Pyrodiversity begets plant–pollinator community diversity

Abstract

Fire has a major impact on the structure and function of many ecosystems globally. Pyrodiversity, the diversity of fires within a region (where diversity is based on fire characteristics such as extent, severity, and frequency), has been hypothesized to promote biodiversity, but changing climate and land management practices have eroded pyrodiversity. To assess whether changes in pyrodiversity will have impacts on ecological communities, we must first understand the mechanisms that might enable pyrodiversity to sustain biodiversity, and how such changes might interact with other disturbances such as drought. Focusing on plant-pollinator communities in mixed-conifer forest with frequent fire in Yosemite National Park, California, we examine how pyrodiversity, combined with drought intensity, influences those communities. We find that pyrodiversity is positively related to the richness of the pollinators, flowering plants, and plant-pollinator interactions. On average, a 5% increase in pyrodiversity led to the gain of approximately one pollinator and one flowering plant species and nearly two interactions. We also find that a diversity of fire characteristics contributes to the spatial heterogeneity (b-diversity) of plant and pollinator communities. Lastly, we find evidence that fire diversity buffers pollinator communities against the effects of drought-induced floral resource scarcity. Fire diversity is thus important for the maintenance of flowering plant and pollinator diversity and predicted shifts in fire regimes to include less pyrodiversity compounded with increasing drought occurrence will negatively influence the richness of these communities in this and other forested ecosystems. In addition, lower heterogeneity of fire severity may act to reduce spatial turnover of plantpollinator communities. The heterogeneity of community composition is a primary determinant of the total species diversity present in a landscape, and thus, lower pyrodiversity may negatively affect the richness of plant-pollinator communities across large spatial scales.

Pyrodiversity promotes avian diversity over the decade following forest fire

“…In contrast with shrubland systems, our finding that biodiversity responds positively to an interaction of pyrodiversity and time since fire possibly results from the complex diversity of habitats created and maintained by fire in conifer landscapes. Indeed, related work on the pyrodiversity-biodiversity hypothesis has found similarly positive results with other taxa in western North America [15], and previous studies have highlighted that different bird species are sensitive to different combinations of fire severity and years since fire [24,28]. Thus, at the scale of individual fires in forested ecosystems, a mosaic of stands of different burn severities-not just the overall degree of burn severity-is likely to produce the greatest diversity of species.…”

“…While recent work has used the Shannon or Simpson index of integer-based post-fire age classes to represent pyrodiversity across fires [13,15], we used the standard deviation of burn-severity scores to measure pyrodiversity within fires. As burn-severity scores are continuous and range from 0 (unburned canopy) to 100 (complete canopy loss), the standard deviation of burn severity provides an index from approximately 0 to 70, with values over 40 representing highly pyrodiverse fires consisting of equal parts high-and low-severity stands.…”

“…a fire perimeter or survey radius). Using bird diversity measurements at two scales (survey points and entire fires) over 10 years following fire, we test the following statistical hypotheses: bird diversity will increase with (i) average burn severity [22] and (ii) pyrodiversity [11,15]; (iii) the effect of pyrodiversity on bird diversity will change with time since fire [24,28], and (iv) these effects will act both on local (i.e. 100 m) and regional (i.e.…”

Refuges from fire maintain pollinator–plant interaction networks

“…Most studies on fire show a positive influence of fire on flowering plant diversity and abundance of insect pollinators (Bond & Scott, 2010;Lamont & Downes, 2011;Ponisio et al, 2016). While this is important for the long-term biodiversity succession in firedisturbed ecosystems, there is concern for the immediate species response during and after fire.…”

Ecology and Conservation of a New Carnivorous Marsupial Species: the Silver-Headed Antechinus (Antechinus argentus)

“…A landmark study by Martin and Sapsis (1992) hypothesised that temporal and spatial variation in fires can promote biodiversity by creating a wider variety of ecological niches available for species. A growing body of literature has supported this hypothesis (see Hutto et al, 2016, Ponisio et al, 2016, Tingley et al, 2016. However, pyrodiversity doesn't always promote biodiversity.…”