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 history 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 on Qikiqtaruk–Herschel Island, Yukon Territory, Canada. We analysed stems from 28 individuals using dendroecology and linear mixed-effect models to test the statistical power of growing season length and climate variables to individually predict radial growth. We found that summer temperature best explained annual variation in radial growth. We found no strong evidence that leaf emergence date, earlier leaf senescence date, or total growing season length had any direct or lagged effects on radial growth. Radial growth was also 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.

Recurrent summer drought affects biomass production and community composition independently of snowmelt manipulation in alpine grassland

“…To our surprise, even over 7 years of snow manipulation, altered snowmelt timing had hardly any effects on the vegetation. Several studies in arctic tundra and alpine vegetation observed a similar unresponsiveness in productivity to earlier snowmelt, both above-and below-ground (Baptist et al, 2010;Boyle et al, 2022;Darrouzet-Nardi et al, 2019). It was previously argued that adverse effects of freezing temperatures during earlier snowmelt outweigh beneficial effects of a longer growing season (Wipf et al, 2009) but particularly graminoids exhibit a high freezing resistance even in a fully active state (von Büren & Hiltbrunner, 2022).…”

“…As biomass production may correlate with growing season length (Kudo, 1992), earlier snowmelt was expected to enhance productivity (Rammig et al, 2010). However, experimental studies have provided little evidence of a stimulating effect of earlier snowmelt on biomass production so far (Baptist et al, 2010; Boyle et al, 2022; Darrouzet‐Nardi et al, 2019; Möhl et al, 2022; Wipf et al, 2009). On the other hand, drought periods are known to reduce above‐ground biomass production in different grassland types (Kahmen et al, 2005; Kröel‐Dulay et al, 2022; Mackie et al, 2019), including subalpine meadows (Gilgen & Buchmann, 2009; Ingrisch et al, 2018).…”

Diverse phenotypes of Late Glacial–Early Holocene downy birch (Betula pubescens Erh.) and the morphology of early Preboreal tree stands in southern Schleswig-Holstein

“…Indeed, Betula pubescens growth appears to be little affected by precipitation. Studies in Iceland (Levanič and Eggertsson, 2008), Finland (Welling et al, 2004), and Sweden (Kullman, 1993) have shown that temperature is the significantly more decisive growth parameter (Boyle et al, 2022). Nevertheless, an approximate precipitation minimum can be inferred from the present distribution of the species in the subarctic regions of the Northern Hemisphere.…”

“…Nutrient supply is one of the three major growth-limiting factors for modern Betula sp. at high latitudes along with temperature and precipitation (Boyle et al, 2022;Weih and Karlsson, 1997). While temperature and precipitation during the Late Glacial-Early Holocene can be approached via robust proxy data, the assessment of nutrients in the soil remains a matter of estimation.…”

“…Spring and autumn became warmer, there was probably fewer late spring frosts and au-tumn began later allowing for accelerated wood growth compared to the previous stadial phase (GS-1). However, it is likely that the increased temperatures affected plant growth to a larger extent than the lengthened growing season (Boyle et al, 2022). It is possible that many single and tall Betula pubescens shoots emerged within short periods of time.…”