Plants are usually thought to have little if any photosynthetic activity in high-latitude ecosystems during winter. Our results show that evergreen species, such as Vaccinium vitis-idaea, are capable of photosynthesizing under insulating snow cover. The subnivean photosynthesis compensates for respiratory CO2 losses during winter, and even net gain of carbon can be achieved. Consequently, the total concentration of non-structural carbohydrates may stay at a steady level in the overwintering leaves throughout winter.
At snowmelt photosynthesis is inhibited due to excessive levels of light and exposure to low temperatures when the protection of the snow cover is lost. Recovery of photosynthesis may take several weeks after snowmelt.
Our growth chamber experiments show that V. vitis-idaea is able to up-regulate its photosynthesis very rapidly when exposed above-zero temperatures in mid-winter. This suggests that the significance of photosynthetic activity in winter may increase along with warming winters.
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