Thermal plasticity of photosynthesis: the role of acclimation in forest responses to a warming climate

Abstract

The increasing air temperatures central to climate change predictions have the potential to alter forest ecosystem function and structure by exceeding temperatures optimal for carbon gain. Such changes are projected to threaten survival of sensitive species, leading to local extinctions, range migrations, and altered forest composition. This study investigated photosynthetic sensitivity to temperature and the potential for acclimation in relation to the climatic provenance of five species of deciduous trees, Liquidambar styraciflua, Quercus rubra, Quercus falcata, Betula alleghaniensis, and Populus grandidentata. Open-top chambers supplied three levels of warming ( 1 0, 1 2, and 1 4 1C above ambient) over 3 years, tracking natural temperature variability. Optimal temperature for CO 2 assimilation was strongly correlated with daytime temperature in all treatments, but assimilation rates at those optima were comparable. Adjustment of thermal optima was confirmed in all species, whether temperatures varied with season or treatment, and regardless of climate in the species' range or provenance of the plant material. Temperature optima from 171 to 341 were observed. Across species, acclimation potentials varied from 0.55 1C to 1.07 1C per degree change in daytime temperature. Responses to the temperature manipulation were not different from the seasonal acclimation observed in mature indigenous trees, suggesting that photosynthetic responses should not be modeled using static temperature functions, but should incorporate an adjustment to account for acclimation. The high degree of homeostasis observed indicates that direct impacts of climatic warming on forest productivity, species survival, and range limits may be less than predicted by existing models.

Future challenges of representing land-processes in studies on land-atmosphere interactions

“…When exposed to different growth environments, either in controlled experiments or as part of natural weather fluctuations, some plant species will rapidly acclimate their response patterns. This acclimation capacity is reflected for instance in altered photosynthesis and respiration rates, water use efficiency or above-to-belowground carbon allocation (Atkin and Tjoelker, 2003;Lloyd et al, 2002;Arneth et al, 2006;Gunderson et al, 2010;Hikosaka et al, 2006;Kozlowski and Pallardy, 2002). In global terrestrial models, however, equations for process-responses to changing environment and parameters used in these equations are typically set to be constant, at least within the same vegetation functional units.…”

Leaf-Level Gas Exchange and Foliar Chemistry of Common Old-Field Species Responding to Warming and Precipitation Treatments

“…Warming can also suppress photosynthetic rates as a result of warming-induced soil moisture stress (De Valpine and Harte 2001). However, some plants can acclimate to temperature changes by altering their physiology, thereby retaining similar or potentially even higher photosynthetic rates in warmer conditions (Mooney and West 1964;Strain et al 1976;Berry and Bjö rkman 1980;Säll and Pettersson 1994;Zhou et al 2007;Gunderson et al 2009). …”

Modelling temperature acclimation effects on the carbon dynamics of forest ecosystems in the conterminous United States

“…In our study we incorporate a general linear relationship for temperature acclimation for all the forest types across the conterminous United States. However, many studies have shown that the degree of the acclimation is highly diverse in different species and in different regions (Mooney et al, 1978;Huner et al, 1993;Dewar et al, 1999;Bunce, 2000;Gunderson et al, 2000;Gunderson et al, 2010). Thus, future study should consider the spatial and inter-species heterogeneity of acclimation in response to temperature variations when more data are available.…”

“…For example, coupled models of climate and terrestrial biosphere functions predict a continuous increase in average global temperatures of between 1.5 and 48C with CO 2 concentrations rising to between 800 and 1000 ppm (Friedlingstein et al, 2006;Gunderson et al, 2010). In the period 2090Á2099, increases in mean surface air temperature and the uncertainty associated with these increases, relative to the period 1980Á1999, are estimated to be between 1.8 and 48C in various emission scenarios using multiple climate models (Meehl et al, 2007).…”