Postfire root distribution of Scots pine in relation to fire behaviour

Fire can potentially have a large direct impact on tree roots and, thus, contribute to reduced vitality. Tree canopy status after fire should have an impact on the postfire production of fine roots, further affecting root function. We analyzed the standing crop of live and dead roots in Pinus sylvestris L. with varying degrees of crown scorch, 1ayear after fire in northern Sweden. On the burned sites, total Pinus live fine-root biomass was 74% of that at the control sites, and it was only 19% of the control for rootsa < 2amm, indicating an 80% reduction due to fire. Root mortality was highest for high-scorch trees, but this was probably due to greater depth of burn in the organic soil for these trees and not to higher fire intensity per se. Fine-root production was also assessed by an ingrowth experiment. This showed relatively similar fine-root production in both control trees and fire-damaged trees, indicating a high allocation to root growth for the damaged trees, to make up for lost root function. Root dynamics after fire are related to a number of factors, and direct effects are determined by the depth of burn in the organic soil layer. Indirect, long-lasting effects could be due mainly to girdling of coarse roots close to tree stems and canopy loss.