Climate manipulation (warming and wetting) experiment in Cambridge Bay, Canada

Atmospheric temperature in the Arctic has increased more than the mid or low latitude, and this trend is expected to continue in the future. Precipitation pattern is also changing due to warming but more unpredictable. A number of studies have been carried out to investigate the responses of terrestrial ecosystems to increased temperature, but less have focused on the effects of precipitation changes or combined effects of temperature and precipitation. We conduct an experiment to examine the effects of both warming and increased summer precipitation on ecosystem characteristics in the Canadian high Arctic since 2012. The study site is located in Cambridge Bay on the southeast coast of Victoria Island, Nunavut (69° 07' 48" N, 105° 03' 35" W). The ecosystem is dry tundra composed of Carex spp. and Dryas integrifolia as dominant vegetation types. A climate manipulation experiment was designed in a factorial combination with warming (ambient vs. increased temperature) and precipitation (ambient vs. increased precipitation). The hexagon types of open top chambers (OTCs) in a 2-m diameter were used to increase temperature, and 2 L of water/per plot (4 m² area) was added every week throughout summer. The OTCs increased ca. 1 and 0.5 °C of atmospheric and soil temperature, respectively. In 2018, we measure net ecosystem exchange and ecosystem respiration using a manual chamber method and extract dissolved organic carbon and inorganic nitrogen from June to September to observe both treatment effects and seasonal changes. We also analyze microbial biomass through extracting microbial phospholipid fatty acids and microbial activities by measuring extracellular enzyme activities. Plant cover is estimated using point-intercept method, and normalized difference vegetation index is measured throughout the summer. We expect to understand the single and combined effects of increased temperature and precipitation on soil biogeochemical processes with a link of changes in plant and microbial activities through synthesizing all the results produced in the previous and coming years.