Norway spruce shows stronger growth sensitivity and weaker intrinsic water-use efficiency response than Scots pine under increasing water limitation in southern Finland
- 1Natural Resources Institute Finland (Helsinki, Finland)
Abstract
Boreal forests, essential for carbon sequestration and multiple ecosystem services, are increasingly threatened by climate-induced water stress. This study investigates how increasing water limitation affects growth and intrinsic water-use efficiency ( i WUE ) in Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies (L.) Karst) in southern Finland from 1990 to 2022. Tree-ring data on basal area increment (BAI) and carbon isotope discrimination (Δ ¹³ C) were collected from three sites per species, with Scots pine on mineral soils and Norway spruce on organic soils and under contrasting soil moisture conditions. The tree-ring records were combined with regional growth indices (GIs) from the Finnish National Forest Inventory (NFI) to enable broader inference across soil types. Our results indicate that water limitation intensified over the past decade, with pronounced growth declines after 2016 in Norway spruce, while Scots pine exhibited smaller reductions, evident at the site level from around 2009 but not resolved in the regional GI. Δ ¹³ C analyses indicated increased stomatal regulation in Scots pine and more limited physiological adjustment in Norway spruce after 2016, consistent with rising atmospheric moisture demand. Accordingly, i WUE increased more strongly in Scots pine, whereas Norway spruce showed only modest changes despite a substantial growth decline. Interannual variability in growth and i WUE was related both to vapour pressure deficit (VPD) and to the summer water balance, but their relative importance differed between species: VPD had the larger effect per standard deviation in Scots pine, whereas Norway spruce responded to atmospheric demand and to the summer water balance to a similar degree. In Norway spruce, growth after 2016 was significantly constrained by VPD, whereas Scots pine showed comparatively buffered growth responses and stronger increases in i WUE . Soil-type effects were generally weak at the regional scale, but clearer patterns emerged along local moisture conditions. At the site level, both species tended to show greater negative post-change growth under drier conditions; however, Scots pine maintained higher mean growth on wetter sites, whereas Norway spruce showed higher mean growth under drier conditions. These contrasting growth–physiology responses indicate species-specific strategies in coping with increasing water limitation, with Norway spruce showing greater growth sensitivity and more limited physiological adjustment than Scots pine. Overall, boreal forest responses to drought appear to be structured primarily by species-specific physiological strategies, while being further modulated by local hydrological conditions. Accounting for both species differences and fine-scale variation in moisture availability will be critical for sustaining forest productivity and resilience under increasingly warm and water-limited climates in northern Europe, underscoring the need for site-adapted management that integrates species selection with local soil and moisture conditions.
Versions
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BibTeX
@article{szejner2026norway,
title = {{Norway spruce shows stronger growth sensitivity and weaker intrinsic water-use efficiency response than Scots pine under increasing water limitation in southern Finland}},
author = {Paul Szejner and Eduardo Martínez-García and Helena Haakana and Juha Heikkinen and Katja T. Rinne-Garmston and Petri Kilpeläinen and Giles Young and Elina Sahlstedt and Raisa Mäkipää and Aleksi Lehtonen},
journal = {Biogeosciences},
year = {2026},
month = oct,
doi = {10.5194/bg-23-7223-2026},
url = {https://bg.copernicus.org/articles/23/7223/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Norway spruce shows stronger growth sensitivity and weaker intrinsic water-use efficiency response than Scots pine under increasing water limitation in southern Finland
AU - Paul Szejner
AU - Eduardo Martínez-García
AU - Helena Haakana
AU - Juha Heikkinen
AU - Katja T. Rinne-Garmston
AU - Petri Kilpeläinen
AU - Giles Young
AU - Elina Sahlstedt
AU - Raisa Mäkipää
AU - Aleksi Lehtonen
PY - 2026
DA - 2026/10/15
JO - Biogeosciences
DO - 10.5194/bg-23-7223-2026
UR - https://bg.copernicus.org/articles/23/7223/2026/
AB - Boreal forests, essential for carbon sequestration and multiple ecosystem services, are increasingly threatened by climate-induced water stress. This study investigates how increasing water limitation affects growth and intrinsic water-use efficiency ( i WUE ) in Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies (L.) Karst) in southern Finland from 1990 to 2022. Tree-ring data on basal area increment (BAI) and carbon isotope discrimination (Δ ¹³ C) were collected from three sites per species, with Scots pine on mineral soils and Norway spruce on organic soils and under contrasting soil moisture conditions. The tree-ring records were combined with regional growth indices (GIs) from the Finnish National Forest Inventory (NFI) to enable broader inference across soil types. Our results indicate that water limitation intensified over the past decade, with pronounced growth declines after 2016 in Norway spruce, while Scots pine exhibited smaller reductions, evident at the site level from around 2009 but not resolved in the regional GI. Δ ¹³ C analyses indicated increased stomatal regulation in Scots pine and more limited physiological adjustment in Norway spruce after 2016, consistent with rising atmospheric moisture demand. Accordingly, i WUE increased more strongly in Scots pine, whereas Norway spruce showed only modest changes despite a substantial growth decline. Interannual variability in growth and i WUE was related both to vapour pressure deficit (VPD) and to the summer water balance, but their relative importance differed between species: VPD had the larger effect per standard deviation in Scots pine, whereas Norway spruce responded to atmospheric demand and to the summer water balance to a similar degree. In Norway spruce, growth after 2016 was significantly constrained by VPD, whereas Scots pine showed comparatively buffered growth responses and stronger increases in i WUE . Soil-type effects were generally weak at the regional scale, but clearer patterns emerged along local moisture conditions. At the site level, both species tended to show greater negative post-change growth under drier conditions; however, Scots pine maintained higher mean growth on wetter sites, whereas Norway spruce showed higher mean growth under drier conditions. These contrasting growth–physiology responses indicate species-specific strategies in coping with increasing water limitation, with Norway spruce showing greater growth sensitivity and more limited physiological adjustment than Scots pine. Overall, boreal forest responses to drought appear to be structured primarily by species-specific physiological strategies, while being further modulated by local hydrological conditions. Accounting for both species differences and fine-scale variation in moisture availability will be critical for sustaining forest productivity and resilience under increasingly warm and water-limited climates in northern Europe, underscoring the need for site-adapted management that integrates species selection with local soil and moisture conditions.
SN - 1726-4189
ER -