Root phenology unresponsive to earlier snowmelt despite advanced aboveground phenology in two subarctic plant communities

Earlier snowmelt at high latitudes advances aboveground plant phenology, thereby affecting water, nutrient and carbon cycles. Despite the key role of fine roots in these ecosystem processes, phenological responses to earlier snowmelt have never been assessed belowground. We experimentally advanced snowmelt in two contrasting plant community types, heath and meadow, in northern Sweden and measured above- and belowground phenology: leaf-out, flowering and fine root growth. We expected earlier snowmelt to advance both above- and belowground phenology, and shrub-dominated heath to be more responsive than meadow. Snow melted on average nine days earlier in the manipulated plots than in controls, and soil temperatures were on average 0.9 C higher during the snowmelt period of three weeks. This resulted in small advances in aboveground phenology, but contrary to our expectations, root phenology was unresponsive with root growth generally starting before leaf-out. These responses to the snowmel...