Carbon mitigation from agroforestry in salinized low rainfall farmland landscapes

215 Pages·2017·2.99 MB·English

by  Stanley Sochacki

Carbon mitigation from agroforestry in salinized low
rainfall farmland landscapes

This thesis is presented for the degree of
Doctor of Philosophy

in the

School of Veterinary and Life Sciences,
Murdoch University, Australia

2016

Stanley J. Sochacki, BSc (Hons)
DECLARATION

I declare that this thesis is my own account of my research and contains as its main
content work which has not previously been submitted for a degree at any tertiary
education institution.

S.J. Sochacki Date
Abstract
Efforts to reduce greenhouse gas emissions have become a global priority and the land
sector can contribute significantly to achieving this via a range of mitigation strategies
such as the biosequestration of carbon and substitution of fossil fuels through
bioenergy. However, the implementation of land sector mitigation is constrained by
several uncertainties and knowledge gaps particularly within low rainfall (300 to 400
mm yr-1) farmland environments.
This thesis examines aspects of land sector mitigation through reforestation systems
integrated into dryland (300 to 400 mm yr-1) farming systems in Western Australia.
The uncertainties that are examined in this thesis include (a) estimation of tree root
carbon storage, (b) exploring whether carbon mitigation can be achieved through new
agroforestry systems that reduce competitive effects and (c) assessing the
sustainability of these new systems in terms of nutrient removal.
Estimates of below ground biomass pools are critical to establishing carbon fluxes on
regional scales which can then be applied in global modeling of climate change
mitigation strategies. A new methodology for tree below-ground biomass estimation
was developed, including a purpose-designed coring machine. Monte Carlo simulation
was used to assess the accuracy of a range of sampling regimes through estimates of
uncertainty (precision) and bias (error) and these sampling methods were subsequently
used to develop allometric relationships to estimate the carbon mitigation potential of
tree phases integrated into agricultural systems.
The implications of integrating tree phases into agricultural systems and the effects of
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this on the sustainability of existing farming systems were investigated. This included
an assessment of potential land use synergies targeting abandoned or marginal land for
multiple land use outcomes via landscape rehabilitation and carbon mitigation. The
integration of short tree phases (3 years) into low rainfall salinized farmland for the
purpose of soil salinity amelioration was shown to have additive environmental
benefits as a potential source of biomass feedstock for renewable energy. Allometric
relationships were developed for three candidate species (Eucalyptus globulus, E.
occidentalis and Pinus radiata) and their carbon storage was assessed based on whole
tree destructive sampling, including below ground sampling. The biomass production
for different planting density and landscape placement strategies, and for different tree
components was estimated to assist in future development of harvesting systems and
management of nutrient removal. It was shown that tree phases inserted into farming
systems for the purpose of ground water control could potentially serve as a biomass
feedstock for renewable energy, either bioenergy for power generation or as feedstock
for lignocellulosic (second generation) biofuel, thus offsetting the use of non-
renewable fossil fuel.
The sustainability of these systems was investigated to determine their impact on
current farming systems and the potential removal of nutrients. Harvesting regimes
that remove woody biomass while retaining leaves on site are likely to be more
sustainable from a nutrient management perspective. A nutrient assimilation index
was developed for these short rotation tree crop systems to aid the management of
nutrient removal. The removal of nutrients via a short (3 year) tree phase was less than
the cereal cropping systems currently in place and had potential to retrieve leached
nutrients from deeper in the soil profile.
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Planting of tree and shrub species in severely salinized abandoned farmland was
shown to be a potential avenue for carbon mitigation, and a resultant positive land use
change. With species selection, management of stand density and landscape position,
tree growth and carbon sequestration can be manipulated with rates of sequestration of
1.1 to 2.3 t ha-1 yr-1 following 8 years growth in the highly saline environment. A
combination of shrub (Atriplex nummularia) and tree (Eucalyptus occidentalis)
species were used to mimic natural saline wetland succession and were successful in
rehabilitating degraded farmland while effectively sequestering carbon and mitigating
atmospheric CO .
2
The challenge remains to integrate these mitigation initiatives and systems into
existing economic and social environments and for them to be accepted as typical
economic activities. This is not only a challenge from the scientific view point, but
encompasses social and political aspects which often makes its application difficult.

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Acknowledgements
First and foremost I would like to thank my supervisors, Professor Richard Harper and
Professor Bernard Dell for their patience, enthusiasm, and guidance throughout my
candidature. Work colleagues Bruce Brand and Dr Peter Ritson provided valuable
input and feedback on the research projects.
I thank the many contractors and helpers who worked with me in the field and in the
laboratory, processing the countless samples which make up the datasets in this thesis.
Particular thanks are due to Phil Fruet and Jennifer Hickling who spent many long
days working on the sieving table.
I would like to thank Murdoch University for funding through a Murdoch
Postgraduate Research Scholarship and the staff of the post graduate office. Funding
for the research projects related in this thesis are from several sources; Chapters 3 and
4, funding was provided by the Western Australian Department of Conservation and
Land Management and the Co-operative Research Centre for Greenhouse Accounting,
Chapters 5 and 6 funding was provided by the Australian Joint Venture Agroforestry
Program Project CAL-6A and Chapter 7 funding was provided by the Australian
Joint Venture Agroforestry Program Project CAL-8A and the Natural Heritage Trust
Farm Forestry Program Project ‘Putting Trees in Their Place’ (983197).

I would also like to thank all land owners for their time and interest in this research
and who generously provided access to their land.

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Finally, I would like to thank my family who put up with my absence when I was
away from home on the many field trips and for their patience during the time spent
completing this thesis part-time while in full-time employment.

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Publications from this thesis
Sochacki, S.J., Ritson, P. and Brand, B. (2007) A specialised soil corer for sampling
tree roots. Australian Journal of Soil Research 45, 111-117. (Chapter 3)

Sochacki, S.J, Ritson, P., Brand, B. Harper, R.J, and Dell, B. (2016) Accuracy of
tree root biomass sampling methodologies for carbon mitigation projects.
Ecological Engineering (in press) http://dx.doi.org/10.1016/j.ecoleng.2016.11.004
(Chapter 4)

Sochacki S.J., Harper R.J. and Smettem, K.R.J. (2007). Estimation of woody
biomass for short rotation bio-energy species in south-western Australia. Biomass
& Bioenergy 31, 608-616. (Chapter 5)

Sochacki S.J., Harper R.J. and Smettem, K.R.J., Dell, B. and Wu, H. (2012)
Evaluating a sustainability index for nutrients in short rotation energy cropping
systems. GCB Bioenergy 5: 315-326. (Chapter 6)

Sochacki S.J., Harper R.J. and Smettem, K.R.J. (2011) Bio-mitigation of carbon
from reforestation of abandoned farmland. GCB Bioenergy 4: 193-201. (Chapter
7)

International conference papers:
1. Sochacki, S.J., Harper, R.J., Smettem, K.R.J. and Dell, B. (2014). A
sustainability index for improving nutrient management in short rotation
bioenergy systems. XXIV IUFRO World Congress 2014 – Salt Lake City, Utah,
United States, 5-11 October 2014 “Sustaining Forests, Sustaining People: The
Role of Research”. International Forestry Review, 16: 261.

2. Sochacki, S.J. (2016). Reforestation of dryland farming systems: potential and
challenges, IUFRO Regional Congress for Asia and Oceania 2016 China
National Convention Centre, Beijing, China October 24-27, 2016

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Acronyms and terms
ACCU Australian Carbon Credit Units
AFOLU Agriculture, Forestry and Other Land Use
AGB Above Ground Biomass
AGO Australian Greenhouse Office
BGB Below Ground Biomass
C Carbon
CEFC Clean Energy Finance Corporation
CER Clean Energy Regulator
CFI Carbon Farming Initiative
CO Carbon dioxide
2
COP-3 Third Conference of the Parties to the United Nations
Framework Convention on Climate Change
CPM Carbon Pricing Mechanism
CP1 First Commitment Period of the Kyoto Protocol
CP2 Second Commitment Period of the Kyoto Protocol
CV Coefficient of Variation
CVI Crown Volume Index
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DAP Direct Action Plan
DBH Diameter at Breast Height
DOB Diameter Over Bark
EDM Edible Dry Matter
ERF Emissions Reduction Fund
ETS Emissions Trading Systems
FI Fit Index
FOLU Forestry and Other Land Use
GHG Greenhouse Gas
I Furnival Index
IEA International Energy Agency
IPCC Intergovernmental Panel on Climate Change
KP Kyoto Protocol (to the United Nations Framework Convention
on Climate Change)
Mg Mega-grams (metric ton)
NAI Nutrient Assimilation Index
NDCs Nationally Determined Contributions
NLWRA National Land and Water Resources Audit
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