Search Results (93)

Populus euphratica (P. euphratica) is a dominant tree species in the arid and semi-arid regions along the main stem of the Tarim River. This study aims to explore the response of microbial communities in the rhizosphere soil of P. euphratica to varying groundwater depths (GWD) and to elucidate the ecological functions of key microbial groups in drought resistance. We established three groundwater depth levels (3.8 m, 5.4 m, and 7.35 m) and employed metagenomic sequencing technology to systematically analyze the topological characteristics of functional microbial community networks, as well as the types and quantities of key microbial groups in the rhizosphere soil of P. euphratica under different GWD conditions. The results indicate that compared to GWDs of 3.8 m and 7.35 m, the average degree and graph density of microbial communities in the rhizosphere soil of P. euphratica at a depth of 5.4 m are the highest. This suggests that at a GWD of 5.4 m, the connectivity and stability of the microbial network structure in the rhizosphere soil of P. euphratica are significantly enhanced. Analysis of the Zi-Pi values within the microbial network structure reveals that, compared to GWDs of 3.8 m and 7.35 m, a depth of 5.4 m supports the greatest variety and quantity of key microbial species in the rhizosphere soil of P. euphratica. The four connecting nodes identified are Actinophytocola, Haladaptatus, Devosia and Pseudonocardia. Spearman correlation analysis demonstrates that the relative abundance of the key bacterial genus Mesorhizobium in the rhizosphere soil of P. euphratica at different GWD is significantly positively correlated with soil catalase (CAT) and urease (UE) activity. Furthermore, the relative abundance of the key bacterial genus Pseudonocardia shows a significant positive correlation with soil total nitrogen (TN) and ammonium nitrogen (NH₄⁺-N) (p < 0.05). The relative abundance of the key bacterial genus Devosia exhibits a highly significant positive correlation with soil water content (SWC) (p < 0.01) and a significant negative correlation with soil NH₄⁺-N (p < 0.05). Additionally, the relative abundance of Devosia is significantly positively correlated with soil CAT (p < 0.05). This study provides a theoretical foundation for the conservation of desert poplar forests in arid regions and for the identification and cultivation of specific key microbial communities in the rhizosphere soil of P. euphratica. Full article

Understanding seasonal water acquisition strategies of desert plants is critical for predicting vegetation resilience under increasing hydrological stress in arid inland river basins. In hyper-arid oases, strong evaporative demand and declining groundwater levels impose tightly coupled constraints on plant water uptake across soil–plant–atmosphere continua. In this study, we combined hydrogen and oxygen stable isotopes, Bayesian mixing models, soil moisture measurements and groundwater monitoring, and leaf δ¹³C analysis to quantify monthly water-source contributions and long-term water-use efficiency of three dominant species (Reaumuria soongarica, Tamarix ramosissima, and Populus euphratica) in the Ejina Oasis. Clear ecohydrological niche differentiation was evident among the three species. R. soongarica exhibited moderate temporal flexibility by integrating shallow and deep soil water with episodic groundwater use, whereas T. ramosissima adopted a vertically integrated and hydraulically plastic strategy combining precipitation, multi-depth soil water, and groundwater. In contrast, P. euphratica followed a conservative strategy, relying predominantly on deep soil water with only minor and transient inputs from precipitation and groundwater. Across species and seasons, deep vadose-zone soil water (120–200 cm) consistently acted as the most stable and influential reservoir, buffering seasonal drought and sustaining transpiration. T. ramosissima maintained the highest intrinsic water-use efficiency, and P. euphratica exhibited consistently lower efficiency associated with sustained access to stable deep soil water. These contrasting strategies reveal multiple pathways of hydraulic stability and plasticity that underpin vegetation persistence under progressive groundwater depletion. By linking water-source partitioning with physiological regulation, this study provides a mechanistic basis for understanding plant water-use strategies and informs ecological water management and species-specific restoration in hyper-arid inland oases. Full article

Auxin plays a crucial role in plant growth and development via concentration gradient regulation, with auxin response factors (ARFs) as key transcription factors in its signalling pathway. However, comprehensive identification and characterisation of ARF genes in Salicaceae remain limited. This study performed a genome-wide analysis of ARF genes in three Salicaceae species (Populus euphratica Oliv., Populus pruinosa, and Salix sinopurpurea), aiming to clarify their physicochemical properties, evolutionary relationships, and functional relevance. A total of 34 ARF genes were identified in each species, all being nucleus-localised hydrophilic unstable proteins clustered into six phylogenetic subgroups. Their promoters contain numerous cis-acting elements responsive to light, phytohormones, and stresses. Transcriptome and qRT-PCR data showed significant up-regulation of PeARF18 in ovate/broad-ovate leaves of P. euphratica compared to linear/lanceolate leaves. This study provides preliminary insights into the characterisation and potential role of the Salicaceae ARF gene family, laying a foundation for further functional exploration of PeARF18 in P. euphratica leaf shape development. Full article

Populus euphratica Oliv. serves as a keystone species in desert riparian ecosystems. Owing to its pronounced tolerance to drought and salinity, as well as its robust reproductive capacity, it has become a pioneer species in desert oases. The xyloglucan endotransglucosylase (XET)/hydrolase (XTH) gene family plays a critical role in the remodeling of plant cell walls; however, its potential biological functions in poplar remain poorly understood. In this study, we identified the XTH gene family in P. euphratica and conducted a preliminary functional analysis. A total of 33 PeXTH genes were identified, which were unevenly distributed across the chromosomes, with the highest density observed on chromosome 6. Conserved domain analysis indicated that most members contain the typical GH16 domain associated with xyloglucan endotransglucosylase activity. Phylogenetic analysis classified them into four distinct subgroups, exhibiting evolutionary conservation with the model dicot plant of Arabidopsis thaliana. Notably, the promoter analysis revealed an abundance of ABA-responsive and stress-related cis-elements, suggesting their potential involvement in response to multiple stresses. Under drought stress, PeXTH7 (PeuTF07G00088.1) exhibited a distinct expression pattern, with transcript levels significantly increasing with persistent treatment. RT-qPCR results confirmed that PeXTH7 is highly expressed in both roots and leaves. Furthermore, subcellular localization assays demonstrated that the PeXTH7 protein localizes to the secretory pathway and the cell wall, implying a role in cell wall dynamic remodeling through the regulation of xyloglucan metabolism. The PeXTH7-overexpressing transgenic lines exhibited a significant increase in root length compared to the wild-type controls. As the first systematic analysis of the XTH gene family in P. euphratica, this study fills an important knowledge gap and provides new insights into the adaptive mechanisms of desert tree species. Full article

Plant interactions and their responses to stress environments are important ecological processes for ecosystem stability and biodiversity formation, but how plant intraspecific relationships respond to environmental stresses remains to be studied in depth. In this study, annual Populus euphratica seedlings were planted in singles or doubles, and two stress treatments were set up: two drought levels (0.7 and 0.4 L) and two salinity levels (200 and 400 mmol L⁻¹). P. euphratica seedlings’ total and part biomass, root/shoot ratio, net photosynthetic rate, stomatal conductance, nonstructural carbohydrate concentration, and proline content were measured. Relative interaction indices were calculated to clarify their intraspecific relationships. The results of the study showed that compared to the single-planted P. euphratica, the double-planted P. euphratica was more significantly inhibited by drought and salt stress, the total biomass decreased, photosynthesis declined, proline content increased, and non-structural carbohydrates changed, which reflected a competitive intraspecific relationship. Secondly, as drought and salt stress intensified, the relative interaction index indicated that the intraspecific relationship of P. euphratica seedlings gradually shifted from neutrality to competition, which indicated that the intraspecific competitive relationship of P. euphratica seedlings was exacerbated by environmental stresses. These findings highlight the need to account for stress-mediated competition in P. euphratica seedlings during ecological restoration in arid environments. Full article

Individual tree segmentation (ITS) is essential for forest inventory, health assessment, carbon accounting, and evaluating restoration efforts. Populus euphratica, a widely distributed desert riparian tree species found along the inland rivers of Central Asia, presents challenges for accurately identifying individual trees and conducting forest inventories due to its complex stand structure and overlapping crowns. To determine the most effective ITS approach for P. euphratica, we benchmarked six commonly used tree segmentation approaches for terrestrial laser scanning (TLS) data: canopy height model segmentation (CHMS), point cloud segmentation (PCS), comparative shortest-path algorithm (CSP), stem location seed point segmentation (SPS), deep-learning trunk-based segmentation (TBS), and leaf–wood separation-based segmentation (LWS). All methods followed a unified preprocessing and tuning protocol. We evaluated these methods based on tree-count accuracy, crown delineation, and structural attributes such as tree height (H), diameter at breast height (DBH), and crown diameter (CD). The results indicated that the TBS and LWS methods performed the best, achieving a mean tree-count accuracy of 98%, while the CHMS method averaged only 46%. These two methods provide the basic branch structure within the tree crown, reducing the likelihood of incorrect segmentation. Validation against field-measured values for H, DBH, and CD showed that both the TBS and LWS methods achieved accuracies exceeding 80% (RMSE = 0.8 m), 86% (RMSE = 0.02 m), and 73% (RMSE = 0.7 m), respectively. For TLS data in P. euphratica desert riparian forests, these two methods provide the most reliable results, facilitating rapid plot-scale inventory and monitoring. These findings establish a practical basis for conducting high-accuracy inventories of Euphrates poplar desert riparian forests. Full article

This study examined the windbreak effects of different tree–shrub configurations through wind tunnel experiments. Using Populus euphratica Oliv. and Tamarix chinensis Lour. as model species, six rows of front-tree–back-shrub arrangements in a triangular layout were tested under varying spacing patterns. Four spacings of P e (7.5 cm × 7.5 cm, 7.5 cm × 10 cm, 7.5 cm × 12.5 cm, 10 cm × 10 cm) and four spacings of T cs (5 cm × 5 cm, 5 cm × 7.5 cm, 5 cm × 10 cm, 7.5 cm × 7.5 cm) were analyzed. Tree–shrub combinations significantly outperformed pure stands. The configuration of P e (7.5 cm × 10 cm) with T c (5 cm × 10 cm) achieved the highest efficiency, with an average of 27.1% and a peak of 47.13% at 7 H. This configuration was effective up to 15 H and showed slower efficiency decline at higher wind speeds. Vertically, most combinations reached maximum efficiency at 20 cm height, while pure T c peaked at 51.96% at 3 cm and pure P e at 36.33% at 20 cm. Overall, the optimal configuration was P e spaced at 7.5 cm × 10 cm and T c at 5 cm × 10 cm, which not only enhanced protective performance but also reduced planting density. These findings provide valuable scientific references for designing windbreak and sand-fixing forests in arid regions, supporting ecological restoration and sustainable land management in desert–oasis transition zones. Full article

Improving plant water use efficiency (WUE) and drought tolerance by modulating stomatal activity constitutes a promising strategy for mitigating the impacts of water scarcity. SnRK2, a key component of the abscisic acid (ABA) signaling pathway, plays a critical role in modulating stomatal behavior under abiotic stress. However, the functional role of SnRK2 in regulating stomatal movement to enhance WUE and drought tolerance in Populus euphratica remains to be characterized. In this study, 11 PeSnRK2 genes were identified in the P. euphratica genome, each comprising 9–14 exons and exhibiting an uneven distribution across seven chromosomes. Subcellular localization predictions indicated that these proteins are predominantly localized in the Cytoplasm and Cytoskeleton. Phylogenetic analysis grouped the PeSnRK2 genes into three distinct subfamilies, and conserved gene structures were observed within each clade. Analysis of cis-acting regulatory elements suggested that PeSnRK2 genes were involved in hormonal signaling and stress response pathways. Further transcriptomic data also indicated substantial alterations in PeSnRK2 expression due to polyethylene glycol (PEG) and abscisic acid (ABA) treatment. Finally, qRT-PCR and subcellular localization showed that PeSnRK2.6 is highly induced by ABA and functions in both nucleus and cytoplasm. This first characterization in a desert woody species bridged gaps in SnRK2 evolution and function. 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

Understanding heavy metal behavior in arid saline soils is critical for phytoremediation in degraded lands. This study investigated metal distribution and plant enrichment in the Tarim Basin using 323 soil and 55 plant samples (Populus euphratica, Tamarix ramosissima, cotton, jujube). Analyses included redundancy analysis (RDA) and bioconcentration factor (BCF) assessments. Key findings reveal that elevated salinity (total salts, TS > 200 g/kg) and alkalinity (pH > 8.5) immobilized As, Cd, Cu, and Zn. Precipitation and competitive leaching reduced metal mobility by 42–68%. Plant enrichment strategies diverged significantly: P. euphratica hyperaccumulated Cd (BCF = 1.59) and Zn (BCF = 2.41), while T. ramosissima accumulated As and Pb (BCF > 0.05). Conversely, cotton posed Hg transfer risks (BCF = 2.15), and jujube approached Cd safety thresholds in phosphorus-rich soils. RDA indicated that pH and total salinity (TS) jointly suppressed metal bioavailability, explaining 57.6% of variance. Total phosphorus (TP) and soil organic carbon (SOC) enhanced metal availability (36.8% variance), with notable TP-Cd synergy (Pearson’s r = 0.42). We propose a dual-threshold management framework: (1) leveraging salinity–alkalinity suppression (TS > 200 g/kg + pH > 8.5) for natural immobilization; and (2) implementing TP control (TP > 0.8 g/kg) to mitigate crop Cd risks. P. euphratica demonstrates targeted phytoremediation potential for degraded saline agricultural systems. This framework guides practical management by spatially delineating zones for natural immobilization versus targeted remediation (e.g., P. euphratica planting in Cd/Zn hotspots) and implementing phosphorus control in high-risk croplands. Full article

Dry seed longevity varies considerably among species, but little is known about its relation with the climate and the molecular mechanisms that determine seed lifespan. Salicaceae species, with more than 620 species worldwide, are known to produce short-lived seeds, making them particularly good models to explore ageing processes in the glassy state rather than under accelerated ageing. We compared seed lifespan for 13 species of Salix and Populus across a broad geographical range (up to 2200 m a.s.l.). High-quality seeds were obtained by optimizing collection time (just before capsule dehiscence) and post-harvest handling (i.e., the use of negative pressure to remove seed hairs). At optimal moisture contents (MCs) between 6 and 9%, most species seeds demonstrated minimal decreases in viability after storage at −20 °C or in liquid nitrogen for 3 years. Dry room (15% RH, 15 °C) storage differentiated between species’ seed lifespans (P₅₀s) of c. 150 to >1200 d. Unlike Salix, Populus species from warm wet environments tended to produce longer-lived seeds in dry storage. Based on transcriptome data on Populus davidiana (longer-lived) and Populus euphratica (shorter-lived), we revealed high correlations between late seed maturation genes, such as 60% of HSP and 67% of LEA genes showed higher expression in P. davidiana seeds, while 70% of WRKY transcription factors showed significantly higher expression in P. euphratica seeds. For these two species, genes related to oxidative stress might be the most important contributor to different seed longevity in the dry glassy state. Full article

Climate change significantly alters vegetation distribution patterns in arid regions, while ecological water conveyance serves as a critical intervention to modify these patterns by augmenting water availability. As a keystone species in Central Asia’s water-stressed ecosystems, Populus euphratica plays a pivotal role in maintaining arid ecosystem stability, making the investigation of its habitat suitability under combined climate change and ecological water conveyance imperative. This study selected 12 variables associated with the spatial distribution of P. euphratica, including bioclimate, groundwater resources, available water storage capacity, elevation, distance to rivers, and stocking rate. Using the maximum entropy (MaxEnt) model, we projected habitat distributions of P. euphratica across the Tarim River Basin with three scenarios: no climate change, climate change, and ecological water conveyance. The study indicated that (1) distance to rivers has the significant effect on the distribution of P. euphratica; (2) although climate change is expected to reduce the habitat suitable for P. euphratica, the implementation of ecological water conveyance is expected to lead to an expansion of its habitat; (3) the implementation of ecological water conveyance is expected to cause the habitat suitable for P. euphratica to shift toward the southeast, suggesting that this initiative has increased groundwater resources in the southeastern part of the watershed. These findings provide a scientific foundation for protecting P. euphratica and formulating effective ecological water conveyance strategies. Full article

Abscisic acid (ABA) is a key phytohormone involved in regulating plant growth and responses to environmental stress. As receptors of ABA, pyrabactin resistance 1 (PYR)/PYR1-like (PYL) proteins play a central role in initiating ABA signal transduction. In this study, a total of 30 PopPYL genes were identified and classified into three sub-families (PYL I–III) in the pan-genome of 17 Populus species, through phylogenetic analysis. Among these subfamilies, the PYL I subfamily was the largest, comprising 21 members, whereas PYL III was the smallest, with only four members. To elucidate the evolutionary dynamics of these genes, we conducted synteny and Ka/Ks analyses. Results indicated that most PopPYL genes had undergone purifying selection (Ka/Ks < 1), while a few were subject to positive selection (Ka/Ks > 1). Promoter analysis revealed 258 cis-regulatory elements in the PYL genes of Populus euphratica (EUP) and Populus pruinosa (PRU), including 127 elements responsive to abiotic stress and 33 ABA-related elements. Furthermore, six structural variations (SVs) were detected in PYL_EUP genes and significantly influenced gene expression levels (p < 0.05). To further explore the functional roles of PYL genes, we analyzed tissue-specific expression profiles of 17 PYL_EUP genes under drought stress conditions. PYL6_EUP was predominantly expressed in roots, PYL17_EUP exhibited leaf-specific expression, and PYL1_EUP showed elevated expression in stems. These findings suggest that the drought response of PYL_EUP genes is tissue-specific. Overall, this study highlights the utility of pan-genomics in elucidating gene family evolution and suggests that PYL_EUP genes contribute to the regulation of drought stress responses in EUP, offering valuable genetic resources for functional characterization of PYL genes. 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

DNA methylation, mediated by DNA methyltransferases (DMTs) and demethylases (DMLs), is an important epigenetic modification that maintains genomic stability and regulates gene expression in plant growth, development, and stress responses. However, a comprehensive characterization of these gene families in Populus sect. Turanga remains lacking. In this study, eight PeDMT and two PeDML genes were identified in Populus euphratica, and six PpDMT and three PpDML genes in Populus pruinosa. Phylogenetic analysis revealed that DMTs and DMLs could be classified into four and three subfamilies, respectively. The analysis of cis-acting elements indicated that the promoter regions of both DMTs and DMLs were enriched with elements responsive to growth and development, light, phytohormones, and stress. Collinearity analysis detected three segmentally duplicated gene pairs (PeDMT5/8, PeDML1/2, and PpDML2/3), suggesting potential functional diversification. Transcriptome profiling showed that several PeDMTs and PeDMLs exhibited leaf shape- and developmental stage-specific expression patterns, with PeDML1 highly expressed during early stages and in broad-ovate leaves. Whole-genome bisulfite sequencing revealed corresponding decreases in DNA methylation levels, suggesting that active demethylation may contribute to heteromorphic leaf formation. Overall, this study provides significant insights for exploring the functions and expression regulation of plant DMTs and DMLs and will contribute to future research unraveling the molecular mechanisms of epigenetic regulation in P. euphratica. Full article