Effects of increased temperature and precipitation on soil biogeochemical processes in Cambridge Bay, Canada

Abstract

Increasing atmospheric temperature is preferentially higher in the Arctic than the mid or low latitude over the last few decades. Pattern of precipitation is also changing with warming but more unpredictable. We conducted an experiment to examine the effects of increased temperature and precipitation on CO2 flux and soil and microbial properties in the high Arctic Canada since 2012. The study site was Cambridge Bay on the southeast coast of Victoria Island, Nunavut (69° 07' 48" N, 105° 03' 35" W). Carex spp. and Dryas integrifolia are dominant vegetation types in this dry tundra. A full factorial design was used in this warming and wetting experiment. Warming was implemented with a hexagon type of open top chambers (OTCs) with a 2-m diameter, and we added 0.5 mm of water every week throughout summer. The atmospheric and soil temperature increased about 0.48 and 0.65 °C in non-warming plots compared to OTCs, respectively. The relative humidity in OTCs was about 1 % lower than that in non-warming plots. Net ecosystem exchange (NEE) and ecosystem respiration were measured by a manual chamber method. NEE was negative (CO2 uptake > production) during mid July to mid August, and CO2 fluxes during a growing season did not show significant differences among treatments. Inorganic N and water extractable C contents were not significantly different among treatments either. Additionally, we measured the extracelluar enzyme activities associated with C and N dynamics at the same time, however, no apparent relationship was found with CO2 fluxes, inorganic N content, and water extractable C. Currently, we are analyzing microbial biomass through extracting microbial phospholipid fatty acids and dissolved organic matter composition using 15T FT-ICR/MS. We expect to understand the effects of warming and wetting on soil biogeochemical processes and DOM compositions through integrating all results produced in 2018 and 2019.