Water, not temperature, limits global forest growth as climate warms

Chart: The growth of forest trees in temperate and boreal regions became more limited by water rather than temperature as the 20th century warmed. The more orange-red the area on the map, the more tree growth in that region became limited by water availability. The bluer the area, the less water-limited the trees became. Credit: Flurin Babst, Swiss Federal Research Institute WSL, Zurich

The growth of forest trees all over the world is becoming more water-limited as the climate warms, according to new research from an international team that includes University of Arizona scientists.

The effect is most evident in northern climates and at high altitudes where the primary limitation on tree growth had been cold temperatures, reports the team this week in the online journal Science Advances.

"Our study shows that across the vast majority of the land surface, trees are becoming more limited by water," said first author Flurin Babst, who conducted the research at the UA Laboratory of Tree-Ring Research and the Swiss Federal Research Institute WSL in Zurich.

"This is the first time that anybody has projected the tree growth responses to climate at a near-global scale," Babst said.

The researchers compared the annual growth rings of trees during two time periods, 1930–1960 and 1960–1990. The growth rings are wider when conditions are better, narrower when conditions are worse. The ring-width measurements were taken from trees at about 2,700 sites spanning every continent except Antarctica.

For those two time periods, the team also mapped […]

Full article: Water, not temperature, limits global forest growth as climate warms

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