How resilient is Calluna vulgaris to drought during germination and its
seedling stage?
Abstract
The coastal heathlands of North-west Europe are valuable cultural
landscapes, created and maintained over millennia by a land-use regime
involving burning and grazing. These heathlands are now critically
threatened throughout their range by land-use change and, increasingly,
climatic changes. The climatic change impacts are complex, as the
coastal heathland regions are experiencing increased temperature and
precipitation, but also increased frequency and severity of extreme
events, such as drought. Previous studies reveal that established
heathland vegetation, including Calluna, are vulnerable to drought, but
also that these vulnerabilities vary throughout the range, and with
successional stage after fire. Recruitment from seed is an important
regeneration strategy for Calluna heathland vegetation after burning,
and our study is the first to assess how the seed germination and early
seedling growth of Calluna respond to drought. We will do this in a lab
germination experiment, where we will expose Calluna seeds to five
different drought treatments, from -0.25 MPa to -1.7 MPa, and measure
germination, and record germination percentage, germination rates, and
seedling growth, below-ground allocation, and functional traits
(Specific Leaf Area, Specific Root Length). To allow assessment of
variation in drought responses due to geographic origin, successional
stage, and the maternal plants’ drought exposure, we will conduct this
experiment on seeds from 540 Calluna plants sampled from across three
drought treatments (control, 50%, and 90% coverage), in three
successional stages after fire (pioneer, building, mature), in two
regions (60N, 65N), using a factorial design.