Seasonal variation in foliar carbon exchange in Pinus radiata and Populus deltoides: respiration acclimates fully to changes in temperature but photosynthesis does not

Abstract

We investigated seasonal variation in dark respiration and photosynthesis by measuring gas exchange characteristics on Pinus radiata and Populus deltoides under field conditions each month for 1 year. The field site in the South Island of New Zealand is characterized by large day-to-day and seasonal changes in air temperature. The rate of foliar respiration at a base temperature of 10 1C (R 10 ) in both pine and poplar was found to be greater during autumn and winter and displayed a strong downward adjustment in warmer months. The sensitivity of instantaneous leaf respiration to a 10 1C increase in temperature (Q 10 ) was also greater during the winter period. The net effect of this strong acclimation was that the long-term temperature response of respiration was essentially flat over a wide range of ambient temperatures. Seasonal changes in photosynthesis were sensitive to temperature but largely independent of leaf nitrogen concentration or stomatal conductance. Over the range of day time growth temperatures (5-32 1C), we did not observe strong evidence of photosynthetic acclimation to temperature, and the long-term responses of photosynthetic parameters to ambient temperature were similar to previously published instantaneous responses. The ratio of foliar respiration to photosynthetic capacity (R d /A sat ) was significantly greater in winter than in spring/ summer. This indicates that there is little likelihood that respiration would be stimulated significantly in either of these species with moderate increases in temperature -in fact net carbon uptake was favoured at moderately higher temperatures. Model calculations demonstrate that failing to account for strong thermal acclimation of leaf respiration influences determinations of leaf carbon exchange significantly, especially for the evergreen conifer.

Seasonal controls on net branch CO2 assimilation in sub-Arctic Mountain Birch (Betula pubescens ssp. czerepanovii (Orlova) Hamet-Ahti)

“…At Kevo, we observed disproportionately high values of the respiration parameter in light response curves for Mountain Birch during the early growing season, consistent with the observed seasonality of foliar respiration in other deciduous trees (Collier and Thibodeau, 1995, Ow et al, 2009and Xu and Baldocchi, 2003. The temperature response of whole-branch respiration measured at Abisko also varied seasonally, indicating higher temperature sensitivity during the early season.…”

Acclimation of Foliar Respiration and Photosynthesis in Response to Experimental Warming in a Temperate Steppe in Northern China

“…The acclimation of foliar respiration and photosynthesis is also reflected in R / A ratio which indicates the balance between carbon gain, loss and accumulation [1], [2]. Our results show that the instantaneous (<5 h) warming at foliage level has non-linearly increased R d / A g ratio, indicating proportionally more carbon loss through R d as T leaf goes up (Fig.…”

Effects of seasonal variation of photosynthetic capacity on the carbon fluxes of a temperate deciduous forest

“…However, there are other aspects of phenology that warrant attention. In particular, seasonal variation of leaf photosynthetic capacity has been shown to affect the functioning of temperate deciduous forests [ Wilson et al ., ; Xu and Baldocchi , ; Grassi et al ., ; Wang et al ., ; Ow et al ., ] and temperate grasslands [ Wolf et al ., ]. In a synthesis of observations, Bauerle et al .…”