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Apparent Winter CO2...
Apparent Winter CO2 uptake by a boreal forest due to decoupling
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- Jocher, Georg (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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- Ottosson Löfvenius, Mikaell (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Enheten för skoglig fältforskning,Department of Forest Ecology and Management,Unit for Field-based Forest Research
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- De Simon, Giuseppe (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Enheten för skoglig fältforskning,Unit for Field-based Forest Research
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- Hörnlund, Thomas (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Enheten för skoglig fältforskning,Unit for Field-based Forest Research
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- Linder, Sune (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för sydsvensk skogsvetenskap,Southern Swedish Forest Research Centre
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- Lundmark, Tomas (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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- Marshall, John (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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- Nilsson, Mats (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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- Näsholm, Torgny (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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- Tarvainen, Lasse (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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- Öquist, Mats (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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- Peichl, Matthias (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management
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(creator_code:org_t)
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- Elsevier BV, 2017
- 2017
- Engelska.
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923 .- 1873-2240. ; 232, s. 23-34
- Relaterad länk:
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https://res.slu.se/i...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Net uptake of carbon dioxide (CO2) was observed during the winter when using the eddy covariance (EC) technique above a 90-year-old Scots pine (Pinus sylvestris L.) stand in northern Sweden. This uptake occurred despite photosynthetic dormancy. This discrepancy led us to investigate the potential impact of decoupling of below- and above-canopy air mass flow and accompanying below-canopy horizontal advection on these measurements. We used the correlation of above- and below-canopy standard deviation of vertical wind speed (sigma(w)), derived from EC measurements above and below the canopy, as the main mixing criterion. We identified 0.33 m s(-1) and 0.06 m s(-1) as site-specific o thresholds for above and below canopy, respectively, to reach the fully coupled state. Decoupling was observed in 45% of all cases during the measurement period (5.11.2014-25.2.2015). After filtering out decoupled periods the above-canopy mean winter NEE shifted from -0.52 mu mol m(-2) s(-1) to a more reasonable positive value of 0.31 mu mol m(-2) s(-1). None of the above-canopy data filtering criteria we tested (i.e., friction velocity threshold; horizontal wind speed threshold; single-level sigma(w) threshold) ensured sufficient mixing. All missed critical periods that were detected only by the two-level filtering approach. Tower-surrounding topography induced a predominant below-canopy wind direction and consequent wind shear between above- and below-canopy air masses. These processes may foster decoupling and below-canopy removal of CO2 rich air. To determine how broadly such a topographical influence might apply, we compared the topography surrounding our tower to that surrounding other forest flux sites worldwide. Medians of maximum elevation differences within 300m and 1000 m around 110 FLUXNET forest EC towers were 24 m and 66 m, respectively, compared to 24 m and 114 m, respectively, at our site. Consequently, below canopy flow may influence above-canopy NEE detections at many forested EC sites. Based on our findings we suggest below-canopy measurements as standard procedure at sites evaluating forest CO2 budgets.
Ämnesord
- LANTBRUKSVETENSKAPER -- Lantbruksvetenskap, skogsbruk och fiske -- Skogsvetenskap (hsv//swe)
- AGRICULTURAL SCIENCES -- Agriculture, Forestry and Fisheries -- Forest Science (hsv//eng)
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- Av författaren/redakt...
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Jocher, Georg
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Ottosson Löfveni ...
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De Simon, Giusep ...
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Hörnlund, Thomas
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Linder, Sune
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Lundmark, Tomas
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visa fler...
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Marshall, John
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Nilsson, Mats
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Näsholm, Torgny
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Tarvainen, Lasse
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Öquist, Mats
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Peichl, Matthias
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visa färre...
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