Trees on the move: Researchers reveal how wildfire accelerates forest
changes

Date:
November 15, 2021
Source:
Stanford University
Summary:
As climate conditions change, tree species are shifting their
ranges.

Wildfire is accelerating this process, likely by reducing
competition from established species -- a finding that raises
questions about how to manage land in an era of shifting ecosystems.



FULL STORY ========================================================================== Refugees are on the move in forests across the western U.S. As climate conditions change, the ranges of tree species are shifting, especially
toward cooler or wetter sites. A new Stanford analysis provides some of
the first empirical evidence that wildfire is accelerating this process,
likely by reducing competition from established species. The study,
published Nov. 15 in Nature Communications, raises questions about how to manage land in an era of shifting ecosystems -- a key issue as President
Biden prepares to sign into law an infrastructure bill that allocates
more than $5 billion for forest restoration and wildfire risk reduction.


========================================================================== "Complex, interdependent forces are shaping the future of our forests,"
said study lead author Avery Hill, a graduate student in biology at
Stanford's School of Humanities & Sciences. "We leveraged an immense
amount of ecological data in the hopes of contributing to a growing body
of work aimed at managing these ecosystem transitions." As the climate changes, animal and plant species are shifting their ranges toward
conditions suitable for their growth and reproduction. Past research
has shown that plant ranges are shifting to higher, cooler elevations
at an average rate of almost five feet per year. In many studies, these
range shifts lag behind the rate of climate change, suggesting that some species may become stranded in unsuitable habitats. The factors that
impact plant species' ability to keep up with climate change are key to maintaining healthy populations of the dominant trees in western forests,
yet have remained largely mysterious.

To better understand the distance, direction and rate at which tree ranges
are shifting, Hill and study co-author Chris Field, the Perry L. McCarty Director of the Stanford Woods Institute for the Environment, looked at
how the phenomenon is affected by wildfire, a potent and widespread driver
of ecosystem structure and composition in the western United States.

Using U.S. Forest Service data collected from over 74,000 plots across
nine Western states, the researchers identified tree species that are
shifting their ranges toward cooler, wetter sites -- an expected response
to the recent warming and drying. Then, they compared the rate of these
range shifts between places that were burned by wildfire and places that
were not.

Of eight species that had seedlings growing in climates significantly
different from mature trees of the same species, Hill and Field found
strong evidence that two -- Douglas fir and canyon live oak -- had larger
range shifts in areas that burned than in areas that did not.

Although the analysis did not reveal the mechanism for how wildfire
accelerates range shifts for certain trees, the researchers hypothesized
that burned areas with their open canopies and scorched understory
present less competition from other plant species.

The findings demonstrate not only that fire can accelerate tree migration,
but that some species may be slowing the range shifts of others through competition. This, in turn, raises questions about the impact of fire management on trees' ability to keep up with climate change, and points
to the importance of low-intensity prescribed and natural fires.

"This study highlights a natural mechanism that can help forests remain healthy, even in the face of small amounts of climate change," said
Field. "It also illustrates the way that ecosystem processes often
have several layers of controls, a feature that emphasizes the value
of detailed understanding for effective management." Field is also
the Melvin and Joan Lane Professor for Interdisciplinary Environmental
Studies, a professor of Earth system science and biology, and a senior
fellow at the Precourt Institute for Energy.

The research was funded by the Gordon and Betty Moore Foundation.

========================================================================== Story Source: Materials provided by Stanford_University. Original written
by Rob Jordan.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Avery P. Hill, Christopher B. Field. Forest fires and
climate-induced
tree range shifts in the western US. Nature Communications, 2021;
12 (1) DOI: 10.1038/s41467-021-26838-z ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211115151021.htm

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