Abstract
Current understanding of the effects of extreme temperature on alpine evergreens is very limited for ecosystems under Mediterranean climate (characterised by a drought period in summer), despite being exceptionally biodiverse systems and highly vulnerable under a global change scenario. We thus assessed (i) seasonal change and (ii) effect of ontogeny (young vs. mature leaves) on thermal sensitivity of Erysimum scoparium, a keystone evergreen of Teide mountain (Canary Islands). Mature leaves were comparatively much more vulnerable to moderately high leaf-temperature (≥+40 and <+50 °C) than other alpine species. Lowest LT50 occurred in autumn (−9.0 ± 1.6 °C as estimated with Rfd, and −12.9 ± 1.5 °C with Fv/Fm). Remarkably, young leaves showed stronger freezing tolerance than mature leaves in spring (LT50 −10.3 ± 2.1 °C vs. −5.6 ± 0.9 °C in mature leaves, as estimated with Rfd). Our data support the use of Rfd as a sensitive parameter to diagnose temperature-related damage in the leaves of mountain plants. On a global change scenario, E. scoparium appears as a well-prepared species for late-frost events, however rather vulnerable to moderately high temperatures.
Highlights
High mountain ecosystems are strongly determined by abiotic factors of the environment such as strong irradiance, wind, and extreme temperatures [1]
The LT10 and LT50 values derived from the data shown in Figure 1 were higher for Rfd than for Fv/Fm (Table 1)
This led to important differences in the LT50, outstanding when estimated from Rfd: LT50 was −5.6 ± 0.9 ◦C in the mature, and −10.3 ± 2.1 ◦C in the young leaves (Table 1)
Summary
High mountain ecosystems are strongly determined by abiotic factors of the environment such as strong irradiance, wind, and extreme temperatures [1]. Despite the overall trend towards decreasing air temperatures with elevation, plant leaves can be exposed to extreme high temperatures in alpine environments too [1,8]. Tolerance to extreme temperature varies along the year due to processes of acclimation/deacclimation (or hardening/dehardening) [9,10,11,12,13]. This fact is becoming of crucial relevance in the current context of global warming, since the spring phenology is advancing (due to overall temperature rise) faster than the date of the last spring frost
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