Climatic change only stimulated growth for trees under weak competition in central boreal forests
Global change ecologists have often used trees under weak competition (e.g. dominant/codominant trees) to examine relationships between climatic change and tree growth. Scaling up these results to a forest relies on the assumption that the climatic change–tree growth relationship is not affected by...
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| Published in: | The Journal of ecology Vol. 108; no. 1; pp. 36 - 46 |
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| Main Authors: | , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Oxford
Blackwell Publishing Ltd
01-01-2020
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Global change ecologists have often used trees under weak competition (e.g. dominant/codominant trees) to examine relationships between climatic change and tree growth. Scaling up these results to a forest relies on the assumption that the climatic change–tree growth relationship is not affected by tree‐level competition.
Using permanent sample plot data from the central Canadian boreal region where warming did not result in water deficit, we tested the above‐mentioned assumption by looking at whether the relationship between climatic change and tree growth varied with tree‐level competition, which was quantified using a modified Hegyi competition index.
We found that tree growth increased over time for trees under weak competition, but decreased for those under strong competition. The divergent temporal trends among trees under different levels of competition led to a non‐significant change in growth for our study plots. Growth increased with regional warming, atmospheric [CO2] and water availability for trees under weak competition, but not for those under strong competition.
Synthesis. Our results suggest that upscaling the growth responses of dominant/codominant trees to climate change to a forest or a region can lead to biased estimates. Tree‐level competition should be taken into account when expressing climatic change and tree growth relationships.
Foreign Language Résumé
Le domaine de recherche qui a attrait aux changement globaux des écosystèmes forestiers a principalement étudié les individus qui n'ont pas subi un haut niveau de compétition pour tirer leurs conclusions sur l'effet des changements climatiques sur la croissance des arbres. Ce phénomène suppose que la compétition entre individus n'affecte pas les interactions entre les changements globaux et la croissance des arbres ou des écosystèmes forestiers.
Nos analyses de placettes échantillon permanentes (placettes re‐mesurées) de la région boréale centrale du Canada, où les changements globaux n'ont pas entraîné de déficit en eau, nous on permit de vérifier si, en effet, le niveau de compétition subi par les individus affecte les interactions entre les changements globaux et la croissance des arbres. Un indice de compétition modifié de Hegyi nous a permis de quantifier le niveau de compétition.
Nos analyses montrent que les individus sous faible compétition croient plus rapidement sous les changements globaux (concentration de CO2 et températures élevées, sans déficit d'eau) que ceux sous un niveau plus élevé de compétition; ces derniers montrent une diminution de croissance. Au niveau de la placette, ces effets s'annulent.
Synthèse. Nos résultats suggèrent que le niveau de compétition des individus doit être pris en considération pour tirer des conclusions non‐biaisées sur l'effet des changements globaux sur la croissance des arbres, tant bien au niveau des individus, des placettes échantillons, des forêts et des régions.
In an area where regional warming did not result in water deficit, tree growth increased over time for trees under weak competition, but decreased for those under strong competition, leading to a non‐significant growth change at the plot level. This study suggests that upscaling the climate change‐associated growth of dominant/codominant trees to a forest can lead to biased estimates |
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| ISSN: | 0022-0477 1365-2745 |
| DOI: | 10.1111/1365-2745.13228 |