Daily Water Use Research Articles

Conserved water use improves the yield performance of soybean (Glycine max (L.) Merr.) under drought

We evaluated the importance of conserved water use in drought adaptation in soybean [Glycine max (L.) Merr.], and identified the traits involved in this mechanism. Eight soybean genotypes, four landraces and four recent cultivars, were collected and yield performance in the field was determined and used in pot experiments to evaluate the yield performance and the water use pattern under three soil moisture treatments imposed from 40days after sowing: well-watered [WW, soil water content (SWC) maintained between 85%–100% field capacity (FC)]; water stress (WS, water withheld until SWC decreased to 30% FC, rewatered to 100% FC and water withheld again to 30% FC); and terminal water stress (TWS, water withheld until maturity). The recent cultivars all out-yielded the landraces in two different years in the field and under well-watered conditions in the pot experiment. Among the eight soybean genotypes, J19 and ZH – two recent cultivars with lower daily water use before flowering, but higher use after flowering – had the best yield performance in the WS and TWS treatments in the pot experiment and in the field. These two soybean genotypes and J19, another recent cultivar, had higher grain yield, hundred-grain weights and water use efficiency for grain yield (WUEG) in the WS treatments than the other genotypes, and higher hundred grain weights, higher WUEG, higher pod numbers and the only significant grain yield in the TWS treatment. J19 and ZH had low root length densities (RLD), low leaf areas at flowering, and transpiration decreased at high plant available soil water content under drought. Thus, we conclude that reducing RLD and restricting water loss contributed to conserved water use and improved yield performance and WUEG in water-limited conditions.

Sapflow characteristics of Kandelia obovata and their controlling factors in Zhangjiang estuary, China.

In this study, the Grainer's thermal dissipation probe method was applied to monitor sap flux density (SFD) of a mangrove species Kandelia obovata over a period of one year (2010-10-2011-10) in Zhangjiangkou Mangrove National Nature Reserve, Fujian, China. The results showed that both season and diameter class exerted significant effects on the SFD of K. obovata trees. In summer, when the diameter at breast height (DBH) reached 8-10 cm, the highest SFD was found at a depth of 2 cm with a value of 38.21 g·m-2·s-1, which was comparable with those for other mangrove tree species and forested wetland tree species. The mean whole tree transpiration (i.e. daily water use) of all stem size classes demonstrated large changes from winter to summer, increased from 0.14 to 0.19 kg·d-1 in small trees (S, DBH=2-4 cm), from 0.94 to 1.45 kg·d-1 in medium trees (M, DBH=4-8 cm) and from 1.96 to 3.43 kg·d-1 in large ones (L, DBH=8-10 cm). The daily transpiration of K. obovata stand was calculated by summing all size classes, which was then summed up for entire year to estimate annual transpiration of entire K. obovata forest, which was about 100.38 mm, less than 6% of local annual precipitation. Key environmental factors all had significant effects (all P<0.001) on the stand transpiration rate (Es) of K. obovata forest, and photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) were the main driving factors, which explained 60%-92% seasonal variation of Es. The PAR and VPD had larger effects on the Es in summer than that in winter. In addition, we observed an obvious time lag phenomenon in the relationship between Es and PAR or VPD, which should be taken into account when explaining seasonal variation of Es in K. obovata forest.

A stochastic model for daily residential water demand

Residential water demand is a random variable which influences greatly the performance of municipal water distribution systems (WDSs). The water request at network nodes reflects the behavior of the residential users, and a proper characterization of their water use habits is vital for the hydraulic system modeling. This study presents a stochastic approach for the characterization of the daily residential water use. The proposed methodology considers a unique probabilistic distribution – mixed distribution – for any time during the day, and thus for any entity of the water demanded by the users. This distribution is obtained by the merging of two cumulative distribution functions taking into account the spike of the cumulative frequencies for the null requests. The methodology has been tested on three real water distribution networks, where the water use habits are different. Experimental relations are given to estimate the parameters of the proposed stochastic model in relation to the users number and to the average daily trend. Numerical examples for a practical application have shown the effectiveness of the proposed approach in order to generate the time series for the residential water demand.

Water as the primary beverage: A predictor of pediatric obesity

Aims: The aims of this study were to assess parental awareness of their own children’s weight status and healthy habits, as well as to determine whether the daily use of water as a child’s primary beverage is a predictor of pediatric obesity or overweight. Methods: A cross-sectional study was conducted at two primary pediatric clinics and one urgent care clinic from September 2014 to November 2014. Data were collected from children’s medical records as well as from parents of children aged 2-18 years. Chi-square tests, bivariate correlations, and multivariate logistic regression procedures were performed. Results: Two-thirds of parents with obese or overweight children were not aware of their children’s weight status. Male gender emerged as the positive predictor of pediatric obesity or overweight (OR, 9.86; 95% Confidence Interval [CI], 1.21-80.4; p = .033), whereas using water as the primary beverage throughout the day, with low-fat/skim milk at mealtimes was a negative predictor (OR, 0.019; 95% CI, 0.001-0.24; p = .002). Conclusions: There were nearly 50-fold lower odds of being obese or overweight for children who use water as the primary beverage throughout the day than those who do not. Rather than focusing on negative impacts of sugar-sweetened beverages or 100% fruit juice, more attention should be paid to the positive impact of using water as the primary beverage throughout the day. Using standardized BMI percentile growth charts, children’s weight status should be communicated to all parents. Teaching and motivating parents and children to drink water as their primary beverage throughout the day could be an effective approach to preventing and managing pediatric obesity.

Mapping evapotranspiration with high-resolution aircraft imagery over vineyards using one- and two-source modeling schemes

Abstract. Thermal and multispectral remote sensing data from low-altitude aircraft can provide high spatial resolution necessary for sub-field (≤ 10 m) and plant canopy (≤ 1 m) scale evapotranspiration (ET) monitoring. In this study, high-resolution (sub-meter-scale) thermal infrared and multispectral shortwave data from aircraft are used to map ET over vineyards in central California with the two-source energy balance (TSEB) model and with a simple model having operational immediate capabilities called DATTUTDUT (Deriving Atmosphere Turbulent Transport Useful To Dummies Using Temperature). The latter uses contextual information within the image to scale between radiometric land surface temperature (TR) values representing hydrologic limits of potential ET and a non-evaporative surface. Imagery from 5 days throughout the growing season is used for mapping ET at the sub-field scale. The performance of the two models is evaluated using tower-based measurements of sensible (H) and latent heat (LE) flux or ET. The comparison indicates that TSEB was able to derive reasonable ET estimates under varying conditions, likely due to the physically based treatment of the energy and the surface temperature partitioning between the soil/cover crop inter-row and vine canopy elements. On the other hand, DATTUTDUT performance was somewhat degraded presumably because the simple scaling scheme does not consider differences in the two sources (vine and inter-row) of heat and temperature contributions or the effect of surface roughness on the efficiency of heat exchange. Maps of the evaporative fraction (EF = LE/(H + LE)) from the two models had similar spatial patterns but different magnitudes in some areas within the fields on certain days. Large EF discrepancies between the models were found on 2 of the 5 days (DOY 162 and 219) when there were significant differences with the tower-based ET measurements, particularly using the DATTUTDUT model. These differences in EF between the models translate to significant variations in daily water use estimates for these 2 days for the vineyards. Model sensitivity analysis demonstrated the high degree of sensitivity of the TSEB model to the accuracy of the TR data, while the DATTUTDUT model was insensitive to systematic errors in TR as is the case with contextual-based models. However, it is shown that the study domain and spatial resolution will significantly influence the ET estimation from the DATTUTDUT model. Future work is planned for developing a hybrid approach that leverages the strengths of both modeling schemes and is simple enough to be used operationally with high-resolution imagery.

Grey water footprint combined with ecological network analysis for assessing regional water quality metabolism

Water pollution is a serious problem in Dianchi Lake Basin, which has resulted in severe pressure on the sustainable utilization of local water resources. This study investigates and quantifies the various water quality change processes involved in a regional water metabolism system by using grey water footprint. Furthermore, an ecological network model of the water quality change processes in water metabolism system is generated and an ecological network analysis is conducted to understand the underlying principles and analyze the importance of the compartments of water quality metabolism. This study provides insights into the status of water quality metabolism in water metabolism system and determines the reasons for the deteriorating water quality. It describes and quantifies 22 water quality change processes and builds the ecological network model to evaluate the metabolic effects of water quality in Dianchi Lake Basin. Results show that the pollutants from urban daily life water use are the main influencing factor on the water quality metabolism in Dianchi Lake Basin water metabolism system. The weight of the grey water footprint of the pollution source from urban daily life water use is the largest, which accounts for approximately 50% of the total weight (100%). Thus, management should exert significant effort to control pollutants from the water use of urban residents. By analyzing the interoperability between the components of the ecological network model, this study determines that all the water quality metabolic effects in Dianchi Lake Basin are poor from 2006 to 2013 (the values of mutualism indices M from 2006 to 2013 are all less than 1). The analysis results can be used to interpret the problems encountered in water quality metabolism in regional water metabolism systems. The proposed improvement measures could support the decision-making process regarding future investments for the optimization of pollution treatment and the sustainability of urban water use.

Yield Response Factor for Onion (Allium Cepa L) Crop Under Deficit Irrigation in Semiarid Tropics of Maharashtra

The present study deals with the study of yield response factor (Ky) for onion crop cultivated under deficit irrigation for Rahuri region (Maharashra). The field experiment was conducted to determine the yield response factor of the onion (Allium cepa L.) cv. N-2-4-1 crop under the deficit irrigation approach during summer season of 2012 and 2013 at Instructional Farm of the Department of Irrigation and Drainage Engineering, Dr. Annasaheb Shinde College of Agricultural Engineering, Mahatma Phule Krishi Vidyapeeth Rahuri. Experiment was carried out in Randomized Block Design (RBD) with 27 treatments and two replications based on different combinations of the quantity of water stress during different crop growth stages. Water applied per irrigation and soil moisture contents before and after irrigation were monitored throughout the season, while onion bulbs were harvested at the end of season and weighed. Average daily crop water use (crop consumptive use) were estimated from the soil moisture content using the soil moisture depletion method. The seasonal yield response factor (Ky) was obtained by relating relative yield decreases to relative crop water use deficit by the regression analysis. The relative yield decreases of the onion crop were proportionally greater with increase in evapotranspiration deficit. It shows the response of yield with respect to the decrease in water consumption. In other words, it explains the decrease in yield caused by the per unit decrease in water consumption. Seasonal crop response factor for onion crop was determined as 1.58, 1.48 and 1.54 during 2012, 2013 and average of both year (2012 &amp;2013) respectively. The yield response factors developed in this study could be used in irrigation design and scheduling for onion in the study area.

The circadian life of nocturnal water use: when late-night decisions help improve your day.

The circadian life of nocturnal water use: when late-night decisions help improve your day.

Time lags between crown and basal sap flows in tropical lianas and co-occurring trees.

Water storage in the stems of woody plants contributes to their responses to short-term water shortages. To estimate the contribution of water storage to the daily water budget of trees, time lags of sap flow between different positions of trunk are used as a proxy of stem water storage. In lianas, another large group of woody species, it has rarely been studied whether stored water functions in their daily water use, despite their increasing roles in the carbon and water dynamics of tropical forests caused by their increasing abundance. We hypothesized that lianas would exhibit large time lags due to their extremely long stems, wide vessels and large volume of parenchyma in the stem. We examined time lags in sap flow, diel changes of stem volumetric water content (VWC) and biophysical properties of sapwood of 19 lianas and 26 co-occurring trees from 27 species in 4 forests (karst, tropical seasonal, flood plain and savanna) during a wet season. The plants varied in height/length from <5 to >60 m. The results showed that lianas had significantly higher saturated water content (SWC) and much lower wood density than trees. Seven of 19 liana individuals had no time lags; in contrast, only 3 of 26 tree individuals had no time lags. In general, lianas had shorter time lags than trees in our data set, but this difference was not significant for our most conservative analyses. Across trees and lianas, time lag duration increased with diurnal maximum changeable VWC but was independent of the body size, path length, wood density and SWC. The results suggest that in most lianas, internal stem water storage contributes little to daily water budget, while trees may rely more on stored water in the stem.

Irrigating Based on Daily Water Use Reduces Nursery Runoff Volume and Nutrient Load Without Reducing Growth of Four Conifers

The objectives of this study were to quantify irrigation volume, runoff volume and nutrient content, and plant growth of container-grown conifers when irrigated based on plant daily water use (DWU) vs. a standard irrigation rate. Four conifer taxa were grown in 10.2-L (no. 3) containers subjected to four irrigation treatments from 23 June to 16 Oct. 2009 and 6 June to 31 Oct. 2010. The taxa were: 1) Chamaecyparis obtusa Sieb. &amp; Zucc. ‘Filicoides’, 2) Chamaecyparis pisifera (Sieb. &amp; Zucc.) Endl. ‘Sungold’, 3) Thuja occidentalis L. ‘Holmstrup’, and 4) Thuja plicata D. Donn ‘Zebrina’. The four irrigation treatments were: 1) control application of 19 mm·d−1, 2) irrigation applied to replace 100% DWU (100 DWU) per day, 3) applications alternating 100% with 75% DWU in a 2-day cycle (100–75 DWU), and 4) a 3-day application cycle replacing 100% DWU the first day and 75% DWU on the second and third days (100–75–75 DWU). Irrigation treatments did not affect plant growth index {GI= [(H + WNS + WEW)/3]} in 2009. In 2010, GI of C. obtusa ‘Filicoides’ was greater for 100 DWU than the control plants. Seasonal total water applied for 100, 100–75, and 100–75–75 DWU was 22%, 32%, and 56% less, respectively, than the control amount of 117 L per container in 2009 (114 days) and 24%, 18%, and 24% less than the control amount of 165 L per container in 2010 (147 days). Scheduling irrigation based on DWU reduced runoff volumes and (nitrate-nitrogen) NO3−-N and (phosphate-phosphorous) PO43−-P load compared with the control. Irrigating based on DWU reduced water application and runoff volumes and NO3−-N and PO43−-P load while producing plants of equal or greater size than control plants.

Beyond the big ditch: politics, ecology, and infrastructure at the Panama Canal

In this innovative book, Ashley Carse traces the water that flows into and out from the Panama Canal to explain how global shipping is entangled with Panama's cultural and physical landscapes. By following container ships as they travel downstream along maritime routes and tracing rivers upstream across the populated watershed that feeds the canal, he explores the politics of environmental management around a waterway that links faraway ports and markets to nearby farms, forests, cities, and rural communities. Carse draws on a wide range of ethnographic and archival material to show the social and ecological implications of transportation across Panama. The Canal moves ships over an aquatic staircase of locks that demand an enormous amount of fresh water from the surrounding region. Each passing ship drains 52 million gallons out to sea -- a volume comparable to the daily water use of half a million Panamanians. Infrastructures like the Panama Canal, Carse argues, do not simply conquer nature; they rework ecologies in ways that serve specific political and economic priorities. Interweaving histories that range from the depopulation of the U.S. Canal Zone a century ago to road construction conflicts and water hyacinth invasions in canal waters, the book illuminates the human and nonhuman actors that have come together at the margins of the famous trade route. 2014 marks the 100th anniversary of the Panama Canal. Beyond the Big Ditch calls us to consider how infrastructures are materially embedded in place, producing environments with winners and losers.

Seasonal Water Use of Southern Highbush Blueberry Plants in a Subtropical Climate

Nonweighing drainage lysimeters were used to measure seasonal water use of mature ‘Emerald’ southern highbush blueberry (SHB; Vaccinium corymbosum interspecific hybrid) plants grown in pine bark beds and in pine bark amended soil in north central Florida. In the absence of rain, irrigation was applied daily with microsprinklers at ≈120% to 175% of reference evapotranspiration as either single or split applications. Leachate was collected and its volume determined from each lysimeter at 6- to 10-day intervals throughout the study. Water use, expressed as L/plant, was calculated as the difference between the amount of irrigation/rain added to lysimeters and the amount of leachate collected from lysimeters during each measurement period. Average daily water use was calculated for monthly intervals beginning in Apr. 2010 and ending in Sept. 2012. Water use increased rapidly during spring through the final stages of fruit ripening and harvest (May) with peak water use occurring during mid to late summer (July, August, and September). Plants grown in pine bark beds used more water than plants in pine bark amended soil during Apr., May, and Dec. 2010, Feb. 2011, and Mar. 2012, but there were no differences during the periods of highest water use. No differences in water use were observed between single or split-application irrigation treatments. Monthly averages for daily water use during the 30-month period ranged from ≈1.75 L/plant in January to ≈8.0 L/plant in mid to late summer. Mean monthly crop coefficient values during the 30-month period ranged from 0.44 in February to 0.86 in September. Canopy volume, yield, and mean berry weight were unaffected by soil or irrigation treatments.

Radial variations in xylem sap flow and their effect on whole‐tree water use estimates

AbstractTo estimate whole‐tree or stand transpiration based on sap flow measurements, sap flux density (Fd) needs to be scaled up over the entire sapwood area. We investigated radial variations in Fd in the dominant oak (Quercus liaotungensis) and a commonly occurring oriental arborvitae (Platycladus orientalis) species using Granier‐type thermal dissipation probes in a semi‐arid forest in northern China. Our results show that Fd in oak trees reached a maximum just below the cambium and decreased towards the inner sapwood. On the other hand, radial sap flow patterns in oriental arborvitae trees differed among individuals. Fd values at different depths within an individual were highly correlated with each other in both species. We assessed the error of single‐depth measurements when upscaling to whole‐tree water use using multi‐depth measurements as a reference. Omitting radial variations resulted in an overestimation of daily water use by 38% and 78% in oak trees with sapwood depths of approximately 2 and 3 cm, respectively. The outer sapwood annuli (0–1 cm) contributed 74% and 65% to the total water use in the two classes of sapwood depth. These contribution coefficients may be used as correction indices for estimating whole‐tree water use. Errors of omitting radial variations in oriental arborvitae trees ranged from −42% to 21%. Using relatively long sensors (e.g. 2 cm) may improve the estimate accuracy in this species. The results would be applicable to the estimation of tree or stand transpiration based on routine depth measurements using one set of sensors. It is suggested that radial variations should be considered for accurately upscaling locally measured sap flow data to whole‐tree water use in trees with wide sapwood and that different approaches may be applied to species with different patterns of radial variations. Copyright © 2015 John Wiley &amp; Sons, Ltd.

The Practice of Green Cane Trash Blanketing in the Irrigated Zone of Mauritius: Effects on Soil Moisture and Water Use Efficiency of Sugarcane

Sugarcane growers in Mauritius are using mechanized harvesting to reduce costs. This practice results in a trash blanket which contributes to conserve soil moisture, but potential savings in irrigation water have yet to be quantified. An on-farm study was undertaken at three sites in the irrigated coastal zone of Mauritius under sub-humid to humid mega-thermal climate and soils that were oxisol or inceptisol. Trials were conducted in ratoon crops under centre pivot irrigation and treatments with or without trash blanket, as well as different irrigation regimes. Sensors were used to log soil moisture data at 20, 40 and 60 cm depths. Increased drainage was observed under trash blanket during rainfall events and cumulative drainage for a 4-month wet period amounted to 43 and 240 mm for no-trash and trash blanket treatments respectively. Daily crop water use was higher with trash blanket, consumption being 4.9 and 5.1 mm day−1 compared to 4.2 and 4.6 mm day−1 for no-trash during peak growth at Savannah and Medine. Sugarcane yield was higher by 7.2 and 6.6 t ha−1 year−1 with trash blanket compared to no-trash, whereas water use efficiency increased by 8 and 9 kg ha−1 mm−1. At Saint Antoine, trash blanket increased the yield difference between irrigated and rainfed crops by 8.6 t ha−1 and improved water use efficiency by 7 kg ha−1 mm−1 when irrigated. Seasonal water equivalence of the trash blanket amounted to 62, 54 and 72 mm water at Savannah, Medine and Saint Antoine, a potential saving of 10–15 % in irrigation water.

Stomatal structure and physiology do not explain differences in water use among montane eucalypts.

Understanding the regulation of water use at the whole-tree scale is critical to advancing the utility of physiological ecology, for example in its role in predictive hydrology of forested catchments. For three eucalypt species that dominate high-elevation catchments in south-eastern Australia, we examined if whole-tree water use could be related to three widely discussed regulators of water use: stomatal anatomy, sensitivity of stomata [i.e. stomatal conductance (g(s))] to environmental influences, and sapwood area. While daily tree water use varied sixfold among species, sap velocity and sapwood area varied in parallel. Combined, stomatal structure and physiology could not explain differences in species-specific water use. Species which exhibited the fastest (Eucalyptus delegatensis) and slowest (Eucalyptus pauciflora) rates of water use both exhibited greater capacity for physiological control of g(s) [indicated by sensitivity to vapour pressure deficit (VPD)] and a reduced capacity to limit g(s) anatomically [indicated by greater potential g(s) (g(max))]. Conversely, g(s) was insensitive to VPD and g(max) was lowest for Eucalyptus radiata, the species showing intermediate rates of water use. Improved knowledge of stomatal anatomy will help us to understand the capacity of species to regulate leaf-level water loss, but seems likely to remain of limited use for explaining rates of whole-tree water use in montane eucalypts at the catchment scale.

Comparison of whole-canopy water use efficiency and vine performance of cv. Sangiovese (Vitis vinifera L.) vines subjected to a post-veraison water deficit

In the present paper a series of WUE expressions, including the physiological and agronomical, were compared in potted cv. Sangiovese (Vitis vinifera L.) grapevines which were either well watered (WW) or subjected to progressive post-veraison water stress (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30%) of daily canopy transpiration (Tc) concurrently recorded via a plant-enclosure gas exchange system. While single-leaf intrinsic water-use efficiency (WUEi) increased with water stress severity, seasonal whole-canopy WUE were similar at pre-stress, 70% Tc, and upon rewatering but dropped during severe water stress. WUE calculated as mass of dry weight stored in annual biomass (leaves, canes and clusters) per liter of water used, did not differ on a seasonal basis, whereas WW and WS showed similar grape composition despite the latter suffered a 25% yield reduction. Results confirm that whole-canopy WUE is a much better index than single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. Under our specific case study, due to high reactivity of Sangiovese to early yellowing and shedding of basal leaves, it can be recommended that post-veraison water supply to Sangiovese vines should not be lower than 70% of daily vine water use.

Feasibility of Using Biocontainers in a Pot-in-pot System for Nursery Production of River Birch

The performance of biocontainers as sustainable alternatives to the traditional petroleum-based plastic containers has been researched in recent years due to increasing environmental concern generated by widespread plastic disposal from green industry. However, research has been mainly focused on using biocontainers in short-term greenhouse production of bedding plants, with limited research investigating the use of biocontainers in long-term nursery production of woody crops. This project investigated the feasibility of using biocontainers in a pot-in-pot (PIP) nursery production system. Two paper (also referred as wood pulp) biocontainers were evaluated in comparison with a plastic container in a PIP system for 2 years at four locations (Holt, MI; Lexington, KY; Crystal Springs, MS; El Paso, TX). One-year-old river birch (Betula nigra) liners were used in this study. Results showed that biocontainers stayed intact at the end of the first growing season, but were penetrated to different degrees after the second growing season depending on the vigor of root growth at a given location and pot type. Plants showed different growth rates at different locations. However, at a given location, there were no differences in plant growth index (PGI) or plant biomass among plants grown in different container types. Daily water use (DWU) was not influenced by container type. Results suggest that both biocontainers tested have the potential to be alternatives to plastic containers for short-term (1 year) birch production in the PIP system. However, they may not be suitable for long-term (more than 1 year) PIP production due to root penetration at the end of the second growing season.

Simulating nectarine tree transpiration and dynamic water storage from responses of leaf conductance to light and sap flow to stem water potential and vapor pressure deficit.

For isohydric trees mid-day water uptake is stable and depends on soil water status, reflected in pre-dawn leaf water potential (Ψpd) and mid-day stem water potential (Ψmd), tree hydraulic conductance and a more-or-less constant leaf water potential (Ψl) for much of the day, maintained by the stomata. Stabilization of Ψl can be represented by a linear relationship between canopy resistance (Rc) and vapor pressure deficit (D), and the slope (BD) is proportional to the steady-state water uptake. By analyzing sap flow (SF), meteorological and Ψmd measurements during a series of wetting and drying (D/W) cycles in a nectarine orchard, we found that for the range of Ψmd relevant for irrigated orchards the slope of the relationship of Rc to D, BD is a linear function of Ψmd. Rc was simulated using the above relationships, and its changes in the morning and evening were simulated using a rectangular hyperbolic relationship between leaf conductance and photosynthetic irradiance, fitted to leaf-level measurements. The latter was integrated with one-leaf, two-leaf and integrative radiation models, and the latter gave the best results. Simulated Rc was used in the Penman-Monteith equation to simulate tree transpiration, which was validated by comparing with SF from a separate data set. The model gave accurate estimates of diurnal and daily total tree transpiration for the range of Ψmds used in regular and deficit irrigation. Diurnal changes in tree water content were determined from the difference between simulated transpiration and measured SF. Changes in water content caused a time lag of 90-105 min between transpiration and SF for Ψmd between -0.8 and -1.55 MPa, and water depletion reached 3 l h(-1) before noon. Estimated mean diurnal changes in water content were 5.5 l day(-1) tree(-1) at Ψmd of -0.9 MPa and increased to 12.5 l day(-1) tree(-1) at -1.45 MPa, equivalent to 6.5 and 16.5% of daily tree water use, respectively. Sixteen percent of the dynamic water volume was in the leaves. Inversion of the model shows that Ψmd can be predicted from D and Rc, which may have some importance for irrigation management to maintain target values of Ψmd. That relationship will be explored in future research.

都市緑化樹木を対象とした大型重量計による単木蒸散量の計測と樹木の形態的・生理的特徴に基づく分析

The purpose of this study is to grasp the variation of whole tree transpiration rates and capacities of container-grown isolated trees and to analyze tree's morpho-physiological effects. We developed hanging-type gravimeter and weighed 11 species (h=3~6.7 m). We found (1)Daily water use in summer irrigation days were 10~30 kg, equivalent to 0.62±0.36 times of water evaporation from the same size of crown projection area, (2)Maximum latent heat was 2.3 kW/tree, (3)Same tree's capacity can change threefold due to physiological change, (4)Ring-porous species tend to use much water, which suggest the significance of hydraulic capacity under volume-restricted soil condition.

The Influence of Deficit Irrigation on Growth, Ornamental Quality, and Water Use Efficiency of Three Potted Bougainvillea Genotypes Grown in Two Shapes

Bougainvillea is widely used as flowering shrub in gardening and landscaping in the Mediterranean region characterized by limited water supply. The evaluation of deficit irrigation as a possible technique to improve water productivity and selection of genotypes that can better withstand soil water deficits are essential for sustainable production. A greenhouse experiment was conducted to determine the effects of deficit irrigation on three potted Bougainvillea genotypes [B. glabra var. Sanderiana, B. ×buttiana ‘Rosenka’, B. ‘Lindleyana’ (=B. ‘Aurantiaca’)] grown in two shapes, globe and pyramid, on agronomical and physiological parameters. Irrigation treatments were based on the daily water use (100%, 50%, or 25%). The shoot, total dry biomass, leaf number, leaf area, and macronutrient [nitrogen (N), phosphorus (P), and potassium (K)] concentration decreased in response to an increase in water stress with the lowest values recorded in the severe deficit irrigation (SDI) treatment. At 160 days after transplanting (DAT), the percentage of total dry biomass reduction caused by irrigation level was lower in B. ×buttiana ‘Rosenka’ compared with B. glabra var. Sanderiana and B. ‘Lindleyana’ (=B. ‘Aurantiaca’). At 160 DAT, the flower index increased in response to an increase in water stress with the highest values recorded under both moderate deficit irrigation (MDI) and SDI for B. ×buttiana ‘Rosenka’. The biomass water use efficiency (WUE) increased under water stress conditions with the highest values recorded in B. glabra var. Sanderiana and B. ×buttiana ‘Rosenka’ grown under MDI (average 1.43 and 1.25 g·L−1, respectively) and especially with SDI (average 1.68 and 1.36 g·L−1, respectively). A number of tolerance mechanisms such as increase in stomatal resistance, decrease in leaf water potential, and decrease in leaf osmotic potential have been observed, especially under SDI. The MDI treatment can be used successfully in Bougainvillea to reduce water consumption while improving the overall quality and WUE, whereas the genotypes B. glabra var. Sanderiana and B. ×buttiana ‘Rosenka’ could be considered suitable for pot plant production.