Alexander Knohl
A5051172985- Plant Water Relations and Carbon Dynamics
- Atmospheric and Environmental Gas Dynamics
- Oil Palm Production and Sustainability
- Climate variability and models
- Forest ecology and management
- Plant responses to elevated CO2
- Remote Sensing in Agriculture
- Tree-ring climate responses
- Conservation, Biodiversity, and Resource Management
- Fire effects on ecosystems
- Atmospheric chemistry and aerosols
- Remote Sensing and LiDAR Applications
- Ecology and Vegetation Dynamics Studies
- Forest Management and Policy
- Isotope Analysis in Ecology
- Soil Carbon and Nitrogen Dynamics
- Peatlands and Wetlands Ecology
- Hydrology and Watershed Management Studies
- Geology and Paleoclimatology Research
- Hydrology and Drought Analysis
- Spectroscopy and Laser Applications
- Land Use and Ecosystem Services
- Aeolian processes and effects
- Forest Ecology and Conservation
- Biofuel production and bioconversion
University of Göttingen
2016-2025
Forest Research
2019
ETH Zurich
2007-2014
University of California, Berkeley
2005-2014
Oregon State University
2014
Corvallis Environmental Center
2014
John Wiley & Sons (United States)
2014
Biogéosciences
2014
Board of the Swiss Federal Institutes of Technology
2008-2011
Plant (United States)
2009
Abstract This paper discusses the advantages and disadvantages of different methods that separate net ecosystem exchange (NEE) into its major components, gross carbon uptake (GEP) respiration ( R eco ). In particular, we analyse effect extrapolation night‐time values daytime; this is usually done with a temperature response function derived from long‐term data sets. For analysis, used 16 one‐year‐long sets dioxide measurements European US‐American eddy covariance networks. These sites span...
Abstract Land-use transitions can enhance the livelihoods of smallholder farmers but potential economic-ecological trade-offs remain poorly understood. Here, we present an interdisciplinary study environmental, social and economic consequences land-use in a tropical landscape on Sumatra, Indonesia. We find widespread biodiversity-profit resulting from forest agroforestry systems to rubber oil palm monocultures, for 26,894 aboveground belowground species whole-ecosystem multidiversity....
Abstract The European CARBOEUROPE/FLUXNET monitoring sites, spatial remote sensing observations via the EOS‐MODIS sensor and ecosystem modelling provide independent complementary views on effect of 2003 heatwave biosphere's productivity carbon balance. In our analysis, these data streams consistently demonstrate a strong negative anomaly primary during summer 2003. FLUXNET eddy‐covariance indicate that drop in was not primarily caused by high temperatures (‘heat stress’) but rather...
Half‐hourly measurements of the net exchanges carbon dioxide and water vapor between terrestrial ecosystems atmosphere provide estimates gross primary production (GPP) evapotranspiration (ET) at ecosystem level on daily to annual timescales. The ratio these quantities represents use efficiency. Its multiplication with mean daylight pressure deficit (VPD) leads a quantity which we call “inherent efficiency” (IWUE*). dependence IWUE* environmental conditions indicates possible adaptive...
linear relations with measurements of solar irradiance (r 2 = 0.95, relative bias: 8%), gross primary productivity 0.86, 5%) and evapotranspiration 15%) in data from 33 flux towers that cover seven plant functional types across arctic to tropical climatic zones. A sensitivity analysis revealed the computed BESS were most sensitive leaf area index irradiance, respectively. We quantified mean global terrestrial estimates evapotranpiration between 2001 2003 as 118 � 26 PgC yr 1 500 104 mm...
Non-photosynthetic, or heterotrophic, tissues in C3 plants tend to be enriched 13C compared with the leaves that supply them photosynthate. This isotopic pattern has been observed for woody stems, roots, seeds and fruits, emerging leaves, parasitic incapable of net CO2 fixation. Unlike plants, roots herbaceous C4 are generally not 13C-enriched leaves. We review six hypotheses aimed at explaining this plants: (1) variation biochemical composition heterotrophic leaves; (2) seasonal separation...
Summary Based on review and original data, this synthesis investigates carbon pools fluxes of Siberian European forests (600 300 million ha, respectively). We examine the productivity ecosystems, expressed as positive rate when amount in ecosystem increases, while (following micrometeorological convention) downward from atmosphere to vegetation (NEE = Net Ecosystem Exchange) are negative numbers. Productivity parameters Primary (NPP=whole plant growth), (NEP CO 2 assimilation minus...
Tropical lowland rainforests are increasingly threatened by the expansion of agriculture and extraction natural resources. In Jambi Province, Indonesia, interdisciplinary EFForTS project focuses on ecological socio-economic dimensions rainforest conversion to jungle rubber agroforests monoculture plantations oil palm. Our data confirm that transformation land use intensification lead substantial losses in biodiversity related ecosystem functions, such as decreased above- below-ground carbon...
Forest ecosystems across the globe show an increase in ecosystem carbon uptake efficiency under conditions with high fraction of diffuse radiation. Here, we combine eddy covariance flux measurements at a deciduous temperate forest central Germany canopy‐scale modeling using biophysical multilayer model CANVEG to investigate impact radiation on various canopy gas exchange processes and elucidate underlying mechanisms. Increasing enhances photosynthesis by redistributing solar load from light...
Abstract Smallholder-dominated agricultural mosaic landscapes are highlighted as model production systems that deliver both economic and ecological goods in tropical landscapes, but trade-offs underlying current land-use dynamics poorly known. Here, using the most comprehensive quantification of change associated bundles ecosystem functions, services benefits to date, we show Indonesian smallholders predominantly choose farm portfolios with high productivity low value. The more profitable...
Abstract. Extreme climatic events, such as droughts and heat stress, induce anomalies in ecosystem–atmosphere CO2 fluxes, gross primary production (GPP) ecosystem respiration (Reco), and, hence, can change the net carbon balance. However, despite our increasing understanding of underlying mechanisms, magnitudes impacts different types extremes on GPP Reco within between ecosystems remain poorly predicted. Here we aim to identify major factors controlling amplitude extreme-event GPP, Reco,...
Abstract The leaf economics spectrum 1,2 and the global of plant forms functions 3 revealed fundamental axes variation in traits, which represent different ecological strategies that are shaped by evolutionary development species 2 . Ecosystem depend on environmental conditions traits comprise communities 4 However, ecosystem largely unknown, limits our understanding how ecosystems respond as a whole to anthropogenic drivers, climate variability 4,5 Here we derive set 6 from dataset surface...
Land-use intensification in the tropics plays an important role meeting global demand for agricultural commodities but generates high environmental costs. Here, we synthesize impacts of rainforest conversion to tree plantations increasing management intensity on carbon stocks and dynamics. Rainforests Sumatra converted jungle rubber, oil palm monocultures lost 116 Mg C ha-1, 159 174 respectively. Up 21% these losses originated from belowground pools, where soil organic matter still decreases...
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...
Pioneering work in the last century has resulted a widely accepted paradigm that primary production is strongly positively related to temperature and water availability such northern hemispheric forest carbon sink may increase under conditions of global warming. However, terrestrial at ecosystem level (i.e. net productivity, NEP) depends on balance between gross productivity (GPP) respiration (TER). Through an analysis European eddy covariance flux data sets, we find common climate...
Abstract. We applied a site evaluation approach combining Lagrangian Stochastic footprint modeling with quality assessment for eddy-covariance data to 25 forested sites of the CarboEurope-IP network. The analysis addresses spatial representativeness flux measurements, instrumental effects on quality, patterns in and performance coordinate rotation method. Our findings demonstrate that application filter could strengthen database, since only one third is situated truly homogeneous terrain....