Predicting ecosystem carbon balance in a warming Arctic: the importance of long-term thermal acclimation potential and inhibitory effects of light on respiration

Abstract

The carbon balance of Arctic ecosystems is particularly sensitive to global environmental change. Leaf respiration (R), a temperature-dependent key process in determining the carbon balance, is not well-understood in Arctic plants. The potential for plants to acclimate to warmer conditions could strongly impact future global carbon balance. Two key unanswered questions are (1) whether short-term temperature responses can predict long-term respiratory responses to growth in elevated temperatures and (2) to what extent the constant daylight conditions of the Arctic growing season inhibit leaf respiration. In two dominant Arctic species Eriophorum vaginatum (tussock grass) and Betula nana (woody shrub), we assessed the extent of respiratory inhibition in the light (RL/RD), respiratory response to short-term temperature change, and respiratory acclimation to long-term warming treatments. We found that R of both species is strongly inhibited by light (averaging 35% across all measurement temperatures). In E. vaginatum both RL and RD acclimated to the long-term warming treatment, reducing the magnitude of respiratory response relative to the short-term response to temperature increase. In B. nana, both RL and RD responded to short-term temperature increase but showed no acclimation to the long-term warming. The ability to predict plant respiratory response to global warming with short-term temperature responses will depend on species-specific acclimation potential and the differential response of RL and RD to temperature. With projected woody shrub encroachment in Arctic tundra and continued warming, changing species dominance between these two functional groups, may impact ecosystem respiratory response and carbon balance.

Grassland responses to increased rainfall depend on the timescale of forcing

“…The prevalence of thresholds, biotic interactions, acclimation and adaptation in ecological responses to climate change means that this translation may not be straightforward. Hence, experimental results can poorly predict natural patterns that develop over longer timescales (Sandel et al, 2010), initial responses to experimental manipulations may poorly predict longer-term effects (Chapin et al, 1995;Harte & Shaw, 1995;Hollister et al, 2005;Wiedermann et al, 2007), populations that show a strong response to initial exposure to certain conditions may show little or no response over longer terms (Shaver et al, 2000;Donelson et al, 2011;Grottoli et al, 2014;Mclaughlin et al, 2014;Smith et al, 2015), and populations that show little response to initial or itinerant exposure may show pronounced responses to repeated or sustained exposure (Kirby & Beaugrand, 2009;Kortsch et al, 2012;Grottoli et al, 2014).…”

“…Physiological thresholds and tipping points can likewise cause ecological trajectories to deviate in sudden and unexpected ways under sustained or larger-magnitude forcing that are not apparent from itinerant or smaller forcing (Kirby & Beaugrand, 2009;Kortsch et al, 2012;Nelson et al, 2013;Grottoli et al, 2014). Species may acclimate to changing climate, so that initially pronounced effects taper off with repeated exposure (Donelson et al, 2011;Grottoli et al, 2014;Mclaughlin et al, 2014). Populations may also adapt to selective pressures of changing climate (Colautti & Barrett, 2013;Van Asch et al, 2013).…”

Light inhibition of foliar respiration in response to soil water availability and seasonal changes in temperature in Mediterranean holm oak (Quercus ilex) forest

“…These large potential variations between measured RL and RD under different experimental conditions are important because the level to which they are actually expressed in the field will determine the extent to which variations in R impact on net CO2 exchange in individual plants and whole ecosystems. Failure to account for light inhibition of leaf R leads to large over-and under-estimates of ecosystem respiration and net primary productivity, respectively (Lloyd et al 2002;Wohlfahrt et al 2005;Atkin et al 2006;Wingate et al 2007;McLaughlin et al 2014).…”

Scaling Thermal Properties from the Leaf to the Canopy in the Alaskan Arctic Tundra

“…Temperature (usually quantified by soil or air temperature) has been known to greatly influence plant physiology and ecology (Berry and Bjorkman, 1980;Walther et al, 2002;Parmesan and Yohe, 2003;Elmendorf et al, 2012;Gottfried et al, 2012). On a physiological scale, warming experiments us-ing greenhouses or infrared heaters applied across a range of species and ecosystems have shown that physiological rates, including photosynthetic and respiratory rates, change as a function of air and/ or soil temperature (Hobbie and Chapin, 1998;Zhou et al, 2007;Zhao and Liu, 2009;Heskel et al, 2013Heskel et al, , 2014McLaughlin et al, 2014;Atkin et al, 2015). On a larger, ecological scale, species ranges are strongly influenced by air temperature-species have evolved to optimize their performance in their respective climate, as demonstrated by evolutionary convergence across phylogenetically unrelated species in climatically similar regions (Mooney, 1977;Beard, 1978;Bunce et al, 1979;Orians and Paine, 1983;Stephenson, 1990;Atkin et al, 2015).…”