Summer temperature – but not growing season length – influences radial growth of Salix arctica in coastal Arctic tundra

Abstract

Arctic climate change is leading to an advance of plant phenology (the timing of life events) with uncertain impacts on tundra ecosystems. Although the lengthening of the growing season is thought to lead to increased plant growth, we have few studies of how plant phenology change is altering tundra plant productivity. Here, we test the correspondence between 14 years of Salix arctica phenology data and radial growth. We sampled 38 Salix arctica individuals across the landscape on Qikiqtaruk – Herschel Island, Yukon Territory, Canada. We used dendroecology and linear mixed-effect models to test the influence of growing season length and climate variables on growth. We found that summer temperature best explained annual variation in growth. We found no strong evidence that green-up date, earlier leaf senescence date or total growing season length had any direct or lagged effects on growth. Growth was not explained by interannual variation in precipitation, MODIS surface greenness (NDVI), or sea ice concentration. Our results demonstrate that at this site, for the widely-distributed species S. arctica, temperature – but not growing season length – influences radial growth. These findings challenge the assumption that advancing phenology and longer growing seasons will increase the productivity of all plant species in Arctic tundra ecosystems.