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30 September 2022, Volume 14 Issue 9 Previous Issue    Next Issue
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Research article
Attribution analysis and multi-scenario prediction of NDVI drivers in the Xilin Gol grassland, China
XU Mengran, ZHANG Jing, LI Zhenghai, MO Yu
Journal of Arid Land. 2022, 14 (9): 941-961.   DOI: 10.1007/s40333-022-0032-x
Abstract ( 59 )   HTML ( 10 )     PDF (4728KB) ( 116 )  

Grassland degradation is influenced by climate change and human activities, and has become a major obstacle for the development of arid and semi-arid areas, posing a series of environmental and socio-economic problems. An in-depth understanding of the inner relations among grassland vegetation dynamics, climate change, and human activities is therefore greatly significant for understanding the variation in regional environmental conditions and predicting future developmental trends. Based on MODIS (moderate resolution imaging spectroradiometer) NDVI (normalized difference vegetation index) data from 2000 to 2020, our objective is to investigate the spatiotemporal changes of NDVI in the Xilin Gol grassland, Inner Mongolia Autonomous Region, China. Combined with 12 natural factors and human activity factors in the same period, the dominant driving factors and their interactions were identified by using the geographic detector model, and multiple scenarios were also simulated to forecast the possible paths of future NDVI changes in this area. The results showed that: (1) in the past 21 a, vegetation cover in the Xilin Gol grassland exhibited an overall increasing trend, and the vegetation restoration (84.53%) area surpassed vegetation degradation area (7.43%); (2) precipitation, wind velocity, and livestock number were the dominant factors affecting NDVI (the explanatory power of these factors exceeded 0.4). The interaction between average annual wind velocity and average annual precipitation, and between average annual precipitation and livestock number greatly affected NDVI changes (the explanatory power of these factors exceeded 0.7). Moreover, the impact of climate change on NDVI was more significant than human activities; and (3) scenario analysis indicated that NDVI in the Xinlin Gol grassland increased under the scenarios of reduced wind velocity, increased precipitation, and ecological protection. In contrast, vegetation coverage restoration in this area was significantly reduced under the scenarios of unfavorable climate conditions and excessive human activities. This study provides a scientific basis for future vegetation restoration and management, ecological environmental construction, and sustainable natural resource utilization in this area.

Monitoring and analysis of snow cover change in an alpine mountainous area in the Tianshan Mountains, China
ZHANG Yin, GULIMIRE Hanati, SULITAN Danierhan, HU Keke
Journal of Arid Land. 2022, 14 (9): 962-977.   DOI: 10.1007/s40333-022-0071-3
Abstract ( 37 )   HTML ( 4 )     PDF (5345KB) ( 57 )  

Estimating the snow cover change in alpine mountainous areas (in which meteorological stations are typically lacking) is crucial for managing local water resources and constitutes the first step in evaluating the contribution of snowmelt to runoff and the water cycle. In this paper, taking the Jingou River Basin on the northern slope of the Tianshan Mountains, China as an example, we combined a new moderate-resolution imaging spectroradiometer (MODIS) snow cover extent product over China spanning from 2000 to 2020 with digital elevation model (DEM) data to study the change in snow cover and the hydrological response of runoff to snow cover change in the Jingou River Basin under the background of climate change through trend analysis, sensitivity analysis and other methods. The results indicate that from 2000 to 2020, the annual average temperature and annual precipitation in the study area increased and snow cover fraction (SCF) showed obvious signs of periodicity. Furthermore, there were significant regional differences in the spatial distribution of snow cover days (SCDs), which were numerous in the south of the basin and sparse in the central of the basin. Factors affecting the change in snow cover mainly included temperature, precipitation, elevation, slope and aspect. Compared to precipitation, temperature had a greater impact on SCF. The annual variation in SCF was limited above the elevation of 4200 m, but it fluctuated greatly below the elevation of 4200 m. These results can be used to establish prediction models of snowmelt and runoff for alpine mountainous areas with limited hydrological data, which can provide a scientific basis for the management and protection of water resources in alpine mountainous areas.

Cost analysis of sand barriers in desertified regions based on the land grid division model
YANG Suchang, QU Zhun
Journal of Arid Land. 2022, 14 (9): 978-992.   DOI: 10.1007/s40333-022-0072-2
Abstract ( 30 )   HTML ( 6 )     PDF (1455KB) ( 33 )  

Sand barriers are the most widely used mechanical implements for wind-blown sand control and desertification prevention. However, there is no standard quantitative cost analysis of the sizes and materials required for sand barriers. In this study, based on the original land grid division model for optimal resource utilization, we calculated the total side lengths of square and regular hexagonal sand barriers with the sizes of 1.0 m×1.0 m, 2.0 m×2.0 m, and 3.0 m×3.0 m in a desertified region of the Shapotou area on the southeastern edge of the Tengger Desert, China. Then, through literature review and social survey, we obtained the material cost and material utilization amount of sand barriers with different materials and sizes. Finally, we calculated the costs of square and regular hexagonal sand barriers comprised of wheat straw, corn stalk, Salix mongolica, poly lactic acid, magnesium cement, and high-density polyethylene, with the sizes of 1.0 m×1.0 m, 2.0 m×2.0 m, and 3.0 m×3.0 m. The results show that the material cost of regular hexagonal corn stalk sand barriers with the size of 3.0 m×3.0 m is the lowest, while the material cost of square magnesium cement sand barriers with the size of 1.0 m×1.0 m is the highest. When using the same material, the cost of regular hexagonal sand barriers is lower than that of square sand barriers with the same size. When using the same size, the cost of sand barriers with corn stalk material is lower than that of sand barriers with other materials. Based on the above analysis, we can conclude that the economic benefits of regular hexagonal sand barriers are greater than those of square sand barriers. This study provides a theoretical basis for accurately calculating the material cost of sand barriers, particularly for the estimated cost of mechanized sand barrier engineering projects.

Effects of different types of guardrails on sand transportation of desert highway pavement
GAO Li, CHENG Jianjun, WANG Haifeng, YUAN Xinxin
Journal of Arid Land. 2022, 14 (9): 993-1008.   DOI: 10.1007/s40333-022-0030-z
Abstract ( 33 )   HTML ( 5 )     PDF (3492KB) ( 92 )  

Guardrail, an important highway traffic safety facility, is mainly used to prevent vehicles from accidentally driving off the road and to ensure driving safety. Desert highway guardrails hinder the movement of wind-blown sand, resulting in the decline of sand transportation by the pavement and the deposition of sand gains on the pavement, and endangering traffic safety. To reveal the influence of guardrails on sand transportation of desert highway pavement, we tested the flow field and sand transport volume distribution around the concrete, W-beam, and cable guardrails under different wind velocities through wind tunnel simulation. Wind velocity attenuation coefficients, sand transportation quantity, and sand transportation efficiency are used to measure sand transportation of highway pavement. The results show that the sand transportation of highway pavement was closely related to the zoning characteristics of flow field and variation of wind velocity around the guardrails. The flow field of the concrete guardrail was divided into deceleration, acceleration, and vortex zones. The interaction between the W-beam guardrail and wind-blown sand was similar to that of lower wind deflector. Behind and under the plates, there were the vortex zone and acceleration zone, respectively. The acceleration zone was conducive to transporting sand on the pavement. The cable guardrail only caused wind velocity variability within the height range of guardrail, and there was no sand deposition on the highway pavement. When the cable, W-beam, and concrete guardrails were used, the total transportation quantities on the highway pavement were 423.53, 415.74, and 136.53 g/min, respectively, and sand transportation efficiencies were 99.31%, 91.25%, and 12.84%, respectively. From the perspective of effective sand transportation on the pavement, the cable guardrail should be preferred as a desert highway guardrail, followed by the W-beam guardrail, and the concrete guardrail is unsuitable. The study results provide theoretical basis for the optimal design of desert highway guardrails and the prevention of wind-blown sand disasters on the highway pavement.

Research on wind erosion processes and controlling factors based on wind tunnel test and 3D laser scanning technology
YAN Ping, WANG Xiaoxu, ZHENG Shucheng, WANG Yong, LI Xiaomei
Journal of Arid Land. 2022, 14 (9): 1009-1021.   DOI: 10.1007/s40333-022-0103-z
Abstract ( 30 )   HTML ( 3 )     PDF (2081KB) ( 89 )  

The study of wind erosion processes is of great importance to the prevention and control of soil wind erosion. In this study, three structurally intact soil samples were collected from the steppe of Inner Mongolia Autonomous Region, China and placed in a wind tunnel where they were subjected to six different wind speeds (10, 15, 17, 20, 25, and 30 m/s) to simulate wind erosion in the wind tunnel. After each test, the soil surfaces were scanned by a 3D laser scanner to create a high-resolution Digital Elevation Model (DEM), and the changes in wind erosion mass and microtopography were quantified. Based on this, we performed further analysis of wind erosion-controlling factors. The study results showed that the average measurement error between the 3D laser scanning method and weighing method was 6.23% for the three undisturbed soil samples. With increasing wind speed, the microtopography on the undisturbed soil surface first became smooth, and then fine stripes and pits gradually developed. In the initial stage of wind erosion processes, the ability of the soil to resist wind erosion was mainly affected by the soil hardness. In the late stage of wind erosion processes, the degree of soil erosion was mainly affected by soil organic matter and CaCO3 content. The results of this study are expected to provide a theoretical basis for soil wind erosion control and promote the application of 3D laser scanners in wind erosion monitoring.

The role of glacial gravel in community development of vascular plants on the glacier forelands of the Third Pole
WEI Tianfeng, SHANGGUAN Donghui, TANG Xianglong, QIN Yu
Journal of Arid Land. 2022, 14 (9): 1022-1037.   DOI: 10.1007/s40333-022-0073-1
Abstract ( 29 )   HTML ( 5 )     PDF (2669KB) ( 43 )  

On a deglaciated terrain, glacial gravel is the primary component of the natural habitat for vascular plant colonization and succession. Knowledge regarding the role of glacial gravel in vascular plant growth, however, remains limited. In this study, an unmanned aerial vehicle (UAV) was used to investigate plant family composition, species richness, fractional vegetation cover (FVC), and gravel cover (GC) along elevational gradients on the three glacier forelands (Kekesayi, Jiangmanjiaer, and Koxkar Baxi) of the Third Pole (including the eastern Pamir Plateau and western Tianshan Mountains) in China. We then analyzed the spatial characteristics of vascular plants followed by exploring the effect of glacial gravel on vascular plants. Findings indicated that FVC on these glacier forelands generally decreased as the elevation increased or distance from the current glacier terminus decreased. The shady slope (Kekesayi) was more vegetated in comparison to the sunny slope (Jiangmanjiaer) at the glacier basin scale, and the warm and humid deglaciated terrain (Koxkar Baxi) had the highest FVC at the regional scale. Plant family composition and species richness on the glacier forelands decreased with rising elevation, with the exception of those on the Jiangmanjiaer glacier foreland. The relationships between FVC and GC presented negative correlations; particularly, they exhibited variations in power functions on the Kekesayi and Jiangmanjiaer glacier forelands of the eastern Pamir Plateau and a linear function on the Koxkar Baxi glacier foreland of the western Tianshan Mountains. Glacial gravel was found to be conducive to vegetation colonization and development in the early succession stage up until vascular plants adapted to the cold and arid climatic condition, whereas it is unfavorable to the expansion of vascular plants in the later succession stage. These findings suggested that the spatial difference of plant characteristics had close connections with regional climatic and topographic conditions, as well as glacial gravel distribution. In addition, we concluded that aerial photographs can be an asset for studying the functions of micro-environment in vegetation colonization as well as succession on the glacier forelands.

Water utilization of typical plant communities in desert steppe, China
CHEN Juan, WANG Xing, SONG Naiping, WANG Qixue, WU Xudong
Journal of Arid Land. 2022, 14 (9): 1038-1054.   DOI: 10.1007/s40333-022-0031-y
Abstract ( 42 )   HTML ( 7 )     PDF (2791KB) ( 84 )  

Water is a limiting factor in the restoration and construction of desert steppe. Exploring plant water sources is necessary to understand soil-plant interactions and species coexistence; however, water sources of major plant communities within the desert steppe of Ningxia Hui Autonomous Region, China remain poorly understood. In this study, we analyzed the water uptake of plants in four typical communities: Agropyron mongolicum Keng.; Sophora alopecuroids Linn.; Stipa breviflora Griseb., and Achnatherum splendens (Trin.) Nevski communities. Stable isotopes δD and δ18O in the xylem of plant and soil water at different soil depths were analyzed. An IsoSource model was used to determine the soil depths from which plants obtained water. Results showed that A. mongolicum community obtained water predominantly from 0-20 and 40-80 cm depth, S. alopecuroids community from 0-20 cm depth, S. breviflora community from 0-40 cm depth, and A. splendens community from 0-20 and 80-140 cm depths. S. alopecuroides had a wider range of soil depths for water extraction, i.e., utilizing different water sources depending on habitat, and the plasticity of its water uptake pattern determined its role in different communities. Water source of plants relayed heavily on the distribution of their roots. Competition for soil water exists between different plant life forms in the sierozem habitat (A. mongolicum, S. alopecuroids, and S. breviflora communities), and in the sandy soil habitat (A. splendens community). The use of soil water by A. splendens community is more spatially differentiated, and shrubs and herbs can coexist stably. Under the pattern of extended drought period in the future, sierozem habitat may be more favorable for the formation of a dominant monoculture community type of perennial fibrous plants. In aeolian sandy soil habitat, A. splendens had a strong competitive advantage, and the growth of shallow-rooted plants was easily suppressed.

Carbon inputs regulate the temperature sensitivity of soil respiration in temperate forests
LIU Yulin, LI Jiwei, HAI Xuying, WU Jianzhao, DONG Lingbo, PAN Yingjie, SHANGGUAN Zhouping, WANG Kaibo, DENG Lei
Journal of Arid Land. 2022, 14 (9): 1055-1068.   DOI: 10.1007/s40333-022-0102-0
Abstract ( 35 )   HTML ( 4 )     PDF (2858KB) ( 93 )  

Litter and root activities may alter the temperature sensitivity (Q10) of soil respiration. However, existing studies have not provided a comprehensive understanding of the effects of litter and root carbon inputs on the Q10 of soil respiration in different seasons. In this study, we used the trench method under in situ conditions to measure the total soil respiration (Rtotal), litter-removed soil respiration (Rno-litter), root-removed soil respiration (Rno-root), and the decomposition of soil organic matter (i.e., both litter and root removal; RSOM) in different seasons of pioneer (Populus davidiana Dode) and climax (Quercus liaotungensis Mary) forests on the Loess Plateau, China. Soil temperature, soil moisture, litter biomass, fine root biomass, litter carbon, and root carbon were analyzed to obtain the drive mechanism of the Q10 of soil respiration in the two forests. The results showed that the Q10 of soil respiration exhibited seasonality, and the Q10 of soil respiration was higher in summer. The litter enhanced the Q10 of soil respiration considerably more than the root did. Soil temperature, soil moisture, fine root biomass, and litter carbon were the main factors used to predict the Q10 of different soil respiration components. These findings indicated that factors affecting the Q10 of soil respiration highly depended on soil temperature and soil moisture as well as related litter and root traits in the two forests, which can improve our understanding of soil carbon-climate feedback in global warming. The results of this study can provide reference for exploring soil respiration under temperate forest restoration.