The apparent temperature response of leaf respiration depends on the timescale of measurements: a study of two cold climate species (original) (raw)
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Evergreen leaf respiration acclimates to long-term nocturnal warming under field conditions
Global Change Biology, 2007
Acclimation of plant respiration rates (R) to climate warming is highly variable and many results appear contradictory. We tested the recently suggested hypotheses that preexisting, long-lived leaves should exhibit a relatively limited ability for R to acclimate to climate warming, and that acclimation would occur via changes in the short-term temperature sensitivity of respiration. Seedlings of a subalpine, evergreen tree species (Eucalyptus pauciflora) were grown under naturally fluctuating conditions within its natural distribution. We used a free air temperature increase (FATI) system of infra-red ceramic lamps to raise night-time leaf temperatures by 0.3 AE 0.1, 1.3 AE 0.1, and 2.2 AE 0.1 1C above ambient for 1 year. Light-saturated assimilation rates and plant growth did not change with nocturnal FATI treatments. Leaf R measured at prevailing temperatures did not differ between FATI treatments. Within each FATI treatment, nocturnal leaf R was highly sensitive to artificial temperature changes within minutes, and also correlated strongly with natural nocturnal and seasonal temperature variation. The corresponding values of Q 10 of R varied according to time scale of measurements, but did not vary between FATI treatments. Instead, acclimation of R to nocturnal FATI occurred through changes in the base rate of respiration.
Leaf respiration is differentially affected by leaf vs. stand-level night-time warming
Global Change Biology, 2002
Plant respiration is an important physiological process in the global carbon cycle serving as a major carbon flux from the biosphere to the atmosphere. Respiration is sensitive to temperature providing a link between environmental variability, climate change and the global carbon cycle. We measured leaf respiration in Populus deltoides after manipulating the air temperature surrounding part of a single leaf, and compared this to the temperature response of the same leaves after manipulating the temperature of the stand. The short-term temperature response of respiration (Q 10 ± change in the respiration rate with a 10 C increase in leaf temperature) was 1.7 when the leaf temperature was manipulated, but 2.1 when the stand-level temperature was changed. As a result, total night-time carbon release during the five-day experiment was 21% lower when using the Q 10 estimates from the tradition leaf manipulation compared to the stand-level manipulation. We conclude that the temperature response of leaf respiration is related to whole plant carbon and energy demands, and that appropriate experimental procedures are required in examining respiratory CO 2 release under variable temperature conditions.
Convergence in the temperature response of leaf respiration across biomes and plant functional types
Proceedings of the National Academy of Sciences of the United States of America, 2016
Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe its short-term temperature response, and even minor differences in the shape of the response curve can significantly impact estimates of ecosystem carbon release and/or storage. Given this, it is critical to establish whether there are predictable patterns in the shape of the respiration-temperature response curve, and thus in the intrinsic temperature sensitivity of respiration across the globe. Analyzing measurements in a comprehensive database for 231 species spanning 7 biomes, we demonstrate that temperature-dependent increases in leaf respiration do not follow a commonly used exponential function. Instead, we find a decelerating function as leaves warm, r...
2013
We tested whether snow gum (Eucalyptus pauciflora) trees growing in thermally contrasting environments exhibit generalizable temperature (T) response functions of leaf respiration (R) and fluorescence (Fo). Measurements were made on pot-grown saplings and field-grown trees (growing between 1380 and 2110 m a.s.l.). Using a continuous, highresolution protocol, we quantified T response curves of R and Fo -these data were used to identify an algorithm for modelling R-T curves at subcritical T's and establish variations in heat tolerance. For the latter, we quantified Tmax [T where R is maximal] and Tcrit [T where Fo rises rapidly]. Tmax ranged from 51 to 57°C, varying with season (e.g. winter > summer). Tcrit ranged from 41 to 49°C in summer and from 58 to 63°C in winter. Thus, surprisingly, leaf energy metabolism was more heat-tolerant in trees experiencing ice-encasement in winter than warmer conditions in summer. A polynomial model fitted to log-transformed R data provided the best description of the T-sensitivity of R (between 10 and 45°C); using these model fits, we found that the negative slope of the Q10-T relationship was greater in winter than in summer.
Global convergence in leaf respiration from estimates of thermal acclimation across time and space
New Phytologist, 2015
Recent compilations of experimental and observational data have documented global temperature-dependent patterns of variation in leaf dark respiration (R), but it remains unclear whether local adjustments in respiration over time (through thermal acclimation) are consistent with the patterns in R found across geographical temperature gradients. We integrated results from two global empirical syntheses into a simple temperaturedependent respiration framework to compare the measured effects of respiration acclimationover-time and variation-across-space to one another, and to a null model in which acclimation is ignored. Using these models, we projected the influence of thermal acclimation on: seasonal variation in R; spatial variation in mean annual R across a global temperature gradient; and future increases in R under climate change. The measured strength of acclimation-overtime produces differences in annual R across spatial temperature gradients that agree well with global variation-across-space. Our models further project that acclimation effects could potentially halve increases in R (compared with the null model) as the climate warms over the 21st Century. Convergence in global temperature-dependent patterns of R indicates that physiological adjustments arising from thermal acclimation are capable of explaining observed variation in leaf respiration at ambient growth temperatures across the globe.
Tree Physiology, 2016
Most vascular plants acclimate respiration to changes in ambient temperature, but explicit tests of these responses in field settings are rare, and how acclimation responses vary in space and time is relatively unstudied, hindering our ability to predict respiratory release of carbon under future climatic conditions. We measured temperature response curves of leaf respiration for three deciduous tree species from 2009 to 2012 in a field warming experiment (+3.4°C above ambient) in both open and understory conditions at two sites in the southern boreal forest in Minnesota, USA. We analyzed the effects of warming on leaf respiration, and how the effects varied among species, times of season (early, middle and late parts of the growing season), sites, habitats (understory, open) and years. We hypothesized that the respiration exponent (Q 10) of the short-term temperature response curve and the degree of acclimation would be smaller under conditions where plants were more likely to be substrate limited, such as in the understory or the margins of the growing season. However, in contrast to these predictions, stable Q 10 and strong respiratory acclimation were consistently observed. For each species, the Q 10 did not vary with experimental warming, nor was its response to warming influenced by time of season, year, site or habitat. Strong leaf respiratory acclimation to warming occurred in each species and was consistent across most sources of variation. Most of the leaf traits studied were not affected by warming, while the Q 10-leaf nitrogen and R 25-soluble carbohydrate relationships were observed, and shifted with warming, implying that acclimation may be associated with the adjustment in respiratory capacity and its relation to leaf nitrogen and soluble carbohydrate content. Consistent Q 10 and acclimation across habitats, sites, times of season and years suggest that modeling of temperature acclimation may be possible with relatively simple functions.
The New phytologist, 2016
Understanding physiological acclimation of photosynthesis and respiration is important in elucidating the metabolic performance of trees in a changing climate. Does physiological acclimation to climate warming mirror acclimation to seasonal temperature changes? We grew Eucalyptus tereticornis trees in the field for 14 months inside 9-m tall whole-tree chambers tracking ambient air temperature (Tair ) or ambient Tair + 3°C (i.e. 'warmed'). We measured light- and CO2 -saturated net photosynthesis (Amax ) and night-time dark respiration (R) each month at 25°C to quantify acclimation. Tree growth was measured, and leaf nitrogen (N) and total nonstructural carbohydrate (TNC) concentrations were determined to investigate mechanisms of acclimation. Warming reduced Amax and R measured at 25°C compared to ambient-grown trees. Both traits also declined as mean daily Tair increased, and did so in a similar way across temperature treatments. Amax and R (at 25°C) both increased as TNC c...
Tree Physiology, 2017
Quantifying the adjustments of leaf respiration in response to seasonal temperature variation and climate warming is crucial because carbon loss from vegetation is a large but uncertain part of the global carbon cycle. We grew fast-growing Eucalyptus globulus Labill. trees exposed to +3°C warming and elevated CO 2 in 10-m tall whole-tree chambers and measured the temperature responses of leaf mitochondrial respiration, both in light (R Light) and in darkness (R Dark), over a 20-40°C temperature range and during two different seasons. R Light was assessed using the Laisk method. Respiration rates measured at a standard temperature (25°C-R 25) were higher in warm-grown trees and in the warm season, related to higher total leaf nitrogen (N) investment with higher temperatures (both experimental and seasonal), indicating that leaf N concentrations modulated the respiratory capacity to changes in temperature. Once differences in leaf N were accounted for, there were no differences in R 25 but the Q 10 (i.e., short-term temperature sensitivity) was higher in late summer compared with early spring. The variation in R Light between experimental treatments and seasons was positively correlated with carboxylation capacity and photorespiration. R Light was less responsive to short-term changes in temperature than R Dark , as shown by a lower Q 10 in R Light compared with R Dark. The overall light inhibition of R was ∼40%. Our results highlight the dynamic nature of leaf respiration to temperature variation and that the responses of R Light do not simply mirror those of R Dark. Therefore, it is important not to assume that R Light is the same as R Dark in ecosystem models, as doing so may lead to large errors in predicting plant CO 2 release and productivity.