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.     

Influence of salt stress on propagation,growth and nutrient uptake of typical aquatic plant species

Anthropogenic activities and natural causes contribute to an increase in the area and degree of degraded saline wetlands in arid/semi‐arid and coastal regions. The objective of this study was to determine the salt tolerance of the seven aquatic plant species Phragmites australis, Arundo donax, Canna indica, Scirpus validus, Alternanthera philoxeroides, Phyllostachys heteroclada and Potederia cordata during asexual reproduction and continuous growth. The species were exposed to five salinity treatments from 0.3 (control) to 20 dS m^?1 during a 30 day experiment. Data were collected on asexual reproduction and growth, chlorophyll content in leaves, Na⁺ and K⁺ concentrations, total nitrogen (TN) and total phosphorus (TP) concentrations in above‐ground biomass (AGB) and below‐ground biomass (BGB). The results showed that: 1) increase in salinity (especially at a salinity level of EC ≥15 dS m^?1) generally inhibited the capacity for asexual reproduction and reduced the chlorophyll content of leaves; 2) total dry biomass of plants was significantly negatively related to asexual reproduction; 3) species‐specific salt tolerance mechanisms were reflected by the Na⁺ and K⁺ concentrations and Na⁺/K⁺ ratios in different parts of the plants; and 4) the absorption of TN and TP were inhibited at high salinity (i.e. EC = 20 dS m^?1) in AGB and BGB of most tested plant species. However, salinity may enhance plant uptake of TN and TP under certain conditions (e.g. EC at 5, 10 and 15 dS m^?1). In general, as compared to the other species tested, giant reed A. donax and alligator weed A. philoxeroides showed relatively high asexual reproduction and growth capacity under high salt stress, and these species should thus be considered as candidates for restoration of degraded saline wetlands and/or for decontaminating saline wastewater.     

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.     

Water relations and leaf gas exchange properties in some elite canola (Brassica napus) lines under salt stress

In order to examine whether growth of eight genetically diverse canola (Brassica napus) lines under salt stress is positively associated with their rate of photosynthesis and other gas exchange related attributes, 20‐day old plants of all eight lines were subjected to salinised soil containing 2.4 dS m^?1 NaCl (control), 4 dS m^?1 NaCl, 8 dS m^?1 NaCl or 12 dS m‐¹ NaCl. The lines DGL (non canola) and Dunkeld were found to be salt tolerant and Rainbow and Cyclon salt sensitive with regard to shoot dry matter production and seed yield under saline conditions. In most of the lines there was a negative relationship between growth and net CO₂ assimilation rate. For example, the salt sensitive line Cyclon was the lowest and Con‐III the highest, and the salt tolerant line Dunkeld intermediate in net CO₂ assimilation rate under salt stress. Stomatal conductance was found to be lower in the salt sensitive line Cyclon, followed by the salt tolerant line Dunkeld along with Oscar. Water use efficiency estimated as Pn/E was moderate in the salt sensitive line Cyclon and the salt tolerant line Dunkeld. In conclusion, high salt tolerance of Dunkeld and DGL (non‐canola) was not positively associated with net CO₂ assimilation rate or Pn/E.     

Variability of the inflorescence morphology of Carex spicata (Cyperaceae) and its implication to taxonomy

Plants growing in different kinds of habitats are expected to show high morphological plasticity. Carex spicata Huds. occurs in different plant communities and shows distinct morphological variability of the inflorescences. Field observations carried out in different plant communities permitted us to hypothesize that the morphological variability of C. spicata inflorescences may to some degree be the result of the habitat. The objective of this study was to test that hypothesis for C. spicata by collecting inflorescences and measuring their morphological features from several populations in each of six plant communities: Agropyro‐Urticetum dioiceae, Arrhenatheretum elatioris, Lolio‐Cynosuretum, Lolio‐Plantaginetum, Trifolio‐Agrimonietum, and Stellario‐Deschampsietum. The following inflorescence features were analyzed: length of the lowest spikelet, distance between two lowest spikelets, length of inflorescence, number of spikelets, and length proportion of the lowest spikelet to the distance between the two lowest spikelets. We found that all analyzed morphological characters differed significantly among the plant communities. Furthermore, we found significant differences among populations within the six plant communities. Moreover, C. spicata inflorescences often have morphological features (i.e. a less crowded inflorescence with a relatively large distance between the two lowest spikelets) similar to the closely related species C. muricata L. Thus, the limited diagnostic value of inflorescence crowding, especially in vegetative or early fruiting phases, suggests that the taxonomic importance of this character should be reconsidered.     

Evaluation of Spinacia oleracea (L.) for phytodesalination and augmented production of bioactive metabolite, 20-hydroxyecdysone

In this study, adaptive features of Spinacia oleracea to different levels of salinity, its use in desalination and production of 20-Hydroxyecdysone were studied. Plants showed survival up to EC 12 dS/m with reduced growth as compared with control. Net photosynthesis rate, transpiration, stomatal conductance, and water use efficiency of salt treated plants declines with increasing salinity stress. Higher antioxidant enzyme activities and compatible solutes accumulation were observed in salt treated plants as function of osmotic adjustment. Significant Na⁺ sequestration and Na/K ratio were noted with increase in salt stress in comparison to the control. Since the plant accumulates a bioactive, secondary metabolite 20-Hydroxyecdysone (20E), we observed significant 20E content in plants grown at EC 4–12 dS/m in comparison to control. Furthermore, a preliminary field experiment, showed significant reduction in the soil electrical conductivity by 1.8 ds/m after 90 days of plant growth with Na⁺ sequestration in plant biomass. Subsequent to this growth period, the phytodesalinized soil supported the significant growth of a glycophyte (rice). Our results suggest that S. oleracea can adapt to saline conditions with antioxidant defense and osmotic adjustment. The plant can be used as a potential candidate for desalination and also for enhanced production of 20-Hydroxyecdysone.     

Comparative demography of two giant caulescent rosettes (Espeletia timotensis and E. spicata) from the high tropical Andes

Using field data from previous studies we built matrix models for two populations of giant rosettes, Espeletia timotensis Cuatrec. and E. spicata Sch. Bip. Wedd., from the Andes Cordillera in Mérida, Venezuela. We analysed the models and calculated population growth rate (λ), sensitivities, elasticities and the sensitivity of the elasticities to changes in the vital rates. The analysis showed that the two species behave alike in general demographic terms. In both models, population growth rate is positive and sensitivities of λ to changes in vital rates decrease markedly in this order: plant establishment, progression of juvenile–adult, germination and survival. The relative contributions of vital rates to λ (elasticities) are very similar to those of other woody plant species: a higher contribution of survival and a very low contribution of fecundity. Transition from seedling to juvenile is most important and the younger established stages (juveniles and young adults) play a predominant demographic role in both populations. Seed banks and older adults are playing a relatively minor role in the dynamics of both populations. However, they may be important in relation to unpredictable, favourable or detrimental events. Perturbation analysis of elasticities showed that increasing the rate of plant establishment will decrease the relative importance of stasis. We conclude that both species are demographically very close, and similar to other long‐lived woody plant species. However, the two species differ in the role of the seed bank, which seems more important in the demography of E. spicata than in E. timotensis.     

Impact of grasshoppers and an invasive grass on establishment and initial growth of restoration plant species

Exotic plant invasion can have dramatic impacts on native plants making restoration of native vegetation at invaded sites challenging. Though invasives may be superior competitors, it is possible their dominance could be enhanced by insect herbivores if native plants are preferred food sources. Insect herbivory can regulate plant populations, but little is known of its effects in restoration settings. There is a need to better understand relationships between insect herbivores and invasive plants with regard to their combined potential for impacting native plant establishment and restoration success. The objective of this study was to assess impacts of grasshopper herbivory and the invasive grass Bromus tectorum (cheatgrass) on mortality and growth of 17 native plant species used in restoration of critical sagebrush steppe ecosystems. Field and greenhouse experiments were conducted using moderate densities of a common, generalist pest grasshopper (Melanoplus bivittatus). Grasshoppers had stronger and more consistent impacts on native restoration plants in field and greenhouse studies than cheatgrass. After 6 weeks in the greenhouse, grasshoppers were associated with 36% mortality over all native restoration species compared to 2% when grasshoppers were absent. Herbivory was also associated with an approximately 50% decrease in native plant biomass. However, effects varied among species. Artemisia tridentata, Chrysothamnus viscidiflorus, and Coreopsis tinctoria were among the most negatively impacted, while Oenothera pallida, Pascopyrum smithii, and Leymus cinerus were unaffected. These findings suggest restoration species could be selected to more effectively establish and persist within cheatgrass infestations, particularly when grasshopper populations are forecasted to be high.     

Effect of salinity on mycorrhizal onion and tomato in soil with and without additional phosphate

Summary Vesicular-arbuscular mycorrhizal fungi (VAM) are known to increase plant growth in saline soils. Previous studies, however, have not distinguished whether this growth response is due to enhanced P uptake or a direct mechanism of increased plant salt tolerance by VAM. In a glasshouse experiment onions (Allium cepa L.) were grown in sterilized, low-P sandy loam soil amended with 0, 0.8, 1.6 mmol P kg^–1 soil with and without mycorrhizal inoculum. Pots were irrigated with saline waters having conductivities of 1.0, 2.8, 4.3, and 5.9 dS m^–1. Onion colonized withGlomus deserticola (Trappe, Bloss, and Menge) increased growth from 394% to 100% over non-inoculated control plants when soil P was low ( 0.2 mmol kg^–1 NaHCO₃-extractable P) at soil saturation extract salinities from 1.1 dS m^–1 to 8.8 dS m^–1. When 0.8 and 1.6 mM P was added no dry weight differences due to VAM were observed, however, K and P concentrations were higher in VAM plants in saline treatments.Glomus fasciculatum (Gerdeman and Trappe) andGlomus mosseae (Nicol. and Gerd.) isolates increased growth of VAM tomato 44% to 193% in non-sterilized, saline soil (10 dS m^–1 saturation extract) despite having little effect on growth in less saline conditions when soil P was low. Higher tomato water potentials, along with improved K nutrition by VAM in onion, indicate mechanisms other than increased P nutrition may be important for VAM plants growing under saline stress. These effects appear to be secondary to the effects of VAM on P uptake.     

Morphological variability of Carex spicata Huds. utricles among plant communities

Differentiation in the size and number of seeds among populations or particular individuals of a given species may depend on genetic features and environmental conditions. The objective of our study was to answer two questions: whether any differences exist in the size and shape of utricles among Carex spicata populations growing in several plant communities and whether the hypothesized differences remain constant in ‘common garden’ conditions (i.e. if the sedges grown in different plant communities are evolving distinctly separate ecotypes). We studied utricle morphological traits (projected area, width, length, W/L ratio and projected perimeter) and number of utricles per spike collected from plants grown in five different plant communities (natural sites) and from plants transferred to common garden conditions. C. spicata utricles showed significant variability of morphological traits that depended on the plant community of origin. Among five plant communities, the largest utricles were found in Agropyron repens–Urtica dioica and Convolvulo arvensis–Agropyretum repentis communities, while the smallest ones were in plants from the Lolio-Plantaginetum community. The similarity of the analyzed populations regarding sedge utricle traits corresponded to the similarity of plant communities where the populations had grown. Moreover, the differences in utricle traits collected from natural conditions remained stable in common garden conditions. This indicated that differences in traits among utricles had a physiological dependence on different biotope conditions or different interspecific interactions prevailing in the particular plant communities. The relationship between the similarities in the diaspores of the populations studied and the similarities in the ecological conditions of the communities may also indicate that the variability of utricles is important for evolution and adaptation.The results support the hypothesis that C. spicata populations in different communities are producing separate ecotypes, i.e. specific species forms with genetically fixed traits adapted to narrowly determined habitat conditions.     

Testing the cultivar vigor hypothesis: comparisons of the competitive ability of wild and cultivated populations of Pascopyrum smithii along a restoration chronosequence

Restoration practitioners often rely on seeds of widely available cultivars representing native species but nonlocal germplasm. Cultivation improves the supply of plant materials and minimizes revegetation costs, but can also favor agronomic traits, and resulting vigor may affect the competitive ability and long‐term persistence of cultivated genotypes at restoration sites. We compared cultivated, restored, and wild populations of Pascopyrum smithii (western wheatgrass) in a greenhouse study to test the extent to which cultivars outcompete local plants in biomass production, and to determine if morphological differences (including height and number of leaves) among cultivated and wild populations persist at restoration sites over time. We found evidence of vigor and greater competitive ability of cultivars in seed mass, growth rate, plant height, and biomass and this advantage occurred when plants were grown alone or in competition with other seed sources. Cultivar vigor persisted at restoration sites over 30 years, but restored populations more closely resembled wild, local populations when cultivars were planted in closer proximity to nearby undisturbed sites. This study supports the cultivar vigor hypothesis and provides evidence for the long‐term persistence of cultivated traits in the environment.     

Copper uptake kinetics in hydroponically-grown durum wheat (Triticum turgidum durum L.) as compared with soil’s ability to supply copper

This paper focuses on the causes of zonation on agricultural land affected by secondary salinity between two halophytic grasses, puccinellia (Puccinellia ciliata Bor. cv. Menemen) and tall wheatgrass (Thinopyrum ponticum (Podp.) Z.-W. Liu & R.R.-C. Wang cv. Tyrrell). We hypothesized that the differences in zonation of puccinellia and tall wheatgrass were caused primarily by differences in the tolerance of these two species to waterlogging under saline conditions. This hypothesis was tested by conducting experiments in the field and in the glasshouse in irrigated sand cultures. At a saltland field site, locations dominated by puccinellia had EC_e values that were consistently higher (11–12 dS/m in early spring, and 5–9 dS/m in late summer) than locations dominated by tall wheatgrass. However locations dominated by puccinellia also had a watertable that was shallower (0.07–0.09 m in the high rainfall season; 0.11–0.13 m in the low rainfall season) than locations dominated by tall wheatgrass. In the glasshouse both species had similar growth responses to salinity under drained conditions, with a 50% decrease in shoot dry mass (DM) at ～300 mM NaCl. However, the combination of salinity (250 mM NaCl) and waterlogging increased puccinellia shoot DM by 150% but decreased shoot DM of tall wheatgrass by 90% (compared with salinity alone). Under saline/waterlogged conditions, puccinellia showed better exclusion of Na⁺ and maintenance of K⁺/Na⁺ in the shoots than tall wheatgrass. We conclude that the zonation of puccinellia and tall wheatgrass is associated with differences in their ion regulation which leads to substantial differences in their growth under saline/waterlogged conditions.     

Diversity and salt tolerance of native Acacia rhizobia isolated from saline and non‐saline soils

Re‐establishing native vegetation in stressed soils is of considerable importance in many parts of the world, leading to significant interest in using plant–soil symbiont interactions to increase the cost‐effectiveness of large‐scale restoration. However, effective use of soil microbes in revegetation requires knowledge of how microbe communities vary along environmental stress gradients, as well as how such variation relates to symbiont effectiveness. In Australia, shrubby legumes dominate many ecosystems where dryland salinity is a major issue, and improving plant establishment in saline soils is a priority of regional management agencies. In this study, strains of rhizobial bacteria were isolated from a range of Acacia spp. growing in saline and non‐saline soils. Replicates of each strain were grown under several salinity levels in liquid culture and characterized for growth and salt tolerance. Genetic characterization of rhizobia showed considerable variation among strains, with salt tolerance and growth generally higher in rhizobial populations derived from more saline soils. These strains showed markedly different genetic profiles and generic affiliations to those from more temperate soils, suggesting community differentiation in relation to salt stress. The identification of novel genomic species from saline soils suggests that the diversity of rhizobia associated with Australian Acacia spp. is significantly greater than previously described. Overall, the ability of some symbiotically effective strains to tolerate high salinity is promising with regard to improving host plant re‐establishment in these soils.     

Photosynthetic pathway and ontogeny affect water relations and the impact of CO2 on Bouteloua gracilis (C4) and Pascopyrum smithii (C3)

The eastern Colorado shortgrass steppe is dominated by the C₄ grass, Bouteloua gracilis, but contains a mixture of C₃ grasses as well, including Pascopyrum smithii. Although the ecology of this region has been extensively studied, there is little information on how increasing atmospheric CO₂ will affect it. This growth chamber study investigated gas exchange, water relations, growth, and biomass and carbohydrate partitioning in B. gracilis and P. smithii grown under present ambient and elevated CO₂ concentrations of 350 μl l⁻¹and 700 μl l⁻¹, respectively, and two deficit irrigation regimes. The experiment was conducted in soil-packed columns planted to either species over a 2-month period under summer-like conditions and with no fertilizer additions. Our objective was to better understand how these species and the functional groups they represent will respond in future CO₂-enriched environments. Leaf CO₂ assimilation (A _n), transpiration use efficiency (TUE, or A _n/transpiration), plant growth, and whole-plant water use efficiency (WUE, or plant biomass production/water evapotranspired) of both species were greater at elevated CO₂, although responses were more pronounced for P. smithii. Elevated CO₂ enhanced photosynthesis, TUE, and growth in both species through higher soil water content (SWC) and leaf water potentials (Ψ) and stimulation of photosynthesis. Consumptive water use was greater and TUE less for P. smithii than B. gracilis during early growth when soil water was more available. Declining SWC with time was associated with a steadily increased sequestering of total non-structural carbohydrates (TNCs), storage carbohydrates (primarily fructans for P. smithii) and biomass in belowground organs of P. smithii, but not B. gracilis. The root:shoot ratio of P. smithii also increased at elevated CO₂, while the root:shoot ratio of B. gracilis was unresponsive to CO₂. These partitioning responses may be the consequence of different ontogenetic strategies of a cool-season and warm-season grass entering a warm, dry summer period; the cool-season P. smithii responds by sequestering TNCs belowground in preparation for summer dormancy, while resource partitioning of the warm-season B. gracilis remains unaltered. One consequence of greater partitioning of resources into P. smithii belowground organs in the present study was maintenance of higher Ψ and A _n rates. This, along with differences in photosynthetic pathway, may have accounted for the greater responsiveness of P. smithii to CO₂ enrichment compared to B. gracilis. Received: 21 July 1997 / Accepted: 16 December 1997     

The Influence Of Salinity On Verticillium dahliae In Stem Cuttings Of Five Olive Cultivars

Verticillium dahliae represents one of the main limiting factors in olive production in the Mediterranean countries. Increasing shortage of fresh water and land, increase the pressure on using alternative sources of marginal or saline water, and land previously cropped with V. dahliae host plants. The objective of the present study was to evaluate the influence of salinity on V. dahliae expression in olive stem cuttings. V. dahliae‐inoculated cuttings of cvs. Picual, Frantoio, Mansanillo and Barnea, showed higher senescence symptoms than their non‐inoculated controls. Colonization levels obtained in cv. Picual were significantly higher than in cv. Frantoio. Manzanillo was the most sensitive cultivar to salinity alone, with significant senescence symptoms in 4 and 6 dS/m NaCl treatments. When cv. Manzanillo was exposed to both salinity and V. dahliae, significantly higher senescence symptoms were obtained as compared with each of them separately. Senescence symptoms of cv. Picual exposed to V. dahliae, whether or not in combination with saline solutions, were significantly higher than those when cuttings were exposed to a saline solution alone. In cv. Frantoio, which is more resistant to salinity than the other cultivars, significantly high senescence symptoms were observed only in combination of V. dahliae and high saline concentration (8 dS/m). The fungal colonization index in cv. Manzanillo in high salinity (8 dS/m) was significantly higher than in the treatment without salt. In cv. Barnea, colonization index in 8 dS/m salinity was significantly higher than in the 4 dS/m concentration or control (fresh water). In conclusion, our findings demonstrate the interaction between V. dahliae and saline irrigation in various cultivars. Thus, stem cuttings could serve as an effective screening method in breeding olive clones for V. dahliae resistance, salt tolerance and their interaction.     

Does Seed Priming Induce Changes in the Levels of Some Endogenous Plant Hormones in Hexaploid Wheat Plants Under Salt Stress？

In order to assess whether salt tolerance could be Improved In spring wheat （Triticum aestivum L.）, the present study was performed by soaking the seeds of two cultlvars, namely MH-97 （salt sensitive） and Inqlab-91 （salt tolerant）, for 12 h In distilled water or 100 mol/m^3 CaCl2, KCI, or NaCI. Primed seeds from each treatment group and non-primed seeds were sown In a field In which NaCI salinity of 15 dS/m was developed. Priming of seeds with CaCl2, followed by priming with KCI and NaCI, was found to be effective In alleviating the adverse effects of salt stress on both wheat cultivars In terms of shoot fresh and dry weights and grain yield. Priming with CaCl2 alleviated the adverse effects of salt stress on hormonal balance In plants of both cultlvars. In MH-97 plants, CaCl2 pretreatment considerably reduced leaf absclslc acid （ABA） concentrations and Increased leaf free salicylic acid （SA） concentrations under both saline and non-saline conditions. In contrast, In the Inqlab-91 plant, CaCl2 Increased free Indoleacetic acid （IAA） and indolebutyrlc acid （IBA） content. However, priming of seeds with CaCl2 did not alter free polyamlne levels in either cultlvar, although spermldlne levels were considerably lower In plants raised from seeds treated with CaCl2 for both cultlvars under saline conditions. Priming with KCI Increased growth In Inqlab-91 plants, but not In MH-97 plants, under saline conditions. The salinity Induced reducUon In auxins （IAA and IBA） was alleviated by NaCI priming In both cultlvars under saline conditions. However, NaCI Increased leaf free ABA content and lowered leaf SA and putresclne levels In Inqlab-91 plants under saline conditions. In conclusion, although all three priming agents （I.e. CaCl2, KCI, and NaCI） were effective In alleviating the adverse effects of salt stress on wheat plants, their effects on altering the levels of different plant hormones were different In the two cuItlvars.     

Naturally Saline Boreal Communities as Models for Reclamation of Saline Oil Sand Tailings

Reclaimed landscapes after oil sands mining have saline soils; yet, they are required to have similar biodiversity and productivity as the predisturbance nonsaline landscape. Given that many species in the boreal forest are not tolerant of salinity, we studied the effects of soil salinity on plant communities in natural saline landscapes to understand potential plant responses during the reclamation process. Vegetation–soil relationships were measured along transects from flooded wetlands to upland forest vegetation in strongly saline, slightly saline, nonsaline, and reclaimed boreal landscapes. In strongly saline landscapes, surface soil salinity was high (>10 dS/m) in flooded, wet‐meadow, and dry‐meadow vegetation zones as compared to slightly saline (<5 dS/m) and nonsaline (<2 dS/m) landscapes. Plant communities in these vegetation zones were quite different from nonsaline boreal landscapes and were dominated by halophytes common to saline habitats of the Great Plains. In the shrub and forest vegetation zones, surface soil salinity was similar between saline and nonsaline landscapes, resulting in similar plant communities. In strongly saline landscapes, soils remained saline at depth through the shrub and forest vegetation zones (>10 dS/m), suggesting that forest vegetation can establish over saline soils as long as the salts are below the rooting zone. The reclaimed landscape was intermediate between slightly saline and nonsaline landscapes in terms of soil salinity but more similar to nonsaline habitats with respect to species composition. Results from this study suggest it may be unrealistic to expect that plant communities similar to those found on the predisturbance landscape can be established on all reclaimed landscapes after oil sands mining.     

Drought tolerance in two perennial bunchgrasses used for restoration in the Intermountain West,USA

An ideal restoration species for the semi-arid Intermountain West, USA would be one that grows rapidly when resources are abundant in the spring, yet tolerates summer’s drought. We compared two perennial C_3, Triticeae Intermountain-native bunchgrasses, the widely occurring Pseudoroegneria spicata and the much less widespread Elymus wawawaiensis, commonly used as a restoration surrogate for P. spicata. Specifically, we evaluated seedlings of multiple populations of each species for biomass production, water use, and morphological and physiological traits that might relate to drought tolerance under three watering frequencies (WFs) in a greenhouse. Shoot biomass of E. wawawaiensis exceeded that of P. spicata regardless of WF. At low WF, E. wawawaiensis displayed 38% greater shoot biomass, 80% greater specific leaf area (SLA), and 32% greater precipitation use efficiency (PUE). One E. wawawaiensis population, E-46, displayed particularly high root biomass and water consumption at high WF. We suggest that such a plant material could be especially effective for restoration of Intermountain rangelands by preempting early-season weeds for spring moisture and also achieving high PUE. Our data explain how E. wawawaiensis has been so successful as a restoration surrogate for P. spicata and highlight the importance of measuring functional traits such as PUE and SLA when characterizing restoration plant materials.     

Salt‐tolerance diversity in diploid and polyploid cotton (Gossypium) species

The development of salt‐tolerant genotypes is pivotal for the effective utilization of salinized land and to increase global crop productivity. Several cotton species comprise the most important source of textile fibers globally, and these are increasingly grown on marginal or increasingly saline agroecosystems. The allopolyploid cotton species also provide a model system for polyploid research, of relevance here because polyploidy was suggested to be associated with increased adaptation to stress. To evaluate the genetic variation of salt tolerance among cotton species, 17 diverse accessions of allopolyploid (AD‐genome) and diploid (A‐ and D‐genome) Gossypium were evaluated for a total of 29 morphological and physiological traits associated with salt tolerance. For most morphological and physiological traits, cotton accessions showed highly variable responses to 2 weeks of exposure to moderate (50 mm NaCl) and high (100 mm NaCl) hydroponic salinity treatments. Our results showed that the most salt‐tolerant species were the allopolyploid Gossypium mustelinum from north‐east Brazil, the D‐genome diploid Gossypium klotzschianum from the Galapagos Islands, followed by the A‐genome diploids of Africa and Asia. Generally, A‐genome accessions outperformed D‐genome cottons under salinity conditions. Allopolyploid accessions from either diploid genomic group did not show significant differences in salt tolerance, but they were more similar to one of the two progenitor lineages. Our findings demonstrate that allopolyploidy in itself need not be associated with increased salinity stress tolerance and provide information for using the secondary Gossypium gene pool to breed for improved salt tolerance.