Forest–atmosphere carbon dioxide exchange in eastern Siberia

• Published in: Agricultural and forest meteorology Vol. 90; no. 4; pp. 291 - 306
• Main Authors: Hollinger, D.Y., Kelliher, F.M., Schulze, E.-D., Bauer, G., Arneth, A., Byers, J.N., Hunt, J.E., McSeveny, T.M., Kobak, K.I., Milukova, I., Sogatchev, A., Tatarinov, F., Varlargin, A., Ziegler, W., Vygodskaya, N.N.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30-04-1998
• Subjects: ATMOSFERA; ATMOSPHERE; Boreal forest; Carbon balance; CARBON DIOXIDE; CO 2; DIOXIDO DE CARBONO; DIOXYDE DE CARBONE; ECHANGE GAZEUX; Eddy correlation; ESTOMA; FEDERACION DE RUSIA; FEDERATION DE RUSSIE; GAS EXCHANGE; INTERCAMBIO DE GASES; Larix; LARIX GMELINII; RUSSIAN FEDERATION; STOMATA; Stomatal control; STOMATE; Eastern Siberia, Russian Federation; Larix; CO 2; Stomatal control; Boreal forest; Eddy correlation; Carbon balance
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/S0168-1923(98)00057-4

We investigated the daily exchange of CO
2 between undisturbed
Larix gmelinii (Rupr.) Rupr. forest and the atmosphere at a remote Siberian site during July and August of 1993. Our goal was to measure and partition total CO
2 exchanges into aboveground and belowground components by measuring forest and understory eddy and storage fluxes and then to determine the relationships between the environmental factors and these observations of ecosystem metabolism. Maximum net CO
2 uptake of the forest ecosystem was extremely low compared to the forests elsewhere, reaching a peak of only ∼5
μmol
m
−2
s
−1 late in the morning. Net ecosystem CO
2 uptake increased with increasing photosynthetically active photon flux density (PPFD) and decreased as the atmospheric water vapor saturation deficit (
D) increased. Daytime ecosystem CO
2 uptake increased immediately after rain and declined sharply after about six days of drought. Ecosystem respiration at night averaged ∼2.4
μmol
m
−2
s
−1 with about 40% of this coming from the forest floor (roots and heterotrophs). The relationship between the understory eddy flux and soil temperature at 5
cm followed an Arrhenius model, increasing exponentially with temperature (Q
10∼2.3) so that on hot summer afternoons the ecosystem became a source of CO
2. Tree canopy CO
2 exchange was calculated as the difference between above and below canopy eddy flux. Canopy uptake saturated at ∼6
μmol CO
2
m
−2
s
−1 for a PPFD above 500
μmol
m
−2
s
−1 and decreased with increasing
D. The optimal stomatal control model of
Mäkelä et al. (1996) was used as a `big leaf' canopy model with parameter values determined by the non-linear least squares. The model accurately simulated the response of the forest to light, saturation deficit and drought. The precision of the model was such that the daily pattern of residuals between modeled and measured forest exchange reproduced the component storage flux. The model and independent leaf-level measurements suggest that the marginal water cost of plant C gain in
Larix gmelinii is more similar to values from deciduous or desert species than other boreal forests. During the middle of the summer, the
L.
gmelinii forest ecosystem is generally a net sink for CO
2, storing ∼0.75
g
C
m
−2
d
−1.