Annual Reference Evapotranspiration Research Articles

Green and Blue Water Footprints of Major Crops in the Wami/Ruvu Basin, Tanzania: Implications for Water Scarcity and Sustainability

Accurate estimation of the blue and green water requirements of the various crops cultivated in a water basin is essential for planning specific plant/crop irrigation schedules. In this study, the crop water requirements of the major crops grown in the Wami/Ruvu basin were determined using the FAO-CROPWAT model based on meteorological parameters: monthly maximum and minimum temperature, wind speed, mean relative humidity, sunshine hours, rainfall data, and effective rainfall for 23 hydro-meteorological stations distributed in the study area. The studied crops are rice, maize, beans, tomatoes, and sugarcane. The crop reference evapotranspiration (ETo) and actual evapotranspiration (ETc) for each crop were determined using crop coefficients (Kc) of various growth stages of crops. The results indicated that the total annual reference evapotranspiration (ETo) was 1604 mm, whereas an average ETo per month was 134 mm. The highest total irrigation water requirements were recorded in sugarcane, followed by rice, while the lowest water requirements were observed in beans and tomatoes. The results presented in this study may facilitate plant-specific water irrigation implementation and maximize crop production while conserving the environment.

Climate change impacts on water flux dynamics in Shingoda basin having agriculture and forest ecosystems: A comprehensive analysis

An assessment of climate chnage and its impacts on water fluxes in the Shingoda basin of the Saurashtra region having 14% agriculture and 75% forest were made through analysis of time series (1951-2100) of bias corrected maximum/minimum temperature and rainfall (RCP4.5), rreference evapotranspiration (ETo), evapotranspiration (ETc) and runoff. Results showed significant climate changes in the basin, with day mean temperature rising from 24.4°C in the second half of the 20th century to 26.5°C and 27.9°C in the first and second half of the 21st century, respectively. During the first and second half of the 21st century, seasonal rainfall increased by 23.0% and 46.33%, and runoff rose by 46.78% and 86.40% compared to the second half of the 20th century. However, annual reference evapotranspiration (ETo) decreased by -1.41% and -6.5%, and crop evapotranspiration (ETc) decreased by -3.2% and -9.8% in the same periods. The analysis also revealed a deficit of -16.10% in downward water flux (rainfall) in the first half of the 20th century, followed by a surplus of 8.46% and 28.37% compared to the upward flux (ETc) in subsequent periods. The upward water flux deficit during 2nd half of 20th century were supported by evidence of depleted groundwater levels and seawater intrusion in the study area.

Irrigation Water Requirements in Regions along Euphrates River in Iraq: Role and implications of Climate Change

This research aimed to predict how projected climate change will affect the quantity of water needed for irrigation. The case study focused on the Iraqi cities of Anbar and Babylon, located in the Euphrates River Basin (ERB). The CROPWAT model was fed by current and future climate data. Three climate change scenarios for the reference period from 1995-2014, SSP1-2.6 (2020-2039) and SSP2- 4.5 (2040-2059), were implemented in this research. The obtained results showed that annual increases in the temperature for Anbar are 1.1 and 1.85 °C, and for Babylon, they are 0.9 and 1.88 °C for the two scenarios SSP1- 2.6 and SSP2-4.5 concerning the reference period scenario. In addition, the annual decrease in precipitation is 3.61 and 4.63 mm for Anbar and 3.61 and 2.66 mm for Babylon Province. The average annual reference evapotranspiration for the three climate scenarios is 157, 202, and 206 mm for Anbar and 187.5, 195.6, and 224 mm for Babylon Province. The total annual irrigation water requirements for the crop growth cycle are 1.10, 1.43, and 1.46 for Anbar and 3.96, 4.13, and 4.76 billion cubic meters for Babylon.

Impact of climate change on shumbrite small scale irrigation project, South Gojjam subbasin, Ethiopia

Climate change has the potential to affect climate parameters like rainfall and temperature which lead to a change in the irrigation water requirement of the irrigation system. As irrigation water requirement is highly dependent on precipitation and potential evapotranspiration, climate change impact studies are necessary. Therefore, this study aims to assess the impact of climate change on the irrigation water requirement of the Shumbrite irrigation project. For this study, climate variables of precipitation and temperature were generated from CORDEX-Africa simulations downscaled from MPI Global Circulation Model (GCM) under three emission scenarios (RCP2.6, RCP4.5, and RCP8.5). The climate data covers from 1981 to 2005 for the baseline period and 2021–2045 for the future period for all scenarios. Future precipitation shows a decrease for all scenarios with a maximum decrease under RCP2.6 (4.2%) and temperature show an increase in the future as compared to the baseline period. The reference evapotranspiration and Irrigation Water Requirements (IWR) were calculated by using CROPWAT 8.0 software. Results showed that the mean annual reference evapotranspiration is expected to increase in the future by 2.7%, 2.6%, and 3.3% for RCP2.6, RCP4.5, and RCP8.5 respectively as compared to the baseline period. Mean annual irrigation water requirement shows an increase of 2.58%, 0.74%, and 8.4% for the future under RCP2.6, RCP4.5, and RCP8.5 respectively. The Crop Water Requirement (CWR) also increases for the future period under all RCP scenarios, with maximum CWR for tomato, potato, and pepper crops. To ensure the sustainability of the project, crops with high irrigation water requirements should be replaced by other crops with low water requirements.

КОЛИЧЕСТВЕННАЯ ОЦЕНКА ПРОСТРАНСТВЕННО-ВРЕМЕННОЙ ИЗМЕНЧИВОСТИ ЭВАПОТРАНСПИРАЦИИ И ОПРЕДЕЛЯЮЩИХ ЕЕ КЛИМАТИЧЕСКИХ ФАКТОРОВ В БАНГЛАДЕШ В 1981-2018 ГГ

Reference evapotranspiration is a vital research item for hydrologic pattern systems in drought-flood risks of a country like Bangladesh. The present research examines spatiotemporal fluctuations in reference evapotranspiration and influencing factors of these fluctuations by applying the Mann-Kendall test with the Theil-Sen’s estimator, Inverse Distance Weighted interpolation method, differential equation and detrending method depending on diurnal meteorological data sets attained from 25 weather observatories between 1981 and 2018. By current research, the FAO 56 Penman-Monteith (PM) model is executed for determining seasonal and annual reference evapotranspiration (ETpmf), and differential equation and detrending method is implemented for assessing correlation, sensitivities, and benefaction of four climatological variables to ETpmf. The MK trend analysis has been performed jointly with the Theil-Sen’s estimator to discover movement of ETpmf and meteorological variables. ETpmf displayed a conspicuous descendant tendency ( p < 0.01) at post-monsoon (-0.87 mm/year), winter (-1.13 mm/year), and annual time scale (-3.31 mm/year) in whole Bangladesh, but at the same period, a non-significant descending tendency of ETpmf was observed in pre-monsoon (-1.47 mm/year) and monsoon (-0.07 mm/year) season in the study area. These changes of ETpmf could be explained by a notable rising tendency in average temperature (TA) and actual vapor pressure (VP) and noteworthy declining tendencies in wind speed (WS) and sunshine duration (SD). ETpmf had been maximum sensitive to TA, a bit less, to VP, SD, and WS in the annual and seasonal periods. TA, WS, and SD produced a positive effect, whereas the VP negatively affected seasonal and annual ETpmf. Despite the negative effect on ETpmf, VP was the second most sensitive to the annual and all seasonal ETpmf after TA. Crosswise the entire study area, WS had the greatest influence to ETpmf, after that TA and SD. At the same time, the positive contribution of VP to ETpmf could not counterbalance the negative contributions of WS, TA, and SD. While the consequence of VP on variations in ETpmf is minor, it has to be considered particularly in the cold period. The counter association among inclining TA and declining ETpmf, which is known as the “evaporation paradox,” happenned in Bangladesh. These research outcomes will be beneficial to develop forthcoming water scheduling and regulation of feasible water resources to lessen climate change effects on agronomic water prerequisites and regulate human induced actions.

A Multidataset Assessment of Climatic Drivers and Uncertainties of Recent Trends in Evaporative Demand across the Continental United States

AbstractIncreased atmospheric evaporative demand has important implications for humans and ecosystems in water-scarce lands. While temperature plays a significant role in driving evaporative demand and its trend, other climate variables are also influential and their contributions to recent trends in evaporative demand are unknown. We address this gap with an assessment of recent (1980–2020) trends in annual reference evapotranspiration (ETo) and its drivers across the continental United States based on five gridded datasets. In doing so, we characterize the structural uncertainty of ETo trends and decompose the relative influences of temperature, wind speed, solar radiation, and humidity. Results highlight large and robust changes in ETo across much of the western United States, centered on the Rio Grande region where ETo increased 135–235 mm during 1980–2020. The largest uncertainties in ETo trends are in the central and eastern United States and surrounding the Upper Colorado River. Trend decomposition highlights the strong and widespread influence of temperature, which contributes to 57% of observed ETo trends, on average. ETo increases are mitigated by increases in specific humidity in non-water-limited regions, while small decreases in specific humidity and increases in wind speed and solar radiation magnify ETo increases across the West. Our results show increases in ETo across the West that are already emerging outside the range of variability observed 20–40 years ago. Our results suggest that twenty-first-century land and water managers need to plan for an already increasing influence of evaporative demand on water availability and wildfire risks.Significance StatementIncreased atmospheric thirst due to climate warming has the potential to decrease water availability and increase wildfire risks in water-scarce regions. Here, we identified how much atmospheric thirst has changed across the continental United States over the past 40 years, what climate variables are driving the change, and how consistent these changes are among five data sources. We found that atmospheric thirst is consistently emerging outside the range experienced in the late twentieth century in some western regions with 57% of the change driven by temperature. Importantly, we demonstrate that increased atmospheric thirst has already become a persistent forcing of western landscapes and water supplies toward drought and will be an essential consideration for land and water management planning going forward.

Characterization of climate impacts on a semi-arid agricultural perimeter in Morocco

The manifestations of climate change in precipitation, air temperature and simulated evapotranspiration for crops in the Tadla perimeter in central Morocco are examined. The study area is characterized by a semi-arid climate, with a potential agricultural vocation. This area is exposed to a scarcity of water resources for crop irrigation. To this effect, it is it is treating of rainfall in this area over 60 years (1958-2018) at 27 measuring stations and for temperature and reference evapo-transpiration (ETo) over 49 years (1969-2018) at 4 stations. Following data analysis by homogeneity tests on the agro-climatic time series (Pettitt test, Lee and Heghinian test, Buishand test and Hubert’s segmentation method). It is detecting that there are time breaks on annual rainfall, mean temperature and reference evapo-transpiration at the respective years of 1978, 1995 and 1978. Because of these breaks in time, rainfall is reducing by 36%, atmospheric warming is 1°C and the climate demand for evaporation coupled with plant transpiration increases by 13%. Consequently, the water requirement increases significantly in the agricultural area of crop production.

Responses of Baseflow to Ecological Construction and Climate Change in Different Geomorphological Types in The Middle Yellow River, China

Baseflow is a critical component of streamflow in arid areas. Determining variations in baseflow and the factors affecting it have positive roles for water resource utilization in arid watersheds. Two watersheds, the Hailiutu River watershed (HLTR) and the Dali River watershed (DLR), located in two different geomorphological regions of the middle Yellow River, were selected for this study. By using the Eckhardt segment method (fourth digital filtering method, DF4), baseflow was separated from streamflow based on its daily data. Mann-Kendall trend test analysis (M-K trend test) was used to test the trends in baseflow change at different times. Complex Morlet wavelet analysis was used to judge baseflow periodicity. Heuristic segmentation and sequential cluster analysis were used to identify the potential change points in the baseflow series for the two regions together with Pearson correlation coefficient. The results showed: (1) the annual baseflow of the HLTR and the DLR showed significantly decreasing trends (P < 0.01), more significantly for the HLTR (0.33 × 108 m3) than the DLR (0.20 × 108 m3). The annual base flow index (BFI, baseflow/total streamflow) in the wind-sand region (0.75) was larger than for the loess region (0.55), and the BFI in the wind-sand region was more stable in different periods. (2) The annual baseflow of the HLTR and the DLR both exhibited a complete main cycle of 42 years and 38 years, respectively. The change points of the annual baseflow in the HLTR were 1967 and 1986, and 1971 and 1996 in the DLR. (3) There was no significant change in annual precipitation in the two watersheds, while annual reference evapotranspiration (ET0) in the DLR showed a significant increasing trend (P < 0.01). The normalized difference vegetation index (NDVI) on the DLR (0.40) was higher than on the HLTR (0.26). (4) Baseflow in the wind-sand region, where vegetation improvement was the only ecological activity, decreased faster than in the loess region where there had been numerous ecological measures such as vegetation improvement, check dams and terraces. This implied that comprehensive measures such as these were helpful in slowing the rate at which the baseflow decreases. Therefore, the effect of ecological construction should be considered in future baseflow studies in other geomorphological types within the Middle Yellow River Basin.

Trends in evapotranspiration and their responses to climate change and vegetation greening over the upper reaches of the Yellow River Basin

This study comprehensively analyzed long-term (1960–2014) variations of potential and actual evapotranspiration (ET) and quantified their inter-annual and seasonal sensitivity and attribution to climate and vegetation growth changes in the upper reaches of the Yellow River Basin (UYRB). Satellite-derived vegetation greenness and in situ measured hydrometeorological datasets were used. Average annual reference evapotranspiration (ET0) showed significant decreasing trend (p < 0.05) by 0.32 mm year−1 over the past 55 years. Results obtained from recovered stationary series and sensitivity analyses showed that reduction of wind speed was the major driving force for decreasing trends in annual and seasonal ET0. Water budget-derived actual evapotranspiration (ETa) increased dramatically during the study period, whereas potential evapotranspiration (ETp) calculated from Penman equation and pan evaporation (ETpan) decreased significantly, suggesting the existence of evaporation paradox over the UYRB. ETa and ETp or ETpan exhibited complementary behavior, while the complementary relationship was asymmetric. During the period 1982–2014, vegetation greening occurred in most areas (65.6%) of the UYRB and was mediated by elevation. Interestingly, non-uniform climate warming imposed opposite impacts on vegetation growth, namely inter-annual and seasonal NDVI was stimulated by daytime temperature but suppressed by nighttime temperature. Furthermore, the positive impacts imposed by daytime temperature on NDVI was much larger in spring than in autumn and summer. Large-scale coherent vegetation greening would be the primary factor affecting inter-annual ETa in comparison with climate factors. These results help in deep understanding the hydrological response to climate change in cold mountain regions.

Spatial and temporal trend in monthly and annual reference evapotranspiration in Madagascar for the 1980-2010 period

The temporal trend and spatial distribution of reference evapotranspiration was investigated across Madagascar for the period of Air temperature relative humidity temperature relative humidity solar radiation and wind speed were collected from weather stations across the country and were used to estimate daily reference evapotranspiration ET by the Penman Monteith equation Monthly average daily ET and the total annual ET were estimated The Mann Kendall test was used for the temporal trend analysis in monthly average daily ET and the total annual ET and the Sen rsquo s method was used to estimate the rate of change in ET during the study period The spline interpolation method was used for spatial interpolation of the variation in annual and monthly average ET The results showed southwest north East trend in ET Reference evapotranspiration was higher at the western semiarid region than the humid eastern region ET peaked during the period of September October Annual total ET varied from mm in Andapa at northeast to mm in Antsohihy at northwestern coastal region Overall there was an increasing trend in annual total ET however the upward trend was significant only at out of weather station sites while monthly ET did not show consistent trends This is one of the first comprehensive studies that investigate spatial and temporal dynamics of ET in Madagascar which can aid in developing appropriate adaptation strategies to improve crop water use and evaporative losses estimates for maintaining or increasing food production while enhancing water use efficiency in the western semiarid regions of Madagascar

Regional probability distribution of the annual reference evapotranspiration and its effective parameters in Iran

The reference evapotranspiration (ET0) plays an important role in water management plans in arid or semi-arid countries such as Iran. For this reason, the regional analysis of this parameter is important. But, ET0 process is affected by several meteorological parameters such as wind speed, solar radiation, temperature and relative humidity. Therefore, the effect of distribution type of effective meteorological variables on ET0 distribution was analyzed. For this purpose, the regional probability distribution of the annual ET0 and its effective parameters were selected. Used data in this research was recorded data at 30 synoptic stations of Iran during 1960–2014. Using the probability plot correlation coefficient (PPCC) test and the L-moment method, five common distributions were compared and the best distribution was selected. The results of PPCC test and L-moment diagram indicated that the Pearson type III distribution was the best probability distribution for fitting annual ET0 and its four effective parameters. The results of RMSE showed that the ability of the PPCC test and L-moment method for regional analysis of reference evapotranspiration and its effective parameters was similar. The results also showed that the distribution type of the parameters which affected ET0 values can affect the distribution of reference evapotranspiration.

Reference evapotranspiration (ETo) and irrigation water requirement of different crops in Bihar

For irrigation scheduling and better management of the water, estimation of irrigation water requirement of the crop is essentially required. The study was conducted for estimation of daily reference evapotranspiration (ETo) by FAO Penman-Monteith method using 30 years (1985-2015) mean meteorological data of two locations Sabour (zone III A) and Patna (zone III B) in Bihar. The crop evapotranspiration was estimated using crop coefficients of different crops like rice,kharif maize, wheat, rabi maize, green gram and summer maize at Sabour and Patna locations. Irrigation water requirement for different crops was estimated based on crop evapotranspiration and effective rainfall during the growing period of the crop. The mean annual reference evapotranspiration (ETo) was found 3.6 mmday-1 at Sabour and 4.1 mmday-1 at Patna. The total crop evapotranspiration was maximum for rice crop in kharif season 546.0 and 607.3 mm at Sabour and Patna respectively and lowest for wheat crop in rabi season 212.9 mm and 243.3 mm at Sabour and Patna respectively. Net irrigation water requirement was maximum for summer maize366.3at Sabour and 508.2 mm at Patna for rice crop whereas lowest in kharif maize 67.5 and 161.4 mm at Sabour and Patna respectively.

Attributing the Changes in Reference Evapotranspiration in Southwestern China Using a New Separation Method

Abstract This study investigated monthly and annual reference evapotranspiration changes over southwestern China (SWC) from 1960 to 2012, using the Food and Agriculture Organization of the United Nations’ report 56 (FAO-56) Penman–Monteith equation and routine meteorological observations at 269 weather sites. During 1960–2012, the monthly and annual decreased at most sites. Moreover, the SWC regional average trend in annual was significantly negative (p &amp;lt; 0.05); this trend was the same in most months. A new separation method using several numerical experiments was proposed to quantify each driving factor’s contribution to changes and exhibited higher accuracy based on several validation criteria, after which an attribution analysis was performed. Across SWC, the declining annual was mainly due to decreased net radiation (RN). Spatially, the annual changes at most sites in eastern SWC (excluding southeastern West Guangxi) were generally due to RN, whereas wind speed (WND) or vapor pressure deficit (VPD) was the determinant at other sites. Nevertheless, the determinants differed among 12 months. For the whole SWC, increased VPD in February and decreased WND in April, May, and October were the determinant of decreased ; however, decreased RN was the determinant in other months. Overall, the determinant of the monthly changes exhibited a complex spatial pattern. A complete analysis of changes and the related physical mechanisms in SWC is necessary to better understand hydroclimatological extremes (e.g., droughts) and to develop appropriate strategies to sustain regional development (e.g., water resources and agriculture). Importantly, this separation method provides new perspective for quantitative attribution analyses and thus may be implemented in various scientific fields (e.g., climatology and hydrology).

ASSESSMENT OF THE WATER NEEDS OF APRICOT AND OLIVE CROPS UNDER ARID CLIMATIC CONDITIONS: CASE STUDY OF TINIBAOUINE REGION (NORTHEAST OF ALGERIA)

The Tinibaouine region, located in north-eastern Algeria on the borders of the Batna-Belezma Mountains, is characterized by a semi-arid to arid climate with an average annual rainfall not exceeding 465 mm and an average annual temperature of around 22 ° C. This region is characterized by the cultivation of apricots as essential crop followed by that of olives, whose plots are all irrigated with the Tinibaouine springwater. These are 450 Ha of trees for apricot and 108 Hectare for olives which constitute the principal revenue of the citizens of this small village. This paper estimated the crop reference and actual evapotranspiration (ETO) respectively and the irrigation water requirement of apricot trees and olive trees. The long recorded climatic data, crop and soil data, effective water allocation and planning, the information about crop water requirements, irrigation withdrawals were computed with the Cropwat model which is based on the United Nations’ Food and Agriculture Organization (FAO), the Penman-Monteith method was used to estimate ETo. Crop coefficients (Kc) from the phenomenological stages of apricot and olive were applied to adjust and estimate the actual evapotranspiration ETc through a water balance of the irrigation water requirements (IR). The results showed that the annual reference evapotranspiration (ETO) was estimated at 3.71mm / day. The irrigation requirements were estimated at 35800 m3/ hectare for apricot, 6980 m3/ hectare for olive, alsoIrrigation needs estimated onland at 14185, 05 m3/ hectare for olive and apricot.

Trend Analysis in Rainfall, Reference Evapotranspiration and Aridity Index in Southern Senegal: Adaptation to the Vulnerability of Rainfed Rice Cultivation to Climate Change

Rainfall and evapotranspiration are two vital elements for food production under rainfed agriculture. This study aims at investigating the combined changes in these variables in the form of aridly index in the southern Senegal. The temporal trends in annual and monthly (from May to October) aridity index, rainfall and evapotranspiration are examined and adaptation strategies to the vulnerability of rainfed rice cultivation to the changes are developed. The results show a significant decreasing trend in annual rainfall at all study locations for the period 1922-2015. When analyzing the trends in sub-periods, there are two clear patterns in the annual rainfall series: a decreasing trend for the period 1922-1979 and a reversal increasing trend for the period 1980-2015. An increasing trend is also observed in annual reference evapotranspiration. The results reveal that the region will be drier with a significant increase in aridity at the annual and most monthly series. Appropriate adaptation strategies should be implemented to diminish the adverse influence of the increasing aridity on rice productivity for a sustainable agriculture.

Micro-climate influence on reference evapotranspiration estimates in wetlands

ABSTRACTTemperature and relative humidity measurements were made within and outside a lowland fen in eastern England during 2009 and 2010. Summer temperatures were found to be on average 0.24°C lower within the fen than outside, whilst summer vapour pressures were found to be on average 0.074 kPa higher within the fen. In contrast, winter temperatures were found to be higher within the fen by an average of 0.03°C. These differences may be expected to influence evapotranspiration estimates derived using data from each of the sites. The influence of the location of meteorological measurements on evapotranspiration estimates was therefore evaluated. The existence of a wetland microclimate results in up to a 7% reduction in annual reference evapotranspiration compared to a site surrounded by arable farmland only 5.5 km away.

Basin‐scale assessment of the land surface water budget in the National Centers for Environmental Prediction operational and research NLDAS‐2 systems

AbstractThe purpose of this study is to evaluate the components of the land surface water budget in the four land surface models (Noah, SAC‐Sacramento Soil Moisture Accounting Model, (VIC) Variable Infiltration Capacity Model, and Mosaic) applied in the newly implemented National Centers for Environmental Prediction (NCEP) operational and research versions of the North American Land Data Assimilation System version 2 (NLDAS‐2). This work focuses on monthly and annual components of the water budget over 12 National Weather Service (NWS) River Forecast Centers (RFCs). Monthly gridded FLUX Network (FLUXNET) evapotranspiration (ET) from the Max‐Planck Institute (MPI) of Germany, U.S. Geological Survey (USGS) total runoff (Q), changes in total water storage (dS/dt, derived as a residual by utilizing MPI ET and USGS Q in the water balance equation), and Gravity Recovery and Climate Experiment (GRACE) observed total water storage anomaly (TWSA) and change (TWSC) are used as reference data sets. Compared to these ET and Q benchmarks, Mosaic and SAC (Noah and VIC) in the operational NLDAS‐2 overestimate (underestimate) mean annual reference ET and underestimate (overestimate) mean annual reference Q. The multimodel ensemble mean (MME) is closer to the mean annual reference ET and Q. An anomaly correlation (AC) analysis shows good AC values for simulated monthly mean Q and dS/dt but significantly smaller AC values for simulated ET. Upgraded versions of the models utilized in the research side of NLDAS‐2 yield largely improved performance in the simulation of these mean annual and monthly water component diagnostics. These results demonstrate that the three intertwined efforts of improving (1) the scientific understanding of parameterization of land surface processes, (2) the spatial and temporal extent of systematic validation of land surface processes, and (3) the engineering‐oriented aspects such as parameter calibration and optimization are key to substantially improving product quality in various land data assimilation systems.

Leaf traits in Chilean matorral: sclerophylly within, among, and beyond matorral, and its environmental determinants.

Studies of leaf traits often focus on tradeoffs between growth and resource conservation, but little is known about variation in the mechanical traits that influence resource conservation. This study investigates how leaf mechanical traits vary across matorral vegetation in central Chile, how they correlate with environmental factors, and how these trends compare at a broader geographic scale. Leaf toughness, strength, stiffness, and associated traits were measured in five matorral types in central Chile, and relationships with soil N and P and climate variables were assessed. Trends with soil and climate were then analyzed across shrubland and woodland in Chile, Western Australia, and New Caledonia. Chilean species varied in leaf mechanics and associated traits, both within and among matorral types, with more species in sclerophyll matorral having strong, tough, and stiff leaves than in arid and littoral matorral. Overall, leaves with high leaf dry mass per area were stiffer, tougher, stronger, thicker, denser, with more fiber, lignin, phenolics and fiber per unit protein and less protein: tannin activity and N and P per mass, forming a broad sclerophylly syndrome. Mechanical traits of matorral species were not correlated with soil N or P, or predictably with climate variables, except flexural stiffness (EI W) which correlated positively with annual reference evapotranspiration (ET 0). However, soil P made strong independent contributions to variation in leaf mechanics across shrublands and woodlands of Chile, Western Australia, and New Caledonia, either separately (strength) or together with ET 0 (toughness) explaining 46-90% of variation. Hence ET 0 was predictive of EI W in Chilean matorral, whereas soil P was highly predictive of variation in leaf strength, and combined with ET 0 was highly predictive of toughness, at a broader geographic scale. The biological basis of these relationships, however, may be complex.

Comparison of Different Methods to Estimate Mean Daily Evapotranspiration from Weekly Data at Patna, India

Estimation of evapotranspiration is necessary for efficient water management and crop planning. Fifteen different methods of ET0 estimation were employed to compute daily reference evapotranspiration for the period 2010 to 2014. In the absence of reliable open pan evaporimeter data, FAO-56 Penman Monteith method was considered as one of the reliable method of ET0 estimation. The results showed that mean weekly evapotranspiration values obtained from Penman-Monteith method were very closer to FAO-56 Penman-Monteith method and values from all the other methods except FAO- 24 Pan, Christiansen Pan and Hargreaves methods generally predicted higher values of mean weekly daily ET0 in comparison to FAO-56 Penman-Monteith method. The analysis shows that mean weekly daily ET0 estimates of combination methods resulted better ET0 estimates than radiation, and temperature and evaporation methods. Weekly ET0 values estimated by FAO-56 Penman-Monteith method were found to vary in the range of 1.3 mm/day to 6.7 mm/day. Average annual reference evapotranspiration was found as 1517.1 mm.

Spatiotemporal Changes of Reference Evapotranspiration in Mongolia during 1980–2006

Reference evapotranspiration (RET) plays an important role in the terrestrial hydrological cycle. Applying the Penman-Monteith method, the RET over Mongolia was estimated from 1980 to 2006. The changing trends and magnitude of RET were detected by the Mann-Kendall test and Theil-Sen’s slope methods. Meanwhile, aridity indices were estimated using two different indices. The impacts of meteorological variables on RET were assessed through sensitive analysis by comparing the resulting RETs from artificially disturbed meteorological variables. The results indicated that the RET for 16 stations in Mongolia showed an increasing trend, particularly in the center and south. The calculated RET was higher than precipitation, which means severe droughts in Mongolia. The spatial patterns of RET are significantly influenced by climatic conditions as well as characteristics of the underlying surface (e.g., elevation and vegetation). The mean annual RET decreased from the south to the north, owing to sparse vegetation in the south of Mongolia. The sensitivity analysis revealed that the changes of RET were strongly affected by air temperature and relative humidity.