Haloxylon Ammodendron Research Articles

Effects of Stumping and Meteorological Factors on Sap Flow Characteristics of Haloxylon ammodendron in Ulan Buh Desert, Northwestern China

The shrub/dwarf tree Haloxylon ammodendron is a prevalent woody plant used to combat desertification in the arid and semi-arid regions of northwestern China. Despite its drought resistance, artificial stands of this species experience significant degradation approximately ten years post-afforestation. Stumping, which involves cutting a portion of the above-ground part of shrubs/trees, is a common practice aimed at reducing water consumption and enhancing the growth of these stands. However, the impact of stumping on the sap flow of H. ammodendron remain inadequately understood, posing challenges to the sustainable management of these artificial stands. In this study, we monitored the sap flow of H. ammodendron subjected to various stumping treatments in the Ulan Buh Desert using the PS-TDP8 tree sap flow monitoring system. Concurrently, we measured several meteorological factors with an automatic weather station. We examined the changes in sap flow velocity following stumping and its response to meteorological factors to elucidate water use during growth. Our findings indicate that both the change in sap flow velocity and characteristics were closely associated with the degree of stumping. The initiation time of sap flow for H. ammodendron under different stumping treatments was earlier than that of the control group. The daily mean value and daily accumulation of sap flow followed the order: 50% stumping > control (no stumping) > 75% stumping > 100% stumping. Sap flow velocity and daily sap flow accumulation increased at 50% stumping but decreased at 75% and 100% stumping. Stumping altered the relationships between sap flow velocity and meteorological factors, with the correlation coefficient between these variables decreasing as the degree of stumping increased. The sap flow following stumping was primarily influenced by both the degree of stumping and meteorological factors. These results may contribute to a better understanding of water transport during the growth of H. ammodendron following stumping.

Effects of Restoration Strategies on Soil Health after Lycium chinense Removal in the Qaidam Basin

Ecological restoration of arid land plays a pivotal role in maintaining ecological sustainability and enhancing the resilience of local communities. As an ecologically significant arid land, the Qinghai Qaidam Basin has been severely impacted by human activities such as the widespread planting of Lycium chinense, leading to considerable degradation of vegetation and soil carbon and nutrients. Currently, this vital area is undergoing extensive ecological restoration through the employment of a variety of strategies, but the impact remains inadequately understood. This study seeks to compare the effects of different restoration strategies in the Qinghai Qaidam Basin, focusing on soil properties across five scenarios: a controlled desert area, natural restoration after the removal of L. chinense, continued planting of L. chinense, restoration through the planting of Haloxylon ammodendron, and mixed reseeding after four years of restoration. Our findings indicate that mixed reseeding significantly improved soil water storage to 4.26%, especially in the deep soil layer. The planting of H. ammodendron strategy efficiently reduced soil pH in such an alkaline environment. Soil nutrients, including total nitrogen (TN), total phosphorus (TP), and total potassium (TK), were predominantly concentrated in the top soil layer, with reduced concentrations observed in the medium and deep soil layers. Although soil organic matter remained relatively stable across all restoration strategies, its content was notably lower in the deeper layers. Overall, mixed reseeding proved to be the most efficient strategy for enhancing soil water retention and nutrient levels. In contrast, despite achieving high vegetative coverage to 62.6%, planting of L. chinense was less ecologically beneficial due to its extensive irrigation requirements and adverse effects on soil structure. These findings suggest that restoring degraded areas to an ideal ecological state cannot be achieved within a few years, underscoring the importance of sustained restoration efforts. This study offers valuable insights and practical guidance for the ecological restoration of arid lands, contributing to the development of sustainable land management practices in similar regions.

Morphological and Germination Characteristics of Alhagi maurorum Boiss. and Salsola richteri Kar. Seeds Distributed in the Karakum Desert of Turkmenistan

The Karakum Desert is the largest desert in Turkmenistan and covers a significant part of Central Asia. This desert is home to plant species that can adapt to hot, dry, and barren conditions. During the summer months, the Karakum Desert can get extremely hot, with temperatures reaching up to 50 °C, while in winter, it can drop to -20 °C. Therefore, the desert conditions significant seasonal temperature differences. In winter, rainfall is very low, snow rarely falls, and quickly melts. Afghan winds have an impact on the desert vegetation. The desert vegetation mainly consists of short grasses and woody shrubs. Despite the scarcity of rainfall and high temperatures during the summer months, steppe plants have generally been able to adapt to the harsh conditions of the desert. There are also species that have adapted to the desert climate, such as Alhagi maurorum Boiss., Haloxylon persicum Bunge, Haloxylon aphyllum (Minkw.) Iljin), Solanum nigrum L., and Salsola richteri Kar. These plants are highly valuable in terms of nutrition for animals and are used as winter animal feed in rural areas. In this study, the seed and germination characteristics of Alhagi maurorum Boiss. and Salsola richteri Kar, which are tree and shrub-like plants that can adapt to Karakum Desert conditions, were examined. In laboratory study, the morphological characteristics of the seeds were determined, and vitality and germination tests were conducted. Information was obtained about the germination adaptation of these plants in desert ecosystems. As a result of the study, it was determined that S. richteri had a very low rate of viable seeds and no germination, while the germination process of Alhagi maurorum could take a considerably long time.

Root exudates facilitate the regulation of soil microbial community function in the genus Haloxylon.

Root exudates act as the "language" of plant-soil communication, facilitating crucial interactions, information exchange, and energy transfer between plants and soil. The interactions facilitated by root exudates between plants and microorganisms in the rhizosphere are crucial for nutrient uptake and stress resilience in plants. However, the mechanism underlying the interaction between root exudates and rhizosphere microorganisms in desert plants under drought conditions remains unclear, especially among closely related species. To reveal the ecological strategies employed by the genus Haloxylon in different habitats. Using DNA extraction and sequencing and UPLC-Q-Tof/MS methods, we studied root exudates and soil microorganisms from two closely related species, Haloxylon ammodendron (HA) and Haloxylon persicum (HP), to assess differences in their root exudates, soil microbial composition, and interactions. Significant differences were found in soil properties and root traits between the two species, among which soil water content (SWC) and soil organic carbon (SOC) in rhizosphere and bulk soils (P < 0.05). While the metabolite classification of root exudates was similar, their components varied, with terpenoids being the main differential metabolites. Soil microbial structure and diversity also exhibited significant differences, with distinct key species in the network and differential functional processes mainly related to nitrogen and carbon cycles. Strong correlations were observed between root exudate-mediated root traits, soil microorganisms, and soil properties, although the complex interactions differed between the two closely relative species. The primary metabolites found in the network of HA include sugars and fatty acids, while HP relies on secondary metabolites, steroids and terpenoids. These findings suggest that root exudates are key in shaping rhizosphere microbial communities, increasing microbial functionality, fostering symbiotic relationships with hosts, and bolstering the resilience of plants to environmental stress.

Analyses of water dependency of Haloxylon ammodendron in arid regions of Iran using stable isotope technique.

The complex relationships within desert ecosystems and their environmental conditions are reflected in patterns of plant water use. Thus, understanding the sources of water used by plants in these areas is crucial for effective resource management. In this study, we investigated the water use pattern of Haloxylon ammodendron in Semnan province, in the central plateau of Iran, using the stable isotope analysis. We employed a simple, homemade cryogenic vacuum distillation (CVD) system to directly extract water from soil samples and different plant components for subsequent analysis by mass spectrometer. The contribution of each possible water source to the plant xylem water was estimated using the IsoSource mixing model. The pattern of 18O values in the xylem water of H. ammodendron indicated its reliance on groundwater as a primary water resource during the wet season. Additionally, the correlation of sand particles with both δ2H and δ18O was found to be 0.32. Moreover, the 18O values of H. ammodendron xylem water were mainly similar to those of groundwater, suggesting the species' dominant use of groundwater. The findings of this study provide valuable insights for strategically planting H. ammodendron to mitigate impacts on groundwater resources and ensure long-term sustainability in arid and semi-arid regions.

Dynamics of soil water, temperature, and salt and their coupled effects in Haloxylon ammodendron forests of different ages in an arid desert oasis ecotone

Study regionThe study region is a typical desert oasis ecotone of the Hexi Corridor, Northwest China. Study focusBased on four years of in situ observational data of soil water, temperature, and electrical conductivity obtained from three Haloxylon ammodendron (H. ammodendron) forests (20, 30 and 50 years) in a typical desert oasis ecotone (DOE) of the Hexi Corridor, in this study, the mechanisms of change and coupled effects of water, heat, and salt in frozen desert soils along a long-term shrub plantation in a typical desert oasis ecotone are presented. New hydrological insights for the regionThis study revealed that changes in soil water, heat, and salt and their coupling effects were completely different between shallow (0–80 cm) and deep (160–200 cm) depths. At 0–80 cm, soil water gradually decreased in the 50-year-old H. ammodendron plot, but soil salt first increased in the 30-year plot and then decreased in the 50-year plot. When the freezing process occurred in the 0–80 cm depth interval, the soil water and salt contents decreased nonlinearly with the absolute value of the soil temperature (|T|), following a power function and logarithmic function, respectively. For the thawing process in the 0–80 cm depth interval, soil water and salt increased with increasing temperature, and there was a significant linear relationship between soil water and salt (P<0.01). In the 160–200 cm layer, soil water and salt significantly increased after 30–50 years during the growing season.

Carbon Sequestration Characteristics of Typical Sand-Fixing Plantations in the Shiyang River Basin of Northwest China

A predominant management practice to reduce wind erosion in the arid deserts of northwest China is the planting of shrubs. However, the carbon sequestration capacity of these sand-fixing plantations has not received much attention. In this study, the carbon sequestration capacity of six typical sand-fixing plantations (Haloxylon ammodendron (C. A. Mey.) Bunge, Caragana korshinskii Kom., Tamarix ramosissima Ledeb., Calligonum mongolicum Turcz., Artemisia desertorum Spreng. and Hedysarum scoparium Fisch. &amp; C. A. Mey.) in the Shiyang River Basin were compared and analyzed. We evaluated how carbon sequestration may vary among different species, and examined if plantation age or management style (such as the additional construction of sand barriers, enclosure) positively or negatively influenced the carbon storage potential of these plantation ecosystems. Our results showed that all six plantations could store carbon, but plant species is the controlling factor driving carbon stock accumulation in plantations. The actual organic carbon stored beneath 25-year-old T. ramosissima, H. ammodendron, C. korshinskii, H. scoparium, C. mongolicum and A. desertorum plantations was 45.80, 31.80, 20.57, 20.2, 8.24 and1.76 Mg ha−1, respectively. Plantations using a clay–sand barrier had 1.3 times the carbon sequestration capacity of plantations that only used wheat straw and sand barriers. Similarly, enclosed plantations had 1.4 times the carbon storage capacity of unenclosed plantations. Plantation age greatly impacts carbon sequestration capacity. A 25-year-old H. ammodendron plantation has a carbon sequestration capacity three times greater than that of 3-year plantation. We conclude that while afforesting arid areas, H. ammodendron and T. ramosissima should be prioritized, and priority also should be given to using clay–sand barrier and enclosure.

Variation and coordination among the plant functional traits of three coexisting shrub species in arid conditions

Functional traits are critical indicators for assessing and predicting plant environmental adaptations and survival strategies. However, less attention has been paid to root functional traits due to the costly and destructive nature of field excavations. This has resulted in a poor understanding of organ trait associations and vegetation survival strategies, particularly for plants in arid environments. In this study, we investigated 11 classical plant functional traits (leaf, stem, and root) and the intact root systems of three dominant coexisting shrubs, Calligonum mongolicum, Nitraria sphaerocarpa, and Haloxylon ammodendron, in a typical oasis–desert ecotone in northwestern China. These three coexisting shrubs generally converge on conservative resource strategies with dimorphic root systems and small leaf mass fractions to cope with strong habitat filtering and survive in arid environments. However, we found significant interspecific divergences in functional traits. Specifically, C. mongolicum had the most conserved traits, the medium root depth (370 cm), and the highest root-shoot ratio (1.72). H. ammodendron had relatively conserved traits, with the most extensive root depth (420 cm, access to groundwater) and the lowest root–shoot ratio (0.45). N. sphaerocarpa had the least conservative traits, the shallowest root depth (200 cm), and the medium root–shoot ratio (1.14). These divergences promote ecological niche segregation and ensure the stable coexistence of shrubs in this resource-limited environment. In contrast to the whole-plant economics spectrum, there was limited coordination between aboveground and belowground functional traits across the three species. Therefore, it is speculated that the different organs of these three species may operate independently to manage different constraints. The deep-rooted H. ammodendron is highly dependent on groundwater; therefore, planting them extensively in the ecotone may increase local groundwater consumption, resulting in the severe degradation of these species, particularly in the context of consecutive oasis expansion and intensified climate change. These results are expected to contribute to the development of effective ecosystem restoration and afforestation practices in such oasis–desert ecotones.

Potential distribution of Haloxylon ammodendron in Central Asia under climate change

Potential distribution of Haloxylon ammodendron in Central Asia under climate change

Effects of stand structure on ecological benefits and tree growth of Haloxylon ammodendron plantations: A meta‐analysis

AbstractHaloxylon ammodendron is a typical tree species in arid region for windbreak and sand fixation. Understanding how stand structure (i.e., afforestation density, forest type, and stand age) of H. ammodendron impacts ecological benefits and tree growth status has great implications for desertification control in arid area. We obtained a dataset of 446 observations from 79 studies related to H. ammodendron plantations for meta‐analysis. Stand age was the key factor affecting performances of windbreak, tree canopy, and soil properties while afforestation density was more important in determining tree survival rate. Wind speed in H. ammodendron plantations was reduced by 52% in general compared to that at the site without any plantations and decreased as the increasing density. With the increase of stand age, soil carbon, nitrogen, and phosphorus accumulated continuously, but soil moisture in 0–60 cm depth decrease when trees grew up to nearly 20 years. Within 4000 plants ha−1, responses of survival rate, tree height, ground diameter, and canopy decreased with the increase of afforestation density. Compared with mono‐species plantation, mixed afforestation was more beneficial to windbreak and survival, while it damaged tree growth. Combining the ecological functions and tree growth of H. ammodendron plantations, the afforestation density and forest age should be controlled to 450–900 plants ha−1 and 20 years, respectively, as the upper limit. Therefore, besides reasonable afforestation density, management measures for regulations of forest age and existing stand density were important to maintain higher ecological benefits and better tree growth of H. ammodendron plantations.

Advancing the dominance of winter annuals under changing rainfall patterns in a temperate desert of Central Asia

Understanding how climate change-induced alterations in rainfall patterns impact the composition and structure of plant diversity is crucial. Examining variations in plant life forms is vital for comprehending ecosystem dynamics. This study analyzes plant life form diversity, rainfall variability, and the impact of different rainfall patterns on plant diversity over 15 years in the Gurbantünggüt Desert, a temperate desert in Central Asia. The study identified 96 plant species in the area, comprising 27 winter annuals and 33 perennial herbs. Over the past 15 years, species diversity has remained stable, while diversity among plant life forms has varied significantly. Winter annuals consistently dominated, showing a significant linear increase in importance values (slope=1.135). Conversely, perennial shrubs like Haloxylon ammodendron and Haloxylon persicum exhibited a marked declining trend. Over the past 15 years, the occurrence of minor (<1 mm) and moderate (1–5 mm) rainfall during the spring and autumn seasons initially rose and subsequently fell. Concurrently, heavy rainfall events (≥5 mm) in spring have waned, showing notable yearly fluctuations. The frequency of heavy autumnal downpours has remained steady, with consistent interannual variations. Minor rainfall events primarily influenced winter annuals and perennial herbs during the spring and autumn, whereas heavy rainfall mainly affected perennial shrubs during these seasons. Our investigations suggest that winter annuals, despite their expanding presence, are ineffective in their ecological functions such as dune stabilization and reducing aeolian erosion in the peak summer months. In contrast, perennial shrubs like H. ammodendron and H. persicum, crucial for these roles, are markedly declining. The variable plant life forms might lead to modifications in the ecological roles of the region, thereby rendering it imperative to persistently observe this desert and proactively formulate conservation strategies for the vegetation.

Response of two dominant woody species to groundwater depth at the transition zone between desert and oasis

Haloxylon species are traditionally considered as dominant desert plants across Central Asia, but recent studies based on stable isotope showed that they are groundwater-dependent, however, their tolerance strategies and limits to groundwater decline remain unknown. Therefore, we adopted the method of spatial-for-temporal, took Haloxylon ammodendron and Haloxylon. persicum in Gurbantunggut Desert as study objects, combined field survey with model estimation exploring their density, growth, age, and biomass characteristics along a natural groundwater gradient, aiming to reveal their responses to groundwater depth changes and predict future development. The results showed that: (1) With the decline of groundwater depth, the population density, and plant height, canopy width, and basal diameter of two species all decreased significantly. （2）When the groundwater depth descended to lower than 12 m, H. persicum replaced H. ammodendron becoming the more dominant species. (3) As the groundwater depth declined, adult individual percentage increased in the population of H. ammodendron, but H. persicum was still dominated by young trees. (4) The above-ground, below-ground and total biomass of two species were all going down with the lowering of groundwater table, H. ammodendron exhibited a greater reduction, while the root-to-shoot ratio of H. persicum increased significantly (p < 0.05). These findings indicated that continuous decline in groundwater depth greatly limited the survival and development of H. ammodendron, the allocation regulation of H. persicum helped to cushion the adverse effects partially. In the long run, decreased accessibility of groundwater would be not conducive to the exertion of their ecological functions. These findings could provide a scientific basis for the protection and management of these valuable species.

Dark septate endophytes enhance the drought tolerance of Haloxylon ammodendron in sterilized and nonsterilized soil

Dark septate endophytes (DSEs) are a type of endophytic fungus that commonly colonize plant root systems in extreme environments, and play a role in enhancing resistance to drought stress. To investigate the potential applications of DSEs in improving drought tolerance of desert plants, three DSE strains isolated from Haloxylon ammodendron for strong drought tolerance - Alternaria tellustris (AT), Cladosporium sp. (CL), and Paraphoma radicina (PR) - were screened through pure culture in vitro. Pot experiments of H. ammodendron were then conducted with different DSE, water, and soil treatments. In both sterilized and nonsterilized soil, DSEs showed growth-promoting and drought-resistant properties, with a stronger effect observed under sterilized soil treatment. The results showed that in sterilized soil, AT and CL increased root biomass, total biomass and root shoot ratio under high drought treatment, while PR effectively enhanced branch number and root biomass under normal water treatment. Physiologically, DSEs improved plant drought tolerance by increasing soluble sugar content and superoxide dismutase activity. Notably, DSE inoculation facilitated the uptake and utilization of soil nutrients such as available phosphorus, nitrate nitrogen, and free amino acids by plants in both sterilized and nonsterilized soil. Overall, our study highlights the potential of DSEs in improving drought resistance and promoting the growth of desert plants.

Population regeneration of two Haloxylon species in central Asian deserts as affected by groundwater depth

Haloxylon ammodendron and Haloxylon persicum are the dominant species in the deserts of Central Asia. As groundwater exploration has resulted in a decline in groundwater depth in this region, the impact on the regeneration of these two Haloxylon populations calls for urgent attention. Therefore, we conducted an intensive vegetation survey, including population density, age structure and seed production and seed characteristics, along a groundwater depth gradient in the Gurbantunggut Desert of Central Asia. The result shows that for H. ammodendron, groundwater depth of 15 m is its survival and regeneration limit, beyond which this species cannot grow. However, for H. persicum, this limit does not apply. Instead, declined groundwater depth promotes a reproduction strategy with low seed quantity, high quality, and a high germination rate for H. ammodendron. Ultimately, H. ammodendron exhibits a tighter regeneration trait coordination, with a reasonable age structure being crucial for its population continuation and environmental adaptation. In contrast, H. persicum demonstrates higher resource acquisition and reproductive ability, along with tolerance to groundwater depth decline. In conclusion, if the groundwater depth decline continues, the continuation of H. ammodendron will be seriously threatened but H. persicum will not be. This study is beneficial for evaluating the future trend of vegetation cover in desert region and planning water resources management in Central Asia.

Response of soil inorganic nitrogen dynamics to planting age and vegetation type in artificial sand‐fixing land

AbstractVegetation restoration in dryland regions may be a powerful way to control desertification and promote local habitat recovery. In these artificial revegetation systems, ecosystem processes and functioning are strongly determined by nitrogen (N) availability, while soil inorganic N (SIN) is the major available N form and is absorbed as a main N source for plants. However, SIN dynamics, their influencing factors, and their relative importance to the ecosystem of these N‐limited systems are not well understood. A field investigation was conducted to examine the monthly variations in SIN and its response to planting age and vegetation type in a typical artificial sand‐fixing system in northwestern China. The SIN content in topsoil (0–20 cm) during the growing season ranged from 7.10 to 95.65 mg kg−1, with a mean value of 27.14 mg kg−1. Soil nitrate N had a dominant role in determining SIN monthly dynamics, which showed a fluctuating trend with two peak values in early July and late August. SIN showed a significant increasing trend with the planting age of sand‐fixing vegetation, and it was highest for Nitraria sphaerocarpa (55.66 ± 5.76 mg kg−1), followed by Haloxylon ammodendron (29.81 ± 3.47 mg kg−1) and interspace (11.39 ± 1.13 mg kg−1). SIN displayed a hump‐shaped relationship with air temperature (R2 = 0.96, p &lt; 0.01) and had a maximum at 19.88°C. The change rate of SIN was positively correlated with accumulated precipitation (R2 = 0.99, p &lt; 0.05). SIN was correlated significantly with soil organic carbon (SOC), total nitrogen (TN), and soil clay content. Our results revealed that climatic (air temperature and precipitation), abiotic (soil texture), plant (planting age and vegetation type), and nutrient‐related (SOC and TN) factors regulate SIN dynamics in artificial sand‐fixing vegetation systems. Climate was the predominant factor affecting soil ammonium N, and soil nutrients (SOC and TN) were the predominant factor affecting soil nitrate N. Therefore, these factors should be integrated into optimizing regional vegetation establishment and improving ecosystem management practices in sand‐fixing lands.

Effects of Great Gerbil Disturbance on Photosynthetic Characteristics and Nutrient Status of Haloxylon ammodendron.

Rodents, such as those that feed on plants and nest in plant roots, can significantly affect the growth and development of desert plants. The aim of this study was to investigate the effects of Rhombomys opimus disturbance on the photosynthetic characteristics and nutrient status of Haloxylon ammodendron at different growth stages in the Gurbantunggut Desert. The effects of great gerbil disturbance on the photosynthetic characteristics of H. ammodendron at different growth stages were investigated by measuring the gas exchange parameters, instantaneous water use efficiency, and chlorophyll fluorescence parameters of H. ammodendron at different ages (young, middle, and adult) under the disturbance of great gerbils. The soil nutrients in the assimilated branches and rhizosphere of H. ammodendron at different growth stages were tracked to reveal the relationship between the H. ammodendron nutrient content and gerbil disturbance. The results showed that great gerbil disturbance decreased the organic carbon content in the rhizosphere soil of adult H. ammodendron and increased the total nitrogen content in the rhizosphere soil and the nitrogen and potassium contents in the assimilated branches at each growth stage. The net photosynthetic rate and instantaneous water use efficiency of H. ammodendron decreased at each growth stage, and the maximum photochemical efficiency and non-photochemical quenching parameters of the young H. ammodendron decreased. However, the actual photochemical efficiency and photochemical parameters of the middle H. ammodendron increased. It was concluded that the disturbance of great gerbils decreased the photosynthetic capacity of H. ammodendron and increased the content of total nitrogen in the soil and nitrogen and potassium in the plant. This study revealed that the Gurbantunggut Desert great gerbil and H. ammodendron do not have a simple predation relationship. It laid a foundation for the study of the moderate disturbance threshold and better use of the mutually beneficial relationship between the two.

Rapid detection of Alternaria spp. by PCR in the newly created forest plantations on the drained bottom of the Aral Sea

Salinization and drought are the most important abiotic stress factors causing significant impact to the agriculture of Uzbekistan. To eliminate the negative consequences of the drying of the Aral Sea, large-scale works are currently being conducted on this territory to create protective forest plantations of halophytic trees and shrubs. An important issue in the protection of forest plantations is the isolation, identification and monitoring of phytopathogenic fungi associated with these forest plantations. The study's objective was to isolate Alternaria fungi from Haloxylon aphyllum (Minkw.) Iljin, Tamarix hispida Willd., T. ramossisima Ledeb. and to also apply a diagnostic marker using PCR assays to detect and identify Alternaria pathogens in these plants. As a result of the study, 10 strains of Alternaria fungi were isolated from plant samples of black saxaul – Haloxylon aphyllum, and two tamarisk species – Tamarix hispida, Tamarix ramossisima. The dominant species was: Alternaria tenuissima (Kunze) Wiltshire. β-tubulin gene was used as a molecular marker to distinguish and identify Alternaria spp in 34 leaf samples of Haloxylon aphyllum, Tamarix hispida and Tamarix ramossisima. The primer set used in the PCR assay was shown to be capable of detecting the presence of Alternaria in the leaves. Therefore, a β-tubulin-based diagnostic marker can be widely applied for monitoring of Alternaria infecting a wide-range of halophytic trees and shrubs in the protective forest plantations.

Fungal Hyphae on the Assimilation Branches Are Beneficial for Haloxylon ammodendron to Absorb Atmospheric Water Vapor: Adapting to an Extreme Drought Environment.

Research on endophytic fungi in desert plants, particularly the epiphytic or endophytic fungi of leaves, remains limited. In the extremely arid regions of northwest China, the ultra-xerophytic desert plant Haloxylon ammodendron harbors white fungi on its assimilating branches during autumn. The hyphae of these fungi intertwine, both internally and externally, comprising superficial, bridging, and endophytic types. The superficial hyphae attach to the surface of the assimilating branches and continuously grow and intersect, forming a thick layer of felt-like hyphae. This thick, felt-like layer of hyphae facilitates the adsorption of atmospheric water vapor on the surface of the hyphae or the assimilating branches, allowing H. ammodendron to capture atmospheric moisture, even under low humidity. Some superficial hyphae penetrate the cuticle into the epidermis, becoming bridging hyphae, which can rapidly transport water from the outside of the epidermis to the inside. The endophytic hyphae shuttle within the epidermis, achieving rapid water transfer within the epidermis of the assimilating branches. The presence of these three types of hyphae not only enables the assimilating branches of H. ammodendron to achieve rapid water absorption and transmission, but also facilitates the uptake of atmospheric water vapor under low humidity conditions. We discuss the mechanism by which the hyphae promote water absorption from the perspectives of hyphal composition, the formation of felt-like structures, and environmental conditions. We consider the presence of fungal hyphae on the surface of the H. ammodendron assimilating branches as an inevitable ecological process in arid environments. This study provides important theoretical insights into the mechanisms underlying the strong drought resistance of desert plants in extremely arid regions and offers strategies for desertification control.

Morpho-physiological adaptations to drought stress in nitrogen-fixing and non-nitrogen-fixing plants

Drought profoundly affects the morpho-physiological responses of desert plants in dryland. To scrutinize the morpho-physiological responses of nitrogen (N)-fixing legumes (Ammopiptanthus mongolicus, Caragana korshinskii), N-fixing non-legumes (Elaeagnus angustifolia, Hippophae rhamnoides), and non-N-fixing plants (Nitraria tangutorum, Haloxylon ammodendron) under varied drought stress levels (75%, 50%, 25% and 5% of soil water holding capacity), a pot experiment was conducted in greenhouse. Following prolonged water deficit, carbon (C) and N stoichiometry, metabolic rates, plant growth, and biomass distribution of unstressed and stressed plants were recorded. Intensified drought significantly reduced stem, root and whole-plant biomass, with no significant changes observed in leaf dry-fresh mass ratio, specific leaf area, intrinsic water use efficiency and root to shoot ratio. However, other traits were impacted differently, reflecting distinct adaptive strategies to drought among three plant functional types (PFTs). Patterns of trait-soil water content (SWC) relationships varied across different PFTs, with N-fixing non-legumes followed by N-fixing legumes displayed greater sensitivity to SWC variations than non-N-fixing plants. This resulted in a shift from a stronger trait-SWC relationship in N-fixing non-legumes and N-fixing legumes to a less correlated relationship in non-N-fixing plants. The diverse responses to drought among PFTs suggest a shift from N limitation to water limitation as SWC decreases.

Anatomical and Metabolome Features of Haloxylon aphyllum and Haloxylon persicum Elucidate the Resilience against Gall-Forming Insects.

Globally, gall-forming insects significantly contribute to the degradation of desert ecosystems. Recent studies have demonstrated that Haloxylon persicum suffers less damage from gall-formers compared to Haloxylon aphyllum. However, the mechanisms driving the long-term metabolic responses of these species to gall-forming biotic stress in their natural environment remain unclear. The current study comparatively analyzes the anatomical features and metabolomic changes in H. aphyllum and H. persicum damaged by gall-forming insects. This research aimed to uncover potential metabolic tolerance mechanisms through GC-MS analysis. The study findings indicate that gall-forming insects cause a reduction in nearly all the anatomical structures of Haloxylon shoots, with the effects being less severe in H. persicum than in H. aphyllum. Thus, the metabolic pathways responsible for the biosynthesis of biologically active substances that enhance resistance to gall inducers were different, specifically in H. aphyllum-the biosynthesis of fatty acids (+their derivatives) and γ-tocopherol (vitamin E) and H. persicum-the biosynthesis of fatty acids (+their derivatives), dialkyl ethers, carbohydrates (+their derivatives), aromatic acid derivatives, phytosterols, γ-tocopherol (vitamin E), phenols, and terpenoids. The results suggest that the modulation of metabolic pathways under biotic stress plays a crucial role in the enhanced survival and growth of H. persicum.