244
path fourier-transform infrared spectrometry (e.g.,
Gosz et al. 1988) and tunable diode lasers (e.g.,
Zahniser et al. 1995) have also been developed for
field measurements of gases and are being used in
conjunction with eddy correlation and other flux
estimate approaches for estimates of emissions of
CH4, N20, and other gases.
Multiple Approaches
for Understanding
and Estimating Fluxes
In the earlier days of trace gas studies, it was typical
to study only one trace gas at a time and to use a
single measurement approach. As the interdisciplinary science of biosphere-atmosphere interactions
continues to mature, many investigators are evaluating fluxes of different gases in a single study, having found that knowledge of the dynamics of several gases offers insights into the functioning of the
system and the factors controlling the emission of
each gas. For example, N20 (a nonreactive greenhouse gas) and NOx (a very chemically reactive gas
involved in air pollution) were rarely studied together in the field until around 1990, despite the
fact that they are produced by the same microbial
processes in soil. Now, studies that evaluate the
fluxes of both gases (which requires the use of two
different analytical systems) are commonly done
and are providing insight into the role of microbial
processes and soil physical characteristics such as
water-filled pore space in controlling production
and emission from soils to the atmosphere (e.g.,
Davidson 1992; Davidson 1993; Davidson et al.
1993; Matson et al. 1996; Matson et al. 1998).
Moreover, studies of N gas exchanges today are
typically accompanied by studies of microbial dynamics as well as edaphic and environmental characteristics. Similarly, N 2 0 and CH4 emissions were
typically studied by different groups in different
ecosystems for different reasons, until researchers
realized that the inverse relationship between the
two gases in some ecosystems provides insight into
the processes responsible for flux, and also suggests
the potential for tradeoff in the gas emissions under
different management practices and environmental
changes (Mosier et al. 1991; Keller et al. 1986;
Steudler et al. 1989).
Pamela Matson and Allen Goldstein
Beginning in the late 1980s, a series of multidiscipline, multiapproach studies have evaluated trace
gas exchange between terrestrial and aquatic ecosystems and the atmosphere, with an eye to not just
estimating fluxes but also understanding the factors
that lead to variability in fluxes across broad
regions. The Amazon Boundary Layer Experiments
(ABLE-2A and B) first attempted to integrate
ground-based, tower-based, and aircraft-based
measurements of gas flux (Harriss et al. 1988,
1990). The Arctic Boundary Layer Experiments
(ABLE-3A and B) took this integration a step further, coordinating ecosystem characterization,
enclosure-based measurements of CH4 and other
gas fluxes, and eddy correlation estimates of CH 4
flux on towers and aircraft (Harriss et al. 1992),
ultimately allowing comparison of the measurement approaches across the different scales (Bartlett and Harriss 1993). More recently, studies such
as BOREAS have expanded the concept to include
multiple tower sites with accompanying groundbased soil, vegetation, and chamber measurements,
and multiple aircraft systems for sensing fluxes at
different scales (Sellers et al. 1995, Margolis and
Ryan 1997).
Such massive efforts present wonderful opportunities for biogenic trace gas researchers. However, approaches that include measurements of
multiple gases using a variety of techniques are becoming the norm for individual researchers or small
teams of scientists as well. Moreover, studies that
include not only trace gas measurements but evaluation of water, nutrient, and meteorological dynamics (described in many of the other chapters of
this book) will ultimately improve our ability to
develop and use ecosystem models that estimate
trace gas flux (see Chapter 25), and to extrapolate
our knowledge to regional and global scales (see
Chapter 18).
References
Ambus, P.; Robertson, G.P. Automated near-continuous
measurement of carbon dioxide and nitrous oxide
fluxes from Soil. Soil Sci. Soc. Am. 62:394-400;
1998.
Aneja, V.P.; Cooper, W.J. Biogenic sulfur emissions: A
review. In: Saltzman E.S.; Cooper W.J., eds. Biogenic
Sulfur in the Environment. Washington, DC: American
Chemical Society; 1989:2-13.
path fourier-transform infrared spectrometry (e.g.,
Gosz et al. 1988) and tunable diode lasers (e.g.,
Zahniser et al. 1995) have also been developed for
field measurements of gases and are being used in
conjunction with eddy correlation and other flux
estimate approaches for estimates of emissions of
CH4, N20, and other gases.
Multiple Approaches
for Understanding
and Estimating Fluxes
In the earlier days of trace gas studies, it was typical
to study only one trace gas at a time and to use a
single measurement approach. As the interdisciplinary science of biosphere-atmosphere interactions
continues to mature, many investigators are evaluating fluxes of different gases in a single study, having found that knowledge of the dynamics of several gases offers insights into the functioning of the
system and the factors controlling the emission of
each gas. For example, N20 (a nonreactive greenhouse gas) and NOx (a very chemically reactive gas
involved in air pollution) were rarely studied together in the field until around 1990, despite the
fact that they are produced by the same microbial
processes in soil. Now, studies that evaluate the
fluxes of both gases (which requires the use of two
different analytical systems) are commonly done
and are providing insight into the role of microbial
processes and soil physical characteristics such as
water-filled pore space in controlling production
and emission from soils to the atmosphere (e.g.,
Davidson 1992; Davidson 1993; Davidson et al.
1993; Matson et al. 1996; Matson et al. 1998).
Moreover, studies of N gas exchanges today are
typically accompanied by studies of microbial dynamics as well as edaphic and environmental characteristics. Similarly, N 2 0 and CH4 emissions were
typically studied by different groups in different
ecosystems for different reasons, until researchers
realized that the inverse relationship between the
two gases in some ecosystems provides insight into
the processes responsible for flux, and also suggests
the potential for tradeoff in the gas emissions under
different management practices and environmental
changes (Mosier et al. 1991; Keller et al. 1986;
Steudler et al. 1989).
Pamela Matson and Allen Goldstein
Beginning in the late 1980s, a series of multidiscipline, multiapproach studies have evaluated trace
gas exchange between terrestrial and aquatic ecosystems and the atmosphere, with an eye to not just
estimating fluxes but also understanding the factors
that lead to variability in fluxes across broad
regions. The Amazon Boundary Layer Experiments
(ABLE-2A and B) first attempted to integrate
ground-based, tower-based, and aircraft-based
measurements of gas flux (Harriss et al. 1988,
1990). The Arctic Boundary Layer Experiments
(ABLE-3A and B) took this integration a step further, coordinating ecosystem characterization,
enclosure-based measurements of CH4 and other
gas fluxes, and eddy correlation estimates of CH 4
flux on towers and aircraft (Harriss et al. 1992),
ultimately allowing comparison of the measurement approaches across the different scales (Bartlett and Harriss 1993). More recently, studies such
as BOREAS have expanded the concept to include
multiple tower sites with accompanying groundbased soil, vegetation, and chamber measurements,
and multiple aircraft systems for sensing fluxes at
different scales (Sellers et al. 1995, Margolis and
Ryan 1997).
Such massive efforts present wonderful opportunities for biogenic trace gas researchers. However, approaches that include measurements of
multiple gases using a variety of techniques are becoming the norm for individual researchers or small
teams of scientists as well. Moreover, studies that
include not only trace gas measurements but evaluation of water, nutrient, and meteorological dynamics (described in many of the other chapters of
this book) will ultimately improve our ability to
develop and use ecosystem models that estimate
trace gas flux (see Chapter 25), and to extrapolate
our knowledge to regional and global scales (see
Chapter 18).
References
Ambus, P.; Robertson, G.P. Automated near-continuous
measurement of carbon dioxide and nitrous oxide
fluxes from Soil. Soil Sci. Soc. Am. 62:394-400;
1998.
Aneja, V.P.; Cooper, W.J. Biogenic sulfur emissions: A
review. In: Saltzman E.S.; Cooper W.J., eds. Biogenic
Sulfur in the Environment. Washington, DC: American
Chemical Society; 1989:2-13.