The findings, reported today in the journal Nature, come from the Global Forest Biodiversity Initiative (GFBI), a consortium of forest scientists and practitioners of which the FACAI Lab is a key hub and global center. Jingjing Liang,
a Purdue University assistant professor of quantitative forest ecology,
is co-supervisor the FACAI Lab, coordinator and cofounder of the GFBI
and co-lead author of the paper. Mo Zhou,
a Purdue assistant professor of forest economics and management, is a
senior author of the paper, co-supervisor of the FACAI lab and lead
economist of the GFBI.
Purdue’s FACAI lab employs artificial intelligence and machine
learning to study global, regional and local forest resource management
and biodiversity conservation. For this research, FACAI compiled species
abundance data from 55 million tree records in 1.2 million forest
sample plots spanning 110 countries. The organization of the data was
integral to developing the global map.
“The map and underlying global forest inventory database will serve
as the foundation for research on the environmental impacts of forest
changes, biological conservation and forest management, “Liang said.
The map identifies the types of mycorrhizal fungi associated with
trees in a particular forest. These fungi attach to tree roots,
extending a tree’s ability to reach water and nutrients while the tree
provides carbon necessary for the fungi’s survival. The two most common
types of mycorrhizae are arbuscular, which grow inside the tissues of
tree roots and are associated with tree species such as maple, ash and
yellow poplar, and ectomycorrhizal, which live on the outside of roots
and are associated with tree species such as pine, oak, hickory and
Those associations are important because the mycorrhizae affects the
trees’ ability to access nutrients, sequester carbon and withstand the
effects of climate change.
“Managing forests for climate change mitigation and sustainable
development, therefore, should go well beyond managing only trees,” Zhou
The authors found that climate is the most significant factor
affecting the distribution of mycorrhizae. A warming climate is reducing
the abundance of ectomycorrhizal tree species by as much as 10 percent.
That change is altering forests’ ecological and economic footprints,
especially along the boreal-temperate ecotone, the border areas between
colder and warmer forest. Losses to ectomycorrhizal species have
implications for climate change since these fungi increase the amount of
carbon stored in soil.
“Knowing the species composition in the forested area across the
world is an important start,” Liang said. “There are many fundamental
and socioeconomic questions we can answer now with GFBI data and
cutting-edge machine learning techniques.”
The FACAI lab is currently developing collaborations to explore
questions about ecology and economics, including self-learning forest
models, innovative approaches to biodiversity valuation, locating
unknown forest resources and space exploration.
The work aligns with Purdue’s Giant Leaps celebration,
acknowledging the university’s global advancements made in health,
space, artificial intelligence and sustainability as part of Purdue’s
150th anniversary. Those are the four themes of the yearlong
celebration’s Ideas Festival, designed to showcase Purdue as an intellectual center solving real-world issues.
Brian S. Steidinger, a postdoctoral research fellow at Stanford University, and Thomas Ward Crowther, an assistant professor at ETH Zurich, are co-lead authors of the Nature paper with Liang. Sergio de Miguel,
an assistant profession and principal investigator of the GFBI Hub at
University of Lleida, Spain, and Xiuhai Zhao and Chunyu Zhang,
professors at Beijing Forestry University, are among the senior
collaborators of this paper.
Climatic controls of decomposition drive the global biogeography of forest-tree symbioses
The identity of the dominant root-associated microbial symbionts in a
forest determines the ability of trees to access limiting nutrients
from atmospheric or soil pools, sequester carbon and withstand the
effects of climate change. Characterizing the global distribution of
these symbioses and identifying the factors that control this
distribution are thus integral to understanding the present and future
functioning of forest ecosystems. Here we generate a spatially explicit
global map of the symbiotic status of forests, using a database of over
1.1 million forest inventory plots that collectively contain over 28,000
tree species. Our analyses indicate that climate variables—in
particular, climatically controlled variation in the rate of
decomposition—are the primary drivers of the global distribution of
major symbioses. We estimate that ectomycorrhizal trees, which represent
only 2% of all plant species, constitute approximately 60% of tree
stems on Earth. Ectomycorrhizal symbiosis dominates forests in which
seasonally cold and dry climates inhibit decomposition, and is the
predominant form of symbiosis at high latitudes and elevation. By
contrast, arbuscular mycorrhizal trees dominate in aseasonal, warm
tropical forests, and occur with ectomycorrhizal trees in temperate
biomes in which seasonally warm-and-wet climates enhance decomposition.
Continental transitions between forests dominated by ectomycorrhizal or
arbuscular mycorrhizal trees occur relatively abruptly along
climate-driven decomposition gradients; these transitions are probably
caused by positive feedback effects between plants and microorganisms.
Symbiotic nitrogen fixers—which are insensitive to climatic controls on
decomposition (compared with mycorrhizal fungi)—are most abundant in
arid biomes with alkaline soils and high maximum temperatures. The
climatically driven global symbiosis gradient that we document provides a
spatially explicit quantitative understanding of microbial symbioses at
the global scale, and demonstrates the critical role of microbial
mutualisms in shaping the distribution of plant species.