Rapid post‐fire re‐assembly of species‐rich bryophyte communities in Afroalpine heathlands

Abstract

Questions In some fire‐prone ecosystems, bryophytes play a crucial role by providing the surface fuel that controls the fire return interval. Afroalpine heathlands are such an ecosystem, yet almost nothing is known about the bryophytes in this system. We do not know the level of species richness, or if there is a successive accumulation of species over time, or if some species are adapted to specific phases along the successional gradient, for example early‐successional species sensitive to competition. Location Afroalpine heathlands in Ethiopia. Methods We made an inventory of all bryophytes in 48 plots of 5 m × 5 m, distributed along a chronosequence from 1 to 25 years post fire. The heathlands are located between 3500 m and 3800 m a.s.l. and are managed by traditional pasture burning with fire intervals of 8–20 years. Results We found in total 111 taxa of bryophytes. Post‐fire mortality was almost 100%. The youngest plots had only a few cosmopolitan species often found after fire. Initially, species richness increased monotonically while starting to level off around 15 years after fire, when many plots had around 30 species and a high cover of Breutelia diffracta, which is a key ground‐living species, important as surface fuel. Most species were found with sporophytes, a pattern even stronger for the most frequent species. Conclusions Interestingly, bryophyte diversity is already remarkably high by only 15 years after total eradication. The relatively slow accumulation of species in the first years after fire suggests that dispersal in space, and not time, is the major mechanism by which sites regain their diversity (i.e. spore banks play a smaller role than colonization of wind‐borne spores). This indicates that the high species richness is built up through colonization from surrounding heathlands, and perhaps also from higher‐altitude alpine grasslands and lower‐altitude forests, and that the bryophyte diversity in this system is maintained by the traditional fire and grazing management.

Do plant traits influence primary succession patterns for bryophytes and vascular plants? Evidence from a 33‐year chronosequence on bare chalk

“…Consistent with our findings, Hylander et al. (2021) also found that Funaria hygrometrica was strongly associated with early successional sites. This cosmopolitan species is known to colonise newly disturbed sites around the world, particularly following fires.…”

“…Hylander et al. (2021) found that the richness of bryophytes increased rapidly from 3 to 42 following fire in Afroalpine heathlands in Ethiopia. However, as with our study they also found that the richness levelled off after 15 years.…”

Fire disturbance promotes biodiversity of plants, lichens and birds in the Siberian subarctic tundra

“…Regarding the densities of the most abundant bird species, we found no significant differences between burnt and unburnt areas, ). An increase in species richness with time since fire on burnt areas reflects the dispersal of species and was also described for Afroalpine heathlands (Hylander et al, 2021) and subalpine Rocky Mountain vegetation (Coop et al, 2010). The hump-shaped pattern in our study might be explained by the intermediate disturbance hypothesis (Connell, 1978), as early and late successional species build a common species pool at an intermediate recovery state.…”

“…Frost et al, 2020; Tsuyuzaki et al, 2018), very few studies have assessed the impacts of fire on biodiversity at the landscape level. From Afroalpine heathlands, for example, it is known that a fire‐induced landscape mosaic can lead to species rich communities and increase their resilience to warming (Hylander et al, 2021; Johansson et al, 2018).…”

“…From Afroalpine heathlands, for example, it is known that a fireinduced landscape mosaic can lead to species rich communities and increase their resilience to warming (Hylander et al, 2021;Johansson et al, 2018).…”