Tree water sources over shallow, saline groundwater in the lower River Murray, south-eastern Australia: implications for groundwater recharge mechanisms

2006 ◽  
Vol 54 (2) ◽  
pp. 193 ◽  
Author(s):  
K. L. Holland ◽  
S. D. Tyerman ◽  
L. J. Mensforth ◽  
G. R. Walker
Keyword(s):  
Soil Water ◽  
Riparian Vegetation ◽  
Water Sources ◽  
Plant Water ◽  
Deep Soil ◽  
Saline Groundwater ◽  
Low Salinity ◽  
South Eastern ◽  
Eastern Australia ◽  
South Eastern Australia

The decline of riparian vegetation in the lower River Murray, south-eastern Australia, is associated with a reduction in flooding frequency, extent and duration, and increased salt accumulation. The plant water sources of healthy Eucalyptus largiflorens trees growing over highly saline (>40 dS m–1) groundwater were investigated during summer when water deficit is greatest. The study found low-salinity soil water overlying highly saline groundwater at most sites. This deep soil water, rather than the saline groundwater, was identified as the plant water source at most sites. Stable isotopes of water and water potential measurements were used to infer how the deep soil water was recharged. The low-salinity, deep soil water was recharged in the following two ways: (1) vertically through the soil profile or via preferential flow paths by rainfall or flood waters or (2) horizontally by bank recharge from surface water on top of the saline groundwater. Vertical infiltration of rainfall and floodwaters through cracking clays was important for trees growing in small depressions, whereas infiltration of rainfall through sandy soils was important for trees growing at the break of slope. Bank recharge was important for trees growing within ∼50 m of permanent and ephemeral water bodies. The study has provided a better understanding of the spatial patterns of recharge at a scale relevant to riparian vegetation. This understanding is important for the management of floodplain vegetation growing in a saline, semi-arid environment.

Effects of environmental conditions on the production of hypocotyl hairs in seedlings of Melaleuca ericifolia (swamp paperbark)

2008 ◽  
Vol 56 (7) ◽  
pp. 564 ◽  
Author(s):  
Randall W. Robinson ◽  
Paul I. Boon ◽  
Nina Sawtell ◽  
Elizabeth A. James ◽  
Robert Cross
Keyword(s):  
Environmental Conditions ◽  
Water Availability ◽  
Coastal Wetlands ◽  
Root Hairs ◽  
Harsh Environments ◽  
Low Salinity ◽  
South Eastern ◽  
Eastern Australia ◽  
Small Wetland ◽  
South Eastern Australia

The production of hypocotyl hairs in the early stages of seedling development can strongly influence the success with which plants recruit sexually in harsh environments. Although wetlands are one type of environment in which seedlings might be expected to develop hypocotyl hairs, there have been few studies of these structures in the woody aquatic plants. We investigated the production of hypocotyl hairs in Melaleuca ericifolia Sm., a small wetland tree widely distributed across swampy coastal areas of south-eastern Australia, in relation to water availability, salinity, temperature and light regime. Hypocotyl hairs were ~20 mm long × 30 μm wide; in contrast, root hairs were generally less than 5 mm long and 15 μm wide. Hypocotyl hairs were produced only under a narrow range of environmental conditions—low salinity, low water availability, moderate temperature, and darkness—and seedlings that failed to produce hypocotyl hairs did not survive. Since the conditions under which hypocotyl hairs were produced were at least as, and possibly even more, restricted than those required for successful germination of seeds, it is likely that the successful sexual recruitment of M. ericifolia would be rare and episodic under conditions existing in most coastal wetlands in south-eastern Australia.

Water content of a red-brown earth subjected to a range of agronomic vegetation options in south-eastern Australia

2001 ◽  
Vol 52 (5) ◽  
pp. 587 ◽  
Author(s):  
D. M. Whitfield
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Deficit ◽  
Soil Water Deficit ◽  
Water Deficits ◽  
South Eastern ◽  
Eastern Australia ◽  
Ground Water Recharge ◽  
South Eastern Australia

The management of ground water recharge in south-eastern Australia relies on the formulation of agricultural practices that utilise rainfall before it moves below the root-zone. Annual cycles of soil water content were therefore measured in a red-brown earth subjected to 5 fallow-free crop sequences, to 2 crop sequences that included fallow, and to 3 pastures. Changes in soil water content induced by wheat, barley, lupin, pea, safflower, canola, and fallow were compared with those of annual pasture and 2 monocultures of the deep-rooted perennials phalaris and lucerne in 3 years of study. Mean minimum soil water content (0–1.6 m) seen in December and May was approximately 355 mm in lucerne and phalaris, 410 mm in annuals (crops and pasture), and 475 mm in fallow. Corresponding soil water deficits appropriate to lucerne, annuals, and fallow were 185, 135, and 65 mm, respectively. Lucerne and annuals both removed approximately 85 mm water from the upper 0.6 m of the soil profile. Differences arose in the subsoil below 0.6 m, where lucerne, annuals, and fallow produced soil water deficits of approximately 100, 50, and 25 mm, respectively. The difference in soil water deficit of deep-rooted perennials and annuals was therefore caused by the extra 50 mm of water extracted by lucerne and phalaris below 0.6 m in the period September–December. The dry subsoil endured through summer to promote the storage, by soil, of rainfall in winter. The data suggest that the spatial utility of an agronomic recharge control option in south-eastern Australia depends on the magnitude of the soil water deficit associated with the vegetation. The soil water deficit, relative to winter (May–August) rainfall, discriminates between areas where annuals suffice for recharge control, where lucerne and phalaris are required for recharge control, and where agronomic annuals and perennials are both conducive to high rates of drainage.

Keystone coleopterans? Colonization by wood-feeding elmids of experimentally immersed woods in south-eastern Australia

1998 ◽  
Vol 49 (1) ◽  
pp. 79 ◽  
Author(s):  
B. G. L. McKie ◽  
P. S. Cranston
Keyword(s):  
Surface Area ◽  
Wood Species ◽  
Riparian Vegetation ◽  
Native Forest ◽  
South Eastern ◽  
Eucalyptus Wood ◽  
Eastern Australia ◽  
Forest Streams ◽  
South Eastern Australia

Macroinvertebrates on immersed woods in streams in montane south-eastern Australia respond to differences in wood taxa, according to a 4-month colonization study of experimentally positioned sticks. Xylophagous elmids (Coleoptera : Elmidae) strongly preferred local native Eucalyptus over other types of wood including non-native softer timbers (Pinus and Alnus). Where gouging elmids were abundant (in native forest streams with native riparian vegetation), immersed Eucalyptus wood supported high abundances of other macroinvertebrates; in their absence (in open grassland streams), Eucalyptus supported few other macroinvertebrates. Macroinvertebrate-gouged channels were present disproportionately on Eucalyptus sticks relative to other wood species. It is proposed that xylophagous elmid beetles are the principal macroinvertebrate modifiers of wood in these south-eastern Australian streams, where their gouging of channels increases surface area, thereby facilitating colonization by other macroinvertebrates and wood-decaying microorganisms and fungi.

scholarly journals Unexplained hydrogen isotope offsets complicate the identification and quantification of tree water sources in a riparian forest

2019 ◽  
Vol 23 (4) ◽  
pp. 2129-2146 ◽  
Author(s):  
Adrià Barbeta ◽  
Sam P. Jones ◽  
Laura Clavé ◽  
Lisa Wingate ◽  
Teresa E. Gimeno ◽  
...  
Keyword(s):  
Soil Water ◽  
Riparian Forest ◽  
Stream Water ◽  
Isotopic Fractionation ◽  
Growing Season ◽  
Water Sources ◽  
Source Water ◽  
Plant Water ◽  
Deep Soil ◽  
Plant Water Sources

Abstract. We investigated plant water sources of an emblematic refugial population of Fagus sylvatica (L.) in the Ciron river gorges in south-western France using stable water isotopes. It is generally assumed that no isotopic fractionation occurs during root water uptake, so that the isotopic composition of xylem water effectively reflects that of source water. However, this assumption has been called into question by recent studies that found that, at least at some dates during the growing season, plant water did not reflect any mixture of the potential water sources. In this context, highly resolved datasets covering a range of environmental conditions could shed light on possible plant–soil fractionation processes responsible for this phenomenon. In this study, the hydrogen (δ2H) and oxygen (δ18O) isotope compositions of all potential tree water sources and xylem water were measured fortnightly over an entire growing season. Using a Bayesian isotope mixing model (MixSIAR), we then quantified the relative contribution of water sources for F. sylvatica and Quercus robur (L.) trees. Based on δ18O data alone, both species used a mix of top and deep soil water over the season, with Q. robur using deeper soil water than F. sylvatica. The contribution of stream water appeared to be marginal despite the proximity of the trees to the stream, as already reported for other riparian forests. Xylem water δ18O could always be interpreted as a mixture of deep and shallow soil waters, but the δ2H of xylem water was often more depleted than the considered water sources. We argue that an isotopic fractionation in the unsaturated zone and/or within the plant tissues could underlie this unexpected relatively depleted δ2H of xylem water, as already observed in halophytic and xerophytic species. By means of a sensitivity analysis, we found that the estimation of plant water sources using mixing models was strongly affected by this δ2H depletion. A better understanding of what causes this isotopic separation between xylem and source water is urgently needed.

scholarly journals Unexplained hydrogen isotope offsets complicate the identification and quantification of tree water sources in a riparian forest

2019 ◽  
Author(s):  
Adrià Barbeta ◽  
Sam P. Jones ◽  
Laura Clavé ◽  
Lisa Wingate ◽  
Teresa E. Gimeno ◽  
...  
Keyword(s):  
Soil Water ◽  
Riparian Forest ◽  
Stream Water ◽  
Isotopic Fractionation ◽  
Growing Season ◽  
Water Sources ◽  
Source Water ◽  
Plant Water ◽  
Deep Soil ◽  
Plant Water Sources

Abstract. We investigated plant water sources of an emblematic refugial population of Fagus sylvatica (L.) in the Ciron river gorges in South-Western France using stable water isotopes. It is generally assumed that no isotopic fractionation occurs during root water uptake, so that the isotopic composition of xylem water effectively reflects that of source water. However, this assumption has been called into question by recent studies that found that, at least at some dates during the growing season, plant water did not reflect any mixture of the potential water sources. In this context, highly resolved datasets covering a range of environmental conditions could shed light on possible plant-soil fractionation processes responsible for this phenomenon. In this study, the hydrogen (δ2H) and oxygen (δ18O) isotope compositions of all potential tree water sources and xylem water were measured fortnightly over an entire growing season. Using a Bayesian isotope mixing model (MixSIAR), we then quantified the relative contribution of water sources for F. sylvatica and Quercus robur (L.) trees. Based on δ18O data alone, both species used a mix of top and deep soil water over the season, with Q. robur using soil water relatively deeper than F. sylvatica. The contribution of stream water appeared to be marginal despite the proximity of the trees to the stream, as already reported for other riparian forests. Xylem water δ18O could always be interpreted as a mixture of deep and shallow soil waters, but the δ2H of xylem water was often more depleted than the considered water sources. We argue that an isotopic fractionation in the unsaturated zone and/or within the plant tissues could underlie this unexpected relatively depleted δ2H of xylem water, as already observed in halophytic and xerophytic species. By means of a sensitivity analysis, we found that the estimation of plant water sources using mixing models was largely affected by this δ2H depletion. A better understanding of what causes this isotopic separation between xylem and source water is urgently needed.

Soil water extraction by dryland crops, annual pastures, and lucerne in south-eastern Australia

2001 ◽  
Vol 52 (2) ◽  
pp. 183 ◽  
Author(s):  
J. F. Angus ◽  
R. R. Gault ◽  
M. B. Peoples ◽  
M. Stapper ◽  
A. F. van Herwaarden
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Crop Management ◽  
Water Extraction ◽  
South Eastern ◽  
Eastern Australia ◽  
Soil Water Extraction ◽  
The Mean ◽  
Dryland Crops ◽  
South Eastern Australia

The extraction of soil water by dryland crops and pastures in south-eastern Australia was examined in 3 studies. The first was a review of 13 published measurements of soil water-use under wheat at several locations in southern New South Wales. Of these, 8 showed significantly more water extracted by crops managed with increased nitrogen supply or growing after a break crop. The mean additional soil water extraction in response to break crops was 31 mm and to additional N was 11 mm. The second study used the SIMTAG model to simulate growth and water-use by wheat in relation to crop management at Wagga Wagga. The model was set up to simulate crops that produced either average district yields or the potential yields achievable with good management. When simulated over 50 years of weather data, the combined water loss as drainage and runoff was predicted to be 67 mm/year for poorly managed crops and 37 mm for well-managed crops. Water outflow was concentrated in 70% of years for the poorly managed crops and 56% for the well-managed crops. In those years the mean losses were estimated to be 95 mm and 66 mm, respectively. The third study reports soil water measured twice each year during a phased pasture–crop sequence over 6.5 years at Junee. Mean water content of the top 2.0 m of soil under a lucerne pasture averaged 211 mm less than under a subterranean clover-based annual pasture and 101 mm less than under well-managed crops. Collectively, these results suggest that lucerne pastures and improved crop management can result in greater use of rainfall than the previous farming systems based on annual pastures, fallows, and poorly managed crops. The tactical use of lucerne-based pastures in sequence with well-managed crops can help the dewatering of the soil andreduce or eliminate the risk of groundwater recharge.

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