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R. A. Falkiner E. K. S. Nambiar P. J. Polglase S. Theiveyanathan L. G. Stewart 《Agroforestry Systems》2006,67(3):279-291
Planting trees, in farm forestry enterprises, to control rising watertables is an increasing practice for both economic and
environmental benefits. One central biophysical issue which determines the effectiveness of trees to control groundwater is
the ability of trees to grow roots through degraded soils and take up groundwater. We investigated the effect of soil properties,
especially the presence of shallow watertables and site preparation practice, on the vertical and horizontal distributions
of Eucalyptus grandis W. Hill ex Maiden and Corymbia maculata (Hook.) K.D. Hill and L.A.S. Johnson roots. In order to improve the reliability of root data, we measured root growth and
distribution by three different methods – (i) number of roots intercepting the vertical plane of the soil profile, (ii) root
length density in soil cores taken at different depths but in the horizontal plane of the profile, and (iii) root length density
in soil cores in the vertical plane at different radial positions from trees and compared the results. Two experimental sites
were established in flood-irrigated, farm forestry plantations on contrasting soils in the Murray Riverina region of south-eastern
Australia. At one site (Norwood Park), we studied a 58-month-old stand of E. grandis growing in clay loam overlaying medium clay, saline, sodic and alkaline subsoil with a saline (11.5 dS m−1) watertable at 2.8 m depth. Here, there were few roots growing above the watertable. The Karawatha site had adjacent stands
of 46-month old E. grandis and C. maculata growing in a sandy, neutral and non-saline soil with a shallow (3.1 m deep) non-saline (2.8 dS m−1) watertable. Here roots proliferated above the watertable in both species but to a much greater extent under C. maculata than under E. grandis. Root distributions in the surface soil were similar at all sites but differences in root growth in the capillary zones paralleled
differences in groundwater uptake by trees. We conclude (i) that appropriate matching of species with site characteristics,
especially soil and groundwater properties, will enhance tree growth and groundwater uptake and (ii) that extensive planting
of C. maculata over non-saline watertables maximises the chances of achieving the multiple objectives of regional groundwater control, fast
growth rates and reduced irrigation demand. 相似文献
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Keryn Paul Phil Polglase Peter Snowdon Tivi Theiveyanathan John Raison Tim Grove Stan Rance 《New Forests》2006,31(3):513-533
There is a need to calibrate models for carbon accounting in forest systems if they are to be applied for carbon trading and
off-set schemes. One such model, Full Carbon Accounting Model (FullCAM), calculates stem mass by taking annual inputs of tree
growth in stem volume and multiplying these by basic stem wood density. Stem mass is then multiplied by user-entered coefficients
to determine the mass of other tree components. Using datasets of Pinus radiata and Eucalyptus globulus that comprised of between 73 and 187 observations, we determined empirical relationships that can be used in FullCAM to relate
basic stem wood density to stand age, and masses of bark, foliage or branches to mass of stem wood for these two species.
All fitted relationships were highly significant (p < 0.001), explaining between 35 and 89% of the variance. These calibrations were then tested using three case studies where
data on volume yield curves and repeated measures of biomass of stand components were available: one of P. radiata and two of E. globulus. Although accumulation of biomass in foliage and branches were not well predicted by the model, sensitivity analysis showed
that this was relatively unimportant to total carbon storage because of the dominance of the stem, particularly once the stand
is older than 5 years. Indeed, FullCAM accounted for 99% of the variance in measured above-ground biomass at all three sites
because calibrations for the mass of stem was reasonably well constrained. Uncertainty analysis showed that despite the standard
errors of parameters used in relationships for basic density and biomass partitioning, and for estimates of carbon contents
of tree components, we can be 95% confident that sequestration of carbon in trees and debris of Pinus radiata and Eucalyptus globulus plantations are, on average, within 13% of that predicted by FullCAM.
Ensis is a joint venture between CSIRO FFP P/L and Scion Australasia P/L 相似文献
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John Finlayson Andrew Bathgate Tivi Theiveyanathan Russell Crosbie Ziaul Hoque 《Agricultural Systems》2010,103(3):161-170
It has been widely suggested that changing land use from annual to perennial crops reduces land and stream degradation due to salinisation. However, annual crops are financially attractive and increases in perennials can reduce stream flows with adverse effects on stream values. As such, salinity control is likely to involve tradeoffs between public and private costs and benefits. This study quantifies the expected on-farm economic and catchment-level water yield and salinity effects of altering land use among trees, perennial pastures and cereals. The structure of a two stage linear-programming (LP) process is described. The first stage is the MIDAS farm-level model of mixed cropping and sheep enterprises which provides inputs to a second stage catchment-level LP. It was concluded that perennial pastures can be used in conjunction with trees as a stream salinity-management tool in low to intermediate rainfall areas in New South Wales. The results indicate that land-use decisions should be informed by site-specific information if adverse effects on streams are to be avoided. 相似文献
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David I. Forrester Swaminathan Theiveyanathan John J. Collopy Nico E. Marcar 《Forest Ecology and Management》2010
Significant increases in aboveground biomass production have been observed when Eucalyptus is planted with a nitrogen-fixing species due to increased nutrient availability and more efficient use of light. Eucalyptus and Acacia are among the most popular globally planted genera with the area of Eucalyptus plantations alone expanding to over 19 Mha over the past two decades. Despite this, little is known about how nutrition and light availability in mixed-species tree plantations influence water use and water use efficiency (WUE). This study examined to what extent water use and WUE have been influenced by increased resource availability and growth in mixed-species plantations. Monocultures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman and 1:1 mixtures of these species were planted. Growth and transpiration were measured between ages 14 and 15 years. Aboveground biomass increment (Mg ha−1) was significantly higher in mixtures (E. globulus; 4.8 + A. mearnsii; 0.9) than E. globulus (3.3) or A. mearnsii monocultures (1.6). Annual transpiration (mm) measured using the heat pulse technique was also higher in mixtures (E. globulus; 285 + A. mearnsii; 134) than in E. globulus (358) and A. mearnsii (217) monocultures. Mixtures exhibited higher WUE than monocultures due to significant increases in the WUE of E. globulus in mixtures (1.69 kg aboveground biomass per cubic metre water transpired) compared to monocultures (0.94). The differences in WUE appear to result from increases in canopy photosynthetic capacity and above- to belowground carbon allocation in mixtures compared to monocultures. Although further studies are required and operational issues need to be resolved, the results of this study suggest that mixed eucalypt–acacia plantations may be used in water-limited environments to produce a given amount of wood with less water than eucalypt monocultures. Alternatively, because mixtures can be more productive and use more water per unit land area (but use it more efficiently), they could be utilized in recharge zones where rising water tables and salinity result from the replacement of vegetation (fast growing trees) that uses higher quantities of water with vegetation (shallow rooted annual crops) that use lower quantities of water. 相似文献
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