Search

Boreal and arctic regions are predicted to warm faster and more strongly than temperate latitudes. Peatlands in these regions contain large stocks of soil carbon in frozen soil and these may effect a strong positive feedback on climate change. We modelled the predicted effects of climate change and wildfire on permafrost in organic soils using a peatland-specific soil thermal model to simulate soil temperatures. We evaluated the model at a lowland black spruce site in Alaska and a sedge-dominated Canadian arctic fen. We estimated the response of soil temperatures and the active layer thickness (AcLTh) under several climate change scenarios. With surface soil temperatures increased by 4.4 °C-5.4 °C, soil temperatures at 100 cm depth increased by 3.6 °C-4.3 °C, the AcLTh increased by 12-30 cm, the zone of partially thawed soil increased, and the number of thaw days increased by 17-26 %. Wildfire caused AcLTh to increase by 26-48 % in the year following fire; AcLTh differences in 2091-2100 were significant (8 cm) at one site. By 2100, climate change effects on AcLTh were larger than wildfire effects suggesting that persistent temperature increases will have a more substantial effect on permafrost than the transient effects of disturbance. [ABSTRACT FROM AUTHOR]

The article presents a study on the Holocene Peat Model (HPM), a simulation model designed to determine peat accumulation tested at a temperate bog in Ontario. It states that the HPM was made and evaluated considering factors such as hydrology, peat properties and the nature of plant communities. It adds that peat decomposition and dynamic peat accumulation models were combined in HPM. Moreover, it asserts that the HPM is capable of demonstrating balances in peatland carbon and watecycles.

We applied an inverse model to simulate global carbon (C) cycle dynamics during the Holocene period using atmospheric carbon dioxide (CO2) concentrations reconstructed from Antarctic ice cores and prescribed C accumulation rates of Northern Peatlands (NP) as inputs. Previous studies indicated that different sources could contribute to the 20 parts per million by volume (ppmv) atmospheric CO2 increase over the past 8000 years. These sources of C include terrestrial release of 40-200 petagram C (PgC, 1 petagram=1015 gram), deep oceanic adjustment to a 500 PgC terrestrial biomass buildup early in this interglacial period, and anthropogenic land-use and land-cover changes of unknown magnitudes. Our study shows that the prescribed peatland C accumulation significantly modifies our previous understanding of Holocene C cycle dynamics. If the buildup of the NP is considered, the terrestrial pool becomes the C sink of about 160-280 PgC over the past 8000 years, and the only C source for the terrestrial and atmospheric C increases is presumably from the deep ocean due to calcium carbonate compensation. Future studies need to be conducted to constrain the basal times and growth rates of the NP C accumulation in the Holocene. These research endeavors are challenging because they need a dynamically-coupled peatland simulator to be constrained with the initiation time and reconstructed C reservoir of the NP. Our results also suggest that the huge reservoir of deep ocean C explains the major variability of the glacial-interglacial C cycle dynamics without considering the anthropogenic C perturbation. [ABSTRACT FROM AUTHOR]

We developed the McGill Wetland Model (MWM) based on the general structure of the Peatland Carbon Simulator (PCARS) and the Canadian Terrestrial Ecosystem Model. Three major changes were made to PCARS: the light use efficiency model of photosynthesis was replaced with a biogeochemical description of photosynthesis; 2. the description of autotrophic respiration was changed to be consistent with the formulation of photosynthesis; and 3. the cohort, multilayer soil respiration model was changed to a simple one box peat decomposition model divided into an oxic and anoxic zones by an effective water table, and a one-year residence time litter pool. MWM was then evaluated by comparing its output to the estimates of net ecosystem production (NEP), gross primary production (GPP) and ecosystem respiration (ER) from years of continuous measurements at the Mer Bleue peatland, a raised ombrotrophic bog located in southern Ontario, Canada (index of agreement [dimensionless]: NEP=0.80, GPP=0.97, ER=0.97; systematic RMSE [g C m-2 d-1]: NEP=0.12, GPP=0.07, ER=0.14; unsystematic RMSE [g C m-2 d-1]: NEP=0.15, GPP=0.27, ER=0.23). Simulated moss NPP approximates what would be expected for a bog peatland, but shrub NPP appears to be underestimated. Sensitivity analysis revealed that the model output did not change greatly due to variations in water table because of offsetting responses in production and respiration, but that even modest temperature increases could lead to converting the bog from a sink to a source of CO2. General weaknesses and further developments of MWM are discussed. [ABSTRACT FROM AUTHOR]