Search Results (75)

Understanding the spatiotemporal evolution of soil salinization is essential for elucidating its driving mechanisms and supporting sustainable land and water management in arid regions. In this study, the Alar Reclamation Area in Xinjiang, a typical desert–oasis transition zone, was selected to investigate the drivers of spatiotemporal variation in soil salinization. GRACE gravity satellite observations for the period 2002–2022 were used to estimate groundwater storage (GWS) fluctuations. Contemporaneous Landsat multispectral imagery was employed to derive the normalized difference vegetation index (NDVI) and a salinity index (SI), which were further integrated to construct the salinization detection index (SDI). Pearson correlation analysis, variance inflation factor analysis, and a stepwise regression framework were employed to identify the dominant factors controlling the occurrence and evolution of soil salinization. The results showed that severe salinization was concentrated along the Tarim River and in low-lying downstream zones, while salinity levels in the middle and upper parts of the reclamation area had generally declined or shifted to non-salinized conditions. SDI exhibited a strong negative correlation with NDVI (p ≤ 0.01) and a significant positive correlation with both irrigation quota and GWS (p ≤ 0.01). A pronounced collinearity was observed between GWS and irrigation quota. NDVI and GWS were identified as the principal drivers governing spatial–temporal variations in SDI. The resulting regression model (SDI = 0.946 − 0.959 × NDVI + 0.318 × GWS) established a robust quantitative relationship between SDI, NDVI and GWS, characterized by a high coefficient of determination (R² = 0.998). These statistics indicated the absence of multicollinearity (variance inflation factor, VIF < 5) and autocorrelation (Durbin–Watson ≈ 1.876). These findings provide a theoretical basis for the management of saline–alkali lands in the upper Tarim River region and offer scientific support for regional ecological sustainability. Full article

Populus euphratica is a key constructive species in desert ecosystems and plays a vital role in maintaining their stability. However, effective automated methods for accurately delineating its distribution outlines are currently lacking. This study used the mainstream area of the Tarim River as a case study and proposed a technical solution for identifying the distribution outline of Populus euphratica using multi-source thematic classification data. First, cropland thematic data were used to optimize the accuracy of the Populus euphratica classification raster data. Discrete points were removed based on density to reduce their impact on boundary identification. Then, a hierarchical identification scheme was constructed using the alpha-shape algorithm to identify the boundaries of high- and low-density Populus euphratica distribution areas separately. Finally, the outlines of the Populus euphratica distribution polygons were smoothed, and the final distribution outline data were obtained after spatial merging. The results showed the following: (1) Applying a closing operation to the cropland thematic classification data to obtain the distribution range of shelterbelts effectively eliminated misclassified pixels. Using the kd-tree algorithm to remove sparse discrete points based on density, with a removal ratio of 5%, helped suppress the interference of outlier point sets on the Populus euphratica outline identification. (2) Constructing a hierarchical identification scheme based on differences in Populus euphratica density is critical for accurately delineating its distribution contours. Using the alpha-shape algorithm with parameters set to α = 0.02 and α = 0.006, the reconstructed geometries effectively covered both densely and sparsely distributed Populus euphratica areas. (3) In the morphological processing stage, a combination of three methods—Gaussian filtering, equidistant expansion, and gap filling—effectively ensured the accuracy of the Populus euphratica outline. Among the various smoothing algorithms, Gaussian filtering yielded the best results. The equidistant expansion method reduced the impact of elongated cavities, thereby contributing to boundary accuracy. This study enhances the automation of Populus euphratica vector data mapping and holds significant value for the scientific management and research of desert vegetation. Full article

Monitoring ecosystem dynamics in arid regions requires robust indicators that can capture spatial heterogeneity and diverse ecological drivers. In this study, we introduce and evaluate two novel ecological indices: the Arid-region Remote Sensing Ecological Index (ARSEI), specifically designed for desert environments, and the Composite Remote Sensing Ecological Index (CoRSEI), which integrates both desert and non-desert systems. These indices are compared with the traditional Remote Sensing Ecological Index (RSEI) in the Tarim River Basin from 2000 to 2023. Principal component analysis (PCA) revealed that RSEI maintained the highest structural compactness (average PCA1 = 87.49%). In contrast, ARSEI (average PCA1 = 78.62%) enhanced sensitivity to albedo and vegetation (NDVI) in arid environments. Spearman correlation analysis further demonstrated that ARSEI was more strongly correlated with NDVI (ρ = 0.49) and precipitation (ρ = 0.62) than RSEI, confirming its improved responsiveness under water-limited conditions. CoRSEI exhibited higher internal consistency and spatial adaptability (mean values ranging from 0.45 to 0.56), with slight ecological improvements observed between 2000 and 2023. Ecological drivers varied across habitat types. In desert areas, evapotranspiration, precipitation, and soil moisture were the main determinants of ecological status, showing high coupling and synchrony. In non-desert regions, soil moisture and precipitation remained dominant, but vegetation indices and disturbance factors (e.g., fire density) exerted stronger long-term influences. Partial dependence analyses further confirmed nonlinear, region-specific responses, such as the threshold effects of precipitation on vegetation growth. Overall, our findings highlight the importance of differentiated ecological modeling. ARSEI enhances sensitivity in desert ecosystems, whereas CoRSEI captures landscape-scale variability across desert and non-desert regions. Both indices contribute to more accurate long-term ecological assessments in hyper-arid environments. Full article

The desert riparian forest oasis, dominated by Populus euphratica and Tamarix chinensis, is an important barrier to protect the economic production and habitat of the Tarim River Basin. However, there is still a lack of high-precision spatial distribution data of desert ri-parian forest species below 10 m. The recently launched PlanetScope CubeSat constella-tion, which provides daily earth observation imagery with a resolution of 3 m, offers a highly favorable dataset for mapping the high-resolution distribution of P. euphratica and T. chinensis and an unprecedented opportunity to explore the optimal phenology window to distinguish between them. In this study, time-series PlanetScope images were first used to extract phenological metrics of P. euphratica, dividing the annual life cycle into four phenology windows: duration of leaf expansion (DLE), duration of leaf maturity (DLM), duration of leaf fall (DLF), and duration of the dormancy period (DDP). The random forest model was used to obtain the classification accuracy of 16 phenological window combinations. Results indicate that after gap filling of vegetation index time series, the identification accuracy for P. euphratica and T. chinensis exceeded 0.90. Among individual phenology windows, the DLE window exhibited the highest classification accuracy (average F1-score 0.87). Among the two phenology window combinations, the DLE-DLF and DLE-DLM windows have the highest classification accuracy (average F1-score 0.90). Among the three phenology window combinations, DLE-DLM-DLF displayed the highest classification accuracy (average F1-score 0.91). Nevertheless, the inclusion of features within the DDP window led to a decrease in accuracy by 1–2% points, which was unfavorable for discriminating tree species. Additionally, features observed during the phenology asynchrony period were found to be more valuable for distinguishing between tree species. Our findings highlight the potential of PlanetScope constellation imagery in tree species classification, offering guidance for selecting optimal image acquisition timing and identifying the most valuable images within time series data for future large-scale tree mapping. Full article

The lower reaches of the Tarim River in Xinjiang, China are home to desert riparian vegetation dominated by Populus euphratica, which play an important role in windbreak and sand fixation, as well as maintaining the ecological balance of arid regions. Based on dendrochronology, this study analyzed the response of Populus euphratica radial growth to hydrothermal factors in the lower Tarim River region, assessed its resistance and resilience to extreme drought events, developed a multivariate regression model for resilience–hydrothermal factor relationships, and revealed the differential response of its ecological resilience to these factors. The results showed that the maximum, minimum, and mean temperatures and saturated water VPD (vapor pressure deficit) during the spring and growing season were the most significant and positively correlated with Populus euphratica growth. The radial growth of Populus euphratica was negatively correlated with maximum and mean summer temperatures. By region, Yingsu (YS) and Kaerdayi (KE) were more sensitive to seasonal climatic factors. The effect of groundwater on the radial growth of Populus euphratica was the strongest factor, with a highly significant negative correlation (p < 0.01), showing that the radial growth of Populus euphratica slowed with increasing depth of groundwater. The VPD, spring drought severity, and growing season groundwater variability all had a significant effect on Populus euphratica resistance, whereas Populus euphratica resilience was mainly significantly associated with growing season drought severity and summer groundwater variability. Radial growth was positively correlated with spring temperatures and the VPD and negatively correlated with summer temperatures (p < 0.01). Full article

Desert plants in arid regions are facing escalating challenges from global warming, underscoring the urgent need to predict shifts in the distribution and habitats of dominant species under future climate scenarios. This study employed the Maximum Entropy (MaxEnt) model to project changes in the potential suitable habitats of three keystone desert species in Xinjiang—Halostachys capsica (M. Bieb.) C. A. Mey (Caryophyllales: Amaranthaceae), Haloxylon ammodendron (C. A. Mey.) Bunge (Caryophyllales: Amaranthaceae), and Karelinia caspia (Pall.) Less (Asterales: Asteraceae)—under varying climatic conditions. The area under the Receiver Operating Characteristic curve (AUC) exceeded 0.9 for all three species training datasets, indicating high predictive accuracy. Currently, Halos. caspica predominantly occupies mid-to-low elevation alluvial plains along the Tarim Basin and Tianshan Mountains, with a suitable area of 145.88 × 10⁴ km², while Halox. ammodendrum is primarily distributed across the Junggar Basin, Tarim Basin, and mid-elevation alluvial plains and aeolian landforms at the convergence zones of the Altai, Tianshan, and Kunlun Mountains, covering 109.55 × 10⁴ km². K. caspia thrives in mid-to-low elevation alluvial plains and low-elevation alluvial fans in the Tarim Basin, western Taklamakan Desert, and Junggar–Tianshan transition regions, with a suitable area of 95.75 × 10⁴ km². Among the key bioclimatic drivers, annual mean temperature was the most critical factor for Halos. caspica, precipitation of the coldest quarter for Halox. ammodendrum, and precipitation of the wettest month for K. caspia. Future projections revealed that under climate warming and increased humidity, suitable habitats for Halos. caspica would expand in all of the 2050s scenarios but decline by the 2070s, whereas Halox. ammodendrum habitats would decrease consistently across all scenarios over the next 40 years. In contrast, the suitable habitat area of K. caspia would remain nearly stable. These projections provide critical insights for formulating climate adaptation strategies to enhance soil–water conservation and sustainable desertification control in Xinjiang. Full article

Ecological risk refers to the potential threat that landscape changes pose to ecosystem structure, function, and service sustainability, while ecological security emphasizes the ability of regional ecosystems to maintain stability and support human well-being. Developing an Ecological Security Pattern (ESP) provides a strategic approach to balance ecological protection and sustainable development. This study investigates the spatial and temporal dynamics of landscape ecological risk in the Tarim Basin and surrounding urban areas in the Xinjiang Uygur Autonomous Region, China, from 2000 to 2020. Using a combination of the InVEST model, landscape connectivity index, and circuit theory-based modeling, we identify ecological source areas and simulate ecological corridors. Ecological source areas are categorized by their ecological value and connectivity: primary sources represent high ecological value and strong connectivity, secondary sources have moderate ecological significance, and tertiary sources are of relatively lower priority but still vital for regional integrity. The results show a temporal trend of ecological risk declining between 2000 and 2010, followed by a moderate increase from 2010 to 2020. High-risk zones are concentrated in the central Tarim Basin, reflecting intensified land-use pressures and weak ecological resilience. The delineated ecological protection zones include 61,702.9 km² of primary, 146,802.5 km² of secondary, and 36,141.2 km² of tertiary ecological source areas. In total, 95 ecological corridors (23 primary, 37 secondaries, and 35 tertiary) were identified, along with 48 pinch points and 56 barrier points that require priority attention for ecological restoration. Valuable areas refer to those with high ecological connectivity and service provision potential, while vulnerable areas are characterized by high ecological risk and landscape fragmentation. This study provides a comprehensive framework for constructing ESPs in arid inland basins and offers practical insights for ecological planning in desert–oasis environments. Full article

The Taklimakan Desert (TD), located in the Tarim Basin, and the Gobi Desert (GD), spanning northern China and southern Mongolia, are the two major dust source regions in East Asia, with substantial influence on China’s atmospheric environment and ecosystem. Using dust storm day (DSD) observations from national meteorological stations between 2000 and 2024, along with meteorological variables and the Normalized Difference Vegetation Index (NDVI), this study examines the spatiotemporal trends of dust storms and their key driving factors in both source regions. The TD and GD regions exhibit high levels of dust storm activity in China, with a distinct decreasing gradient from the source areas to downstream regions observed across all seasons. Trend analysis of DSD reveals distinct temporal patterns: the TD region experienced a moderate decline (−0.11 d/a) followed by a fluctuating increase (0.04 d/a), while the GD region exhibited a sharp drop (−0.32 d/a) and a subsequent marked resurgence (0.09 d/a). Seasonally, dust storm events in the TD region were frequent in both spring and summer, whereas in the GD region they were concentrated almost entirely in spring. In both source regions, spring dust storm events were closely linked to wind speed and the frequency of strong wind days. However, in summer, precipitation played a more suppressive role in the GD region, while wind remained the primary driver in the TD region. Between 2001 and 2013, both regions experienced a reduction in barren land area, aligning with a decline in dust storm events. In contrast, barren land in the GD region expanded from 2013 to 2023, accompanied by a significant increase in dust storm events. Notably, in the GD region, spring and summer NDVI values were negatively correlated with DSD, indicating stronger vegetation control over dust emission. In contrast, this relationship was weaker in the TD region, underscoring distinct ecological–meteorological interactions between the two desert systems. Full article

In order to cope with the ecological pressure caused by the uncontrolled expansion of cultivated land in arid areas and ensure regional food security, the implementation of a cultivated land fallowing system has become an effective way to restore the ecology, alleviate the pressure on cultivated land, and increase productivity. In view of this, this paper takes the Tarim River Basin, located in the arid zone of China’s agricultural continent, as the research object. Using a land use transfer matrix and a gravity center migration model, the paper analyzes the spatiotemporal characteristics of cultivated land expansion in the Tarim River Basin from 2000 to 2020. Through remote sensing and the integration of multi-source data, the paper constructs an arable land fallow urgency index (SILF) from multiple dimensions such as human activity intensity, ecological vulnerability, output value, water resources status, and terrain conditions. The research results show that (1) cultivated land in the Tarim River Basin expanded by 15,665.133 km² in general, which is manifested by spreading around based on existing cultivated land, mainly from the conversion of grassland and unused land; the center of gravity of cultivated land moved 37.833 km to the northeast and 7.257 km to the southwest first. (2) The area of not urgently fallow (NUF) in the watershed showed an overall downward trend, decreasing by 10%, while the area of very urgently fallow (VUF) increased by 16%. VUF is mainly distributed in the marginal areas of cultivated land close to the desert and is gradually expanding into the interior of cultivated land. (3) The overall ecological environment of cultivated land in the watershed is showing a deteriorating trend, and the deterioration is gradually spreading from the edge of the cultivated land to the interior. (4) There are significant differences in the SILF values of different land use types after conversion to cultivated land. The urgency of fallowing cultivated land converted from unused land is the highest, followed by grassland, forest land, water bodies, and construction land. The expanded cultivated land has a higher SILF value than the original cultivated land. The research results can provide insights into regional land resource management, the formulation of cultivated land protection policies, and the ecological restoration of cultivated land. Full article

Our understanding of water and salt changes in the context of declining groundwater levels in the Tarim Basin remains limited, largely due to the scarcity of hydrological monitoring stations and field observation data. This study utilizes water and salt monitoring data from 474 apparent electromagnetic induction (ECa, measured by EM38-MK2 device) sites across seven oases, combined with groundwater level observation data from representative areas, to analyze the spatiotemporal changes in ECa within the oases of the Tarim Basin from 2000 to 2022. Specific results are shown below: Numerous algorithmic predictions show the ensemble learning algorithm with the smallest error explained 71% of the ECa spatial variability. The ECa was particularly effective at identifying areas where groundwater extends beyond a depth of 5 m, demonstrating increased efficacy when ECa readings exceed the threshold of 1100 mS/m. Our spatiotemporal analysis spanning the years 2000 to 2022 has revealed a significant decline in ECa values within the artificially irrigated zones of the oasis clusters. In contrast, the transitional ecotone between the desert and the oases in Atux, Aksu, Kuqa, and Luntai have experienced a significant increase in ECa value. The variations observed within the defined Zone B, where ECa values ranged from 800 mS/m to 1100 mS/m, and Zone A, characterized by ECa values exceeding 1100 mS/m, aligned with the periodic fluctuations in the groundwater drought index (GDI), indicating a clear pattern of correlation. This study demonstrated that ECa can serve as a valuable tool for revealing the spatial and temporal variations of water resources in arid zones. The results obtained through this approach provided essential references for the local scientific management of soil and water resources. Full article

Plant functional traits are indicative of the long-term responses and adaptations of plants to their environment. However, the specific mechanisms by which desert plant functional groups (PFGs) adjust their ecological adaptation strategies to cope with harsh environments remain unclear, particularly in ecologically fragile farming–pastoral zones. To address this gap, this study investigates and analyzes the morphological and chemical characteristics of 13 desert plant species in the farming–pastoral zone of the northern Tarim Basin. Through cluster analysis, these desert plants were categorized into distinct PFGs to elucidate their ecological response strategies at a higher organizational level. The results were as follows: (1) Based on plant functional traits, the 13 desert plant species were classified into acquisitive, medium, and conservative PFGs. These groups exhibited significant differences in chemical element content and proportion, as well as morphological adjustments (p < 0.05). (2) The acquisitive functional group maintained high resource acquisition and turnover through high specific leaf area and leaf phosphorus content; the medium functional group occupied limited resources through greater plant height and canopy width, whereas the conservative functional group exhibited low growth rates but high morphological investment to ensure survival. Moreover, these differences in ecological adaptation strategies led to the selection of divergent central traits by different PFGs. (3) Low soil nutrient availability and soil salinization, rather than groundwater depth, were identified as the primary environmental factors driving the differentiation of PFGs in the farming–pastoral zone. These findings suggest that desert plants in arid regions employ diverse ecological adaptation strategies to cope with environmental pressures. This research study provides valuable insights and recommendations for the conservation and restoration of desert plant communities. Full article

To explain one of the reasons why two adjacent deep-rooted desert plants can coexist over long periods, mutual water supply between species was investigated. The study focused on δD and δ¹⁸O stable isotopic characteristics of root water and soil water near the roots of Tamarix ramosissima Ledeb. and Alhagi sparsifolia Shap. in the Tarim River Basin in China during the growing season. The direct comparison method and the Mix SIAR model were employed to analyze the water sources of the plants and the contribution rates of each water source. A similarity proportional index was used to assess the hydraulic connections between plant species. The water sources of T. ramosissima and A. sparsifolia were soil water found at depths of 40 to 90 cm and 220 to 300 cm (a total contribution rate of 58.85%) and 130 to 190 and 240 to 300 cm (a total contribution rate of 81.35%) with groundwater depths of 2.5 to 3.0 m, respectively. When the groundwater depth increased to 4 m, the water sources for both T. ramosissima and A. sparsifolia were soil water at depths of 20 to 100 (a contribution rate of 70.60%) and 20 to 120 cm (a contribution rate of 49.60%), respectively. Both A. sparsifolia and T. ramosissima could lift water from deep soil or groundwater for their own growth needs and supply some water to each other, which suggests that desert plants were allowed to achieve mutual benefits and coexistence through hydraulic connections. These results enrich the theoretical understanding of desert plant coexistence and provide a scientific basis for desert vegetation restoration. Full article

The phenological characteristics of plants can reflect both their responses to environmental changes as well as an ecosystem’s sensitivity to climate change. Although there have been several phenological studies of plant species worldwide, there is minimal research on the phenology of vegetation found in extremely arid environments within the context of climate change. To address this research gap, this study investigated the effects of climate–hydrological factors, including temperature, precipitation, surface temperature, and surface humidity, on the phenological characteristics (start of the growing season [SOS] and end of the growing season [EOS]) of Populus euphratica in the Tarim Desert Oasis. Using Landsat 7/8 satellite imagery and field data, we analyzed the spatial and temporal variations in the SOS and EOS from 2004 to 2023. The availability of water, particularly changes in groundwater depth and surface water, directly played a key role in shaping the spatial distribution and temporal dynamics of P. euphratica phenology. The impact of increasing temperatures on P. euphratica phenology varied under different moisture conditions: in high-moisture environments, increased temperatures promoted earlier SOS and delayed EOS, with the opposite conditions occurring in low-moisture environments. This study highlights the profound influence of moisture conditions on P. euphratica phenology in the context of climate change, especially in extreme arid regions. To accurately predict the response of P. euphratica phenology to climate change, future ecological models should incorporate hydrological factors, particularly changes in soil moisture, in cold and dry regions. These findings provide important insights for developing effective ecological protection and management strategies. Full article

The Populus euphratica desert riparian forest, predominantly distributed along the Tarim River in northwestern China, has experienced significant degradation due to climate change and anthropogenic activities. Despite its ecological importance, systematic assessments of P. euphratica stand structure across the entire Tarim River remain scarce. This study employed terrestrial laser scanning (TLS) to capture high-resolution 3D structural data from 2741 individual trees across 30 plots within six transects, covering the 1300 km mainstream of the Tarim River. ANOVA, PCA, and RDA were applied to examine tree structure variation and environmental influences. Results revealed a progressive decline in key structural parameters from the upper to lower reaches of the river, with the lower reaches showing pronounced degradation. Stand density decreased from 440 to 257 trees per hectare, mean stand height declined from 9.3 m to 5.6 m, mean crown diameter reduced from 4.1 m to 3.8 m, canopy cover dropped from 62% to 42%, and the leaf area index fell from 0.51 to 0.29. Age class distributions varied along the river, highlighting population structures indicative of growth in the upper reaches, stability in the middle reaches, and decline in the lower reaches. Abiotic factors, including groundwater depth, soil salinity, soil moisture, and precipitation, exhibited strong correlations with stand structural parameters (p < 0.05, R² ≥ 0.69). The findings highlight significant spatial variations in tree structure, with healthier growth in the upper reaches and degradation in the lower reaches, enhance our understanding of forest development processes, and emphasize the urgent need for targeted conservation strategies. This comprehensive quantification of P. euphratica stand structure and its environmental drivers offer valuable insights into the dynamics of desert riparian forest ecosystems. The findings contribute to understanding forest development processes and provide a scientific basis for formulating effective conservation strategies to sustain these vital desert ecosystems, as well as for the monitoring of regional environmental changes. Full article

Populus euphratica is the only dominant tree species of desert riparian forest in the Tarim River Basin and faces a great threat of drought. Policy-based artificial water delivery projects are an effective engineering method to mitigate drought and reduce the degradation of desert riparian forests. Forest gaps have been shown to be the primary mode of forest regeneration. However, little is known about growth status of P. euphratica in various arid zone habitats, particularly in light of the complex and diverse microenvironmental alterations in the understory. This study quantified the effects of forest gaps and flooded areas on microenvironmental changes in the understory. The relationships between the microenvironmental changes, soil physicochemical properties, and physiological characteristics of P. euphratica were investigated through a cross-experiment that compared whether the water delivery process was flooded and whether forest gaps existed. The results revealed that the forest gap increased the diversity of light conditions on the ground; floods decreased the temperature of the forest gap by 1.94 °C while they increased the air humidity by 8.19%. Flooding improved the vertical distribution of soil physicochemical properties within the forest gap while also altering the content of soil indicators in different directions. In the research area, only the peroxidase activity (POD) exhibited significant differences (p < 0.05) in drought indicators between the forest gaps and understory of P. euphratica, while all of the drought indicators improved after flooding. Changes in the microenvironments and soil physicochemical features together play an important ecological role in mitigating the drought of P. euphratica. These results provide an actionable theoretical basis for the efficient management of riparian forests and a research basis for sustainable forest development in arid zones. Full article