Direct and indirect effects of land use on bryophytes in grasslands

Steffen Boch; Eric Allan; Jean-Yves Humbert; Yasemin Kurtogullari; Malie Lessard-Therrien; Jörg Müller; Daniel Prati; Nora Simone Rieder; Raphaël Arlettaz; Markus Fischer

doi:10.1016/j.scitotenv.2018.06.323

Direct and indirect effects of land use on bryophytes in grasslands

Sci Total Environ. 2018 Dec 10:644:60-67. doi: 10.1016/j.scitotenv.2018.06.323. Epub 2018 Jul 4.

Authors

Affiliations

¹ Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland; Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland. Electronic address: steffen.boch@wsl.ch.
² Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
³ Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland.
⁴ Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland; Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland.
⁵ Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland; College of Biological Science, University of Guelph, 50 Stone Road East, Guelph, Ontario, Canada.
⁶ Department of Nature Conservation, Heinz Sielmann Foundation, Unter den Kiefern 9, 14641 Wustermark, Germany.
⁷ Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland; Swiss Ornithological Institute, Valais Field Station, Rue du Rhône 11, 1950 Sion, Switzerland.

PMID: 29980086
DOI: 10.1016/j.scitotenv.2018.06.323

Abstract

Land-use intensification is the major threat for biodiversity in agricultural grasslands, and fertilization has been suggested as the most important driver. A common explanation for the decline of bryophyte diversity with higher land-use intensity is an indirect negative effect via the increase in vascular plant productivity, which reduces light levels for bryophytes. However, direct negative effects of land-use intensification may also be important. Here, we disentangle direct and vascular plant biomass mediated indirect effects of land use on bryophytes. We analyzed two complementary datasets from agricultural grasslands, an observational study across 144 differently managed grasslands in Germany and an experimental fertilization and irrigation study of eleven grasslands in the Swiss Alps. We found that bryophyte richness and cover strongly declined with land-use intensity and in particular with fertilization. However, structural equation modelling revealed that although both direct and indirect effects were important, the direct negative effect of fertilization was even stronger than the indirect effect mediated by increased plant biomass. Thus, our results challenge the widespread view that the negative effects of fertilization are mostly indirect and mediated via increased light competition with vascular plants. Our study shows that land use intensification reduces bryophyte diversity through several different mechanisms. Therefore, only low-intensity management with limited fertilizer inputs will allow the maintenance of bryophyte-rich grasslands.

Keywords: Fertilization; Grassland biodiversity; Land-use intensification; Liverwort; Moss; Structural equation modelling.