Abstract
Press disturbances are stressors that are extended or ongoing relative to the generation times of community members, and, due to their longevity, have the potential to alter communities beyond the possibility of recovery. They also provide key opportunities to investigate ecological resilience and to probe biological limits in the face of prolonged stressors. The underground coal mine fire in Centralia, Pennsylvania has been burning since 1962 and severely alters the overlying surface soils by elevating temperatures and depositing coal combustion pollutants. As the fire burns along the coal seams to disturb new soils, previously disturbed soils return to ambient temperatures, resulting in a chronosequence of fire impact. We used 16S rRNA gene sequencing to examine bacterial and archaeal soil community responses along two active fire fronts in Centralia, and investigated the influences of assembly processes (selection, dispersal and drift) on community outcomes. The hottest soils harbored the most variable and divergent communities, despite their reduced diversity. Recovered soils converged toward similar community structures, demonstrating resilience within 10–20 years and exhibiting near-complete return to reference communities. Measured soil properties (selection), local dispersal, and neutral community assembly models could not explain the divergences of communities observed at temperature extremes, yet beta-null modeling suggested that communities at temperature extremes follow niche-based processes rather than null. We hypothesize that priority effects from responsive seed bank transitions may be key in explaining the multiple equilibria observed among communities at extreme temperatures. These results suggest that soils generally have an intrinsic capacity for robustness to varied disturbances, even to press disturbances considered to be ‘extreme’, compounded, or incongruent with natural conditions.
Highlights
Human interactions with and alterations of environmental systems are important components of global change (Allen et al, 2014)
In some situations of anthropogenic disturbance, such as pollution, native microbial communities can provide bioremediative functions to support ecosystem recovery (Ruberto et al, 2009; Desai et al, 2010; Fuentes et al, 2015; Ma et al, 2016). Because of their foundational roles in driving important ecosystem processes, understanding how microbial communities respond to press disturbance can provide insights into the potential for ecosystems to recover
Paired-end sequence merging, quality filtering, denois- from 0.105 to 1.29 (maximum distance between ing, singleton-sequence removal, chimera checking, and different samples was 4.49; Supplementary Figure 2; open-reference Operational Taxonomic Unit (OTU) and alpha diversity among technical replicates picking were conducted using a UPARSE workflow provided in Supplementary Table 2)
Summary
Human interactions with and alterations of environmental systems are important components of global change (Allen et al, 2014). Paired-end sequence merging, quality filtering, denois- from 0.105 to 1.29 (maximum distance between ing, singleton-sequence removal, chimera checking, and different samples was 4.49; Supplementary Figure 2; open-reference Operational Taxonomic Unit (OTU) and alpha diversity among technical replicates picking were conducted using a UPARSE workflow provided in Supplementary Table 2).
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