Leymus Mollis Research Articles

Identification of osmotic stress-responsive genes from <i>Leymus mollis</i>, a wild relative of wheat (<i>Triticum aestivum</i> L.)

The tolerance of the dune grass Leymus mollis (Triticeae; Poaceae) to various biotic and abiotic stresses makes it a very useful genetic resource for wheat breeding. Wide hybridization between L. mollis and wheat allows the introduction of Leymus chromosomes into the wheat genetic background and facilitates the integration of useful traits into wheat. However, the genetic basis controlling the physiological tolerance of L. mollis to multiple environmental stresses remains largely unexplored. Using suppression subtractive hybridization, we identified 112 osmotic-stress-responsive genes from L. mollis and confirmed their differential expression under osmotic stress. These genes were categorized into 13 functional categories, including cell defense and stress response, transcriptional regulation, signal transduction, biosynthesis of compatible solutes and cell wall metabolism. Representative genes were validated by northern blot and RT-PCR analyses of expression patterns in response to osmotic stress and abscisic acid treatment. The genes identified here represent a useful source of expressed sequence tags (ESTs) for the analysis and identification of Leymus chromosomes introduced into wheat. Furthermore, being highly conserved, genetically associated with osmotic stress tolerance and transferable to wheat, these ESTs provide significant tools for the development of EST-derived molecular markers for introgression of osmotic stress tolerance genes into wheat.

ハマニンニク (Leymus mollis)からの塩、乾燥ストレスに応答する遺伝子の同定と発現解析

ハマニンニク (Leymus mollis)からの塩、乾燥ストレスに応答する遺伝子の同定と発現解析

On the distribution of seed-eating Dicraeus nartshukae (Diptera, Chloropidae) and its host plant Leymus mollis

The distribution ranges of Dicraeus nartshukae Kanmiya (Diptera, Chloropidae) and its host plant Leymus mollis (Trin.) Pilger are discussed. Larvae of D. nartshukae develop in unripe seeds of Leymus mollis but not in the seeds of the closely related L. villosissimus and L. interior. The spikes, spikelets, and glumes of L. mollis are larger than in other species, and usually softly hirsute. The glumes of L. villosissimus and L. interior possess dense hirsute pubescence which appears to be unfavorable for oviposition of Dicraeus nartshukae. The absence of seedeating Dicraeus on L. villosissimus and L. interior is an additional argument in support of distinctness of these species. The distribution range of Dicraeus nartshukae is meridional, or Pacific littoral.

Post-eruption Legacy Effects and Their Implications for Long-Term Recovery of the Vegetation on Kasatochi Island, Alaska

We studied the vegetation of Kasatochi Island, central Aleutian Islands, to provide a general field assessment regarding the survival of plants, lichens, and fungi following a destructive volcanic eruption that occurred in 2008. Plant community data were analyzed using multivariate methods to explore the relationship between pre- and post-eruption plant cover; 5 major vegetation types were identified: Honckenya peploides beach, Festuca rubra cliff shelf, Lupinus nootkatensis–Festuca rubra meadow, Leymus mollis bluff ridge (and beach), and Aleuria aurantia lower slope barrens. Our study provided a very unusual glimpse into the early stages of plant primary succession on a remote island where most of the vegetation was destroyed. Plants that apparently survived the eruption dominated early plant communities. Not surprisingly, the most diverse post-eruption community most closely resembled a widespread pre-eruption type. Microhabitats where early plant communities were found were distinct and apparently crucial in determining plant survival. Comparison with volcanic events in related boreal regions indicated some post-eruption pattern similarities.

New Records of Vascular Plants in the Yukon Territory VIII

Forty-seven taxa, 35 native and 12 introduced, are reported as new to the flora of Yukon and nine taxa previously reported are deleted. The new native taxa are: Artemisia arctica ssp. comata, Botrychium alaskense, Botrychium minganense, Bromus richardsonii, Calamagrostis holmii, Carex incurviformis, Carex mackenziei, Carex microchaeta ssp. nesophila, Carex ramenskii, Carex rariflora var. androgyna, Carex tahoensis, Carex xerantica, Carex × flavicans, Deschampsia sukatschewii, Eleocharis erythropoda, Eleocharis macrostachya, Eleocharis mamillata, Erigeron ochroleucus, Impatiens noli-tangere, Limnorchis huronensis, Nymphaea tetragona, Polygonum douglasii ssp. douglasii, Potamogeton natans, Potentilla crebridens ssp. hemicryophila, Puccinellia tenella ssp. langeana, Rumex beringensis, Salix farriae, Salix glauca ssp. Stipuli fera, Saussurea nuda, Saxifraga hyperborea, Saxifraga rivularis ssp. arctolitoralis, Silene soczavana var. macrosperma, Symphyotrichum subspicatum, Taraxacum hyparcticum, and Zannichellia palustris. The new introduced taxa are: Acer negundo, Avena fatua, Camelina microcarpa, Crepis capillaris, Hippophae rhamnoides, Lamium amplexicaule, Linaria dalmatica, Medicago lupulina, Prunus padus, Rumex pseudonatronatus, Valeriana officinale, and Viola tricolor. Deleted taxa are: Aster laevis var. geyeri, Carex athrostachya, Elatine triantha, Camelina sativa, Erysimum cheiri, Galium palustre, Impatiens capensis, Platanthera hyperborea, and Sonchus oleraceus. Vouchers are cited and general notes on distribution and identification are provided. Four of the native taxa reported here are new to Canada: Botrychium alaskense, Carex microchaeta ssp. nesophila, Potentilla crebridens ssp. hemicryophila and Rumex beringensis.

Vegetation of eastern Unalaska Island, Aleutian Islands, AlaskaThis paper is one of a selection of papers published as part of the special Schofield Gedenkschrift.

Plant communities of Unalaska Island in the eastern Aleutian Islands of western Alaska, and their relationship to environmental variables, were studied using a combined Braun-Blanquet and multivariate approach. Seventy relevés represented the range of structural and compositional variation in the matrix of vegetation and landform zonation. Eleven major community types were distinguished within six physiognomic–ecological groups: I. Dry coastal meadows: Honckenya peploides beach meadow, Leymus mollis dune meadow. II. Mesic meadows: Athyrium filix-femina – Aconitum maximum meadow, Athyrium filix-femina – Calamagrostis nutkaensis meadow, Erigeron peregrinus – Thelypteris quelpaertensis meadow. III. Wet snowbed meadow: Carex nigricans snowbed meadow. IV. Heath: Linnaea borealis – Empetrum nigrum heath, Phyllodoce aleutica heath, Vaccinium uliginosum – Thamnolia vermicularis fellfield. V. Mire: Carex pluriflora – Plantago macrocarpa mire. VI. Deciduous shrub thicket: Salix barclayi – Athyrium filix-femina thicket. These were interpreted as a complex gradient primarily influenced by soil moisture, elevation, and pH. Phytogeographical and syntaxonomical analysis of the plant communities indicated that the dry coastal meadows, most of the heaths, and the mire vegetation belonged, respectively, to the widespread classes Honckenyo–Elymetea, Loiseleurio–Vaccinietea, and Scheuchzerio–Caricetea, characterized by their circumpolar and widespread species. Amphi-Beringian species were likely diagnostic of amphi-Beringian syntaxa, many of these yet to be described.

Tolerance to Sand Burial, Trampling, and Drought of Two Subarctic Coastal Plant Species (<i>Leymus mollis</i> and <i>Trisetum spicatum</i>)

In order to ensure the sustainable development of the North, increased anthropogenic pressure on subarctic environments must be accompanied by appropriate restoration techniques. Locally adapted restoration guidelines need to rely on sound ecological knowledge of the species used in restoration trials. We evaluate the tolerance (emergence and biomass production) of two coastal species (Leymus mollis and Trisetum spicatum) to sand burial, trampling, and drought, all major constraints to plant colonization in the village of Whapmagoostui-Kuujjuarapik in subarctic Quebec. In three 11-week greenhouse experiments, plants were submitted to three intensities of sand burial (0.0, 0.5, and 1.0 cm per week), trampling events (none, once per week, once per day) and drought (50 mL of water every other day, every week, and every other week). While T. spicatum performance decreased under both moderate and high sand burial intensities, L. mollis tolerated moderate burial intensity. Both species were able to sustain trampling, although the performance of T. spicatum was reduced under high trampling intensity. Finally, neither species could tolerate moderate and high drought intensities, suggesting that watering needs to be included in any restoration initiatives. Since L. mollis performed better than T. spicatum in the sand burial experiment, we recommend the use of this species in future small-scale restoration trials.

Assisted Revegetation in a Subarctic Environment: Effects of Fertilization on the Performance of Three Indigenous Plant Species

Assisted revegetation is particularly difficult in subarctic and arctic ecosystems where the impact of anthropogenic activities can be extensive and natural plant regeneration is slow. The construction of a military base in the 1950s at Kuujjuarapik–Whapmagoostui in northern Quebec destroyed most of the vegetation cover. Afterwards, other anthropogenic disturbances linked to the village expansion (housing, ATV traffic, pedestrian trampling) have slowed down the recovery process. To provide residents with low-cost but efficient assisted revegetation techniques, we evaluated the performance (seedling emergence, survival, and biomass production) of three indigenous plant species (Leymus mollis, Lathyrus japonicus, Trisetum spicatum) submitted to different levels of mineral and organic fertilizer additions in both a greenhouse experiment and a field plantation in the village. In the greenhouse experiment, moderate mineral fertilization had positive impacts on seedling emergence and both aboveground and belowground biomass of L. mollis. The magnitude of this impact on biomass was greater when mineral fertilization was combined with organic fertilization. The effects of mineral fertilization were negative on the other two species, especially at higher fertilization levels. However, after two growing seasons, a moderate level of mineral fertilizer in the field plantation had positive effects on the cover and aboveground biomass of all three species. Overall, organic fertilization from the substrate of a nearby marsh did not enhance plant performance in either experiment. Planting seeds of L. mollis or T. spicatum in combination with a moderate level of mineral fertilization at the time of planting provides a low-cost assisted revegetation treatment for subarctic villages.

Abnormal pollen development of bread wheat-Leymus mollis partial amphiploid

Octoploid Tritileymus was the partial amphiploid obtained from Triticum aestivum × Leymus mollis, its chromosome constitution was 14 Leymus chromosomes and 42 wheat chromosomes. In the pollen development of Tritileymus, some abnormalities were observed, such as the absence of tetrad formation, cytomixis of microspores, irregular shape of some microspores and multi-germination pores, symmetrical first mitosis, chromosomes or chromatids randomly dispersed in the cytoplasm of microspore.

New Records of Vascular Plants in the Yukon Territory VII

Based on field reconnaissance mainly in 2003 in Kluane National Park but also many other areas throughout the Yukon, information is provided on geographically significant plant occurrences. Thirteen native taxa, Agrostis humilis, Blysmopsis rufa, Carex bebbii, C. lenticularis var. dolia, C. nigricans, C. sartwellii, C. siccata, Diphasiastrum sitchense, Najas flexilis, Oxytropis arctica var. arctica, Oxytropis arctica var. murrayi, Saxifraga nelsoniana ssp. carlottae and Swertia perennis and two introduced taxa, Bromus japonicus and Leymus mollis ssp. mollis s.l. are reported new to the flora of the Yukon Territory. Significant range extensions for 109 native and eight introduced taxa are included and three species, Clematis occidentalis, Polygonum persicaria, and Verbena hastata are deleted from the flora.

Sources of wheat powdery mildew resistance from wheat-rye and wheat-Leymus hybrids.

Introgression of germplasm from rye and Leymus mollis has been used in the objective of broadening mildew resistance in wheat. The mildew resistant wheat lines were isolated from crosses of three hexaploid triticale lines, a mildew resistant double wheat-rye substitution line and a mildew resistant hexaploid wheat-L. mollis hybrid with three mildew susceptible breadwheats. Three different mildew isolates with a broad virulence have been used and lines with different resistance patterns, including resistance to all three mildew isolates, were selected. From a total of about 13,000 lines, eight lines from the triticale crosses, 58 from the double wheat-rye substitution line crosses and six from the L. mollis-hybrid crosses showed homozygous resistance to all three isolates. A differential tester set of wheat lines with known mildew resistance genes including earlier known resistance genes from rye showed a similarity between IRS-cultivars and the largest category in the triticale populations, indicating a higher frequency of IR chromosomes. The results are discussed in relation to the differential tester set and in relation to broadening the genetic base of resistance in wheat by interspecific hybridization.

Isolation, characterization, and analysis of Leymus-specific DNA sequences.

Genomic Southern hybridization using labeled total genomic DNA of Leymus mollis as probe showed intense hybridization signals on all restriction enzyme digested DNA from five species of Leymus Hochst., and four species of Psathyrostachys Nevski. Experiments using the same L. mollis probe, but with unlabeled blocking DNA from Psathyrostachys, showed no hybridization at all. These two genera evidently had the same genomic content. Southern hybridization without blocking allowed identification of DNA fragments abundant in Leymus and Psathyrostachys. Fragments potentially specific to Leymus were cloned. Five repetitive DNA clones from L. mollis and L. arenarius were characterized: pLmIs1, pLmIs44, pLmIs51, pLmIs53, and pLaIs56. These clones hybridized to both Leymus and Psathyrostachys on Southern blots - no clone hybridized to only one of these genera. Both Southern blot and fluorescence in situ hybridization (FISH) experiments showed that all the clones contained dispersed repetitive sequences. They painted all and whole chromosomes uniformly except at centromeres, telomeres, and nucleolar organiser regions. Three of these clones, i.e., pLmIs1, pLmIs44, and pLmIs53, were essentially specific to Leymus and Psathyrostachys - little or no hybridization was detected in other genera such as Triticum, Hordeum, Thinopyrum, or Elymus. Sequence analysis further revealed that the clones were part of retroelements. In particular, the clone pLmIs44 produced hybridization profiles suitable for analysis of genetic relatedness among species. The present study shows that Leymus and Psathyrostachys share the same basic genome, Ns, and therefore provides strong evidence for combining these two genera.

Trade-off between growth ability and stress tolerance in Leymus mollis (Poaceae) along a subarctic coastal dune sequence in northern Quebec

Several environmental factors vary with distance from the shoreline on coastal dunes. For instance, salinity, salt spray, and sand movement decrease but nutrient and water availability increase from the foredune to the stabilized dunes. Plants colonizing the upper beach and the foredune are thus exposed to more severe abiotic stresses than those on the stabilized dunes. Although community composition changes progressively from the upper beach to the stabilized dunes, some species persist through the sequence. For example, on the coastal dunes of subarctic Quebec, Leymus mollis (Trin.) Hara (Poaceae), a perennial grass that colonizes the upper beach and the foredune, persists onto older stabilized dunes. Under controlled conditions, the response of L. mollis ramets from different habitats along the dune sequence to various saline conditions was examined. It was expected that ramets from the upper beach and the foredune, where substrate salinity is typically higher, salt spray more important, and saltwater intrusion more frequent, to better support salinity stress. Ramets from the upper beach and the foredune had a higher relative growth rate (RGR) but were, in fact, less tolerant to salt stress than those from the stabilized dune. Because sand accumulation is higher on the upper beach and the foredune, a higher RGR may be favored there to the detriment of a higher sensitivity to salt stress. The salt tolerance of stabilized dune ramets may be the expression of a more generalized stress-tolerance strategy as suggested by low RGR and high leaf nutrient concentration.Key words: embryo dune, foredune, leaf turnover, relative growth rate (RGR), salt stress, stabilized dune, tolerance, trade-off.

Factors responsible for Honckenya peploides (Caryophyllaceae) and Leymus mollis (Poaceae) spatial segregation on subarctic coastal dunes

Low water and nutrient availability and significant sand movement, salt spray, and soil salinity are typical of coastal dunes. These conditions are generally unfavorable for the various life stages of plants and especially for seedlings. However, the intensity of these stresses decreases landward, even over short distances, with significant effects on community composition. On coastal dunes in subarctic Québec, Canada, Honckenya peploides (Caryophyllaceae) colonizes the upper beach where it forms small mounds called embryo dunes. Leymus mollis (Poaceae) is mostly restricted to the foredune; however, a few individuals successfully establish on the upper beach, particularly on embryo dunes. We hypothesized that this differential distribution is associated with differences in the tolerance of the two species' seedlings to physical stresses. Honckenya peploides and L. mollis seedling tolerance to sand burial, salt spray, soil salinity, and nutrient and water availability was assessed in greenhouse experiments. Unexpectedly, our results showed that tolerance to sand burial, salt spray, and soil salinity was lower for H. peploides than for L. mollis. If seeds are available and seedlings tolerate the conditions prevailing on the upper beach well, why are mature L. mollis individuals rare in this habitat? We suggest that massive abrasion events (e.g., violent storm waves and ice thrust) restrict the presence of the species on the upper beach.

Facilitation of Leymus mollis by Honckenya peploides on coastal dunes in subarctic Quebec, Canada

Plant recruitment in the very first stages of primary succession is limited by seed availability and harsh abiotic conditions. Facilitation, the positive effect of an earlier successional species on a later successional one, is often significant during primary succession and may result from the trapping of seeds and (or) the improvement of seed germination, seedling emergence, establishment, growth, and survival. We examined the effect of mature Honckenya peploides (L.) Ehrh. (Caryophyllaceae) plants on Leymus mollis Trin. (Poaceae) seedling recruitment on a coastal dune in subarctic Quebec, Canada. Facilitative effects of H. peploides on L. mollis may be critical because the latter species is a key element in the dynamics of the coastal dunes at high latitudes in eastern Canada. Honckenya peploides forms small mounds on the upper beach (the embryo dunes) that are typically distinct from the foredune. Leymus mollis progression towards the upper beach occurs through clonal growth, but seedling recruitment is also significant and contributes to the population genetic diversity. We determined L. mollis seedling emergence and growth and estimated various abiotic variables in two habitats on the upper beach: the embryo dunes and the bare, flat areas beside embryo dunes. Sand accumulation and substrate salinity were higher on the embryo dunes than beside them. Leymus mollis seedling emergence was more important on embryo dunes, although seedling growth was lower there. Our results suggest that the embryo dunes formed by H. peploides facilitate L. mollis recruitment possibly by trapping seeds and improving seed germination and seedling emergence.Key words: coastal dunes, facilitation, Honckenya peploides, interspecific interactions, Leymus mollis, sand burial.

Bacterial Leaf Stripe Caused by Xanthomonas translucens pv. cerealis on Intermediate Wheatgrass in Idaho.

Intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth & D.R. Dewey) (synonyms: Agropyron intermedium [Host] Beauv.; Elytrigia intermedia [Host] Nevski) is widely grown as a forage crop and is also used to control soil erosion. In a seed production field of cv. Rush in Washington County, ID, more than 80% of the plants were found affected by a disease with leaf stripe symptoms. The lesions were initially elongated, water-soaked, and translucent, later developing into brown, necrotic, interveinal stripes that often coalesced. Frequently, yellowish, dried, granular, or flaky exudate was present on the lesion surfaces. Microscopic examination of cut pieces of symptomatic tissue showed profuse bacterial streaming. Isolations on nutrient agar and King's medium B agar consistently yielded smooth, circular, butyrous, yellow, raised bacterial colonies. The bacterium was rod-shaped, Gram-negative, oxidase-negative, aerobic, and did not reduce nitrate. Substrate utilization profiles (Biolog Inc.), and cellular fatty acid analysis (Analytical Services Inc.) identified the bacterium as a pathovar of Xanthomonas translucens (syn: X. campestris pv. translucens). For pathogenicity tests, 3- to 5-week-old greenhouse-grown seedlings were injected in the whorl with a water suspension of 24-h-old culture (approximately 107 cfu/ml) of the bacterium. Control plants were injected with sterile distilled water. The plants were incubated at 25 to 28°C and observations were recorded after 6 to 10 days. The bacterium was pathogenic (causing water-soaked lesions, often with bacterial exudate) to T. intermedium cvs. Rush, Tegmar, PI 547316, and PI 380636; wheat cvs. Stephens, Vandal, FF 301, and FFR 525; barley cvs. Galena, Lud, and Steptoe; oat cvs. Boone, Clinton, Erban, Marion, Mohawk, Nemaha, Olena, and Tama; rye cvs. Florida 401, Hazel, Musketeer, Oklon, Rymin, Wintermore, and Wrens 96; Agropyron cristatum cv. Ephraim; A. cristatum × desertorum cv. Hycrest; Bromus arvensis; B. briziformis; B. catharticus; B. inermisssp. inermis; B. inermis ssp. pumpellianus; B. japonicus; B. marginatus; B. popovii; B. rigidus; B. tomentellus; Dactylis glomerata cvs. Paiute and Potomac; Elymus repens; Leymus mollis; L. angustus cv. Prairieland; Lolium arundinaceum cv. Fawn; L. perenne cv. Zero Nui; and Psathyrostachys juncea cv. Bozoisky. It was only weakly pathogenic (with small, chlorotic or water-soaked lesions and no exudation) to Phleum pratense cv. Climax and Pseudoroegneria spicata ssp. spicata cv. Goldar. It was not pathogenic to Andropogon gerardii cv. Pawnee; Festuca ovina; Oryza sativa cvs. Cypress, Newbonnet, and M201; or Schizachyrium scoparium cv. Camper. Based on the pathogen's natural host and its wide host range among cereals and grasses as verified by inoculation, the bacterium was identified as X. translucens pv. cerealis. This is the first report of natural occurrence of this pathogen on T. intermedium. A sample (105 g) of seed used for planting the affected field was found contaminated with 7.5 × 104 cfu/g of the pathogen, and seed to seedling transmission was observed in greenhouse tests. Contaminated seed, thus, may serve as a source of primary inoculum to intermediate wheatgrass, which in turn may serve as an inoculum source to other susceptible cereals and grasses growing in the vicinity.

Development of a genomic in situ hybridization method using Technovit 7100 sections of early wheat embryo

It is difficult to observe the behavior of chromosomes in early wheat embryos because they are wrapped in several cell layers of the ovary. Here we conducted genomic in situ hybridization on sections of ovary embedded in Technovit 7100, a resinous compound suitable for in situ hybridization of mRNA in sectioned tissues. With this resin it is possible to make thin sections with high resolution, no autofluorescence, and good water permeability. These features enable histochemical study using fluorescence microscopy. We established the most suitable conditions for the denaturation of target DNA embedded in Technovit resin, and performed GISH on them. Using this method, we identified Leymus mollis chromosomes in the young ovary of F1 hybrids between wheat and L. mollis. Furthermore, we observed the behavior of maize chromosomes in early wheat × maize hybrid embryos.

The effect of sea-water submergence on rhizome bud viability of the introducedAmmophila arenaria and the nativeLeymus mollis in California

Ammophila arenaria, an invasive European beach grass, dominates most United States Pacific coast beaches north of San Francisco Bay, and it appears to severely reduce opportunities for regeneration of native plant species, including American beach grass,Leymus mollis. The knowledge of how longAmmophila rhizomes can survive in sea-water is important for long-tern management strategies, which must consider the probability of reinvasion of areas whereAmmophila has been eradicated. The bud viability of bothAmmophila arenaria andLeymus mollis remained high following submergence in sea-water for 7 days, andLeymus bud viability was still high after 13 days submergence. In fact,Leymus bud viability appears to be enhanced slightly by submergence for 7 days in sea-water. SinceAmmophila rhizomes retain a mean bud viability of >50% following submergence for 7 days, there is clearly the potential for long distance dispersal to other beaches. Even after 13 days of submergence,Ammophila rhizomes still had a mean bud viability of 8.5%. Assuming near-shore current speeds of 5–45 cm/sec, viableAmmophila rhizomes can be transported up to 505 km in 13 days.

Ecophysiological differences among Leymus mollis populations across a subarctic dune system caused by environmental, not genetic, factors.

Plant species that persist during succession, from the colonization to the stabilization stages, face major environmental changes. Such changes are believed to have significant effects on species performance. In subarctic coastal dune systems, Leymus mollis colonizes the embryo dunes, on the upper limit of the beach. It reaches its maximum density on the foredune, but also grows on older, stabilized ridges. This paper reports on the phenotypic variations of some ecophysiological traits associated with the persistence of L. mollis on a dune system on the east coast of Hudson Bay (northern Quebec). Leymus mollis ramets tend to have a lower net carbon assimilation rate and water use efficiency, and a higher substomatal CO2 concentration on the stabilized dune than on the foredune. However, these physiological differences cannot be explained by differences in leaf morphology or nitrogen content. Under controlled conditions, ecophysiological differences observed in the field disappear, suggesting that these are not genetic but determined by environmental changes along the foredune-stabilized dune gradient. We propose that higher net carbon assimilation rate on the foredune might be related to higher sink strength in relation to the growth-stimulating effect of sand burial.

Persistence of colonizing plant species along an inferred successional sequence on a subarctic coastal dune (Québec, Canada)

Coastal dune systems have been extensively studied in various parts of the world, but few investigations have been made in the Subarctic where temperatures remain relatively low during the short growing season. Here, we report the results of a study performed on a subarctic coastal dune system on the east coast of Hudson Bay, Canada. We determined the spatiotemporal dynamics of some important substrate characteristics, described the spatial dynamics of the vascular plant community, and followed temporal changes in the populations of the two major plant species, Leymus mollis (Poaceae) and Lathyrus japonicus (Fabaceae), along a toposequence, from the embryo dunes to the stabilized dune. The observed spatial changes in substrate characteristics were consistent with those reported in studies of lower-latitude dune systems, but they were generally of lesser magnitude. The subarctic climate appears to have unusual effects on the spatial gradient of substrate salinity and water content. For instance, salinity did not vary along the toposequence early in the season while the bay was still partly frozen, but it showed a significant gradient during the summer, with lower salinity values on the stabilized dune. Life-form turnover, from the upper beach to the stabilized dune, was lower than what has been reported for lower-latitude dune systems because of the rarity of annual plant species. Although the density and biomass of Leymus and Lathyrus ramets decreased along the toposequence, both species persisted onto the stabilized dune where they were the most frequent vascular plants. Such persistence appears to be related to the ability of both species to physiologically adjust to local conditions. Because of the climatic context, subarctic coastal dunes constitute unique systems, with characteristics quite different from those of lower-latitude coastal dune systems.