Drought tolerance of emerging European silver fir seedlings (Abies alba Mill.) does not follow geographic gradients

Abstract

One of silviculture's primary objectives is converting monospecific into diverse forest stands comprising climate-tolerant species, aiming to mitigate global change. In practice, this is often achieved by enrichment planting or seeding of species, currently not occurring in the specific area. Silver fir ( Abies alba ) is considered one of the European native species regarded as climate tolerant. The species, therefore recently received increasing attention in research and forestry in the context of climate change adaptation. The intra-specific variation in drought tolerance has been intensively studied in Abies alba adult trees, but not in seedlings. Here, we explore the potential of Abies alba seedlings to withstand simulated summer droughts in central Europe. A climate chamber experiment was conducted, examining the resistance to and recovery from drought of silver fir seedlings of four provenances representing a geographic West–East gradient in Europe. Seedlings were exposed to two 30-day drought scenarios of differing severity under controlled conditions. We measured biomass partitioning patterns and individual photosynthetic efficiency. Growth and maximum photosynthetic efficiency were unaffected by intermediate drought. Intense drought significantly reduced the maximum photosynthetic efficiency of all provenances. Seedlings of the easternmost provenance showed the greatest biomass across all treatments; however, they failed to recover from drought. Our findings show that differences in drought susceptibility of emerging Abies alba seedlings do not follow geographic gradients.

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