In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

Kettridge, Nicholas; Baird, Andrew J.

doi:10.1029/2006jf000655

Cited by 23 publications

(24 citation statements)

References 28 publications

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“…Sharratt (1997) measured in situ thermal conductivity in black spruce forests of interior Alaska and reported values for relatively dry moss ranging from 0.03 to 0.09 W m j1 K j1 over the growing season, which are consistent with our measurements at low moisture content (G20% by volume). Minimum K t values measured in this study are also consistent with in situ thermal conductivity measurements of Sphagnum peat by Kettridge and Baird (2007). Our results are also in a good agreement with the estimates of Romanovsky and Osterkamp (2000 ; Table 1) based on interpretation of high-resolution and high-precision temperature measurements from a black spruce forest site in the Bonanza Creek LTER research area (0.1 W m j1 K j1 for the living moss, 0.3 W m j1 K j1 for the dead moss, and 0.5 W m j1 K j1 for the peat layer).…”

Section: Controls On Thermal Conductivity Of Organic Horizonssupporting

confidence: 89%

The Effect of Moisture Content on the Thermal Conductivity of Moss and Organic Soil Horizons From Black Spruce Ecosystems in Interior Alaska

O’Donnell¹,

Romanovsky

Harden³

et al. 2009

Soil Science

160

140

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Organic soil horizons function as important controls on the thermal state of near-surface soil and permafrost in high-latitude ecosystems. The thermal conductivity of organic horizons is typically lower than mineral soils and is closely linked to moisture content, bulk density, and water phase. In this study, we examined the relationship between thermal conductivity and soil moisture for different moss and organic horizon types in black spruce ecosystems of interior Alaska. We sampled organic horizons from feather mossYdominated and Sphagnumdominated stands and divided horizons into live moss and fibrous and amorphous organic matter. Thermal conductivity measurements were made across a range of moisture contents using the transient line heat source method. Our findings indicate a strong positive and linear relationship between thawed thermal conductivity (K t ) and volumetric water content. We observed similar regression parameters (A or slope) across moss types and organic horizons types and small differences in A 0 ( y intercept) across organic horizon types. Live Sphagnum spp. had a higher range of K t than did live feather moss because of the field capacity (laboratory based) of live Sphagnum spp. In northern regions, the thermal properties of organic soil horizons play a critical role in mediating the effects of climate warming on permafrost conditions. Findings from this study could improve model parameterization of thermal properties in organic horizons and enhance our understanding of future permafrost and ecosystem dynamics.

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Section: Controls On Thermal Conductivity Of Organic Horizonssupporting

confidence: 89%

The Effect of Moisture Content on the Thermal Conductivity of Moss and Organic Soil Horizons From Black Spruce Ecosystems in Interior Alaska

O’Donnell¹,

Romanovsky

Harden³

et al. 2009

Soil Science

160

140

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“…The thermal conductivity, including allowance for vapor flux, is calculated from Farouki [1986]: where P is the porosity, θ is the volumetric moisture content, f o is the volumetric fraction of organic matter, and the subscripts a , o and w indicators of air, organic matter and water respectively. Values of k o and k w are assumed to be 0.25 and 0.59 W m 1 K 1 , respectively, and k a combines the conduction and advective vapor component and is given by: The vertical variation in the volumetric heat capacity C (J m 3 K 1 ) is calculated by summing the soil constituents multiplied by their respective heat capacities, with the volumetric moisture content simulated from the preferred capillary rise model presented in Kettridge and Baird [2007].…”

Section: Overview Of Hip Modelmentioning

confidence: 99%

Impact of wildfire on the thermal behavior of northern peatlands: Observations and model simulations

2012

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[1] Wildfire represents the single largest disturbance to the ecohydrological function of northern peatlands. Alterations to peatland thermal behavior as a result of wildfire will modify the carbon balance of these important long-term global carbon stores and regulate post-fire ecosystem recovery. We simulate the 3-D thermal behavior of a peatland that has been disturbed by wildfire to identify how changes in peat temperatures emerge from changes to the surface energy balance and peat thermal properties. Peat temperatures are simulated within two adjacent peatlands, one area having burned 4 years previously, the second which has been wildfire-free for 75 years. We demonstrate that there is only a small alteration to the thermal response in Sphagnum fuscum hummocks that are not severely burnt within the wildfire. In contrast, wildfire produces important changes to the energy balance of Sphagnum hollows. A large reduction in the latent heat flux post-fire increases surface temperatures by up to 30 C during daytime summer conditions. However, temperatures through the peat profile are insensitive to these increases in surface temperature. The low surface moisture content of near-surface peat insulates the profile from these higher temperatures and, at depths below 0.015 m, only small differences are identifiable between burned and unburned hollow temperatures. Nevertheless, we argue that these alterations to near-surface temperatures and evaporation rates likely substantially influence the thermal and hydrological conditions post-wildfire, impacting the peatland recovery.

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“…In the unsaturated zone, water is transported downwards for short periods during and after rainfall events (up to 24 hours; Kettridge & Baird, 2007). During drier periods water is also transported to the Sphagnum surface to supply that lost via evapotranspiration (Yazaki et al , 2006; Kettridge & Baird, 2007). In comparison, in the saturated zone, vertical hydraulic gradients are thought to be minimal in the shallow peat profile simulated in this study.…”

Section: Model Descriptionmentioning

confidence: 99%

“…The vertical variation in the volumetric heat capacity C (J m −3 K −1 ) was simulated from the modified Granberg Model (ModGberg model) described in Kettridge & Baird (2007). Briefly, this model is an empirical representation of the vertical variations in soil water content in Sphagnum peats presented by Hayward & Clymo (1982).…”

Section: Model Descriptionmentioning

confidence: 99%

Modelling soil temperatures in northern peatlands

Kettridge

Baird

2008

European J Soil Science

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Methane emissions from northern peatlands are strongly dependent on soil temperatures. Therefore, to predict methane emissions from northern peatlands under future climatic conditions, it is important to simulate the effect of these changing climatic conditions on peat temperatures. This article reports on the development and testing of two one-dimensional (1D) models used to simulate soil temperatures at shallow depths in a northern peatland. First, the HIP-Dlet (Heat in Peat -Dirichlet) model applies measured temperatures to the surface boundary of a conduction-based temperature model. Secondly, the HIP-Nmann (Heat in Peat -von Neumann) model simulates the surface boundary from standard meteorological measurements. The HIP-Dlet model provides a reasonable to good approximation of measured temperatures showing that heat transport processes within the soil are adequately simulated. The model does not simulate an advective liquid heat flux. However, only substantial rainfall events (> 70 mm over 3 days) during the study period had any significant effect on model error. Errors in the HIPNmann model were of a similar magnitude to the HIP-Dlet model. Errors in the HIP-Dlet model resulted predominantly from errors in the measured soil temperatures. Errors in the HIP-Nmann were due to errors in the measured soil temperatures and the inaccurate simulation of the surface boundary condition. The development of future peatland temperature models should, therefore, focus on the simulation of the surface boundary condition, particularly the parameterisation of the surface resistance that is shown here to produce significant errors in the modelled soil temperatures.

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In situ measurements of the thermal properties of a northern peatland: Implications for peatland temperature models

Cited by 23 publications

References 28 publications

The Effect of Moisture Content on the Thermal Conductivity of Moss and Organic Soil Horizons From Black Spruce Ecosystems in Interior Alaska

The Effect of Moisture Content on the Thermal Conductivity of Moss and Organic Soil Horizons From Black Spruce Ecosystems in Interior Alaska

Impact of wildfire on the thermal behavior of northern peatlands: Observations and model simulations

Modelling soil temperatures in northern peatlands

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