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Research indicates that biodiversity in more humid forests exerts a greater influence than in arid environments, offering essential insights for individuals striving to conserve and rehabilitate these ecosystems

Biodiversity plays a crucial role in every ecosystem. Studies have demonstrated that a richer variety of plant and animal species strengthens ecosystem functionality and stability, rendering habitats more robust against challenges like pests, diseases, and climate change.

However, the significance of biodiversity varies. Recent research from the University of Michigan unveils practical implications of this reality in forests, providing crucial insights for land managers and conservationists striving to safeguard these habitats.

“Diversity is vital wherever we investigate,” stated Peter Reich, a professor of environment and sustainability and the director of the Institute for Global Change Biology at the University of Michigan. “However, in our experiments, we found it is particularly significant in humid climates.”

Reich served as the lead researcher on a project that included 15 tree diversity experiments worldwide, covering a range of climates. Analysis of around 100,000 trees from nearly 130 species revealed that trees in wetter climates with more diverse neighbors exhibited greater growth. In contrast, this effect was reduced or absent in drier areas.

“This provides a more detailed understanding of how biodiversity operates in diverse environments,” noted Reich, who is also a professor at the University of Minnesota. “If you are considering restoration or replanting, it is highly beneficial to introduce diverse trees, especially in humid regions.”

Reich emphasized that the term “wetter” encompasses more than just tropical rainforests that might typically come to mind. According to the study’s criteria, Michigan’s forests, for instance, also fall under the wet category.

The initiative was facilitated by the broader Tree Diversity Network, the largest global network of tree diversity experiments comprising 34 distinct sites. The resultant study, published in the journal Nature Ecology & Evolution, features contributors from nearly a dozen nations representing over 30 organizations.

The research was also supported by international funding sources, including the U.S. National Science Foundation, German Research Foundation, São Paulo Research Foundation, and the University of Chinese Academy of Sciences.

“We discovered enhanced tree growth in neighborhoods with diverse species and functional characteristics—for instance, specific leaf area and wood density,” stated study lead author Liting Zheng, who conducted the research as a postdoctoral fellow at Michigan’s School of Environment and Sustainability and is now affiliated with the German Center for Integrative Biodiversity Research.

“Our findings underscore the significance of creating and upholding high neighborhood diversity in forest management—particularly to optimize the potential of biodiversity as a nature-based climate solution in humid areas.”

Understanding the forest beyond the trees

While prior research has investigated the advantages of biodiversity concerning climate, their findings have been inconsistent. The reasons for this are not entirely understood, according to Reich, but many studies have faced a couple of notable drawbacks.

For one, many have concentrated on a single experimental site. Among those that engaged multiple sites for a broader analysis, there tended to be a general assessment of biodiversity as an average metric for the entire community.

The current study employed a significantly more detailed methodology. Researchers at each experimental site evaluated tree biodiversity by examining every individual tree and their surrounding neighbors.

“What differentiates our study is that it includes 15 long-term experiments with extensive numbers of trees,” Reich remarked. “Instead of assessing an entire community, we focused on individual trees and around eight of their neighbors, asking, ‘Are those neighbors diverse or not?’”

He acknowledged that a limitation of their investigation is that, due to the nature of the experiments, the trees studied were all relatively youthful, aged between 4 to 14 years. However, there’s no clear rationale suggesting that the findings wouldn’t apply to older forests.

This methodology allowed researchers to demonstrate the significant influence of biodiversity in wet forests, along with an additional intriguing and vital discovery. While biodiversity appears to be more consequential in humid climates, its effect during wetter years in those climates is minimal.

“Diversity seems to be more beneficial under average conditions, which is relevant for management,” Reich noted. “There is a notion that biodiversity will significantly assist during extreme years, supported by some evidence, but our data did not reflect this.”

Kai Zhu, associate professor of geospatial data science, and Inés Ibáñez, professor of ecosystem science and management—both affiliated with Michigan’s School of Environment and Sustainability—also contributed to the study.

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