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Leaf water content (LWC) encapsulates critical aspects of tree physiology and is considered a proxy for assessing tree drought stress and the risk of forest decline; however, its measurement relies on destructive sampling and is thus less efficient. Advancements in hyperspectral imaging technology present new prospects for noninvasively evaluating LWC and mapping drought severity across forested regions. In this study, leaf samples were obtained from Populus alba var. pyramidalis, a species widely employed for constructing farmland shelterbelts in water-limited regions of northern China but notably susceptible to drought. These samples were dehydrated to varying degrees to generate concurrent LWC measurements and hyperspectral images, enabling the development of narrow-band and multivariate spectral prediction models for LWC estimation. Two visible-spectrum narrow-band indices identified, the single-band index (R627) and the band subtraction index (R437 − R444), demonstrated a strong correlation with LWC. Despite certain influences of variable preprocessing and selection on multivariate model performance, most models exhibited robust predictive accuracy for LWC. The FDRL-UVE-PLSR combination emerged as the optimal multivariate model, with R2 values reaching 0.9925 and 0.9853 and RMSE values below 0.0124 and 0.0264 for the calibration and validation datasets, respectively. Using this optimal model, along with localized spectral smoothing, moisture distribution across leaf surfaces was visualized, revealing lower water retention at the leaf margins compared to central regions. These methodologies provide critical insights into subtle water-associated physiological processes at the leaf scale and facilitate high-frequency, large-scale assessments and monitoring of drought stress levels and the risk of drought-induced tree mortality and forest degradation in drylands. [ABSTRACT FROM AUTHOR]

Crown removal revitalises sand‐fixing shrubs that show declining vigour with age in drought‐prone environments; however, the underlying mechanisms are poorly understood. Here, we addressed this knowledge gap by comparing the growth performance, xylem hydraulics and plant carbon economy across different plant ages (10, 21 and 33 years) and treatments (control and crown removal) using a representative sand‐fixing shrub (Caragana microphylla Lam.) in northern China. We found that growth decline with plant age was accompanied by simultaneous decreases in soil moisture, plant hydraulic efficiency and photosynthetic capacity, suggesting that these interconnected changes in plant water relations and carbon economy were responsible for this decline. Following crown removal, quick resprouting, involving remobilisation of root nonstructural carbohydrate reserves, contributed to the reconstruction of an efficient hydraulic system and improved plant carbon status, but this became less effective in older shrubs. These age‐dependent effects of carbon economy and hydraulics on plant growth vigour provide a mechanistic explanation for the age‐related decline and revitalisation of sand‐fixing shrubs. This understanding is crucial for the development of suitable management strategies for shrub plantations constructed with species having the resprouting ability and contributes to the sustainability of ecological restoration projects in water‐limited sandy lands. Summary statement: Embolism accumulation restricted carbon assimilation in aging shrubs and resulted in growth decline, while the crown‐removal treatment revitalised plants by promoting the construction of new hydraulic systems in resprouts and enhancing carbon balance through the removal of dysfunctional old stems. [ABSTRACT FROM AUTHOR]

This document discusses the challenges faced by plants in arid and semi-arid regions due to harsh environmental conditions such as limited rainfall, high temperatures, and poor soil nutrition. The document highlights the importance of understanding plant adaptation strategies to extreme environments in order to protect and manage local vegetation and ecosystems. The document presents research papers that cover various aspects of plant adaptation in arid regions, including water uptake mechanisms, physiological and biochemical adaptations, plant-soil microbial interactions, and ecosystem services. The research findings provide insights into how plants in arid regions adapt to environmental changes and maintain ecological balance. However, further research is needed to fully understand the processes and mechanisms of plant adaptation in extreme environments. [Extracted from the article]

Luo and Gong [[9]] investigated the diversity of desert shrub communities and evaluated the relationship between species diversity indexes and key climatic variables across 29 sites in Xinjiang, northwestern China. Liu et al. [[11]] explored the scale effects of the biodiversity-ecosystem multifunctionality relationship of representative desert plant communities in the southern margin of the Taklimakan Desert. Arid and semi-arid lands cover more than one-third of the earth's terrestrial area and are typically characterized by rainfall scarcity, higher temperatures and evapotranspiration, salinization, nutrient-poor soil, and a paucity of vegetation cover. [Extracted from the article]

Aims: Sand-fixing shrub Salix gordejevii plays an important role in sand dune stabilization but often shows severe decline and mortality on the windward slopes of active dunes. The objective of this study was to explore the environmental drivers and physiological mechanisms behind its decline and mortality on the windward slopes of active sand dunes. Methods: The xylem hydraulics, sap flow, water relations and non-structural carbohydrate reserves were measured for S. gordejevii plants that respectively inhabited interdune, leeward and windward positions of active dunes with contrasting soil water regimes. Results: Root exposure caused by wind erosion, rather than low soil moisture, predisposed windward S. gordejevii plants to stronger water stress. Correspondingly, the windward plants showed reduced transpirational water use and exhibited a suite of acclimative adjustments in leaf traits favoring water conservation. Despite these adjustments, windward S. gordejevii plants still suffered from higher risks of hydraulic failure and branch mortality. No evidence of carbon depletion in windward S. gordejevii plants was found although the soluble sugar to starch ratios changed significantly. Conclusions: Our findings suggest that wind-erosion-induced root exposure triggers water stress and eventually causes the mortality of windward S. gordejevii plants, during which increased risk of hydraulic dysfunction is pronounced. [ABSTRACT FROM AUTHOR]

Differences in key physiological characteristics between plant species can result in their contrasting performances in vegetation restoration projects, but ecophysiological comparative studies in close relation to ecological restoration projects are scarce. Hedysarum fruticosum Pall. and Caragana microphylla Lam. are two leguminous shrub species widely used in combination for fixation of active sand dunes in semiarid regions of northern China, but they clearly differ in fitness at different stages of dune vegetation development; that is, H. fruticosum quickly gains a community dominance at the initial stage but yields to C. microphylla in a few years after the fixation of dunes. To reveal the underlying mechanism of such a pattern, key physiological characteristics related to xylem water transport, leaf water use, and drought tolerance were compared between these two species at a typical site of sand dune fixation project in Inner Mongolia. Compared with C. microphylla, H. fruticosum shows an acquisitive and risky water management strategy with substantially higher hydraulic efficiency and photosynthetic capability but reduced resistance to drought‐induced xylem embolism, which endows it an advantage under conditions of relatively high soil water availability at the early stage of dune fixation. In contrast, C. microphylla exhibits more conservative water use and characteristics of greater drought tolerance, which results in greater dominance under the more drought‐stressed conditions of the later stage of dune fixation. Our study for the first time provides a potential mechanistic explanation for the clear switching of dominant positions between the two important sand‐fixing shrub species during the sand dune revegetation process. [ABSTRACT FROM AUTHOR]

Atmospheric water is one of the main water resources for plants in arid ecosystems. However, whether deep-rooted, tomentum-less desert trees can absorb atmospheric water via aerial organs and transport the water into their bodies remains poorly understood. In the present study, a woody, deep-rooted, tomentum-less plant, Haloxylon ammodendron (C.A. Mey.) Bunge, was selected as the experimental object to investigate the preconditions for and consequences of foliar water uptake. Plant water status, gas exchange, and 18O isotopic signatures of the plant were investigated following a typical rainfall pulse and a high-humidity exposure experiment. The results showed that a high content of atmospheric water was the prerequisite for foliar water uptake by H. ammodendron in the arid desert region. After atmospheric water was absorbed via the assimilating branches, which perform the function of leaves due to leaf degeneration, the plant transported the water to the secondary branches and trunk stems, but not to the taproot xylem or the soil, based on the 18O isotopic signatures of the specimen. Foliar water uptake altered the plant water status and gas exchange-related traits, i.e., water potential, stomatal conductance, transpiration rate, and instantaneous water use efficiency. Our results suggest that atmospheric water might be a subsidiary water resource for sustaining the survival and growth of deep-rooted plants in arid desert regions. These findings contribute to the knowledge of plant water physiology and restoration of desert plants in the arid regions of the planet. [ABSTRACT FROM AUTHOR]

In an arid region, water is the limiting factor for the performance of plants and, hence, the input of water significantly affects the ecological processes. Although the dew phenomenon often occurs in the desert, whether plants can absorb and utilise this water source is still unknown. In this study, we tested the effects of 3 amounts of dew, that is, total natural amount of dew, half amount of natural dew, and no amount of (zero) dew, in order to investigate variations in functional traits and demographic traits in relation to the life history of an ephemeral plant Lappula semiglabra. Results showed that variations in functional traits including plant height, crown area, leaf area, leaf thickness, leaf relative water content, chlorophyll content, and net photosynthetic rate were significantly increased with increasing dew amount. Leaf water potential was significantly decreased, whereas root length and root diameter showed no significant differences among 3 amounts of dew. Demographic traits including survival rate, survival, total age, and mean life expectancy increased with increasing dew amount, whereas the vanish rate percentage, mortality rate, mortality, and fatal number decreased. In combination, our results showed that leaf and stem traits L. semiglabra related to dew absorption increased with increasing of dew amount, and hence, obtained more water, whereas root traits related to uptake of soil water remain unchanged. We conclude that leaves and stem of L. semiglabra can absorb and efficiently utilise dew as a water resource for better suitability in the arid desert region. [ABSTRACT FROM AUTHOR]