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RISS 인기검색어
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- 저자 : Dennis Otieno (검색결과 3 건)
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Laiju, Nahida,Otieno, Dennis,Jung, Eun-Young,Lee, Bo-Ra,Tenhunen, John,Lim, Jong-Hwan,Sung, Joo-Han,Kang, Sin-Kyu The Ecological Society of Korea 2012 Journal of Ecology and Environment Vol.35 No.3
Sap flux density (SFD) measurements were used, in combination with morphological characteristics of trees and forest structure, to calculate whole-tree transpiration, stand transpiration (St) and mean canopy stomatal conductance (Gs). Analysis based on the relationships between the morphological characteristics of trees and whole tree water use, and on the responses of SFD and Gs to short wave radiation (RR), vapor pressure deficit (VPD) and soil water content (SWC) during drought and non-drought periods were conducted. The results showed a strong positive correlation between whole tree transpiration and both tree diameter at breast height (DBH) ($r^2$ = 0.95, P < 0.05) and sapwood area (SA) ($r^2$ = 0.98, P < 0.05). Relationships between SFD and DBH ($r^2$ = 0.25), as well as SA ($r^2$ = 0.17) were weak. Daily SFD of Quercus serrata Thunb was closely related to VPD and RR. Although operating at different time scales, RR and VPD were important interacting environmental controls of tree water use. SFD increased with increasing VPD (<1 kPa) and RR. SWC had a considerable effect on stand transpiration during the drought period. The relationships between SFD, VPD and RR were distorted when SWC dropped below 35%.
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Nahida Laiju,강신규,Dennis Otieno,정은영,이보라,John Tenhunen,임종환,성주한 한국생태학회 2012 Journal of Ecology and Environment Vol.35 No.3
Sap flux density (SFD) measurements were used, in combination with morphological characteristics of trees and forest structure, to calculate whole-tree transpiration, stand transpiration (St) and mean canopy stomatal conductance (Gs). Analysis based on the relationships between the morphological characteristics of trees and whole tree water use, and on the responses of SFD and Gs to short wave radiation (RR), vapor pressure deficit (VPD) and soil water content (SWC) during drought and non-drought periods were conducted. The results showed a strong positive correlation between whole tree transpiration and both tree diameter at breast height (DBH) (r2 = 0.95, P < 0.05) and sapwood area (SA) (r2 = 0.98,P < 0.05). Relationships between SFD and DBH (r2 = 0.25), as well as SA (r2 = 0.17) were weak. Daily SFD of Quercus serrata Thunb was closely related to VPD and RR. Although operating at different time scales, RR and VPD were important interacting environmental controls of tree water use. SFD increased with increasing VPD (<1 kPa) and RR. SWC had a considerable effect on stand transpiration during the drought period. The relationships between SFD, VPD and RR were distorted when SWC dropped below 35%.
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Yue-Lin Li,Guo-Yi Zhou,De-Qiang Zhang,Katherine Owen Wenigmann,Dennis Otieno,John Tenhunen,Qian-Mei Zhang,Jun-Hua Yan 한국기상학회 2012 Asia-Pacific Journal of Atmospheric Sciences Vol.48 No.1
CO2 fluxes were measured continuously for three years (2003-2005) using the eddy covariance technique for the canopy layer with a height of 27 m above the ground in a dominant subtropical evergreen forest in Dinghushan, South China. By applying gapfilling methods, we quantified the different components of the carbon fluxes (net ecosystem exchange (NEE)), gross primary production (GPP) and ecosystem respiration (Reco) in order to assess the effects of meteorological variables on these fluxes and the atmospherecanopy interactions on the forest carbon cycle. Our results showed that monthly average daily maximum net CO2 exchange of the whole ecosystem varied from −3.79 to −14.24 μmol m−2 s−1 and was linearly related to photosynthetic active radiation. The Dinghushan forest acted as a net carbon sink of −488 g C m−2 y−1, with a GPP of 1448 g Cm−2 y−1, and a Reco of 961 g C m−2 y−1.Using a carboxylase-based model, we compared the predicted fluxes of CO2 with measurements. GPP was modelled as 1443 g C m−2 y−1, and the model inversion results helped to explain ca. 90% of temporal variability of the measured ecosystem fluxes. Contribution of CO2 fluxes in the subtropical forest in the dry season (October-March) was 62.2% of the annual total from the whole forest ecosystem. On average, 43.3%of the net annual carbon sink occurred between October and December, indicating that this time period is an important stage for uptake of CO2 by the forest ecosystem from the atmosphere. Carbon uptake in the evergreen forest ecosystem is an indicator of the interaction of between the atmosphere and the canopy, especially in terms of driving climate factors such as temperature and rainfall events. We found that the Dinghushan evergreen forest is acting as a carbon sink almost year-round. The study can improve the evaluation of the net carbon uptake of tropical monsoon evergreen forest ecosystem in south China region under climate change conditions.
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