Structure and composition of a post-fire ascomycete community: role of abiotic and biotic factors

Abstract

The role of certain abiotic and biotic factors in determining the structure of a post-fire ascomycete community was studied by the laboratory simulation of soil conditions occurring during and following a prairie fire. Aerated steam treatment of prairie soil (35, 40, 55, 70, or 85 °C for 60 s) was used to simulate the elevated soil temperatures generated during a grassland fire. Further manipulations included: (1) addition of ashed remains of prairie grasses to steamed soil surfaces, (2) the incubation of steam-treated soil samples layered over untreated prairie soil, and (3) addition of ash to steamed soil underlain with a layer of untreated soil to create a simulated burn.Across all treatments, species diversity and total number of species were significantly higher in soils steamed at 35, 55, or 70 °C than soils steamed at 40 or 85 °C. The greatest number of species per sample for steaming alone occurred in samples treated at 55 °C. The addition of ash to steamed samples or layering with untreated prairie soil significantly reduced species diversity and total number of species as compared with steamed soil alone. When ash and a subsurface layer of untreated soil were applied together, species diversity, total number of species, and mean number of species for samples steamed at 55 or 70 °C, were significantly greater than when either treatment was added separately. It was found that a simulated burn at 55 or 70 °C promoted the development of a community which most closely resembled a naturally occurring post-fire ascomycete community. This suggested that the structure of the post-fire ascomycete community was in part determined by (1) species responses to elevated soil temperatures, (2) ash deposition, and (3) biotic factors associated with the subsurface soil layers.