Winter snow and spring temperature have differential effects on vegetation phenology and productivity across Arctic plant communities

Abstract

Tundra dominates two‐thirds of the unglaciated, terrestrial Arctic. Although this region has experienced rapid and widespread changes in vegetation phenology and productivity over the last several decades, the specific climatic drivers responsible for this change remain poorly understood. Here we quantified the effect of winter snowpack and early spring temperature conditions on growing season vegetation phenology (timing of the start, peak, and end of the growing season) and productivity of the dominant tundra vegetation communities of Arctic Alaska. We used daily remotely sensed normalized difference vegetation index (NDVI), and daily snowpack and temperature variables produced by SnowModel and MicroMet, coupled physically based snow and meteorological modeling tools, to (1) determine the most important snowpack and thermal controls on tundra vegetation phenology and productivity and (2) describe the direction of these relationships within each vegetation community. Our results show that soil temperature under the snowpack, snowmelt timing, and air temperature following snowmelt are the most important drivers of growing season timing and productivity among Arctic vegetation communities. Air temperature after snowmelt was the most important control on timing of season start and end, with warmer conditions contributing to earlier phenology in all vegetation communities. In contrast, the controls on the timing of peak season and productivity also included snowmelt timing and soil temperature under the snowpack, dictated in part by the snow insulating capacity. The results of this novel analysis suggest that while future warming effects on phenology may be consistent across communities of the tundra biome, warming may result in divergent, community‐specific productivity responses if coupled with reduced snow insulating capacity lowers winter soil temperature and potential nutrient cycling in the soil.

Snow modulates winter energy use and cold exposure across an elevation gradient in a montane ectotherm

“…However, at the population level C . aeneicollis populations are negatively impacted by dry years (Dahlhoff et al, 2019), consistent with a role for interannual variation in cold stress impacting population dynamics (although it remains possible that population declines are driven by the impacts of snow on soil water content, microbial respiration, and primary productivity; Kelsey et al, 2021). We conclude that there is good evidence that interannual variation in snow cover can impact fitness of ectotherms that overwinter in the soil, but more research is required to fully demonstrate the mechanisms.…”

“…Climate change-induced reductions in snow cover will therefore have very different fitness implications for organisms living at different elevations, and these fitness impacts cannot be predicted based on air temperatures alone. This highlights the importance of refining our understanding of how snow interacts with air and soil temperatures to determine organismal performance and fitness, in order to predict the biological impacts of climate change (Fitzpatrick et al, 2019(Fitzpatrick et al, , 2020Kearney, 2020;Kelsey et al, 2021).…”

“…However, when we take into account that snowy years also have delayed spring phenology and are thus longer than dry winters, we found support for our prediction that snowy winters are more energetically demanding. This suggests that impacts of interannual variation in snow cover on winter energy use are likely to come largely from the effects on spring phenology, rather than by increasing energy use due to soil warming (Fitzpatrick et al, 2019; Kelsey et al, 2021).…”

Snow melt timing acts independently and in conjunction with temperature accumulation to drive subalpine plant phenology

“…The relative ability of temperature accumulation and snow melt timing to predict spring phenology in high‐elevation and high‐latitude environments appears to vary among species as well as between phenological stages (Kelsey et al, 2020; Quaglia et al, 2020; Theobald et al, 2017; Wipf, 2010). Following this, we found that temperature accumulation did cue phenology (in tandem with other drivers) for some, but not all species and not all responses.…”

Climate-induced reversal of tree growth patterns at a tropical treeline

“…As warming progresses, mid and high latitudes may begin to experience similar trends to those that we found in Mexico at lower latitudes. The persistence of glaciers and snowpack at the highest elevations or latitudes may buffer habitats from warming-induced stress during the growing season, at least temporarily ( 50 ). In other systems, these buffering effects have resulted in lagged responses of plant community composition and productivity to climate change ( 51 ).…”