PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

Y Wu,C Blodau

doi:10.5194/gmd-6-1173-2013

Abstract

Abstract. Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

Highlights

The CryospherePeatlands represent the largest terrestrial soil C pool and a significant N pool
We ran the parameterized, initiated model for 6 yr from 1999 to 2004 and evaluated the simulation results of water table (WT) depth, and depth profiles of soil temperature, moisture and O2 to assess the ability of the model to generate environmental controls on C and N cycling
The simulated C and N pool sizes, transfer rates and fluxes were compared with six years of continuous measurements to evaluate the capability of the www.geosci-model-dev.net/6/1173/2013/

Summary

Introduction

The CryospherePeatlands represent the largest terrestrial soil C pool and a significant N pool. Peat stores 547 PgC (Yu et al, 2010) and 8 to PgN, accounting for one-third of the terrestrial C and 9 % to % of the soil organic N storage (Wieder and Vitt, 2006). The two characteristic environmental conditions in northern peatlands’ high water table (WT) and low temperature, play an essential role in preserving the large C pool by impeding material translocation and transformation in the permanently saturated zone (Clymo, 1984) the total N storage in peat is substantial, the scarcity of biologically available N induces a conservative manner of N cycling in peatlands (Rosswall and Granhall, 1980; Urban et al, 1988). Sphagnum mosses are highly adapted to the nutrient-poor environment and successfully compete with vascular plants through a series of competition strategies, such as inception of N that is deposited from the atmosphere, internal recycling of N, and a minimized N release from litter with low decomposability (Damman, 1988; Aldous, 2002)

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Conclusion