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Statements

Subject Item
n2:RIV%2F67179843%3A_____%2F12%3A00379237%21RIV13-AV0-67179843
rdf:type
skos:Concept n19:Vysledek
dcterms:description
Cloud cover affects carbon exchange between biota and the atmosphere. Recent studies have demonstrated that an increase in the diffuse radiation fraction enhances the photosynthetic efficiency of canopies. Although the exact mechanism behind this effect is not clear, a more even distribution of light among leaves across the vertical profile of the canopy is considered to be the most important cause of this difference. To test this hypothesis, the net ecosystem production (NEP) of a Norway spruce forest was measured under cloudy and sunny skies by the eddy covariance method. In parallel, measurements of the diurnal courses of gas exchange and chlorophyll fluorescence parameters were made in the upper sun (5th whorl; 1-year-old needles), middle (8th and 10th whorl; 1- and 2-year-old needles) and lower shade (15th whorl; >2-year-old needles) shoots. The higher diffuse radiation fraction during cloudy days resulted in significantly higher ecosystem carbon uptake than at corresponding incident photosynthetic photon flux density on sunny days. Our shoot-level data show that shoots from deep within the canopy contribute substantially to the overall carbon balance during cloudy days. But, although shade-adapted shoots had a markedly positive carbon balance over a 24-h period on cloudy days, their performance was impaired on sunny days contributing only a marginal or even negative carbon balance from the middle and shaded parts of the canopy. The uppermost sun shoots contributed 78% of the total carbon assimilated during a sunny day, but only 43% during a cloudy day. In addition, afternoon depression of canopy NEP and CO2 assimilation rates of the uppermost shoots (5th and 8th whorl) occurred in response to irradiance on sunny days, characterized by significant decreases in CO2 uptake and apparent quantum yield; however, this depression did not occur under cloudy conditions. Stomatal and non-stomatal regulations of carbon assimilation in the afternoon are discussed. Cloud cover affects carbon exchange between biota and the atmosphere. Recent studies have demonstrated that an increase in the diffuse radiation fraction enhances the photosynthetic efficiency of canopies. Although the exact mechanism behind this effect is not clear, a more even distribution of light among leaves across the vertical profile of the canopy is considered to be the most important cause of this difference. To test this hypothesis, the net ecosystem production (NEP) of a Norway spruce forest was measured under cloudy and sunny skies by the eddy covariance method. In parallel, measurements of the diurnal courses of gas exchange and chlorophyll fluorescence parameters were made in the upper sun (5th whorl; 1-year-old needles), middle (8th and 10th whorl; 1- and 2-year-old needles) and lower shade (15th whorl; >2-year-old needles) shoots. The higher diffuse radiation fraction during cloudy days resulted in significantly higher ecosystem carbon uptake than at corresponding incident photosynthetic photon flux density on sunny days. Our shoot-level data show that shoots from deep within the canopy contribute substantially to the overall carbon balance during cloudy days. But, although shade-adapted shoots had a markedly positive carbon balance over a 24-h period on cloudy days, their performance was impaired on sunny days contributing only a marginal or even negative carbon balance from the middle and shaded parts of the canopy. The uppermost sun shoots contributed 78% of the total carbon assimilated during a sunny day, but only 43% during a cloudy day. In addition, afternoon depression of canopy NEP and CO2 assimilation rates of the uppermost shoots (5th and 8th whorl) occurred in response to irradiance on sunny days, characterized by significant decreases in CO2 uptake and apparent quantum yield; however, this depression did not occur under cloudy conditions. Stomatal and non-stomatal regulations of carbon assimilation in the afternoon are discussed.
dcterms:title
Impact of clear and cloudy sky conditions on the vertical distribution of photosynthetic CO2 uptake within a spruce canopy Impact of clear and cloudy sky conditions on the vertical distribution of photosynthetic CO2 uptake within a spruce canopy
skos:prefLabel
Impact of clear and cloudy sky conditions on the vertical distribution of photosynthetic CO2 uptake within a spruce canopy Impact of clear and cloudy sky conditions on the vertical distribution of photosynthetic CO2 uptake within a spruce canopy
skos:notation
RIV/67179843:_____/12:00379237!RIV13-AV0-67179843
n19:predkladatel
n20:ico%3A67179843
n3:aktivita
n12:Z n12:P n12:I
n3:aktivity
I, P(2B06068), P(ED1.1.00/02.0073), P(IAA600870701), P(LM2010007), P(SP/2D1/93/07), Z(AV0Z60870520)
n3:cisloPeriodika
1
n3:dodaniDat
n15:2013
n3:domaciTvurceVysledku
n8:8834822 n8:7674864 n8:1241346 n8:3280551 n8:3273296 n8:5420113 n8:3692574 n8:9057765 n8:5693314 n8:6730256 n8:7131038
n3:druhVysledku
n7:J
n3:duvernostUdaju
n10:S
n3:entitaPredkladatele
n16:predkladatel
n3:idSjednocenehoVysledku
140584
n3:idVysledku
RIV/67179843:_____/12:00379237
n3:jazykVysledku
n17:eng
n3:klicovaSlova
afternoon depression of photosynthesis; daily course; diffuse/direct radiation; eddy covariance; light response curve; light use efficiency; light response curve; light use efficiency; net ecosystem production; photorespiration; stomatal conductance
n3:klicoveSlovo
n9:light%20response%20curve n9:stomatal%20conductance n9:light%20use%20efficiency n9:daily%20course n9:afternoon%20depression%20of%20photosynthesis n9:net%20ecosystem%20production n9:eddy%20covariance n9:photorespiration n9:diffuse%2Fdirect%20radiation
n3:kodStatuVydavatele
GB - Spojené království Velké Británie a Severního Irska
n3:kontrolniKodProRIV
[FF4F1EC62ABF]
n3:nazevZdroje
Functional Ecology
n3:obor
n18:EH
n3:pocetDomacichTvurcuVysledku
11
n3:pocetTvurcuVysledku
13
n3:projekt
n4:2B06068 n4:LM2010007 n4:IAA600870701 n4:SP%2F2D1%2F93%2F07 n4:ED1.1.00%2F02.0073
n3:rokUplatneniVysledku
n15:2012
n3:svazekPeriodika
26
n3:tvurceVysledku
Grace, J. Pokorný, Radek Havránková, Kateřina Holišová, Petra Ač, Alexander Urban, Otmar Klem, Karel Navrátil, M. Tomášková, Ivana Šprtová, Mirka Zitová, Martina Kozlová, Klára Špunda, Vladimír
n3:wos
000299204300007
n3:zamer
n13:AV0Z60870520
s:issn
0269-8463
s:numberOfPages
10
n11:doi
10.1111/j.1365-2435.2011.01934.x