Anna M Jensen1, Jeffrey M Warren2, Paul J Hanson2, Joanne Childs2, Stan D Wullschleger2. 1. Climate Change Science Institute, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6301, USA Anna.Jensen@lnu.se. 2. Climate Change Science Institute, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6301, USA.
Abstract
BACKGROUND AND AIMS: The carbon (C) balance of boreal terrestrial ecosystems is sensitive to increasing temperature, but the direction and thresholds of responses are uncertain. Annual C uptake in Picea and other evergreen boreal conifers is dependent on seasonal- and cohort-specific photosynthetic and respiratory temperature response functions, so this study examined the physiological significance of maintaining multiple foliar cohorts for Picea mariana trees within an ombrotrophic bog ecosystem in Minnesota, USA. METHODS: Measurements were taken on multiple cohorts of needles for photosynthetic capacity, foliar respiration (Rd) and leaf biochemistry and morphology of mature trees from April to October over 4 years. The results were applied to a simple model of canopy photosynthesis in order to simulate annual C uptake by cohort age under ambient and elevated temperature scenarios. KEY RESULTS: Temperature responses of key photosynthetic parameters [i.e. light-saturated rate of CO2 assimilation (Asat), rate of Rubisco carboxylation (Vcmax) and electron transport rate (Jmax)] were dependent on season and generally less responsive in the developing current-year (Y0) needles compared with 1-year-old (Y1) or 2-year-old (Y2) foliage. Temperature optimums ranged from 18·7 to 23·7, 31·3 to 38·3 and 28·7 to 36·7 °C for Asat, Vcmax and Jmax, respectively. Foliar cohorts differed in their morphology and photosynthetic capacity, which resulted in 64 % of modelled annual stand C uptake from Y1&2 cohorts (LAI 0·67 m(2 )m(-2)) and just 36 % from Y0 cohorts (LAI 0·52 m(2 )m(-2)). Under warmer climate change scenarios, the contribution of Y0 cohorts was even less; e.g. 31 % of annual C uptake for a modelled 9 °C rise in mean summer temperatures. Results suggest that net annual C uptake by P. mariana could increase under elevated temperature, and become more dependent on older foliar cohorts. CONCLUSIONS: Collectively, this study illustrates the physiological and ecological significance of different foliar cohorts, and indicates the need for seasonal- and cohort-specific model parameterization when estimating C uptake capacity of boreal forest ecosystems under ambient or future temperature scenarios. Published by Oxford University Press on behalf of the Annals of Botany Company 2015. This work is written by US Government employees and is in the public domain in the US.
BACKGROUND AND AIMS: The carbon (C) balance of boreal terrestrial ecosystems is sensitive to increasing temperature, but the direction and thresholds of responses are uncertain. Annual C uptake in Picea and other evergreen boreal conifers is dependent on seasonal- and cohort-specific photosynthetic and respiratory temperature response functions, so this study examined the physiological significance of maintaining multiple foliar cohorts for Picea mariana trees within an ombrotrophic bog ecosystem in Minnesota, USA. METHODS: Measurements were taken on multiple cohorts of needles for photosynthetic capacity, foliar respiration (Rd) and leaf biochemistry and morphology of mature trees from April to October over 4 years. The results were applied to a simple model of canopy photosynthesis in order to simulate annual C uptake by cohort age under ambient and elevated temperature scenarios. KEY RESULTS: Temperature responses of key photosynthetic parameters [i.e. light-saturated rate of CO2 assimilation (Asat), rate of Rubisco carboxylation (Vcmax) and electron transport rate (Jmax)] were dependent on season and generally less responsive in the developing current-year (Y0) needles compared with 1-year-old (Y1) or 2-year-old (Y2) foliage. Temperature optimums ranged from 18·7 to 23·7, 31·3 to 38·3 and 28·7 to 36·7 °C for Asat, Vcmax and Jmax, respectively. Foliar cohorts differed in their morphology and photosynthetic capacity, which resulted in 64 % of modelled annual stand C uptake from Y1&2 cohorts (LAI 0·67 m(2 )m(-2)) and just 36 % from Y0 cohorts (LAI 0·52 m(2 )m(-2)). Under warmer climate change scenarios, the contribution of Y0 cohorts was even less; e.g. 31 % of annual C uptake for a modelled 9 °C rise in mean summer temperatures. Results suggest that net annual C uptake by P. mariana could increase under elevated temperature, and become more dependent on older foliar cohorts. CONCLUSIONS: Collectively, this study illustrates the physiological and ecological significance of different foliar cohorts, and indicates the need for seasonal- and cohort-specific model parameterization when estimating C uptake capacity of boreal forest ecosystems under ambient or future temperature scenarios. Published by Oxford University Press on behalf of the Annals of Botany Company 2015. This work is written by US Government employees and is in the public domain in the US.
Authors: Sanna Sevanto; Tanja Suni; Jukka Pumpanen; Tiia Grönholm; Pasi Kolari; Eero Nikinmaa; Pertti Hari; Timo Vesala Journal: Tree Physiol Date: 2006-06 Impact factor: 4.196
Authors: Russell K Monson; Jed P Sparks; Todd N Rosenstiel; Laura E Scott-Denton; Travis E Huxman; Peter C Harley; Andrew A Turnipseed; Sean P Burns; Brant Backlund; Jia Hu Journal: Oecologia Date: 2005-10-22 Impact factor: 3.225
Authors: Jakub Hejtmánek; Jan Stejskal; Jaroslav Čepl; Zuzana Lhotáková; Jiří Korecký; Anna Krejzková; Jakub Dvořák; Salvador A Gezan Journal: Front Plant Sci Date: 2022-05-30 Impact factor: 6.627
Authors: Verity G Salmon; Deanne J Brice; Scott Bridgham; Joanne Childs; Jake Graham; Natalie A Griffiths; Kirsten Hofmockel; Colleen M Iversen; Terri M Jicha; Randy K Kolka; Joel E Kostka; Avni Malhotra; Richard J Norby; Jana R Phillips; Daniel Ricciuto; Christopher W Schadt; Stephen D Sebestyen; Xiaoying Shi; Anthony P Walker; Jeffrey M Warren; David J Weston; Xiaojuan Yang; Paul J Hanson Journal: Plant Soil Date: 2021-07-17 Impact factor: 4.993
Authors: Pertti Hari; Tuomas Aakala; Emmi Hilasvuori; Risto Häkkinen; Atte Korhola; Mikko Korpela; Tapio Linkosalo; Harri Mäkinen; Eero Nikinmaa; Pekka Nöjd; Heikki Seppä; Mika Sulkava; Juhani Terhivuo; Heikki Tuomenvirta; Jan Weckström; Jaakko Hollmén Journal: PLoS One Date: 2017-06-29 Impact factor: 3.240