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1
Schwingshackl, Clemens, Martin Hirschi, and Sonia I. Seneviratne. "Quantifying Spatiotemporal Variations of Soil Moisture Control on Surface Energy Balance and Near-Surface Air Temperature." Journal of Climate 30, no. 18 (August 8, 2017): 7105–24. http://dx.doi.org/10.1175/jcli-d-16-0727.1.
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Abstract Soil moisture plays a crucial role for the energy partitioning at Earth’s surface. Changing fractions of latent and sensible heat fluxes caused by soil moisture variations can affect both near-surface air temperature and precipitation. In this study, a simple framework for the dependence of evaporative fraction (the ratio of latent heat flux over net radiation) on soil moisture is used to analyze spatial and temporal variations of land–atmosphere coupling and its effect on near-surface air temperature. Using three different data sources (two reanalysis datasets and one combination of different datasets), three key parameters for the relation between soil moisture and evaporative fraction are estimated: 1) the frequency of occurrence of different soil moisture regimes, 2) the sensitivity of evaporative fraction to soil moisture in the transitional soil moisture regime, and 3) the critical soil moisture value that separates soil moisture- and energy-limited evapotranspiration regimes. The results show that about 30%–60% (depending on the dataset) of the global land area is in the transitional regime during at least half of the year. Based on the identification of transitional regimes, the effect of changes in soil moisture on near-surface air temperature is analyzed. Typical soil moisture variations (standard deviation) can impact air temperature by up to 1.1–1.3 K, while changing soil moisture over its full range in the transitional regime can alter air temperature by up to 6–7 K. The results emphasize the role of soil moisture for atmosphere and climate and constitute a useful benchmark for the evaluation of the respective relationships in Earth system models.
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Akbar, Ruzbeh, Daniel J. Short Gianotti, Kaighin A. McColl, Erfan Haghighi, Guido D. Salvucci, and Dara Entekhabi. "Estimation of Landscape Soil Water Losses from Satellite Observations of Soil Moisture." Journal of Hydrometeorology 19, no. 5 (May 1, 2018): 871–89. http://dx.doi.org/10.1175/jhm-d-17-0200.1.
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Abstract This study presents an observation-driven technique to delineate the dominant boundaries and temporal shifts between different hydrologic regimes over the contiguous United States (CONUS). The energy- and water-limited evapotranspiration regimes as well as percolation to the subsurface are hydrologic processes that dominate the loss of stored water in the soil following precipitation events. Surface soil moisture estimates from the NASA Soil Moisture Active Passive (SMAP) mission, over three consecutive summer seasons, are used to estimate the soil water loss function. Based on analysis of the rates of soil moisture dry-downs, the loss function is the conditional expectation of negative increments in the soil moisture series conditioned on soil moisture itself. An unsupervised classification scheme (with cross validation) is then implemented to categorize regions according to their dominant hydrological regimes based on their estimated loss functions. An east–west divide in hydrologic regimes over CONUS is observed with large parts of the western United States exhibiting a strong water-limited evapotranspiration regime during most of the times. The U.S. Midwest and Great Plains show transitional behavior with both water- and energy-limited regimes present. Year-to-year shifts in hydrologic regimes are also observed along with regional anomalies due to moderate drought conditions or above-average precipitation. The approach is based on remotely sensed surface soil moisture (approximately top 5 cm) at a resolution of tens of kilometers in the presence of soil texture and land cover heterogeneity. The classification therefore only applies to landscape-scale effective conditions and does not directly account for deeper soil water storage.
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Yang, Zesu, Qiang Zhang, Yu Zhang, Ping Yue, Liang Zhang, Jian Zeng, and Yulei Qi. "Hydrothermal Factors Influence on Spatial-Temporal Variation of Evapotranspiration-Precipitation Coupling over Climate Transition Zone of North China." Remote Sensing 14, no. 6 (March 17, 2022): 1448. http://dx.doi.org/10.3390/rs14061448.
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As a land–atmosphere coupling “hot spot”, the northern China climate transition zone has a sharp spatial gradient of hydrothermal conditions, which plays an essential role in shaping the spatial and temporal pattern of evapotranspiration-precipitation coupling, but whose mechanisms still remain unclear. This study analyzes the spatial and temporal variation in land–atmosphere coupling strength (CS) in the climate transitional zone of northern China and its relationship with soil moisture and air temperature. Results show that CS gradually transitions from strong positive in the northwest to negative in the southeast and northeast corners. The spatial distribution of CS is closely related to climatic hydrothermal conditions, where soil moisture plays a more dominant role: CS increases first, and then decreases with increasing soil moisture, with the threshold of soil moisture at 0.2; CS gradually transitions from positive to negative at soil moisture between 0.25 and 0.35; CS shows an exponential decreasing trend with increasing temperature. In terms of temporal variation, CS is strongest in spring and weakens sequentially in summer, autumn, and winter, and has significant interdecadal fluctuations. The trend in CS shifts gradually from significantly negative in the west to a non-significant positive in the east. Soil moisture variability dominates the intra-annual variability of CS in the study regions, and determines the interannual variation of CS in arid and semi-arid areas. Moreover, the main reason for the positive and negative spatial differences in CS in the study area is the different driving regime of evapotranspiration (ET). ET is energy-limited in the southern part of the study area, leading to a positive correlation between ET and lifting condensation level (LCL), while in most of the northern part, ET is water-limited and is negatively correlated with LCL; LCL has a negative correlation with P across the study area, thus leading to a negative ET-P coupling in the south and a positive coupling in the north.
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Buitink, Joost, Anne M. Swank, Martine van der Ploeg, Naomi E. Smith, Harm-Jan F. Benninga, Frank van der Bolt, Coleen D. U. Carranza, Gerbrand Koren, Rogier van der Velde, and Adriaan J. Teuling. "Anatomy of the 2018 agricultural drought in the Netherlands using in situ soil moisture and satellite vegetation indices." Hydrology and Earth System Sciences 24, no. 12 (December 21, 2020): 6021–31. http://dx.doi.org/10.5194/hess-24-6021-2020.
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Abstract. The soil moisture status near the land surface is a key determinant of vegetation productivity. The critical soil moisture content determines the transition from an energy-limited to a water-limited evapotranspiration regime. This study quantifies the critical soil moisture content by comparison of in situ soil moisture profile measurements of the Raam and Twente networks in the Netherlands, with two satellite-derived vegetation indices (near-infrared reflectance of terrestrial vegetation, NIRv, and vegetation optical depth, VOD) during the 2018 summer drought. The critical soil moisture content is obtained through a piece-wise linear correlation of the NIRv and VOD anomalies with soil moisture on different depths of the profile. This non-linear relation reflects the observation that negative soil moisture anomalies develop weeks before the first reduction in vegetation indices: 2–3 weeks in this case. Furthermore, the inferred critical soil moisture content was found to increase with observation depth, and this relationship is shown to be linear and distinctive per area, reflecting the tendency of roots to take up water from deeper layers when drought progresses. The relations of non-stressed towards water-stressed vegetation conditions on distinct depths are derived using remote sensing, enabling the parameterization of reduced evapotranspiration and its effect on gross primary productivity in models to study the impact of a drought on the carbon cycle.
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Diro, G. T., and L. Sushama. "The Role of Soil Moisture–Atmosphere Interaction on Future Hot Spells over North America as Simulated by the Canadian Regional Climate Model (CRCM5)." Journal of Climate 30, no. 13 (July 2017): 5041–58. http://dx.doi.org/10.1175/jcli-d-16-0068.1.
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Soil moisture–atmosphere interactions play a key role in modulating climate variability and extremes. This study investigates how soil moisture–atmosphere coupling may affect future extreme events, particularly the role of projected soil moisture in modulating the frequency and maximum duration of hot spells over North America, using the fifth-generation Canadian Regional Climate Model (CRCM5). With this objective, CRCM5 simulations, driven by two coupled general circulation models (MPI-ESM and CanESM2), are performed with and without soil moisture–atmosphere interactions for current (1981–2010) and future (2071–2100) climates over North America, for representative concentration pathways (RCPs) 4.5 and 8.5. Analysis indicates that, in future climate, the soil moisture–temperature coupling regions, located over the Great Plains in the current climate, will expand farther north, including large parts of central Canada. Results also indicate that soil moisture–atmosphere interactions will play an important role in modulating temperature extremes in the future by contributing more than 50% to the projected increase in hot-spell days over the southern Great Plains and parts of central Canada, especially for the RCP4.5 scenario. This higher contribution of soil moisture–atmosphere interactions to the future increases in hot-spell days for RCP4.5 is related to the fact that the projected decrease in soil moisture caused the soil to remain in a transitional regime between wet and dry state that is conducive to soil moisture–atmosphere coupling. For the RCP8.5 scenario, on the other hand, the future projected soil state over the southern United States and northern Mexico is too dry to have an impact on evapotranspiration and therefore on temperature.
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McDermid, Sonali Shukla, Carlo Montes, Benjamin I. Cook, Michael J. Puma, Nancy Y. Kiang, and Igor Aleinov. "The Sensitivity of Land–Atmosphere Coupling to Modern Agriculture in the Northern Midlatitudes." Journal of Climate 32, no. 2 (December 26, 2018): 465–84. http://dx.doi.org/10.1175/jcli-d-17-0799.1.
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AbstractModern agricultural land cover and management are important as regional climate forcings. Previous work has shown that land cover change can significantly impact key climate variables, including turbulent fluxes, precipitation, and surface temperature. However, fewer studies have investigated how intensive crop management can impact background climate conditions, such as the strength of land–atmosphere coupling and evaporative regime. We conduct sensitivity experiments using a state-of-the-art climate model with modified vegetation characteristics to represent modern crop cover and management, using observed crop-specific leaf area indexes and calendars. We quantify changes in land–atmosphere interactions and climate over intensively cultivated regions situated at transitions between moisture- and energy-limited conditions. Results show that modern intensive agriculture has significant and geographically varying impacts on regional evaporative regimes and background climate conditions. Over the northern Great Plains, modern crop intensity increases the model simulated precipitation and soil moisture, weakening hydrologic coupling by increasing surface water availability and reducing moisture limits on evapotranspiration. In the U.S. Midwest, higher growing season evapotranspiration, coupled with winter and spring rainfall declines, reduces regional soil moisture, while crop albedo changes also reduce net surface radiation. This results overall in reduced dependency of regional surface temperature on latent heat fluxes. In central Asia, a combination of reduced net surface energy and enhanced pre–growing season precipitation amplify the energy-limited evaporative regime. These results highlight the need for improved representations of agriculture in global climate models to better account for regional climate impacts and interactions with other anthropogenic forcings.
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Wang, Suping, Qiang Zhang, Ping Yue, Jianshun Wang, Jinhu Yang, Wei Wang, Hongli Zhang, and Xueyuan Ren. "Precipitation-Use Efficiency and Its Conversion with Climate Types in Mainland China." Remote Sensing 14, no. 10 (May 20, 2022): 2467. http://dx.doi.org/10.3390/rs14102467.
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The impacts of climate change on ecosystem productivity and water resources over a long term in China are not well quantified. Precipitation-use efficiency (PUE) is a key parameter that describes carbon and water exchange in terrestrial ecosystems. Research on the response of regional PUE to climate change and its driving forces is of great significance to climate-change mitigation and the sustainable development of regional ecology. Based on an improved actual evapotranspiration (ETa) model, the responses of ETa, net primary productivity (NPP), and PUE to climate change in different climatic regions of China were analyzed; the contributions of various environmental factors to PUE changes were quantified; and the conversion characteristics and regulatory mechanisms of the PUE regime in different climatic regions were identified. The results indicate that the improved ETa model, after considering the limiting effect of energy on ETa in humid regions, can simulate the ETa distribution in China well. Over the past 58 years (1960–2017), ETa and NPP have increased in the western regions and decreased in the eastern regions, with the boundary at 103° E. PUE presents a “low-high-low” spatial distribution from northwest to southeast in China. It is noteworthy that there was a zonal distribution for a high value area of PUE, which coincided with the summer monsoon transition zone. The soil moisture (SM) increase in arid regions is the main driving force of the PUE increase, whereas the annual net radiation (Rn) change in humid regions is the main driving force of the PUE change. The transition zone is the conversion zone, where the prevailing factor limiting vegetation growth transitions from water to energy.
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Ibragimova, Kh. "Irrigation Effect on Evapotranspiration (in Absheron)." Bulletin of Science and Practice 6, no. 11 (November 15, 2020): 179–87. http://dx.doi.org/10.33619/2414-2948/60/21.
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In the presented article, the results of the use of dispersed irrigation are considered. This method helps to reduce the ambient temperature, increase soil moisture, establish an optimal irrigation regime, reduce the need for water resources, prevent depression of photosynthesis of alfalfa agrophytocenosis under Absheron conditions. It is recommended to carry out dispersed irrigation on the soil surface at temperatures above 28 °C. The best results were obtained under the condition of the combined application of dispersed irrigation with sprinkling, especially in dry years.
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WANG, Cong, Shuai WANG, Bojie FU, Lu ZHANG, Nan LU, and Lei JIAO. "Stochastic soil moisture dynamic modelling: a case study in the Loess Plateau, China." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 109, no. 3-4 (September 2018): 437–44. http://dx.doi.org/10.1017/s1755691018000658.
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ABSTRACTSoil moisture is a key factor in the ecohydrological cycle in water-limited ecosystems, and it integrates the effects of climate, soil, and vegetation. The water balance and the hydrological cycle are significantly important for vegetation restoration in water-limited regions, and these dynamics are still poorly understood. In this study, the soil moisture and water balance were modelled with the stochastic soil water balance model in the Loess Plateau, China. This model was verified by monitoring soil moisture data of black locust plantations in the Yangjuangou catchment in the Loess Plateau. The influences of a rainfall regime change on soil moisture and water balance were also explored. Three meteorological stations were selected (Yulin, Yan'an, and Luochuan) along the precipitation gradient to detect the effects of rainfall spatial variability on the soil moisture and water balance. The results showed that soil moisture tended to be more frequent at low levels with decreasing precipitation, and the ratio of evapotranspiration under stress in response to rainfall also changed from 74.0% in Yulin to 52.3% in Luochuan. In addition, the effects of a temporal change in rainfall regime on soil moisture and water balance were explored at Yan'an. The soil moisture probability density function moved to high soil moisture in the wet period compared to the dry period of Yan'an, and the evapotranspiration under stress increased from 59.5% to 72% from the wet period to the dry period. The results of this study prove the applicability of the stochastic model in the Loess Plateau and reveal its potential for guiding the vegetation restoration in the next stage.
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Buchtele, J., M. Tesař, and P. Krám. "Variability of water regime in the forested experimental catchments." Soil and Water Research 4, Special Issue 2 (March 19, 2010): S93—S101. http://dx.doi.org/10.17221/1366-swr.
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The water regime variability in most catchments is frequently influenced not only by the changes of the vegetation cover in the annual cycle but also by its development in the time span of decades. That means that the resulting evapotranspiration depends not only on the actual climatic situation but also on the soil moisture. The simulations of the rainfall-runoff process have been used with the intention to follow the possible role of the developing land cover. The differences between the observed and simulated flows in relatively long periods can be considered as an appropriate tool for the assessment of the water regime changes, in which the evapotranspiration demand variability is a significant phenomenon.
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Manning, Colin, Martin Widmann, Emanuele Bevacqua, Anne F. Van Loon, Douglas Maraun, and Mathieu Vrac. "Soil Moisture Drought in Europe: A Compound Event of Precipitation and Potential Evapotranspiration on Multiple Time Scales." Journal of Hydrometeorology 19, no. 8 (August 1, 2018): 1255–71. http://dx.doi.org/10.1175/jhm-d-18-0017.1.
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Abstract Compound events are extreme impacts that depend on multiple variables that need not be extreme themselves. In this study, we analyze soil moisture drought as a compound event of precipitation and potential evapotranspiration (PET) on multiple time scales related to both meteorological drought and heat waves in wet, transitional, and dry climates in Europe during summer. Drought indices that incorporate PET to account for the effect of temperature on drought conditions are sensitive to global warming. However, as evapotranspiration (ET) is moisture limited in dry climates, the use of such drought indices has often been criticized. We therefore assess the relevance of the contributions of both precipitation and PET to the estimation of soil moisture drought. Applying a statistical model based on pair copula constructions to data from FluxNet sites in Europe, we find at all sites that precipitation exerts the main control over soil moisture drought. At wet sites PET is additionally required to explain the onset, severity, and persistence of drought events over different time scales. At dry sites, where ET is moisture limited in summer, PET does not improve the estimation of soil moisture. In dry climates, increases in drought severity measured by indices incorporating PET may therefore not indicate further drying of soil but the increased availability of energy that can contribute to other environmental hazards such as heat waves and wildfires. We therefore highlight that drought indices including PET should be interpreted within the context of the climate and season in which they are applied in order to maximize their value.
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Dubenok, Nikolay N., Aleksandr V. Gemonov, and Aleksandr V. Lebedev. "Moisture consumption by plum seedlings under drip irrigation in the Central Nonchernozem zone of Russia." RUDN Journal of Agronomy and Animal Industries 15, no. 2 (December 15, 2020): 191–99. http://dx.doi.org/10.22363/2312-797x-2020-15-2-191-199.
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The aim of the study was to establish influence of different soil moisture content and climatic factors on water consumption of plum seedlings grown in a fruit nursery in the Nonchernozem zone. According to the results of studies conducted on plum seedlings under drip irrigation in the Moscow region for two years, evapotranspiration with different precipitation availability and temperature was determined. Variability of total water consumption depending on meteorological factors and irrigation regime was considered. Studies have confirmed the increase in the value of evapotranspiration with increasing pre-irrigation threshold of humidity with low-volume drip irrigation. The maximum values of water consumption by year of research, as expected, were recorded in the most wetted variant of the experiment, where moisture content of soil root zone did not fall below 80 % of the field moisture capacity. The statistical analysis carried out did not confirm the effect of varietal characteristics on evapotranspiration, which may be associated with the use of related rootstocks and the use of seedlings with the comparable force of growth in laying the experience. Structure of evapotranspiration of plum seedlings was determined according to experimental data of two research years. Precipitation and irrigation were the most part of total water consumption.
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Luong, Nguyen Duc, Nguyen Hoang Hiep, and Thi Hieu Bui. "Investigating the Spatio-Temporal Variation of Soil Moisture and Agricultural Drought towards Supporting Water Resources Management in the Red River Basin of Vietnam." Sustainability 13, no. 9 (April 28, 2021): 4926. http://dx.doi.org/10.3390/su13094926.
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The increasing serious droughts recently might have significant impacts on socioeconomic development in the Red River basin (RRB). This study applied the variable infiltration capacity (VIC) model to investigate spatio-temporal dynamics of soil moisture in the northeast, northwest, and Red River Delta (RRD) regions of the RRB part belongs to territory of Vietnam. The soil moisture dataset simulated for 10 years (2005–2014) was utilized to establish the soil moisture anomaly percentage index (SMAPI) for assessing intensity of agricultural drought. Soil moisture appeared to co-vary with precipitation, air temperature, evapotranspiration, and various features of land cover, topography, and soil type in three regions of the RRB. SMAPI analysis revealed that more areas in the northeast experienced severe droughts compared to those in other regions, especially in the dry season and transitional months. Meanwhile, the northwest mainly suffered from mild drought and a slightly wet condition during the dry season. Different from that, the RRD mainly had moderately to very wet conditions throughout the year. The areas of both agricultural and forested lands associated with severe drought in the dry season were larger than those in the wet season. Generally, VIC-based soil moisture approach offered a feasible solution for improving soil moisture and agricultural drought monitoring capabilities at the regional scale.
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Tužinský, Ladislav, Eduard Bublinec, and Marek Tužinský. "Development of soil water regime under spruce stands." Folia Oecologica 44, no. 1 (June 27, 2017): 46–53. http://dx.doi.org/10.1515/foecol-2017-0006.
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AbstractThe aim of this paper is to analyse the water regime of soils under spruce ecosystems in relation to long-lasting humid and drought periods in the growing seasons 1991-2013. The dominant interval humidity in observing growing seasons is semiuvidic interval with soil moisture between hydro-limits maximal capillary capacity (MCC) and point of diminished availability (PDA). Gravitationally seepage concentrated from accumulated winter season, water from melting snow and existing atmospheric precipitation occurs in the soil only at the beginning of the growing season. The supplies of soil water are significantly decreasing in the warm climate and precipitant deficient days. The greatest danger from drought threatens Norway spruce during the summer months and it depends on the duration of dry days, water supply at the beginning of the dry days, air temperature and the intensity of evapotranspiration. In the surface layers of the soil, with the maximum occurrence of active roots, the water in semiarid interval area between hydro-limits PDA and wilting point (WP) decreases during the summer months. In the culminating phase occurs the drying to moisture state with capillary stationary and the insufficient supply of available water for the plants. Physiological weakening of Norway spruce caused by set of outlay components of the water balance is partially reduced by delivering of water by capillary action from deeper horizons. In extremely dry periods, soil moisture is decreasing also throughout the soil profile (0-100 cm) into the bottom third of the variation margin hydro-limits MCC-PDA in the category of capillary less moving and for plants of low supply of usable water (60-90 mm). The issue of deteriorated health state of spruce ecosystems is considered to be actual. Changes and developments of hydropedological conditions which interfere the mountain forests represent the increasing danger of the drought for the spruce.
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Josef, Zavadil. "Optimisation of Irrigation Regime for Early Potatoes, Late Cauliflower, Early Cabbage and Celery." Soil and Water Research 1, No. 4 (January 7, 2013): 139–52. http://dx.doi.org/10.17221/6515-swr.
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The paper deals with optimisation of threshold suction pressure of soil water on light soils for early potatoes, early cabbage, late cauliflower and celery on the basis of results of small-plot field experiments with differentiated irrigation regime. Experiments were conducted in 2003–2005. Threshold suction pressures of soil water were identical for all crops: 15 kPa in treatment I, 30 kPa in treatment II, 60 kPa in treatment III, and 120 kPa in treatment IV. Precipitation, air temperature and relative humidity, global solar radiation, wind speed and direction were measured by an automated meteorological station. Reference and actual evapotranspiration was determined for the experimental crops according to FAO Paper No. 56 and by means of a biological curve (BC) in 2003–2005. To compare these two methods of calculation of actual evapotranspiration the soil moisture balance was found out. Based on the influence on marketable yield and proportion of the crop quality grades it is possible to determine the optimum threshold suction pressure on light loamy-sand soils in early potatoes, late cauliflower and cabbage 30 kPa and in celery 15 kPa. 80% of available soil water capacity (ASWC) corresponds to the threshold suction pressure 30 kPa, and as much as 96% of ASWC corresponds to 15 kPa. The seasonal irrigation depths determined on the basis of soil moisture balance, in which the crop evapotranspiration (ETc) is calculated either according to FAO 56 or by the BC, are substantially different from the really achieved irriga­tion depths in the treatments where optimal suction pressure is maintained. For potatoes, the really achieved values of seasonal irrigation depths are nearer to the depths calculated by the BC, while for the other vegetables (cauliflower, cabbage and celery) they are more similar to the depths calculated by FAO 56 methodology. The theoretical irrigation depths calculated by the BC method sometimes differ substantially from those based on FAO 56. These differences are at maximum for cauliflower and celery and at minimum for cabbage and decrease with the decreasing irrigation depths.
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Cely-Reyes, Germán Eduardo, Karen Victoria Suárez-Parra, and Rosalina González-Forero. "Water use efficiency in four irrigation regimes in bulb onion production in the Alto Chicamocha Irrigation District." Revista Colombiana de Ciencias Hortícolas 14, no. 3 (September 1, 2020): 393–401. http://dx.doi.org/10.17584/rcch.2020v14i3.12347.
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The bulb onion is one of the most important agricultural products in Colombia. The productive conditions of the Riego del Alto Chicamocha (Boyaca) district are a regional and national benchmark for this market. The objective of this research was to evaluate four irrigation regimes in terms of production and irrigation water efficiency in bulb onion crops. This trial was in the municipality of Nobsa, village of Dicho (Boyaca). A completely randomized design with four treatments was used: irrigation regime with 150% evapotranspiration (Evt); moisture-based irrigation regime, detected with soil moisture sensors; irrigation regime with 100% Evt; irrigation regime with 60% Evt, along with four repetitions. Starting three weeks after transplant and for 11 weeks (77 days), the polar diameter (cm), equatorial diameter (cm), root length (cm), leaf length (cm), SPAD units, stomatal conductance and irrigation water use efficiency were determined. The irrigation regime with 100% Evt had the best performance in terms of the polar and equatorial diameters and the root and leaf lengths, which were reflected in the fresh weight at harvest. The irrigation regime with soil moisture values obtained from remote sensors, with lower amounts of applied water, had better values for the transformation of water to fresh mass, with 13.64 kg mm-1.
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Eruola, Abayomi. "Response of yam varieties to soil moisture regime in Southwestern Nigeria." Italian Journal of Agrometeorology, no. 2 (December 27, 2021): 3–14. http://dx.doi.org/10.36253/ijam-1324.
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A field experiment was conducted on varietal response of white yam to moisture regime in Abeokuta. The experiment comprised three varieties of yam (Efuru, Ise-osi and Oniyere), three mulching options (grass, polythene and unmulched), and two planting dates (early and late). Treatments were replicated three times using RCBD lay-out. Model for selecting planting date involved relating potential evapotranspiration (PE) to precipitation (P) in the form of 0.1PE<P < 0.5PE, partitioned for attaining optimal planting date into early {T1= Σ(P-0.1PE) ≤ 0} and late {T2 = Σ(P-0.5PE) ≤ 0}, respectively. For humid period defined by P> PE, the physiological parameters and moisture agro-climatic indices measured during phenological stages of yam grown were analyzed with respect to treatments. Result showed that T1 defined as Σ(P-0.1PE) ≤ 10 mm appeared as the best model that significantly (P < 0.05) influenced emergence rate, phenological growth and tuber yield. All yam varieties evaluated were suitable for planting with respect to yield. Efuru and Ise-osi synchronized perfectly with Actual Water Availability and produced good vegetative growth with LAI of 1.08 and 0.91 leading to higher tuber yield of 12 and 11.64 tonnes ha-1, respectively. Grass mulch had tuber yield, 4-6 tonnes ha-1greater than the polythene and unmulched plots in all varieties. Mulching significantly (P< 0.05) increased tuber yield, 6-8 tonnes ha-1than the unmulched. Conclusively, early planting with grass mulch increased tuber yield.
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Jayawardane, NS, J. Blackwell, and M. Stapper. "Effect of changes in moisture profiles of a transitional red-brown earth with surface and slotted gypsum applications on the development and yield of a wheat crop." Australian Journal of Agricultural Research 38, no. 2 (1987): 239. http://dx.doi.org/10.1071/ar9870239.
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The low productivity of transitional red-brown earths for flood irrigated upland cropping is associated with their low infiltration rates and inadequate aeration of the root zone. The effect of the measured changes in the moisture and aeration profiles with surface and slotted gypsum applications on growth and development of a wheat crop was evaluated in a preliminary field study, on non-replicated plots.The patterns of changes in moisture profiles in the gypsum slotted plots were similar to those observed in the previous season, namely, deeper preferential wetting and faster internal drainage through the slots. This resulted in lower volumetric moisture contents in the slots and in the surface and subsurface layers between slots, compared to the non-slotted plots.The critical moisture contents were defined for each soil depth at which an air-filled porosity of 0.08 mm3 mm-3 was reached. For the transitional red-brown earth used in this study, air-filled porosity needs to be larger than 0.08 mm3 mm-3 to provide a soil pathway for oxygen flow to roots. The moisture profiles in the no-gypsum, surface gypsum and slotted gypsum plots measured throughout the cropping season indicated the period of time when oxygen flow through different soil layers was likely to be restricted. The moisture contents were higher than the critical value in the surface and subsurface layers of the non-slotted plots, particularly in the plot with no gypsum applications, during a period in winter with prolonged rainfall and low evapotranspiration rates. This resulted in reductions in the rates of phasic development, tillering, canopy closure and dry matter production and finally lower yields in the non-slotted plots, especially in the plot without gypsum. Differences in grain yields were mainly due to differences in the number of spikes m-2.During the second half of the growing season higher potential evapotranspiration, lower rainfall and accurate irrigation scheduling resulted in the moisture contents being maintained below the critical limits at all depths in all plots. Consequently, the two yield components which were determined during this period, namely, the number of kernels per spike and kernel weight, showed only slight variations between plots.
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Kurachenko, N. L., O. A. Ulyanova, O. A. Vlasenko, V. V. Kazanov, and E. Yu Kazanova. "WATER AVAILIBILITY OF SPRING RAPE SEEDS ON AGROCHERNOZEM OF KANSK FOREST-STEPPE." Bulletin of Agrarian Science 5, no. 86 (2020): 39–44. http://dx.doi.org/10.17238/issn2587-666x.2020.5.39.
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The influence of spring rapeseed on the water regime and moisture balance of agrochernozem was studied in a field experiment under the conditions of the Kansk forest-steppe of the Krasnoyarsk Territory. The study of the water regime of agrochernozem in the crops of spring rape was carried out on 4 test plots from May to September with an interval of 10-12 days. Soil samples were taken from the depth of 0-100 cm every 10 cm. It has been established that the water regime of agrochernozem, functioning in crops of spring rape, determined by soil conditions, biological and physiological characteristics of plants and meteorological parameters, is generally satisfactory in the meter layer. Moisture profiles of typical clayey-illuvial agrochernozem, reflecting the distribution of moisture in the soil for the period May-September, showed drying of 0-30 cm of the soil layer in the period from the beginning of stem growth to full maturation. Precipitation, which fell in the period from June to August, was completely consumed and did not replenish the soil moisture reserves, but played an important role in the formation of the crop yield. The reserves of productive moisture in the 0-20 cm layer were 9-11 mm and were assessed as poor during the period of flowering and pod formation in rape. Intensive consumption of productive moisture during the growing season occurred mainly from the 0-50 cm layer (Cv = 38%) and, to a lesser extent, from the 50-100 cm layer (Cv = 26%). Evapotranspiration moisture consumption by spring rape from the 0- 50 cm was rated at 255 mm. The average moisture consumption for the formation of 1 ton of spring rapeseed was 54 mm with a yield of 4.8 t / ha.
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Alonge, Charles J., Karen I. Mohr, and Wei-Kuo Tao. "Numerical Studies of Wet versus Dry Soil Regimes in the West African Sahel." Journal of Hydrometeorology 8, no. 1 (February 1, 2007): 102–16. http://dx.doi.org/10.1175/jhm559.1.
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Abstract The West African Sahel lies between the wet, humid equatorial zone of Africa to the south and the Sahara Desert to the north. This topography results in a strong north–south precipitation gradient. A coupled land–atmosphere (cloud resolving) model and observed data from the Hydrological Atmospheric Pilot Experiment in the Sahel were used to simulate both wet and dry soil moisture regimes. There are two case studies—one characterized by convective precipitation, the other by fair weather. In both of the case studies, evapotranspiration from the tiger bush land cover was noticeably larger in the wet soil moisture regime. The increase in latent heat flux was the key factor in creating a boundary layer that was more favorable to late-afternoon deep convection in the wet regime. Differences in boundary layer growth and development between the case studies suggested a more important role for the land surface in fair weather environments versus convective precipitation environments.
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GHOSH, A., and O. N. SINGH. "DETERMINATION OF THRESHOLD REGIME OF SOIL MOISTURE TENSION FOR SCHEDULING IRRIGATION IN TROPICAL AEROBIC RICE FOR OPTIMUM CROP AND WATER PRODUCTIVITY." Experimental Agriculture 46, no. 4 (July 19, 2010): 489–99. http://dx.doi.org/10.1017/s0014479710000359.
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SUMMARYAerobic rice is considered a viable agro-technology to cope with the looming crisis of water supply that threatens the sustainability of irrigated rice production systems. Rice adapted to aerobic conditions requires less water than that grown under conventional irrigation management. A field study was conducted at Cuttack, India, during the dry season (January–May) in 2005 and 2006 to determine the critical soil moisture regime at the root-zone depth (30 cm) for sustaining optimum growth and grain yield of aerobic rice variety ‘Apo’ (IR 55423-01). Irrigation at 0, 20 and 40 kPa soil moisture tension resulted in similar grain yields (4.90–5.25 t ha−1 in 2005 and 4.35–4.50 t ha−1 in 2006). The seasonal water requirement in treatments receiving irrigation at 20, 40 and 60 kPa soil moisture tensions was 28.4, 42.8 and 60.7% lower than that at 0 kPa soil moisture tension, but the yield declined significantly at 60 kPa, i.e. by 42.8% in 2005 and 36.7% in 2006. Irrigation at 40 kPa soil moisture tension ensured maximum water productivity of 0.90, 0.47 and 0.53 g grain kg−1 water with respect to evapotranspiration, irrigation plus rainfall and irrigation alone, respectively. Thus, irrigation at 40 kPa soil moisture tension may be considered critical for optimum grain yield and maximum water productivity of aerobic rice in Indian cultivation conditions.
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Matejka, F., J. Rožnovský, T. Hurtalová, and D. Janouš. "Effect of soil drought on evapotranspiration of a young spruce forest." Journal of Forest Science 48, No. 4 (May 17, 2019): 166–72. http://dx.doi.org/10.17221/11871-jfs.
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Daily courses of the actual transpiration of a forest stand were determined by an experimentally verified mathematical Soil – Vegetation – Atmosphere Transfer model. The results refer to the Norway spruce (Picea abies [L.] Karst.) monoculture situated in the highest locations of the Beskids Mts. Drought-free transpiration was estimated as a model simulation run for nonlimiting soil moisture exceeding the level of decreased availability of water. Drought-induced reduction in transpiration was quantified as a difference between actual transpiration and simulated transpiration for moist soil. The results led to conclusions that dry soil causes a significant reduction in actual evapotranspiration and its components in comparison with moist soil. Simultaneously, the effect of soil desiccation was compensated by extremely high evaporative demands of the atmosphere, so that the daily totals of evapotranspiration and its components remained sufficiently high. The high values of global radiation and saturation deficit in the air favourably influenced the water regime of the analysed forest stand in the dry period.
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Bormann, H. "Analysis of possible impacts of climate change on the hydrological regimes of different regions in Germany." Advances in Geosciences 21 (August 10, 2009): 3–11. http://dx.doi.org/10.5194/adgeo-21-3-2009.
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Abstract. In this study, the impact of climate change scenarios on the hydrological regimes of five different regions in Germany is investigated. These regions (Northwest Germany, Northeast Germany and East German basins, upper and lower Rhine, pre-Alps) differ with respect to present climate and projected climate change. The physically based SVAT-model SIMULAT is applied to theoretical soil columns based on combinations of land use, soil texture and groundwater depth to quantify climate change effects on the hydrological regime. Observed climate, measured at climate stations of the German Weather Service (1991–2007), is used for comparison with climate projections (2071–2100) generated by the regional scale climate model WETTREG. While all climate scenarios implicate an increase in precipitation in winter, a decrease in precipitation in summer and an increase in temperature, the simulated impacts on the hydrological regime are regionally different. In the Rhine region and in Northwest Germany, an increase in the annual runoff and groundwater recharge is simulated despite the increase in temperature and potential evapotranspiration. In the Eastern part of Germany and the pre-Alps, annual runoff and groundwater recharge will decrease. Due to dry conditions in summer, the soil moisture deficit will increase (in Northeast Germany and the East German basins in particular) or remain constant (Rhine region). In all regions the seasonal variability in runoff and soil moisture status will increase. Despite regional warming actual evapotranspiration will decrease in most regions except in areas with shallow groundwater tables and the lower Rhine. Although the study is limited by the fact that only one climate model was used to drive one hydrologic model, the study shows that the hydrological regime will be affected by climate change. The direction of the expected changes seems to be obvious as well as the necessity of the adaptation of future water management strategies.
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Pandey, V., and P. K. Srivastava. "INTEGRATION OF SATELLITE, GLOBAL REANALYSIS DATA AND MACROSCALE HYDROLOGICAL MODEL FOR DROUGHT ASSESSMENT IN SUB-TROPICAL REGION OF INDIA." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3 (April 30, 2018): 1347–51. http://dx.doi.org/10.5194/isprs-archives-xlii-3-1347-2018.
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Change in soil moisture regime is highly relevant for agricultural drought, which can be best analyzed in terms of Soil Moisture Deficit Index (SMDI). A macroscale hydrological model Variable Infiltration Capacity (VIC) was used to simulate the hydro-climatological fluxes including evapotranspiration, runoff, and soil moisture storage to reconstruct the severity and duration of agricultural drought over semi-arid region of India. The simulations in VIC were performed at 0.25&deg; spatial resolution by using a set of meteorological forcing data, soil parameters and Land Use Land Cover (LULC) and vegetation parameters. For calibration and validation, soil parameters obtained from National Bureau of Soil Survey and Land Use Planning (NBSSLUP) and ESA's Climate Change Initiative soil moisture (CCI-SM) data respectively. The analysis of results demonstrates that most of the study regions (>&thinsp;80&thinsp;%) especially for central northern part are affected by drought condition. The year 2001, 2002, 2007, 2008 and 2009 was highly affected by agricultural drought. Due to high average and maximum temperature, we observed higher soil evaporation that reduces the surface soil moisture significantly as well as the high topographic variations; coarse soil texture and moderate to high wind speed enhanced the drying upper soil moisture layer that incorporate higher negative SMDI over the study area. These findings can also facilitate the archetype in terms of daily time step data, lengths of the simulation period, various hydro-climatological outputs and use of reasonable hydrological model.
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Quinn, P. F., B. Ostendorf, K. Beven, and J. Tenhunen. "Spatial and temporal predictions of soil moisture patterns and evaporative losses using TOPMODEL and the GASFLUX model for an Alaskan catchment." Hydrology and Earth System Sciences 2, no. 1 (March 31, 1998): 51–64. http://dx.doi.org/10.5194/hess-2-51-1998.
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Abstract. By using topographic indices as derived from a Digital Terrain Models (DTM), it is possible to represent the heterogeneity within a landscape. This heterogeneity can reflect both long term evolutionary patterns seen in a landscape and the short term forcing of flow dynamics during storm events. By spatial analysis, the linkage between the geomorphological- hydrological-plant physiological phenomena can be examined. In this study, a direct link will be established between the topographically-driven hydrological phenomena and the eco-physiological response. The topographic distribution function of TOPMODEL is used to control the spatial and temporal flux of the channel flow and water table. The plant physiological model GAS-FLUX is used to give a spatially and temporally dissaggregated species-sensitive estimate of evapotranspiration flux. Evapotranspiration is sensitive to the vegetation phonology, to tundra community physiology and to the temperature regime. A simple linking of TOPMODEL and the GAS-FLUX model is applied to a summer snow-free period to the Imnavait catchment, Alaska (2.2 km2). A species-sensitive evapotranspiration model proved to give the highest quality results when validated against flow observations. Predicted dynamics of variable source area and the component hydrological processes are illustrated.
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Kuban, Martin, Juraj Parajka, Rui Tong, Isabella Greimeister-Pfeil, Mariette Vreugdenhil, Jan Szolgay, Silvia Kohnova, Kamila Hlavcova, Patrik Sleziak, and Adam Brziak. "The effects of satellite soil moisture data on the parametrization of topsoil and root zone soil moisture in a conceptual hydrological model." Journal of Hydrology and Hydromechanics 70, no. 3 (August 23, 2022): 295–307. http://dx.doi.org/10.2478/johh-2022-0021.
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Abstract In a previous study, the topsoil and root zone ASCAT satellite soil moisture data were implemented into three multi-objective calibration approaches of the TUW hydrological model in 209 Austrian catchments. This paper examines the model parametrization in those catchments, which in the validation of the dual-layer conceptual semi-distributed model showed improvement in the runoff simulation efficiency compared to the single objective runoff calibration. The runoff simulation efficiency of the three multi-objective approaches was separately considered. Inferences about the specific location and the physiographic properties of the catchments where the inclusion of ASCAT data proved beneficial were made. Improvements were primarily observed in the watersheds with lower slopes (median of the catchment slope less than 15 per cent) and a higher proportion of farming land use (median of the proportion of agricultural land above 20 per cent), as well as in catchments where the runoff is not significantly influenced by snowmelt and glacier runoff. Changes in the mean and variability of the field capacity parameter FC of the soil moisture regime were analysed. The values of FC decreased by 20 per cent on average. Consequently, the catchments’ water balance closure generally improved by the increase in catchment evapotranspiration during the validation period. Improvements in model efficiency could be attributed to better runoff simulation in the spring and autumn month. The findings refine recommendations regarding when hydrological modelling could consider satellite soil moisture data added to runoff signatures in calibration useful.
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Vourlitis, George L., José de Souza Nogueira, Nicolau Priante Filho, Wander Hoeger, Fernando Raiter, Marcelo Sacardi Biudes, Jose Carlos Arruda, Vinicius Buscioli Capistrano, Jorge Luiz Brito de Faria, and Francisco de Almeida Lobo. "The Sensitivity of Diel CO2 and H2O Vapor Exchange of a Tropical Transitional Forest to Seasonal Variation in Meteorology and Water Availability." Earth Interactions 9, no. 27 (December 1, 2005): 1–23. http://dx.doi.org/10.1175/ei124.1.
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Abstract Measurements of ecosystem gas exchange, meteorology, and hydrology (rainfall and soil moisture) were used to assess the seasonal patterns of, and controls on, average diel (24 h) net ecosystem CO2 exchange (NEE), evapotranspiration (E), and bulk canopy water vapor conductance (Gc) of a tropical transitional (ecotonal) forest in the Brazilian Amazon. Diel trends in E and NEE were almost completely explained by the diel variation in photosynthetic photon flux density (QPPFD), and while the QPPFD response of E varied little over the annual cycle, the QPPFD response of NEE declined substantially during the dry season, and the magnitude of hysteresis in the NEE–QPPFD response increased as well. The magnitude of the residuals for the QPPFD versus NEE response was significantly negatively correlated with total monthly rainfall and surface soil moisture and positively correlated with the maximum daily temperature and atmospheric vapor pressure deficit (V). Average daily Gc was also significantly correlated with average daily V (r = −0.72) and soil moisture (r = 0.62), suggesting strong stomatal control of NEE during drought. However, drought reduced ecosystem CO2 efflux relatively more than CO2 assimilation, suggesting that the seasonal variation in NEE was largely driven by seasonal variation in respiration. When compared with other tropical forests, seasonality in NEE was negatively correlated with annual rainfall and positively correlated with dry-season length. The relatively high sensitivity of NEE to seasonal variation in climate and water availability has profound implications for C cycling dynamics under novel climates resulting from climate and/or land-use change in the Amazon basin.
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Raddatz, R. L., G. H. B. Ash, C. F. Shaykewich, K. A. Roberge, and J. L. Graham. "First- and second-generation agrometeorological models for the prairies and simulated water-demand for potatoes." Canadian Journal of Soil Science 76, no. 3 (August 1, 1996): 297–305. http://dx.doi.org/10.4141/cjss96-036.
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On the Canadian prairies, moisture is usually the limiting factor in crop production. Occasionally, the thermal regime limits yields. At the Winnipeg Climate Centre, Environment Canada, a root-zone water-balance model simulates crop development, water-demand and water-use with daily climatological observations from across the agricultural portion of the Canadian Prairie Provinces. Simulations are used for regional-scale monitoring of the prairie’s major crops (spring wheat, barley and canola) and they have been used to quantify climatological risks. This agrometeorological model is termed a first-generation model as potential evapotranspiration is estimated empirically from Baier and Robertson’s simplest regression equation.A coupled atmosphere-crop-soil agrometeorological model has also been developed for crop monitoring on the prairies. This model generates atmospheric boundary layer profiles at climatological-sites using upper-air analyses and surface characteristics. The crop-soil boundary layer consists of the growing crop, and the top, root and sub-zones of the soil. Evapotranspiration is calculated deterministically from the air’s water vapour density deficit. The calculation is modulated by aerodynamic, canopy and soil resistances. The coupled approach is termed a second-generation model.The re-formulation of the coupled model to simulate the phenology and water-demand of a newly significant crop, potatoes, is described. Comparison with 1994 and 1995 test-plot observations of fractional leaf area and rooting depth suggests that the potato phenology simulation requires further development. Estimates of daily crop water-demand are similar but show greater day-today variation than values generated by a first-generation Baier and Robertson procedure. Key words: Regional modelling, soil moisture, phenology, crop water-demand, potatoes
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Nazarenko, N. N. "Coenomorphs as phytometers of biotopes." Biosystems Diversity 24, no. 1 (January 28, 2016): 8–14. http://dx.doi.org/10.15421/011602.
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The article describes the A.L. Belgard system of vascular plant species coenomorphs as indicators of biotopes by using standardized Y.P. Didukh phytometer scales for 12 environmental factors. The classification and ordination of coenomorphs in the phytometer space was performed by using algorithms of discriminant analysis. The analysis is based on 2,186 species of the vascular plant flora of Ukraine. The classification accuracy was around 80% and above, the least homogenous was the petrophyte coenomorph. The validity of identification of ruderal coenomorphs was proved as an indicator of biotopes with increased content of soil nitrogen. Analysis of the a posteriori probability of species attribution to a coenomorph supports the validity of distinguishing transitional coenomorphs. Their number is small and each group contains a small number of species. The principal factors of classifying species by coenomorph are (in descending order of significance): minimum soil moisture, minimum light (shade), impoverishment of salts in the soil solution, high porosity of soil and impoverishment of carbonates of calcium in the soil and maximum values for radiation balance. The analysis of the distribution of coenomorphs in the space of the square of Mahalanobis distances and the ordination in the discriminant functions axis has determined the ranking of coenomorph of biotope and coenotic substitution: soil moisture (first discriminant function), radiation balance and shade (second discriminant function), salt regime and soil aeration (third discriminant function). For the vegetation of Ukraine this ordination of coenomorphs corresponds to the zonal factors of the distribution of biotopes and their limiting factors and the factors determining A.L. Belgard’s typology of natural and artificial forests: soil moisture, salinity of the soil solution, light conditions. The coenomorph optima for the principal factors have been defined in phytometer scales. This allows coenomorphs to be used as biotope phytometers and provides a preliminary assessment of those species whose place in the scales has not yet been determined. Analysis of posterior probabilities enabled us to determine the transitional coenomorphs, which are typical for ecotones between zonal and intrazonal vegetational ecosystems of Ukraine.
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Radu, Danielle D., and Tim P. Duval. "Response of hydrology and CO<sub>2</sub> flux to experimentally altered rainfall frequency in a temperate poor fen, southern Ontario, Canada." Biogeosciences 15, no. 13 (July 2, 2018): 3937–51. http://dx.doi.org/10.5194/bg-15-3937-2018.
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Abstract. Predicted changes to the precipitation regime in many parts of the world include intensifying the distribution into lower frequency, large magnitude events. The corresponding alterations to the soil moisture regime may affect plant growth and soil respiration, particularly in peatlands, where large stores of organic carbon are due to gross ecosystem productivity (GEP) exceeding ecosystem respiration (ER). This study uses lab monoliths corroborated with field measurements to examine the effect of changing rainfall frequency on peatland moisture controls on CO2 uptake in an undisturbed cool temperate poor fen. Lab monoliths and field plots containing mosses, sedges, or shrubs received either 2.3, 1, or 0.5 precipitation events per week, with total rainfall held constant. Decreasing rain frequency led to lower near-surface volumetric moisture content (VMC), water table (WT), and soil tension for all vegetation types, with minimal effect on evapotranspiration. The presence of sedges in particular led to soil tensions of ≥100 cm of water for a sizeable duration (37 %) of the experiment. Altered rainfall frequencies affected GEP but had little effect on ER; overall, low-frequency rain led to a reduced net CO2 uptake for all three vegetation types. VMC had a strong control on GEP and net ecosystem exchange (NEE) of the Sphagnum capillifolium monoliths, and decreasing rainfall frequency influenced these relationships. Overall, communities dominated by mosses became net sources of CO2 after 3 days without rain, whereas sedge communities remained net sinks for up to 14 days without rain. The results of this study demonstrate the hydrological controls of peatland CO2 exchange dynamics influenced by changing precipitation frequency; furthermore, they suggest these predicted changes in frequency will lead to increased sedge GEP but limit the carbon-sink function of peatlands.
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O'Donnell, J. A., J. W. Harden, A. D. McGuire, and V. E. Romanovsky. "Exploring the sensitivity of soil carbon dynamics to climate change, fire disturbance and permafrost thaw in a black spruce ecosystem." Biogeosciences Discussions 7, no. 6 (December 6, 2010): 8853–93. http://dx.doi.org/10.5194/bgd-7-8853-2010.
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Abstract. In the boreal region, soil organic carbon (OC) dynamics are strongly governed by the interaction between wildfire and permafrost. Using a combination of field measurements, numerical modeling of soil thermal dynamics, and process-based modeling of OC dynamics, we tested the sensitivity of soil OC storage to a suite of individual climate factors (air temperature, soil moisture, and snow depth) and fire severity. We also conducted sensitivity analyses to explore the combined effects of fire-moisture interactions and snow seasonality on OC storage. OC losses were calculated as the difference in OC stocks after three fire cycles (~450 years) following a prescribed step-change in climate and/or fire. Across single-factor scenarios, our findings indicate that warmer air temperatures resulted in the largest soil OC losses (5.3 kg C m−2), whereas dry soil conditions alone (in the absence of wildfire) resulted in the smallest carbon losses (0.1 kg C m−2). Increased fire severity resulted in carbon loss of 3.3 kg C m−2, whereas changes in snow depth resulted in smaller OC losses (2.1–2.2 kg C m−2). Across multiple climate factors, we observed larger OC losses than for single-factor scenarios. For instance, high fire severity regime associated with warmer and drier conditions resulted in OC losses of 6.1 kg C m−2, whereas a low fire severity regime associated with warmer and wetter conditions resulted in OC losses of 5.6 kg C m−2. A longer snow-free season associated with future warming resulted in OC losses of 5.4 kg C m−2. Soil climate was the dominant control on soil OC loss, governing the sensitivity of microbial decomposers to fluctuations in temperature and soil moisture; this control, in turn, is governed by interannual changes in active layer depth. Transitional responses of the active layer depth to fire regimes also contributed to OC losses, primarily by determining the proportion of OC into frozen and unfrozen soil layers. Carbon cycle feedbacks from the boreal region to the climate system will clearly depend upon these interactions among climate drivers, fire regime characteristics, and permafrost dynamics.
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Kraft, Basil, Martin Jung, Marco Körner, Sujan Koirala, and Markus Reichstein. "Towards hybrid modeling of the global hydrological cycle." Hydrology and Earth System Sciences 26, no. 6 (March 23, 2022): 1579–614. http://dx.doi.org/10.5194/hess-26-1579-2022.
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Abstract. State-of-the-art global hydrological models (GHMs) exhibit large uncertainties in hydrological simulations due to the complexity, diversity, and heterogeneity of the land surface and subsurface processes, as well as the scale dependency of these processes and associated parameters. Recent progress in machine learning, fueled by relevant Earth observation data streams, may help overcome these challenges. But machine learning methods are not bound by physical laws, and their interpretability is limited by design. In this study, we exemplify a hybrid approach to global hydrological modeling that exploits the data adaptivity of neural networks for representing uncertain processes within a model structure based on physical principles (e.g., mass conservation) that form the basis of GHMs. This combination of machine learning and physical knowledge can potentially lead to data-driven, yet physically consistent and partially interpretable hybrid models. The hybrid hydrological model (H2M), extended from Kraft et al. (2020), simulates the dynamics of snow, soil moisture, and groundwater storage globally at 1∘ spatial resolution and daily time step. Water fluxes are simulated by an embedded recurrent neural network. We trained the model simultaneously against observational products of terrestrial water storage variations (TWS), grid cell runoff (Q), evapotranspiration (ET), and snow water equivalent (SWE) with a multi-task learning approach. We find that the H2M is capable of reproducing key patterns of global water cycle components, with model performances being at least on par with four state-of-the-art GHMs which provide a necessary benchmark for H2M. The neural-network-learned hydrological responses of evapotranspiration and grid cell runoff to antecedent soil moisture states are qualitatively consistent with our understanding and theory. The simulated contributions of groundwater, soil moisture, and snowpack variability to TWS variations are plausible and within the ranges of traditional GHMs. H2M identifies a somewhat stronger role of soil moisture for TWS variations in transitional and tropical regions compared to GHMs. With the findings and analysis, we conclude that H2M provides a new data-driven perspective on modeling the global hydrological cycle and physical responses with machine-learned parameters that is consistent with and complementary to existing global modeling frameworks. The hybrid modeling approaches have a large potential to better leverage ever-increasing Earth observation data streams to advance our understandings of the Earth system and capabilities to monitor and model it.
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O'Donnell, J. A., J. W. Harden, A. D. McGuire, and V. E. Romanovsky. "Exploring the sensitivity of soil carbon dynamics to climate change, fire disturbance and permafrost thaw in a black spruce ecosystem." Biogeosciences 8, no. 5 (May 27, 2011): 1367–82. http://dx.doi.org/10.5194/bg-8-1367-2011.
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Abstract. In the boreal region, soil organic carbon (OC) dynamics are strongly governed by the interaction between wildfire and permafrost. Using a combination of field measurements, numerical modeling of soil thermal dynamics, and mass-balance modeling of OC dynamics, we tested the sensitivity of soil OC storage to a suite of individual climate factors (air temperature, soil moisture, and snow depth) and fire severity. We also conducted sensitivity analyses to explore the combined effects of fire-soil moisture interactions and snow seasonality on OC storage. OC losses were calculated as the difference in OC stocks after three fire cycles (~500 yr) following a prescribed step-change in climate and/or fire. Across single-factor scenarios, our findings indicate that warmer air temperatures resulted in the largest relative soil OC losses (~5.3 kg C m−2), whereas dry soil conditions alone (in the absence of wildfire) resulted in the smallest carbon losses (~0.1 kg C m−2). Increased fire severity resulted in carbon loss of ~3.3 kg C m−2, whereas changes in snow depth resulted in smaller OC losses (2.1–2.2 kg C m−2). Across multiple climate factors, we observed larger OC losses than for single-factor scenarios. For instance, high fire severity regime associated with warmer and drier conditions resulted in OC losses of ~6.1 kg C m−2, whereas a low fire severity regime associated with warmer and wetter conditions resulted in OC losses of ~5.6 kg C m−2. A longer snow-free season associated with future warming resulted in OC losses of ~5.4 kg C m−2. Soil climate was the dominant control on soil OC loss, governing the sensitivity of microbial decomposers to fluctuations in temperature and soil moisture; this control, in turn, is governed by interannual changes in active layer depth. Transitional responses of the active layer depth to fire regimes also contributed to OC losses, primarily by determining the proportion of OC into frozen and unfrozen soil layers.
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Kotovych, O. V. "The hydrological cycle in the ravine oak forests of steppe Prydniprovia." Fundamental and Applied Soil Science 15, no. 1-2 (January 14, 2014): 89–100. http://dx.doi.org/10.15421/041409.
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The characteristic of the hydrological cycle in the ravine oak forest is given in the work. In its preparation, we proceeded from assumption about the participation of groundwater in water feeding of wood vegetation. To confirm or refute this the term average groundwater depth, the changes in its long-term, seasonal and intraday level dynamics were analyzed. The intra-annual structure of the groundwater regime was established, while in the structure the three specific periods were identified – winter-spring recovery, spring-autumn recession and autumn recovery. It was established that the duration of the hydrological year between the beginning of winter-spring recovery and the ending of autumn recovery was about 11.5 months. Most often, the hydrological year flows between January and December of neighboring hydrological years. The groundwater depth during the observation period ranged from 7.65 to 10.08 m from the surface. The amplitude of level changes between seasons was 0.57–1.59 m. The speed of rise and fall level was set, while the instability of characterized indicators was observed, that is closely related to the temperature of atmospheric air of the previous period. The annual dynamics of groundwater level is compensatory in nature, in which the spring-autumn recession is compensated autumn and winter-spring recovery. From the position of winter minimum level and the deviation of the average annual rainfall norms, it was found that the course of the annual changes level has a close correlation with the amount of precipitation. Intraday dynamics of level conditions during the vegetation period has stepwise, descending character, which means that there is no direct connection of groundwater with woody vegetation. It was found that at the absence of available groundwater, the incoming part of the water balance was determined by the vegetation period precipitation and the moisture contained in the soil at the beginning of the vegetation period. The amount of precipitation of the vegetation period, excluding precipitation detained by the cover and litter, during the observation period was over 292 mm. Dynamics of soil moisture in 1.5 meters layer showed that the most dynamic changes in moisture took place in the upper meter of soil. During the non-growing period in the 1.5 meters layer up to 252 mm of moisture is accumulated. The total amount of rainfall and soil moisture in the 1.5 meters layer of soil at the beginning of vegetative period averages 542 mm, 46 % of which is soil moisture, and the remaining 54 % is the precipitation moisture. The average annual evapotranspiration coefficient is calculated from the ratio of the amount of soil moisture at the beginning of the vegetative period and all vegetative period precipitation to evapotranspiration of appropriate period of time. In this approach the figure for ravined oak forests is 0.78, 0.63 – for steppe plots of virgin land. The general moisture conditions prevailing here are local, are formed under the influence of geomorphological features on the background of climatic conditions and are responsible to the intrazonal type.
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Jiang, Yelin, Meijian Yang, Weiguang Liu, Koushan Mohammadi, and Guiling Wang. "Eco-hydrological responses to recent droughts in tropical South America." Environmental Research Letters 17, no. 2 (February 1, 2022): 024037. http://dx.doi.org/10.1088/1748-9326/ac507a.
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Abstract This study assesses the ecohydrological effects of recent meteorological droughts in tropical South America based on multiple sources of data, and investigates the possible mechanisms underlying the drought response and recovery of different ecohydrological systems. Soil drought response and recovery lag behind the meteorological drought, with delays longer in the dry region (Nordeste) than in the wet region (Amazonia), and longer in deep soil than in shallow soil. Evapotranspiration (ET) and vegetation in Nordeste are limited by water under normal conditions and decrease promptly in response to the onset of shallow soil drought. In most of the Amazon where water is normally abundant, ET and vegetation indices follow an increase-then-decrease pattern, increase at the drought onset due to increased sunshine and decrease when the drought is severe enough to cause a shift from an energy-limited regime to a water-limited regime. After the demise of meteorological droughts, ET and vegetation rapidly recover in Nordeste with the replenishment of shallow soil moisture (SM), but take longer to recover in southern Amazon due to their dependence on deep SM storage. Following severe droughts, the negative anomalies of ET and vegetation indices in southern Amazon tend to persist well beyond the end of soil drought, indicating drought-induced forest mortality that is slow to recover from. Findings from this study may have implications on the possibility of a future forest dieback as drought is projected to become more frequent and more severe in a warmer climate.
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Makarychev, S. V. "EVALUATION OF THE GROWING CONDITIONS OF SEA-BUCKTHORN PLANTATIONS UNDER INUNDATIVE IRRIGATION." Vestnik Altajskogo gosudarstvennogo agrarnogo universiteta, no. 9 (2021): 30–36. http://dx.doi.org/10.53083/1996-4277-2021-203-30-36.
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Sea-buckthorn grows well on slope lands that are high-ly drained and lack stagnant water. The optimum soil mois-ture content for sea-buckthorn corresponds to 70% of the lowest moisture capacity. Under continuous soil moisture deficit, the leaf surface area decreased, the fruits were poorly set as a result of ovary drop during the first half of the growing season, and berry size decreased. In this re-gard, the study of the water regime of the soil under sea-buckthorn plantations the possibility of its regulation re-mained quite topical. The available moisture in the humus horizons of chernozem in May 2004 corresponded to a satisfactory level. At the end of summer, the moisture con-tent of the chernozem decreased to unsatisfactory state. As a result, the plants experienced water deprivation throughout the growing season. Naturally, the need arose for irrigation, especially in June and August with irrigation rates of 490 and 280 t per m3, respectively. In the underly-ing horizons, the soil moisture deficit was weaker. In the humus horizons, the available moisture in the chernozem in the middle of the slope did not differ much from the mois-ture content at its top. At the same time, in the transitional BC layer in the second half of summer, the available mois-ture content was significantly higher. This difference was also found in the parent rock. In the lower part of theslope, the one-meter soil layer contained a greater amount of moisture which contributed to the decrease of its deficit during the entire growing season. This was especially no-ticeable in the illuvial horizon and parent rock. In the sec-ond half of summer,the available moisture content here remained higher than in the upper slope sites. In conclu-sion, it should be noted that only humus-accumulative hori-zons A (arable) + AB needed irrigation with different irriga-tion rates depending on the location of the sea-buckthorn plantations on the slope and their growth features.
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Blanusa, Tijana, Eleni Vysini, and Ross W. F. Cameron. "Growth and Flowering of Petunia and Impatiens: Effects of Competition and Reduced Water Content Within a Container." HortScience 44, no. 5 (August 2009): 1302–7. http://dx.doi.org/10.21273/hortsci.44.5.1302.
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The primary objective of this research was to determine how the presence of more than one plant and more than one species in a container influence plant quality, particularly when the volume of water given to the container is reduced. Petunia ×hybrida ‘Hurrah White’ and Impatiens ‘Cajun Violet’ were chosen as typical bedding plant species. Plants were grown in 2 l containers either under “100% ETp” (i.e., replacing all the water lost by evapotranspiration in the previous 24 h) or under a moisture-restrictive regime of “25% ETp,” in which plants received 25% of the “100% ETp” value. An ancillary experiment investigated whether low watering resulted in floral buds being aborted. Results demonstrated that watering requirements of Petunia under “100% ETp” (i.e., replacing all the water lost by evapotranspiration in the previous 24 h) were on average 30% greater than those of Impatiens. However, when two Petunia plants were growing in the same container, the volume of water required to maintain soil moisture content at container capacity was on average only 10% greater than for a single plant. Under a “25% ETp” regime in which plants received 25% of the “100% ETp” value, flower number, plant height, and flower size were reduced by 50%, 33%, and 13%, respectively, in Petunia compared with “100% ETp.” For example, flower numbers decreased from an average of 71 to 33 flowers per plant in “100% ETp” and “25% ETp,” respectively. Petunia plants in the “25% ETp” regime, however, were more efficient at producing both biomass and flowers in relation to the volume of water applied. Petunia plants that experienced both competition from other plants in the container and lower irrigation rates had enhanced efficiency of flower production (i.e., more flowers per unit biomass). For Impatiens, however, the growing of single plants at “25% ETp” was plausible, but the addition of a Petunia plant at “25% ETp” was detrimental to plant quality (Impatiens flower numbers reduced by 75%).
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Miller, Luke, George Vellidis, and Timothy Coolong. "Comparing a Smartphone Irrigation Scheduling Application with Water Balance and Soil Moisture-based Irrigation Methods: Part II—Plasticulture-grown Watermelon." HortTechnology 28, no. 3 (June 2018): 362–69. http://dx.doi.org/10.21273/horttech04014-18.
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A new smartphone irrigation scheduling application (VegApp) was compared with current irrigation scheduling recommendations and an automated soil moisture sensor (SMS)–based irrigation system in southern Georgia during Spring 2016 and 2017. Plants were grown using plastic mulch and drip irrigation following standard production practices for watermelon (Citrullus lanatus) in Georgia. The VegApp irrigation regime was based on evapotranspiration (ETo) values calculated from real-time data collected from a nearby weather station. Current irrigation scheduling recommendations use a water balance (WB) method. The WB method uses historic averages for determining ETo rates for the season. Water applied, soil water tension at 6-, 10-, and 14-inch depths, yield, and fruit quality were evaluated. In 2016, the SMS-based irrigation plots applied the least water. In 2017, the lowest amount of water was applied to plants grown using the VegApp. Total marketable yields were not significantly affected by irrigation regime. However, 45-count fruit yields were affected by irrigation in 2017. Plants grown using SMS-based irrigation had significantly higher yields of 45-count fruit than those grown using the WB method. Irrigation water use efficiency (IWUE) was affected by irrigation treatment and year. The SMS-irrigated plants had the greatest IWUE, although it was not significantly different from plants grown using the VegApp irrigation program. Internal quality parameters including, firmness, hollow heart, and total soluble solids (TSS) were not significantly affected by irrigation scheduling during the study. The results suggest that overall water applications may be reduced and yields maintained when using VegApp compared with traditional WB methods of irrigation scheduling.
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Garrigues, S., A. Verhoef, E. Blyth, A. Wright, B. Balan-Sarojini, EL Robinson, S. Dadson, A. Boone, S. Boussetta, and G. Balsamo. "Capability of the variogram to quantify the spatial patterns of surface fluxes and soil moisture simulated by land surface models." Progress in Physical Geography: Earth and Environment 45, no. 2 (February 15, 2021): 279–93. http://dx.doi.org/10.1177/0309133320986147.
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Up to now, relatively little effort has been dedicated to the quantitative assessment of the differences in spatial patterns of model outputs. In this paper, we employed a variogram-based methodology to quantify the differences in the spatial patterns of root-zone soil moisture, net radiation, and latent and sensible heat fluxes simulated by three land surface models (SURFEX/ISBA, JULES and CHTESSEL) over three European geographic domains – namely, UK, France and Spain. The model output spatial patterns were quantified through two metrics derived from the variogram: i) the variogram sill, which quantifies the degree of spatial variability of the data; and ii) the variogram integral range, which represents the spatial length scale of the data. The higher seasonal variation of the spatial variability of sensible and latent heat fluxes over France and Spain, compared to the UK, is related to a more frequent occurrence of a soil-moisture-limited evapotranspiration regime during summer dry spells in the south of France and Spain. The small differences in spatial variability of net radiation between models indicate that the spatial patterns of net radiation are mostly driven by the climate forcing data set. However, the models exhibit larger differences in latent and sensible heat flux spatial variabilities, which are related to their differences in i) soil and vegetation ancillary datasets and ii) physical process representation. The highest discrepancies in spatial patterns between models are observed for soil moisture, which is mainly related to the type of soil hydraulic function implemented in the models. This work demonstrates the capability of the variogram to enhance our understanding of the spatiotemporal structure of the uncertainties in land surface model outputs. Therefore, we strongly encourage the implementation of the variogram metrics in model intercomparison exercises.
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Bultot, F., G. L. Dupriez, and D. Gellens. "Estimated annual regime of energy-balance components, evapotranspiration and soil moisture for a drainage basin in the case of a CO2 doubling." Climatic Change 12, no. 1 (February 1988): 39–56. http://dx.doi.org/10.1007/bf00140263.
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Reich, Marvin, Michal Mikolaj, Theresa Blume, and Andreas Güntner. "Reducing gravity data for the influence of water storage variations beneath observatory buildings." GEOPHYSICS 84, no. 1 (January 1, 2019): EN15—EN31. http://dx.doi.org/10.1190/geo2018-0301.1.
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Ground-based gravimetry is increasingly used to study mass distributions and mass transport below the earth surface. The gravity effect of local water storage variations can be large and should be accounted for in the interpretation of these data. However, the effect of hydrologic mass changes in the immediate vicinity of the gravimeter is not considered in standard routines for separating unwanted signal components. This applies in particular to the effect of the buildings in which gravimeters are installed. The building shields the underlying soil from precipitation and evapotranspiration and thus directly affects the water storage dynamics in the near-field of the gravimeter. A combined approach of in situ soil moisture observations and hydrologic modeling was used to quantify the altered water storage variations below observatory buildings. Subsequently, the errors caused by different estimation approaches for this umbrella effect in hydrogravitational computations were assessed. Depending on the site characteristics, the errors range from 4.1 to [Formula: see text] for the intra-annual amplitude when natural soil moisture data are considered for modeling the umbrella effect, and they range from 4.1 to [Formula: see text] when assuming no gravity change within 5 m below the building. These results were condensed to general recommendations, leading to a new simple and broadly applicable method to reduce observed gravity data for building effects, given basic information about the gravimeter location, building dimensions, climatic regime, and soil type of the observation site. This new reduction approach indicates errors of the intra-annual amplitude from 1.9 to [Formula: see text].
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Miller, Luke, George Vellidis, Osama Mohawesh, and Timothy Coolong. "Comparing a Smartphone Irrigation Scheduling Application with Water Balance and Soil Moisture-based Irrigation Methods: Part I—Plasticulture-grown Tomato." HortTechnology 28, no. 3 (June 2018): 354–61. http://dx.doi.org/10.21273/horttech04010-18.
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A new smartphone vegetable irrigation scheduling application (VegApp) was compared with current irrigation scheduling recommendations and soil moisture sensor (SMS)–based irrigation for growing tomato (Solanum lycopersicum) in southern Georgia during Spring 2016 and 2017. Plants were grown using plastic mulch and drip irrigation following standard production. The VegApp-scheduled irrigation based on crop evapotranspiration (ETc) values calculated daily from meteorological data retrieved from nearby weather stations, whereas ETc rates for current water balance (WB)–based recommendations were calculated from historic averages for the region. Water usage, soil moisture tension, fruit yield and quality, and foliar macronutrient content were measured. In 2016, plants grown using SMS-based irrigation applied the least water followed by the VegApp- and WB-grown plants. In 2017, WB-treated plants received the least water, followed by VegApp- and SMS-grown plants. Total marketable yields were similar among treatments and years. Irrigation water use efficiency (IWUE) varied between year and irrigation regime, with SMS-grown plants having a significantly greater IWUE than the other treatments in 2016. Plants irrigated using the VegApp had a greater IWUE than SMS-irrigated plants in 2017. Differences in IWUE were largely the result of variable irrigation volumes and not changes in yield. Fruit total soluble solids (TSS) were unaffected by treatment in either study year. Fruit pH was affected by irrigation treatment in 2017. Foliar nitrogen concentrations were affected by irrigation regime in 2017, with VegApp-grown plants having significantly greater concentrations of foliar N than other irrigation treatments. The results of this study suggest that the VegApp could be a reliable tool that can be used by growers to produce yields comparable to currently accepted irrigation scheduling practices and reduce water use in some seasons.
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Booth, Eric G., and Steven P. Loheide. "Effects of evapotranspiration partitioning, plant water stress response and topsoil removal on the soil moisture regime of a floodplain wetland: implications for restoration." Hydrological Processes 24, no. 20 (September 3, 2010): 2934–46. http://dx.doi.org/10.1002/hyp.7707.
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Franchini, M., A. M. Hashemi, and P. E. O’Connell. "Climatic and basin factors affecting the flood frequency curve: PART II – A full sensitivity analysis based on the continuous simulation approach combined with a factorial experimental design." Hydrology and Earth System Sciences 4, no. 3 (September 30, 2000): 483–98. http://dx.doi.org/10.5194/hess-4-483-2000.
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Abstract. The sensitivity analysis described in Hashemi et al. (2000) is based on one-at-a-time perturbations to the model parameters. This type of analysis cannot highlight the presence of parameter interactions which might indeed affect the characteristics of the flood frequency curve (ffc) even more than the individual parameters. For this reason, the effects of the parameters of the rainfall, rainfall runoff models and of the potential evapotranspiration demand on the ffc are investigated here through an analysis of the results obtained from a factorial experimental design, where all the parameters are allowed to vary simultaneously. This latter, more complex, analysis confirms the results obtained in Hashemi et al. (2000) thus making the conclusions drawn there of wider validity and not related strictly to the reference set selected. However, it is shown that two-factor interactions are present not only between different pairs of parameters of an individual model, but also between pairs of parameters of different models, such as rainfall and rainfall-runoff models, thus demonstrating the complex interaction between climate and basin characteristics affecting the ffc and in particular its curvature. Furthermore, the wider range of climatic regime behaviour produced within the factorial experimental design shows that the probability distribution of soil moisture content at the storm arrival time is no longer sufficient to explain the link between the perturbations to the parameters and their effects on the ffc, as was suggested in Hashemi et al. (2000). Other factors have to be considered, such as the probability distribution of the soil moisture capacity, and the rainfall regime, expressed through the annual maximum rainfalls over different durations. Keywords: Monte Carlo simulation; factorial experimental design; analysis of variance (ANOVA)
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Oliveira, Rívia de Souza Vaz, Leandro Caixeta Salomão, Hélber Souto Morgado, Cleiton Mateus Sousa, and Henrique Fonseca E. de Oliveira. "Growth and production of basil under different luminosity and water replacement levels." Horticultura Brasileira 38, no. 3 (September 2020): 324–28. http://dx.doi.org/10.1590/s0102-053620200314.
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ABSTRACT Basil is used as spice and for medicinal purposes. Its growth is influenced by environmental factors, mainly soil moisture and air temperature. Thus, this study was installed to evaluate growth and production of basil under different levels of luminosity and water replacement. The experimental design was completely randomized, with six replicates, arranged in split plot scheme, with three luminosity levels in the plots (full sun, 50% and 70% shading) and four water replacement levels in the subplots (25, 50, 75 and 100% ETc). We evaluated plant height, stalk diameter, number of leaves and branches, root system volume, the largest root length, fresh and dry mass of roots and leaves. Data were submitted to variance analysis to observe significant differences between treatments and interactions. Luminosity effects were evaluated using Tukey test (p≤0.05%) and the effects of water regime, with the aid of regression analysis. According to data, 50% shading and 100% water replacement, lost through crop evapotranspiration, resulted in higher values of plant height, stalk diameter, branch growth, fresh and dry mass of leaves, and number of leaves. Full sun environment and 100% water replacement provided an increase in root dry mass and volume.
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Spicer, Robert, Paul Valdes, Alice Hughes, Jian Yang, Teresa Spicer, Alexei Herman, and Alexander Farnsworth. "New insights into the thermal regime and hydrodynamics of the early Late Cretaceous Arctic." Geological Magazine 157, no. 10 (May 30, 2019): 1729–46. http://dx.doi.org/10.1017/s0016756819000463.
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AbstractThe Arctic is warming faster than anywhere else of comparable size on Earth, impacting global climate feedbacks and the Arctic biota. However, a warm Arctic is not novel. The Late Cretaceous fossil record of the region enables a detailed reconstruction of polar environmental conditions, and a thriving extinct ecosystem, during a previous 'hothouse’ global climate. Using leaf form (physiognomy) and tree ring characteristics we reconstruct Cenomanian to Coniacian polar thermal and hydrological regimes over an average annual cycle at eight locations in NE Russia and northern Alaska. A new high spatial resolution (∼1 km) WorldClim2 calibration of the Climate Leaf Analysis Multivariate Program (CLAMP) yields results similar to, but often slightly warmer than, previous analyses, but also provides more detailed insights into the hydrological regime through the return of annual and seasonal vapour pressure deficit (VPD), potential evapotranspiration (PET) estimates and soil moisture, as well as new thermal overviews through measures of thermicity and growing degree days. The new results confirm the overall warmth of the region, particularly close to the Arctic Ocean, but reveal strong local differences that may be related to palaeoelevation in the Okhotsk–Chukotka Volcanogenic Belt in NE Russia. While rainfall estimates have large uncertainties due to year-round wet soils in most locations, new measures of VPD and PET show persistent high humidity, but with notably drier summers at all the Arctic sites.
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Lamb, Eric G., and William Megill. "The Shoreline Fringe Forest and Adjacent Peatlands of the Southern Central British Columbia Coast." Canadian Field-Naturalist 117, no. 2 (April 1, 2003): 209. http://dx.doi.org/10.22621/cfn.v117i2.684.
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Four distinct vegetation types are found in close proximity along an exposed section of the southern central coast of British Columbia. A coastal fringe of coniferous forest a few hundred metres wide is separated by a steep ecotone from an inland peatland-forest complex. The objectives of this study were (1) to describe the plant communities along the transition from forest to peatland, and (2) to identify some of the major environmental factors associated with those communities using indicator plant analysis. The coastal forest is dominated by Thuja plicata, Tsuga heterophylla, Picea sitchensis, and Chamaecyparis nootkatensis. Characteristic understory species include Gaultheria shallon and Blechnum spicant. Inland from the coastal forest are transitional forest stands with a species-rich understory including Cornus canadensis, Hylocomium splendens, and Vaccinium parvifolium. The peatlands are poor fens characterized by thickets of Pinus contorta and Chamaecyparis nootkatensis among open areas dominated by species such as Sphagnum sp., Empetrum nigrum, Juniperus communis, and bogs characterized by Myrica gale, Eriophorum angustifolium, and Sanguisorba officinalis. Indicator plant analysis identified differences in the ground surface materials, soil moisture and nutrient regime between the vegetation types. The general trend is for an increase in soil moisture from the forest vegetation to the peatlands and a concurrent change from the Mor humus forms that dominate the coastal forest floor to the surface groundwater table of the peatlands. These environmental differences between forest and peatland are likely related to the steeper slopes typically found in the fringe forest vegetation.
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Mizuochi, Hiroki, Agnès Ducharne, Frédérique Cheruy, Josefine Ghattas, Amen Al-Yaari, Jean-Pierre Wigneron, Vladislav Bastrikov, Philippe Peylin, Fabienne Maignan, and Nicolas Vuichard. "Multivariable evaluation of land surface processes in forced and coupled modes reveals new error sources to the simulated water cycle in the IPSL (Institute Pierre Simon Laplace) climate model." Hydrology and Earth System Sciences 25, no. 4 (April 22, 2021): 2199–221. http://dx.doi.org/10.5194/hess-25-2199-2021.
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Abstract. Evaluating land surface models (LSMs) using available observations is important for understanding the potential and limitations of current Earth system models in simulating water- and carbon-related variables. To reveal the error sources of a LSM, five essential climate variables have been evaluated in this paper (i.e., surface soil moisture, evapotranspiration, leaf area index, surface albedo, and precipitation) via simulations with the IPSL (Institute Pierre Simon Laplace) LSM ORCHIDEE (Organizing Carbon and Hydrology in Dynamic Ecosystems) model, particularly focusing on the difference between (i) forced simulations with atmospheric forcing data (WATCH Forcing Data ERA-Interim – WFDEI) and (ii) coupled simulations with the IPSL atmospheric general circulation model. Results from statistical evaluation, using satellite- and ground-based reference data, show that ORCHIDEE is well equipped to represent spatiotemporal patterns of all variables in general. However, further analysis against various landscape and meteorological factors (e.g., plant functional type, slope, precipitation, and irrigation) suggests potential uncertainty relating to freezing and/or snowmelt, temperate plant phenology, irrigation, and contrasted responses between forced and coupled mode simulations. The biases in the simulated variables are amplified in the coupled mode via surface–atmosphere interactions, indicating a strong link between irrigation–precipitation and a relatively complex link between precipitation–evapotranspiration that reflects the hydrometeorological regime of the region (energy limited or water limited) and snow albedo feedback in mountainous and boreal regions. The different results between forced and coupled modes imply the importance of model evaluation under both modes to isolate potential sources of uncertainty in the model.
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Hartz, T. K. "Drip-irrigation Scheduling for Fresh-market Tomato Production." HortScience 28, no. 1 (January 1993): 35–37. http://dx.doi.org/10.21273/hortsci.28.1.35.
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Drip-irrigation scheduling techniques for fresh-market tomato (Lycopersicon esculentum Mill.) production were compared in three growing seasons (1989-91). Three regimes were evaluated: EPK [reference evapotranspiration (ETo, corrected Penman) × programmed crop coefficients], ECC (ET0 × a crop coefficient based on estimated percent canopy coverage), and SMD (irrigation at 20% available soil moisture depletion). EPK coefficients ranged from 0.2 (crop establishment) to 1.1 (full canopy development). Percent canopy coverage was estimated from average canopy width ÷ row width. Irrigation in the SMD treatment was initiated at -24 kPa soil matric tension, with recharge limited to 80% of daily ET0. The EPK and ECC regimes gave similar fresh fruit yields and size distributions in all years. With the EPK scheduling technique, there was no difference in crop response between daily irrigation and irrigation three times per week. In all seasons, ECC scheduling resulted in less total water applied than EPK scheduling and averaged 76% of seasonal ET0 vs. 86% for EPK. Irrigating at 20% SMD required an average of only 64% of seasonal ET0; marketable yield was equal to the other scheduling techniques in 1989 and 1991, but showed a modest yield reduction in 1990. Using an SMD regime to schedule early season irrigation and an ECC system to guide application from mid-season to harvest may be the most appropriate approach for maximizing water-use efficiency and crop productivity.
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Pankiv, Zenoviy, and Taras Yamelynets. "Ferrum concretions forms in the mollic gley soils of Low (Male) Polissya." Polish Journal of Soil Science 53, no. 1 (June 22, 2020): 137. http://dx.doi.org/10.17951/pjss.2020.53.1.137.
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<p>In the humid conditions, the most common ground forms are the ferruginous ones: ferrum concretions, marsh ore, ocher spots, etc. Mollic gley soils are widely spread along the periphery of marshes and are formed under the influence of mollic and gley processes on various soil-forming rocks under conditions of sporadically pulsating water regime and excessive moisture under the meadow and swamp biocenoses. The ferrum concretions are characteristic of all genetic horizons of mollic gley soils, except for the soil-forming rock, and their content ranges from 3.3% in the mollic to 47.1% in the lower transitional horizon. The gross iron content in the fine mollic gley soils, as well as in the ferrum concretions forms, increases with depth, and the maximum values are characteristic of the lower transition horizon. The lowest values of the gross iron content are characteristic of the fine soil-forming rock (16.0 mg / 100 g soil) and the mollic soil (66.4 mg / 100 g soil). It was established that the gross chemical content of the ferrum concretions forms is dominated by the iron oxides with the highest content in the ferrum concretions of the mollic soils (48.75%). Also the ferrum concretions forms of iron are characterized by a rather high content of aluminum oxides (5.59–7.92%). The highest values of the accumulation coefficient are characteristic of the iron oxide (Kx = 7.21–2.58), which confirms the hypothesis of the dominant role of its compounds in the formation of the ferrum concretions forms.</p>