Abstract
Moorlands dominated by Calluna vulgaris (hereafter Calluna) are globally
rare and under increasing threat of wildfires due to climate change. The
soil seed bank is important for community resilience, but research on
its contribution to regenerating vegetation after moorland fires has to
date focused on prescribed fire or on the short-term (≤ 2 year) impacts
of wildfire. To address the role of the seed bank in long-term
vegetation regeneration, we studied a chronosequence of six wildfire
sites within a Scottish moorland catchment, ranging from 2 to 64 years
since burning. We recorded vegetation composition and sampled the seed
bank. Calluna and Erica spp. comprised 66 % and 27 % of germinated
seeds, respectively, and the majority of vegetation species were not
represented in the seed bank. Canonical Correspondence Analysis (CCA)
revealed that time since fire was a strong predictor of vegetation
species composition, but it had no effect on seed bank composition,
suggesting that the same species dominate the seed bank regardless of
burning. Whilst total seed density was marginally reduced after wildfire
and slightly increased with time, the non-Calluna seed bank was more
notably affected. The proportion of non-Calluna species decreased with
time in both vegetation and seed bank as Calluna cover was
re-established and the seed bank of other species became gradually
depleted. Whilst relative non-Calluna cover in the vegetation was at a
maximum at the start of the chronosequence and then declined, the
proportion of non-Calluna in the seed bank followed a unimodal pattern
after fire and reached a peak after around 35 years. Our results
contribute to the knowledge of how moorland ecosystems regenerate after
severe disturbances, which are likely to become more common as the
climate changes.