Seasonal responses of xylem sap velocity to VPD and solar radiation during drought in a stand of native trees in temperate Australia

2004 ◽  
Vol 31 (5) ◽  
pp. 461 ◽  
Author(s):  
Melanie J. B. Zeppel ◽  
Brad R. Murray ◽  
Craig Barton ◽  
Derek Eamus
Keyword(s):  
Solar Radiation ◽  
Water Use ◽  
Xylem Sap ◽  
Spatial Models ◽  
Vapour Pressure Deficit ◽  
Hysteresis Curve ◽  
Eastern Australia ◽  
Eucalyptus Crebra ◽  
Vegetation Water ◽  
Remnant Forest

Xylem sap velocity of two dominant tree species, Eucalyptus crebra F. Muell. and Callitris glaucophylla J. Thompson & L.A.S. Johnson, in a native remnant forest of eastern Australia was measured in winter and summer during a prolonged (> 12 months) and extensive drought. The influence of vapour pressure deficit (VPD) and solar radiation levels on the velocity of sap was determined. Pronounced hysteresis in sap velocity was observed in both species as a function of VPD and solar radiation. However, the rotation of the hysteresis curve was clockwise for the response of sap velocity to VPD but anti-clockwise in the response of sap velocity to radiation levels. A possible reason for this difference is discussed.The degree of hysteresis (area bounded by the curve) was larger for the VPD response than the response to solar radiation and also varied with season. A simple linear model was able to predict sap velocity from knowledge of VPD and solar radiation in winter and summer. The consistent presence of hysteresis in the response to sap velocity to VPD and solar radiation suggests that large temporal and spatial models of vegetation water use may require some provision for the different responses of sap velocity, and hence water use, to VPD and solar radiation, between morning and afternoon and between seasons.

Effect of water stress on potato growth, yield and water use in a hot and a cool tropical climate

1990 ◽  
Vol 114 (3) ◽  
pp. 321-334 ◽  
Author(s):  
I. Trebejo ◽  
D. J. Midmore
Keyword(s):  
Solar Radiation ◽  
Water Use ◽  
Dry Matter ◽  
Conversion Coefficient ◽  
Growth Yield ◽  
Vapour Pressure Deficit ◽  
Yield Reduction ◽  
Hot Season ◽  
Intercepted Solar Radiation ◽  
Potato Growth

SUMMARYIrrigation experiments are described in which three cultivars were subjected to varying degrees of drought in the cool and hot seasons in Lima, Peru. The most severely draughted plots received, on average, 20% and 35% less water than the well-watered control plots, resulting in 20% and 52% yield reduction in the cool and hot seasons, respectively. Average fresh tuber yields ranged, according to cultivar, from 1370 to 2450 g/m2 in the summer and from 2800 to 4450 g/m2 in the winter, with tuber dry-matter percentages of c. 17% and 20%, respectively. The production of total dry matter per unit intercepted solar radiation (the conversion coefficient, estimated from the slope of the regression, in g/MJ) was markedly less during the hot season but, regressed on a photo thermal quotient ∑((MJ/m2)/(°C > 4·5°C)), a common relationship across seasons was achieved. The conversion coefficient was less in draughted than in well-watered plots, more so in the hot season.Crop transpirational and evapotranspirational water use efficiencies (WUE) were less in the hot season largely because of the greater saturation vapour-pressure deficit. However, because of greater harvest index (HI) and more-efficient interception of solar radiation per unit of applied water by draughted than by well-watered plots in the summer, and despite a lower conversion coefficient, draughted plots showed greater WUE. Based on total water applied and final fresh tuber yields, WUE was, on average, 3·9 and 12·4 kg/m3 in the hot and cool seasons, respectively, values close to the extremes of the range of published values. Low HI in the summer was, to some extent, responsible for this seasonal difference.

Regulation of canopy conductance and transpiration and their modelling in irrigated grapevines

2003 ◽  
Vol 30 (6) ◽  
pp. 689 ◽  
Author(s):  
Ping Lu ◽  
Isa A. M. Yunusa ◽  
Rob R. Walker ◽  
Warren J. Müller
Keyword(s):  
Solar Radiation ◽  
Sap Flow ◽  
Heat Dissipation ◽  
Xylem Sap ◽  
Vapour Pressure Deficit ◽  
Vitis Vinifera L ◽  
Canopy Conductance ◽  
Xylem Sap Flow ◽  
Highly Correlated ◽  
Monteith Equation

Whole-vine transpiration was estimated for well-watered nine-year-old Sultana grapevines (Vitis vinifera L. cv. Sultana) from xylem sap flow measured with Granier's heat-dissipation probes. Canopy conductance of the grapevine was calculated by inverting the Penman–Monteith equation. Transpiration from grapevine canopies was strongly controlled by the canopy conductance. Canopy conductance decreased exponentially with increasing vapour pressure deficit (VPD) except in the morning when solar radiation was less than 200 W m–2 and the canopy conductance was predominantly limited by the solar radiation. A non-linear model of canopy conductance as a function of the solar radiation and VPD explained > 90% of the variation observed in canopy conductance. Under contrasting VPD conditions (daytime maximum of 3 kPa vs 8 kPa), grapevines were able to regulate their canopy conductance from 0.006 to 0.001 m s–1 to maintain a near constant transpiration. Whole-canopy transpiration calculated from modelled canopy conductance using the Penman–Monteith equation was highly correlated with the measured transpiration (sap flow) values over the range of 0–0.20 mm h–1 (R2 > 0.85). Cross-validation shows that these mechanistic models based on solar radiation and VPD provide good predictions of canopy conductance and transpiration under the conditions of the study.

Quantification of wheat water-use efficiency at the shire-level in Australia

2010 ◽  
Vol 61 (1) ◽  
pp. 1 ◽  
Author(s):  
A. Doherty ◽  
V. O. Sadras ◽  
D. Rodriguez ◽  
A. Potgieter
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Wheat Yield ◽  
Vapour Pressure Deficit ◽  
Diffuse Radiation ◽  
Latitudinal Gradients ◽  
Eastern Australia ◽  
Use Efficiency ◽  
Yield Formation ◽  
Seasonal Water Use

In eastern Australia, latitudinal gradients in vapour pressure deficit (VPD), mean temperature (T), photosynthetically active radiation (PAR), and fraction of diffuse radiation (FDR) around the critical stage for yield formation affect wheat yield and crop water-use efficiency (WUE = yield per unit evapotranspiration). In this paper we combine our current understanding of these climate factors aggregated in a normalised phototermal coefficient, NPq = (PAR· FDR)/(T · VPD), with a shire-level dynamic model of crop yield and water use to quantify WUE of wheat in 245 shires across Australia. Three measures of WUE were compared: WUE, the ratio of measured yield and modelled evapotranspiration; WUEVPD, i.e. WUE corrected by VPD; and WUENPq, i.e. WUE corrected by NPq. Our aim is to test the hypothesis that WUENPq suits regional comparisons better than WUE or WUEVPD. Actual median yield at the shire level (1975–2000) varied from 0.5 to 2.8 t/ha and the coefficient of variation ranged from 18 to 92%. Modelled median evapotranspiration varied from 106 to 620 mm and it accounted for 42% of the variation in yield among regions. The relationship was non-linear, and yield stabilised at ~2 t/ha for evapotranspiration above 343 mm. There were no associations between WUE and rainfall. The associations were weak (R2 = 0.09) but in the expected direction for WUEVPD, i.e. inverse with seasonal rainfall and direct with off-season rainfall, and strongest for WUENPq (R2 = 0.40).We suggest that the effects of VPD, PAR, FDR, and T, can be integrated to improve the regional quantification of WUE defined in terms of grain yield and seasonal water use.

scholarly journals Trehalose induces tomato defenses and increases drought tolerance and bacterial wilt disease resistance

2021 ◽  
Author(s):  
April M MacIntyre ◽  
Valerian Meline ◽  
Zachary Gorman ◽  
Steven P Augustine ◽  
Carolyn J Dye ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Stomatal Conductance ◽  
Water Use ◽  
Bacterial Wilt ◽  
Xylem Sap ◽  
Wilt Disease ◽  
Tomato Plants ◽  
Bacterial Wilt Disease ◽  
Infected Tomato ◽  
Use Efficiency

Ralstonia solanacearum causes plant bacterial wilt disease, leading to severe crop losses. Xylem sap from R. solanacearum-infected tomato is enriched in host produced trehalose. Water stressed plants accumulate the disaccharide trehalose, which increases drought tolerance via abscisic acid (ABA) signaling networks. Because infected plants have reduced water flow, we hypothesized that bacterial wilt physiologically mimics drought stress, which trehalose could mitigate. Transcriptomic responses of susceptible vs. resistant tomato plants to R. solanacearum infection revealed differential expression of drought-associated genes, including those involved in ABA and trehalose metabolism. ABA was enriched in xylem sap from R. solanacearum-infected plants. Treating roots with ABA lowered stomatal conductance and reduced R. solanacearum stem colonization. Treating roots with trehalose increased ABA in xylem sap and reduced plant water use by reducing stomatal conductance and temporarily improving water use efficiency. Further, trehalose-treated plants were more resistant to bacterial wilt disease. Trehalose treatment also upregulated expression of salicylic acid (SA)-dependent defense genes, increased xylem sap levels of SA and other antimicrobial compounds, and increased wilt resistance of SA-insensitive NahG tomato plants. Additionally, trehalose treatment increased xylem concentrations of jasmonic acid and related oxylipins. Together, these data show that exogenous trehalose reduced both water stress and bacterial wilt disease and triggered systemic resistance. This suite of responses revealed unexpected linkages between plant responses to biotic and abiotic stress and suggests that that R. solanacearum-infected tomato plants produce more trehalose to improve water use efficiency and increase wilt disease resistance. In turn, R. solanacearum degrades trehalose as a counter-defense.

In-season crop classification using optical remote sensing with random forest over irrigated agricultural fields in Australia

2021 ◽  
Author(s):  
Zitian Gao ◽  
Danlu Guo ◽  
Dongryeol Ryu ◽  
Andrew Western
Keyword(s):  
Random Forest ◽  
Water Use ◽  
Landsat 8 ◽  
Irrigation Season ◽  
Yield Estimation ◽  
Cropping Season ◽  
Crop Type ◽  
Eastern Australia ◽  
Crop Classification ◽  
Type Classification

<p>Timely classification of crop types is critical for agronomic planning in water use and crop production. However, crop type mapping is typically undertaken only after the cropping season, which precludes its uses in later-season water use planning and yield estimation. This study aims 1) to understand how the accuracy of crop type classification changes within cropping season and 2) to suggest the earliest time that it is possible to achieve reliable crop classification. We focused on three main summer crops (corn/maize, cotton and rice) in the Coleambally Irrigation Area (CIA), a major irrigation district in south-eastern Australia consisting of over 4000 fields, for the period of 2013 to 2019. The summer irrigation season in the CIA is from mid-August to mid-May and most farms use surface irrigation to support the growth of summer crops. We developed models that combine satellite data and farmer-reported information for in-season crop type classification. Monthly-averaged Landsat spectral bands were used as input to Random Forest algorithm. We developed multiple models trained with data initially available at the start of the cropping season, then later using all the antecedent images up to different stages within the season. We evaluated the model performance and uncertainty using a two-fold cross validation by randomly choosing training vs. validation periods. Results show that the classification accuracy increases rapidly during the first three months followed by a marginal improvement afterwards. Crops can be classified with a User’s accuracy above 70% based on the first 2-3 months after the start of the season. Cotton and rice have higher in-season accuracy than corn/maize. The resulting crop maps can be used to support activities such as later-season system scale irrigation decision-making or yield estimation at a regional scale.</p><p>Keywords: Landsat 8 OLI, in-season, multi-year, crop type, Random Forest</p>

scholarly journals Soil moisture heterogeneity regulates water use in Populus nigra L. by altering root and xylem sap phytohormone concentrations

2020 ◽  
Vol 40 (6) ◽  
pp. 762-773 ◽  
Author(s):  
Jaime Puértolas ◽  
Marta Pardos ◽  
Carlos de Ollas ◽  
Alfonso Albacete ◽  
Ian C Dodd
Keyword(s):  
Soil Moisture ◽  
Water Use ◽  
Deficit Irrigation ◽  
Xylem Sap ◽  
Irrigation Scheduling ◽  
Populus Nigra ◽  
Soil Drying ◽  
Plant Water ◽  
Plant Water Use ◽  
Soil Moisture Heterogeneity

Abstract Soil moisture heterogeneity in the root zone is common both during the establishment of tree seedlings and in experiments aiming to impose semi-constant soil moisture deficits, but its effects on regulating plant water use compared with homogenous soil drying are not well known in trees. Pronounced vertical soil moisture heterogeneity was imposed on black poplar (Populus nigra L.) grown in soil columns by altering irrigation frequency, to test whether plant water use, hydraulic responses, root phytohormone concentrations and root xylem sap chemical composition differed between wet (well-watered, WW), and homogeneously (infrequent deficit irrigation, IDI) and heterogeneously dry soil (frequent deficit irrigation, FDI). At the same bulk soil water content, FDI plants had greater water use than IDI plants, probably because root abscisic acid (ABA) concentration was low in the upper wetter layer of FDI plants, which maintained root xylem sap ABA concentration at basal levels in contrast with IDI. Soil drying did not increase root xylem concentration of any other hormone. Nevertheless, plant-to-plant variation in xylem jasmonic acid (JA) concentration was negatively related to leaf stomatal conductance within WW and FDI plants. However, feeding detached leaves with high (1200 nM) JA concentrations via the transpiration stream decreased transpiration only marginally. Xylem pH and sulphate concentration decreased in FDI plants compared with well-watered plants. Frequent deficit irrigation increased root accumulation of the cytokinin trans-zeatin (tZ), especially in the dry lower layer, and of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), in the wet upper soil layer. Root hormone accumulation might explain the maintenance of high root hydraulic conductance and water use in FDI plants (similar to well-watered plants) compared with IDI plants. In irrigated tree crops, growers could vary irrigation scheduling to control water use by altering the hormone balance.

scholarly journals Water in a warmer world – is atmospheric evaporative demand changing in viticultural areas?

2019 ◽  
Vol 12 ◽  
pp. 01011
Author(s):  
H.R. Schultz
Keyword(s):  
Wind Speed ◽  
Solar Radiation ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Strong Increase ◽  
Simultaneous Increase ◽  
Evaporative Demand ◽  
Precipitation Patterns ◽  
Napa Valley ◽  
Rhone Valley

The predicted developments in climate are region-specific and adaptation can only be successful considering the regional characteristics with its diverse technical, environmental, economic and social implications. One of the key concerns for many regions is the availability of water through precipitation, the distribution of precipitation throughout the year, and possible changes in evaporative demand of the atmosphere and thus water use. From rising temperatures it is mostly assumed that water holding capacity of the atmosphere will increase in the future as a function of the Clausius-Clapeyron law, which predicts an increase in the saturation vapour pressure of the atmosphere of 6–7% per degree Celsius. As a consequence, a simultaneous increase in potential evapotranspiration (ETp, the amount of water that could potentially be evaporated from soils and transpired by plants due to changes in climatic factors such as temperature, vapour pressure deficit, radiation and wind speed) is assumed in many cases, which would alter soil and plant water relations. However, the same underlying principles also predict an increase in precipitation by 1–2% per degree warming. Additionally, model predictions for many regions forecast altered precipitation patterns and thus in combination with the possibility of increased ETp, farmers around the world fear an increase in the likelyhood of water deficit and a reduction in the availability of water for irrigation. Contrary to expectations, there have been reports on a reduction in evaporative demand worldwide despite increasing temperatures. In many cases this has been related to a decrease in solar radiation observed for many areas on earth including wine growing regions in Europe until the beginning of the 80th (global dimming) of the last century. However, since then, solar radiation has increased again, but ETp did not always follow and a worldwide decrease in wind speed and pan evaporation has been observed. In order to evaluate different grape growing regions with respect to observed changes on precipitation patterns and ETp, the data of seven wine-growing areas in five countries in the Northern and Southern hemisphere across a large climatic trans-sect were analyzed (Rheingau, Germany, Burgundy, Rhone Valley, France, Napa Valley, USA, Adelaide Hills, Tasmania, Australia, Marlborough, New Zealand) were analyzed. Precipitation patterns differed vastly between locations and showed very different trends over observation periods ranging from 23 to 60 years. The ETp has increased continuously in only two of the seven wine growing areas (Rheingau and Marlborough). In most other areas, ETp has been stable during winter and summer for at least 22 years (Rhone Valley, Napa Valley, Tasmania), sometimes much longer (45 years Adelaide Hills), and has been declining in Burgundy after a period of strong increase for the last 13 years. The potential underlying factors are discussed in relation to observed shifts in precipitation patterns.

Water use, competition, and crop production in low rainfall, alley farming systems of south-eastern Australia

2003 ◽  
Vol 54 (8) ◽  
pp. 751 ◽  
Author(s):  
Murray Unkovich ◽  
Kerrin Blott ◽  
Alex Knight ◽  
Ivan Mock ◽  
Abdur Rab ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Crop Yield ◽  
Farming Systems ◽  
Alley Farming ◽  
Annual Crop ◽  
South Eastern ◽  
Annual Crops ◽  
Eastern Australia ◽  
Perennial Shrubs

Annual crops were grown in alleys between belts of perennial shrubs or trees over 3–4 years at 3 sites across low rainfall (<450 mm) south-eastern Australia. At the two lower rainfall sites (Pallamana and Walpeup), crop grain yields within 2–5 m of shrub belts declined significantly with time, with a reduction equivalent to 45% over 9 m in the final year of cropping. At the third, wetter site (Bridgewater), the reduction in crop grain yields adjacent to tree belts was not significant until the final year of the study (12% over 11 m) when the tree growth rates had increased. The reductions in crop yield were associated with increased competition for water between the shrub or tree belts and the crops once the soil profile immediately below the perennials had dried. At all 3 sites during the establishment year, estimates of water use under the woody perennials were less than under annual crops, but after this, trends in estimates of water use of alley farming systems varied between sites. At Pallamana the perennial shrubs used a large amount of stored soil water in the second summer after establishment, and subsequently were predominantly dependent on rainfall plus what they could scavenge from beneath the adjacent crop. After the establishment year at the Walpeup site, water use under the perennial shrubs was initially 67 mm greater than under the annual crop, declining to be only 24 mm greater in the final year. Under the trees at Bridgewater, water use consistently increased to be 243 mm greater than under the adjacent annual crop by the final year. Although the shrub belts used more water than adjacent crop systems at Walpeup and Pallamana, this was mostly due to the use of stored soil water, and since the belts occupied only 7–18% of the land area, increases in total water use of these alley farming systems compared with conventional crop monocultures were quite small, and in terms of the extent of recharge control this was less than the area of crop yield loss. At the wetter, Bridgewater site, alley farming appeared to be using an increasing amount of water compared with conventional annual cropping systems. Overall, the data support previous work that indicates that in lower rainfall environments (<350 mm), alley farming is likely to be dogged by competition for water between crops and perennials.

Environmental response of spring wheat in the south-western Australian cereal belt

1987 ◽  
Vol 38 (4) ◽  
pp. 655 ◽  
Author(s):  
KG Rickert ◽  
RH Sedgley ◽  
WR Stern
Keyword(s):  
Water Use ◽  
Spring Wheat ◽  
Critical Evaluation ◽  
Grain Filling ◽  
High Ratio ◽  
Soil Types ◽  
Environmental Response ◽  
Total Water ◽  
Eastern Australia ◽  
Dry Conditions

The performance of the spring wheat cultivar Gamenya, the leading cultivar in Western Australia since 1968, was studied to identify key aspects of its response to the environment under typically dry conditions on two contrasting soil types: a heavy clay loam and a light loamy sand overlying clay in the Merredin region.In the rain-fed treatments the total water use was similar on both soils and was of the order of 240 mm. On the heavy-textured soil at high nitrogen, the foliage canopy developed more rapidly than on the light soil, resulting in earlier soil water depletion and haying off. Water use efficiencies of about 10 kg grain ha-1 per mm of water were similar to those reported for winter rainfall areas in south-eastern Australia. This suggests a greater degree of buffering against spring drought than is indicated by the high ratio of pre-anthesis to post-anthesis water use (3-4.7:l) relative to values of 2-2.7:l in other parts of the Australian wheatbelt. Data on the partitioning of dry matter indicated that this buffering of the harsh spring conditions at Merredin may be due to a greater contribution of assimilates from pre-anthesis storage, to grain filling. In dry environments, further critical evaluation is needed of the role of stored assimilates in grain formation.Faster canopy closure on the heavy soil resulted from a higher density of shoots and possibly larger leaves. This led to the suggestion that on heavier, more fertile soils, an ideotype with restricted tillering, may be higher yielding. By the end of the season ear bearing shoot densities and total water use were the same on both soil types, thus masking earlier important differences.

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