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Title: Quantifying and reducing the differences in forest CO 2-fluxes estimated by eddy covariance, biometric and chamber methods: A global synthesis

Abstract

Carbon dioxide (CO 2) fluxes between terrestrial ecosystems and the atmosphere are primarily measured with eddy covariance (EC), biometric, and chamber methods. However, it is unclear why the estimates of CO 2-fluxes, when measured using these different methods, converge at some sites but diverge at others. We synthesized a novel global dataset of forest CO 2-fluxes to evaluate the consistency between EC and biometric or chamber methods for quantifying CO 2 budget in forests. The EC approach, comparing with the other two methods, tended to produce 25% higher estimate of net ecosystem production (NEP, 0.52Mg C ha-1 yr-1), mainly resulting from lower EC-estimated Re; 10% lower ecosystem respiration (Re, 1.39Mg C ha-1 yr-1); and 3% lower gross primary production (0.48 Mg C ha-1 yr-1) The discrepancies between EC and the other methods were higher at sites with complex topography and dense canopies versus those with flat topography and open canopies. Forest age also influenced the discrepancy through the change of leaf area index. The open-path EC system induced >50% of the discrepancy in NEP, presumably due to its surface heating effect. These results provided strong evidence that EC produces biased estimates of NEP and Re in forest ecosystems. A globalmore » extrapolation suggested that the discrepancies in CO 2 fluxes between methods were consistent with a global underestimation of Re, and overestimation of NEP, by the EC method. Accounting for these discrepancies would substantially improve the our estimates of the terrestrial carbon budget .« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1416691
Report Number(s):
PNNL-SA-124998
Journal ID: ISSN 0168-1923; KP1702010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Agricultural and Forest Meteorology; Journal Volume: 247; Journal Issue: 15 December 2017; Related Information: pages 93-103
Country of Publication:
United States
Language:
English

Citation Formats

Wang, Xingchang, Wang, Chuankuan, and Bond-Lamberty, Benjamin. Quantifying and reducing the differences in forest CO2-fluxes estimated by eddy covariance, biometric and chamber methods: A global synthesis. United States: N. p., 2017. Web. doi:10.1016/j.agrformet.2017.07.023.
Wang, Xingchang, Wang, Chuankuan, & Bond-Lamberty, Benjamin. Quantifying and reducing the differences in forest CO2-fluxes estimated by eddy covariance, biometric and chamber methods: A global synthesis. United States. doi:10.1016/j.agrformet.2017.07.023.
Wang, Xingchang, Wang, Chuankuan, and Bond-Lamberty, Benjamin. Fri . "Quantifying and reducing the differences in forest CO2-fluxes estimated by eddy covariance, biometric and chamber methods: A global synthesis". United States. doi:10.1016/j.agrformet.2017.07.023.
@article{osti_1416691,
title = {Quantifying and reducing the differences in forest CO2-fluxes estimated by eddy covariance, biometric and chamber methods: A global synthesis},
author = {Wang, Xingchang and Wang, Chuankuan and Bond-Lamberty, Benjamin},
abstractNote = {Carbon dioxide (CO2) fluxes between terrestrial ecosystems and the atmosphere are primarily measured with eddy covariance (EC), biometric, and chamber methods. However, it is unclear why the estimates of CO2-fluxes, when measured using these different methods, converge at some sites but diverge at others. We synthesized a novel global dataset of forest CO2-fluxes to evaluate the consistency between EC and biometric or chamber methods for quantifying CO2 budget in forests. The EC approach, comparing with the other two methods, tended to produce 25% higher estimate of net ecosystem production (NEP, 0.52Mg C ha-1 yr-1), mainly resulting from lower EC-estimated Re; 10% lower ecosystem respiration (Re, 1.39Mg C ha-1 yr-1); and 3% lower gross primary production (0.48 Mg C ha-1 yr-1) The discrepancies between EC and the other methods were higher at sites with complex topography and dense canopies versus those with flat topography and open canopies. Forest age also influenced the discrepancy through the change of leaf area index. The open-path EC system induced >50% of the discrepancy in NEP, presumably due to its surface heating effect. These results provided strong evidence that EC produces biased estimates of NEP and Re in forest ecosystems. A global extrapolation suggested that the discrepancies in CO2 fluxes between methods were consistent with a global underestimation of Re, and overestimation of NEP, by the EC method. Accounting for these discrepancies would substantially improve the our estimates of the terrestrial carbon budget .},
doi = {10.1016/j.agrformet.2017.07.023},
journal = {Agricultural and Forest Meteorology},
number = 15 December 2017,
volume = 247,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2017},
month = {Fri Dec 15 00:00:00 EST 2017}
}