Field experiment shows competition for light is key mechanism behind loss of plant diversity from eutrophication and lack of grazing – ScienceDaily

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The research team around Prof. Dr. Anu Eskelinen from the University of Oulu (Finland) used the Global Change Experimental Facility (GCEF) at the UFZ research center in Bad Lauchstädt for his experiments. Scientists from the UFZ, iDiv and various universities use the GCEF platform to investigate the influence of different climate models and land use intensities on the structure of plant communities – in particular food webs and interactions between species.

Anu Eskelinen, who was a guest scientist at the UFZ and iDiv for several years, pursued a new experimental approach: the team illuminated the low-growing plants in the grassland directly with LED lamps, thereby increasing the amount of light. In addition to this treatment, fertilizer was applied to some plots and sheep grazing was used on others.

The experiment showed a sharp decline in species richness and biodiversity due to artificial fertilization if the areas were not grazed at the same time. When the researchers added LED lights, the loss in biodiversity was mitigated. Later, researchers excluded sheep from half of the plots, causing species richness and diversity to decrease. At the same time, total non-grazing vegetation cover increased, which in turn reduced the light available to plants. Importantly, adding light to the undergrowth plants mitigated this loss in diversity. “These results suggest that herbivores are a dominant factor controlling competition for light and plant diversity,” says first author Anu Eskelinen.

The research team believes that the results from the field trials should be taken into account for future grassland management and conservation policies. “Our results underline the importance of preserving native herbivores and using sustainable grazing as a management measure,” Anu Eskelinen continues.

Prof. Dr. Stan Harpole, co-author and head of the Department of Physiological Diversity at the UFZ and iDiv, adds: “This study underscores the value of carefully designed manipulative field experiments, which we need to comprehensively test the causes of diversity loss. Only thanks to the excellent infrastructure of the Global Change Experimental Facility of the UFZ and the support of the Bad Lauchstädt research station as well as the cooperation with iDiv were we able to expand our understanding and test the theory under more realistic conditions”.

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materials provided by Helmholtz Center for Environmental Research – UFZ. Note: Content can be edited for style and length.

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