Tumajer et al. (2025) Longer growing seasons will not offset growth loss in drought-prone temperate forests of Central-Southeast Europe

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-10-29
• Authors: Jan Tumajer, Jakub Kašpar, Jan Altman, Nela Altmanová, J. Julio Camarero, Emil Cienciala, Vojtěch Čada, Tomáš Čihák, Jiří Doležal, Pavel Fibich, Pavel Janda, Ryszard J. Kaczka, Tomáš Kolář, Jiří Lehejček, Jiří Mašek, Radim Matula, Kateřina Neudertová Hellebrandová, Lenka Plavcová, Michal Rybníček, Miloš Rydval, Rohan Shetti, Miroslav Svoboda, Martin Šenfeldr, Pavel Šamonil, Ivana Vašíčková, Monika Vejpustková, Václav Treml
• DOI: 10.1038/s41467-025-64568-8

Research Groups

• Department of Physical Geography and Geoecology, Faculty of Science, Charles University, Prague, Czech Republic
• Department of Forest Ecology, Landscape Research Institute p.r.i., Brno, Czech Republic
• Institute of Botany of the Czech Academy of Sciences, Třeboň, Czech Republic
• Department of Forest Ecology, Czech University of Life Sciences, Prague, Czech Republic
• Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
• Instituto Pirenaico de Ecología (IPE-CSIC), Zaragoza, Spain
• IFER – Institute of Forest Ecosystem Research Ltd., Jilove u Prahy, Czech Republic
• Global Change Research Institute of the Czech Academy of Sciences, Brno, Czech Republic
• Forestry and Game Management Research Institute, Jíloviště, Czech Republic
• Faculty of Forestry and Wood Technology, Mendel University in Brno, Brno, Czech Republic
• Department of Environment, Faculty of Environment, University of Jan Evangelista Purkyně, Ústí nad Labem, Czech Republic
• The Green Concept, Institute for Carbon Assessments and Restoration Ecology, Pune, India

Short Summary

This study uses the VS-Lite growth model calibrated with 2013 tree-ring chronologies from Central-Southeast Europe to predict that while extended growing seasons may temporarily offset drought-induced growth loss until the 2040s-2050s, high-emission climate scenarios will lead to significant long-term growth reduction in drier temperate forests, as growing season extension becomes insufficient to compensate for declining summer growth rates.

Objective

• To understand how growing season extension and increasing drought stress contribute to long-term growth trends in temperate forests.
• To test if future negative impacts of increasing summer drought stress on stem growth will be partly offset by the prolongation of the growing season.
• To determine if the net balance between the positive effects of growing season extension and negative effects of summer growth decline would vary along the climatic gradient, among Shared Socioeconomic Pathway (SSP) scenarios, and during future meteorological extremes (cool-wet and warm-dry years).

Study Configuration

• Spatial Scale: Central-Southeast Europe, covering 2013 sites of 15 tree genera across latitudinal (42.4–51.8°N), longitudinal (10.6–25.5°E), and elevational gradients (153–1713 m). Climatic water balance ranges from -160 mm to +1230 mm annually.
• Temporal Scale:
  • Calibration Period: 1961–2020 (tree-ring chronologies, historical climate).
  • Forecast Periods: Four bi-decadal periods: 2020–2039, 2040–2059, 2060–2079, and 2080–2099.
  • Data Resolution: Monthly for VS-Lite model inputs and outputs.
  • Validation Data: Dendrometer data (2012–2020), Normalized Difference Vegetation Index (NDVI) (2000–2020).

Methodology and Data

• Models used: Modified VS-Lite empirical non-linear climate-driven growth model, simulating intra-annual wood formation based on monthly temperature, soil moisture, and photoperiod.
• Data sources:
  • Tree-ring data: 2013 tree-ring width chronologies from three dendrochronological datasets: TreeDataClim, CzechTerra, and RemoteForests network.
  • Dendrometer data: Automatic point (TOMST) or band dendrometers (Environmental Measuring Systems) from 57 sites in the Czech Republic.
  • Vegetation Index: Normalized Difference Vegetation Index (NDVI) time series (2000–2020) from MODIS satellite (Terra Vegetation Indices; MOD13Q1) with 250 m spatial and 16-day temporal resolution.
  • Historical Climate Data: Monthly mean air temperature and total monthly precipitation (1961–2020) from gridded products (Czech Hydrometeorological Institute, German Weather Service, E-OBS version 30) with 0.1°x0.1° spatial resolution.
  • Future Climate Projections: Mean ensemble of bi-decadal anomalies from the sixth Coupled Model Intercomparison Project (CMIP6) for four Shared Socioeconomic Pathways (SSPs): SSP1-2.6 (low-emission), SSP2-4.5 (moderate), SSP3-7.0 (high-emission), and SSP5-8.5 (high-emission), with 0.25° × 0.25° spatial resolution.

Main Results

• The VS-Lite model demonstrated good coherence with observed tree-ring width chronologies (mean Pearson's r = 0.42), dendrometer data, and NDVI series, validating its capability to approximate climatic drivers of stem growth and phenology.
• Until the 2040s–2050s, predicted annual growth increments under mean climatology were stable or slightly positive across most SSP scenarios and genera, as the extended growing season temporarily offset drought stress.
• During the second half of the 21st century, high-emission scenarios (SSP3-7.0, SSP5-8.5) led to significant growth reduction in dry sites (13% to 27% narrower tree-rings by 2080-2099 compared to baseline), while humid coniferous forests (e.g., Picea sp.) showed growth acceleration (up to 48% wider tree-rings).
• Low-emission scenarios (SSP1-2.6, SSP2-4.5) predicted annual growth rates fluctuating close to or slightly above the baseline mean.
• Cold-driven growth limitation, prevalent in the baseline period, is predicted to decline, being replaced by drought stress as the primary limiting factor.
• The mean growing season duration is forecasted to extend by 0.65 months (SSP1-2.6) to 1.44 months (SSP5-8.5) by the end of the century, primarily due to an earlier start of cambial activity.
• Intra-annual growth patterns are predicted to shift from a unimodal distribution with a single summer peak to right-skewed unimodal or bimodal patterns (two distinct peaks in spring and autumn) in dry sites under high-emission scenarios, reflecting accelerated spring/autumn growth and reduced summer growth rates.
• Extreme warm-dry years are projected to cause severe growth loss at dry sites (41% to 70% narrower tree-rings by 2080-2099 compared to baseline mean), with an earlier cessation of the growing season due to amplified drought.

Contributions

• Provides a comprehensive regional assessment of the trade-off between growing season extension and summer drought stress on temperate forest growth in Central, Eastern, and Southeastern Europe.
• Forecasts intra-annual wood formation and overall growth trends for 15 tree genera under four SSP climate scenarios through the 21st century, identifying a critical tipping point in the 2040s–2050s.
• Demonstrates that while extended growing seasons can initially offset drought impacts, this compensation becomes insufficient in drier sites under high-emission scenarios, leading to significant growth reductions.
• Highlights the crucial role of adjusting intra-annual wood formation to seasonal moisture availability for tree survival in warmer climates.
• Emphasizes that only low-emission scenarios support non-declining stem growth in dry forests with current species composition, informing climate change adaptation strategies for forestry.
• Utilizes a large dataset of 2013 tree-ring chronologies and independently validates the VS-Lite model's intra-annual growth simulations with dendrometer data and NDVI.

Funding

• Czech Science Foundation [24-11757S, 23-07583S]
• Charles University [PRIMUS/24/SCI/004]
• Program Johannes Amos Comenius P JAC [CZ.02.01.01/00/22_008/0004605]
• Ministry of Agriculture of the Czech Republic [QL24020351]

Citation

@article{Tumajer2025Longer,
  author = {Tumajer, Jan and Kašpar, Jakub and Altman, Jan and Altmanová, Nela and Camarero, J. Julio and Cienciala, Emil and Čada, Vojtěch and Čihák, Tomáš and Doležal, Jiří and Fibich, Pavel and Janda, Pavel and Kaczka, Ryszard J. and Kolář, Tomáš and Lehejček, Jiří and Mašek, Jiří and Matula, Radim and Hellebrandová, Kateřina Neudertová and Plavcová, Lenka and Rybníček, Michal and Rydval, Miloš and Shetti, Rohan and Svoboda, Miroslav and Šenfeldr, Martin and Šamonil, Pavel and Vašíčková, Ivana and Vejpustková, Monika and Treml, Václav},
  title = {Longer growing seasons will not offset growth loss in drought-prone temperate forests of Central-Southeast Europe},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-64568-8},
  url = {https://doi.org/10.1038/s41467-025-64568-8}
}