Post‐fire recovery of desert bryophyte communities: effects of fires and propagule soil banks

Abstract

Questions As changing wildfire regimes modify North American deserts, can fires of greater severity and frequency negatively impact the recovery of native bryophyte communities, which are not adapted to such disturbances? Does post‐fire recovery result from the survival of existing surface plants, dormant propagules in sub‐surface soil banks (dispersal in time) or aerial immigration into burned sites (dispersal in space)? Do wildfires negatively affect the survival of propagules in bryophyte soil banks? Location Continental arid shrublands, Mojave Desert, southwestern US. Methods We characterized bryophyte communities along a post‐fire chronosequence spanning three decades across sites where fires had different severities, ages and potential fuels. Three community profiles (surface, soil and aerial) were surveyed with a combination of on‐site surveys and emergence germination techniques. We tested for differences in beta diversity, species composition and richness with PERMDISP, PERMANOVA and linear mixed models, respectively. Results Burn severity was associated with differences in beta diversity, species composition and richness, while burn age was associated only with different composition and richness. No effect of potential fuel availability was found. More variation in composition was explained by significant differences among profiles than by other fire attributes. Species richness (but not beta diversity) was higher in soil profiles than in aerial spore rain or existing surface communities. Soils from the oldest and least severe burns had a greater number of species than soils from recent and more severe burns. Conclusions Bryophyte soil banks are common elements of desert soils that facilitate post‐disturbance recovery of communities, but soil banks are themselves threatened by the intensifying frequency and severity of wildfires in North American deserts. Recovery of desert bryophyte communities seems to begin (but not necessarily conclude) within 30 yr after wildfires. In the near future, communities may become perturbed from historical patterns as contemporary fire regimes undergo extensive changes.

Changes in Multi-Level Biodiversity and Soil Features in a Burned Beech Forest in the Southern Italian Coastal Mountain

“…Change in bryophyte species composition after the fire also follows the general model due to the environmental post-fire conditions with an increase in the frequency of acrocarpous species in burned soil and pleurocarpous in unburned soil [138][139][140]. The high frequency of cosmopolitan moss Funaria hygrometrica in the burned ground, mainly those affected by high intensity fire, is in accordance with several previous studies on post-fire bryophyte dynamics in the Mediterranean vegetation [140][141][142][143].…”

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

“…Although the exact mechanism is uncertain, at least one study has provided an example of regeneration from spore banks after fire in a North American desert community (Smith et al, 2014). Studies investigating post-fire succession often find a rather slow return of the pre-fire bryophyte species composition.…”

Similar mechanisms underlie beta diversity of bryophytes in two archipelagos with different isolation time

“…We found similar beta diversity patterns in these two archipelagos, indicating that the time since isolation is longer enough than the time needed for the successful colonization of bryophytes, that is,~30 yr (Smith et al 2014, Jagodzi nski et al 2018. Thus, we cannot conclude that isolation time has no effect on species composition of bryophyte communities, unless assessing more natural archipelagos with a larger range of isolation time (especially those newly formed archipelagos), or conducting experiments to manually control the effect of isolation time.…”

“…Highlighting this ability, Hutsemekers et al (2008) found that for 56% of bryophyte species, recruits dispersed at least 6–86 km from source populations in <50 yr. In previous studies, bryophyte communities have been found to restore successfully within ~30 yr after catastrophic disturbance (e.g., wildfire; Smith et al 2014, Jagodziński et al 2018). In contrast, Pharo et al (2004) found evidence for lower richness and shifts in species composition in newly formed fragments (<25 yr) compared to near contiguous habitats, suggesting that some species with weaker dispersal ability may exhibit greater time lag between colonization events.…”