamics
- Remote Sensing in Agriculture
- Pasture and Agricultural Systems
- Forest ecology and management
- Hydrology and Watershed Management Studies
- Tree-ring climate responses
- Plant Ecology and Soil Science
- Species Distribution and Climate Change
- Forest Management and Policy
- Cryospheric studies and observations
- Odor and Emission Control Technologies
- Soil and Water Nutrient Dynamics
- Meteorological Phenomena and Simulations
- Horticultural and Viticultural Research
- Climate change and permafrost
- Soil and Unsaturated Flow
- Bioenergy crop production and management
- Rangeland and Wildlife Management
ETH Zurich
2016-2025
Finnish Meteorological Institute
2021
Chinese University of Hong Kong
2021
Northern Arizona University
2021
University of Helsinki
2021
University of Alaska Fairbanks
2021
Universität Innsbruck
2009-2020
Swiss Federal Institute of Aquatic Science and Technology
2018
Instituto de Ciencias Agrarias
2018
Karlsruhe Institute of Technology
2017
We apply and compare three widely applicable methods for estimating ecosystem transpiration (T) from eddy covariance (EC) data across 251 FLUXNET sites globally. All are based on the coupled water carbon relationship, but they differ in assumptions parameterizations. Intercomparison of daily T estimates shows high correlation among (R between .89 .94), a spread magnitudes T/ET (evapotranspiration) 45% to 77%. When compared at six with concurrent EC sap flow measurements, all EC-based show...
Abstract. Methane (CH4) emissions from natural landscapes constitute roughly half of global CH4 contributions to the atmosphere, yet large uncertainties remain in absolute magnitude and seasonality emission quantities drivers. Eddy covariance (EC) measurements flux are ideal for constraining ecosystem-scale due quasi-continuous high-temporal-resolution measurements, coincident carbon dioxide, water, energy lack ecosystem disturbance, increased availability datasets over last decade. Here, we...
Recent studies indicate an increase in the frequency of extreme compound dryness days (days with both soil AND air dryness) across central Europe future, little information on their impact functioning trees and forests. This study aims to quantify assess dryness, For this, >15 years ecosystem-level (carbon dioxide water vapor fluxes) 6-10 tree-level measurements (transpiration growth) each from a montane mixed deciduous forest (CH-Lae) subalpine evergreen coniferous (CH-Dav) Switzerland, is...
Abstract The eddy covariance is a powerful technique to estimate the surface-atmosphere exchange of different scalars at ecosystem scale. EC method central component Integrated Carbon Observation System, monitoring network for greenhouse gases across European Continent. data processing sequence applied collected raw complex, and multiple robust options steps are often available. For System similar networks, standardisation methods essential avoid methodological biases improve comparability...
The recently developed PTR-TOF instrument was evaluated to measure methanol fluxes emitted from grass land using the eddy covariance method. high time resolution of allowed storing full mass spectra up m/z 315 with a frequency 10 Hz. Three isobaric ions were found at nominal 33 due resolving power PTR-TOF. Only one three peaks contributed fluxes. exact this peak agrees well protonated (m/z 33.0335). measured compared virtual disjunct simultaneously conventional PTR-MS. both instruments show...
Abstract. Plant phenological development is orchestrated through subtle changes in photoperiod, temperature, soil moisture and nutrient availability. Presently, the exact timing of plant stages their response to climate management practices are crudely represented land surface models. As visual observations phenology laborious, there a need supplement long-term with automated techniques such as those provided by digital repeat photography at high temporal spatial resolution. We present first...
Eddy covariance (EC) is the preferable technique for flux measurements since it only direct determination method. It requires a continuum of high time resolution (e.g. 5-20 Hz). For volatile organic compounds (VOC) soft ionization via proton transfer reaction has proven to be quantitative method real mass spectrometry; here we use flight spectrometer (PTR-TOF) 10 Hz EC full spectra up m/z 315. The PTR-TOF enabled identification chemical formulas and separation oxygenated hydrocarbon species...
The theoretical basis for the link between leaf exchange of carbonyl sulfide (COS), carbon dioxide (CO(2)) and water vapour (H(2)O) assumptions that need to be made in order use COS as a tracer canopy net photosynthesis, transpiration stomatal conductance, are reviewed. ratios CO(2) H(2)O deposition velocities used this end shown vary with ratio internal ambient mole fractions relative limitations by boundary layer, conductance COS. It is suggested these velocity exhibit considerable...
Abstract Commercially available fast-response analysers for methane (CH 4 ) and nitrous oxide (N 2 O) have recently become more sensitive, robust easier to operate. This has made their application long-term flux measurements with the eddy-covariance method feasible. Unlike carbon dioxide (CO water vapour (H O), there so far been no guidelines on how optimise standardise measurements. paper reviews state-of-the-art of various steps discusses aspects such as instrument selection, setup...
Forests dominate carbon (C) exchanges between the terrestrial biosphere and atmosphere on land. In long term, net flux forests has been significantly impacted by changes in forest cover area structure due to ecological disturbances management activities. Current empirical approaches for estimating ecosystem productivity (NEP) rarely consider age as a predictor, which represents variation physiological processes that can respond differently environmental drivers, regrowth following...
Central European grasslands are characterized by a wide range of different management practices in close geographical proximity. Site-specific strategies strongly affect the biosphere-atmosphere exchange three greenhouse gases (GHG) carbon dioxide (CO2 ), nitrous oxide (N2 O), and methane (CH4 ). The evaluation environmental impacts at site level is challenging, because most situ measurements focus on quantification CO2 exchange, while long-term N2 O CH4 flux ecosystem scale remain scarce....
Abstract Diffuse radiation generally increases photosynthetic rates if total is kept constant. Different hypotheses have been proposed to explain this enhancement of photosynthesis, but conclusive results over a wide range diffuse conditions or about the effect canopy architecture are lacking. Here, we show response photosynthesis different fractions light for five major arable crops (pea, potato, wheat, barley, rapeseed) and cover characterized by architecture. We used 13 years flux...
Using five eddy covariance flux sites (two forests and three grasslands), we investigated ecosystem physiological responses to the 2018 drought across elevational gradients in Switzerland. Flux measurements showed that at lower elevation (below 1000 m.a.s.l.; grassland mixed forest) annual productivity (GPP) declined by approximately 20% compared previous 2 years (2016 2017), which led a reduced net (NEP). At high sites, however, GPP increased 14% as result NEP alpine montane grasslands, but...
Abstract Atmospheric dryness, as indicated by vapor pressure deficit (VPD), has a strong influence on forest greenhouse gas exchange with the atmosphere. In this study, we used long‐term (10–30 years) net ecosystem productivity (NEP) measurements from 60 sites across world (1003 site‐years) to quantify changes in NEP resistance and recovery response extreme atmospheric dryness. We tested two hypotheses: first, differences of forests will depend both biophysical characteristics (i.e., leaf...
Abstract. Mapping in-situ eddy covariance measurements of terrestrial land-atmosphere fluxes to the globe is a key method for diagnosing Earth system from data-driven perspective. We describe first global products (called X-BASE) newly implemented up-scaling framework, FLUXCOM-X. The X-BASE comprise estimates CO2 net ecosystem exchange (NEE), gross primary productivity (GPP) as well evapotranspiration (ET) and, time, novel fully transpiration product (ETT), at high spatial (0.05°) and...
Drought and heat events, such as the 2018 European drought, interact with exchange of energy between land surface atmosphere, potentially affecting albedo, sensible latent fluxes, well CO2 exchange. Each these quantities may aggravate or mitigate heat, their side effects on productivity, water scarcity global warming. We used measurements 56 eddy covariance sites across Europe to examine response fluxes extreme drought prevailing most year how differed various ecosystem types (forests,...
The potential of grasslands to mitigate climate change by carbon (C) sequestration in soils depends on agricultural management and the response grassland C cycle a warming more variable climate. A 15-year time series eddy covariance dioxide (CO2) flux measurements medium-intensively managed at 1000 m above sea level Switzerland was analysed assess how CO2 fluxes respond environmental drivers as well grazing cutting events. Further, effects management, recent trends anomalous weather...
Abstract. Mapping in situ eddy covariance measurements of terrestrial land–atmosphere fluxes to the globe is a key method for diagnosing Earth system from data-driven perspective. We describe first global products (called X-BASE) newly implemented upscaling framework, FLUXCOM-X, representing an advancement previous generation FLUXCOM terms flexibility and technical capabilities. The X-BASE are comprised estimates CO2 net ecosystem exchange (NEE), gross primary productivity (GPP),...