Vegetation communities in continental boreal wetlands along a salinity gradient: Implications for oil sands mining reclamation

Oil sands mining is a major disturbance to boreal landscapes in north-eastern Alberta, Canada. Freshwater peatlands dominate the landscape prior to mining, but the post-mining reclamation landscape will have wetlands that span a salinity gradient. Little is known about the native vegetation communities in subsaline and saline marshes in the boreal region, yet these communities offer the best potential for reclamation of wetlands after oil sands mining. The overall intent of this study is to provide information on natural wetland communities along a gradient of salinities that can be used to enhance oil sands wetland reclamation. Our specific study objectives were to: (1) characterize environmental conditions of industrial and natural wetlands, (2) characterize vegetation communities (composition and diversity) in these wetlands, (3) and explore how vegetation communities (composition and diversity) may be influenced by environmental conditions. We surveyed vegetation communities and environmental variables in 25 natural boreal wetlands along a salinity gradient and in 10 industrial marshes in the oil sands mining region. We observed an electrical conductivity (EC) range of 0.5-28 mS cm⁻¹ in the wetlands, indicating that salinity similar to or higher than anticipated for oil sands reclamation is naturally present in some boreal wetlands. We observed low species richness in both industrial and natural wetlands. There were 101 plant species observed in all the wetlands, with 82 species recorded in the natural wetlands and 44 species in industrial wetlands. At the plot level, richness decreased with increasing EC and pH, but increased with soil organic matter. Using Cluster Analysis and indicator species analysis we defined 16 distinct vegetation community types, each dominated by one or two species of graminoid vegetation. In general these communities resembled those of boreal or prairie marshes. Electrical conductivity, pH, and water depth were important factors correlating with community composition of the wetlands, however peat depth and soil organic content did not differ among community types. Not all community types were present in industrial wetlands, indicating that these communities may need to be planted to enhance overall diversity in future reclaimed oil sands wetlands.     

Anthropogenic transformation of soil and vegetation resulting from afforestation in southern steppes

Recent data (2006–2008) on characteristics of the vegetation and soils of the solonetzic complex in areas with tree failures within the Volgograd-Elista-Cherkessk forest shelterbelt have been compared with those obtained prior to afforestation (1950). The results show that the vegetation and soils have changed profoundly. Solonetzic agrozems in tree failure sites have been occupied by herbaceous plant communities similar in composition to natural communities. Anthropogenically altered soils formed under forest plantations have no natural analogs. The initial strongly saline shallow (crusty) solonetz soils with a chloride-sulfate or sulfate-chloride composition of salts have transformed into slightly saline solonetzic and solonchakous agrozems with sodium sulfate salinity or with increased alkalinity in the middle of the soil profile and a dealkalized arable horizon.     

Influence of salinity on methanogenesis and associated microflora in tropical rice soils

In a laboratory incubation study, methane (CH4) production in two saline soils and a nonsaline soil sample was investigated under flooded conditions. Mean CH4 production was remarkable (630.86 ng CH4/g) in nonsaline alluvial soil, but low (12.97 ng CH4/g) in acid sulfate saline (Pokkali) soil which was attributed to the high sulfate content of the later. CH4 production was also low in the coastal saline (Canning) soil (142.36 ng CH4/g) but increased upon leaching the soil of its salt content. Addition of salts to the nonsaline alluvial soil at 4, 8, 16 and 20 dS/m progressively decreased CH4 production. The inhibition of CH4 production was related to low microbial activities as reflected by decreased microbial biomass C and low soil microbial population including that of methanogens.     

Restoration of belowground fungal communities in reclaimed landscapes of the Canadian boreal forest

The trajectory of forests establishing on reclaimed oil sands mines in the Canadian boreal forest is uncertain. Soil microbes, namely mycorrhizal fungi, partly underlie successional trajectories of plant communities, yet their role in restoration is often overlooked. Here, we tested the relative importance of common management tools used in restoration—species planted and soil placement—on the recovery of ectomycorrhizal fungal communities over 4 years. Importantly, we further compared the community assembly of fungi on reclaimed landscapes to that in reference ecosystems disturbed to different degrees. This latter test addresses whether disturbance intensity is more important than common management interventions to restore fungal communities in these ecosystems. Three main findings emerged. (1) The effect of tree species planted and soil placement on ectomycorrhizal fungal communities establishing on reclaimed landscapes was dynamic through time. (2) Disturbances that remove or disrupt the organic layer of soils substantially affect the composition of ectomycorrhizal fungal communities. (3) Shifts in the community composition of ectomycorrhizal fungi were driven to a greater extent by disturbance severity than either tree species planted or soil placement.     

塔里木盆地大叶白麻的土壤生境类型

 本文以新疆塔里木盆地大叶白麻在不同地形位置、土壤盐分含量和地下水位深浅等生态因子综合作用下,形成的土壤适应性反应为根据,结合所在土壤上的大叶白麻植株形态、生长状况和化学成分含量等特点,将该盆地大叶白麻的土壤划分为河漫滩草甸土、高水位盐土、中水位盐土、低水位盐土和砂化荒漠森林土五种生境类型;并建议按土壤生境类型来合理开发、利用和保护这一野生植物资源。     

Projected climate change effects on Alberta's boreal forests imply future challenges for oil sands reclamation

Climate change will drive significant changes in vegetation cover and also impact efforts to restore ecosystems that have been disturbed by human activities. Bitumen mining in the Alberta oil sands region of western Canada requires reclamation to “equivalent land capability,” implying establishment of vegetation similar to undisturbed boreal ecosystems. However, there is consensus that this region will be exposed to relatively severe climate warming, causing increased occurrence of drought and wildfire, which threaten the persistence of both natural and reclaimed ecosystems. We used a landscape model, LANDIS‐II, to simulate plant responses to climate change and disturbances, forecasting changes to boreal forests within the oil sands region. Under the most severe climate forcing scenarios (representative concentration pathway [RCP] 8.5) the model projected substantial decreases in forest biomass, with the future forest being dominated by drought‐ and fire‐tolerant species characteristic of parkland or prairie ecosystems. In contrast, less extreme climate forcing scenarios (RCPs 2.6 and 4.5) had relatively minor effects on forest composition and biomass with boreal conifers continuing to dominate the landscape. If the climate continues to change along a trajectory similar to those simulated by climate models for the RCP 8.5 forcing scenario, current reclamation goals to reestablish spruce‐dominated boreal forest will likely be difficult to achieve. Results from scenario modeling studies such as ours, and continued monitoring of change in the boreal forest, will help inform reclamation practices, which could include establishment of species better adapted to warmer and drier conditions.     

The role of soil pH in linking groundwater flow and plant species density in boreal forest landscapes

In hilly boreal landscapes topography governs groundwater flow which strongly influences soil development, and thus vegetation composition. Soil pH is known to correlate well with plant species density and composition, but in boreal forests this relationship has been little studied. Previously, we successfully used a topography-based hydrological index, the topographical wetness index (TWI), as an approximation of the variation in groundwater flow to predict local plant species density in a boreal forest landscape. Data on species indicator values demonstrated that soil pH can be an important soil variable linking groundwater flow and plant species density. In the present paper we explore this link by relating measured soil pH to species numbers of vascular plants and TWI in 200-m² plots within two boreal forest landscapes, differing in average soil pH. The two landscapes showed almost identical relationships between plant species number and soil pH, implying that this relationship is robust. The landscapes also had similar relationships between soil pH and TWI as well as between plant species number and TWI except at high TWI values, which indicate groundwater discharge areas. In these areas soil pH and plant species numbers were higher in the high-pH landscape at any given TWI value. We conclude that for predictive mapping of the species density of vascular plants in boreal forests, soil pH is a major factor. However, TWI as a measure of groundwater flow is a practical alternative predictor.     

Plant community development following reclamation of oil sands mines using four cover soil types in northern Alberta

Understanding the effects of reclamation treatments on plant community development is an important step in setting realistic indicators and targets for reclamation of upland oil sands sites to forest ecosystems. We examine trends in cover, richness, evenness, and community composition for four cover soil types (clay over overburden, clay over tailings sand, peat‐mineral mix over overburden, and peat‐mineral mix over tailings sand) and natural boreal forests over a 20 year period in the mineable oil sands region of northern Alberta, Canada. Tree, shrub, and nonvascular plant species cover showed similar increases over time for all reclamation treatments, with corresponding declines in forb and graminoid cover with time. These trends resemble those in the natural boreal forests of the region and the trajectory of community development for the reclamation treatments appears to follow typical early successional trends for boreal forests. Species richness and diversity of natural forest differed significantly from reclamation treatments. Nonmetric multidimensional scaling ordination and multi‐response permutation procedure revealed that species composition was not affected by reclamation treatment but clearly differed from natural forest. Analysis of species co‐occurrence indicated random plant community assembly following reclamation, in contrast to a higher proportion of nonrandom plant community assembly in natural forests. Thus, reclaimed plant communities appear to be unstructured through year 20 and assembly is still in progress on these reclaimed sites.     

Dynamics of seasonal plant growth in halophytic meadows taking into account the temperature factor and soil salinity level

A mathematical model has been constructed to describe the growth dynamics of various plant communities of halophytic meadows depending on the temperature factor and degree of soil salinity. Field investigation of the yields of halophytic meadow plant communities were performed in the coastal area of Kurinka Lake in the Altaiskii district of the Republic of Khakasia in 2004 and 2006. The results of field investigations and model studies show that there is a correlation between plant growth and air temperature for plant communities growing on soils with the lowest and medium salinity levels. It was proven in model studies that for the plant communities that grow on highly saline (3.58%) soils, not only air temperature but also the salinity level of the soil should be taken into account.     

Nitrogen mineralization rates in salinevs. salt-amended soils

Studies were conducted to compare N mineralization rates in salt-amended nonsaline soils to naturally-occurring saline soils. NaCl, CaCl₂, and Na₂SO₄ were added to nonsaline soils at rates that produced electrical conductivities of the saturation extracts (EC_e) of 5, 10, 15, and 20 dS m⁻¹. Saline soils with similar properties were leached to the same EC_c levels. N mineralization in the Chino soil was inhibited by salt addition, particularly with sodium and calcium chlorides. In the Domino soil there was some inhibition of N mineralization with the chloride salts, but enhancement with Na₂SO₄ was observed. Nitrification in both soils was more sensitive to salt addition than ammonification. N mineralization occurred more slowly in both leached saline soils compared to the salt-amended soils. Leached saline soils often accumulated greater amounts of inorganic N compared to their native saline counterparts, particularly with the 5 dS m⁻¹ Chino soil (native, 44 dS m⁻¹) and with the 5, 10, 15 and 20 dS m⁻¹ Domino soils (native, 32 dS m⁻¹). Kinetic parameters were estimated by the linear least squares (LLS) and the nonlinear least squares (NLLS) methods. Generally, the LLS transformation estimated greater values of potentially mineralizable N (N_o) and lower rate constants (k). With the NLLS equation, N_o values for the leached saline soils were usually lower, and k values usually higher than in the salt-amended soils. The nonsaline controls generally had the highest N_o and lowest k estimates. Average LLS rate constants for the salt-amended and leached saline soils were 0.055 and 0.083 for the Chino, and 0.104 and 0.137 week⁻¹, respectively, for the Domino soils. With the NLLS equation, average k values for the salt-amended and leached saline soils were 0.087 and 0.089 for the Chino, and 0.181 and 0.387 week⁻¹, respectively, for the Domino soils. These results suggest that N mineralization rates obtained in salt-amended nonsaline soils may not be representative of those in naturally-occurring saline soils.     

The influence of soil on vegetation structure and plant diversity in different tropical savannic and forest habitats

Aims Soil plays an important role in the formation and heterogeneity of habitats and thus can cause changes in vegetation structure and plant diversity. The differentiation between Cerrado/savanna and forest is well known, but the relationship between soil and habitats from savannic or forest formations still needs to be better understood, particularly in tropical ecotonal areas. We studied the association between attributes of plant communities, namely structure and diversity, and physicochemical characteristics of soils in the Caatinga domain at the transition to Cerrado in Brazil.Methods Chemical and physical analyses of soils were performed in samples of 38 plots from savannic formations and 30 plots from forest formations. Vegetation was characterized floristically and structurally in all plots, five habitats being assessed in each plant formation. Soil features and vegetation parameters were highly distinct among the different habitats.Important findings In general, forest habitats were more nutrient rich than savannic formation. Furthermore, soil variables showed effects both on vegetation structure and on its species diversity, more pronouncedly in the savannic formations. Habitats were structurally distinct, and diversity differed between savannic and forest communities; however, a higher differentiation occurred when the savannic formation habitats were compared among them. Although plant diversity did not differ among forest formation habitats, soil attributes showed a close relationship with edaphic factors and can contribute for similar vegetation. The soil–vegetation relationship in highly diverse ecotonal landscapes is important from the conservation biology point of view and aid in the execution of proactive plans for the maintenance of biodiversity. Thus, we noticed that diversity and soil behaves distinctly between savannic and forest communities.     

Saline stress tolerance partly matches with habitat preference in ground‐living wolf spiders

Salinity interacts with many physiological functions and therefore probably influences the distribution of terrestrial fauna in tidal flooded salt marshes. The present study tests the hypothesis that the physiological tolerance of stenotopic wolf spiders for saline conditions at least partially determines their occurrence throughout salt‐marsh and nonsaline habitats. The duration of survival of three stenotopic wolf spider species (Araneae: Lycosidae) with different habitat preferences is compared in a controlled laboratory experiment. The forest‐dwelling Pardosa saltans, the salt‐marsh resident Pardosa purbeckensis and its sister species the inland‐living Pardosa agrestis are exposed to experimental conditions with different levels of salinity. Individuals (45 males and 20–45 females per treatment) are placed in individual air‐tight boxes filled with water‐saturated sand. Three levels of salinity are tested: nonsaline (0‰), medium saline (33–35‰) and highly saline (66–70‰). Contents of carbon, hydrogen and nitrogen and the molar ration carbon/nitrogen remain constant over time and do not differ among salinity treatments, indicating that starvation effects on survival, if any, are similar for all treatments. Conversely, body water significantly decreases over time and differs among salinity treatments, in accordance with patterns of survival. Conforming to their habitat preference, the survival of P. saltans and P. agrestis decreases quickly under highly saline conditions. Pardosa purbeckensis, however, has a high survival under both saline and nonsaline conditions. The duration of survival of females is significantly lower than that of males of P. saltans and P. purbeckensis. Durations of survival of ground‐living wolf spiders exposed to salinity partly match their habitat distribution but do not explain the restriction of salt‐marsh species to saline habitats.     

Plant Growth-Promoting Bacteria Facilitate the Growth of Barley and Oats in Salt-Impacted Soil: Implications for Phytoremediation of Saline Soils

Plant growth-promoting bacteria (PGPB) strains that contain the enzyme 1-amino- cyclopropane-1-carboxylate (ACC) deaminase can lower stress ethylene levels and improve plant growth. In this study, ACC deaminase-producing bacteria were isolated from a salt-impacted (～50 dS/m) farm field, and their ability to promote plant growth of barley and oats in saline soil was investigated in pouch assays (1% NaCl), greenhouse trials (9.4 dS/m), and field trials (6–24 dS/m). A mix of previously isolated PGPB strains UW3 (Pseudomonas sp.) and UW4 (P. sp.) was also tested for comparison. Rhizobacterial isolate CMH3 (P. corrugata) and UW3+UW4 partially alleviated plant salt stress in growth pouch assays. In greenhouse trials, CMH3 enhanced root biomass of barley and oats by 200% and 50%, respectively. UW3+UW4, CMH3 and isolate CMH2 also enhanced barley and oat shoot growth by 100%–150%. In field tests, shoot biomass of oats tripled when treated with UW3+UW4 and doubled with CHM3 compared with that of untreated plants. PGPB treatment did not affect salt uptake on a per mass basis; higher plant biomass led to greater salt uptake, resulting in decreased soil salinity. This study demonstrates a method for improving plant growth in marginal saline soils. Associated implications for salt remediation are discussed.     

Vegetation and ecological gradients in abandoned salt pans in western France

Abstract. Salt marshes along the Atlantic coast of France have been converted into solar salt pans since the 7th century. Salt production declined strongly from the 18th century onward, leading to the abandonment of many of these salt pans. High soil salinity is a residue from the original salt production and varies among salt pans according to time since abandonment, the current flooding regime and the effect of drainage measures. The relationships between the plant communities and seven environmental variables were investigated by Detrended Correspondence Analyses (DCA). Duration of flooding, electric conductivity and sodium saturation were most strongly related to variation in vegetation. The Heleo‐chareto‐Hippuridetum vulgaris and the Caricetum ripariae occur in lagoons with slightly saline soil that are flooded for the longest time period; the Scirpetum maritimi compacti occurs in salt pans with saline soil flooded for a long period; the Alopecuro‐Juncetum gerardii occurs on saline soil where flooding is of short duration whereas the Carici‐Lolietum perennis is never flooded and occurs on only slightly saline soil. Soil salinity and duration of flooding provide a satisfactory explanation of the variation in species composition in abandoned salt pans but land‐use practices, especially grazing, have to be taken into account to fully understand their floristic composition.     

The Role of the Forest Soil Propagule Bank in Assisted Natural Recovery after Oil Sands Mining

This study was undertaken to determine if use of stratified organic layers of intact litter, fragmented litter, and humus on the forest floor (LFH) improves establishment of upland native boreal plant species during oil sands reclamation in Alberta, Canada. The abundance and composition of vascular plant species in the soil propagule bank were determined for LFH and peat materials before salvage from donor sites and 18 months after application on the receiver site. Applications of 10 and 20 cm were evaluated. Various soil properties were assessed to determine impacts of donor materials. In the growth chamber, LFH donor material had significantly more plant species emerge (37) from the propagule bank than did peat donor material (19). In the field, LFH treatments had significantly higher species richness (49, 47, 24, and 25 species for LFH 10 cm, LFH 20 cm, peat 10 cm, and peat 20 cm treatments, respectively), plant abundance, and soil nutrients than peat treatments. Application thickness of peat had little effect, but 20 cm of LFH was more beneficial for plant community establishment than 10 cm. LFH treatments had narrower C:N ratios and higher soluble potassium and available phosphorus than peat. Applying 10 versus 20 cm of donor material increased admixing of fine‐textured subsoil, reducing organic carbon, nitrogen, and potassium; these effects were greater for LFH than peat treatments. Thus, addition of LFH aids in creating diverse ecosystems on reclaimed upland landscapes by providing a source of propagules for revegetating upland boreal forest communities and improving nutrient availability for plants.     

Community composition and functioning of denitrifying bacteria from adjacent meadow and forest soils

We investigated communities of denitrifying bacteria from adjacent meadow and forest soils. Our objectives were to explore spatial gradients in denitrifier communities from meadow to forest, examine whether community composition was related to ecological properties (such as vegetation type and process rates), and determine phylogenetic relationships among denitrifiers. nosZ, a key gene in the denitrification pathway for nitrous oxide reductase, served as a marker for denitrifying bacteria. Denitrifying enzyme activity (DEA) was measured as a proxy for function. Other variables, such as nitrification potential and soil C/N ratio, were also measured. Soil samples were taken along transects that spanned meadow-forest boundaries at two sites in the H. J. Andrews Experimental Forest in the Western Cascade Mountains of Oregon. Results indicated strong functional and structural community differences between the meadow and forest soils. Levels of DEA were an order of magnitude higher in the meadow soils. Denitrifying community composition was related to process rates and vegetation type as determined on the basis of multivariate analyses of nosZ terminal restriction fragment length polymorphism profiles. Denitrifier communities formed distinct groups according to vegetation type and site. Screening 225 nosZ clones yielded 47 unique denitrifying genotypes; the most dominant genotype occurred 31 times, and half the genotypes occurred once. Several dominant and less-dominant denitrifying genotypes were more characteristic of either meadow or forest soils. The majority of nosZ fragments sequenced from meadow or forest soils were most similar to nosZ from the Rhizobiaceae group in alpha-Proteobacteria species. Denitrifying community composition, as well as environmental factors, may contribute to the variability of denitrification rates in these systems.     

The Effects of Saline Water Drip Irrigation on Tomato Yield,Quality, and Blossom-End Rot Incidence --- A 3a Case Study in the South of China

Saline water resources are abundant in the coastal areas of south China. Most of these resources still have not been effectively utilized. A 3-year study on the effects of saline water irrigation on tomato yield, quality and blossom-end rot (BER) was conducted at different lower limits of soil matric potential (-10 kPa, -20 kPa, -30 kPa, -40 kPa and -50 kPa). Saline water differing in electrical conductivity (EC) (3 dS/m, 4 dS/m, 4.5 dS/m, 5 dS/m and 5.5 dS/m) was supplied to the plant after the seedling establishment. In all three years, irrigation water with 5.5 dS/m salinity reduced the maximum leaf area index (LAI_m) and chlorophyll content the most significantly when compared with other salinity treatments. However, compared with the control treatment (CK), a slight increase in LAI_m and chlorophyll content was observed with 3~4 dS/m salinity. Saline water improved tomato quality, including fruit density, soluble solid, total acid, vitamin C and the sugar-acid ratio. There was a positive relationship between the overall tomato quality and salinity of irrigation water, as analyzed by principal component analysis (PCA). The tomato yield decreased with increased salinity. The 5.5 dS/m treatment reduced the tomato yield (Y_t) by 22.4~31.1%, 12.6~28.0% and 11.7~27.3%, respectively in 2012, 2013 and 2014, compared with CK. Moreover, a significant (P≤0.01) coupling effect of salinity and soil matric potential on Y_t was detected. Saline water caused Y_t to increase more markedly when the lower limit of soil matric potential was controlled at a relatively lower level. The critical salinity level that produced significant increases in the BER_i was 3 dS/m~4 dS/m. Following the increase in BER_i under saline water irrigation, marketable tomato yield (Y_m) decreased by 8.9%~33.8% in 2012, 5.1%~30.4% in 2013 and 10.1%~32.3% in 2014 compared with CK. In terms of maintaining the Y_t and Y_m, the salinity of irrigation water should be controlled under 4 dS/m, and the lower limit of soil matric potential should be greater than -20 kPa.     

Woody Debris Amendment Enhances Reclamation after Oil Sands Mining in Alberta,Canada

Mining disturbs large forested areas around the world, including boreal forests after oil sands mining in Canada. Industrial companies are expected to reclaim degraded land to ecosystems with equivalent land capability. This research showed the value of woody debris for reclamation of dramatically disturbed landscapes with a forest ecosystem end land use. Adding woody debris during reclamation can facilitate recovery of flora, soil nutrient cycling and water and nutrient holding capacity. Combined with forest floor material, woody debris can provide native plant propagules that would be otherwise commercially unavailable. Sites with and without woody debris on forest floor material containing identifiable litter (L), fragmented and fermented litter (F), and humus (H) (LFH), and peat mineral soil mix (peat) cover soils were studied. Within 2 years, woody debris decreased bare ground and created microsites which were positively associated with greater vegetation cover and woody plant density. Woody debris treatments had lower soil available nitrate and soil under woody debris had a lower temperature range and higher soil volumetric water content than control treatments without woody debris. Woody debris did not affect first year microbial biomass carbon or mycorrhizae, but both were greater on LFH than peat cover soil. LFH was associated with lower bare ground and greater vegetation cover, species richness, and soil phosphorus and potassium than peat cover soil, which had greater soil sulfate .     

Classification and ecology of the mid‐seral Picea mariana forests of British Columbia

Abstract. We sampled vegetation and soils of, and classified mid‐seral, even‐aged, fire‐origin, upland Picea mariana ecosystems in the Boreal White & Black Spruce and Sub‐boreal Spruce zones of British Columbia, Canada. We applied multi‐variate and tabular methods to analyse and synthesize the data from 121 plots according to the methods of biogeoclimatic ecosystem classification. We delineated seven basic vegetation units and described their vegetation and environmental features. However, the delineated units could not be related to neither of the taxonomies proposed for the North American boreal forest communities. Although species‐poor, the under‐storey vegetation in the sampled ecosystems provided for a sufficient floristic differentiation, which matched well the major edaphic differences between the units. The classification of mid‐seral boreal ecosystems may be more useful that based on old‐growth stands that are infrequent or lacking in the landscape due to wildfires.     

Comparison of Distichlis spicata and Suaeda aegyptiaca in response to water salinity: Candidate halophytic species for saline soils remediation

Distichlis spicata and Suaeda aegyptiaca are two potential halophytic plant species for bioremediation of salt degraded soils, and development of saline agriculture. The physiological responses of the species to different levels of salinity (EC 0, 12, 24, 36, and 48 dS/m) in a controlled environment experiment were studied. Both species showed a high level of tolerance to elevated concentrations of salt in the irrigation water. The shoot fresh and dry weights in S. aegyptiaca increased till 36 dS/m and were sustained under 48 dS/m while in D. spicata, both parameters decreased as salinity increased. Glycine betaine accumulation did not change in D. spicata with increasing salinity, whereas proline content revealed a marked increase of 7.13 fold in 48 dS/m salinity compared to the control, which showed its critical osmoprotection role in the plant. In S. aegyptiaca, both osmolytes content significantly increased at high salinity levels (36 and 48 dS/m) up to 3.22 and 2.0 folds, respectively. Overall, S. aegyptiaca had a better potential of Na⁺ phytoremediation, and tolerated higher salinity compared to D. spicata. In contrast, the vigorous root and rhizome growth in D. spicata made it a proper solution for protecting the soils against further erosion under saline conditions.