Functional trait variation of Anemone nemorosa along macro‐ and microclimatic gradients close to the northern range edge

Climate warming is affecting ecosystems worldwide, and slow-colonizing
forest under- storey species are particularly vulnerable if they are
unable to track climate change. However, species’ responses to climatic
conditions in terms of growth, reproduction and colonization capacity may
vary with the distance to their distribution range edge. Anemone nemorosa
is known to be a slow colonizing forest herb dependent on forest cover in
the southern and central part of its distribution range, whereas at its
northern distribution range (and at higher elevations) it also occurs in
open habitats. Here, we investigated the response of plant functional
traits of Anemone nemorosa in cen- tral Norway (close to its northern
distribution range edge) to a macroclimatic gra- dient (elevation), two
microclimatic gradients (forest density and distance to forest edge) and a
competition treatment (removal of neighbouring vegetation). We aimed to
identify which environmental conditions (light, temperature, soil pH
and/or soil organic matter) drive A. nemorosa’s responses. In a total of
90 plots, we measured six functional traits of A. nemorosa (plant height,
biomass, specific leaf area, seed number, seed mass,and germination
percentage). We found stronger variation in environmental conditions along
the macroclimatic elevational gradient, than along the microclimatic
gradients of forest density and distance to forest edge, and this was also
reflected in A. nemorosa’s responses. Light availability, in interaction
with temperature, was the key environmental variable driving plant
performance, while soil conditions were less important. The competition
release treatment had a negative effect on A. nemorosa in our study sites,
indicating that the facilitative effect of the neighbouring vegetation may
be stronger than the competitive effect. Our study suggests that A.
nemorosa, close to its northern distribution range edge, has the capacity
to cope with climate change through phenotypic responses, and that light
and temperature are the key drivers of these responses.