Leaf temperatures in glasshouses and open‐top chambers

Abstract

Summary• Climate manipulation experiments are of key importance in identifying possible responses of plant communities and ecosystems to climate change. Experiments for warming the air under sunlit conditions are carried out in (partial) enclosures. These inevitably alter the energy balance inside, potentially altering tissue temperatures which affect metabolism and growth.• Using an empirically validated energy balance model, we investigate effects of two widely used warming methods, climate-controlled glasshouses and passively warmed open-top chambers (OTCs), on leaf temperatures. The model applies standard energy balance formulas, supplemented with data on optical properties of glasshouse materials and wind conditions inside OTCs.• Results show that the different radiation environment inside glasshouses did not produce large leaf temperature deviations compared with outside. Poor glasshouse design with significant radiation blockage by the structure or with insufficient ventilation did affect tissue temperatures more significantly. The drastic wind speed reduction inside OTCs approximately doubled the actual (canopy) warming compared with earlier reported increases in air temperature provided by this technique -an effect that was inflated if the plants' stomates closed.• These results demonstrate that leaf temperatures were higher than previously considered in OTCs but not in climate-controlled glasshouses.

Experimental warming differentially affects microbial structure and activity in two contrasted moisture sites in a Sphagnum-dominated peatland

“…The question is therefore whether this effect was due to an experimental artefact or whether it results from a thermodynamic constraint. It was demonstrated that OTCs can stop wind blowing, thus reducing evaporation (de Boeck et al, 2012). As no relationship was found between wind speed and peat moisture (at 5 cm depth) in the control plots (data not shown), we assume that no significant reduction of evaporation by OTCs occurred at 5 cm depth.…”

Simulated heat waves affected alpine grassland only in combination with drought

“…This also highlights the notion that air temperatures can be misleading (Körner, ; Scherrer & Körner, ; De Boeck et al ., ) and that actual tissue temperatures should be used to judge whether excessive heat occurs in plants. Tissue temperatures also explain why the imposed heat wave did not alleviate any growth limitation by cool temperatures.…”

Review: critical appraisal of methods to investigate the effect of temperature on grapevine berry composition

“…Most of these experiments were conducted with potted plants or artificial soils constraining the duration to one growing season. Main artefacts associated to the experimental design (Poorter et al 2012b) include: (i) insufficient replication or independency between experimental units (Mori et al 2005a, 2007) that compromise reproducibility and statistical power; (ii) artefacts from controlled environments, such us lack of wind and its biological implications (de Langre 2008), for example, reduced thigmomorphogenic effect (Jones 1992), evaporative demand and convective heat loss from the berry (Smart and Sinclair 1976); (iii) abrupt changes on cycles of temperature and light or extreme temperatures, such as 40/20°C (day/night) during 8 to 12 days (Sepúlveda and Kliewer 1986); (iv) altered radiation (intensity and composition); (v) enrichment of CO2 concentration and its consequences, for instance, on stomata conductance; and (vi) altered tissue temperature, which affects plant growth and metabolism (De Boeck et al 2012a). Some limitations from these approaches have been emphasised (Tarara et al 2000); these include: (i) difficulties to scale up results from plant or lower level of organisation to the crop level , Koshita et al 2007, Azuma et al 2012, or from hours of treatments to complete seasons ); and (ii) unrealistic growing conditions that do not match current and projected warming or do not reproduce daily and seasonal cycles of temperature, CO 2, VPD and light (Buttrose et al 1971, Buttrose and Hale 1973.…”