Direct and indirect effects of land use on bryophytes in grasslands

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.

Dry grasslands of the central valleys of the Alps from a European perspective: the example of Ausserberg (Valais, Switzerland)

“…Nowadays traditional irrigation systems are largely replaced by modern devices such as aerial sprinkler systems, often in combination with fertilisation to increase yields (e.g. Boch et al 2018a). While irrigated grasslands are still mown or grazed, former arable areas have been transformed to extensive pastures, and less productive land has been abandoned.…”

Evidence for a possible extinction debt in Swiss wetland specialist plants

“…Fast extinctions of bryophyte species in habitat remnants have been shown for epiphytes (Hylander & Weibull, 2012), and there is at least one documented example of a wetland bryophyte species (Meesia longiseta) that vanished from the wetlands of Zürich in the early 20th century (Hofmann et al, 2007). Although good long-distance dispersal abilities of many bryophytes due to their small spores (Hutsemekers, Dopagne, & Vanderpoorten, 2008;Patiño & Vanderpoorten, 2018) and their capability for asexual propagation (e.g., by means of specialized propagules or clonal expansion; Rydin, 2009) should reduce the risk of local extinction in bryophytes, bryophytes are also known to react sensitively to changing environmental conditions such as changing water levels or increasing nutrients (Bergamini & Pauli, 2001;Boch et al, 2018;Vitt & Chee, 1990 This delayed response makes it possible to prevent or at least to reduce future extinctions of these species through specific conservation measures (Kuussaari et al, 2009;Otsu, Iijima, Nagaike, & Hoshino, 2017). The first goal must be to prevent any further reduction in wetland area.…”

Changes in Spatial Distribution of Bryophytes under CMIP6 Future Projections on the Qinghai-Tibet Plateau

“…Bryophytes, a group of early nonvascular land plants (Kenrick and Crane, 1997), are used as an ideal bioindication of climate uctuations as their speci c eco-physiological and biological features (Tuba et al, 2011;Porada et al, 2016b;Becker Scarpitta et al, 2017). Bryophytes likewise held a key position in terms of carbon/nutrient cycling (Elbert et al, 2012;Lindo et al, 2013;Vicherová et al, 2020), grasslands biodiversity conservation (Boch et al, 2018), forest renewal (Kiebacher et al, 2016;Jiang et al, 2018;Ingerpuu et al, 2019), water and soil nutrients cycling and reserve (Soudzilovskaia et al, 2013) and environment pollution monitoring (Meyer et al, 2012;Wang et al, 2015). However, recent studies dedicate that changing climate would strongly affect ecosystem structure and function, biodiversity, species richness of Bryophytes, resulting in niches and geographical distribution shifts (Alatalo et al, 2015;Wang et al, 2019), and by the contrary, Bryophytes' niches changes will also alter the key ecosystem functions and sustainability processes (Lang et al, 2009;Hooper et al, 2012).…”