Fire is a powerful ecological and evolutionary force that regulates organismal traits, population sizes, species interactions, community composition, carbon and nutrient cycling and ecosystem function. It also presents a rapidly growing societal challenge, due to both increasingly destructive wildfires and fire exclusion in fire‐dependent ecosystems. As an ecological process, fire integrates complex feedbacks among biological, social and geophysical processes, requiring coordination across several fields and scales of study. Here, we describe the diversity of ways in which fire operates as a fundamental ecological and evolutionary process on Earth. We explore research priorities in six categories of fire ecology: (a) characteristics of fire regimes, (b) changing fire regimes, (c) fire effects on above‐ground ecology, (d) fire effects on below‐ground ecology, (e) fire behaviour and (f) fire ecology modelling. We identify three emergent themes: the need to study fire across temporal scales, to assess the mechanisms underlying a variety of ecological feedbacks involving fire and to improve representation of fire in a range of modelling contexts. Synthesis: As fire regimes and our relationships with fire continue to change, prioritizing these research areas will facilitate understanding of the ecological causes and consequences of future fires and rethinking fire management alternatives.

Following disturbances such as wildfires, oak seedlings must form a symbiotic association with mycorrhizal fungi to survive. Wildfires, however, reduce available mycorrhizal fungal propagules in the soil. Ectomycorrhizal (ECM) fungi on oak seedlings sampled in severely burned (7 sites), moderately burned (7 sites), and unburned areas (8 sites) in the Great Smoky Mountains National Park were evaluated 21 months after the 2016 Chimney Tops 2 Wildfire by Sanger sequencing of the nuclear ribosomal DNA internal transcribed spacer region (nrITS; fungal barcode). Sequences were aligned and grouped into Operational Taxonomic Units (OTUs) based on well-supported phylogenetic clades and 98–100% nrITS sequence homology with sequences in GenBank. One hundred seventy-nine root-associated fungi comprising 124 OTUs were recovered after removing duplicates (the same fungus on two or more roots of the same plant). The ECM genus Russula was the most diverse genus (25 OTUs), followed by the Thelephora / Tomentella clade (18 OTUs), Lactifluus (8 OTUs), Lactarius (4 OTUs), and Laccaria aff. laccata (2 OTUs). Russula OTUs were identified more frequently on oak roots from burned areas and in burned soils, suggesting that some Russula taxa may have a selective advantage in burned areas. High alpha diversity occurred within each of the burn categories, but little overlap of taxa occurred between burn categories (high beta diversity). Approximately half of the recovered OTUs (100/179 total root-associated fungi = 55.9%) were found on a single plant. Oak seedlings growing in moderately and severely burned areas 21 months after a fire were capable of forming root associations with available fungi. In contrast to the expectation that root-associated fungal diversity would be reduced after a wildfire, diversity 1 year after the Chimney Tops 2 Fire was high with ectomycorrhizal Laccaria , Russulaceae , and Thelephoraceae dominating. This study suggests that the availability of ECM fungi post-fire is not a barrier to oak re-establishment.

Fire is an inherently evolutionary process, even though much more emphasis has been given to ecological responses of plants and their associated communities to fire. Here, we synthesize contributions to a Special Feature entitled ‘Fire as a dynamic ecological and evolutionary force’ and place them in a broader context of fire research. Topics covered in this Special Feature include a perspective on the impacts of novel fire regimes on differential forest mortality, discussions on new approaches to investigate vegetation‐fire feedbacks and resulting plant syndromes, synthesis of fire impacts on plant–fungal interactions, and a meta‐analysis of arthropod community responses to fire. We conclude by suggesting pathways forward to better understand the ecological and evolutionary consequences of fire. These include developing ecological and evolutionary databases for fire ecology, integrating hierarchical genetic structure or phylogenetic structure, and developing new experimental frameworks that limit context‐dependent outcomes. Read the free Plain Language Summary for this article on the Journal blog.

Here we tested the overarching hypothesis that climate change velocity drives rapid evolution in bud break phenology. With field and common garden studies, we used age cohorts within 17 populations of a foundation riparian tree species distributed across multiple strong environmental gradients in the western US. We provide evidence of contemporary evolution, as young trees in trailing-edge populations have evolved to break bud approximately six days earlier than old trees in these same populations. These populations experience greater water stress than populations at the core of the species’ distribution, and the magnitude of genetic divergence in bud-break phenology is related to the velocity of change in climate water deficit over the last 100 years. This relationship to climate change velocity did not exist in core populations, suggesting that, despite similar rates of change, a threshold of water deficit stress has yet to be surpassed in those regions. Overall, the interactive effects of old trees and trailing edge populations can provide useful insight into centuries of environmental history and each independently represent important benchmarks for understanding the context for contemporary environmental change.