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Stith T. Gower - One of the best experts on this subject based on the ideXlab platform.
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Soil Surface CO2 flux in a boreal black spruce fire chronosequence
Journal of Geophysical Research, 2002Co-Authors: Chuankuan Wang, Ben Bond-lamberty, Stith T. GowerAbstract:[1] Understanding the effects of wildfire on the carbon (C) cycle of boreal forests is essential to quantifying the role of boreal forests in the global carbon cycle. Soil Surface CO2 flux (Rs), the second largest C flux in boreal forests, is directly and indirectly affected by fire and is hypothesized to change during forest succession following fire. The overall objective of this study was to measure and model Rs for a black spruce (Picea mariana [Mill.] BSP) postfire chronosequence in northern Manitoba, Canada. The experiment design was a nested factorial that included two Soil drainage classes (well and poorly drained) × seven postfire aged stands. Specific objectives were (1) to quantify the relationship between Rs and Soil temperature for different aged boreal black spruce forests in well-drained and poorly drained Soil conditions, (2) to examine Rs dynamics along postfire successional stands, and (3) to estimate annual Soil Surface CO2 flux for these ecosystems. Soil Surface CO2 flux was significantly affected by Soil drainage class (p = 0.014) and stand age (p = 0.006). Soil Surface CO2 flux was positively correlated to Soil temperature (R2 = 0.78, p < 0.001), but different models were required for each drainage class × aged stand combination. Soil Surface CO2 flux was significantly greater at the well-drained than the poorly drained stands (p = 0.007) during growing season. Annual Soil Surface CO2 flux for the 1998, 1995, 1989, 1981, 1964, 1930, and 1870 burned stands averaged 226, 412, 357, 413, 350, 274, and 244 g C m-2 yr−1 in the well-drained stands and 146, 380, 300, 303, 256, 233, and 264 g C m−2 yr−1 in the poorly drained stands. Soil Surface CO2 flux during the winter (from 1 November to 30 April) comprised from 5 to 19% of the total annual Rs. We speculate that the smaller Soil Surface CO2 flux in the recently burned than the older stands is mainly caused by decreased root respiration.
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a comparison of six methods for measuring Soil Surface carbon dioxide fluxes
Journal of Geophysical Research, 1997Co-Authors: John M. Norman, Stith T. Gower, Christopher J. Kucharik, Dennis D. Baldocchi, M. Rayment, Kathleen Savage, Patrick M Crill, Robert G. StrieglAbstract:Measurements of Soil-Surface CO2 fluxes are important for characterizing the carbon budget of boreal forests because these fluxes can be the second largest component of the budget. Several methods for measuring Soil-Surface CO2 fluxes are available: (1) closed-dynamic-chamber systems, (2) closed-static-chamber systems, (3) open-chamber systems, and (4) eddy covariance systems. This paper presents a field comparison of six individual systems for measuring Soil-Surface CO2 fluxes with each of the four basic system types represented. A single system is used as a reference and compared to each of the other systems individually in black spruce (Picea mariana), jack pine (Pinus banksiana), or aspen (Populus tremuloides) forests. Fluxes vary from 1 to 10 μmol CO2 m−2 s−1. Adjustment factors to bring all of the systems into agreement vary from 0.93 to 1.45 with an uncertainty of about 10–15%.
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A comparison of six methods for measuring Soil-Surface carbon
1997Co-Authors: John M. Norman, Stith T. Gower, Christopher J. Kucharik, Dennis D. Baldocchi, M. Rayment, Kathleen Savage, Robert G. StrieglAbstract:Measurements of Soil-Surface CO2 fluxes are important for characterizing the carbon budget of boreal forests because these fluxes can be the second largest component of the budget. Several methods for measuring Soil-Surface CO2 fluxes are available' (1) closed-dynamic-chamber systems, (2) closed-static-chamber systems, (3) open-chamber systems, and (4) eddy covariance systems. This paper presents a field comparison of six individual systems for measuring Soil-Surface CO2 fluxes with each of the four basic system types represented. A single system is used as a reference and compared to each of the other systems individually in black spruce (Picea mariana), jack pine (Pinus banksiana), or aspen (Populus tremuloides) forests. Fluxes vary from 1 to 10/mol CO2 m -2 s -. Adjustment factors to bring all of the systems into agreement vary from 0.93 to 1.45 with an uncertainty of about 10-15%.
Keith L. Bristow - One of the best experts on this subject based on the ideXlab platform.
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Soil Surface heat flux: some general questions and comments on measurements
Agricultural and Forest Meteorology, 1995Co-Authors: C.l. Mayocchi, Keith L. BristowAbstract:Abstract Soil Surface heat flux is often measured incorrectly owing to a lack of understanding of the processes occurring at the Soil Surface. To determine accurately Soil Surface heat flux from measurements of heat flux at some depth below the Surface, both heat storage above the plate and latent heat loss from below the plate must be taken into account. Large errors can be introduced if heat storage is neglected, and even larger errors can be found if latent heat processes are ignored. In this paper we describe a general framework for the correct interpretation of field measurements of Soil heat flux.
S. B. Verma - One of the best experts on this subject based on the ideXlab platform.
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Soil Surface CO2 fluxes and the carbon budget of a grassland
Journal of Geophysical Research, 1992Co-Authors: J. M. Norman, R. Garcia, S. B. VermaAbstract:Measurements of Soil Surface CO2 fluxes are reported for three sites within the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) area, and simple empirical equations are fit to the data to provide predictions of Soil fluxes from environmental observations. A prototype Soil chamber, used to make the flux measurements, is described and tested by comparing CO2 flux measurements to a 40-L chamber, a 1-m3 chamber, and eddy correlation. Results suggest that flux measurements with the prototype chamber are consistent with measurements by other methods to within about 20%. A simple empirical equation based on 10-cm Soil temperature, 0- to 10-cm Soil volumetric water content, and leaf area index predicts the Soil Surface CO2 flux with a root-mean-square (rms) error of 1.2 μmol m−2 s−1 for all three sites. Further evidence supports using this equation to evaluate Soil Surface CO2 during the 1987 FIFE experiment. The Soil Surface CO2 fluxes when averaged over 24 hours are comparable to daily gross canopy photosynthetic rates. For 6 days of data the net daily accumulation of carbon is about 0.6 g CO2 m−2 d−1; this is only a few percent of the daily gross accumulation of carbon by photosynthesis. As the Soil became drier in 1989, the net accumulation of carbon by the prairie increased, suggesting that the Soil flux is more sensitive to temperature and drought than the photosynthetic fluxes.
Heping Liu - One of the best experts on this subject based on the ideXlab platform.
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impact of wave phase difference between Soil Surface heat flux and Soil Surface temperature on Soil Surface energy balance closure
Journal of Geophysical Research, 2010Co-Authors: Zhiqiu Gao, Robert Horton, Heping LiuAbstract:[1] The sensitivity of climate simulations to diurnal variation in the Surface energy budget encourages enhanced inspection into the energy balance closure failure encountered in micrometeorological experiments. The diurnal wave phases of Soil Surface heat flux and temperature are theoretically characterized and compared for both moist Soil and absolutely dry Soil Surfaces, indicating that the diurnal wave phase difference between Soil Surface heat flux and temperature ranges from 0 to π/4 for natural Soils. Assuming that the net radiation and turbulent heat fluxes have phases identical to that of the Soil Surface temperature, we evaluate potential contributions of the wave phase difference to the Surface energy balance closure. Results show that the sum of sensible heat flux and latent heat flux is always less than the available Surface energy (i.e., the difference between net radiation and Soil Surface heat flux) even if all energy components are accurately measured, their footprints are strictly matched, and all corrections related to measurement environments and techniques are made. The energy balance closure ratio is extremely sensitive to the ratio of Soil Surface heat flux amplitude (A4) to net radiation flux amplitude (A1), and a high value of A4/A1 causes a significant failure in Surface energy balance closure. An experimental case study confirms the theoretical analysis.
C.l. Mayocchi - One of the best experts on this subject based on the ideXlab platform.
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Soil Surface heat flux: some general questions and comments on measurements
Agricultural and Forest Meteorology, 1995Co-Authors: C.l. Mayocchi, Keith L. BristowAbstract:Abstract Soil Surface heat flux is often measured incorrectly owing to a lack of understanding of the processes occurring at the Soil Surface. To determine accurately Soil Surface heat flux from measurements of heat flux at some depth below the Surface, both heat storage above the plate and latent heat loss from below the plate must be taken into account. Large errors can be introduced if heat storage is neglected, and even larger errors can be found if latent heat processes are ignored. In this paper we describe a general framework for the correct interpretation of field measurements of Soil heat flux.
