Data from: The response of the alpine dwarf shrub Salix herbacea to altered snowmelt timing: lessons from a multi-site transplant experiment

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.

气候变化正在改变高山与北极生态系统的春季融雪模式，而这类变化或会影响植物的物候、生长与繁殖过程。若要预测高山植物对融雪时间变化的响应，我们需要了解其性状可塑性（trait plasticity）、该性状对生长与繁殖的影响，以及植物所具备的本地生境优势（home-site advantage）程度。本研究以常见的多年生矮灌木北极柳（Salix herbacea）为对象，通过将其植丛块在早暴露脊生境与晚暴露雪床微生境之间开展互易移植（reciprocal transplant）实验，探究该物种对春季融雪时间变化的响应。移植后，我们在两个生长季内对其物候、形态与适合度性状（fitness traits）以及叶片受损情况进行了监测。结果显示，相较于雪床生境，脊生境中的北极柳展叶更早，但发育时长更长，且叶片尺寸更小。脊生境中，更长的物候发育时长与更小的叶片尺寸，与有性繁殖（sexual reproduction）能力下降存在关联；而雪床生境中，更大的叶片尺寸与适中的发育时长，则与克隆繁殖（clonal reproduction）能力提升存在关联。克隆繁殖与有性繁殖均未对融雪时间的改变产生响应。本研究未在有性与克隆繁殖层面发现本地生境优势。叶片受损概率取决于融雪时间（即植株暴露时长），但并未对适合度性状产生短期影响。综上，本研究涉及的北极柳种群可通过物候与叶片尺寸的可塑性变化响应融雪时间的偏移，同时维持克隆与有性繁殖的水平。本地生境优势的缺失表明，北极柳或许并未适应不同的微生境。因此，该研究种群不太可能通过快速适应来应对气候变化，但其响应也不会受到小尺度本地适应的限制。短期来看，雪床生境中的植株因茎密度较高，或可维持种群存续。但从长期来看，在融雪提前的情境下，叶片尺寸与开花量下降、物候发育时长增加，以及受损暴露风险提升，或会降低北极柳的整体生存表现。