Do burned areas recover from inside? An experiment with soil fauna in a heterogeneous landscape.

摘要

The post-fire soil faunal communities are formed both by animals having survived the fire and by colonizers from the surrounding landscape. The relative impact of these processes is largely affected by fire intensity. However, with the same fire intensity, the severity of the fire and, thus, the survival of soil animals could vary depending on environmental heterogeneity. We hypothesized that much fewer soil animals would survive the same fire intensity on shallow, dry soils than on deep, moist soils. To clarify the impact of soil depth and moisture on animal survival after fire, we conducted a burning experiment in the laboratory. Soil samples containing indigenous populations of soil fauna were taken along two transects from the top, slope and foot of two respective rocky outcrops within a mixed coniferous forest in Central Sweden. Half of the samples were burnt and half were left unburnt. Burning depth varied between 24 mm (soils from the top of the gradient) to 12 mm (slope and foot soils) indicating a difference in flammability. The proportion of animals surviving fire seemed to be fairly independent of burning depth (42 to 62% survival rate). Contribution of eggs which survived fire in the soil to the overall animal abundance restoration was negligible (1-3%). A multi-trophic approach resulted in different sensitivity estimates to artificial burning of various parameters. Abundance and biomass of all fauna groups studied was more sensitive to fire than species richness. Collembolans and macrofauna predators were the groups most tolerant to fire, while oribatid mites and macrofaunal detritivores showed higher mortality after the fire treatment. Despite a more pronounced alteration of the components of soil food-web by burning in the lowland Sphagnum plots, they may be important as refugia, especially for more slowly moving soil-dwelling macro- and microarthropods.