Abstract
As major disturbance agents, natural catastrophes impact habitats, thereby maintaining the dynamics of ecological communities. Such discrete events are expected to positively affect biodiversity because they generate high habitat heterogeneity and thus numerous ecological niche opportunities. Species typical of open and semi-open habitats, which are often of high conservation concern in modern anthropized landscapes, may benefit most from recurrent natural catastrophes that regularly reset ecosystems. We investigated bird community changes and species-specific responses to wildfire at two recently burnt temperate, montane-subalpine forest stands in an inner-Alpine Swiss valley, with a special focus on red-listed and conservation priority species. We compared bird community changes in burnt forests (spanning 13 years) with bird assemblages occurring in adjacent non-burned forest stands that served as quasi-experimental controls. Strong species-specific responses to wildfire were evidenced, resulting in a dramatic post-fire decrease in overall bird abundance and species richness. Yet, red-listed bird species and conservation priority species in Switzerland were substantially more common in burnt than in control forest stands. Many red-listed species showed a bell-shaped numeric response to wildfire over time, suggesting low habitat suitability just after fire, high habitat suitability at pioneer and early stages of vegetation succession, followed by a long-term decrease in suitability while vegetation becomes denser, especially at ground level. As established for Mediterranean regions where wildfires are especially frequent, this study shows that forest fires can also boost the populations of red-listed and priority bird species typical of open and semi-open habitats in temperate biomes. Prescribed forest fire might represent a management option for preserving threatened elements of biodiversity despite the intense public debate it will trigger.
Highlights
Most ecosystems are in essence dynamic natural systems in which biological community structure and population densities are modulated by ever changing environmental conditions that
Studies describing the impact of wildfire on avifauna of grasslands and savannahs (e.g. [12, 15,16,17]), boreal and temperate forests (e.g. [11, 18,19,20,21]), tropical rainforests (e.g. [9, 22,23]) and Mediterranean ecosystems (e.g. [24,25,26,27,28,29,30]) mostly indicate shifts in communities towards open-land or non-forest bird species
This study shows that wildfires dramatically impact forest avifauna and provide niche opportunities for a wide palette of bird species that are red-listed and/or bear highest conservation priority in Switzerland
Summary
Shifts in ecological communities can result either from environmental changes that progressively model habitat or from sudden catastrophes that disrupt the ecosystem functioning [3]. The latter are commonly defined as disturbances [3] and include, among others, fires, floods, landslides, avalanches, storms, droughts and tidal waves The post-fire recolonization by pioneer plant species causes a rapid rejuvenation of the ground and field layer, but leaves numerous patches of bare ground Taken together, this creates a patchy mosaic of semi-open habitats [13]. This apparent deterministic change in the bird assemblage is likely to favour beta-diversity because burnt and unburnt patches often occur side by side, sometimes even in an intricate manner
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