Recent spruce (Picea abies) treeline ecotonal progression since the late1980s in the Swedish Scandes-a repeat photographic narration and analysis

Leif Kullman Leif Kullman

doi:10.30574/ijsra.2021.4.1.0189

Abstract

This study reports a case of climate-mediated transformation and physiognomic progression of the Norway spruce (Picea abies) treeline ecotone since the mid-1990s in the Swedish Scandes. The methods include repeat photography and foliation estimates of old-established clonal spruces. An air and soil temperature nadir by the 1980s had caused extensive needle and shoot mortality, evident at the landscape-scale. Subsequent winter and summer temperature rises induced a striking canopy recovery, including densification and vertical growth. Release from low soil temperature stress appears as instrumental for canopy progression and shift from stunted growth to erect tree forms. Seed-based regeneration of new individuals has been virtually nil and the ecotone appears to be spatially stable. Ongoing ecotonal shifts has the character of growth form transformations in accordance with climatic conjunctures.

Highlights

The performance of alpine treeline ecotones are generally held as sentinels of climate change and associated ecological landscape transformation [75, 35, 38, 66, 67, 63, 11, 22, 72, 20, 16, 24, 19, 1, 13]
Given the fact that high-elevation tree species zonation patterns have shifted during the Holocene [40], it may be relevant to look at the current status and responses of species, confined to elevations well below the treeline of the species currently forming highest ascending treeline
This paper focuses on Norway spruce

Summary

Introduction

The performance of alpine treeline ecotones are generally held as sentinels of climate change (summer and winter) and associated ecological landscape transformation [75, 35, 38, 66, 67, 63, 11, 22, 72, 20, 16, 24, 19, 1, 13].Observational data have evidenced that responses to altered climatic conditions vary locally in extent and character in consequence of topography, soils and associated factors as well as shifting land use histories. Species specific idiosyncrasies influence response patterns [53, 6, 58]. Climatic treeline effect studies have focused on the species that currently displays the uppermost arboreal representation towards the alpine tundra. Given the fact that high-elevation tree species zonation patterns have shifted during the Holocene [40], it may be relevant to look at the current status and responses of species, confined to elevations well below the treeline of the species currently forming highest ascending treeline. Karst.), forming the second highest treeline in much of the Swedish Scandes. It penetrates with scattered individuals into the lower part of the subalpine birch forest belt

Methods

Results

Conclusion