Methane and Carbon Dioxide Cycling in Soils of the Harvard Forest

Methane and Carbon Dioxide Cycling in Soils of the Harvard Forest
Author: Alexa Jaeger
Publisher:
Total Pages: 18
Release: 2018
Genre:
ISBN:

Soil is Earth's largest terrestrial carbon pool (Oertel et al., 2016) and can act as a net source of greenhouse gases (GHG). However, if organic material accumulates in soils faster than it is converted to CO2 by cellular respiration, soil becomes a smaller GHG source and even has the potential to become a GHG sink. Not much is known about factors that drive soil to be a source or a sink of GHG. Soil temperature and moisture have both been shown to correlate with CH4 emissions and temperature has been shown to correlate with CO 2 emissions (Jacinthe et al., 2015). Currently these relationships are not well constrained, particularly in upland soils, which are soils found at elevations between 100 and 500 m (Carating et al., 2014). Soil from the Harvard Forest was collected and used in two in-lab flux experiments to constrain the effect that soil moisture has on i.) the rate of CH4 and CO2 production/consumption and ii.) the fraction of injected CH4 that is oxidized to CO2 by soil microbes. The first experiment involved injecting vials containing soil samples with CH4 , taking an initial measurement with a residual gas analyzer (RGA), incubating for three days, and taking final measurements using the RGA. The results of this experiment indicated that cellular respiration is an important carbon source in these soils, with more CO2 coming from cellular respiration than from the oxidation of CH4. The second experiment involved injecting vials containing soil samples with CH4 and 14CH4 as a tracer, incubating for six days, and analyzing CO2 from each sample using a scintillation counter. This experiment showed a weak trend indicating that increased soil moisture may result in decreased CH4 oxidation. Results showed that decays per minute from the samples were lower than in a control. These results indicated that not all CO 2 from each sample was successfully captured and analyzed using the methods here. So while the trend may hold true, it should be supported by reconducting the experiment using a more reliable means of CO2 capture. The unexpected results from both experiments indicated that there is still much to be learned about the reactions that occur in these soils and how to perfect laboratory methods to study them.

High Frequency Measurements of Soil Carbon Dioxide Flux at Harvard Forest

High Frequency Measurements of Soil Carbon Dioxide Flux at Harvard Forest
Author: Stephen C. Phillips
Publisher:
Total Pages: 85
Release: 2007
Genre:
ISBN: 9781109823127

Soil carbon dioxide flux was measured by automatic chambers at Harvard Forest over a four-year period, 2003-2006. The autochambers were installed along a moisture gradient from upland to wetland soils. In 2003, fluxes from the upland and mid-slope chambers exceeded the fluxes from the wetland margin. In 2004-2006, the mid-slope fluxes were significantly larger than both the upland and wetland margin chambers. The differences in flux between chamber location were most pronounced in the late summer and early fall. Residuals from a non-linear temperature regression exhibit a distinct seasonal pattern in 2003, 2004, and 2006, but not in 2005. On short time scales, the residuals are correlated with soil moisture, responding to precipitation events. The seasonal pattern of soil flux reaches a maximum later in the year than ecosystem respiration measured at the eddy covariance flux tower.

Analysis of Carbon Dioxide and Methane Cycling in Forest Soils Using Stable Carbon Isotopes

Analysis of Carbon Dioxide and Methane Cycling in Forest Soils Using Stable Carbon Isotopes
Author:
Publisher:
Total Pages:
Release: 2008
Genre:
ISBN:

Understanding the role of forests in the cycling of methane (CH4) and carbon dioxide (CO2) is of importance to the elucidation of global greenhouse gas budgets. Previous studies have shown aerated forests soils to be net sinks of atmospheric CH4 and sources of carbon dioxide. While much research has focused on the role of forest soils as CO2 sources and CH4 sinks, few studies have utilized 13C-isotope studies to clarify the nature of subsurface CO2 production and CH4 consumption. The present study, carried out in 3 temperate forest environments on Vancouver Island during 2006 and 2007, and a boreal forest in northern Quebec in 2005, is intended to address this paucity of information. The isotope and concentration data corroborates previous studies in suggesting that both temperate and boreal forest environments act as net CH4 sinks and CO2 sources. No clear evidence of methanogenesis is apparent in either Vancouver Island or northern Quebec, where the isotopic composition of subsurface CH4 is influenced by diffusive and biological fractionation. Near-surface photosynthetic uptake may have a strong influence on the isotopic composition of soil CO2 and the resultant fluxes, acting to reduce apparent fluxes due to CO2 consumption. Intra-site variability of CH4 and CO2 fluxes indicates that the use of two static chambers in a single site, while sufficient for the confirmation of gas uptake or emission, may be less adequate in the determination of actual rates of efflux/influx. Future studies should address this by either sampling a larger area, installing a greater number of chambers, or by utilizing entirely different methods, such as the use of eddy covariance techniques.

Analysis of Carbon Dioxide and Methane Cycling in Forest Soils Using Stable Carbon Isotopes

Analysis of Carbon Dioxide and Methane Cycling in Forest Soils Using Stable Carbon Isotopes
Author: Kern Young Lee
Publisher:
Total Pages:
Release: 2008
Genre:
ISBN:

Understanding the role of forests in the cycling of methane (CH4) and carbon dioxide (CO2) is of importance to the elucidation of global greenhouse gas budgets. Previous studies have shown aerated forests soils to be net sinks of atmospheric CH4 and sources of carbon dioxide. While much research has focused on the role of forest soils as CO2 sources and CH4 sinks, few studies have utilized 13C-isotope studies to clarify the nature of subsurface CO2 production and CH4 consumption. The present study, carried out in 3 temperate forest environments on Vancouver Island during 2006 and 2007, and a boreal forest in northern Quebec in 2005, is intended to address this paucity of information. The isotope and concentration data corroborates previous studies in suggesting that both temperate and boreal forest environments act as net CH4 sinks and CO2 sources. No clear evidence of methanogenesis is apparent in either Vancouver Island or northern Quebec, where the isotopic composition of subsurface CH4 is influenced by diffusive and biological fractionation. Near-surface photosynthetic uptake may have a strong influence on the isotopic composition of soil CO2 and the resultant fluxes, acting to reduce apparent fluxes due to CO2 consumption. Intra-site variability of CH4 and CO2 fluxes indicates that the use of two static chambers in a single site, while sufficient for the confirmation of gas uptake or emission, may be less adequate in the determination of actual rates of efflux/influx. Future studies should address this by either sampling a larger area, installing a greater number of chambers, or by utilizing entirely different methods, such as the use of eddy covariance techniques.

The Harvard Forest

The Harvard Forest
Author: Harvard Forest (Research facility)
Publisher:
Total Pages: 440
Release: 1989
Genre: Forests and forestry
ISBN:

Fire, Climate Change, and Carbon Cycling in the Boreal Forest

Fire, Climate Change, and Carbon Cycling in the Boreal Forest
Author: Eric S. Kasischke
Publisher: Springer Science & Business Media
Total Pages: 490
Release: 2012-08-22
Genre: Science
ISBN: 0387216294

A discussion of the direct and indirect mechanisms by which fire and climate interact to influence carbon cycling in North American boreal forests. The first section summarizes the information needed to understand and manage fires' effects on the ecology of boreal forests and its influence on global climate change issues. Following chapters discuss in detail the role of fire in the ecology of boreal forests, present data sets on fire and the distribution of carbon, and treat the use of satellite imagery in monitoring these regions as well as approaches to modeling the relevant processes.

Greenhouse Gas Sinks

Greenhouse Gas Sinks
Author: Dave Reay
Publisher: CABI
Total Pages: 306
Release: 2007
Genre: Science
ISBN: 1845931890

In this first comprehensive handbook of the earth's sinks for greenhouse gases, leading researchers from around the world provide an expert synthesis of current understanding and uncertainties. It will be a valuable resource for students, researchers and practitioners in conservation, ecology and environmental studies.