title: Vertical variations in wood CO2 efflux for live emergent trees in a Bornean tropical rainforest.
abstract: Difficult access to 40-m-tall emergent trees in tropical rainforests has resulted in a lack of data related to vertical variations in wood CO2 efflux, even though significant variations in wood CO2 efflux are an important source of errors when estimating whole-tree total wood CO2 efflux. This study aimed to clarify vertical variations in wood CO2 efflux for emergent trees and to document the impact of the variations on the whole-tree estimates of stem and branch CO2 efflux. First, we measured wood CO2 efflux and factors related to tree morphology and environment for seven live emergent trees of two dipterocarp species at four to seven heights of up to ∼ 40 m for each tree using ladders and a crane. No systematic tendencies in vertical variations were observed for all the trees. Wood CO2 efflux was not affected by stem and air temperature, stem diameter, stem height or stem growth. The ratios of wood CO2 efflux at the treetop to that at breast height were larger in emergent trees with relatively smaller diameters at breast height. Second, we compared whole-tree stem CO2 efflux estimates using vertical measurements with those based on solely breast height measurements. We found similar whole-tree stem CO2 efflux estimates regardless of the patterns of vertical variations in CO2 efflux because the surface area in the canopy, where wood CO2 efflux often differed from that at breast height, was very small compared with that at low stem heights, resulting in little effect of the vertical variations on the estimate. Additionally, whole-tree branch CO2 efflux estimates using measured wood CO2 efflux in the canopy were considerably different from those measured using only breast height measurements. Uncertainties in wood CO2 efflux in the canopy did not cause any bias in stem CO2 efflux scaling, but affected branch CO2 efflux.
authors.affiliation: Field Science Center for Northern Biosphere, Hokkaido University, 250 Tokuda, Nayoro, Hokkaido 096-0071, Japan Kasuya Research Forest, Kyushu University, Sasaguri, Fukuoka 811-2415, Japan ayumi.katayama0920@gmail.com.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Katayama
authors.affiliation: School of Forestry and Resource Conservation, National Taiwan University, Taipei 106-17, Taiwan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kume
authors.affiliation: The Hakubi Research Center for Advanced Research, Kyoto University, Kyoto 606-8302, Japan.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Komatsu
authors.affiliation: School of Human Science and Environment, University of Hyogo, Himeji, Hyogo 670-0092, Japan.
authors.forename: Mizue
authors.initials: M
authors.lastname: Ohashi
authors.affiliation: Faculty of Agriculture, University of the Ryukyus, Okinawa 903-0213, Japan.
authors.forename: Kazuho
authors.initials: K
authors.lastname: Matsumoto
authors.affiliation: Kasuya Research Forest, Kyushu University, Sasaguri, Fukuoka 811-2415, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Ichihashi
authors.affiliation: Hydrospheric Atmospheric Research Center, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan.
authors.forename: Tomo'omi
authors.initials: T
authors.lastname: Kumagai
authors.affiliation: Kasuya Research Forest, Kyushu University, Sasaguri, Fukuoka 811-2415, Japan.
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Otsuki
mesh_terms: D001893:Borneo; D002245:Carbon Dioxide / Q000378:metabolism*; D053958:Dipterocarpaceae / Q000254:growth & development / Q000502:physiology*; D008296:Malaysia; D018526:Plant Transpiration; D065947:Rainforest; D014197:Trees / Q000254:growth & development / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide
keywords: carbon allocation; dipterocarp; scaling; stem respiration