After the burn: factors affecting land snail survival in post-prescribed-burn woodlands

Abstract

Prescribed burning is commonly used for vegetation management. Whereas effects on vegetation are apparent, effects of these burns on ground-dwelling invertebrates are not. Land snails are especially susceptible to burns. Snail loss occurs directly from burns, but may also occur post-burn because of altered habitat conditions, although post-burn loss has not previously been tested. We used a field experiment to investigate snail survival and factors affecting survival in post-burn habitats. We exposed snails (Discidae: Anguispira alternata) to combinations of intact leaf litter, wood shelters, burned leaf litter, charred wood and ash added to leaf litter, to simulate a variety of post-burn conditions. Half of the replicates were watered every 3 d, which allowed detection of desiccation effects in comparison to ambient water conditions. The on-going drought resulted in high snail mortality. Watering increased survival and, as a consequence, growth. Snail mortality was higher in habitats with burned leaves and/or wood than in unburned habitats. Higher temperatures and rapid initial mortality in burned habitats, and increased survival with watering, indicated that the major cause of post-fire mortality was desiccation, rather than starvation. Contrary to expectations, snails in burned-leaf habitats grew more than snails in unburned habitats, and this greater growth was associated with higher soil pH. Snails surviving fires in burned woodland areas likely have high post-burn mortality. Our experiment highlights the negative impacts of burned woodland habitats on some nontarget organisms and indicates that prescribed burns should be avoided during exceptionally dry conditions.

Impacts of the 2019–2020 bushfires on New South Wales biodiversity: a rapid assessment of distribution data for selected invertebrate taxa

“…In addition, there are changes to species composition after fires, with a higher proportion of larger invertebrates remaining, as smaller invertebrates may struggle to re-colonize burnt areas due to low vagility and/or greater susceptibility to desiccation under drier conditions (Buckingham et al, 2019). Studies of land snails have shown that snails living in burnt areas have higher mortality than in unburnt areas, indicating that survivors or re-colonizers of burnt areas may struggle to survive (Ray & Bergey, 2015). Rapid weed growth after fires has a negative effect on invertebrates, and also makes these areas more susceptible to future fires (Sands, 2018).…”

“…The loss of detritivores can result in an increased depth of dry leaf litter, increasing fuel load and also adding to the risk of further fires. Many invertebrates are negatively affected by current fire management regimes (Ray & Bergey, 2015;Sands, 2018), with a need for fuel reduction burning to follow a micromosaic patch pattern in order to avoid the loss of overall invertebrate biodiversity (New et al, 2010;Sands, 2018).…”

Land snails on two different sides of Mt. Galunggung

“…Gradually the forest succession was occupied by snails. The snails found in the area may come from surviving snail in refuge surround, similar to the snails in burnt area [9]. More snail species were probably dispersed from surrounding area of Galunggung where not impacted by the eruption and established the communities.…”

Tall grass prairie ecosystem management—a gastropod perspective

“…The result is that most sites recently burned (<2 years) had gastropod composition similar to unmanaged sites, demonstrating rapid recolonization in this patchy ecosystem. Ray and Bergey (2015) showed that in favourable weather conditions snail communities in post-burn habitats that include leaf litter showed growth rate increases due to higher soil pH following fire. In Prairie habitat once reestablishment of the litter layer is underway, recolonization from adjacent sites such as Wet Forest patches or drainage sites (especially by aquatic species) can be rapid.…”