Soil CO2 efflux in boreal pine forests in the current climate and under CO2 enrichment and air warming
Niinistö S. (2015). Soil CO2 efflux in boreal pine forests in the current climate and under CO2 enrichment and air warming. https://doi.org/10.14214/df.194
Abstract
The aims of the study were to identify factors related to temporal and spatial variation in forest soil CO2 efflux(Fs), compare measurement chambers, and to test effects of a climate change experiment. The study was based on four-year measurements in upland Scots pine forests.
Momentary plot averages of Fs ranged from 0.04 to 1.12 gCO2m−2 h−1 and annual estimates for the forested area from1750 to 2050 gCO2 m−2. Soil temperature was a dominant predictor of the temporal variation in Fs (R2=76–82%). A temperature and degree days model predicted Fs of independent data within 15% on the average but underestimated it during the peak efflux period (July–August), possibly because of seasonal pattern in growth of roots and mycorrhiza. A comparison sub-study indicated that the reliability of the measurement chambers was not related to the principle i.e. non-steady-state through-flow, non-steady-state non-through-flow or steady-state through-flow.
Spatial variability of Fs within 400 m2 plots in four stands was large; coefficients of variation (CV) ranged from 0.10 to 0.80, with growing season averages of 0.22–0.36. A positive spatial autocorrelation was found at short distances (3–8 m). In data from several stands, thickness of the humus layer explained 28% of the variation in Fs, and with the distance to the closest trees it explained 40%. Fs also correlated with root mass of the humus layer. Between-plot differences in Fs were small.
In the climate change experiment, CO2 enrichment and air warming consistently, but not always significantly,increased Fs in whole-tree chambers. Their combined effect was additive, with no interaction; i.e. +23–37% (elevated CO2), +27–43% (elevated temperature), and +35–59% (combined treatment), depending on year. Air warming was a significant factor in the 4-year data according to ANOVA. Temperature sensitivity of Fs under the warming, however, decreased in the second year.
Keywords
climate change;
elevated temperature;
soil respiration;
carbon flux;
temperature response;
spatial variation
Published 22 May 2015
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Available at https://doi.org/10.14214/df.194 | Download PDF
Original articles
Niinistö S.M., Kellomäki S., Silvola, J. (2011). Seasonality in boreal forest ecosystem affects the use of soil temperature and moisture as predictors of soil CO2 efflux. Biogeosciences 8: 3169–3186.
https://doi.org/10.5194/bg-8-3169-2011
Pumpanen J., Kolari P., Ilvesniemi H., Minkkinen K., Vesala T., Niinistö S., Lohila A., Larmola T., Morero M., Pihlatie M., Janssens I., Curiel Yuste J., Grünzweig JM., Reth S., Subke J.-A., Savage K., Kutsch W., Østreng G., Ziegler W., Anthoni P., Lindroth A., Hari P. (2004). Comparison of different chamber techniques for measuring soil CO2 efflux. Agricultural and Forest Meteorology 123: 159–176.
https://doi.org/10.1016/j.agrformet.2003.12.001
Niinistö S.M., Silvola J., Kellomäki S. (2004). Soil CO2 efflux in a boreal pine forest under atmospheric CO2 enrichment and air warming. Global Change Biology 10(8): 1363–1376.
https://doi.org/10.1111/j.1365-2486.2004.00799.x
Niinistö S.M., Kellomäki S., Ylioja T. (2015). Spatial variability of soil CO2 efflux in boreal pine stands. Manuscript.