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Published November 19, 2018
How climate drives the functional characteristics of vegetation across the globe has been a key question in ecological research for more than a century. A University of Wyoming researcher contributed to a new study that helped clarify an answer, one that found climate globally may play less of a role than local factors.
“We found that plant communities around the globe can be characterized along surprisingly few attributes: They mostly vary in height and resource acquisitiveness,” says Daniel Laughlin, a UW associate professor in the Department of Botany. “However, these differences could not easily be predicted by climatic conditions, suggesting that local-scale drivers like disturbance and competition play important roles.”
These local factors include microclimate; fine-scale soil properties; disturbance regime, which is the frequency and severity of disturbances, such as fires or floods; and successional dynamics, which is the change in plant composition at a site over time since a major disturbance event.
Laughlin was co-author of the new study that is highlighted in a paper, titled “Global Trait-Environment Relationships of Plant Communities,” published today (Nov. 19) in Nature Ecology and Evolution, a monthly peer-reviewed scientific journal that covers all aspects of research on ecology.
Helge Bruelheide, a professor in the Institute of Biology at Martin Luther University Halle-Wittenberg, was the paper’s lead author. Laughlin contributed trait data and expertise on analyzing trait-environment relationships, and he edited drafts of the paper.
Trait composition of plant communities across the globe is captured by two main dimensions and is shaped predominantly by environmental filtering, but is only weakly related to global climate and soil gradients. Plant functional traits -- which include leaf size, plant height and tissue density -- directly affect ecosystem functions and are fundamental for managing and predicting biodiversity and ecosystem change.
“Everyone who travels will notice similarities in vegetation, even across different continents. The similarities and differences can be quantified by variation in their functional traits,” Laughlin explains. “For example, mountain forests in Europe resemble mountain forests in Wyoming because both environments have selected for conical evergreen trees that tolerate snow, despite differences in species composition. These similarities -- in form and function among plant communities -- are common features of the planet. However, we found that trait variation at the local scale cannot easily be predicted by broad climate variables.”
Researchers performed the first global, plot-level analysis of trait-environment relationships, using a novel database with more than 1.1 million vegetation plots and 26,632 plant species with trait information.
“It took four years to assemble and analyze the data, but some of the primary data was collected decades ago,” Laughlin says. “It was the culmination of millions of hours of work.”
This dataset was used to test the hypothesis that environmental filtering is the main global structuring force of community trait composition in plants.
The paper shows that the two main community trait axes -- plant stature and resource acquisitiveness -- capture half of the global trait variations. Thus, similar climate and soil conditions support communities differing greatly in mean trait values and, within plot trait variation, does not vary systematically with macroenvironment.
The paper’s results found only limited support for researchers’ second hypothesis that global climate played a larger role in trait composition of plant communities. Community-level trait composition was poorly captured by global climate and soil variables.
“The biggest surprise was that the dominant differences -- height and resource acquisitiveness -- among communities was not explained by variation in climate,” Laughlin says. “This suggests that similar climate and soil conditions can produce very different vegetation, and that sites of different climates can sometimes have very similar vegetation.”