Large Trees Are the First to Perish.

PositionDROUGHT

In forests worldwide, research shows that drought consistently has had a more-detrimental impact on the growth and survival of larger trees. In addition, while the death of small trees may affect the dominance of trees in a landscape, the death of large trees has a far worse impact on the ecosystem and climate's health, especially due to the important role that trees play in the carbon cycle.

In a study published in Nature Plants, a team of researchers studied forests worldwide, ranging from semi-arid woodlands to tropical rainforests, to determine how a tree's size impacts its response to drought. The team included researchers from Los Alamos (N.M.) National Laboratory, the Smithsonian's Conservation Biology Institute and Tropical Research Institute, the University of New Mexico, and the U.S. Geological Survey.

Whereas previous studies documented processes at a single site, this team analyzed data from 40 drought events at 38 forest locations, systematically reviewing forests' size-death correlation worldwide.

Living trees soak up greenhouse gas and store it for a long time in their woody tissues, but dying trees release it--a carbon sink becomes a carbon source. Moreover, larger trees transpire, or release, more water into the atmosphere, cooling the land and supporting cloud formation, which affects how much solar radiation is reflected back to space and impacts precipitation.

They also play key roles in biodiversity, creating environments on which many plant and animal species are dependent, explains coauthor Nate McDowell, forest...

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