Abstract
Climate change is stronger at high than at temperate and tropical latitudes. The natural geothermal conditions in southern Iceland provide an opportunity to study the impact of warming on plants, because of the geothermal bedrock channels that induce stable gradients of soil temperature. We studied two valleys, one where such gradients have been present for centuries (long-term treatment), and another where new gradients were created in 2008 after a shallow crustal earthquake (short-term treatment). We studied the impact of soil warming (0 to +15 °C) on the foliar metabolomes of two common plant species of high northern latitudes: Agrostis capillaris, a monocotyledon grass; and Ranunculus acris, a dicotyledonous herb, and evaluated the dependence of shifts in their metabolomes on the length of the warming treatment. The two species responded differently to warming, depending on the length of exposure. The grass metabolome clearly shifted at the site of long-term warming, but the herb metabolome did not. The main up-regulated compounds at the highest temperatures at the long-term site were saccharides and amino acids, both involved in heat-shock metabolic pathways. Moreover, some secondary metabolites, such as phenolic acids and terpenes, associated with a wide array of stresses, were also up-regulated. Most current climatic models predict an increase in annual average temperature between 2–8 °C over land masses in the Arctic towards the end of this century. The metabolomes of A. capillaris and R. acris shifted abruptly and nonlinearly to soil warming >5 °C above the control temperature for the coming decades. These results thus suggest that a slight warming increase may not imply substantial changes in plant function, but if the temperature rises more than 5 °C, warming may end up triggering metabolic pathways associated with heat stress in some plant species currently dominant in this region.
Highlights
The global mean surface temperature at the end of the century (2081–2100) is likely to increase between 2.6 and 4.8 ◦ C, and even more towards the poles (2–8 ◦ C) [1]
We investigated the effects of short- and long-term warming on the foliar metabolomes of the grass Agrostis capillaris and the herbaceous dicotyledon Ranunculus acris
These results strongly suggest that metabolism is much more conservative and homeostatic for R. acris than A. capillaris, consistent with the higher metabolomic homeostasis and lower flexibility to environmental changes in herbaceous than grass species previously reported in other ecometabolomic studies [63,64]
Summary
The global mean surface temperature at the end of the century (2081–2100) is likely to increase between 2.6 and 4.8 ◦ C, and even more towards the poles (2–8 ◦ C) [1]. The species resistant to stress usually have low phenotypical plasticity [7] This low phenotypical plasticity can even be a great constrain, because the capacity of organisms to increase their activity due to global warming could be limited by several variables, such as water and nutrient availabilities [10,11,12]. This is especially relevant in sub-arctic ecosystems, where warming largely impacts on soil nutrient availability, plant production, and reproduction [13,14,15,16]
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