Limited effects of early snowmelt on plants, decomposers, and soil nutrients in Arctic tundra soils

Abstract

In addition to warming temperatures, Arctic ecosystems are responding to climate change with earlier snowmelt and soil thaw. Earlier snowmelt has been examined infrequently in field experiments, and we lack a comprehensive look at belowground responses of the soil biogeochemical system that includes plant roots, decomposers, and soil nutrients. We experimentally advanced the timing of snowmelt in factorial combination with an open‐top chamber warming treatment over a 3‐year period and evaluated the responses of decomposers and nutrient cycling processes. We tested two alternative hypotheses: (a) Early snowmelt and warming advance the timing of root growth and nutrient uptake, altering the timing of microbial and invertebrate activity and key nutrient cycling events; and (b) loss of insulating snow cover damages plants, leading to reductions in root growth and altered biological activity. During the 3 years of our study (2010–2012), we advanced snowmelt by 4, 15, and 10 days, respectively. Despite advancing aboveground plant phenology, particularly in the year with the warmest early‐season temperatures (2012), belowground effects were primarily seen only on the first sampling date of the season or restricted to particular years or soil type. Overall, consistent and substantial responses to early snowmelt were not observed, counter to both of our hypotheses. The data on soil physical conditions, as well interannual comparisons of our results, suggest that this limited response was because of the earlier date of snowmelt that did not coincide with substantially warmer air and soil temperatures as they might in response to a natural climate event. We conclude that the interaction of snowmelt timing with soil temperatures is important to how the ecosystem will respond, but that 1‐ to 2‐week changes in timing of snowmelt alone are not enough to drive season‐long changes in soil microbial and nutrient cycling processes.

Effect of elevation, season and accelerated snowmelt on biogeochemical processes during isolated conifer needle litter decomposition

“…6 ), while mass losses from deployed conifer needles were similar across the full 700-meter gradient ( Table S2 ). This was surprising considering the differences in snowmelt timing across elevation ( Table S1 ); however, these results agree with other studies that have shown minimal impact on microbial structure with no lasting effects on microbial biomass and nutrient cycling processes after experimental snowmelt manipulations ( Conner, Gill & Harvey, 2017 ; Darrouzet-Nardi et al, 2019 ). A plausible explanation is that ecological resilience overcomes the effects of accelerated snowmelt without additional climate variables of higher temperatures and lower precipitation ( Darrouzet-Nardi et al, 2019 ).…”

Investigating the sensitivity of soil heterotrophic respiration to recent snow cover changes in Alaska using a satellite-based permafrost carbon model

“…All model input data sets were reprojected into a 1 km resolution Albers projection and resampled to an 8 d time step consistent with the model simulations. Other ancillary data sets included the 30 m National Land Cover Database (NLCD) 2011 (Jin et al, 2013), 50 m SOC estimates for Alaska (to 1 m depth; Mishra et al, 2017), and the global 9 km mineral soil texture data developed for the SMAP L4SM algorithm (De Lannoy et al, 2014). The dominant NLCD land cover type within each 1 km pixel was used to define the modeling domain, with open water and perennial ice and snow areas excluded (Fig.…”

Climate change alters temporal dynamics of alpine soil microbial functioning and biogeochemical cycling via earlier snowmelt

“…Indeed, an increased frequency and severity of freeze-thaw cycles in soil due to reduced snow cover during the winter months could impact microbial and biogeochemical cycles during snowmelt, regardless of its timing. Any or all of these winter and spring climate change impacts could potentially lead to cross-season legacy effects [23,24]. Earlier spring snowmelt, in particular, could disrupt the temporal dynamics of plant and soil microbial resource demands [16,25], with potential consequences for ecosystem C and N retention in these widespread and vulnerable mountain ecosystems [26].…”