Fast Responses of Root Dynamics to Increased Snow Deposition and Summer Air Temperature in an Arctic Wetland.

Ludovica D’Imperio,Bo Elberling,Marie F. Arndal,Cecilie S. Nielsen,Inger K. Schmidt

doi:10.3389/fpls.2018.01258

Ludovica D’Imperio, Bo Elberling + Show 3 more

Open Access

https://doi.org/10.3389/fpls.2018.01258

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Abstract

In wet tundra ecosystems, covering vast areas of the Arctic, the belowground plant biomass exceeds the aboveground, making root dynamics a crucial component of the nutrient cycling and the carbon (C) budget of the Arctic. In response to the projected climatic scenarios for the Arctic, namely increased temperature and changes in precipitation patterns, root dynamics may be altered leading to significant changes in the net ecosystem C budget. Here, we quantify the single and combined effects of 1 year of increased winter snow deposition by snow fences and summer warming by open-top chambers (OTCs) on root dynamics in a wetland at Disko Island (West Greenland). Based on ingrowth bags, snow accumulation decreased root productivity by 42% in the 0–15 cm soil depth compared to ambient conditions. Over the growing season 2014, minirhizotron observations showed that root growth continued until mid-September in all treatments, and it peaked between the end of July and mid-August. During the season, plots exposed to experimental warming showed a significant increase in root number during September (between 39 and 53%) and a 39% increase in root length by the beginning of September. In addition, a significant reduction of root diameter (14%) was observed in plots with increased snow accumulation. Along the soil profile (0–40 cm) summer warming by OTCs significantly increased the total root length (54%), root number (41%) and the root growth in the 20–30 cm soil depth (71%). These results indicate a fast response of this ecosystem to changes in air temperature and precipitation. Hence, on a short-term, summer warming may lead to increased root depth and belowground C allocation, whereas increased winter snow precipitation may reduce root production or favor specific plant species by means of reduced growing season length or increased nutrient cycling. Knowledge on belowground root dynamics is therefore critical to improve the estimation of the C balance of the Arctic.

Highlights

Wetlands are widespread in the Arctic and cover about 7% of its vegetated area (Walker et al, 2005)
In a warmer and in particular drier future climate, this C stock may become available for biological decomposition and arctic wetlands play a central role in balancing the uptake and release of carbon dioxide (CO2) and methane (CH4) on a global level (Swindles et al, 2015)
The results presented in this study quantify the short-term effects (1 year) of snow accumulation, summer warming and their combination on root production and phenology in an arctic wetland

Summary

Introduction

Wetlands are widespread in the Arctic and cover about 7% of its vegetated area (Walker et al, 2005). In these ecosystems, the accumulation of soil organic carbon (SOC) exceeds the rates of decomposition due to the low soil temperature and lack of oxygen during periods of high water-table (Sullivan et al, 2008). In the Arctic, the belowground plant biomass exceeds its aboveground counterpart (Mokany et al, 2006; Iversen et al, 2015; Wang et al, 2016a) and represents an important component of soil nutrient cycling and net ecosystem C budget (Iversen et al, 2015). As concluded by Blume-Werry et al (2016) neither the knowledge from non-Arctic ecosystems, nor projections of aboveground to belowground production, reflect seasonal dynamics of root growth in arctic plant communities and limited data is available on root phenology in this region (Radville et al, 2016)

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