The Response of the Alpine Dwarf Shrub Salix herbacea to Altered Snowmelt Timing: Lessons from a Multi-Site Transplant Experiment

Abstract

Climate change is altering spring snowmelt patterns in alpine and arctic ecosystems, and these changes may alter plant phenology, growth and reproduction. To predict how alpine plants respond to shifts in snowmelt timing, we need to understand trait plasticity, its effects on growth and reproduction, and the degree to which plants experience a home-site advantage. We tested how the common, long-lived dwarf shrub Salix herbacea responded to changing spring snowmelt time by reciprocally transplanting turfs of S. herbacea between early-exposure ridge and late-exposure snowbed microhabitats. After the transplant, we monitored phenological, morphological and fitness traits, as well as leaf damage, during two growing seasons. Salix herbacea leafed out earlier, but had a longer development time and produced smaller leaves on ridges relative to snowbeds. Longer phenological development times and smaller leaves were associated with reduced sexual reproduction on ridges. On snowbeds, larger leaves and intermediate development times were associated with increased clonal reproduction. Clonal and sexual reproduction showed no response to altered snowmelt time. We found no home-site advantage in terms of sexual and clonal reproduction. Leaf damage probability depended on snowmelt and thus exposure period, but had no short-term effect on fitness traits. We conclude that the studied populations of S. herbacea can respond to shifts in snowmelt by plastic changes in phenology and leaf size, while maintaining levels of clonal and sexual reproduction. The lack of a home-site advantage suggests that S. herbacea may not be adapted to different microhabitats. The studied populations are thus unlikely to react to climate change by rapid adaptation, but their responses will also not be constrained by small-scale local adaptation. In the short term, snowbed plants may persist due to high stem densities. However, in the long term, reduction in leaf size and flowering, a longer phenological development time and increased exposure to damage may decrease overall performance of S. herbacea under earlier snowmelt.

The snow and the willows: earlier spring snowmelt reduces performance in the low‐lying alpine shrub Salix herbacea

“…This corresponds to Wijk (), who also found increasing stem density in S. herbacea under later snowmelt conditions, and to Sedlacek et al . (), who found larger leaf sizes in S. herbacea growing in late snowbeds relative to early‐exposure sites. In the few alpine accelerated snowmelt studies available, few dwarf shrub species demonstrated any enhancement in vegetative growth, with only low‐lying shrubs evergreen E. nigrum and L. procumbens , two species characteristic to exposed microhabitats, showing increased stem elongation in response to early snowmelt (Wipf, Stoeckli & Bebi ; Wipf ).…”

Non-equilibrium in Alpine Plant Assemblages: Shifts in Europe’s Summit Floras

“…Also, vegetation change on Piz Linard (see above, Wipf et al 2013b) and on Scandinavian mountains (Grytnes et al 2014) seemed to be partly driven by the snow distribution on the summit. Furthermore, the small-scale distribution of snow in complex alpine terrain is extremely important for the distribution of plants: within the same elevation, the date of snowmelt can differ by more than a month within a few metres depending on topography , which influences vegetation and plant populations considerably (for studies on the snowbed species Salix herbacea see Wheeler et al 2015;Sedlacek et al 2015;Cortes et al 2014). Hence, future efforts should clearly focus on not only explaining vegetation changes by temperature but by a combination of temperature and precipitation/snow cover.…”

Testing the niche‐breadth–range‐size hypothesis: habitat specialization vs. performance in Australian alpine daisies

“…These results have implications for the maintenance of biodiversity across landscape mosaics such as alpine regions (Sedlacek et al. ). The low growth rate of some narrow alpine endemics outside their natural habitat may indicate vulnerability of these species to future environmental changes including the arrival of invasive competitors.…”