Multiple global change factors cause declines of a temperate bryophyte

ABSTRACT

Background

Climate change, nutrient enrichment and land use have been predicted to alter bryophyte abundance and performance; we expect these factors to interact, yet experiments addressing their joint effects are missing.

Aims

We tested the responses of Brachythecium rutabulum, a common temperate moss species, to single and combined effects of future climatic conditions, grazing, light limitation and nutrient enrichment. We predicted that future climatic conditions, intense grazing, light limitation and nutrient enrichment have all negative effects on the survival and photosynthetic condition of B. rutabulum, and their joint effects become strong even if individual factors have only weak effects (multiple stress hypothesis).

Methods

We measured after two growing seasons biomass and chlorophyll fluorescence of transplanted moss colonies in full-factorial treatments of fertilisation, exclusion of sheep grazing and light amendment by LED lamps, replicated in ambient and future climatic conditions.

Results

Future climate and fertilisation had negligible effects on colony biomass and chlorophyll fluorescence of bryophyte colonies, whereas light amendment had positive effect on chlorophyll fluorescence and grazing exclusion had positive effect on colony biomass. Colony biomass and chlorophyll fluorescence decreased with increasing number of global change factors.

Conclusion

Supporting the multiple stress hypothesis, individually weak global change factors can combine to strong joint effects.

HIGHLIGHTS

• Multiple global change factors have relatively strong negative effects on a bryophyte even if the effects of single factors are weak.

• We did not find evidence of multiplicative interactions (e.g. synergies) between multiple global change factors. Nevertheless, the additive effects of combined treatments showed increasing linear response with greater number of factors acting in combination.

• Amended light availability promotes bryophyte photosynthetic condition, whereas intense grazing may be a disturbance factor having negative effects on bryophytes.

• Considering multiple global change effects operating simultaneously is required for improved predictions of plant responses to global environmental change.

KEYWORDS:

• Climate change
• grazing
• land use
• light limitation
• multiple stress hypothesis
• nutrient addition
• transplant experiment

Acknowledgments

We thank the personnel of Bad Lauchstädt station for assistance in material acquisition, watering transplants during the acclimation and taking care of experimental facility. Christiane Roscher is thanked for her help in the acquisition of the transplants. Saara Oilinki assisted in the measurement of chlorophyll fluorescence. We are grateful to Maria-Theresa Jessen and Konrad Kirsch for help in maintaining the experimental treatments at eDiValo. We thank the staff of the Bad Lauchstädt Experimental Research Station and Martin Schädler for their work in maintaining the GCEF plots and infrastructures of the Global Change Experimental Facility (GCEF), and Harald Auge, François Buscot, Stefan Klotz, Thomas Reitz and Martin Schädler for their role in establishing the GCEF.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contributions

Risto Virtanen: Conceptualisation, performing experiment, laboratory analysis, statistical analysis and writing of the original draft.

Susanne Dunker: Performing the experiment, commenting on and reviewing the original draft.

Stanley W. Harpole: Project administration, conceptualisation, data analysis and commenting on the original draft.

Anu Eskelinen: Funding acquisition, conceptualisation, performing the experiment, and commenting on the original draft.

Data availability statement

Data are available at Dryad https://doi.org/10.5061/dryad.qjq2bvqkx

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/17550874.2024.2330659

Additional information

Funding

The research was supported by Academy of Finland (grant 29719) to A.E. We appreciate the Helmholtz Association, the Federal Ministry of Education and Research, the State Ministry of Science and Economy of Saxony-Anhalt and the State Ministry for Higher Education, Research and the Arts Saxony to fund the Global Change Experimental Facility (GCEF) project.