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30 November 2023, Volume 15 Issue 11 Previous Issue    Next Issue
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Research article
Combining RUSLE model and the vegetation health index to unravel the relationship between soil erosion and droughts in southeastern Tunisia
Olfa TERWAYET BAYOULI, ZHANG Wanchang, Houssem TERWAYET BAYOULI
Journal of Arid Land. 2023, 15 (11): 1269-1289.   DOI: 10.1007/s40333-023-0110-8
Abstract ( 30 )   HTML ( 226 )     PDF (2075KB) ( 181 )  

Droughts and soil erosion are among the most prominent climatic driven hazards in drylands, leading to detrimental environmental impacts, such as degraded lands, deteriorated ecosystem services and biodiversity, and increased greenhouse gas emissions. In response to the current lack of studies combining drought conditions and soil erosion processes, in this study, we developed a comprehensive Geographic Information System (GIS)-based approach to assess soil erosion and droughts, thereby revealing the relationship between soil erosion and droughts under an arid climate. The vegetation condition index (VCI) and temperature condition index (TCI) derived respectively from the enhanced vegetation index (EVI) MOD13A2 and land surface temperature (LST) MOD11A2 products were combined to generate the vegetation health index (VHI). The VHI has been conceived as an efficient tool to monitor droughts in the Negueb watershed, southeastern Tunisia. The revised universal soil loss equation (RUSLE) model was applied to quantitatively estimate soil erosion. The relationship between soil erosion and droughts was investigated through Pearson correlation. Results exhibited that the Negueb watershed experienced recurrent mild to extreme drought during 2000-2016. The average soil erosion rate was determined to be 1.8 t/(hm2·a). The mountainous western part of the watershed was the most vulnerable not only to soil erosion but also to droughts. The slope length and steepness factor was shown to be the most significant controlling parameter driving soil erosion. The relationship between droughts and soil erosion had a positive correlation (r=0.3); however, the correlation was highly varied spatially across the watershed. Drought was linked to soil erosion in the Negueb watershed. The current study provides insight for natural disaster risk assessment, land managers, and stake-holders to apply appropriate management measures to promote sustainable development goals in fragile environments.

Evaluation of restoration success in arid rangelands of Iran based on the variation of ecosystem services
Mohsen SHARAFATMANDRAD, Azam KHOSRAVI MASHIZI
Journal of Arid Land. 2023, 15 (11): 1290-1314.   DOI: 10.1007/s40333-023-0073-9
Abstract ( 21 )   HTML ( 200 )     PDF (984KB) ( 153 )  

The plantation of non-native species is one of the most expensive ecological restoration measures in arid and semi-arid areas, while its impacts on local communities are largely ignored. This study assessed the rate of change and the dynamic degree of the economic values of ecosystem services related to local conservation (water yield, stocking rate and aesthetic value) and preserving the future (carbon sequestration, soil protection, soil stability and habitat provision) to determine the restoration success of the plantation of non-native species Haloxylon ammodendron (C.A.Mey.) Bunge ex Fenzl (15- and 30-year-old) in parts of arid rangelands of Bardsir region, Kerman Province, Iran. We investigated the impacts of the two plantations on the seven ecosystem services and ecosystem structures (horizontal and vertical structures, vegetation composition and species diversity) based on field sampling and measurements at four sampling sites (i.e., control, degraded, and 15- and 30-year-old plantation sites) in spring and summer of 2022. The restoration success of the plantation of non-native species was then examined by assessing the rate of change and the dynamic degree of the total economic value of all ecosystem services as well as the rate of change and the dynamic degree of the economic values of ecosystem services for the two groups (local conservation and preserving the future). Although the plantation of non-native species H. ammodendron enormously improved the vertical and horizontal structures of ecosystems, it failed to increase species diversity and richness fully. Further, despite the plantation of non-native species H. ammodendron had significantly increased the economic values of all ecosystem services, it was only quite successful in restoring carbon sequestration. Path analysis showed that plantation age had a significant impact on restoration success directly and indirectly (through changing ecosystem structures and services). The dynamic degree of the economic values of ecosystem services related to local conservation and preserving the future at the 15- and 30-year-old plantation sites indicated that the two plantations successfully restored the ecosystem services related to preserving the future. The presented method can help managers select the best restoration practices and predict their ecological-social success, especially for the plantation of high-risk non-native species in arid and semi-arid areas.

Spatiotemporal variation of surface albedo and its influencing factors in northern Xinjiang, China
YUAN Shuai, LIU Yongqiang, QIN Yan, ZHANG Kun
Journal of Arid Land. 2023, 15 (11): 1315-1339.   DOI: 10.1007/s40333-023-0069-5
Abstract ( 29 )   HTML ( 6 )     PDF (5384KB) ( 28 )  

Surface albedo is a quantitative indicator for land surface processes and climate modeling, and plays an important role in surface radiation balance and climate change. In this study, by means of the MCD43A3 surface albedo product developed on the basis of Moderate Resolution Imaging Spectroradiometer (MODIS), we analyzed the spatiotemporal variation, persistence status, land cover type differences, and annual and seasonal differences of surface albedo, as well as the relationship between surface albedo and various influencing factors (including Normalized Difference Snow Index (NDSI), precipitation, Normalized Difference Vegetation Index (NDVI), land surface temperature, soil moisture, air temperature, and digital elevation model (DEM)) in the north of Xinjiang Uygur Autonomous Region (northern Xinjiang) of Northwest China from 2010 to 2020 based on the unary linear regression, Hurst index, and Pearson's correlation coefficient analyses. Combined with the random forest (RF) model and geographical detector (Geodetector), the importance of the above-mentioned influencing factors as well as their interactions on surface albedo were quantitatively evaluated. The results showed that the seasonal average surface albedo in northern Xinjiang was the highest in winter and the lowest in summer. The annual average surface albedo from 2010 to 2020 was high in the west and north and low in the east and south, showing a weak decreasing trend and a small and stable overall variation. Land cover types had a significant impact on the variation of surface albedo. The annual average surface albedo in most regions of northern Xinjiang was positively correlated with NDSI and precipitation, and negatively correlated with NDVI, land surface temperature, soil moisture, and air temperature. In addition, the correlations between surface albedo and various influencing factors showed significant differences for different land cover types and in different seasons. To be specific, NDSI had the largest influence on surface albedo, followed by precipitation, land surface temperature, and soil moisture; whereas NDVI, air temperature, and DEM showed relatively weak influences. However, the interactions of any two influencing factors on surface albedo were enhanced, especially the interaction of air temperature and DEM. NDVI showed a nonlinear enhancement of influence on surface albedo when interacted with land surface temperature or precipitation, with an explanatory power greater than 92.00%. This study has a guiding significance in correctly understanding the land-atmosphere interactions in northern Xinjiang and improving the regional land-surface process simulation and climate prediction.

Contribution of groundwater to the formation of sand dunes in the Badain Jaran Desert, China
WANG Wang, CHEN Jiaqi, CHEN Jiansheng, WANG Tao, ZHAN Lucheng, ZHANG Yitong, MA Xiaohui
Journal of Arid Land. 2023, 15 (11): 1340-1354.   DOI: 10.1007/s40333-023-0032-5
Abstract ( 24 )   HTML ( 213 )     PDF (2119KB) ( 183 )  

The tallest sand dune worldwide is located in the Badain Jaran Desert (BJD), China, and has been standing for thousands of years. Previous studies have conducted limited physical exploration and excavation on the formation of sand dunes and have proposed three viewpoints, that is, bedrock control, wind dominance, and groundwater maintenance with no unified conclusion. Therefore, this study analyzed the underlying bedding structure of sand dunes in the BJD. Although the bedrock of sand dunes is uplifted and wind controls the shape of dunes, the main cause of dune formation is groundwater that maintains the deposition of calcareous sandstone and accumulation of aeolian sand. According to water transport model and vapor transports in the unsaturated zone of sand dunes, capillary water transport height is limited with film water constituting the main form of water in dunes. Chemical properties and temperature of groundwater showed that aquifers in different basins receive relatively independent recharge from deep sources in the crater. Result of dune formation mechanism is of considerable importance in understanding groundwater circulation and provides a new perspective on water management in arid desert areas.

Multiple assessments, source determination, and health risk apportionment of heavy metal(loid)s in the groundwater of the Shule River Basin in northwestern China
WEN Xiaohu, LI Leiming, WU Jun, LU Jian, SHENG Danrui
Journal of Arid Land. 2023, 15 (11): 1355-1375.   DOI: 10.1007/s40333-023-0111-7
Abstract ( 22 )   HTML ( 4 )     PDF (1525KB) ( 137 )  

Global ecosystems and public health have been greatly impacted by the accumulation of heavy metal(loid)s in water. Source-specific risk apportionment is needed to prevent and manage potential groundwater contamination with heavy metal(loid)s. The heavy metal(loid)s contamination status, water quality, ecological risk, and health risk apportionment of the Shule River Basin groundwater are poorly understood. Therefore, field sampling was performed to explore the water quality and risk of heavy metal(loid)s in the groundwater of the Shule River Basin in northwestern China. A total of 96 samples were collected from the study area to acquire data for water quality and heavy metal(loid)s risk. There was noticeable accumulation of ferrum in the groundwater of the Shule River Basin. The levels of pollution were considered to be moderately low, as evaluated by the degree of contamination, heavy metal evaluation index, heavy metal pollution index, and Nemerow pollution index. The ecological risks were also low. However, an assessment of the water quality index revealed that only 58.34% of the groundwater samples had good water quality. The absolute principal component scores-multiple linear regression model was more suited for this study area than the positive matrix factorization model. There were no obvious noncarcinogenic or carcinogenic concerns for all types of receptors according to the values of the total hazard index and total carcinogenic risk. The human activities and the initial geological environment factor (65.85%) was the major source of noncarcinogenic risk (residential children: 87.56%; residential adults: 87.52%; recreational children: 86.77%; and recreational adults: 85.42%), while the industrial activity factor (16.36%) was the major source of carcinogenic risk (residential receptors: 87.96%; and recreational receptors: 68.73%). These findings provide fundamental and crucial information for reducing the health issues caused by heavy metal(loid)s contamination of groundwater in arid areas.

Subsurface irrigation with ceramic emitters improves wolfberry yield and economic benefits on the Tibetan Plateau, China
HAN Mengxue, ZHANG Lin, LIU Xiaoqiang
Journal of Arid Land. 2023, 15 (11): 1376-1390.   DOI: 10.1007/s40333-023-0034-3
Abstract ( 14 )   HTML ( 5 )     PDF (2328KB) ( 60 )  

Climate warming has led to the expansion of arable land at high altitudes, but it has also increased the demand for water use efficiency (WUE). To address this issue, the development of water-saving irrigation technology has become crucial in improving water productivity and economic returns. This study aimed to assess the impacts of three irrigation methods on water productivity and economic returns in wolfberry (Lycium barbarum L.) cultivation on the Tibetan Plateau, China during a two-year field trial. Results showed that subsurface irrigation with ceramic emitters (SICE) outperformed surface drip irrigation (DI) and subsurface drip irrigation (SDI) in terms of wolfberry yield. Over the two-year period, the average yield with SICE increased by 8.0% and 2.3% compared with DI and SDI, respectively. This improvement can be attributed to the stable soil moisture and higher temperature accumulation achieved with SICE. Furthermore, SICE exhibited higher WUE, with 14.6% and 4.5% increases compared with DI and SDI, respectively. In addition to the agronomic benefits, SICE also proved advantageous in terms of economic returns. Total average annual input costs of SICE were lower than the other two methods starting from the 8th year. Moreover, the benefit-cost ratio of SICE surpassed the other methods in the 4th year and continued to widen the gap with subsequent year. These findings highlight SICE as an economically viable water-saving irrigation strategy for wolfberry cultivation on the Tibetan Plateau. Thus, this research not only provides an effective water-saving irrigation strategy for wolfberry cultivation but also offers insights into addressing irrigation-related energy challenges in other crop production systems.

Effects of dieback on the vegetative, chemical, and physiological status of mangrove forests, Iran
Vahid Farashi KAHNOUJ, Marzieh REZAI, Rasool MAHDAVI, Maryam MOSLEHI, Saiedeh ESKANDARI
Journal of Arid Land. 2023, 15 (11): 1391-1404.   DOI: 10.1007/s40333-023-0031-6
Abstract ( 19 )   HTML ( 5 )     PDF (966KB) ( 14 )  

Mangrove forests are valuable resources in tropical and subtropical regions, which have been faced dieback due to various human activities including rapid expansion of shrimp farming, urban development, and pollution, as well as natural factors such as rising sea level, increasing air temperature, drought, and sharp decrease in rainfall. However, the mechanisms of dieback of mangrove forests are not well understood. Therefore, this research aimed to assess the vegetative, chemical, and physiological status of grey mangrove (Avicennia marina (Forsk.) Vierh.) forests at different intensities of dieback in the Hormozgan Province, Iran. A total of 40 plots categorized into four dieback intensities (severe, medium, low, and control) were randomly selected for monitoring, and various parameters related to vegetative, chemical, and physiological status of grey mangrove forests were examined. The results revealed that the control group had the highest tree density, seedling density, vitality levels, aerial root density, and aerial root height. Generally, as dieback severity increased, a decrease in demographic and vegetative parameters of trees and seedlings was observed in the dieback treatments. The amounts of heavy metals (lead, cadmium, and nickel) in the sediment, roots, and leaves of grey mangrove trees at different dieback levels indicated that lead levels were the highest in the sediment, roots, and leaves in the severe dieback treatment. At the same time, the control had the lowest values. Cadmium concentrations in the sediment followed the pattern of severe dieback>moderate dieback>low dieback>control with no significant differences in the roots and leaves. Nickel amounts in all three parts, i.e., sediment, roots, and leaves showed the highest levels in the severe dieback treatment. Furthermore, metal level analysis in the organs of grey mangrove trees at different dieback levels revealed that lead and nickel were more abundant in the root organ compared with the leaves. In contrast, the leaf organ exhibited the highest cadmium levels. Dieback significantly impacted water electrical conductivity (EC), soil organic carbon (SOC), and chlorophyll a, b, and total chlorophyll contents, with the highest values observed in the severe dieback treatment. However, no significant differences were observed in acidity and carotenoid levels. In conclusion, sediment erosion and heavy metal accumulation were critical contributors to dieback of grey mangrove trees, affecting their physiological, vegetative, and plant production characteristics. As the ability of these plants to rehabilitate has diminished, effective management planning is imperative in dieback-affected areas.

Plant growth-promoting properties and anti-fungal activity of endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta in arid lands
ZHAO Mengqi, SU Huan, HUANG Yin, Rashidin ABDUGHENI, MA Jinbiao, GAO Jiangtao, GUO Fei, LI Li
Journal of Arid Land. 2023, 15 (11): 1405-1420.   DOI: 10.1007/s40333-023-0071-y
Abstract ( 18 )   HTML ( 4 )     PDF (578KB) ( 156 )  

Endophytes, as crucial components of plant microbial communities, significantly contribute to enhancing the absorption of nutrients such as nitrogen and phosphorus by their hosts, promote plant growth, and degrade pathogenic fungal mycelia. In this study, an experiment was conducted in August 2022 to explore the growth-promoting potential of endophytic bacterial strains isolated from two medical plant species, Thymus altaicus and Salvia deserta, using a series of screening media. Plant samples of Thymus altaicus and Salvia deserta were collected from Zhaosu County and Habahe County in Xinjiang Uygur Autonomous Region, China, in July 2021. Additionally, the inhibitory effects of endophytic bacterial strains on the four pathogenic fungi (Fusarium oxysporum, Fulvia fulva, Alternaria solani, and Valsa mali) were determined through the plate confrontation method. A total of 80 endophytic bacterial strains were isolated from Thymus altaicus, while a total of 60 endophytic bacterial strains were isolated from Salvia deserta. The endophytic bacterial strains from both Thymus altaicus and Salvia deserta exhibited plant growth-promoting properties. Specifically, the strains of Bacillus sp. TR002, Bacillus sp. TR005, Microbacterium sp. TSB5, and Rhodococcus sp. TR013 demonstrated strong cellulase-producing activity, siderophore-producing activity, phosphate solubilization activity, and nitrogen-fixing activity, respectively. Out of 140 endophytic bacterial strains isolated from Thymus altaicus and Salvia deserta, 104 strains displayed anti-fungal activity against Fulvia fulva, Alternaria solani, Fusarium oxysporum, and Valsa mali. Furthermore, the strains of Bacillus sp. TR005, Bacillus sp. TS003, and Bacillus sp. TSB7 exhibited robust inhibition rates against all the four pathogenic fungi. In conclusion, the endophytic bacterial strains from Thymus altaicus and Salvia deserta possess both plant growth-promoting and anti-fungal properties, making them promising candidates for future development as growth-promoting agents and biocontrol tools for plant diseases.