School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemThe effectiveness of nitrogen fertiliser use for wheat production with an emphasis on elevated carbon dioxide environments( 2013)Variability in crop responses to nitrogen (N) is influenced by many factors that are subject to complex interactions. A meta-analytic approach was used to study variability in crop responses to N fertiliser application using a large dataset of Australian annual N fertiliser trials. This analysis provided baseline information about existing performance and management of N fertilisers for crop production. However under predicted changes in atmospheric CO2 concentration, new challenges exist for N management and there is limited information on this. A series of controlled environment and field experiments were established to examine the effects of N fertiliser strategies (inhibitors, foliar applications) on N availability, crop N status, grain protein, and soil nitrous oxide emissions under ambient and elevated CO2 (e[CO2]) conditions to better understand the challenge of effective N use under future climates. The findings from the meta-analysis revealed that the effectiveness of N use will be more predictive when making N management decisions for moderate yielding environments but require caution when applied in low and high yielding environments; splitting high N application rates by considering the timing of N application can significantly alter the response, especially for N uptake; urease inhibitor (at a higher concentration of inhibitor) and nitrification inhibitor can enhance the yield and grain N uptake of basic N products; nitrification inhibitors will enhance N uptake in high yielding areas under particular soil texture conditions; and in coarse texture soils, high rates of N application will produce lower relative responses when rainfall is high compared to when seasonal rainfall is lower. The findings from the studies conducted under e[CO2] conditions suggest that at maturity the use of nitrification inhibitor might play a role to compensate the slow mobilisation of N towards grain. Foliar N application might not be a viable strategy to be used to influence grain N characteristics under e[CO2]. Nitrous oxide emissions may increase in legume based cropping systems but the interaction with [CO2] was not significant. The meta-analysis can be used as a guideline for N management. However, this analysis was limited to agronomic responses and further studies while considering economic factors are needed for more informed N management decisions. Under future climate of e[CO2], it is debatable whether better synchronisation of N supply with crop demand can compensate for a decrease in tissue N concentration, or whether a physiological constraint exists that needs to be overcome through further research.
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ItemFactors affecting microwave modified wood permeability and strength( 2013)Microwave treatment can be used to increase wood permeability, speeding subsequent drying or impregnation processes with potential savings in time, energy and cost. However microwave treatment can reduce the strength of the treated timber. Treatment pressure can be used to alter the boiling point of water, which could have a significant effect on the resultant strength and permeability. Three methodologies were used to investigate the relationship between microwave treatment conditions, in particular pneumatic pressure, and the resultant strength and permeability of the timber. A device was designed and constructed with the aim of enabling the simultaneous measurement of the permeability of small cylindrical samples during microwave treatment. Testing of the individual components proved successful, however moisture vapour generated during microwave heating of the timber samples presented problems during combined testing. Permeability measurements were performed separately in the second and third methodologies and utilised larger samples. Controlled temperature and controlled power density treatments were trialled with the controlled power density treatment providing more consistent results. Bending testing and an impregnation cycle were found to be the most reliable methods of assessing strength and permeability respectively. High power microwave treatment increased the permeability and reduced the strength of the treated timber. Treating the samples under elevated pressure, followed by an immediate pressure delta minimised this strength loss. A ranking system was proposed to assess the combined strength and permeability resulting from treatment. Using this ranking system, an optimum balance between high permeability and maximum strength was obtained using a high power, Elevated Pressure Microwave treatment followed by an Immediate Pressure Delta (EPMIPD). This treatment performed better than atmospheric pressure microwave treatments conducted as part of this research.
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ItemWheat grain quality dynamics under elevated atmospheric CO2 concentration in Mediterranean climate conditions( 2013)Since 1959, carbon dioxide concentration [CO2] in the atmosphere increased from 315 µmol mol-1 to approximately 389 µmol mol-1 by 2009 in a rate of 1.5 µmol mol-1 per year. Within the next 50 years, atmospheric [CO2] will likely to rise to 550 µmol mol-1. Carbon dioxide is a greenhouse gas and a major factor that contributes to global warming. In parallel, global temperature is predicted to increase by an average of 1.5-4.5 ºC with more frequent occurrences of extreme climatic events such as heat waves and/or drought by the mid of this century. There is a limited understanding on the impact of elevated atmospheric [CO2] (e[CO2]) on wheat grain quality in semi-arid and Mediterranean cropping systems. The research reported in this thesis investigated the effects of e[CO2] on wheat grain physical, chemical, flour rheological properties under two main climate conditions: semi-arid and Mediterranean which represent the water-limited “mega-environment 4”, larger wheat grown area in the world as defined for wheat (Braun et al., 1996). The experiments were carried out using state art technology of free- air CO2 enrichment (FACE) facilities located in Walpeup and Horsham, Victoria, Australia. (See thesis for full abstract)
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ItemA study of salinity tolerance in field pea( 2013)Preliminary research was aimed at identification of parental germplasm that could be used for improvement of tolerance to toxic effects of sodium chloride (NaCl) in field pea. An initial screening experiment of 780 globally-distributed Pisum L. accessions identified significant variation in response to applied NaCl, based on plant symptoms. Lines with relatively higher tolerance as compared to commercial varieties grown in Australia were most frequently identified within landraces originating from the central, eastern and southern provinces of China. The most tolerant identified accession was an unadapted landrace ‘ATC1836’ originating from Greece. Variation for salinity tolerance was validated using a sub-set of 70 accession lines. Salinity-induced toxicity symptoms were closely associated with reductions of plant growth rate, height, shoot and root dry matter and with increased concentration of Na+ at the plant growing tip. The level of salinity tolerance based on these factors varied substantially and provides an important basis for genetic improvement of field pea for Australia. Seven field pea genotypes that vary significantly for salinity tolerance showed a range of symptom development and growth responses over time under increasing levels of NaCl salinity applied using watering treatments. The genotypic responses were closely associated with Na+ accumulation in leaflet tissue on the lower plant and a parallel reduction in K+ concentration. Increasing salinity caused strong but variable inhibition of root and shoot dry matter accumulation and final grain yield for all genotypes. The genotype ATC1836 showed the highest relative tolerance based on measured parameters, but was comparatively slow growing. Three genotypes (03H090P-04HO2002, 03H556P-04HO2012, 99-410-2-14-2) with moderate tolerance obtained substantially more dry matter under the highest salinity treatment of (18 dsm-1) compared to the commercial variety ‘Kaspa’. The genotype OZP0812 was also able to maintain relatively higher growth rate at the lower salinity treatment level of 6 dsm-1. The high salinity tolerance of the landrace genotype ATC1836 that is evident at early growth stages was also apparent in this study at later ontogeny, on the basis of lower biomass reduction, reduced symptom development and delayed rate of Na+ accumulation in plant tissue. In this study, sodium accumulated more rapidly and to a higher degree, and symptoms developed faster on lower growth nodes when compared to the growing tip. Plant biomass and main plant height showed lower correlation with Na+ concentration in plant tissue than plant chlorosis. The taller genotype OZP0812 produced more biomass under conditions of increasing salinity than the dwarf genotypes Kaspa and OZP0809 and the landrace genotype ATC1836. Applied salinity exerted deleterious and varying effects on seed yield components such as reduced seed and pod set and seed size. The genotype OZP0812 maintained both higher seed yield and larger seed size compared to the salinity tolerant landrace genotype ATC1836, despite accumulation of more Na+ in plant tissue. Increased salinity resulted in earlier flowering and increased Na+ concentration in seed tissue. Segregation ratios for salinity tolerance were analysed in 3 field pea populations derived from crosses between the sensitive genotype Kaspa and the tolerant genotypes ATC1836, Parafield and Yarrum, revealing probable multigenic control. A comparatively higher proportion of tolerant progeny was observed in the ATC1836 x Kaspa population. However, a high degree of trangressive segregation for enhanced salinity tolerance was apparent in progeny from crosses of either Parafield or Yarrum with Kaspa, suggesting that parental combining abilities should also be assessed for improvement of salinity tolerance. Positive broad sense heritabilities for measures of symptom response to salinity, and repeatability of results between experiments and generations implied high potential for genetic gain from use of pot-based screening methods. Differences in assessment of salinity symptom response based on a numerical scale as compared to percentage plant necrosis were not significant. Variation for salinity tolerance within recombinant inbred lines (RILs) progeny derived from the Kaspa x Parafield cross was documented on the basis of rate of symptom development and a salinity tolerance index. A frequency analysis showed that the proportion of field pea germplasm with higher salinity tolerance in advanced yield testing nurseries in Australia had increased in the period 2005-2011. However, a multivariate canonical analysis based on 14 yield nurseries in 2011 indicated that the degree of salinity tolerance in advanced germplasm currently provides significantly less yield benefit than degree of boron toxicity tolerance, indicating a need for further pre-breeding efforts. Boron tolerant accessions as a group were higher yielding at 7 sites during 2011. All of these sites were in regions with highly alkaline sub-soils, and six sites had comparatively lower growing season rainfall. The high rainfall exception (Kingsford, South Australia) was affected by powdery mildew, for which resistance is positively linked with high boron tolerance. Genotypes with dual sensitivity to both boron and salinity mostly performed better at sites with higher rainfall in the growing season. For sites at which salinity tolerance was more important, the only sensitive genotypes that performed well were all early flowering (i.e. PBA Twilight). One boron sensitive genotype (119) showed specific adaptation across sites at which boron tolerance was important, and is hence suitable as a key parent for improving general adaptation of crop. Linkage maps based on molecular genetic marker polymorphism were constructed for RIL populations of Kaspa x Parafield and Kaspa x Yarrum populations. RIL progeny and parents from these populations were screened at the seedling growth stage for growth symptom responses to salinity stress imposed by adding NaCl in the watering solution at a concentration of 18 dsm-1. Phenotypic variation for salinity induced symptoms was normally distributed and increased with severity over time. A salinity index was developed to quantify variation for salinity tolerance and was used in concert with statistical correlation analysis to identify quantitative trait loci (QTLs) and flanking single nucleotide polymorphism (SNP) markers that could be useful for implementation of marker assisted selection (MAS) strategies. This thesis has identified valuable variation in salinity tolerance in Pisum for field pea breeding programs. A knowledge of critical growth responses at the seedling and reproductive growth stages for salinity tolerance now provides a guide to screening of populations for useful genetic variation or marker-tagged QTLs. Preliminary investigation has identified QTLs for seedling tolerance to salinity stress for implementation of MAS for the purposes of parent building and routine screening.
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ItemStructural variations in the ovine genome: their detection and association with phenotypic traits( 2013)Growth and meat yield traits are important to the New Zealand sheep industry. Genomic selection (GS) of these traits uses information from high density ovine SNPs to produce estimated breeding values (EBVs). The aim of GS is to account for loci directly influencing the trait (quantitative trait loci, QTL). This relies on the assumption that high density SNPs tag QTL effects via linkage disequilibrium (LD), however, it is unlikely that all QTL are adequately tagged by high density SNPs. Copy number variants (CNVs) are a type of genetic variant that may not be well tagged by SNPs and have been shown to be involved in phenotypic variation. To date, there has been little published work on CNVs in the sheep genome. While there is a well known example of a CNV affecting coat colour (agouti) in sheep, little is known of how CNVs affect phenotypic variation of production traits. The studies in this thesis employed multiple methods to identify CNVs in the sheep genome. Animals (including trios) were assayed on a Roche NimbleGen 2.1M CGH array. CNV calls from trios were used along with known false-positive calls to build a logistic regression to predict the probability calls from the 2.1M CGH array were correct. 3,488 autosomal CNVRs were identified. On a large scale, CNVRs were hard to accurately detect without using a combination of approaches. CNVRs were verified against CNVRs detected with the Roche NimbleGen 385K CGH array, Illumina OvineSNP50 BeadChip and Illumina HiSeq 2000 sequence data. Results of this work contribute a comprehensive resource of CNV regions to the literature on sheep CNVs. Given the importance of growth and meat yield traits in the New Zealand sheep industry, and the possibly unaccounted effects of CNVs on these traits, an association analysis was carried out with these traits and loci that potentially represent CNVs. Firstly, it was determined that EBVs produced by Sheep Improvement Limited (SIL) were appropriate to use as the dependent variable in the association analysis. Loci that potentially represent CNVs were SNPs from the Illumina OvineSNP50 BeadChip that were previously discarded from GS and genome wide association studies (GWAS) because they could not be genotyped. Reasons why these SNPs can’t be genotyped include the presence of the SNP in a CNV. Raw data from these SNPs were tested to determine if they were associated with the growth and meat yield traits. Seventeen associations, involving nine SNPs, were detected and validated in independent datasets. Two SNPs were in CNVRs detected using the CNV detection methods described above - one involved the agouti CNV. Raw data from this SNP was associated with ultrasonic eye muscle depth. Associations remained significant after fitting genotypes of flanking SNPs (from surrounding ~1Mb of sequence) used in GS and GWAS, suggesting that the effect of these associations are not accounted for in GS or GWAS. Including information from these SNPs in GS could improve the reliability of EBVs, contributing to genetic improvement of growth and meat yield traits in the New Zealand sheep industry.
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ItemThe role of the antioxidants ascorbate and glutathione, in the plant-pathogen interaction between Phytophthora cinnamomi Rands and susceptible and resistant Eucalyptus species( 2013)This study investigates the role that the low molecular weight antioxidants, ascorbate and glutathione, play in the plant-pathogen interaction between Eucalyptus spp. and Phytophthora cinnamomi - Rands. The study has shown that plant responses (i.e. antioxidant concentration changes, rates of photosynthesis, stomatal conductance, quantum efficiency of photo-system II and carbohydrate levels) to P. cinnamomi root infection in roots and leaves differ significantly between susceptible and resistant Eucalyptus species. Antioxidant concentration decreases and an increased sensitivity to leaf photoinhibition were associated with infection in susceptible E. sieberi. In contrast, early antioxidant increases were associated with resistant E. sideroxylon.
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ItemPasture investment decisions: returns, risk and time( 2013)Making risky investment decisions well is an important part of farm business management. Risky investment decisions are those for which the rate of return on capital is not known when the decision to invest is made. To be complete, analysis of such decisions must include consideration of expected returns, risk and the dynamic element of time. This thesis contains such an analysis, in relation to decisions to invest in pasture improvement on farms in south west Victoria, Australia. The return and risk of these investments were estimated using stochastic simulation of a whole farm economic model. The real options approach was used to value the risk associated with these investments. This analysis revealed that pasture investments generate risk-adjusted returns which compare favourably to those generated by other readily-available investments, such as bank deposits or shares. The estimates of return and risk are static – they do not change over time. As such, this analysis generates no insight into the dynamic aspect of decisions to invest in pasture improvement, and cannot explain some elements of observed pasture investment decisions. To remedy this deficiency, the dynamic aspect was investigated by representing the ability of investors to reduce uncertainty over time in a Bayesian learning model. Learning alters the perceived distribution of values that can be taken by a variable of interest over time. As this occurs, the decision to invest in pasture improvement may also be revised. Performing this analysis revealed that a learning model is a suitable tool for representing the dynamic aspect of decisions to invest in pasture improvement, even when the data required to calibrate the model are relatively scarce. Furthermore, insights were obtained into the quantity and quality of data obtained at different stages throughout the learning process. These estimates indicate that, in this case, more information is obtained from a one-year on-farm trial than is obtained from three years of collecting information from off-farm sources. This study shows how a comprehensive analysis of risky farm investments can be performed, and hence represents a contribution to the discipline of farm management economics. Furthermore, information about the return, risk and dynamic aspects of decisions to invest in pasture improvement can help various groups and organisations make better decisions. In particular, the implications of this study are considered for farmers and their advisors, rural merchandise sellers, research and development organisations and policy-makers.
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ItemPhytocaps as biotic systems to mitigate landfill methane emissions( 2013)Landfill gas is a significant source of anthropogenic methane emissions and accounts for more than half of greenhouse gas emissions from waste sectors. While harvesting landfill gas for energy is the best mitigation option, methane oxidation by landfill cover soils is considered an important secondary measure to reduce landfill methane emissions. In recent years, regulatory control has evolved to allow consideration of alternative options for final covers. An evapotranspiration cover, also commonly known as phytocap in Australia, is one of the alternative cover options that has been widely considered and investigated. A phytocap presents a soil-plant alternative to the traditional barrier cap approach. It relies on the capacity of a porous layer of soil to store water, and the combination of evaporation and transpiration of vegetation to control the percolation of water into a landfill. When planted with native vegetation, it also improves the ecology and sustainability of a closed landfill. While the hydrological performance of phytocap has been investigated by a number of studies resulting in positive outcomes, its ability to serve also as a “biocover” for effective methane oxidation to mitigate emissions has received little attention. The main aim of this thesis was to assess phytocap performance in terms of enhancing methane oxidation activity in the cover soil and mitigating methane emissions. The research methodology included a full-scale field comparison between phytocaps and conventional compacted clay covers in terms of methane oxidation and emissions. A supplementary glasshouse experiment with both blank and planted soil columns was also conducted to investigate vegetation-methane interactions, and to identify plant influenced soil properties that would affect methane oxidation and emissions. This research forms a part of the 5-year Australian Alternative Cover Assessment Project (A-ACAP), co-funded by the Australian Research Council and Waste Management Association of Australia. In the full-scale field comparison, trial sites located at five landfills under a broad range of Australian climatic conditions have been monitored. The 5 A-ACAP trial sites with side-by-side phytocap and conventional cover test pads were built directly on top of active landfills with an aim to study their hydrological performance as well as methane mitigation efficiency. This thesis related to the methane mitigation component focused on the trial site located in Melbourne where more frequent monitoring campaigns have been conducted. The results of the field trial indicated that phytocaps could mitigate methane emissions more effectively compared to conventional covers. Emission rates detected from the Melbourne phytocap averaged at 1.45 gCH4/m2/day (out of the 17% measurements that resulted in significant positive fluxes), compared to the conventional cover which averaged at 5.57 gCH4/m2/day (out of the 65% measurements that resulted in significant positive fluxes). This positive finding is supported by the gas concentration profile data obtained from both types of covers. The field trial also concluded that the effectiveness of methane oxidation in phytocaps can be significantly enhanced with methane emission reduced to a negligible level when used in combination with gas extraction systems. In contrast, only a marginal gas extraction influence was observed on conventional covers. In addition to the overall reduction in emissions, phytocaps can also significantly reduce the amount of hot spots in surface emissions. For the glasshouse experiment, at both high and low gas influx rates, the planted soil columns showed high oxidation fractions (mostly higher than 0.5), which are comparable to the performance of some biocovers reported in the literature. Rather unexpectedly, the blank soil columns exhibited an even higher average CH4 oxidation fraction (average 0.89 under 36.5-73 gCH4/m2/day load) compared to the planted soil columns (average 0.67 under 36.5-73 gCH4/m2/day load). This finding appeared to be contradictory to the positive methane oxidation enhancement effects of vegetation in soil covers commonly reported in previous studies. With a closer examination, it was observed that the plant roots brought in a significant increase in soil gas diffusivity of the planted columns, which significantly shortened the methane retention time in the soil and subsequently reduced the methane oxidation capacity of the planted columns. The high oxidation fraction of the blank columns was attributed to the organic rich soil. Combining the research of this thesis with the findings of a concurrent A-ACAP hydrological study, it can be concluded that phytocaps provide an economical and sustainable option for new and old landfills to minimise water percolation and to mitigate methane emissions. As a result of achieving the objective of minimising percolation, the soil moisture profile of a phytocap may not be at its optimum for methane oxidation during certain periods of the year. Maintaining a balance between minimising water infiltration and promoting methane oxidation has to be addressed in a phytocap design in order to achieve optimum performance in both functionalities.
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ItemEffects of wildfire on forest structure and plant functioning in resprouting forests: implications for catchment water balance( 2013)Globally, forests release large amounts of water that are critically important for urban and industrial water supply. Forests also account for the majority of terrestrial carbon sequestration. In southern Australia, much of the water supply comes from protected catchments vegetated by eucalypt forests. The primary natural disturbance in these forests is wildfire, with close to 3 million hectares burnt over the last decade in the state of Victoria (DSE 2013). Given that forest water-use (the volume of water released to the atmosphere) can change following disturbance, thereby changing the volume of streamflow discharge, understanding the effects of wildfire on forest water-use is vital for water resource planning. Concern around the effects of wildfire on water supply were heightened in 2009 when, following a prolonged drought that necessitated water restrictions, the Black Saturday wildfires burnt through 430 000 ha, including 30% of the water supply catchments for Melbourne, Australia’s second largest city. There are two different ecological responses of eucalypt forests to wildfire. The mixed eucalypt species forests are facultative resprouters, meaning they primarily regenerate vegetatively, with some seedling recruitment. In contrast, ash-type forests are obligate seeders, meaning they are largely killed by fire and regenerate from seed. Despite mixed eucalypt species forests dominating southern Australia’s water catchments, the effect of wildfire on evapotranspiration and streamflow from this forest type is unknown. Research to date has instead been focused on ash-type forests where post-fire evapotranspiration can be up to double that of long unburnt forest, leading to a corresponding reduction in streamflow. The central aim of this thesis is thus to elucidate how post-fire changes in forest structure and plant functioning in resprouting forests affects catchment water balance. Focusing research on the resprouting mixed eucalypt species forests not only addresses this knowledge gap in ecohydrology in Australian catchments, but also provides an opportunity to investigate the effects of altering foliage distribution, while largely maintaining other attributes of forest structure. The overall approach of the thesis is to evaluate the influence of post-fire changes in forest structure and functioning on evapotranspiration and streamflow. This is a process based approach which identifies the mechanisms underlying any observed changes in catchment water balance. This approach is critical for modelling the impacts of topographic driven variability in forest type and variability in fire severity on catchment water balance; and for predicting changes in evapotranspiration under circumstances other than those measured, such as at other locations or under a different climate. Such an approach also provides insights into the functioning of other resprouting vegetation types, which are found across the globe. The research presented in this thesis found that observed post-fire evapotranspiration was a function of both fire severity and landscape position. In forest subject to high intensity wildfire (100% canopy scorch), evapotranspiration was substantially less than in unburnt forest, over 1-3 years post-fire. The magnitude of change in evapotranspiration in forest burnt at moderate severity (<30% canopy scorch), was much less than for high intensity fire. Evapotranspiration was consistently lower in damp forest (located on southern slopes and gullies) than dry forest, although the rate of recovery was similar. These reductions in evapotranspiration in burnt forest were driven by lowered stand-scale transpiration. This was a function of partial tree mortality, 100% shrub mortality, and reduced transpiration within surviving trees. Reductions in stand-scale transpiration were partially offset by increased interception and evapotranspiration close to the forest floor, this in turn was driven by regenerating seedlings which increased the total leaf area of burnt forest. Despite lower transpiration per unit sapwood area in surviving trees, transpiration per unit leaf area was higher compared to unburnt trees. This was related to the post-fire canopy architecture of surviving trees, with more foliage located at lower heights than in unburnt trees. This lower foliage had higher rates of gas exchange, consistent with the hydraulic limitation hypothesis which predicts higher gas exchange in lower foliage due to a shorter hydraulic path length and lesser gravitational force. Recovery of evapotranspiration is predicted to occur within 10-15 years post-fire, over which time net evapotranspiration, when compared with unburnt forest, is predicted to be lower in forest burnt at high severity, but higher in forest burnt at moderate severity. These changes in forest water-use are expected to result in net streamflow increases following severe wildfire, but net decreases following moderate severity fire, subject to soil water storage dynamics. Streamflow observations from a mixed eucalypt species forested catchment burnt at light-moderate severity supports these predictions, with streamflow lower than expected due to fire induced changes in evapotranspiration dynamics over the initial five years post-fire. The research findings presented in this thesis demonstrate the importance of both forest structure and plant functioning in governing catchment water balance. These findings also demonstrate that the ecological response of species to disturbance is a critical factor in determining rates of recovery of carbon and water fluxes.
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ItemThe potential use of LiDAR and digital imagery in selection of suitable forest harvesting systems( 2013)Major factors affecting the productivity and efficiency of mechanized forest harvesting systems include stand conditions (e.g. tree form, tree size, crown size and the type and density of trees), terrain conditions (e.g. slope, ground roughness, ground strength, road and drainage features, etc.), yield, operator performance (e.g. experience, skill and work technique), and machinery limitations or design. The purpose of the study was to examine whether ‘tree size’ and ‘slope’ information derived from LiDAR (Light Detection And Ranging) data and multispectral imagery, could be used to predict the productivity and efficiency of forest harvesting equipment. Tree size is known to be the biggest influence on harvester productivity. The study aimed at developing a productivity model for a harvester operating in a 35-year-old radiata pine (Pinus radiata) plantation in South Australia using data obtained from low density LiDAR (Light Detection And Ranging) (2.6 points / m2) and high resolution Quickbird imagery (60 cm). Tree size extracted from a harvester onboard computer system (OBC) was used to estimate tree size impact on harvester productivity by conducting a time study. LiDAR-derived tree heights were not found to be significantly different (p < 0.05) from field measured tree heights and the absolute mean underestimation of LiDAR-height was 1.3 m. LiDAR-derived tree height estimates were found to be poorly related to tree volume and hence to harvester productivity. This was believed to be the result of the stand’s thinning history reducing the range of tree sizes i.e. removal of trees in the thinning operations. An attempt, therefore to estimate crown diameter from Quickbird imagery and or low density LiDAR was made which, in combination with LiDAR height, might be used to estimate tree volume and hence harvester productivity. Slope is a major terrain factor affecting harvester productivity. A study in Tasmania examined the ability of LiDAR to derive terrain slope over large areas and to use the derived slope data to model the effect of slope on the productivity of a self-levelling feller-buncher in order to predict its productivity for a wide range of slopes. Low intensity LiDAR (>3 points / m2) flown in 2011 over the study site was used to derive slope classes. A time and motion study carried out for the harvesting operation was used to evaluate the impact of tree volume (estimated from manual tree measurements) and slope on the feller-buncher productivity. The study found that productivity of the feller-buncher was significantly greater on moderate slope (11-18°) than on steep slope (18-27°). This difference in productivity resulted from operator technique differences related to felling. The productivity models were tested using LiDAR-derived slope and trees not used in the model development and were found to be able to accurately predict the effect of slope on the productivity of the feller-buncher. To better understand the drivers of harvesting productivity, a detailed comparative study of two single-grip harvesters was carried out in Australian Pinus radiata clearfell harvesting operations. Significant differences in productivity between the harvesters were found to be largely due to operator working technique differences. This factor cannot be determined through remote sensing. However, its influence can be reduced by using a general productivity model obtained from multiple operators.