ORCID Profile
0000-0002-5281-6111
Current Organisation
Scion
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Publisher: Informa UK Limited
Date: 05-02-2019
Publisher: Elsevier BV
Date: 04-2007
Publisher: Informa UK Limited
Date: 1996
Publisher: Oxford University Press (OUP)
Date: 11-2000
DOI: 10.1093/TREEPHYS/20.17.1157
Abstract: In 1986, four allopatric Eucalyptus species (E. camaldulensis Dehnh, E. saligna Smith, E. leucoxylon F. Muell and E. platypus Hook.) were planted together in a 480-mm rainfall zone, in 8-m wide contour belts as part of a plan to minimize waterlogging and secondary salinization. Throughout 1997, 1998 and 1999, there was significant inter-specific variation in predawn leaf water potential (Psi(pd)) however, maximum stomatal conductance (g(sm)) only differed significantly between species in mid to late summer. Relationships between g(sm) and Psi(pd) were significant and showed that stomata of E. camaldulensis were significantly more sensitive to Psi(pd), and presumably soil water potential, than stomata of E. leucoxylon or E. platypus. When applied to the Psi(pd) data, these relationships predicted that g(sm), and by inference transpiration, varied much less between species than Psi(pd). Diurnal measurements throughout the season confirmed this prediction, and showed that E. camaldulensis and E. saligna avoided drought by gaining access to deeper water, whereas E. leucoxylon and E. platypus maintained greater g(sm) at a given water stress than E. camaldulensis or E. saligna. Osmotic potentials measured after rehydration and water release curves of the leaves indicated that different mechanisms accounted for the apparent drought tolerance of E. leucoxylon and E. platypus. In summer, E. leucoxylon reduced osmotic potential at full and zero turgor by similar amounts compared with winter. In summer, E. platypus had a significantly lower bulk elastic modulus and relative water content at turgor loss point than E. camaldulensis, E. saligna or E. leucoxylon. This elastic adjustment resulted in a larger difference between osmotic potential at full and zero turgor in summer than in winter. The inherently low osmotic potential in E. leucoxylon and elastic adjustment in E. platypus resulted in turgor loss at a similar and significantly lower water potential than in E. camaldulensis or E. saligna. These results have implications for species selection for planting to manage groundwater recharge in areas prone to waterlogging and secondary salinization.
Publisher: Oxford University Press (OUP)
Date: 05-2005
DOI: 10.1093/TREEPHYS/25.5.571
Abstract: We used calorimetry to test whether there is a single general relationship between growth and respiration in shoots and roots of Eucalyptus globulus Labill. seedlings when stressed, irrespective of the type or severity of stress. We found that nitrogen (N) deprivation and salt treatment had no effect on the relationship between growth and respiration and little effect on absolute rates of respiration. Carbon-conversion efficiency (epsilonC) ranged from 0.7 to 0.9 for specific growth rates (R(SG)) greater than 0.3 day(-1). Above an R(SG) of 0.1 day(-1), epsilonC decreased gradually with decreasing R(SG) and between an R(SG) of 0- 0.1 day(-1), epsilonC decreased rapidly. We conclude that the relationship between epsilonC and R(SG) is not greatly affected by salt or N-deprivation stresses. Relationships between gross productivity and epsilonC may be generally applicable, in which case they could improve on the "flat-tax" approach to modeling net primary productivity from gross productivity while avoiding the complexity of more explicit models of plant respiration. However, the relationship between gross productivity and epsilonC was sensitive to temperature and the effect of temperature on epsilonC thus requires further investigation. Nitrogen deprivation caused large decreases in leaf area and shoot to root ratio, and mature leaves of N-deprived plants had lower intrinsic water-use efficiencies than leaves of plants well supplied with nutrients. Nitrogen deprivation increased apical dominance and most of the reduction in leaf area was the result of fewer secondary branches, although leaf size was also reduced. Our results suggest that N deprivation reduces productivity primarily by reducing sink size, rather than sink activity, and that apical dominance may be an important mechanism for maintaining adequate epsilonC in resource-limited conditions.
Publisher: Springer Science and Business Media LLC
Date: 1998
Publisher: Wiley
Date: 06-2021
DOI: 10.1002/HYP.14182
Abstract: In central Chile, many communities rely on water obtained from small catchments in the coastal mountains. Water security for these communities is most vulnerable during the summer dry season and, from 2010 to 2017, rainfall during the dry season was between 20% and 40% below the long‐term average. The rate of decrease in stream flow after a rainfall event is a good measure of the risk of flow decreasing below a critical threshold. This risk of low flow can be quantified using a recession coefficient ( α ) that is the slope of an exponential decay function relating flow to time since rainfall. A mathematical model was used to estimate the recession coefficient ( α ) for 142 rainstorm events (64 in summer 78 in winter) in eight monitored catchments between 2008 and 2017. These catchments all have a similar geology and extend from 35 to 39 degrees of latitude south in the coastal range of south‐central Chile. A hierarchical cluster analysis was used to test for differences between the mean value of α for different regions and forest types in winter and summer. The value of α did not differ ( p 0.05) between catchments in winter. Some differences were observed during summer and these were attributed to morphological differences between catchments and, in the northernmost catchments, the effect of land cover (native forest and plantation). Moreover, α for catchments with native forest was similar to those with pine plantations, although there was no difference ( p 0.05) between these and Eucalyptus plantations. The recession constant is a well‐established method for understanding the effect of climate and disturbance on low flows and baseflows and can enhance local and regional analyses of hydrological processes. Understanding the recession of flow after rainfall in small headwater catchments, especially during summer, is vital for water resources management in areas where the establishment of plantations has occurred in a drying climate.
Publisher: Springer Science and Business Media LLC
Date: 25-02-2011
Publisher: Elsevier BV
Date: 12-2020
Publisher: Wiley
Date: 10-2004
Publisher: National Inquiry Services Center (NISC)
Date: 25-06-2015
Publisher: Oxford University Press (OUP)
Date: 05-1996
DOI: 10.1093/TREEPHYS/16.5.469
Abstract: In August 1990, a 2-ha plantation was established in an area where rainfall (about 515 mm year(-1)) was insufficient to meet evaporative demand. On nine occasions between September 1991 and April 1993, pressure-volume curves were constructed for irrigated and rainfed Eucalyptus globulus ssp. globulus Labill. and E. nitens (Deane and Maiden) Maiden trees. During the experiment, rainfed trees experienced six periods when predawn water potential was significantly lower than that of irrigated trees. In early spring of 1991 and 1992, osmotic potentials at full turgor and turgor loss point in the irrigated E. nitens were significantly lower than at other times of the year, probably because of winter hardening. Water stress reduced osmotic potential and increased bulk elastic modulus in E. nitens, whereas the reverse occurred in E. globulus. However, treatment differences with respect to changes in osmotic and elastic properties were commonly overshadowed by interspecific differences. These were most apparent at the end of the sixth period of water stress when osmotic potentials at full and zero turgor were significantly higher and bulk elastic modulus and relative water content at turgor loss point were significantly lower in E. globulus than in E. nitens. We conclude that the drought-tolerance responses of E. globulus make it a more suitable species than E. nitens for establishment on sites where moderate water stress is experienced.
Publisher: Elsevier BV
Date: 12-2006
Publisher: Oxford University Press (OUP)
Date: 19-02-2009
Abstract: Eucalyptus globulus Labill., a globally significant plantation species, is grown commercially in a multiple rotation framework. Second and subsequent crops of E. globulus may be established either by allowing the cut stumps to resprout (commonly referred to as coppice) or by replanting a new crop of seedlings. Currently, long-term growth data comparing coppice and seedling productivity in second or later rotations in southern Australia is limited. The capacity to predict productivity using these tools is dependent on an understanding of the physiology of seedlings and coppice in response to light, water and nutrient supply. In this study, we compared the intrinsic (independent of the immediate environment) and native (dependent on the immediate environment) physiology of E. globulus coppice and second-generation seedlings during their early development in the field. Coppice not only grew more rapidly, but also used more water and drew on stored soil water to a depth of at least 4.5 m during the first 2 years of growth, whereas the seedlings only accessed the top 0.9 m of the soil profile. During the same period, there was no significant difference between coppice and seedlings in either their stomatal response to leaf-to-air vapour pressure difference (D) or intrinsic water-use efficiency CO(2)- and light-saturated rates of photosynthesis were greater in seedlings than that in coppice as were the quantum yield of photosynthesis and total leaf chlorophyll content. Thus, at a leaf scale, seedlings are potentially more productive per unit leaf area than coppice during early development, but this is not realised under ambient conditions. The underlying cause of this inherent difference is discussed in the context of the allocation of resources to above- and below-ground organs during early development.
Publisher: MDPI AG
Date: 07-02-2020
DOI: 10.3390/F11020187
Abstract: The transpiration of Nothofagus glauca (Phil.) Krasser and advanced Pinus radiata D. Don. regeneration was measured in a fragment of native N. glauca forest. Over the eight months of this study, P. radiata contributed approximately 60% of the total stand transpiration. This was out of proportion with the approximately 34% of the stand sapwood area contributed by P. radiata. This was due to the significantly greater sap flux density of the P. radiata compared to the N. glauca between May and October. Though the results are from a small study conducted as part of a larger experiment, it is argued that they suggest that invasion by P. radiata may substantially increase the risk from climate change to reserves of N. glauca forest in the Maule region of central Chile. In some reserves of N. glauca forest, Forestal Arauco S.A. manually removed P. radiata that regenerated after the wildfire of January 2017. This was a costly operation and there is a need for indices to assess competition. The ratio of sapwood area to leaf area is suggested as a potential index for assessing competition to identify stands at risk.
Publisher: Wiley
Date: 12-1993
DOI: 10.1111/J.1439-0329.1993.TB00822.X
Abstract: The spatial arrangement of discolouration and decay from artificial wounds in Eucalyptus regnans was consistent with the CODIT model of s higo and m arx (1977) up to 2 years after wounding. Discolouration and decay had spread more from wounds which remained bark‐covered than from those where the bark was removed from the bole.
Publisher: Springer Science and Business Media LLC
Date: 1999
Publisher: Oxford University Press (OUP)
Date: 06-2011
Abstract: Although hydraulic redistribution has been observed for a range of tree species, including Eucalyptus kochii subsp. borealis (C. Gardner) D. Nicolle, there is limited direct evidence that water taken up by deep roots in moist soil is in fact exuded by shallow roots in dry soil. This paper reports an experiment designed to test this hypothesis. Water enriched with deuterium was added to the groundwater via a slotted tube at 4.5 m depth below 5-year-old E. kochii subsp. borealis trees. Nocturnal sap flow increased markedly immediately after deep irrigation, indicating that the trees were using water from this depth. Two weeks later, s les of surface soil and xylem water were found to contain levels of deuterium up to 30% higher than soils and xylem water from a control plot upslope of the main treatment plot. This is strong evidence that trees used groundwater and that efflux of important amounts of hydraulically redistributed water occurred via the roots of E. kochii subsp. borealis.
Publisher: Elsevier BV
Date: 2023
Publisher: Elsevier BV
Date: 09-2020
Publisher: Springer Science and Business Media LLC
Date: 14-07-2011
Publisher: Oxford University Press (OUP)
Date: 28-09-2009
Abstract: Information on how vegetation adapts to differences in water supply is critical for predicting vegetation survival, growth and water use, which, in turn, has important impacts on site hydrology. Many field studies assess adaptation to water stress by comparing between disparate sites, which makes it difficult to distinguish between physiological or morphological changes and long-term genetic adaptation. When planting trees into new environments, the phenotypic adaptations of a species to water stress will be of primary interest. This study examined the response to water availability of Eucalyptus kochii ssp. borealis (C. Gardner) D. Nicolle, commonly integrated with agriculture in south-western Australia for environmental and economic benefits. By choosing a site where the groundwater depth varied but where climate and soil type were the same, we were able to isolate tree response to water supply. Tree growth, leaf area and stand water use were much larger for trees over shallow groundwater than for trees over a deep water table below a silcrete hardpan. However, water use on a leaf area basis was similar in trees over deep and shallow groundwater, as were the minimum leaf water potential observed over different seasons and the turgor loss point. We conclude that homeostasis in leaf water use and water relations was maintained through a combination of stomatal control and adjustment of sapwood-to-leaf area ratios (Huber value). Differences in the Huber value with groundwater depth were associated with different sapwood-specific conductivity and water use on a sapwood area basis. Knowledge of the coordination between water supply, leaf area, sapwood area and leaf transpiration rate for different species will be important when predicting stand water use.
Publisher: Informa UK Limited
Date: 15-05-2019
Publisher: Elsevier BV
Date: 11-2011
Publisher: Elsevier BV
Date: 12-2011
Publisher: Informa UK Limited
Date: 1999
Publisher: Elsevier BV
Date: 12-2009
Publisher: Wiley
Date: 05-1994
Publisher: Springer Science and Business Media LLC
Date: 12-2003
Publisher: Elsevier BV
Date: 02-2023
Publisher: Elsevier BV
Date: 02-2002
Publisher: IEEE
Date: 26-09-2020
Publisher: Copernicus GmbH
Date: 27-10-2022
DOI: 10.5194/HESS-26-5357-2022
Abstract: Abstract. The effect of Eucalyptus plantations on water balance is thought to be more severe than for commercial alternatives such as Pinus species. Although this perception is firmly entrenched, even in the scientific community, only four direct comparisons of the effect on the water balance of a Eucalyptus species and a commercial alternative have been published. One of these, from South Africa, showed that Eucalyptus grandis caused a larger and more rapid reduction in streamflow than Pinus patula. The other three, one in South Australia and two in Chile, did not find any significant difference between the annual evapotranspiration of E. globulus and P. radiata after canopy closure. While direct comparisons are few, there are at least 57 published estimates of annual evapotranspiration of either the Eucalyptus or Pinus species. This paper presents a meta-analysis of these published data. Zhang et al. (2004) fitted a relationship between the vegetation evaporation efficiency and the climate wetness index to published data from catchment studies and proposed this approach for comparing land uses. We fitted this model to the published data for Eucalyptus and Pinus and found that the single parameter of this model did not differ significantly between the two genera (p=0.48). This was also the case for all parameters of an exponential relationship between evapotranspiration and rainfall (p=0.589) and a linear relationship between the vegetation evaporation index and rainfall (p=0.155). These results provide strong evidence that, for a given climate wetness index, the two genera have similar annual water use. The residuals compared to the model of Zhang et al. (2004) were significantly correlated with soil depth for Eucalyptus, but this was not the case for Pinus. For Eucalyptus, the model overestimates the vegetation evaporation efficiency on deep soils and underestimates the vegetation evaporation efficiency on shallow soils.
Publisher: Oxford University Press (OUP)
Date: 08-1996
DOI: 10.1093/TREEPHYS/16.8.697
Abstract: Sapflow sensors were used to investigate variation in sapflow velocity at different positions in the sapwood of three-year-old Eucalyptus globulus ssp. globulus Labill. trees. Sapflow velocity was measured at 5-mm intervals across the sapwood by moving two probe sets simultaneously on two opposite radii. Another probe set placed in a fixed position at right angles to the first two sets acted as a control. A sapflow velocity ratio was defined as the velocity given by each moving sensor ided by that given by the static sensor. Correlation between observations of sapflow velocity at different positions exceeded 95%, and the ratio of velocity between any pair of sensors was constant. We observed radial variation in sapflow velocity across the sapwood with the lowest velocities at the center of the tree. Variation due to sensor position was high implying the need for large numbers of sensors for accurate estimates of sap flux. To overcome this need, we used a correction coefficient, namely a simple weighted average of the sapflow ratios with depth in the sapwood, for each fixed sensor. We recommend the use of three probe sets to estimate the correction coefficient. Subsequently, two probe sets can be placed at two fixed positions for routine measurements of sap flux.
Publisher: Oxford University Press (OUP)
Date: 26-05-2010
Abstract: This paper reports on variation in leaf area index (L) in five Eucalyptus globulus Labill. plantations in response to application of nitrogen, thinning at age 2 years and variation in climate wetness index (the ratio of rainfall to potential evaporation). Observed L is compared with: (i) L predicted to optimize net primary productivity for a given average annual temperature, annual water use and potential evaporation (L(opt)) and (ii) L calculated as a linear function of climate wetness index (L(eq)). L peaked in fertilized plots at between 4 and 5 years of age or immediately after canopy closure. The value of L from canopy closure to age 8 years was not strongly related to annual rainfall or climate wetness index. At two sites with total soil nitrogen <1.2 mg g(-)(1), L in fertilized plots was about two units greater than in unfertilized plots. This difference persisted until measurements ended in 2004 when the trees were 8 years old. The L of plots thinned to 300 and 600 stems ha(-)(1) at age 2 years recovered quickly and was not significantly different from L in unthinned plots when the trees were 8 years old. L(opt) was a good predictor of the leaf area index of 8-year-old plots of E. globulus when nitrogen and phosphorus were non-limiting (model efficiency (EF) was 0.5). For the same plots, L(eq) underestimated observed L by an average of two units, and the model efficiency was low (-3.25). Data from two nitrogen-limited sites demonstrated that for fertilized plots L(opt) (EF = 0.6) was a much better predictor of L than L(eq) (EF = -3.36). At the same sites, L(eq) (EF = 0.42) was a better model for predicting L of unfertilized plots than L(opt) (-3.59). These results provide evidence that comparing observed L with L(opt) can identify stands limited by factors other than growing climate.
Publisher: Elsevier BV
Date: 05-2004
Publisher: MDPI AG
Date: 09-03-2022
Abstract: Wildfires are an important disturbance affecting catchments’ soil and hydrological processes within. Wildfires are predicted to increase in both frequency and severity under climate change. Here, we present measurements of tritium (3H) in surface water of three streams before and after the ‘las Máquinas’ megafire of January 2017 in central Chile and streamflow metrics. Mean transit times (MTTs) of water were calculated in three coastal catchments with the Mediterranean climate type, covered by native forest, a mixture of native forest and Pinus radiata D. Don, and P. radiata. Lumped parameter models (LPMs) were used to obtain MTTs. Tritium activities from 2012 to 2018 ranged from 0.597 to 0.927 Tritium Units (TU), with the lowest TU activity in 2018. These 3H concentrations indicated water ages from 5 to 30 years. Following the fire, peak flows and baseflow have increased in two catchments but decreased in the third. Even though we have seen changes in the hydrological responses within the three catchments, pre- and post-fire MTT values were not significantly different. Therefore, there is no conclusive evidence of hydrological changes at the groundwater level due to wildfire at this early stage. However, since the MTT ranges from 5 to 30 years, it is likely that more time is required for the changes in the hydrograph to be clearly reflected in the tritium signal even though there are noticeable changes in streamflow metrics such as runoff and baseflow. Within the following years from this study, a s ling schedule to continue to investigate both the long-term drought and the effect of wildfire on these catchments will be maintained.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Oxford University Press (OUP)
Date: 10-1999
DOI: 10.1093/TREEPHYS/19.12.831
Abstract: For analysis of carbon isotope discrimination in wood, cellulose or holocellulose is often preferred to whole tissue because of the variability in isotopic composition of different wood components and the relative immobility of cellulose. Most currently used methods for the preparation of wood components for stable isotope analysis (e.g., the Jayme-Wise method) produce a residue of holocellulose. The Jayme-Wise method was initially developed to extract holocellulose from small (~1 g) s les of wood, and, despite subsequent modifications, the method requires specialized glassware, considerable time and entails the risk of s le loss. For carbon isotope analysis, we adapted an acid-catalyzed solvolytic method for preparing crude cellulose by treating wood meal with acidified di-glycol methyl ether (diglyme). The one-step process requires no special glassware, is complete within 24 hours and enables over 100 s les to be processed in a day. This method gives similar delta(13)C values to the Jayme-Wise method for wood of Eucalyptus globulus Labill., Pinus radiata D. Don and Pinus pinaster Ait. The relationship between delta(13)C of wood and crude cellulose is as strong as that observed between wood and alpha-cellulose and stronger than that observed between wood and holocellulose in other species. These relationships suggest that variation in delta(13)C of wood may result from hemicellulose and that analysis of stable carbon isotopes in crude cellulose is preferable. If the consistent -0.3 bias in the value of delta(13)C of cellulose resulting from residual lignin is corrected for, then the relationship between delta(13)C of wood and crude cellulose may be used to predict delta(13)C of cellulose from a small sub-s le. The method is well suited to species with low concentrations of extractives, but further testing is needed to assess its general applicability.
Publisher: Elsevier BV
Date: 02-2000
Publisher: Springer Science and Business Media LLC
Date: 2001
Abstract: In previous work, we provided evidence from sap flow measurements that when root systems span soil layers of different moisture content, water is redistributed by roots in the direction of the difference in water potential. In addition to the phenomenon termed "hydraulic lift", where water is redistributed from depth to dry topsoil, the process of "hydraulic redistribution" includes downward transfer of water when the surface layers of soils with low permeability become wet after rainfall. In this paper, we support our previous findings with evidence from measurements of soil water and estimate the quantities of water transferred to depth following rain. Amounts of water stored at depth are not likely to be significant for drought avoidance by plants. However, downward transfer of water may be important to plant establishment and the reduction of waterlogging in certain soil types.
Publisher: Springer Science and Business Media LLC
Date: 26-10-2015
Publisher: CSIRO Publishing
Date: 1999
DOI: 10.1071/PP98023
Abstract: This paper incorporates the cumulative effect of water stress, in a phenomenological model of stomatal conductance of upper canopy foliage (gsu) for Eucalyptus globulus and Eucalyptus nitens. Maximum observed stomatal conductance of irrigated trees was moderated by three functions describing the response of gsu to light, air temperature and vapour pressure deficit. This model explained 70% of the variation in gsu of irrigated trees using the same parameter values for both species. Daily total conductance was calculated for rainfed (Gsu,R) and irrigated (Gsu,I) trees. Linear relationships between the ratio of Gsu,R/G su,I (f(W)) and pre-dawn water potential explained only 46 and 30%, respectively, of variation in f(W) for E. globulus and E. nitens. The average value of pre-dawn water potential for the preceding x days (Sψx) was calculated for a range of values of x. When x was 8 for E. globulus and 20 for E. nitens a single exponential decay function accounted for 70% of variation in f(W) for both species. This result and the number of days over which it was necessary to calculate (Sψx) were consistent with previous studies of the leaf water relations, canopy and sapwood development, and stomatal behaviour of the two species.
Publisher: Elsevier BV
Date: 11-2011
Publisher: Wiley
Date: 04-2021
DOI: 10.1002/HYP.14047
Publisher: Wiley
Date: 10-12-2013
DOI: 10.1111/NPH.12064
Abstract: Plant survival during drought requires adequate hydration in living tissues and carbohydrate reserves for maintenance and recovery. We hypothesized that tree growth and hydraulic strategy determines the intensity and duration of the ‘physiological drought’, thereby affecting the relative contributions of loss of hydraulic function and carbohydrate depletion during mortality. We compared patterns in growth rate, water relations, gas exchange and carbohydrate dynamics in three tree species subjected to prolonged drought. Two E ucalyptus species ( E . globulus , E . smithii ) exhibited high growth rates and water‐use resulting in rapid declines in water status and hydraulic conductance. In contrast, conservative growth and water relations in P inus radiata resulted in longer periods of negative carbon balance and significant depletion of stored carbohydrates in all organs. The ongoing demand for carbohydrates from sustained respiration highlighted the role that duration of drought plays in facilitating carbohydrate consumption. Two drought strategies were revealed, differentiated by plant regulation of water status: plants maximized gas exchange, but were exposed to low water potentials and rapid hydraulic dysfunction and tight regulation of gas exchange at the cost of carbohydrate depletion. These findings provide evidence for a relationship between hydraulic regulation of water status and carbohydrate depletion during terminal drought.
Publisher: Wiley
Date: 02-2000
Publisher: Informa UK Limited
Date: 02-10-2014
Publisher: Elsevier BV
Date: 06-2010
Publisher: Wiley
Date: 05-11-2004
No related grants have been discovered for Donald White.