Ground-Dwelling Arthropod Community Responses to Recent and Repeated Wildfires in Conifer Forests of Northern New Mexico, USA

Abstract

The increasing frequency and severity of wildfires in semi-arid conifer forests as a result of global change pressures has raised concern over potential impacts on biodiversity. Ground-dwelling arthropod communities represent a substantial portion of diversity in conifer forests, and could be particularly impacted by wildfires. In addition to direct mortality, wildfires can affect ground-dwelling arthropods by altering understory characteristics and associated deterministic community assembly processes (e.g., environmental sorting). Alternatively, disturbances have been reported to increase the importance of stochastic community assembly processes (e.g., probabilistic dispersal and colonization rates). Utilizing pitfall traps to capture ground-dwelling arthropods within forest stands that were burned by one or two wildfires since 1996 in the Jemez Mountains of northern New Mexico, United States (USA), we examined the potential influences of deterministic versus stochastic processes on the assembly of these diverse understory communities. Based on family-level and genera-level arthropod identifications, we found that the multivariate community structures differed among the four fire groups surveyed, and were significantly influenced by the quantities of duff, litter, and coarse woody debris, in addition to tree basal area and graminoid cover. Taxon diversity was positively related to duff quantities, while taxon turnover was positively linked to exposed-rock cover and the number of logs on the ground. Despite the significant effects of these understory properties on the arthropod community structure, a combination of null modeling and metacommunity analysis revealed that both deterministic and stochastic processes shape the ground-dwelling arthropod communities in this system. However, the relative influence of these processes as a function of time since the wildfires or the number of recent wildfires was not generalizable across the fire groups. Given that different assembly processes shaped arthropod communities among locations that had experienced similar disturbances over time, increased efforts to understand the processes governing arthropod community assembly following disturbance is required in this wildfire-prone landscape.

Biodiversity conservation through the lens of metacommunity ecology

“…Among the relatively few studies that have explicitly used a mechanistic approach, generalities have been elusive because anthropogenic drivers influence metacommunity functioning in multiple, often interactive, ways. [96][97][98][99][100] This is corroborated by meta-analyses showing that responses after disturbance are highly variable, and depend, among other things, on the type of disturbance, habitat, and trophic role. [101][102][103] Therefore, to understand global change effects on the conservation of populations and biodiversity, we need to understand how each metacommunity process, alone or in concert, is altered by these global change drivers.…”

“…However, evidence for the impact of global change on metacommunity processes and functioning has been largely circumstantial. Among the relatively few studies that have explicitly used a mechanistic approach, generalities have been elusive because anthropogenic drivers influence metacommunity functioning in multiple, often interactive, ways 96–100 . This is corroborated by meta‐analyses showing that responses after disturbance are highly variable, and depend, among other things, on the type of disturbance, habitat, and trophic role 101–103 .…”

Wildfire influences individual growth and breeding dispersal, but not survival and recruitment in a montane amphibian

“…Growth ultimately is contingent on the availability of food resources, however, which for boreal toads includes primarily arthropods, principally ants (Formicidae), beetles (Coleoptera), and spiders (Bull, 2006; Bull & Hayes, 2009; Campbell, 1970). Wildfire can increase the diversity and abundance of arthropods and other invertebrates (Bess et al, 2002; Buddle et al, 2006; Ferrenberg et al, 2019; Jackson et al, 2012), and high‐severity fires can result in an extended “fire pulse” characterized by a flux of invertebrate prey to aquatic and terrestrial habitats (Harris et al, 2018; Malison & Baxter, 2010; Silins et al, 2014). Post‐fire increases in prey availability therefore may have stimulated the growth of boreal toads between 2019 and 2020 at burned sites in our study area.…”

Forest disturbance and arthropods: small‐scale canopy and understory disturbances alter movement of mobile arthropods

“…Dispersal capacity of species contributes to processes of community assembly at landscape and local scales, including patterns of probabilistic dispersal and recolonization following natural and anthropogenic disturbances. Studies of arthropod community assembly have often found that a combination of stochastic (neutralbased) and deterministic (niche-based) processes shape patterns of assembly (Thompson and Townsend 2006, Farnon Ellwood et al 2009, Rominger et al 2009, Ferrenberg et al 2019, Perry et al 2020), but disturbances can mediate the relative importance of these mechanisms. For example, following tree mortality caused by bark beetles, the relative importance of deterministic processes related to plant and soil habitat characteristics increased in strength for grounddwelling arthropods, while stochastic processes related to dispersal limitations increased for soildwelling arthropods (Ferrenberg et al 2016).…”