10 May 2021

10 May 2021

Review status: a revised version of this preprint is currently under review for the journal BG.

A new mechanistic understanding of ecophysiological patterns in a widespread alpine dwarf shrub – Refining climate-growth relationships

Svenja Dobbert1, Roland Pape2, and Jörg Löffler1 Svenja Dobbert et al.
  • 1Department of Geography, University of Bonn, Meckenheimer Allee 166, D -53115 Bonn, Germany
  • 2Department of Natural Sciences and Environmental Health, University of South-Eastern Norway, Gullbringvegen 36, N3800 Bø, Norway

Abstract. Considering the recent widespread greening associated with dwarf shrubs in arctic and alpine ecosystems, further understanding of how these shrubs respond to environmental conditions is of crucial importance. Here we present novel insights and propose a new method to monitor shrub growth, using high-precision point dendrometers.

We analyzed intra- and inter-annual growth patterns of a common evergreen species (Empetrum nigrum ssp. hermaphroditum) by measuring its hourly radial stem variability at a micrometer scale over four successive years on exposed ridge positions and along a steep elevational gradient. With the same temporal resolution, we collected near-ground micro-environmental data and identified environmental drivers controlling growth behaviour.

Overall, we found high inter-plant variability in growth-defining parameters, but high similarities in growth responses to the micro-environment. Early-season radial growth in spring exhibited high sensitivity to winter thermal conditions and prolonged ground-freezing in spring, suggesting that the evergreen species E. hermaphroditum remains photosynthetically active during the snow-free period, which increases carbohydrate accumulation for early season physiological activities. We discovered a phase of radial stem shrinkage during the winter months, which can be attributed to an active cell water reduction to protect the plant from frost damage.

We present the first fine-scale intra-annual growth curves for an alpine dwarf shrub and identify soil moisture availability and winter freezing conditions as the main drivers of radial stem variability, thus forwarding the ongoing debate on the functional mechanisms of greening and browning in arctic and alpine regions.

Svenja Dobbert et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-99', Anonymous Referee #1, 18 May 2021
    • AC1: 'Reply on RC1', Jörg Löffler, 27 May 2021
      • RC2: 'Reply on AC1', Anonymous Referee #1, 30 May 2021
        • AC2: 'Reply on RC2', Jörg Löffler, 07 Jun 2021
  • RC3: 'Comment on bg-2021-99', Anonymous Referee #2, 18 Jun 2021
    • AC3: 'Reply on RC3', Jörg Löffler, 23 Jun 2021
  • RC4: 'Comment on bg-2021-99', Anonymous Referee #3, 27 Jul 2021
    • AC4: 'Reply on RC4', Jörg Löffler, 06 Aug 2021

Svenja Dobbert et al.

Svenja Dobbert et al.


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Short summary
Understanding how vegetation might respond to climate change is especially important in arctic-alpine ecosystems, where major shifts in shrub growth have been observed. We studied how such changes come to pass and how future changes might look like by measuring hourly variations in stem diameter of dwarf shrubs from one common species. From this data, we are able to discern information about growth mechanisms and can thus show the complexity of shrub growth/microenvironment relations.