DOI: 10.5443/11463
title: Carbon-flux and Microbial Community Dynamics in Low-Arctic Tundra

description: Arctic ecosystems store large amounts of carbon in organic matter that may contribute to carbon dioxide (CO2) production as climate warms, further enhancing the greenhouse effect. We know that many biological factors, including plant interactions with mycorrhizal fungi and other soil microbes, regulate plant survival and the carbon-balance of arctic tundra, but these interactions are poorly understood. Recently, new advances in technology have allowed us to study belowground communities with resolution not previously possible, leading to new findings about the links between below and above ground community dynamics. Our research uses cutting-edge technology such as stable isotope tracing and molecular methods to investigate the role of soil microbial communities in the response of an Arctic ecosystem to climate change. We found that 1) mycorrhizal fungal networks link plants in tundra and play a critical role in the expansion of shrubs in Arctic landscapes with climate change; 2) as climate warms, tundra shrubs increasingly partner with mycorrhizal fungi that are specialized in the breakdown of the organic carbon stored in tundra soils; and 3) climate warming will alter the diversity and composition of free-living soil microbial communities in Arctic tundra and these changes will also lead to increased losses of carbon from soils. Our data suggest that microbial community change in Arctic tundra will act as a positive feedback to climate change, speeding up the rate of change in Low-Arctic tundra ecosystems.
description: Purpose: Effects of anthropogenic climate change have now been reported in all of the earth's biomes (Rosenzwieg et al. 2008) but Arctic regions, which sustain the highest rates of warming (Trenberth et al. 2007), have been particularly perturbed (Post et al. 2009). The stability of terrestrial Arctic ecosystems is of immediate concern because tundra soils store a disproportionally large share of the earth's C, and increased microbial decomposition of this C will feedback to climate on decadal timescales (Schuur et al. 2009). Soil microbes are central to the C balance of terrestrial ecosystems because of their dual role as decomposers of soil organic matter and as determinants of plant community diversity (van der Heijden et al. 2008), which in turn controls the quality and quantity of C inputs to soils (De Deyn et al. 2008, Bardgett et al. 2008). Yet, despite the importance of Arctic soils in the global C cycle, we know very little of the impacts of climate change on Arctic soil microbial communities, and even less of how these changes will feedback to the stability of tundra plant communities. In "Carbon-flux and Microbial Community Dynamics in Low-Arctic Tundra" we address critical gaps in our understanding of the role of soil microbial communities in the response of an Arctic ecosystem to climate change. Objectives: 1) To assess the ecological role of mycorrhizal networks (MNs) in plant interactions in a Low-Arctic tundra ecosystem; 2) To determine the effects of warming and increased nutrient availability on the ectomycorrhizal (ECM) fungal community of a tundra shrub that is responsive to these climate change factors; 3) To determine the effects of climate warming on Arctic soil fungi and bacteria over time; 4) To assess the role of the mycorrhizal symbiosis in determining C-allocation to tundra plant rhizosphere organisms.
description: Summary: Arctic ecosystems store large amounts of carbon in plants and soil and this carbon may be released and contribute to carbon dioxide production as the climate warms. In the Arctic tundra however, plant interactions with mycorrhizal fungi and other soil microbes that regulate carbon are poorly understood. Across growing seasons, this project is investigating links between below and above ground community processes regarding carbon balance and transfer. Using new advances in technology, this work is identifying key microbial groups in the soil that are involved in the cycling of carbon in Arctic tundra and determining how carbon cycling will respond to climate change.