Understory functional groups and fire history but not experimental warming drive tree seedling performance in unmanaged boreal forests

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  • Maria Theresa Jessen
  • Eveline J. Krab
  • Lett, Signe
  • Marie-Charlotte Nilsson
  • Laurenz Teuber
  • David A. Wardle
  • Ellen Dorrepaal

Introduction: Survival and growth of tree seedlings are key processes of regeneration in forest ecosystems. However, little is known about how climate warming modulates seedling performance either directly or in interaction with understory vegetation and post-fire successional stages. Methods: We measured survival (over 3 years) and growth of seedlings of three tree species (Betula pubescens, Pinus sylvestris, and Picea abies) in a full-factorial field experiment with passive warming and removal of two plant functional groups (feather moss and/or ericaceous shrubs) along a post-fire chronosequence in an unmanaged boreal forest. Results: Warming had no effect on seedling survival over time or on relative biomass growth. Meanwhile, moss removal greatly increased seedling survival overall, while shrub removal canceled this effect for B. pubescens seedlings. In addition, B. pubescens and P. sylvestris survival benefitted most from moss removal in old forests (>260 years since last fire disturbance). In contrast to survival, seedling growth was promoted by shrub removal for two out of three species, i.e., P. sylvestris and P. abies, meaning that seedling survival and growth are governed by different understory functional groups affecting seedling performance through different mechanism and modes of action. Discussion: Our findings highlight that understory vegetation and to a lesser extent post-fire successional stage are important drivers of seedling performance while the direct effect of climate warming is not. This suggests that tree regeneration in future forests may be more responsive to changes in understory vegetation or fire regime, e.g., indirectly caused by warming, than to direct or interactive effects of rising temperatures.

OriginalsprogEngelsk
Artikelnummer1130532
TidsskriftFrontiers in Forests and Global Change
Vol/bind6
Antal sider10
ISSN2624-893X
DOI
StatusUdgivet - 2023

Bibliografisk note

Funding Information:
This study was funded by Kempe Foundation (JCK-1112), Swedish Research Council VR (Dnr 621-2011-5444), and Knut and Alice Wallenberg Foundation (Wallenberg Academy Fellowship KAW 2012.0152) to ED.

Funding Information:
We thank Katharina Krumpholz, Johannes Moeser, and Luise Pabst for valuable help in the field and lab and Adam Clark for helpful discussions on the statistics. We also thank the Swedish Polar Research Secretariat and SITES for support, accommodation and laboratory facilities at Abisko Scientific Research Station.

Publisher Copyright:
Copyright © 2023 Jessen, Krab, Lett, Nilsson, Teuber, Wardle and Dorrepaal.

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