نتایج جستجو برای: eddy covariance

تعداد نتایج: 44832  

1999

The net ecosystem exchange of CO2 between forests and the atmosphere, measured by eddy covariance, is the small difference between two large fluxes of photosynthesis and respiration. Chamber measurements of soil surface CO2 efflux (Fs), wood respiration (Fw) and foliage respiration (Ff) help identify the contributions of these individual components to net ecosystem exchange. Models developed fr...

2003
H. P. Schmid H.-B. Su C. S. Vogel P. S. Curtis

[1] We report results from the first 3 years (1999–2001) of long-term measurements of net ecosystem exchange (NEE) at an AmeriFlux site over a mixed hardwood forest in northern lower Michigan. The primary measurement methodology uses eddy covariance systems with closed-path infrared gas analyzers at two heights (46 and 34 m) above the forest (canopy height is 22 m). One objective is to contribu...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2015
Jianyang Xia Shuli Niu Philippe Ciais Ivan A Janssens Jiquan Chen Christof Ammann Altaf Arain Peter D Blanken Alessandro Cescatti Damien Bonal Nina Buchmann Peter S Curtis Shiping Chen Jinwei Dong Lawrence B Flanagan Christian Frankenberg Teodoro Georgiadis Christopher M Gough Dafeng Hui Gerard Kiely Jianwei Li Magnus Lund Vincenzo Magliulo Barbara Marcolla Lutz Merbold Leonardo Montagnani Eddy J Moors Jørgen E Olesen Shilong Piao Antonio Raschi Olivier Roupsard Andrew E Suyker Marek Urbaniak Francesco P Vaccari Andrej Varlagin Timo Vesala Matthew Wilkinson Ensheng Weng Georg Wohlfahrt Liming Yan Yiqi Luo

Terrestrial gross primary productivity (GPP) varies greatly over time and space. A better understanding of this variability is necessary for more accurate predictions of the future climate-carbon cycle feedback. Recent studies have suggested that variability in GPP is driven by a broad range of biotic and abiotic factors operating mainly through changes in vegetation phenology and physiological...

2009
Hong-Li Ren Fei-Fei Jin Jong-Seong Kug Jing-Xia Zhao Juhyun Park

[1] A kinematic mechanism for the positive feedback between the North Atlantic Oscillation (NAO) and synoptic eddies are depicted based on observational data analyses. Using three-point rescaled covariance statistics of bandpass-filtered (2–8 days) synoptic eddy fields, we examined observed eddy structure changes associated with wintermean NAO anomalous flow. It is demonstrated that the NAO flo...

2009
S. A. Archibald A. Kirton M. R. van der Merwe R. J. Scholes C. A. Williams

Inter-annual variability in primary production and ecosystem respiration was explored using eddy-covariance data at a semi-arid savanna site in the Kruger Park, South Africa. New methods of extrapolating night-time respiration to the entire day and filling gaps in eddy-covariance data in semi-arid systems were developed. Net ecosystem exchange (NEE) in these systems occurs as pulses associated ...

2015
J. Minet E. Laloy B. Tychon

Eddy covariance data from four European grassland sites are used to probabilistically invert the CARAIB (CARbon Assimilation In the Biosphere) dynamic vegetation model (DVM) with 10 unknown parameters, using the DREAM(ZS) (DiffeRential Evolution Adaptive Metropolis) Markov chain Monte Carlo (MCMC) sampler. We focus on comparing model inversions, considering both homoscedastic and heteroscedasti...

2012
Benjamin N. Sulman Ankur R. Desai Nicole M. Schroeder Dan Ricciuto Alan Barr Andrew D. Richardson Lawrence B. Flanagan Peter M. Lafleur Hanqin Tian Guangsheng Chen Robert F. Grant Benjamin Poulter Hans Verbeeck Philippe Ciais Bruno Ringeval Ian T. Baker Kevin Schaefer Yiqi Luo Ensheng Weng

[1] Northern peatlands are likely to be important in future carbon cycle-climate feedbacks due to their large carbon pools and vulnerability to hydrological change. Use of non-peatland-specific models could lead to bias in modeling studies of peatland-rich regions. Here, seven ecosystem models were used to simulate CO2 fluxes at three wetland sites in Canada and the northern United States, incl...

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