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Dryad

Alpine and Arctic tundra shrub populations show similar ontogenetic growth trends but differing absolute growth rates and lifespan

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Aug 09, 2024 version files 40.93 KB

Abstract

The majority of terrestrial primary production is performed by plants, the ontogenetic growth trends of which greatly influence biomass and carbon dynamics. Here, we study ontogenetic trends of primary (apical) and secondary (stem thickening) growth in Arctic (Svalbard, Norway) and alpine (Krkonoše, Czechia) populations of black crowberry (Empetrum nigrum), the dominant plant species of certain tundra communities. The environmental conditions in alpine areas are more favourable for plant growth than those in the High Arctic, where temperatures are lower, there is less precipitation and soils are shallower, among other differences. These differences were reflected in significant differences in absolute growth rates and shrub age between the populations under study. However, we found almost no differences in ontogenetic growth trends between the populations. In both populations, primary growth and secondary (stem base) growth decrease throughout ontogeny whereas secondary (stem top) growth and basal area increment increase. No significant differences in the slope of the trends were found in either primary or secondary (stem base) growth. Trends in the ratio between basal area increment and primary growth revealed neither absolute nor relative differences between the populations. Ontogenetic trends in the shrubs analysed were surprisingly stable despite the prominently different environmental conditions. Empetrum plants have adapted to the different environments by altering their absolute growth rate only. This adaptation has probably also resulted in the different longevity of plants constituting the study populations, confirming the theory that slower-growing plants live longer. Primary growth and secondary (diameter) growth at the stem base seem to be more basic characteristics of plant growth compared to basal area increment and secondary (diameter) growth at the apex because the latter two seem to be dependent on the absolute growth rate.