Climate change triggered synchronous woody plants recruitment in the last two centuries in the treeline ecotone of the Northern Hemisphere

• Published in: The Science of the total environment Vol. 921; p. 170953
• Main Authors: Cannone, N., Malfasi, F.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.04.2024
• Subjects: 1980 regime shift; Air temperature; Climate change; CO2 fertilization; Forest-tundra ecotone; Tree and shrub recruitment; Tree and shrub recruitment; Forest-tundra ecotone; Climate change; 1980 regime shift; Air temperature; CO2 fertilization; CO fertilization
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.170953

Climate change triggers several ecosystem responses, including woody plant encroachment. We analyse woody plant recruitment across the treeline ecotone (the forest-tundra ecotone) of the Northern Hemisphere (NH) over an extended period (1801–2010) and its relation with atmospheric CO2 and air temperature. We detected a synchronous trend of woody plant recruitment across the NH, indicating a major climatic and environmental change, triggered by a combination of CO2 fertilization and air temperature changes. The drivers of woody plant recruitment changed with time: CO2 fertilization was the main driver in the period 1801–1950, while air temperature was the main driver after 1950, despite the drastic acceleration of CO2 increase in the last decades. These data support the hypothesis that we are shifting from a fertilization-dominated to a warming-dominated period. The temporal patterns of woody plant recruitment are consistent with the occurrence of the 1980 regime shift, a major change occurred in the Earth's biophysical systems. Indeed, the recruitment drop promoted by the 1960s–1980s air cooling, was followed by an intensive recruitment increase triggered by the restart of air warming in the last decades. The largest sensitivity and fastest resilience of evergreen and Pinaceae to the restart of air warming allows to hypothesize that, among the woody plant functional and taxonomic groups, they could perform the largest expansion also in future decades. [Display omitted] •Woody plant recruitment shows a major change in the Earth's biophysical systems.•We detected a synchronous recruitment trend since 1801 in the Northern Hemisphere.•Atmospheric CO2 and air temperature are the main drivers of woody plant recruitment.•After 1950 air temperature became the main driver overcoming CO2 fertilization.•Evergreen and Pinaceae are the woody plants most sensitive to climate change.