Document: KRI-3-59-38

Production and transport of dissolved carbon in arctic tundra microcosms: The roles of vegetation and water flow.

JUDD, K.E.* and G.W.KLING

University of Michigan, Ann Arbor, MI 48104-1048 1

Abstract:
Production and export rates of dissolved C were measured in arctic tundra microcosms of three vegetation types (tussock, intertussock, and wet sedge). Microcosms were flushed with water at different frequencies to simulate storm events and determine mass export of dissolved C. Production rates of dissolved C in the absence of flushing were 32.8 (intertussock), 6.08 (tussock), and 1.13 (wet sedge) g C g-1 of soil d-1. Production per gram of above ground biomass was 0.046 (intertussock), 0.016(tussock) and 0.003 (wet sedge) g C m-2 d-1. Total dissolved C production was dominated by dissolved organic C (DOC) in intertussock (33.8 g C g-1 d-1) and tussock (5.75 g C g-1 d-1) soils, while in wet sedge soils, DOC was consumed (-0.25 g C g-1 d-1) and dissolved inorganic C (DIC) production (1.31 g C g-1 d-1) dominated total C production. The ratio of DOC to DIC exported dropped with increased flushing frequencies. Dissolved C yield per gram of soil were greatest from intertussock microcosms and lowest from wet sedge soils at all flushing frequencies. Total yield of dissolved C and DOC increased with increased flushing frequency. The increase was asymptotic in intertussock microcosms and linear in tussock and wet sedge microcosms. Mass export per liter of water added declined as flushing frequency increased. Export and production of dissolved C were strongly correlated with above ground biomass, but not below ground biomass or photosynthetic rates. Soil C content was also correlated with dissolved C export. Photosynthetic rates were greatests in tussock (3.34 g C m-2 day-1), followed by wet sedge (2.45 g C m-2 day-1), and intertussock (0.42 C m-2 day-1) vegetation. UV absorbance characteristics of soil waters were related to the overlying vegetation. The results indicate that arctic tundra soils have a high potential for dissolved C export and that water flow and vegetation type are important controls on dissolved C export. This information should contribute to our understanding of C cycling in the Arctic.

Keywords: C balance; C export; Arctic; tundra ecosystems; increased water flow

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