Thin section studies of Calluna heathland soils subject to prescribed burning

Abstract

Abstract. Soil microstructures and biological activity were studied in thin sections of Culluna heathland soils subject to periodic burning. Freely drained Brown Podzolic soils from a species‐rich heath at Dinnet Muir, Aberdeenshire, Scotland were compared with shallow Humo‐ferric Podzols with a thick humus layer (5–10 cm) supporting a species‐poor heath at Balmenach, Aberdeenshire.Structures with greater porosity occurred in all Dinnet soils and the most recently burned Balmenach soil. Burning led to an increase in soil porosity which gradually disappeared after a period of 2–3 years. Soils of the recently burned site had more enchytraeid worms than those burned ten years previously. Most of the Dinnet soil samples were dominated by extremely fine granular structure which could have been produced by flocculation of well decomposed organic matter or by enchytraeid worms. In recently burned sites the increase in soil macro‐ and microbial activities may lead to the formation of composite structures.Regular burning every 10–15 years has been the land management practice in Scottish heathlands to ensure the production of fresh browse of nutritious heather shoots for herbivores. The near‐ground microclimate and regeneration mechanisms of heathland plants are well adjusted to the periodic disturbance by fire. We found that the gradual decrease in surface soil porosity over time can be restored by prescribed burning. Soil structure and the distribution and continuity of pores in the soil profile directly affect soil water movement and retention. These factors have important ecological implications for post‐fire vegetation recovery.