Plant Water Demand Research Articles

Low sensitivity of three terrestrial biosphere models to soil texture over the South American tropics

Abstract. Drought stress is an increasing threat for vegetation in tropical regions, within the context of human-induced increase of drought frequency and severity observed over South American forests. Drought stress is induced when a plant's water demand is not met with its water supply through root water uptake. The latter depends on root and soil properties, including soil texture (i.e. the soil clay and sand fractions) that determines the soil water availability and its hydraulic properties. Hence, soil clay content is responsible for a significant fraction of the spatial variability in forest structure and productivity. Soil-textural properties largely vary at the spatial resolution used by Terrestrial Biosphere Models (TBMs) and it is currently unclear how this variability affects the outputs of these models used to predict the response of vegetation ecosystems to future climate change scenarios. In this study, we assessed the sensitivity of the carbon cycle of three state-of-the-art TBMs, i.e. ORganizing Carbon and Hydrology in Dynamic EcosystEms (ORCHIDEEv2.2), Ecosystem Demography model version 2 (ED2), and Lund–Potsdam–Jena General Ecosystem Simulator (LPJ-GUESS) to soil-textural properties at the regional level over the South American tropics using model default pedotransfer functions. For all three TBMs, the model outputs, including gross primary productivity (GPP), aboveground biomass (AGB), soil carbon content and drought stress, were shown to be mostly insensitive to soil-texture changes representative of the spatial variability in soil properties, except for a small region characterised by very low water availability in ORCHIDEEv2.2 and ED2. We argue that generic pedotransfer and simple drought stress functions, as currently implemented in TBMs, should be reconsidered to better capture the role of soil texture and its coupling to plant processes. Similarly, we suggest that better estimates of the soil-texture uncertainty resulting from soil-texture data aggregate should be considered in the future. Those steps forward are critical to properly account for future increasing drought stress conditions in tropical regions.

An integrated framework to assess climate change impacts on water use for thermoelectric power plants

Climate variability and change impact both water demand and water availability for power generation because of the interconnected relationship between water and thermoelectric power generation. To assess the impacts of climate change on water demand by thermoelectric power plants, this study developed a framework that integrates the characteristics of power plants and the results of the Integrated Environmental Control Model (IECM) and the General Circulation Model (GCM) to simulate the water demand. This study contributed a novel tool to assess climate change impacts on water demand based on local climate conditions. This framework was applied to thermoelectric power plants in Illinois to explore the water demand at daily, monthly, and annual temporal resolutions. The results demonstrated that water use is more sensitive at shorter timescales. Thus, it is important to examine the water-energy nexus at a finer temporal resolution. Results also indicated that water consumption is more sensitive to climate change than withdrawal; power plants with a wet cooling tower are more sensitive than ones with a once-through cooling system; and natural gas-fired power plants are more sensitive than coal-fired plants. The case study demonstrated the novel framework is capable to assess climate change impact on water demand of thermoelectric power plants at varying temporal resolutions and the framework is easily applicable to other parts of the world.

Perencanaan Kebutuhan Air Pada Areal Irigasi Bendung Walahar Karawang, Jawa Barat


 Planning for water needs for irrigation areas is carried out to determine the water needs for plants to grow and develop. The source of water obtained for meeting water needs comes from the Walahar Dam. The results of water demand planning can also be used to simulate cropping patterns. Cropping patterns are very helpful for farmers in determining effective and efficient planting times. Calculation of plant water needs is processed from climatological data and rainfall data, the results of which are demand discharge. Based on the results of the calculation of water requirements for plants, the average discharge requirement is 0.65 m3/second – 9.59 m3/second, while the available water or available discharge in Walahar Weir is 183.90 m3/second. So it can be concluded that the available water in Walahar Weir can meet the water needs of plants.
 Keywords: Discharge, Climatological Data, Rainfall Data, Plant Water Demand Planning

Impacts of deficit irrigation and organic amendments on soil microbial populations and yield of processing tomatoes

Altered precipitation patterns and increased water demands from urban, industrial, and environmental needs often reduce the volume of irrigation water available for agriculture. Strategies that reduce irrigation water inputs, e.g., deficit irrigation (DI), need further evaluation to determine potential impacts on yield and soil microbial communities driving critical soil biogeochemical cycles. Whether soil organic amendments can stabilize DI effects on yield and microbial communities remains unknown. Processing tomato beds were established in a full factorial experimental design of soils unamended or amended with a one-time application—four to five years before sampling—of either biochar or biochar with compost and three irrigation regimes: full (100 % of plant water demand), or DI treatments at 75 % or 50 % of full irrigation. We profiled soil bacterial and archaeal community compositions for two growing seasons and determined soil C and N metabolic potentials and biomass of microbial groups using high throughput sequencing of 16S rRNA genes and phospholipid fatty acid analysis. We tested the discrete and interactive effects of DI and soil amendments on soil chemical and biological properties, and crop yield. DI had stronger effects on the bacterial and archaeal community composition than soil organic amendments. However, 75 % DI did not strongly affect bacterial and archaeal community composition or the total and individual biomass of microbial groups, but it increased irrigation water productivity of processing tomatoes. Although soil amendments did not stabilize the compositional shifts induced by DI, their recalcitrant C still had residual effects on the bacterial and archaeal community composition years after their incorporation. Furthermore, soil moisture correlated with bacterial and archaeal community's C and N metabolic potentials, likely augmenting the amendments' C and N residence time in DI soils. Our results provide insight into water-saving mechanisms that could increase profit margins in water-scarce years without affecting microbial populations that support plant growth and productivity.

Smart advanced agriculture system in India using IoT technology

The current work focuses on the need for automation in agriculture through IoT technology. Automated farming aims to monitor and control various parameters that can help increase agriculture productivity. The proposed system provides a technical solution to a variety of problems such as water demand, humidity, temperature and humidity of complex plants, fire warning and maintenance check on unwanted agricultural inputs including timely and adequate electricity supply. In the proposed system a Wi-Fi module is used that automatically notifies the alert and unwanted stay or sign-in display of real-time data that can be seen and accessed online using IoT technology from anywhere in the world. The system is equipped with a solar panel that provides conditions for different environmental forces and the performance of various sensors is available to meet your desired expectations.

Direct and Legacy Effects of Spring Temperature Anomalies on Seasonal Productivity in Northern Ecosystems

Warmer or cooler spring in northern high latitudes will, for the most part, directly impact gross primary productivity (GPP) of ecosystems, but also carry consequences for the upcoming seasonal GPP. Spatiotemporal patterns of these legacy effects are still largely unknown but important for improving our understanding of how plant phenology is associated with vegetation dynamics. In this study, impacts of spring temperature anomalies on spring, summer and autumn GPP were investigated, and the dominant drivers of summer and autumn GPP including air temperature, vapor pressure deficit and soil moisture have been explored for northern ecosystems (>30°N). Three remote sensing products of seasonal GPP (GOSIF-GPP, NIRv-GPP and FluxSat-GPP) over 2001–2018, all based on a spatial resolution of 0.05°, were employed. Our results indicate that legacy effects from spring temperature are most pronounced in summer, where they have stimulating effects on the Arctic ecosystem productivity. Spring warming likely lessens the harsh climatic constraints that govern the Arctic tundra and extends the growing season length. Further south, legacy effects are mainly negative. This strengthens the hypothesis that enhanced vegetation growth in spring will increase plant water demand and stress in summer and autumn. Soil moisture is the dominant control of summer GPP in temperate regions. However, the dominant meteorological variables controlling vegetation growth may differ depending on the GPP products, highlighting the need to address uncertainties among different methods of estimating GPP.

Evaluation Of Water Delivery Performance In The Paya Sordang Irrigation Area, Padang Sidimpuan Tenggara District, Tapanui Regency

Irrigation plays a role in increasing crop production, by regulating, providing water needs for plants. Water demand for plants is affected by water loss due to decreased performance of irrigation networks. For this reason, a good irrigation system is needed so that water needs for plants can be met. Loss of water that occurs in irrigation canals can affect the efficiency of water requirements needed by plants. To increase crop production, it can also be done by optimizing the available land so that land use becomes more effective. The location of the research study is in the Paya Sordang Irrigation Area, Southeast Padangsidimpuan District, South Tapanuli Regency. Analysis of irrigation water needs was carried out using the FJMock method, from the analysis of irrigation water needs it was found that the mainstay discharge of the Batang Angkola watershed was obtained in order to obtain a good planting pattern and period. From the measurement of the discharge can be seen the efficiency of the irrigation canal. Meanwhile, to calculate land effectiveness, it is done by dividing the irrigated area by the design area. Based on this research, the mainstay discharge is 17.75 m3/s and the water demand is 0.7 lt/sec/ha. The efficiency of the secondary network is 91.1962%, this efficiency has met the efficiency specified in the criteria for irrigation planning, namely for the secondary channel, the efficiency is 90%. From the research results, it can be seen that Paya Sordang irrigation is currently less effective. This can be seen from the initial planned irrigation area which is 4,350 ha and which can be irrigated only 1,232 ha during the dry season and 3,118 during the rainy season, so that the effectiveness of Paya Sordang irrigation is only 28.322% during the dry season and 71.678% during the rainy season.

How temperature shocks impact energy poverty in Vietnam: mediating role of financial development and environmental consideration.

This paper evaluates the energy poverty of Vietnam by mediating the role of financial development and environmental considerations. Across the globe, billions of individuals live in fuel poverty, failing to access inexpensive and sustainable energy, which is necessary for long-term development. An elevation in power consumption due to an overall increase in heat and short periods of extreme heat exacerbates global warming. The goal of this research is to look at how climate change is affecting energy poverty in Vietnam. This finding (1) demonstrates that temperature shocks have a positive and quantitative impact. (2) The same may be said for "poor income/high cost" figures, which include information on power rates. Similarly, if households use the same amount of power but spend less on other items, the influence will not raise their electricity use. (3) Thermal shocks have been shown to reduce agricultural output in studies. During seasons of low rainfall, for example, higher evaporation and plant water demand can worsen drought and raise total irrigation expenses. Labor productivity is also affected by rising temperatures, particularly in weather-sensitive industries like agriculture. As a result, heat shocks will lower agricultural revenues, worsening energy poverty. Surprisingly, overall income appears to be a little mitigating influence. This might be owing to widespread underreporting of stated income, particularly among persons who rely on agriculture for their livelihood.

BIOMASSA DE DOIS CLONES DE Eucalyptus (E. grandis × E. urophylla) IRRIGADOS COM ÁGUA SALINA

ABSTRACT Using saline water for irrigation relies on strategies that include selecting salt-tolerant cultivars and leaching salts away from zones close to the roots. A greenhouse experiment was carried out to assess early growth and biomass production of two Eucalyptus clones (E. grandis × E. urophylla), CO 865 and CO 1407, irrigated with saline water and under different leaching fractions. Treatments were laid out in a randomized block design and arranged in a 4 × 2 + 2 factorial scheme: four leaching fractions (3, 10, 20, and 30 % of crop water demand for plants irrigated with saline water), two Eucalyptus clones (VCC 865 and CO 1407), and two additional treatments, one for each clone, conventionally irrigated with fresh water. The treatments were replicated four times. Measurements were made at 114 days after transplanting. Soil salinity decreased with increasing leaching fraction where VCC 865 was grown; however, leaf dry weight production was lower in treatments irrigated with saline water. Compared to fresh water-irrigated plants, irrigation with saline water resulted in lower: canopy diameter, leaf number, dry leaf mass, dry root mass, aerial parts dry mass, aerial part/root ratio, and total plant dry weight. Overall, the VCC 865 Eucalyptus clone performed better under saline irrigation than CO 1407.

Leaf coordination between petiole vascular development and water demand in response to elevated CO2 in tomato plants.

The rise in atmospheric CO2 has a profound impact on plants physiology and performance. Stomatal gas exchange such as reduction in water loss via transpiration and higher photosynthetic rates are among the key plant physiological traits altered by the increase of CO2. Water acquired in plant roots is transported via the xylem vessels to the shoots. Under conditions of elevated CO2, water flux decreases due to higher water use efficiency and a decline in stomatal conductance. However, the mechanism by which the shoot vascular development is affected under elevated CO2 is still largely unclear in herbaceous crops. In the current study, tomato plants were exposed to either 400 or 800 ppm of CO2 and were analyzed for growth, leaf area, gas exchange rate, and petiole anatomy. Elevated CO2 caused a reduction in metaxylem vessel diameter, which in turn, decreased leaf theatrical conductivity by 400% as compared with plants grown under ambient CO2. This work links anatomical changes in the petioles to the rise in atmospheric CO2 and water use. Plant water demand declined under elevated CO2, while photosynthesis increased. Thus, the decrease in leaf specific conductivity was attributed to lower water consumption in leaf gas exchange and, by extension, to higher leaf water use efficiency. As the global climate changes and water scarcity becomes more common, such anatomical alterations caused by elevated CO2 may affect plant response to water limitation. Further research on petiole anatomical alterations under conditions of combined climate change factors such as drought and heat with elevated CO2 may assist in clarifying the responses expected by future climate scenarios.

Factors dominating the horizontal and vertical variability of soil water vary with climate and plant type in loess deposits

Identifying the variability and predominant factors affecting soil water (SW) is essential in regions with thick vadose zones and deep-rooted plants. This information is needed to clarify the balance between water availability and plant water demand. We collected 9263 soil samples from 128 profiles of 7–25 m deep soil under different climates (arid, semiarid and subhumid), soil textures and plant types (shallow or deep roots) in China's Loess Plateau. The factors dominating the horizontal and vertical variability of SW were identified using a multimodel inference approach and stepwise regression analysis. Horizontally, the mean water content and storage increased while the water deficits decreased from the northwest to the southeast. Vertically, mean water content and storage are highest in the relatively stable layer, followed by rapidly changing layers and active layers. Plant age and soil clay content dominate the horizontally varied SW, while plant age and normalized difference vegetation index (NDVI) dominate the vertical variability of SW. However, the dominant factors appeared to differ with climate and plant type. It was determined that for climate, soil clay content and plant age in arid regions, precipitation and plant age in semiarid regions, NDVI and plant age in subhumid regions were important factors. For plants, the dominant factors are NDVI and precipitation under shallow-rooted plants; however, NDVI and plant age were dominant under deep-rooted plants. The dominance of plant age highlighted the impact of vegetation patterns on SW, especially for deep-rooted plants, which should be taken into account when managing water resources and ecosystem rehabilitation in degraded regions.

THE APPLICATION OF DRY RUBBER LATEX AND VERMICOMPOST TO PLANT WATER CONSUMPTION AND THE GROWTH OF PADDY ON SWAMPY LAND

Swampy land is an alternative for rice plant cultivation where the amount of rainfall has an impact on the amount of inundation. In order to provide appropriate water for rice plants, especially during the dry season, an irrigation water system is required for its control.Alternative materials such as dry rubber latex and vermicom-post can be utilized to reduce water use and ensure that water is delivered as efficiently as possible. The goal of this study was to see how dried rubber latex on the soil surface and vermicompost in the soil affected rice plant water demand and growth. This research was conducted from November 2020 – February 2021. The study used a factorial randomized block design (RAKF) with 2 treatments, covered dry rubber latex variations (K), K0 (0%), K1 (25%), K2 (50%), K3 (75%), and vermicompos (V), V0(0 g), V1(58.82 g), V2(117.64 g), V3 (176.46 g)with 3 rep-licat. So that the total treatmentsare 48 treatments.The results showed that the application of dry rubber latex and vermicompost significantly affected the number of leaves and the number of tillers. The K3 treatment (75%) was the best because it had the smallest evapotranspiration rate with an average of 1.2 mm day-1. The K3 treatment (75%) had the smallest average water requirement of 1.6 mm day-1 with an average number of 37.07 leaves. The high yield of K3 treatment was due to the wider the area covered by 75% (K3), the higher the water content, nutrients, and the lower the soil temperature. Closure using dry rubber latex can reduce sunlight so that the process of water loss is lower, and the available nutrients are higher.

Image processing algorithm to estimate ice-plant leaf area from RGB images under different light conditions

The productivity of horticultural crops in an artificial light condition are highly influenced by the structure of plant and the area coverage. Accurate measurement of leaf area is very important for predicting plant water demand and optimal growth. In this paper, we proposed an image processing algorithm to estimate the ice-plant leaf area from the RGB images under the artificial light condition. The images were taken using a digital camera and the RGB images were transformed to grayscale images. A binary masking was applied from a grayscale image by classifying each pixel, belonging to the region of interest from the background. Then the masked images were segmented and the leaf region was filled using region filling technique. Finally, the leaf area was calculated from the number of pixel and using known object area. The experiment was carried out in three different light conditions with same plant variety (Ice-plant, Mesembryanthemum crystallinum). The results showed that the correlation between the actual and measured leaf area was found over 0.97 (R2:0.973) by our proposed method. Different light condition also showed significant impact on plant growth. Our results inspired further research and development of algorithms for the specific applications.

Assessment of crop water requirement of field pea (Pisum sativum L.) in foothills valley areas of Manipur, North East India

The purpose of this study was to assess the evapotranspiration in field pea (Pisum sativum L.) in foothills valley areas of Manipur using the Hargreaves-Samani equation to predict the plant water demand. The crop coefficient (Kc) values ranged between 0.45 and 1.28 during the crop growth stages of field pea for the five crop seasons (2013-18). The average five-year effective rainfall was estimated to be 59.0 mm, with standard deviation (SD±) ranging between 4.4 to 35.1 mm. The average crop water requirement for field pea was estimated to be 221.0 mm and the average water demand for different crop growth stages of field pea was estimated to be 20.0 mm (initial stage), 52.0 mm (development stage), 100.0 mm (mid-season) and 49.0 mm (late season). Thus, the information generated may help in effective management of crop water requirements for sustainable crop production including field pea in the region.

Responses of 'Syrah' grapevine to deficit irrigation in the Brazilian semi-arid region

Grapevine growing in areas with low rainfall as the Brazilian semi-arid requires irrigation to full fill plant water demand. The objective of this study was to evaluate the physiological and yield responses of grapevine to irrigation strategies in the Lower Middle São Francisco Valley, in Petrolina, State of Pernambuco, Brazil. The experiment was carried out over three consecutive growing seasons of drip irrigated 'Syrah' grapevine, grafted on 1103 Paulsen and planted in an Ultisol (Soil Taxonomy, USA). Full irrigation (FI), regulated deficit irrigation (RDI), and deficit irrigation (DI) treatments were designed in a randomized block with four replications. Mostly soil moisture depletion was observed until 0.6 m soil depth while higher moisture values and their small variation over the time were observed below 0.6 m and until 1.20 m depth as consequence of dense soil layers. RDI and DI promoted moderate water stress in plants (pre-dawn water potential from −0.2 to 0.4 MPa), reducing water consumption and gas exchange. Intrinsic water use efficiency was higher in RDI and DI (121 and 115 µmol CO2 mol H20−1, respectively). Tritratable acidity reduced to 5.81 and 6.28 g L−1 tartaric acid as water deficit increased, except in the third season. Soluble solids were influenced by treatments only in the second season, when it decreased in FI plants (22.6° brix). Weight of 100 berries was influenced by treatments in all seasons, with lower values for DI and RDI grapevines (less than 155 g). Number (15) and weight (2.2 kg) of cluster per grapevine and yield (7284 kg) were significantly higher in FI only in the third growing season, while average cluster weight was greater in FI in the first and third seasons (84 and 149 g, respectively). Irrigation water productivity did not differ among irrigation strategies. Deficit irrigation strategies allowed water saving.

Assessment of regional water demand for coal-based power plants in India: exploring its regional impact on other cross-sectoral water stress.

Water use in coal power generation is one of the key points to highlight for the countries like India because country electricity demand increases rapidly which led to increase in water demand. The coal power sector in India will remain to be the dominant source of electricity generation until 2040 and will require a regular water supply, which is already in a stressful condition. This work focuses on the regional assessment of water withdrawal and consumption of the coal power sector at three broad stages includes fuel extraction, fuel preparation, and power generation. Our analysis reveals that 99% of the total water supply to the sector was withdrawn by power plants. Further, the study assessed its trade-off with other sectoral water demand adopting WSI (Water Stress Index) criteria for both surface and groundwater sources. The results highlighted the per capita groundwater to be under severe stress and similar status was also identified in the case of fresh surface water except for the Central region. The overall WSI status was found to be severe in all regions of India. This situation creates a water-scarce situation for water-guzzling power plants that are dependent on surface water and faces the competitive situation with the agriculture and domestic sector. Results of the study concluded that the technological up-gradation at the power plants could be helpful to reduce the total water demand by 78% of coal power sector which can be reduced the severity of regional water stress. Our study aids policymakers to identify the region which is more vulnerable in terms of cross-sectoral water demand and also fulfills the need for quality data availability at a regional scale that may use in the future towards sustainable water-resources management practices.

Irrigation Scheduling with Soil Gas Diffusivity as a Decision Tool to Mitigate N2O Emissions from a Urine-Affected Pasture

Pastures require year-round access to water and in some locations rely on irrigation during dry periods. Currently, there is a dearth of knowledge about the potential for using irrigation to mitigate N2O emissions. This study aimed to mitigate N2O losses from intensely managed pastures by adjusting irrigation frequency using soil gas diffusivity (Dp/Do) thresholds. Two irrigation regimes were compared; a standard irrigation treatment based on farmer practice (15 mm applied every 3 days) versus an optimised irrigation treatment where irrigation was applied when soil Dp/Do was ≈0.033 (equivalent to 50% of plant available water). Cow urine was applied at a rate of 700 kg N ha−1 to simulate a ruminant urine deposition event. In addition to N2O fluxes, soil moisture content was monitored hourly, Dp/Do was modelled, and pasture dry matter production was measured. Standard irrigation practices resulted in higher (p = 0.09) cumulative N2O emissions than the optimised irrigation treatment. Pasture growth rates under treatments did not differ. Denitrification during re-wetting events (irrigation and rain) contributed to soil N2O emissions. These results warrant further modelling of irrigation management as a mitigation option for N2O emissions from pasture soils, based on Dp/Do thresholds, rainfall, plant water demands and evapotranspiration.

Root hydraulics adjustment is governed by a dominant cell-to-cell pathway in Beta vulgaris seedlings exposed to salt stress

Soil salinity reduces root hydraulic conductivity (Lpr) of several plant species. However, how cellular signaling and root hydraulic properties are linked in plants that can cope with water restriction remains unclear. In this work, we exposed the halotolerant species red beet (Beta vulgaris) to increasing concentrations of NaCl to determine the components that might be critical to sustaining the capacity to adjust root hydraulics. Our strategy was to use both hydraulic and cellular approaches in hydroponically grown seedlings during the first osmotic phase of salt stress. Interestingly, Lpr presented a bimodal profile response apart from the magnitude of the imposed salt stress. As well as Lpr, the PIP2-aquaporin profile follows an unphosphorylated/phosphorylated pattern when increasing NaCl concentration while PIP1 aquaporins remain constant. Lpr also shows high sensitivity to cycloheximide. In low NaCl concentrations, Lpr was high and 70 % of its capacity could be attributed to the CHX-inhibited cell-to-cell pathway. More interestingly, roots can maintain a constant spontaneous exudated flow that is independent of the applied NaCl concentration. In conclusion, Beta vulgaris root hydraulic adjustment completely lies in a dominant cell-to-cell pathway that contributes to satisfying plant water demands.

Combined effects of biomaterial amendments and rainwater harvesting on soil moisture, structure and apple roots in a rainfed apple orchard on the Loess Plateau, China

Adequate soil moisture and good soil structure are critical to sustainable productivity of rain-fed apple (Malus pumila Mill) orchards on China’s Loess Plateau. Droughts, poor soil structure, low soil fertility, and a lack of synchronization between plant water demand and rainfall results in low rainfall use efficiency in gentle slope orchards of this area. This study combined soil biomaterial amendment and rainwater harvesting (BARH), and evaluated the effect of BARH on soil moisture content (SMC), soil water storage (SWS), soil saturated hydraulic conductivity, soil structure, and apple roots in a field experiment in rainfed apple orchard on the Loess Plateau from 2016 to 2018. Three treatments: (1) the BARH treatment, combination of biomaterial amendment and rainwater harvesting (2) the RH treatment, rainwater harvesting measure only and (3) the control (CK) treatment, which is the local traditional practice. Compared with the CK treatment, the BARH and RH treatment significantly (P < 0.05) improved SMC by 31.08% and 18.83%, respectively, and SWS by 102.19 mm and 35.30 mm, respectively, within 0–300 cm during the apple growing season (from April to October) over three years. There were notable and significant increases in SMC in the 0–160 cm soil layer. SWC in the autumn improved due to heavy rainfall and lower water consumption by the apple trees. This alleviated the critical water requirements of early spring apple trees for the following year, and therefore, less rainfall was required. The BARH treatment had a soil bulk density (BD) that was 3.52% lower (P < 0.05) within 0–60 cm soil depth, 83.93% higher saturated soil conductivity (Ksat), and 4.9% higher sand-size soil macroaggregates (0.02–2 mm) within 0–40 cm soil depth, compared to the CK treatment over three years. 70% of the root systems were concentrated in the 0–160 cm soil layer in all treatments which was highly correlated with SMC. Root dry weight density (RWD) under BARH and RH treatments increased by 33.35% and 7.52% within 0–300 cm of the soil in comparison to the CK treatment, respectively. Likewise, the root length density (RLD) under BARH and RH treatments increased by 52.16% and 21.34% within the 0–300 cm soil layer compared to the CK treatment, respectively. Therefore, the combination of biomaterial amendment and rainwater harvesting is an effective cultivation measure for sustainable development of rainfed apple orchards on the Loess Plateau.

土地利用/覆被变化扎龙湿地蒸散发量及生态需水量的遥感估算

地表蒸散发量是影响湿地水热平衡的主要因素，也是水分损失的主要途径，对湿地生态需水量的合理确定和水资源的有效管理具有重要意义。借助遥感和GIS技术，利用2002、2010、2016年34景Landsat影像，基于时序NDVI数据对湿地下垫面物候特征的定量表征，准确获取了扎龙湿地保护区3个时期土地利用/覆被的动态变化信息。选用物理基础较好且应用广泛的SEBAL模型，估算了湿地的瞬时蒸散发量，并结合站点气象数据，实现了湿地蒸散发量在时间尺度上的扩展，分别得到日、月、年尺度的湿地蒸散发量，深入探究了扎龙湿地蒸散发的时空分布特征；最后从湿地湖泡需水量、植物需水量及生物栖息地需水量3个方面，定量估算出扎龙湿地3个时期的现状生态需水量。研究发现：扎龙湿地的土地覆被类型主要以芦苇沼泽、草地和耕地为主，其中芦苇沼泽分布占绝对优势，且2002-2016年持续增加了205.82 km²；草地、耕地呈持续减少态势，分别减少了119.35 km²和95.96km²，表明2002-2016年扎龙湿地生态系统呈恢复态势；湿地保护区蒸散发量年内均大致呈单峰型分布，符合夏季 > 春季 > 秋季 > 冬季的规律，在年际上呈现明显的递增趋势，年蒸散发量由2002年的518.87mm增加到2016年的625.98mm，增加了20.64%。为满足湿地内的生态消耗，总体上2002-2016年湿地的生态需水量也相应的增加，保护区适宜生态需水量的变动范围为5.40亿-7.08亿m³，可以维持湿地湖泊、植被、动植物栖息地的健康态势。维持核心区健康状态的最小生态需水量变化范围为2.71亿-3.32亿m³。随着遥感数据时空分辨率的提高，基于蒸散发量反演的湿地生态需水量估算将更加实用和准确，为湿地保护区制定科学合理的补水方案提供有效的技术支撑。;Surface evapotranspiration is a main factor influencing wetland water-heat balance and a main way of water loss. It has important significance for the reasonable determination of ecological water demand in wetlands and the effective management of water resources. With the help of remote sensing and GIS technology, the quantitative characterization of the phenological characteristics of the underlying surface of Zhalong wetland based on temporal NDVI data was made by using Landsat images of 34 scenes in 2002, 2010 and 2016. At the same time, the dynamic change information of land use/cover in three periods of the wetland reserve was obtained accurately. The SEBAL model with good physical foundation and wide application was selected to estimate the instantaneous evapotranspiration of the wetland. By combining with the meteorological data of nearby hydrographic stations, the temporal expansion of evapotranspiration of the wetland was realized. The daily, monthly and annual evapotranspiration of Zhalong wetland was obtained, and the spatio-temporal distribution characteristics of evapotranspiration in Zhalong wetland were deeply investigated. At last, the present ecological water demand of Zhalong wetland in three periods was quantitatively estimated from three aspects:water demand of wetland lake bubble, water demand of plants, and water demand of biological habitat. The results indicated that the land cover types of Zhalong wetland were mainly reed marshes, grasslands and cultivated land, among which reed marshes occupied the absolute dominance, increased by 205.82 km² continuously from 2002 to 2016. Grassland and cultivated land decreased by 119.35 km² and 95.96 km², respectively, indicating that Zhalong wetland ecosystem showed a recovery trend from 2002 to 2016. The annual evapotranspiration of the wetland reserve presented a roughly single-peak distribution in the three years, which was consistent with the summer > spring > autumn > winter. The annual evapotranspiration increased significantly from 518.87 mm in 2002 to 625.98 mm in 2016, by an increase of 20.64%. In order to meet the ecological consumption in the wetland, the total ecological water demand of the wetland increased correspondingly from 2002 to 2016. The range of the appropriate ecological water demand of the wetland reserve was 540 million m³ -708 million m³, which could maintain the health of the lakes, vegetation, animal and plant habitats in the wetland. The minimum ecological water demand for maintaining the health of the core area varied from 271 million m³ to 332 million m³. With the improvement of spatial and temporal resolution of remote sensing data, the estimation of wetland ecological water demand based on evapotranspiration inversion will be more practical and accurate, providing effectively technical support for the formulation of scientific and reasonable water rehydration schemes in wetland reserves.