Comparing the responses of bryophytes and short‐statured vascular plants to climate shifts and eutrophication

Abstract

Summary 1. Few experimental studies have tested how abundance and diversity of grassland bryophytes respond to global environmental changes such as climate shifts and eutrophication. Because bryophytes in grasslands are low-statured, and because plant height is a key functional trait governing plant responses to resource gradients, their responses to these factors could resemble those of better-studied small vascular plants. Alternatively, traits unique to bryophytes could lead to qualitatively different responses than those of small vascular plants. 2. In a semi-arid Californian grassland system, where bryophytes are at relatively low abundance and their ecology has been little studied, we compared changes in cover and species richness of bryophytes and short-statured vascular plants in response to 5 years of experimental fertilization, springtime watering and fertilization + watering, which produced strong gradients in vascular plant biomass. 3. Supporting our hypotheses, the cover and richness of both bryophytes and short vascular plants were negatively related to total community biomass and tall vascular plant cover, and declined in response to the fertilization + watering treatment, in which the cover of tall vascular plants most strongly increased. 4. Two divergent responses were also observed as follows: watering alone increased the cover of bryophytes but not short vascular plants, while fertilization alone reduced the cover of short vascular plants but not bryophytes. 5. Bryophytes and short-statured vascular plants in grasslands both may be expected to decline under projected global changes in climate and nutrient deposition that enhance total community biomass and competitive pressure. However, shifts in either precipitation or eutrophication regimes alone may have differential effects on bryophytes and short vascular plants in grasslands, and organism-specific plant functional traits must also be considered.

Herbivores rescue diversity in warming tundra by modulating trait-dependent species losses and gains

“…1 , Supplementary Table 2 ), indicating that without herbivores warming-induced intensification of light competition can be severe enough to cause local extinctions of bryophytes. This is consistent with expectations, as bryophytes are among the smallest land plants, and thus likely to suffer strongly from competition for light and to respond rapidly to climatic and other environmental changes 49 , 50 . Even though warming did not induce losses of vascular plants, the greatest losses of vascular plants were observed in warmed and fertilized plots when herbivores were excluded (five species lost per plot).…”

Direct and indirect effects of land use on bryophytes in grasslands

“…Moreover, in our study irrigation had no significant effect on bryophyte cover. This is in contrast to Virtanen et al (2017) who found an increasing bryophyte cover in only irrigated experimental plots under Mediterranean climate conditions in California. However, high rates of fertilization seem to be particularly negative for bryophytes.…”

“…Müller et al (2012) also observed a decrease in bryophyte richness with increasing productivity, along a land-use intensity gradient in German grasslands. Virtanen et al (2017) found a reduction of bryophyte species richness and cover in experimental plots, which were irrigated and fertilized. However, these previous studies were not able to identify the mechanisms behind the impacts of fertilization.…”

Seasonal variation of secondary metabolites in nine different bryophytes

“…Our results suggest that species in this group are specialized to the conditions in late successional stages with regard to their biochemistry, as well as to grow in mats or cushions and to have high relative growth rates in order to withstand the competition from vascular plants (During, ; Hedwall et al., ; Virtanen et al., ). Producing metabolites only on demand seems to be favorable for bryophyte species in late successional stages.…”

“…Thus, bryophytes can reduce erosion and often act as prerequisite for establishing vascular plants by creating microhabitats (Streitberger, Schmidt, & Fartmann, 2017;Zamfir, 2000). In late successional stages in grasslands, even low bryophyte abundances can facilitate the regeneration of vascular plants by influencing nutrient retention and water cycling (Virtanen, Eskelinen, & Harrison, 2017). However, the net outcome is often depending on environmental conditions (Doxford, Ooi, & Freckleton, 2013).…”