Open AccessInterannual variability and timing of growing‐season CO 2 exchange in a boreal forest
Author(s) -
Suni Tanja,
Berninger Frank,
Markkanen Tiina,
Keronen Petri,
Rannik Üllar,
Vesala Timo
Publication year - 2003
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002jd002381
Subject(s) - growing season , eddy covariance , environmental science , ecosystem respiration , scots pine , carbon sink , seasonality , boreal , ecosystem , atmospheric sciences , carbon cycle , sink (geography) , climatology , ecology , biology , geography , pinus <genus> , botany , cartography , geology
We studied the interannual variability of cumulative net ecosystem CO 2 exchange (NEE) and its connection with cumulative or average climatic variables during five growing seasons. The analysis was based on a 5‐year‐long time series of CO 2 flux measured from April 1996 to April 2001 in a Scots pine forest in southern Finland by the eddy covariance technique. The onset of the ecosystem growing season was best connected with air temperature, and the end of the growing season was best connected with day length. With these variables we were able to predict the timing and the length of each growing season within 0–3 days. The forest was a sink of carbon with little interannual variability: The uptake during the four full growing seasons varied by 80 g C m −2 , ranging from 230 to 310 g C m −2 . The estimated winter release each year varied between 60 and 90 g C m −2 . The interannual variation in seasonal (spring, summer, autumn) carbon exchange ranged from 30 g C m −2 in autumn and spring to 80 g C m −2 in summer. The average climatic variables explained the variability of the seasonal or growing‐season cumulative NEE only partly. Both the daytime and the nighttime CO 2 fluxes contributed markedly to the variability in carbon exchange, indicating that photosynthesis and respiration have an equally important influence on NEE.