Areas In Arid Regions Research Articles

Differences in the Effects of Three Water Elements on Vegetation in Different Climatic Regions: Insights From the Yellow River Basin, China

ABSTRACTThe effects of water on vegetation have always been a concern. It is an important support as well as a major limiting factor with respect to vegetation growth. By analysing the spatiotemporal changes and correlations between precipitation (PRE), soil moisture (SM), vapour pressure deficit (VPD) and normalized difference vegetation index (NDVI) in the Yellow River Basin, we explored the different effects of three water elements on vegetation in different climatic regions. Our findings reveal the following: (1) NDVI and the three water elements report an increasing trend in the Yellow River Basin, with NDVI increasing most significantly. 92.1% of the Yellow River Basin showed an increase in NDVI. (2) Vegetation in the Yellow River Basin was most positively affected by PRE, followed by SM and VPD. PRE mainly affected the natural vegetation on both sides of the boundary between the arid and semi‐arid regions and the semi‐humid regions. SM mainly affected the natural vegetation in the arid and semi‐arid regions, whereas VPD mainly affected the crops in the irrigation areas, and the irrigation areas in arid regions were affected the most. These findings contribute to a deeper understanding of the relationship between water elements and vegetation.

Carbon sequestration through conservation tillage in sandy soils of arid and semi-arid climates: A meta-analysis

This meta-analysis assessed soil organic carbon (SOC) percent changes in sandy soils, transitioning from conventional tillage (CT) to conservational tillage (CST) in arid and semi-arid climates. High levels of SOC in sandy soils are difficult to attain especially when precipitation levels are very low, contributing to low biomass production, and increased decomposition of organic matter. While CT practices are known to reduce SOC through the breakdown of soil aggregates, accelerated decomposition of soil organic matter, and promote erosion, CST methods (i.e., mulch tillage, no tillage, reduced tillage, ridge tillage, etc.) offer the potential to preserve soil aggregates and increase SOC concentration. Analyzing 55 peer-reviewed publications in arid and semi-arid climates with ≥ 45 % sand content, this study compared SOC content between CST and CT over short- and long-term periods (349 paired observations). Results showed that CST increased SOC in sandy soils, with an estimated 12.74 ± 1.46 % increase. Specifically, reduced tillage (RdT), mulch tillage (MchT), and no tillage (NT) exhibited the highest increases of SOC by 18.94 ± 2.48 %, 11.45 ± 2.46 %, and 10.06 ± 2.46 %, respectively, compared to CT. Studies with durations of up to 15 years (n = 297) showed a progressive increase in SOC concentrations under CST; however, the long-term stability of the accrued carbon content in sandy soils of arid and semi-arid climates is still uncertain, as studies extending beyond 15 years (n = 52) did not demonstrate significant changes in SOC levels. CST significantly raised SOC concentrations in precipitation up to 600 mm, though no significant changes were observed for precipitation over 600 mm. In soils with over 56 % sand content, CST increased SOC by approximately 13 %. This study highlights both positive and limited impacts of CST practices for soil conservation and climate change mitigation, emphasizing their significance for both existing agricultural areas in arid regions and those in parts of the world where aridity is on the rise.

Optimal groundwater depth and irrigation amount can mitigate secondary salinization in water-saving irrigated areas in arid regions

Secondary salinization poses a significant threat to the sustainable development of water-saving irrigation districts. This study aims to explore the spatial and temporal variations in soil salinity and the factors influencing these changes in water-saving irrigation areas in the inland arid regions of Northwest China. The Manas River Irrigation District was selected as the study area. A grid measuring 10 km × 14 km grid was designed to determine the latitude and longitude coordinates of the grid centers, resulting in 66 sample points. Soil samples were collected from these points in 2013, 2014, 2020, and 2021 from the 0100 cm layer to obtain salinity data. Based on existing research and practical conditions in water-saving irrigation areas, 11 factors influencing soil salinity changes were identified, including irrigation area and irrigation amount. Classical statistical methods and interpretable machine learning techniques were employed to analyze the distribution characteristics of soil salinity and the influencing factors. This analysis proposes effective solutions to mitigate potential secondary salinization in irrigation areas. The results revealed that soil salinity in the irrigation area belonged to moderate variation (Cv = 46.74 %51.80 %). The horizontal direction of the irrigation area shows higher salt content in the upstream and downstream areas, and a gradual decrease in variability with increasing depth characterizes the vertical direction. From 2013–2021, soil salinization in the irrigation area gradually decreased. In 2013 and 2014, the area was predominantly covered by mild saline-alkali soil, accounting for 75.1 % and 76.6 % of the total area, respectively. However, in 2020 and 2021, non-saline soils became dominant, covering 60.9 % and 66.5 % of the total irrigation area, respectively. In order of importance, the factors affecting the spatial and temporal evolution of soil salinity are groundwater depth, annual water surface evaporation, water-saving irrigation area, underground water diversion amount, mineralization of groundwater, irrigation amount, surface water diversion amount, and annual rainfall. In the oasis irrigation area, maintaining a groundwater depth of 4.06.0 m and an irrigation amount of 55006000 m3 ha−1 can alleviate the problem of secondary salinization that may result from large-scale development of water-saving irrigation. The findings of this study provide a basis for the prevention and control of soil salinization in water-saving irrigation areas and the development and management of saline land in oasis areas.

Use of remote sensing, spatial and geophysical modeling, and real recharging capabilities to identify suitable areas for groundwater exploitation in dry coastal areas

Accurate identification of groundwater potential areas in arid regions is an important task for groundwater management and sustainability. As a result, this study used the innovative integration of remote sensing (RS), geographic information system (GIS), watershed modeling system (WMS), geophysical survey, and water mass balance equation to identify potential groundwater areas in the W. Dara, Eastern Desert, Egypt. A weighted spatial probability model (WSPM) of groundwater potential based on eight regulatory factors was implemented within ArcGIS software. Drainage density (DD), precipitation (P), net groundwater recharge (NGR), terrain slope (TS), lineament density (LD), lithologic group (LG), water quality (TDS), and depth to groundwater level (DGW) are the aspects considered. The Analytical hierarchy process (AHP) method was used to assign weights to these parameters, and their accuracy was estimated using the consistency ratio (CR). The resulting groundwater potential map classified W. Dara study area into five categories, ranging from very low to very high potential. A geophysical survey, in the form of Vertical Electrical Sounding (VES) and Transient Electromagnetic (TEM), was conducted along W. Dara to validate the results of the WSPM, which identified areas of high groundwater potential. The 1D inversion of VES/TEM shows that the central and western parts of W. Dara are considered the most promising areas for groundwater occurrence, and are located in areas of high and very high potential classes derived from WSPM. Moreover, the results of VES and TEM surveys showed that the proposed aquifers (Nubian Sandstone, Miocene, and Quaternary) in the study area are horizontally and vertically connected through a set of normal faults traversing NW-SE. Ten sites have been proposed for drilling additional exploitative wells in W. Dara area based on the WSPM and geophysical survey with the aim of sustainable development. Thus, the integrated techniques applied in this study proved effective in accurately determining the development strategy for arid and semi-arid coastal areas, especially those that suffer from scarcity of rainfall and increased agricultural reclamation requirements in remote areas.

Improving the STARFM Fusion Method for Downscaling the SSEBOP Evapotranspiration Product from 1 km to 30 m in an Arid Area in China

Continuous evapotranspiration (ET) data with high spatial resolution are crucial for water resources management in irrigated agricultural areas in arid regions. Many global ET products are available now but with a coarse spatial resolution. Spatial-temporal fusion methods, such as the spatial and temporal adaptive reflectance fusion model (STARFM), can help to downscale coarse spatial resolution ET products. In this paper, the STARFM model is improved by incorporating the temperature vegetation dryness index (TVDI) into the data fusion process, and we propose a spatial and temporal adaptive evapotranspiration downscaling method (STAEDM). The modified method STAEDM was applied to the 1 km SSEBOP ET product to derive a downscaled 30 m ET for irrigated agricultural fields of Northwest China. The STAEDM exhibits a significant improvement compared to the original STARFM method for downscaling SSEBOP ET on Landsat-unavailable dates, with an increase in the squared correlation coefficients (r2) from 0.68 to 0.77 and a decrease in the root mean square error (RMSE) from 10.28 mm/10 d to 8.48 mm/10 d. The ET based on the STAEDM additionally preserves more spatial details than STARFM for heterogeneous agricultural fields and can better capture the ET seasonal dynamics. The STAEDM ET can better capture the temporal variation of 10-day ET during the whole crop growing season than SSEBOP.

Future changes of dry‐wet climate regions and its contributing climatic factors in China based on CMIP6 models

AbstractUnderstanding future dry and wet changes under global climate change is of great regional significance in China. Based on six Global Climate Models (GCM) from the Coupled Model Intercomparison Project phase 6 (CMIP6), we project the changes of dry‐wet climate regions in China in the 21st century under the three SSP‐RCP (shared socioeconomic pathway‐representative concentration pathway) scenarios (SSP1‐2.6, SSP2‐4.5 and SSP5‐8.5), and further identify the key climatic factors that lead to the transition of dry‐wet climate regions. The results show the area of humid and subhumid regions in China will show an upward trend in the future, while the area of semiarid and arid regions will show a downward trend. Especially under the SSP5‐8.5 scenario, the area of the subhumid region has the largest increase trend (0.042% per year), and the area of the arid region has the largest decline trend (−0.048% per year). The three main transfer directions of dry‐wet climate regions are from arid to semiarid regions, from semiarid to subhumid regions, and from subhumid to humid regions in the future. Due to the future extensive wetting trend in the north, the future dry‐wet climate regions will shift to wetter types in Tibet, North China, the Qinling‐Huaihe regions and the northeast. In addition, the key climatic factors for the transition of dry‐wet climate regions are mainly precipitation, maximum temperature and solar radiation. The increase of precipitation plays a dominant role for areas projected to change to wetter types, and the increase of potential evapotranspiration (PET) plays a dominant role for areas projected to change to drier types. The PET changes in changed areas of dry‐wet climate regions are mainly dominated by maximum temperature and solar radiation. Our research has important implications for future water resource management and reconsideration of climate mitigation and adaptation policies.

Water Conservation and Ecological Water Requirement Prediction of Mining Area in Arid Region Based on RS-GIS and InVEST: A Case Study of Bayan Obo Mine in Baotou, China

The overexploitation of mineral resources in northwestern China has resulted in severe ecological degradation and even desertification in certain mining areas. To support ecological restoration in these arid mining regions, we conducted a study on water conservation and ecological water demand using Bayan Obo as a case study. Based on remote sensing, geographic information systems, and the Integrated Valuation of Ecosystem Services and Trade-offs InVEST model, our study found that the mining area has lost its capacity for water production, with the water source conservation showing negative values. In addition, precipitation levels are far lower than evapotranspiration, making it difficult to retain precipitation. We predicted ecological water demand for the planning years (2025, 2030, and 2035) by combining qualitative and quantitative forecasting methods, with 2019 serving as the base year. The results indicated a downward trend in natural ecological water demand, while artificial ecological water demand exhibited the opposite trend. Changes in natural grassland and artificial green areas in the mining region were identified as the main drivers of changes in ecological water demand.

Insecta Orthoptera: a bibliometric review of papers from the Scopus database published in English for the period of 1986-2021

Today, climate change, an increase in anthropogenic factors, and changes in the natural environment have an adverse effect on insect diversity due to the changing climes around the world. There has been an increase in the number of pests of agricultural crops over the past few years because of the expansion of the cultivated areas in arid regions, including the number of insects of the Order Orthoptera. The formation of fauna in different regions of the globe needs to be identified in order to improve the methods of combating them, and therefore, it is necessary to identify their formation. A great deal of research on the class of insects has been conducted over the last 35 years, and most of those articles are published in English. However, the research work on Insecta: Orthoptera was carried out in different topics and ways during those 35 years. The scope of this article is to cover all articles that have been published about orthoptera between 1986 and 2021 in the Scopus database. Various categories were analyzed in order to determine the quality of this research, including the year of research, who was responsible for the research, and which of the major research institutes did the research. In the light of the analysis, it is possible to have a certain understanding of the current research problems that are being experienced in this area as a result of the analysis.

Spatiotemporal Distribution of Precipitation over the Mongolian Plateau during 1976–2017

Located in the interior of Eurasia, the Mongolian Plateau (MP) is extremely sensitive to global warming and become a critical area for studying precipitation patterns. Based on the monthly data of 135 meteorological stations during 1976–2017, we analyze the spatiotemporal change in precipitation and discuss its response to atmospheric circulation. The results show that: (1) Precipitation shows increasing trends in spring, autumn, and winter, but a decreasing trend at a rate of 5.3 mm/decade in summer. The annual precipitation also shows an overall slight decreasing trend. (2) The spatial distribution is uneven, the annual precipitation in the northern Great Khingan Mountains is more, but it gradually decreases at the rate of 10–30 mm/decade, showing a trend of “wet gets dry”; while there is less in the southwest Gobi Desert region, but it gradually increases with the rate of 10–20 mm/decade, showing a trend of “dry gets wet”. (3) Over decades, the East Asian summer monsoon (EASM) and westerly circulation show a seesaw change in MP. Affected by the weakening of the EASM, the area of arid regions has gradually expanded. The results also demonstrate that the EASM has a higher impact on the annual precipitation change pattern, particularly in the southeastern MP. The conclusion indicated that the variation in the position and orientation between EASM and the westerly circulation may be an explanation for the spatiotemporal precipitation pattern, providing a new viewpoint to the question of circulation mechanisms behind climate change in MP in recent 40 years.

Comparative study of indoor thermal environment and human thermal comfort in residential buildings among cities, towns, and rural areas in arid regions of China

Most thermal comfort studies classify towns as rural areas and compare them with cities, dismissing the unique thermal characteristics of towns. A comparative study on thermal comfort in cities, rural areas, and towns based on their original definitions is required. This study aims to determine the differences between indoor thermal environment and human thermal comfort in residential buildings in cities, towns, and rural areas. This four-month investigation was conducted in Bayannur City using a survey with 141 participants. The survey responses were combined with environmental measurements, and the data analysis showed that the participants’ clothing insulation was distributed over a wider range for towns (0.3–0.9 clo) and rural areas (0.9–1.5 clo) than for cities (0.3–0.6 clo). The acceptable operative temperature ranges of city, town, and rural area residents were 20.9–28.0, 17.7–23.3, and 15.1–21.6 ℃, respectively. Although the operative temperature of residential buildings in those areas differed by 5–10 °C, all participants expected a warmer indoor thermal environment. City residents who can adapt to varying conditions can restore thermal comfort more easily than town and rural area residents.

Analysis of Spatial Structure in the Kashgar Metropolitan Area, China

Taking metropolitan areas as space carriers has become the engine of the Chinese government in its promotion of high-quality development, and this has also become an important measure by which to balance regional development. We used Zipf’s law and the gravity model to study the urban scale distribution characteristics of the Kashgar Metropolitan Area (KMA) in this paper. We also constructed a spatial structure judgment vector for the KMA and put forward the development objectives of different circles. The findings show the following: (1) large cities have a high primacy of development, while small and medium-sized cities are underdeveloped. At present, the KMA is a concentrated monocentric-pattern metropolitan area, with Kashgar City as its core city. (2) The urban built-up area of Kashgar City is expanding to the east and south, where it has broken through the administrative boundary and become integrated with the urban built-up area of Shule County. The spatial structure characteristics of the KMA have been further clarified. The KMA forms three circles: core, middle, and outer. (3) Tumxuk City, Bachu County, Yecheng County, Shache County, and other counties are far from the core city and cannot be connected with Kashgar, but they are closely related to the surrounding cities, forming the Bachu–Tumxuk Urban Group and the Shache–Zepu–Yecheng Urban Group. This study contributes to the understanding of the characteristics of urban scale distribution and the spatial structure of metropolitan areas in arid regions, as well as providing guidance for the formulation of policies for the development of different circles in the KMA.

Groundwater monitoring for evaluating the pasture carrying capacity and its vulnerability in arid and semi-arid regions: A case study of urban and mining areas in Mongolia

Arid and semi-arid regions cover 41% of the global land area and 2 billion people, 90% of which belong to developing countries, live there. Variation in precipitation due to climate change brings big large influences on ground and underground water resources, and especially it is predicted that arid and semi-arid regions are getting drier. Therefore, it is imperative to clarify impacts to environmental vulnerability caused by the variation of water cycle (VWC) due to climate change and consider options for its adaption. Mongolia is a typical country where environmental vulnerability is getting worse by VWC. Our previous studies revealed that the increase of evapotranspiration and permafrost degradation by global warming deteriorate the pasture carrying capacity (PCC) in semi-arid regions in Mongolia. In this manner, VWC is a key component of PCC, but VWC depends on not only climate change but also human activities. Recent mine development and urbanization, as well as growth of livestock, increase groundwater use, but their influences have not been clarified. To explore the influence of urbanization and mining, we have started groundwater monitoring of urban areas in semi-arid regions (Northern Mongolia) and mining areas in arid regions (Southern Mongolia) since May 2018. After investigating hundreds of wells in those areas, and finally selected 11 wells in urban areas and 7 wells in mining areas for groundwater monitoring. 22 Onset HOBO U20 Water Level Loggers (Forestry Suppliers, Inc.), including 5 Loggers for atmospheric correction, and a Water Flow Rate Sensor (Keyence Inc.) are working for measuring groundwater usage. Meanwhile, with data analyses of groundwater level at 875 wells from 2015 to 2017 measured by the local basin authority, it was found that the groundwater level of mining area had a tendency of decreasing widely comparing with that of non-mining area.

Evaluation of the SMOS and SMAP soil moisture products under different vegetation types against two sparse in situ networks over arid mountainous watersheds, Northwest China

Assessment of the suitability of satellite soil moisture products at large scales is urgently needed for numerous climatic and hydrological researches, particularly in arid mountainous watersheds where soil moisture plays a key role in land-atmosphere exchanges. This study presents evaluation of the SMOS (L2) and SMAP (L2_P_E and L2_P) products against ground-based observations from the Upstream of the Heihe River Watershed in situ Soil Moisture Network (UHRWSMN) and the Ecological and Hydrological Wireless Sensor Network (EHWSN) over arid high mountainous watersheds, Northwest China. Results show that all the three products are reliable in catching the temporal trend of the in situ observations at both point and watershed scales in the study area. Due to the uncertainty in brightness temperature and the underestimation of effective temperature, the SMOS L2 product and both the SMAP L2 products show “dry bias” in the high, cold mountainous area. Because of the more accurate brightness temperature observations viewing at a constant angle and more suitable estimations of single scattering albedo and optical depth, both the SMAP L2 products performed significantly better than the SMOS product. Moreover, comparing with station density of in situ network, station representation is much more important in the evaluation of the satellite soil moisture products. Based on our analysis, we propose the following suggestions for improvement of the SMOS and SMAP product suitability in the mountainous areas: further optimization of effective temperature; revision of the retrieval algorithm of the SMOS mission to reduce the topographic impacts; and, careful selection of in situ observation stations for better representation of in situ network in future evaluations. All these improvements would lead to better applicability of the SMOS and SMAP products for soil moisture estimation to the high elevation and topographically complex mountainous areas in arid regions.

Spatial decision support system for land use management of newly reclaimed areas in arid regions

The current work is an attempt to establish a spatial decision support system (SDSS) for the newly reclaimed areas, especially saline soils of the arid regions. The proposed system is based on database of ArcGIS environment and includes land capability and suitability models. A base map of the study area, remotely sensed data, soil and water analytical data, meteorological data and socio-economic information formulate the essential database for the SDSS implementation. Based on processing the proposed SDSS, the agricultural and fish farming land uses would be increased from about 48% to 71% of the total area where almost 60% would be devoted to field crop cultivation, 11% can be used as permanent fish farms and 29% could be assigned to residential and industrial purposes or any other recreational uses. The soils capabilities would be improved through good management policy and land reclamation processes.

The restoration feasibility of degraded Carex Tussock in soda-salinization area in arid region

In the arid and semi-arid areas, Carex Tussock had deteriorated and disappeared as a result of water deficit and salinization due to human activities and climate changes. A green house experiment was carried out to testify the restoration feasible of Carex Tussock in salinization area. We used a factorial design with two soil conditions (degraded soil occurred salinization and undisturbed soil), two Carex Tussocks (degraded ones resulted from soda-salinization and well ones) and three water levels (long-term drought, seasonal inundation and long-term inundation). In soda-saline soil, degraded Carex Tussock subjected to long-term drought died finally, and could not be revived even the stress was eliminated. Degraded Carex Tussock subjected to the other two water treatments and well Carex Tussock in all water condition went dormant status until environment was improved. However, in the undisturbed soil, except for degraded Carex Tussock under the long-term drought, others successfully survived to the end of experiments, and the degraded ones could be revived when water condition was improved. In undisturbed soil, height, leaf width, leaf area, chlorophyll content and biomass (fresh biomass and dry biomass) of well ones were better than degraded ones. Above results illustrated that it was not feasible to restore Carex Tussock in the soda-saline soils no matter by water condition improvement or well Carex Tussock transplanted. However, transplanting degraded or well Carex Tussock to undisturbed soil could establish successfully. Besides, natural Carex Tussock protection should be paid more attention to avoid soil salinization or secondary salinization. Once salinization or secondary salinization extensively occurred, the degeneration of Carex Tussock would be irreversible.

Continuous Daily Evapotranspiration Estimation at the Field-Scale over Heterogeneous Agricultural Areas by Fusing ASTER and MODIS Data

Continuous daily evapotranspiration (ET) monitoring at the field-scale is crucial for water resource management in irrigated agricultural areas in arid regions. Here, an integrated framework for daily ET, with the required spatiotemporal resolution, is described. Multi-scale surface energy balance algorithm evaluations and a data fusion algorithm are combined to optimally exploit the spatial and temporal characteristics of image datasets, collected by the advanced space-borne thermal emission reflectance radiometer (ASTER) and the moderate resolution imaging spectroradiometer (MODIS). Through combination with a linear unmixing-based method, the spatial and temporal adaptive reflectance fusion model (STARFM) is modified to generate high-resolution ET estimates for heterogeneous areas. The performance of this methodology was evaluated for irrigated agricultural fields in arid and semiarid areas of Northwest China. Compared with the original STARFM, a significant improvement in daily ET estimation accuracy was obtained by the modified STARFM (overall mean absolute percentage error (MAP): 12.9% vs. 17.2%; root mean square error (RMSE): 0.7 mm d−1 vs. 1.2 mm d−1). The modified STARFM additionally preserved more spatial details than the original STARFM for heterogeneous agricultural fields, and provided field-to-field variability in water use. Improvements were further evident in the continuous daily ET, where the day-to-day dynamics of ET estimates were captured. ET data fusion provides a unique means of monitoring continuous daily crop ET values at the field-scale in agricultural areas, and may have value in supporting operational water management decisions.

Rapid Delineation of Groundwater Enrichment Area in Arid Region of Xinjiang Based on GRSFAI

Based on groundwater remote sensing fuzzy assessment index (GRSFAI), a research on groundwater enrichment in the arid gobi region in the southeast of Yanqi basin in Xinjiang was carried out. In consideration of the sources of groundwater, storage space and runoff conditions, remote sensing interpretation and DEM data analysis methods were adopted to extract 6 factors related to the groundwater enrichment, such as lithology, fault, relief, slope, vegetation coverage, flow accumulation. Each factor which was quantified by fuzzy comprehensive method would be calculated by AHP, and the rapid delineation of groundwater enrichment area was finally realized according to the weighted calculation results. On the basis of the research, two wells have been constructed in the groundwater enrichment area, which has water yield of 3500m3/d and 3800m3/d respectively. The reliability and applicability of the GRSFAI method to evaluate the groundwater enrichment in research area are also validated.

Mapping daily evapotranspiration based on spatiotemporal fusion of ASTER and MODIS images over irrigated agricultural areas in the Heihe River Basin, Northwest China

Continuous monitoring of daily evapotranspiration (ET) is crucial for allocating and managing water resources in irrigated agricultural areas in arid regions. In this study, continuous daily ET at a 90-m spatial resolution was estimated using the Surface Energy Balance System (SEBS) by fusing Moderate Resolution Imaging Spectroradiometer (MODIS) images with high temporal resolution and Advanced Space-borne Thermal Emission Reflectance Radiometer (ASTER) images with high spatial resolution. The spatiotemporal characteristics of these sensors were obtained using the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM). The performance of this approach was validated over a heterogeneous oasis-desert region covered by cropland, residential, woodland, water, Gobi desert, sandy desert, desert steppe, and wetland areas using in situ observations from automatic meteorological systems (AMS) and eddy covariance (EC) systems in the middle reaches of the Heihe River Basin in Northwest China. The error introduced during the data fusion process based on STARFM is within an acceptable range for predicted LST at a 90-m spatial resolution. The surface energy fluxes estimated using SEBS based on predicted remotely sensed data that combined the spatiotemporal characteristics of MODIS and ASTER agree well with the surface energy fluxes observed using EC systems for all land cover types, especially for vegetated area with MAP values range from 9% to 15%, which are less than the uncertainty (18%) of the observed λE in this study area. Time series of daily ET modelled from SEBS were compared to that modelled from PT-JPL (one of Satellite-based Priestley-Taylor ET model) and observations from EC systems. SEBS performed generally better than PT-JPL for vegetated area, especially irrigated cropland with bias, RMSE, and MAP values of 0.29mm/d, 0.75mm/d, 13% at maize site, −0.33mm/d, 0.81mm/d, and 14% at vegetable sites.

Mapping of vulnerability of flooded area in arid region. Case study: area of Ghardaïa-Algeria

The issue of natural hazards in general and flooding in particular is a hot topic which marks memorable actions in the world and specifically in Algeria. Managing this risk is becoming more of a necessity that must include all stakeholders and all possible means available. The objective of this work is the vulnerability mapping of flood areas in the arid region Oued M’zab-region Ghardaia. It’s about implement predictive models and flood control. This allows the development of a risk prevention plan to flooding. To achieve this goal we evaluated the hazard and vulnerability. The evaluation of the risk passes by a study of the mode of rising. This study leads to the determination of the synthetic hygrogram which are taken into account under the boundary conditions upstream of a hydraulic model of the nonpermanent flows on free face. The results obtained for one period of return given constitute the risk of the floods relating to these hydrograms. The vulnerability is represented by a rate which translates the objective of protection against a probable risk. Two types of models are tested on a section of Oued M’zab-region where the data are available. Initially, are considered hydrological models (HEC-HMS 1D). In the second place of the hydraulic models (HEC-RAS 1D). After comparison of the results obtained by various simulations, the vulnerable zones are thus charted.

Regeneration properties of a Populus euphratica riparian forest located in the vicinity of the Ejina Oasis, Inner Mongolia, China

To explore the regeneration properties of a Populus euphratica Oliv. forest under unstable environmental conditions, we performed replicate censuses to determine the sapling dynamics of a P. euphratica population in the vicinity of the Ejina Oasis (Inner Mongolia). Even when the stands were established on riverside flatland, we detected slight variations in ground levels and salt concentrations. Due to leaching by flood water, the salinity of topsoil was lower in the riverbed than on the riverbank. Newly recruited saplings grew on riverbanks with high-salinity soil. Saplings were distributed over a wide area via fluctuating water levels, and those growing where salt levels were relatively low were able to grow more easily and become canopy trees. Small individuals comprise a sapling bank on the forest floor that is relatively stable. The dieback of larger saplings results in few reaching a height of more than 2 m. The growth of saplings (including new recruits) is balanced by the death of smaller saplings and the dieback of larger saplings. Individual saplings persist for about 4 years on the forest floor. In summary, hydrological events coupled with soil conditions may drive vegetation distribution patterns in riparian areas in arid regions. P. euphratica forests regenerate via a sapling bank rather than a seed bank. Yearly fluctuations in water flow facilitate the spread of the sapling bank, which guarantees regeneration of the forest. Dieback through partial defoliation is a mechanism used by saplings to escape adverse conditions, thereby maintaining a stable state in arid regions.