Resprouting in European beech confers resilience to high-frequency fire

Abstract

Abstract European beech (Fagus sylvatica L.) can regenerate successfully from seeds after mixed-severity fires with mid-to-long fire return intervals (>60 years). However, if fire return interval is lower than the age of sexual maturity, post-fire seeding will be limited, leaving vegetative resprouting as the only viable option for recovery. This means that the forecasted increase in fire frequency driven by climate change may erode beech forest resilience to fire. Here, we surveyed tree regeneration in a European beech forest affected by two consecutive fires, in 2003 and 2017, and applied experimental clipping of tree saplings to address the following questions: (1) What is the fire resistance and post-fire recovery via resprouting of tree saplings? (2) Which factors drive post-fire resprouting of beech saplings? (3) Does post-fire clipping of tree saplings increase the probability of survival and resprouting vigor? We monitored 2195 beech saplings and 953 saplings of other tree species during three consecutive years, from 2018 to 2020. Almost all beech saplings were top-killed by fire, and two-thirds of them died completely. However, 3 years after the second fire, 30 per cent of beech saplings survived by resprouting from the base. Post-fire resprouting was less likely in small-diameter saplings and in those more injured by fire. Overall, the second fire did not cause a major decline of beech regeneration and consequently did not alter the dominant species composition of post-fire recovery. Given the low specific resistance to fire, post-fire resprouting of saplings is therefore a key component of beech resilience to short-interval fires. The effects of clipping on post-fire survival and resprouting vigor were very limited, suggesting the unsuitability of actively clearing burned beech regeneration as a post-fire management prescription. In conclusion, basal resprouting from beech saplings after fire-induced top-kill led to a higher-than-expected resilience of beech to short-interval fires (i.e. circa 15 years).