BGBiogeosciencesBGBiogeosciences1726-4189Copernicus PublicationsGöttingen, Germany10.5194/bg-15-349-2018Preface: OzFlux: a network for the study of ecosystem carbon and water dynamics
across Australia and New ZealandPreface: OzFluxvan GorselEvaeva.vangorsel@anu.edu.auCleverlyJameshttps://orcid.org/0000-0002-2731-7150BeringerJasonhttps://orcid.org/0000-0002-4619-8361CleughHelenEamusDerekhttps://orcid.org/0000-0003-2765-8040HutleyLindsay B.https://orcid.org/0000-0001-5533-9886IsaacPeterProberSuzanneFenner School of Environment and Society, The Australian National
University, ACT, Canberra, AustraliaSchool of Life Sciences, University of Technology Sydney, Broadway,
NSW, 2007, AustraliaThe UWA School of Agriculture and Environment, The University of
Western Australia, Crawley, WA, 6020, AustraliaCSIRO Climate Science Centre, Canberra, 2601, AustraliaResearch Institute for the Environment and Livelihoods, Charles
Darwin University, Darwin, NT 0909 AustraliaOzFlux, Melbourne, VIC 3159, AustraliaCSIRO Land and Water, Floreat, 6913, AustraliaEva van Gorsel (eva.vangorsel@anu.edu.au)16January2018151349352This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/This article is available from https://bg.copernicus.org/articles/15/349/2018/bg-15-349-2018.htmlThe full text article is available as a PDF file from https://bg.copernicus.org/articles/15/349/2018/bg-15-349-2018.pdf
This special issue of Biogeosciences synthesises and interprets the
research outputs and results from OzFlux, the Australian and New Zealand Flux
Network. The OzFlux community dedicates this special issue to Dr Ray Leuning,
who made profound and significant contributions to our knowledge of
land–vegetation–atmosphere interactions and generously offered his thoughtful
consideration to students and early career researchers globally. His
dedication to teaching was expressed through direct interactions, as a
regular lecturer in the flux course in the USA, and the annual data workshops
that he originally organised for OzFlux and that continue in his honour.
Ray personally visited many potential sites for the OzFlux network across
Australia and New Zealand, where his insight ensured that best practice and
fit-for-purpose measurement methods were used that were appropriate for each
location's unique situation. Ray, with colleagues, founded OzFlux in 2001
(Beringer et al., 2016) and
continued to guide OzFlux as it grew its depth of understanding and grew in
size, scope and impact. Ray's vision of interdisciplinary science was
realised when OzFlux was supported via the Australian government's National
Collaborative Infrastructure Scheme's funding to the Terrestrial Ecosystem
Research Network (TERN) in 2009.
Carbon is naturally circulated between the atmosphere, ocean and terrestrial
biosphere on timescales ranging from sub-daily to millennia. Exchanges with
geologic pools occur on even longer timescales. In addition to this natural
carbon cycle, anthropogenic emissions occur predominantly through land-use
change and fossil fuel emissions (Achard et al., 2014). The Earth's natural
carbon sinks (oceans and terrestrial) continue to remove about half of the
global emissions of carbon dioxide that are released via human activity into
the atmosphere (Jones et al., 2016). As a result of these processes,
atmospheric CO2 concentrations have increased from about 277 ppmv in
1750 to > 400 ppmv in November 2015 (Le Quéré et al., 2016, and
citations therein). Terrestrial ecosystems have been taking up increasing
amounts of CO2 albeit with a sink strength that varies greatly between
years, especially in the semi-arid and savanna vegetation of Australia
(Poulter et al., 2014; Trudinger et al., 2016). Likewise, dry temperate
eucalypt forests can be a very large sink for carbon (Hinko-Najera et al.,
2017; Leuning et al., 2005), although these highly productive ecosystems can
become a carbon source due to the direct and indirect effects of climate
variability (van Gorsel et al., 2013). Bristow et al. (2016) show in this
special issue that clearing of woody vegetation from the tropical savanna
results in carbon emissions double the size of that reported for savanna
burning. Rainfall is an important driver of photosynthesis in Australian
ecosystems, and fluctuations of rainfall and productivity in Australia have
been associated with multiple climate indices (Cleverly et al., 2016; Rogers
and Beringer, 2017). Australia's climate has always been characterised by
extreme, high-impact weather events such as cyclones, storms, fire weather
and heatwaves. The “Angry Summer” heatwave of 2012–2013 (Climate Council,
2014) reflected the resilience of Australian vegetation (Ma et al., 2016),
although that resilience is being tested as longer droughts, more severe
heatwaves and strengthened land–climate feedbacks increase in frequency and
intensity due to climate change (van Gorsel et al., 2016). Like extreme
weather, fire has a transformative impact on Australian ecosystems and the
carbon cycle (Beringer et al., 2016; Whitley et al., 2017). The carbon cycle is intrinsically linked to the water
cycle and no more so than in Australia, “a land of drought and flooding
rains” (Dorothea Mackellar,
http://www.dorotheamackellar.com.au/archive/mycountry.htm). The strong
influence of water availability on net carbon fluxes in Australian landscapes
provides an important constraint on plans to reduce Australia's greenhouse
gas emissions using land management practices.
A more detailed understanding of the dynamic soil–plant–atmosphere continuum
is critical to explain and predict past and future trends and variability in
the terrestrial carbon and water cycles, and this knowledge is required by
resource managers and policymakers seeking to manage carbon and water
resources. Differential allocation of resources (i.e. water, carbon, light)
between roots and shoots by grasses compared to trees supports the hypothesis
that tree cover in the Australian savanna is determined primarily by resource
limitation (Haverd et al., 2016). Root water uptake is a key determinant of
observed differences in the behaviour of C3 woody and C4 grass
components of savanna ecosystems (Whitley et al., 2016). Contrasting patterns
of root water uptake result in seasonal variations in phenology on canopy,
understory and ecosystem scales, with consequential effects on photosynthetic
production (Moore et al., 2016a; Whitley et al., 2017). Trees and grasses
have been shown to have distinct light-use efficiencies, which affects
photosynthesis and enables gross primary production (Moore et al., 2017) to
be tracked and inferred from phenocam networks on the ground or from space
for some ecosystems (Moore et al., 2016b). Restrepo-Coupe et al. (2016)
showed in this special issue that satellite-based, remotely sensed data are
more strongly related to the photosynthetic potential of ecosystems than to
actual photosynthesis, and that these data can be used for large-scale
estimation of photosynthetic production across the Australian continent.
Natural fluxes must be measured to better understand land–climate
interactions, feedbacks and climate regulation. Flux networks are integrated
through their common infrastructure and data (Isaac et al., 2017). Research
advances by the OzFlux community have led to improved, process-oriented
application of gap-filling and partitioning of carbon fluxes between gross
primary production and ecosystem respiration (Beringer et al., 2017; Isaac et
al., 2017; McHugh et al., 2017). In this special issue, OzFlux has also
contributed to our understanding of micrometeorological methods for
measurements of trace gases (for example methane and N2O) over grazed
pasture in New Zealand (Laubach et al., 2016). Hunt et al. (2016) find that
intensive pasture management with irrigation does not necessarily lead to
carbon losses under the pasture; provided that the carbon in cattle excreta
is returned to the pasture, even gains are possible. Soil in Australian
temperate forests is a consistent sink for methane, showing little response
to temperature and driven largely by variations in soil moisture content and,
conversely, air-filled porosity (Fest et al., 2017). These studies are made
possible by networks of flux towers using the eddy covariance method,
contributing to an improved process-based understanding that is central to
the building of models and their verification. Regional networks like OzFlux
further contribute to integration of these data and findings across a global
network, FLUXNET, which has operated since 1997 (Baldocchi et al., 2001) and
continues at hundreds of research sites around the world.
This special issue reflects the breadth of scientific research to which Ray
made significant contributions, including (i) methodological aspects of
observations and their interpretation (Beringer et al., 2017; Isaac et al.,
2017; McHugh et al., 2017); (ii) upscaling ecosystem-scale measurements to
regional and larger scales using remote sensing and physical modelling
(Haverd et al., 2016; Laubach et al., 2016; Moore et al., 2016b;
Restrepo-Coupe et al., 2016; Trudinger et al., 2016; Whitley et al., 2016);
and (iii) analysis of carbon, water and energy cycles in response to land use
and climate change, extreme weather, and fire (Bristow et al., 2016;
Hinko-Najera et al., 2017; Hunt et al., 2016; Moore et al., 2016a, 2017; van
Gorsel et al., 2016; Fest et al., 2017). Ray's approach to science was to
always capture process understanding and integrate this into models that
could be used to deliver predictions and solutions. An in-depth overview of
Ray's scientific achievements is given in Cleugh (2013). We remember him well
for his quotes, often given with a sincerity that showed his unshakable moral
centre: “Work not published is work not done” (we have a responsibility to
give back to society); “Don't publish ephemera” (put forth your best effort
to answer important questions); “What is your hypothesis?” (only when we
are testing hypotheses are we engaging with the scientific method); “Know
thy site” (go out there, experience, learn and understand how the ecosystem
and the instrumentation work); “Health warning: this lecture contains
equations” (because sometimes they are required for proper understanding);
and “Beat the drum” and “Ring your bell” (let others know what
important discoveries you have made).
Ray made an enormous contribution to science, and his research will have an
enduring impact as evidenced by a large and increasing number of citations
and the use of his work in textbooks. His work will also continue through
the many colleagues, postdoctoral researchers and postgraduate students
with whom he has generously shared his knowledge. Not only has he taught in
many summer schools and courses around the world, but many of us
experienced how Ray would simply take a day out of his very busy work life to
discuss a scientific problem. He would give support all the way through, from
rigorously answering the scientific question to publishing the answers in a
peer-reviewed publication. Ray had an impeccably high standard that he also
expected of the community and this has held the community in good stead
through rigorous publications. He always insisted on getting the best value
out of the science we did. Through his engagement, Ray has certainly helped
the OzFlux community to go all the way from a loose collection of colleagues
involved in flux work, through to the coordinated network that is OzFlux,
which collects high-quality data that have been published in this
special issue and as well numerous other publications. His legacy has
ensured the future success of OzFlux.
One of Ray's favourite books was Of Men and Numbers: The Story of the Great Mathematicians (Muir, 1961). It includes Sir Isaac
Newton's quote “If I have seen further, it is by standing on the shoulders
of giants”. Ray was a true intellectual giant to the OzFlux community and we
would not have been able to make the contributions to FLUXNET and the wider
scientific community if it were not for him. On 12 February 2018 it will be 2 years since Ray left us. He is sorely missed but we are deeply grateful for
the contributions he has made to both the OzFlux and the wider scientific
communities. We are grateful to Ray for his wonderful collegiality, his
tremendous contributions to science and his willingness to share his great
knowledge with all of us.
Stefan K. Arndt, Mila Bristow, David Campbell, Helen A. Cleugh,
James Cleverly, Derek Eamus, Cacilia Ewenz, Benedikt J. Fest, Peter Grace,
Anne Griebel, Samantha Grover, Vanessa Haverd, John Hunt, Nina Hinko-Najera,
Peter Isaac, Georgia Koerber, Johannes Laubach, Michael J. Liddell,
Craig Macfarlane, Ian D. McHugh, Wayne Meyer, Caitlin E. Moore,
Elise Pendall, Alison Phillips, Rebecca L. Phillips, Suzanne M. Prober,
Natalia Restrepo-Coupe, Susanna Rutledge, Cassandra Rogers, Ivan Schroder,
Richard Silberstein, Cathy M. Trudinger, Eva van Gorsel, Camilla Vote,
Tim Wardlaw and Rhys Whitley.
ReferencesAchard, F., Beuchle, R., Mayaux, P., Stibig, H.-J., Bodart, C., Brink, A.,
Carboni, S., Desclée, B., Donnay, R., Hugh D. E., Lupi, A., Ra, R.,
Seliger, R., and Simonetti, D.: Determination of tropical deforestation rates
and related carbon losses from 1990 to 2010, Glob. Change Biol., 20,
2540–2554, 10.1111/gcb.12605, 2014.Baldocchi, D. D., Falge, E., Gu, L., Olson, R., Hollinger, D., Running, S.,
Anthoni, P., Bernhofer, C., Davis, K., Evans, R., Fuentes, J., Goldstein, A.,
Katul, G., Law, B., Lee, X., Malhi, Y., Meyers, T., Munger, W., Oechel, W.,
Paw, K. T. U., Pilegaard, K., Schmid, H. P., Valentini, R., Verma, S.,
Vesala, T., Wilson, K., and Wofsy, S.: FLUXNET?: A New Tool to Study the
Temporal and Spatial Variability of Ecosystem-Scale Carbon Dioxide, Water
Vapor, and Energy Flux Densities, B. Am. Meteorol. Soc., 82, 2415–2434,
10.1175/1520-0477(2001)082<2415:FANTTS>2.3.CO;2, 2001.Beringer, J., Hutley, L. B., McHugh, I., Arndt, S. K., Campbell, D., Cleugh,
H. A., Cleverly, J., Resco de Dios, V., Eamus, D., Evans, B., Ewenz, C.,
Grace, P., Griebel, A., Haverd, V., Hinko-Najera, N., Huete, A., Isaac, P.,
Kanniah, K., Leuning, R., Liddell, M. J., Macfarlane, C., Meyer, W., Moore,
C., Pendall, E., Phillips, A., Phillips, R. L., Prober, S. M.,
Restrepo-Coupe, N., Rutledge, S., Schroder, I., Silberstein, R., Southall,
P., Yee, M. S., Tapper, N. J., van Gorsel, E., Vote, C., Walker, J., and
Wardlaw, T.: An introduction to the Australian and New Zealand flux tower
network – OzFlux, Biogeosciences, 13, 5895–5916,
10.5194/bg-13-5895-2016, 2016.Beringer, J., McHugh, I., Hutley, L. B., Isaac, P., and Kljun, N.: Technical
note: Dynamic INtegrated Gap-filling and partitioning for OzFlux (DINGO),
Biogeosciences, 14, 1457–1460, 10.5194/bg-14-1457-2017,
2017.Bristow, M., Hutley, L. B., Beringer, J., Livesley, S. J., Edwards, A. C.,
and Arndt, S. K.: Quantifying the relative importance of greenhouse gas
emissions from current and future savanna land use change across northern
Australia, Biogeosciences, 13, 6285–6303,
10.5194/bg-13-6285-2016, 2016.Cleugh, H.: Preface for the special issue on water and carbon coupling to
honour Dr Ray Leuning, Agr. Forest Meteorol., 182–183, 189–190,
10.1016/j.agrformet.2013.08.009, 2013.Cleverly, J., Eamus, D., Luo, Q., Restrepo Coupe, N., Kljun, N., Ma, X.,
Ewenz, C., Li, L., Yu, Q., and Huete, A.: The importance of interacting
climate modes on Australia's contribution to global carbon cycle extremes,
Sci. Rep.-UK, 6, 23113, 10.1038/srep23113, 2016.Climate Council: Angry Summer 2013/2014, available at:
http://www.climatecouncil.org.au/angry-summer (last access: 1 October 2016), 2014.Fest, B. J., Hinko-Najera, N., Wardlaw, T., Griffith, D. W. T., Livesley, S.
J., and Arndt, S. K.: Soil methane oxidation in both dry and wet temperate
eucalypt forests shows a near-identical relationship with soil air-filled
porosity, Biogeosciences, 14, 467–479,
10.5194/bg-14-467-2017, 2017.Haverd, V., Smith, B., Raupach, M., Briggs, P., Nieradzik, L., Beringer, J.,
Hutley, L., Trudinger, C. M., and Cleverly, J.: Coupling carbon allocation
with leaf and root phenology predicts tree–grass partitioning along a
savanna rainfall gradient, Biogeosciences, 13, 761–779,
10.5194/bg-13-761-2016, 2016.Hinko-Najera, N., Isaac, P., Beringer, J., van Gorsel, E., Ewenz, C., McHugh,
I., Exbrayat, J.-F., Livesley, S. J., and Arndt, S. K.: Net ecosystem carbon
exchange of a dry temperate eucalypt forest, Biogeosciences, 14, 3781–3800,
10.5194/bg-14-3781-2017, 2017.Hunt, J. E., Laubach, J., Barthel, M., Fraser, A., and Phillips, R. L.:
Carbon budgets for an irrigated intensively grazed dairy pasture and an
unirrigated winter-grazed pasture, Biogeosciences, 13, 2927–2944,
10.5194/bg-13-2927-2016, 2016.Isaac, P., Cleverly, J., McHugh, I., van Gorsel, E., Ewenz, C., and Beringer,
J.: OzFlux data: network integration from collection to curation,
Biogeosciences, 14, 2903–2928, 10.5194/bg-14-2903-2017,
2017.Jones, C. D., Ciais, P., Davis, S. J., Friedlingstein, P., Gasser, T.,
Peters, G. P., Rogelj, J., van Vuuren, D. P., Canadell, J., G., Cowie, A.,
Jackson, R. B., Jonas, M., Kriegler, E., Littleton, E., Lowe, J. A., Milne,
J., Shrestha, G., Smith, P., Torvanger, A., and Wiltshire A.: Simulating the
Earth system response to negative emissions, Environ. Res. Lett., 11, 095012,
10.1088/1748-9326/11/9/095012, 2016.Laubach, J., Barthel, M., Fraser, A., Hunt, J. E., and Griffith, D. W. T.:
Combining two complementary micrometeorological methods to measure CH4 and
N2O fluxes over pasture, Biogeosciences, 13, 1309–1327,
10.5194/bg-13-1309-2016, 2016.Le Quéré, C., Andrew, R. M., Canadell, J. G., Sitch, S., Korsbakken,
J. I., Peters, G. P., Manning, A. C., Boden, T. A., Tans, P. P., Houghton, R.
A., Keeling, R. F., Alin, S., Andrews, O. D., Anthoni, P., Barbero, L., Bopp,
L., Chevallier, F., Chini, L. P., Ciais, P., Currie, K., Delire, C., Doney,
S. C., Friedlingstein, P., Gkritzalis, T., Harris, I., Hauck, J., Haverd, V.,
Hoppema, M., Klein Goldewijk, K., Jain, A. K., Kato, E., Körtzinger, A.,
Landschützer, P., Lefèvre, N., Lenton, A., Lienert, S., Lombardozzi,
D., Melton, J. R., Metzl, N., Millero, F., Monteiro, P. M. S., Munro, D. R.,
Nabel, J. E. M. S., Nakaoka, S.-I., O'Brien, K., Olsen, A., Omar, A. M., Ono,
T., Pierrot, D., Poulter, B., Rödenbeck, C., Salisbury, J., Schuster, U.,
Schwinger, J., Séférian, R., Skjelvan, I., Stocker, B. D., Sutton, A.
J., Takahashi, T., Tian, H., Tilbrook, B., van der Laan-Luijkx, I. T., van
der Werf, G. R., Viovy, N., Walker, A. P., Wiltshire, A. J., and Zaehle, S.:
Global Carbon Budget 2016, Earth Syst. Sci. Data, 8, 605–649,
10.5194/essd-8-605-2016, 2016.Leuning, R., Cleugh, H. A., Zegelin, S. J., and Hughes, D.: Carbon and water
fluxes over a temperate Eucalyptus forest and a tropical wet/dry savanna in
Australia: measurements and comparison with MODIS remote sensing estimates,
Agr. Forest Meteorol., 129, 151–173, 10.1016/j.agrformet.2004.12.004,
2005.Ma, X., Huete, A., Cleverly, J., Eamus, D., Chevallier, F., Joiner, J.,
Poulter, B., Zhang, Y., Guanter, L., Meyer, W., Xie, Z., and Ponce-Campos,
G.: Drought rapidly diminishes the large net CO2 uptake in 2011 over
semi-arid Australia, Sci. Rep.-UK, 6, 37747, 10.1038/srep37747, 2016.McHugh, I. D., Beringer, J., Cunningham, S. C., Baker, P. J., Cavagnaro, T.
R., Mac Nally, R., and Thompson, R. M.: Interactions between nocturnal
turbulent flux, storage and advection at an “ideal” eucalypt woodland site,
Biogeosciences, 14, 3027–3050, 10.5194/bg-14-3027-2017,
2017.Moore, C. E., Beringer, J., Evans, B., Hutley, L. B., McHugh, I., and Tapper,
N. J.: The contribution of trees and grasses to productivity of an Australian
tropical savanna, Biogeosciences, 13, 2387–2403,
10.5194/bg-13-2387-2016, 2016a.Moore, C. E., Brown, T., Keenan, T. F., Duursma, R. A., van Dijk, A. I. J.
M., Beringer, J., Culvenor, D., Evans, B., Huete, A., Hutley, L. B., Maier,
S., Restrepo-Coupe, N., Sonnentag, O., Specht, A., Taylor, J. R., van Gorsel,
E., and Liddell, M. J.: Reviews and syntheses: Australian vegetation
phenology: new insights from satellite remote sensing and digital repeat
photography, Biogeosciences, 13, 5085–5102,
10.5194/bg-13-5085-2016, 2016b.Moore, C. E., Beringer, J., Evans, B., Hutley, L. B., and Tapper, N. J.:
Tree–grass phenology information improves light use efficiency modelling of
gross primary productivity for an Australian tropical savanna,
Biogeosciences, 14, 111–129, 10.5194/bg-14-111-2017, 2017.
Muir, J.: Of Men and Numbers: The Story of Great Mathematicians, Dodd, Mead &
Company, New York, USA, 1961.Poulter, B., Frank, D., Ciais, P., Myneni, R. B., Andela, N., Bi, J.,
Broquet, G., Canadell, J. G., Chevallier, F., Liu, Y. Y., Running, S. W.,
Sitch, S., and van der Werf, G. R.: Contribution of semi-arid ecosystems to
interannual variability of the global carbon cycle, Nature, 509, 600–603,
10.1038/nature13376, 2014.Restrepo-Coupe, N., Huete, A., Davies, K., Cleverly, J., Beringer, J., Eamus,
D., van Gorsel, E., Hutley, L. B., and Meyer, W. S.: MODIS vegetation
products as proxies of photosynthetic potential along a gradient of
meteorologically and biologically driven ecosystem productivity,
Biogeosciences, 13, 5587–5608, 10.5194/bg-13-5587-2016,
2016.Rogers, C. D. W. and Beringer, J.: Describing rainfall in northern Australia
using multiple climate indices, Biogeosciences, 14, 597–615,
10.5194/bg-14-597-2017, 2017.Trudinger, C. M., Haverd, V., Briggs, P. R., and Canadell, J. G.: Interannual
variability in Australia's terrestrial carbon cycle constrained by multiple
observation types, Biogeosciences, 13, 6363–6383,
10.5194/bg-13-6363-2016, 2016.van Gorsel, E., Berni, J., Briggs, P., Cabello-Leblic, A., Chasmer, L.,
Cleugh, H., Hacker, J., Hanson, S., Haverd, Hughes, D., Hopkinson, C., Keith,
H., Kljun, N., Leuning, R., Yebra, M., and Zegelin, S.: Primary and secondary
effects of climate variability on net ecosystem exchange in an evergreen
Eucalyptus forest, Agr. Forest Meteorol., 182–183, 248–256,
10.1016/j.agrformet.2013.04.027, 2013.van Gorsel, E., Wolf, S., Cleverly, J., Isaac, P., Haverd, V., Ewenz, C.,
Arndt, S., Beringer, J., Resco de Dios, V., Evans, B. J., Griebel, A.,
Hutley, L. B., Keenan, T., Kljun, N., Macfarlane, C., Meyer, W. S., McHugh,
I., Pendall, E., Prober, S. M., and Silberstein, R.: Carbon uptake and water
use in woodlands and forests in southern Australia during an extreme heat
wave event in the “Angry Summer” of 2012/2013, Biogeosciences, 13,
5947–5964, 10.5194/bg-13-5947-2016, 2016.Whitley, R., Beringer, J., Hutley, L. B., Abramowitz, G., De Kauwe, M. G.,
Duursma, R., Evans, B., Haverd, V., Li, L., Ryu, Y., Smith, B., Wang, Y.-P.,
Williams, M., and Yu, Q.: A model inter-comparison study to examine limiting
factors in modelling Australian tropical savannas, Biogeosciences, 13,
3245–3265, 10.5194/bg-13-3245-2016, 2016.Whitley, R., Beringer, J., Hutley, L. B., Abramowitz, G., De Kauwe, M. G.,
Evans, B., Haverd, V., Li, L., Moore, C., Ryu, Y., Scheiter, S., Schymanski,
S. J., Smith, B., Wang, Y.-P., Williams, M., and Yu, Q.: Challenges and
opportunities in land surface modelling of savanna ecosystems,
Biogeosciences, 14, 4711–4732, 10.5194/bg-14-4711-2017,
2017.