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Abstract Detail

Ecological Section

Hartsock, Jeremy A. [1], Vitt, Dale H. [1], Ebbs, Stephen [1], House, Melissa [1].

Net Nitrogen Mineralization in Boreal Wetlands: A Test of Early Success for Canadian Oil Sands Reclamation.

Globally, peat forming wetlands store about 25-33% and 9-16% of the world’s soil organic carbon and nitrogen (N) pools, respectively, and annually provide a global ecosystem service by reducing atmospheric CO2 concentrations. In the boreal zone, peatlands are classified into three general site types (bogs, poor fens, and rich fens) based on differences in vegetation, pore-water chemistry, and source of water. Bogs and poor fens have a ground layer and peat profile dominated by the genus Sphagnum, whereas rich fen ground layers and peat profiles are true moss-dominated, and exhibit increased vascular plant cover. In Alberta Canada, peatland complexes occupy approximately 45% of the boreal zone. Underlying this peatland/upland landscape are large bitumen deposits (i.e., ‘oil sands'). Open-pit mining for bitumen removes all surface vegetation and soil, and sterile saline sand is deposited into ‘in-pits’ after bitumen extraction. Using the in situ buried bag technique, we measured net N mineralization rates along a moisture gradient within a reclamation watershed established on an in-pit. The objective was to use net N mineralization as one indicator of below-ground ecosystem health, and determine if net N mineralization rates at this site are comparable to six nearby benchmark fens. At benchmark sites, we determined that net N mineralization rates increase markedly along a Sphagnum-dominated to true-moss dominated gradient, with rich fens exhibiting net N mineralization rates up to 50 times higher than those in Sphagnum-dominated systems. Despite these higher net N mineralization rates in rich fens, inorganic N concentrations in pore-water remain low. We conclude that along the bog-rich fen gradient, the type of ground layer vegetation, and hence peat type, controls rates of net N mineralization. At the reclamation site, two years after watershed establishment, net N mineralization rates were similar to the fen benchmarks; however, at drier sites, net N mineralization was dominated by high net nitrification rates not common in fens. We conclude that net N mineralization in early successional stages of reclamation, where ground layers have not yet developed, is strongly influenced by soil wetness, and could be a key indicator of below-ground system health.

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1 - Southern Illinois University, Plant Biology, Carbondale, IL, 62901, USA

oil sands

Presentation Type: Oral Paper:Papers for Sections
Session: 21
Location: Salon 17/18/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 1:45 PM
Number: 21002
Abstract ID:417
Candidate for Awards:None

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