Tamarix Ramosissima Research Articles

Contribution of Fine Roots to Soil Organic Carbon Accumulation in Different Desert Communities in the Sangong River Basin.

This study explored the relationship between soil organic carbon (SOC) and root distribution, with the aim of evaluating the carbon stocks and sequestration potential under five plant communities (Alhagi sparsifolia, Tamarix ramosissima, Reaumuria soongorica, Haloxylon ammodendron, and Phragmites communis) in an arid region, the Sangong River watershed desert ecosystem. Root biomass, ecological factors, and SOC in different layers of a 0–100 cm soil profile were investigated. The results demonstrated that almost all living fine root biomass (11.78–34.41 g/m2) and dead fine root biomass (5.64–15.45 g/m2) levels were highest in the 10–20 cm layer, except for the P. communis community, which showed the highest living and dead fine root biomass at a depth of 60–70 cm. Fine root biomass showed strong seasonal dynamics in the five communities from June to October. The biomass levels of the A. sparsifolia (138.31 g/m2) and H. ammodendron (229.73 g/m2) communities were highest in August, whereas those of the T. ramosissima (87.76 g/m2), R. soongorica (66.29 g/m2), and P. communis (148.31 g/m2) communities were highest in September. The SOC of the five communities displayed strong changes with increasing soil depth. The mean SOC value across all five communities was 77.36% at 0–30 cm. The highest SOC values of the A. sparsifolia (3.08 g/kg), T. ramosissima (2.35 g/kg), and R. soongorica (2.34 g/kg) communities were found in June, and the highest value of the H. ammodendron (2.25 and 2.31 g/kg, p > 0.05) community was found in June and September. The highest SOC values of the P. communis (1.88 g/kg) community were found in July. Fine root production and turnover rate were 50.67–486.92 g/m2/year and 1.25–1.98 times per year. The relationships among SOC, fine root biomass, and ecological factors (soil water content and soil bulk density) were significant for all five communities. Based on the results, higher soil water content and soil conductivity favored the decomposition of root litter and increased fine root turnover, thereby facilitating SOC formation. Higher pH and bulk density levels are not conducive to soil biological activity and SOC mineralization, leading to increased SOC levels in desert regions.

Eco-Hydrological Response of Water Conveyance in the Mainstream of the Tarim River, China

Desert riparian vegetation forms an ecological corridor in extremely arid environments, and ecological water conveyance is an important measure of vegetation restoration and biodiversity conservation in desert riparian zones. Studying the responses of vegetation to ecological water conveyance and changes in this process in arid desert riparian zones and assessing the comprehensive benefits of ecological water conveyance are highly significant for ecological conservation and restoration in addition to the formulation of water transfer policies. Previous studies mainly used a single indicator to evaluate the ecological restoration of the mainstream Tarim River in Northwest China; thus, systematic and comprehensive assessments based on multiple indicators have not been conducted. In the present study, remote sensing data and field surveys were used to analyze the ecological restoration status of the Tarim River during 2015–2021 in terms of hydrological responses, vegetation responses, and ecological water conveyance benefits. The results showed that groundwater levels and soil moisture in the mainstream area of the Tarim River increased significantly from 2015 to 2021. The amount of groundwater storage also increased. Ecological water conveyance has created good hydrological conditions for groundwater recharge and ecological restoration on both sides of the mainstream area of the Tarim River. Desert forest ecosystems, mainly comprising Populus euphratica and Tamarix ramosissima, have been saved and rejuvenated in water conveyance areas. After ecological water conveyance, the Simpson and Shannon–Wiener indices increased significantly, but the diversity level began to decline and then stabilize with the increase in water conveyance frequency. The overall habitat status improved and the quality of the ecological environment below the Wusiman section of the middle reaches of the Tarim River improved significantly.

Effects of Exogenous Potassium (K+) Application on the Antioxidant Enzymes Activities in Leaves of Tamarix ramosissima under NaCl Stress.

Saline soil is a worldwide distributed resource that seriously harms plants’ growth and development. NaCl is the most widely distributed salt in saline soil. As a typical representative of halophytes, Tamarix ramosissima Lcdcb (T. ramosissima) is commonly grown in salinized soil, and halophytes have different abilities to retain more K+ under salt stress conditions. Halophytes can adapt to different salt environments by improving the scavenging activity of reactive oxygen species (ROS) by absorbing and transporting potassium (K+). In this study, electron microscope observation, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents determination, primary antioxidant enzyme activity determination and transcriptome sequencing analysis were carried out on the leaves of T. ramosissima under NaCl stress at 0 h, 48 h and 168 h. The results showed that H2O2 and MDA contents increased in the 200 mM NaCl + 10 mM KCl and 200 mM NaCl groups, but the content increased the most in the 200 mM NaCl group at 168 h. In addition, the leaves of T. ramosissima in the 200 mM NaCl + 10 mM KCl group had the most salt secretion, and its superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were all higher than those of the 200 mM NaCl group and significantly higher than those of the control group. According to the results of transcriptome sequencing, it was found that the expression of 39 genes related to antioxidant enzyme activity changed significantly at the transcriptional level. Among them, 15 genes related to antioxidant enzyme activities were upregulated, and 24 genes related to antioxidant enzyme activities were downregulated in the leaves of T. ramosissima when exogenous potassium (K+) was applied under NaCl stress for 48 h; when exogenous potassium (K+) was used for 168 h under NaCl stress, 21 antioxidant enzyme activity-related genes were upregulated, and 18 antioxidant enzyme activity-related genes were downregulated in T. ramosissima leaves. Based on the changes of expression levels at different treatment times, 10 key candidates differentially expressed genes (DEGs) (Unigene0050462, Unigene0014843, Unigene0046159, Unigene0046160, Unigene0008032, Unigene0048033, Unigene0004890, Unigene0015109, Unigene0020552 and Unigene0048538) for antioxidant enzyme activities were further screened. They played an important role in applying exogenous potassium (K+) for 48 h and 168 h to the leaves of T. ramosissima in response to NaCl stress. Their expression levels were dominated by upregulation, which enhanced the activity of antioxidant enzymes, and helped T. ramosissima mitigate NaCl poison and resist NaCl stress. Particularly, Unigene0048538 in glutathione S-transferase (GST) activity had the largest log2 fold-change in the comparison groups of 200 mM NaCl-48 h vs. 200 mM NaCl + 10 mM KCl-48 h and 200 mM NaCl-168 h vs. 200 mM NaCl + 10 mM KCl-168 h. Its expression level was upregulated and played an important role in NaCl toxicity. At the same time, the results of the phylogenetic tree analysis showed that Unigene0048538 had the closest genetic distance to Prunus persica in the evolutionary relationship. In summary, with the increase of exogenous potassium (K+) application time under NaCl stress, T. ramosissima can resist high NaCl stress by enhancing antioxidant enzymes’ activity and maintaining the growth of T. ramosissima. Still, it is not enough to completely eliminate NaCl poison. This study provides a theoretical basis for the molecular mechanism of salt tolerance and K+ mitigation of NaCl poison by the representative halophyte T. ramosissima in response to NaCl stress.

Analysis of Amino Acids in the Roots of Tamarix ramosissima by Application of Exogenous Potassium (K+) under NaCl Stress.

Soil salinization is one of the main environmental factors affecting plant growth worldwide. Tamarix ramosissima Ledeb. (T. ramosissima) is a halophyte representative that is widely grown in salinized soils. As an important nutrient element for plant growth, K+ plays an important role in improving the tolerance to salt stress, but the mechanism of reducing the damage caused by NaCl stress to T. ramosissima is less reported. Our results show that the proline content and the Log2 fold-change of proline’s relative quantification in the roots of T. ramosissima increased over time with the application of exogenous potassium (K+) for 48 h and 168 h under NaCl stress. Moreover, 13 amino-acid-related metabolic pathways were involved in the resistance of T. ramosissima to salt stress. Mainly, the aldehyde dehydrogenase family genes and tryptophan-synthase-related genes were found at 48 h and 168 h with exogenous potassium applied to the roots of T. ramosissima under NaCl stress, and they regulated their related metabolic accumulation in the arginine and proline metabolism pathways, increasing the effectiveness of inducing NaCl tolerance of T. ramosissima. It is noteworthy that alpha-ketobutyric was produced in the roots of T. ramosissima under NaCl stress for 48 h with the application of exogenous potassium, which is one of the most effective mechanisms for inducing salt tolerance in plants. Meanwhile, we found three DEGs regulating alpha-ketobutyric acid. This study provides a scientific theoretical basis for further understanding the molecular mechanism of K+ alleviating the salinity damage to T. ramosissima caused by NaCl.

Predicting the potential distribution of four endangered holoparasites and their primary hosts in China under climate change.

Climate change affects parasitic plants and their hosts on distributions. However, little is known about how parasites and their hosts shift in distribution, and niche overlap in response to global change remains unclear to date. Here, the potential distribution and habitat suitability of four endangered holoparasites and their primary hosts in northern China were predicted using MaxEnt based on occurrence records and bioclimatic variables. The results indicated that (1) Temperature annual range (Bio7) and Precipitation of driest quarter (Bio17) were identified as the common key climatic factors influencing distribution (percentage contribution > 10%) for Cynomorium songaricum vs. Nitraria sibirica (i.e., parasite vs. host); Temperature seasonality (Bio4) and Precipitation of driest month (Bio14) for Boschniakia rossica vs. Alnus mandshurica; Bio4 for Cistanche deserticola vs. Haloxylon ammodendron; Precipitation of warmest quarter (Bio18) for Cistanche mongolica vs. Tamarix ramosissima. Accordingly, different parasite-host pairs share to varying degree the common climatic factors. (2) Currently, these holoparasites had small suitable habitats (i.e., moderately and highly) (0.97–3.77%), with few highly suitable habitats (0.19–0.81%). Under future scenarios, their suitable habitats would change to some extent; their distribution shifts fell into two categories: growing type (Boschniakia rossica and Cistanche mongolica) and fluctuating type (Cynomorium songaricum and Cistanche deserticola). In contrast, the hosts’ current suitable habitats (1.42–13.43%) varied greatly, with highly restricted suitable habitats (0.18–1.00%). Under future scenarios, their suitable habitats presented different trends: growing type (Nitraria sibirica), declining type (Haloxylon ammodendron) and fluctuating type (the other hosts). (3) The niche overlaps between parasites and hosts differed significantly in the future, which can be grouped into two categories: growing type (Boschniakia rossica vs. Alnus mandshurica, Cistanche mongolica vs. Tamarix ramosissima), and fluctuating type (the others). Such niche overlap asynchronies may result in severe spatial limitations of parasites under future climate conditions. Our findings indicate that climate factors restricting parasites and hosts’ distributions, niche overlaps between them, together with parasitic species identity, may jointly influence the suitable habitats of parasitic plants. Therefore, it is necessary to take into account the threatened holoparasites themselves in conjunction with their suitable habitats and the parasite-host association when developing conservation planning in the future.

Coupling the water use of Populus euphratica and Tamarix ramosissima and evapotranspiration partitioning in a desert riparian forest ecosystem

Evapotranspiration (ET) partitioning involves determining how the flux of water is mediated by abiotic and biotic pathways. Previous studies have shown the average transpiration fraction (T/ET) from sites to global scales. However, few studies couple plant water use with ET partitioning to understanding how changes in plant community structure affect the seasonal to interannual variability in ET partitioning in desert riparian forest ecosystem. In this study, we used an isotope tracer coupled to a ''multi-source'' model to estimate the ET and its components, such as soil evaporation (E) and plant transpiration (T). The total T was further partitioned into the transpiration of Populus euphratica (Tp) and Tamarix ramosissima (Tt). The consistency of R2 (0.78 and 0.74) between the simulated and total ET measured by eddy covariance and Tp by sap flow illustrated that this model can reconstruct the water exchange in desert riparian forest ecosystem. The fraction Tp/ET was slightly higher than Tt/ET, but less than E/ET, and their ratios were 0.16, 0.14 and 0.70, respectively, from 2014 to 2017. The fractions of Tp/T and Tt/T were almost equal values of 52% and 48%. The different water use strategies and stomatal conductance sensitivities between P. euphratica and T. ramosissima demonstrated that their different responses to the changes of vapor pressure deficit (VPD) and groundwater depth. In drought period, Tp was greater than Tt, indicating that P. euphratica had a competitive advantage because of its deep groundwater utilization strategy and high sensitivity to stomatal conductance. The change of community structure indicated by increase coverage of P. euphratica in desert riparian forest ecosystem had significant enhance on T/ET than total ET. This study emphasizes that considering the different water uses among various species to optimize the ecological water demand will improve the management of desert riparian forest ecosystems.

Transcriptome and Metabonomic Analysis of Tamarix ramosissima Potassium (K+) Channels and Transporters in Response to NaCl Stress.

Potassium ion (K+) channels and transporters are key components of plant K+ absorption and transportation and play an important role in plant growth and development. This study revealed that K+ channels and transporters are involved in the salt tolerance molecular mechanism and metabolites of the halophyte representative plant Tamarix ramosissima (T. ramosissima) in response to NaCl stress, providing a theoretical basis for the mitigation of salt stress using halophytes. Through transcriptome sequencing and metabolite detection analysis of 0 h, 48 h and 168 h by applying exogenous K+ to the roots of T. ramosissima under NaCl stress, 15 high-quality Clean Data bases were obtained, Q20 reached more than 97%, Q30 reached more than 92%, and GC content reached 44.5%, which is in line with further bioinformatics analysis. Based on the Liquid chromatography–mass spectrometry (LC-MS) analysis, the roots of T. ramosissima were exposed to exogenous potassium for 48 h and 168 h under NaCl stress, and 1510 and 1124 metabolites were identified in positive and negative ion mode, respectively. Through orthogonal projections to latent structures discriminant analysis (OPLS-DA) model analysis, its metabolomic data have excellent predictability and stability. The results of this study showed that there were 37 differentially expressed genes (DEGs) annotated as Class 2 K+ channels (Shaker-like K+ channel and TPK channel) and Class 3 K+ transporters (HAK/KUP/KT, HKT and CPAs transporter families). Among them, 29 DEGs were annotated to the gene ontology (GO) database, and the most genes were involved in the GO Biological Process. In addition, the expression levels of Unigene0014342 in the HAK/KUP/KT transporter and Unigene0088276 and Unigene0103067 in the CPAs transporter both first decreased and then increased when treated with 200 mM NaCl for 48 h and 168 h. However, when treated with 200 mM NaCl + 10 mM KCl for 48 h and 168 h, a continuous upward trend was shown. Notably, the expression level of Unigene0016813 in CPAS transporter continued to increase when treated with 200 mM NaCl and 200 mM NaCl + 10 mM KCl for 48 h and 168 h. 3 DEGs, Unigene0088276, Unigene0016813 and Unigene0103067, were dominated by the positive regulation of their related metabolites, and this correlation was significant. The results showed that these DEGs increased the absorption of K+ and the ratio of K+/Na+ under NaCl stress at 48 h and 168 h after adding exogenous potassium and enhanced the salt tolerance of T. ramosissima. Notably, the expression level of Unigene0103067 in the CPAs transporter was consistently upregulated when 200 mM NaCl + 10 mM KCl was treated for 48 h and 168 h. The positive regulatory metabolites were always dominant, which better helped T. ramosissima resist salt stress. Unigene0103067 plays an important role in enhancing the salt tolerance of T. ramosissima and reducing the toxicity of NaCl in roots. Additionally, phylogenetic tree analysis showed that Unigene0103067 and Reaumuria trigyna had the closest genetic distance in the evolutionary relationship. Finally, 9 DEGs were randomly selected for quantitative real-time PCR (qRT-PCR) verification. Their expression trends were completely consistent with the transcriptome sequencing analysis results, proving that this study’s data are accurate and reliable. This study provides resources for revealing the molecular mechanism of NaCl stress tolerance in T. ramosissima and lays a theoretical foundation for cultivating new salt-tolerant varieties.

Responses of microbial communities and metabolic profiles to the rhizosphere of Tamarix ramosissima in soils contaminated by multiple heavy metals

Heavy metals (HMs) contamination around smelters poses serious stress to soil microbiome. However, the co-effect of multiple HMs and native vegetation rhizosphere on the soil ecosystem remains unclear. Herein, effects of high HMs level and the rhizosphere (Tamarix ramosissima) on soil bacterial community structure and metabolic profiles in sierozem were analyzed by coupling high-throughput sequencing and soil metabolomics. Plant roots alleviated the threat of HMs by absorbing and stabilizing them in soil. High HMs level decreased the richness and diversity of soil bacterial community and increased numbers of special bacteria. Plant roots changed the contribution of HMs species shaping the bacterial community. Cd and Zn were the main contributors to bacterial distribution in non-rhizosphere soil, however, Pb and Cu became the most important HMs in rhizosphere soil. HMs induced more dominant metal-tolerant bacteria in non-rhizosphere than rhizosphere soil. Meanwhile, critical metabolites varied by rhizosphere in co-occurrence networks. Moreover, the same HMs-tolerant bacteria were regulated by different metabolites, e.g. unclassified family AKYG1722 was promoted by Dodecanoic acid in non-rhizosphere soil, while promoted by Octadecane, 2-methyl- in rhizosphere soil. The study illustrated that high HMs level and rhizosphere affected soil properties and metabolites, by which soil microbial community structure was reshaped.

Whole-Plant Water Use and Hydraulics of Populus euphratica and Tamarix ramosissima Seedlings in Adaption to Groundwater Variation

Riparian phreatophytes in hyperarid areas face selection pressure from limiting groundwater availability and high transpiration demand. We examined whole-plant water use and hydraulic traits in Populus euphratica and Tamarix ramosissima seedlings to understand how they adapt to groundwater variations. These species coexist in the Tarim River floodplain of western China. Measurements were performed on 3-year-old seedlings grown in lysimeters simulating various groundwater depths. P. euphratica had relatively greater leaf area-specific water use due to its comparatively higher sapwood area to leaf area ratio (Hv). A high Hv indicates that its sapwood has a limited capacity to support its leaf area. P. euphratica also showed significantly higher leaf-specific conductivity (ksl) than T. ramosissima but both had similar sapwood-specific conductivities (kss). Therefore, it was Hv rather than kss which accounted for the interspecific difference in ksl. When groundwater was not directly available, ksl and Hv in P. euphratica were increased. This response favors water loss control, but limits plant growth. In contrast, T. ramosissima is more capable of using deep groundwater. Stomatal sensitivity to increasing leaf-to-area vapor pressure deficit was also higher in P. euphratica. Overall, P. euphratica is less effective than T. ramosissima at compensating for transpirational water loss at a whole-plant level. For this reason, P. euphratica is restricted to riverbanks, whereas T. ramosissima occurs over a wide range of groundwater depths.

Temporal variation in stomatal sensitivity to vapour pressure deficit in western riparian forests

Abstract Increasing atmospheric vapour pressure deficit (D) can influence plant water and carbon uptake. However, growing season variation in stomatal responses to D among tree taxa has not been thoroughly quantified and therefore has not been well‐characterized in stomatal regulation models. Using sap flux data from nine riparian species spanning a 600‐m elevation gradient in semi‐arid northern Utah, USA, we fit a time‐varying empirical model of stomatal conductance to D in a hierarchical Bayesian framework. The reference conductance (Gref, conductance at D = 1 kPa) term was modelled as a function of cumulative growing season D, which varied with site elevation. Seven species exhibited Gref that varied significantly with cumulative growing season D, but the direction was not consistent among species. Two low‐elevation ring‐porous species, the invasive Tamarix ramosissima and Elaeagnus angustifolia, exhibited significantly positive correlation between Gref and cumulative D, such that standardized stomatal sensitivity (S) decreased during the season. Despite lower D at the mid‐ and high‐elevation sites, five diffuse‐porous native species exhibited progressively increasing sensitivity to D during the growing season. Stomatal strategies exhibit seasonal trends that vary by environmental conditions (D) and functional traits (wood anatomy), which complicates the prediction of plant hydraulic function under increasing atmospheric drought. In the increasingly arid western United States, the progressively less sensitive stomatal behaviour of invasive taxa may hasten their dominance in riparian forests. Read the free Plain Language Summary for this article on the Journal blog.

Butterfly Assemblages Associated with Restored Riparian Uplands: Las Vegas Wash, Nevada, USA

The butterfly assemblage found at riparian upland plant restoration areas (after removal of the invasive plant, tamarisk (Tamarix ramosissima Ledebour)) along Las Vegas Wash was examined over four different months. Upland areas were planted with a variety of plants, however, those with a mesquite (Prosopis spp. Linneaus) component contained additional butterfly species relative to other plots. Detrended correspondence analysis demonstrated a gradient of butterfly species that corresponded with mesquite, age of stand, and homogenous areas of tamarisk. Some potential butterfly species went undetected; perhaps because required herbaceous understory plants were absent, or the need for greater densities of the hemiparasitic mistletoe (Phoradendron) (Nutt.) which is utilized by certain butterfly species. A single plot of exotic tamarisk, the near-past dominant shrub of the Wash landscape, was examined. An incursion of the beetle Diorhabda carinulata (Desbrochers), a phytophagous tamarisk control agent, appeared to affect tamarisk nectar production along with butterfly abundance at the plot. Butterfly response to nectar at inadvertent seep areas suggests these features are important for butterfly directed landscape restoration activities. Use of a characteristic butterfly community for identifying goals for upland restoration was valuable in describing end-points that incorporated assets of natural mesquite bosques.

Germination characteristics of plump and shriveled seeds of Tamarix ramosissima matured in different seasons

Tamarix ramosissima has bi-seasonal flowering and fruiting. Although the basic germination characteristics of T. ramosissima seeds have been evaluated, there is a lack of information about the effects of seed plumpness on germination. Effects of seed plumpness and season of maturity and light conditions on germination were tested. Plump seeds matured in spring or summer had similar size and pappus length. The size of plump seeds was significantly larger than that of shriveled seeds. Both types of seeds matured in summer germinated better than seeds matured in spring. Germination percentage of plump seeds was significant higher than that of shriveled seeds, especially for seeds matured in spring. Darkness significantly decreased the germination of seeds matured in summer. This study provides comprehensive information about the seed germination requirements of T. ramosissima and the results can be used in restoration of desert lands.

Perennial Flowering Plants Sustain Natural Enemy Populations in Gobi Desert Oases of Southern Xinjiang, China.

Simple SummaryNatural habitats are essential providers of biological conservation services. The crucial role of the Gobi Desert, a dominant landscape of desert-oasis ecosystems in natural predator conservation is poorly understood, especially in southern Xinjiang, China’s Tarim Basin, where the Gobi Desert is directly adjacent to farmland and characterized by extremely sparse vegetation and more severe climatic conditions. In this context, we investigated the floral composition of the Gobi Desert and gauged the identity, relative abundance, and temporal dynamics of predatory insects associated with the prevailing plant species. We also explored whether certain plant traits and herbivore abundance are related to either natural enemy identity or relative abundance. Our results demonstrate that perennial flowering plants, such as Apocynum pictum (Apocynaceae), Phragmites communis (Poaceae), Karelinia caspia (Asteraceae), and Tamarix ramosissima (Tamaricaceae), are the dominant species of vegetation community in the Gobi Desert, and could sustain diversified arthropod predators, i.e., ladybeetles, spiders, and other natural enemies. This work not only informs sustainable pest management initiatives, but also shows how non-crop habitats at the periphery of agricultural fields underpin ecological resilience under adverse climatic conditions.Natural habitats play crucial roles in biodiversity conservation and shape the delivery of ecosystem services in farming landscapes. By providing diverse resources to foraging natural enemies, they can equally enhance biological pest control. In this study, we described the plant community and foliage-dwelling invertebrate predators within non-crop habitats of the Gobi Desert oases in southern Xinjiang, China. We assessed whether plant-related variables (i.e., species identity, flowering status) and herbivore abundance affect natural enemy identity and abundance. A total of 18 plant species belonging to 18 genera and 10 families were commonly encountered, with Apocynum pictum (Apocynaceae), Phragmites communis (Poaceae), Karelinia caspia (Asteraceae), and Tamarix ramosissima (Tamaricaceae) as the dominant species. Certain plant species (P. communis) primarily provide shelter, while others offer (floral, non-floral) food resources or alternative prey. Predatory ladybeetles and spiders were routinely associated with these plants and foraged extensively within adjacent field crops. Plant traits and herbivore abundance explained up to 44% (3%–44%) variation in natural enemy community and exhibited consistent, year-round effects. Among all plant species, A. pictum consistently had a significantly higher abundance of resident natural enemies, except for August 2019. Our study underlines how perennial flowering plants, such as A. pictum, are essential to sustain natural enemy communities and related ecosystem services in arid settings. This work not only informs sustainable pest management initiatives but also shows how non-crop habitats at the periphery of agricultural fields underpin ecological resilience under adverse climatic conditions.

Research Advances in Plant Physiology and Ecology of Desert Riparian Forests under Drought Stress

Under drought stress, desert riparian forest plants are highly self-regulating and have their own unique water use and regulation strategies, which can respond positively in several aspects such as physiology, ecology, and individual phenotypes when coping and adapting to the stresses brought by external environmental changes. In addition, as an important component of arid zone ecosystems, desert riparian forest plants maintain the cycling process of energy and material in desert areas. Therefore, it is of great ecological value to study the role played by desert riparian forest plants in desertification control and biodiversity conservation in arid zones. The purpose of this study is to provide basic data and scientific basis for the conservation, and restoration of desert riparian forests in the inland river basin of arid zone. In this paper, the physiological and ecological responses of desert riparian plants under drought stress were analyzed by reviewing the literature and focusing on the key scientific issues such as drought avoidance mechanisms, water use, and water redistribution, and the relationship between interspecific water competition and resource sharing of desert riparian plants. The results showed that: (1) In the inland river basin of arid zone, desert riparian plants show a mutual coordination of increasing soluble sugars, proline, malondialdehyde (MDA), and decreasing peroxidase (POD), to form a unique drought avoidance mechanism, and improve their drought tolerance by changing leaf stomatal conductance resulted from regulating abscisic acid (ABA) and cytokinin (CTK) content. (2) Desert riparian forest plants have their own unique water use and regulation strategies. When the degree of drought stress increased, Populus euphratica enhanced the water flow of dominant branches by actively sacrificing the inferior branches to ensure and improve the overall survival chances of the plant, while Tamarix ramosissima weaken hydraulic conductance, and increase subsurface material inputs by reducing plant height to cope with drought stress. (3) The root systems of desert riparian plants have hydraulic uplift and water redistribution functions, and, in the hydraulic uplift process of P. euphratica and T. ramosissima root systems, there is a possibility of assisting with other species in water utilization and the existence of a resource sharing mechanism.

Transcriptome analysis of Tamarix ramosissima leaves in response to NaCl stress.

Halophyte Tamarix ramosissima. Lcdcb (T. ramosissima) are known as the representative of Tamarix plants that are widely planted in salinized soil. However, molecular mechanisms towards salt tolerance and adaptation are largely rare. In this study, we carried out RNA-sequence and transcriptome analysis of T. ramosissima in response to NaCl stress, screened differentially expressed genes (DEGs) and further verified by qRT-PCR. Results showed that 105702 unigenes were spliced from the raw data of transcriptome sequencing, where 54238 unigenes were retrieved from KEGG, KOG, NR, and SwissProt. After 48 hours of NaCl treatment, the expression levels of 6374 genes were increased, and 5380 genes were decreased in leaves. After 168 hours, the expression levels of 3837 genes were up-regulated and 7808 genes were down-regulated. In particular, 8 transcription factors annotated to the KEGG Pathway were obtained, involving the WRKY and bZIP transcription family. In addition, KEGG pathway annotation showed that expression of 39 genes involved in ROS scavenging mechanisms were significantly changed, in which 21 genes were up-regulated and 18 genes were down-regulated after 48 hours as well as 15 genes were up-regulated and 24 genes were down-regulated after 168h. Simultaneously, the enzyme activities of SOD and POD were significantly enhanced under NaCl treatment, but the enzyme activity of CAT was not significantly enhanced. Moreover, WRKY, MYB and bZIP may participate in the process of salt resistance in T. ramosissima. This study provides gene resources and a theoretical basis for further molecular mechanisms of salt tolerance in T. ramosissima.

Foliar P-Fractions Allocation of Karelinia caspia and Tamarix ramosissima Are Driven by Soil and Groundwater Properties in a Hyper-Arid Desert Ecosystem.

The allocation patterns of foliar phosphorus (P) fractions across various vegetation types generally reflect the adaptability to P-impoverished environments. However, the allocation of foliar-P fractions within the desert herb Karelinia caspia (K. caspica) and shrub Tamarix ramosissima (T. ramosissima) in soils with different environment-P availability and the impact of soil and groundwater properties on foliar-P fractions allocation remain unclear. The foliar-P fractions (metabolites-P, nucleic acid-P, structural-P, and residual-P) of K. caspica and T. ramosissima and the properties of 0–60 cm deep soil under their canopy and groundwater were determined at four different environment-P sites. Results found that as environment-P availability decreased, both plants allocated the higher proportions of foliar-P to nucleic acid-P than to metabolites-P and structural-P. With the exception of residual-P, foliar-P fractions were markedly higher for K. caspica than T. ramosissima. Soil Olsen-P, NO3–-N, soil water content, electrical conductivity (EC), groundwater EC, and total dissolved solids (TDSs) played an important role in allocating foliar P-fractions for both K. caspica and T. ramosissima. Compared with K. caspica, the foliar-P fractions of T. ramosissima were more tightly bounded to groundwater than soil properties. Overall, these findings show how desert plants flexibility take advantage of the foliar-P in low environment-P availability and illustrate the foliar-P fractions allocation of desert plants is driven by soil and groundwater properties.

Inhibitory Effect of Tamarix ramosissima Extract on the Formation of Heterocyclic Amines in Roast Lamb Patties by Retarding the Consumption of Precursors and Preventing Free Radicals.

Tamarix ramosissima has been widely used as barbecue skewers for the good taste and unique flavor it gives to the meat, but the effects of T. ramosissima on heterocyclic amine (HA) formation in roast lamb are unknown. The influence of T. ramosissima extract (TRE) on HA formation, precursors’ consumption, and free radicals’ generation in roast lamb patties were elucidated by UPLC-MS, HPLC, and electron spin resonance (ESR) analysis, respectively. Six HAs were identified and compared with the control group; the total and polar HAs decreased by 30.51% and 56.92% with TRE addition at 0.30 g/kg. The highest inhibitory effect was found against 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine (PhIP) formation (70.83%) at 0.45 g/kg. The addition of TRE retarded the consumption of HA precursors, resulting in fewer HAs formed. The typical signal intensity of free radicals in roast lamb patties significantly decreased with TRE addition versus the control group (p < 0.05), and the higher the levels of the TRE, the greater the decrease in signal intensity. We propose that the inhibitory effects of TRE on HA formation, especially on polar HAs, were probably achieved by retarding the consumption of precursors and preventing free radicals from being generated in roast lamb patties. These findings provide valuable information concerning TRE’s effectiveness in preventing HA formation through both the precursor consumption and free radical scavenging mechanisms.

The Stem Sap Flow and Water Sources for Tamarix ramosissima in an Artificial Shelterbelt With a Deep Groundwater Table in Northwest China.

The shelterbelt forest between oases and the desert plays a vital role in preventing aeolian disasters and desertification in arid regions of northwest China. Tamarix ramosissima (T. ramosissima), a typical perennial and native xerophyte shrub in Northwest China, grows naturally and is widely used in building artificial shelterbelt forests. The balance between water consumption and the availability of water determines the survival and growth of T. ramosissima. How T. ramosissima copes with extremely low rainfall and a deep groundwater table remains unknown. To answer this, the transpiration and the water sources of T. ramosissima were investigated by the heat balance and oxygen isotopic analysis method, respectively. Our results show that the daily T. ramosissima stem sap flow (SSF) was positively correlated with air temperature (Ta), photosynthetically active radiation (PAR), and the vapor pressure deficit (VPD). We found no significant relationship between the daily SSF and soil moisture in shallow (0–40 cm) and middle (40–160 cm) soil layers. Oxygen isotope results showed that T. ramosissima mainly sources (>90%) water from deep soil moisture (160–400 cm) and groundwater (910 cm). Diurnally, T. ramosissima SSF showed a hysteresis response to variations in PAR, Ta, and VPD, which suggests that transpiration suffers increasingly from water stress with increasing PAR, Ta, and VPD. Our results indicate that PAR, Ta, and VPD are the dominant factors that control T. ramosissima SSF, not precipitation and shallow soil moisture. Deep soil water and groundwater are the primary sources for T. ramosissima in this extremely water-limited environment. These results provide information that is essential for proper water resource management during vegetation restoration and ecological reafforestation in water-limited regions.

MELISSOPALINOLOGICAL STUDY OF SOUTHERN BESSARABIA HONEY

Different natural and climatic zones, directions of agricultural production, ethnic and cultural features of agriculture, and reliefs of the regions of Ukraine are the result of a wide variety of vegetation. Ukraine occupies less than 6% of Europe’s area but owns about 35% of all its biodiversity. This leads to a considerable list of plants that are sources of nectar for the production of honey of different varieties. Ukraine produces classic monofloral varieties of honey, such as white acacia, rapeseed, linden, buckwheat, sunflower, as well as less common monofloral, such as mustard, clover, raspberry, bird’s-foot, phacelia, fireweed, goldenrod, sophora, honeydew. Today, regional polyfloral varieties of honey are also produced, such as Carpathian, steppe, Crimean, and other locally produced honey from reserves (for example, from Gomilshansky forests, Mezynsky reserve, Askanian meadows). A common way to identify the botanical and geographical origin of honey and identify its species is to study the pollen composition. This work was aimed to determine the pollen profile of spring honeys of Southern Bessarabia using the method of melissopalynology. Bessarabia is an ethnographic region with its own culture of agricultural production and natural and climatic conditions. The material of the study was samples of honey obtained in the apiaries of the Center for Ethnographic, Green, Rural Tourism, and Family Recreation Frumushika-Nova (Odessa region) in 2021. The pollen profile of honey was investigated using the author’s improved method of melissopalynological analysis. Identification of pollen grains was performed using the online database of pollen grains PalDat using a model nutrient medium. The pollen profile of spring honeys of Southern Bessarabia is represented by 30 morphotypes of pollen grains of different plant species, contains honeydew of natural origin and natural impurities (plant particles, wax, bee bodies). In the pollen profile of honey, no dominant (45% or more) pollen grains were detected, secondary – 6, insignificant – 21, inclusions – 3 morphotypes. This allows us to assert the polyflorality of the studied honey with the exception of white acacia, the dominant pollen of which may be 20% or more. Pollen grains of endemic species of steppe plants of Ukraine were found in the pollen profile of spring honeys of Southern Bessarabia (tamarix ramosissima, lathyrus pannonicus, rosa tesquicola, bifora radians, ailanthus altissima, ultus pumila, prunus tenella, viola occulta). The obtained results can be further used to identify the geographical origin of honey from this region. At the next stages of the research, it will be promising to determine the pollen profiles of summer honeys of Southern Bessarabia and other ethnographic regions of Ukraine.

Spectral classification, mapping and physical habitat implications of a riparian invasion by Tamarix ramosissima Ledeb. in the Touws River, Klein Karoo, South Africa

This paper investigates the invasion of a reach of the Touws River by the deciduous alien tree Tamarix ramosissima Ledeb. (Pink Tamarisk, Saltcedar). The objectives of the paper were to investigate the utility of a delta-normalised difference vegetation index (dNDVI) in evaluating the status, pattern and process of invasion, and to evaluate the implications of the invasion for riverscape morphodynamics and physical habitat structure and function. The spectral classification developed had an overall accuracy of 59.89%, omission error of 28.25%, and commission error of 11.86%. The classification of vegetation was used to quantify the aerial extent and pattern of invasion (currently at least 65.50% of the valley floor vegetation cover). Field observations and existing knowledge of seed dispersal mechanisms and germination constraints of the invasive tree were compared with those of the indigenous sweet thorn Vachellia karroo, to provide insight into invasion patterns and processes within the reach. The linear channel-flanking distribution of the invasion has the potential to alter reach hydrology and morphodynamics, which are key building blocks of physical habitat structure and function. The spectral classification approach demonstrated is relatively simple, has a strong biophysical basis in that it exploits a known, predictable and observable seasonal vegetation response that produces a clear spectral signature, and can be applied to long reaches of rivers impacted by alien vegetation invasions.