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The role of air and soil temperature in the seasonality of photosynthesis and transpiration in a boreal Scots pine ecosystem
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Physics.
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Physics.
2012 (English)In: Agricultural and Forest Meteorology, ISSN 0168-1923, E-ISSN 1873-2240, Vol. 156, 85-103 p.Article in journal (Refereed) Published
Abstract [en]

Photosynthesis and transpiration in boreal forests are restricted by air temperature (T a) and soil temperature (T s), especially in spring after the dormant period, but the extent to which the recovery process is regulated these factors is still uncertain. To examine the role of air temperature and soil temperature, years with three types of typical patterns of temperature rises were identified from 13 years of continuous flux measurements for a Scots pine ecosystem in Hyytiälä, southern Finland. By combining a process-based ecosystem model (CoupModel) with an uncertainty estimation procedure (GLUE), the role of regulating factors was explored and 45 of 51 parameters were found to have reduced uncertainty after calibration. Air temperature was the major limiting factor for photosynthesis in early spring, autumn and winter, but soil temperature was a rather important limiting factor in late spring. Especially during warm spring with a large delay of soil temperature rise both water uptake and photosynthesis was strongly reduced due to low soil temperature. Soil moisture and nitrogen showed indications of being more important for regulating photosynthesis in the summer period. It proved possible to replace the soil temperature acclimation function on photosynthesis and transpiration with a corresponding air temperature function only during warm years with a small delay between T a and T s. Fluxes of photosynthesis and transpiration showed a sensitivity to the carbon footprint representation, as expected from the high spatial variability in soil temperature during the spring of a warm year with a large delay between T a and T s.

Place, publisher, year, edition, pages
2012. Vol. 156, 85-103 p.
Keyword [en]
Carbon and water balance, CoupModel, Generalised likelihood uncertainty estimation (GLUE), Gross primary productivity (GPP), Net ecosystem exchange (NEE), Sensible and latent heat fluxes, Total ecosystem respiration (TER)
National Category
Other Environmental Engineering
Identifiers
URN: urn:nbn:se:kth:diva-40699DOI: 10.1016/j.agrformet.2012.01.006ISI: 000302670500008Scopus ID: 2-s2.0-84862809362OAI: oai:DiVA.org:kth-40699DiVA: diva2:442023
Note

QC 20120328

Available from: 2011-09-20 Created: 2011-09-20 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Impact of cold climate on boreal ecosystem processes: exploring data and model uncertainties
Open this publication in new window or tab >>Impact of cold climate on boreal ecosystem processes: exploring data and model uncertainties
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The impact of cold climate on physical and biological processes, especially the role of air and soil temperature in recovering photosynthesis and transpiration in boreal forests, was investigated in a series of studies. A process-based ecosystem model (CoupModel) considering atmospheric, soil and plant components was evaluated and developed using Generalized Likelihood Uncertainty Estimation (GLUE) and detailed measurements from three different sites. The model accurately described the variability in measurements within days, within years and between years. The forcing environmental conditions were shown to govern both aboveground and belowground processes and regulating carbon, water and heat fluxes. However, the various feedback mechanisms between vegetation and environmental conditions are still unclear, since simulations with one model assumption could not be rejected when compared with another.

The strong interactions between soil temperature and moisture processes were indicated by the few behavioural models obtained when constrained by combined temperature and moisture criteria. Model performance on sensible and latent heat fluxes and net ecosystem exchange (NEE) also indicated the coupled processes within the system. Diurnal and seasonal courses of eddy flux data in boreal conifer ecosystems were reproduced successfully within defined ranges of parameter values. Air temperature was the major limiting factor for photosynthesis in early spring, autumn and winter, but soil temperature was a rather important limiting factor in late spring. Soil moisture and nitrogen showed indications of being more important for regulating photosynthesis in the summer period. The need for systematic monitoring of the entire system, covering both soil and plant components, was identified as a subject for future studies. The results from this modelling work could be applied to suggest improvements in management of forest and agriculture ecosystems in order to reduce greenhouse gas emissions and to find adaptations to future climate conditions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. x, 31 p.
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1061
Keyword
net ecosystem exchange; sensible and latent heat fluxes; soil temperature; soil moisture; CoupModel; GLUE
National Category
Forest Science
Identifiers
urn:nbn:se:kth:diva-40451 (URN)978-91-7501-104-2 (ISBN)
Public defence
2011-10-07, V1, Teknikringen 76, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
the Nitro-Europe project
Note
QC 20110921Available from: 2011-09-21 Created: 2011-09-15 Last updated: 2011-09-21Bibliographically approved

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