Autumn photosynthetic decline and growth cessation in seedlings of white spruce are decoupled under warming and photoperiod manipulations. (20th March 2017)

• Record Type: Journal Article
• Authors: Stinziano, Joseph R.; Way, Danielle A.
• Is Part Of: Plant, cell and environment. Volume 40:Number 8(2017)
• Page Start: 1296
• Page End: 1316
• Publication Date: 2017-03-20
• Subjects: biomass -- climate change -- day length -- Jmax -- Vcmax -- phenology; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.12917
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: Climate warming is expected to increase the seasonal duration of photosynthetic carbon fixation and tree growth in high‐latitude forests. However, photoperiod, a crucial cue for seasonality, will remain constant, which may constrain tree responses to warming. We investigated the effects of temperature and photoperiod on weekly changes in photosynthetic capacity, leaf biochemistry and growth in seedlings of a boreal evergreen conifer, white spruce [ Picea glauca (Moench) Voss]. Warming delayed autumn declines in photosynthetic capacity, extending the period when seedlings had high carbon uptake. While photoperiod was correlated with photosynthetic capacity, short photoperiods did not constrain the maintenance of high photosynthetic capacity under warming. Rubisco concentration dynamics were affected by temperature but not photoperiod, while leaf pigment concentrations were unaffected by treatments. Respiration rates at 25 °C were stimulated by photoperiod, although respiration at the growth temperatures was increased in warming treatments. Seedling growth was stimulated by increased photoperiod and suppressed by warming. We demonstrate that temperature is a stronger control on the seasonal timing of photosynthetic down‐regulation than is photoperiod. Thus, while warming can stimulate carbon uptake in boreal conifers, the extra carbon may be directed towards respiration rather than biomass, potentially limiting carbon sequestration under climate change. Abstract : Photoperiod may limit the ability of trees to respond to climate warming during autumn. In this study, we investigated the impact of photoperiod and temperature manipulations on photosynthetic physiology and growth in white spruce ( Picea glauca ) seedlings. We found that temperature limited photosynthetic physiology while photoperiod limited growth, and climate warming may cause a desynchronization between autumn photosynthesis and growth. Therefore, warming‐induced stimulation of photosynthesis during autumn may not lead to enhanced carbon sequestration, as this carbon may be allocated to more labile pools instead.