Sensitivity and uncertainty of the carbon balance of a Pacific Northwest Douglas-fir forest during an El Niño/La Niña cycle

The annual net ecosystem productivity ( F NEP) of a second-growth Douglas-fir stand established in 1949 on the Canadian West Coast varied considerably over the 4-year period between 1998 and 2001. This period included the El Niño/La Niña cycle during the northern hemispheric winters of 1997/1998 and...

Full description

Saved in:

Bibliographic Details
Published in:	Agricultural and forest meteorology 2004-06, Vol.123 (3), p.201-219
Main Authors:	Morgenstern, Kai, Andrew Black, T., Humphreys, Elyn R., Griffis, Timothy J., Drewitt, Gordon B., Cai, Tiebo, Nesic, Zoran, Spittlehouse, David L., Livingston, Nigel J.
Format:	Article
Language:	eng
Subjects:	Agricultural and forest climatology and meteorology. Irrigation. Drainage Agronomy. Soil science and plant productions Biological and medical sciences Carbon balance Douglas-fir Ecosystem photosynthesis Ecosystem respiration Eddy covariance Error analysis Fundamental and applied biological sciences. Psychology General agronomy. Plant production Net ecosystem productivity
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	The annual net ecosystem productivity ( F NEP) of a second-growth Douglas-fir stand established in 1949 on the Canadian West Coast varied considerably over the 4-year period between 1998 and 2001. This period included the El Niño/La Niña cycle during the northern hemispheric winters of 1997/1998 and 1998/1999, offering a unique opportunity to study how a typical forest ecosystem in the Pacific Northwest reacts to interannual climate variability. This was possible even though annual F NEP values calculated from eddy covariance (EC) measurements of CO 2 fluxes were subject to biases. These were largely due to the failure of the EC method to accurately measure losses of CO 2 under low turbulence conditions at night, which caused F NEP overestimates of as much as 90 g C m −2 per year. As these biases were largely unaffected by interannual climate variability, it was possible to reliably quantify interannual differences in F NEP estimates if they were larger than random variability, which was estimated to be ±30 g C m −2 per year at most. Interannual differences were mainly due to differences in ecosystem respiration ( R) between the 4 years. In the year following the 1997/1998 El Niño, high air temperatures led to the highest annual R of the 4 years, while annual gross ecosystem photosynthesis ( P) was only slightly higher than normal. This resulted in 1998 having the lowest F NEP (270 g C m −2 per year) of the 4 years. For 1999, a cool and cloudy La Niña year, F NEP was 360 g C m −2 per year, much higher than 1998, but somewhat lower than the last 2 years, for which F NEP values were 390 and 420 g C m −2 per year, respectively.
ISSN:	0168-1923 1873-2240