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Rhizosphere and root associated bacteria are key components of plant microbiomes and influence crop production. In sustainable agriculture, it is important to investigate bacteria diversity in various plant species and how edaphic factors influence the bacterial microbiome. In this study, we used high-throughput sequencing to assess bacterial communities associated with the rhizosphere and root interior of canola, wheat, field pea, and lentil grown at four locations in Saskatchewan, Canada. Rhizosphere bacteria communities exhibited distinct profiles among crops and sampling locations. However, each crop was associated with distinct root endophytic bacterial communities, suggesting that crop species may influence the selection of root bacterial microbiome. Proteobacteria, Actinobacteria, and Bacteroidetes were the dominant phyla in the root interior, whereas Gemmatimonadetes, Firmicutes, and Acidobacteria were prevalent in the rhizosphere soil. Pseudomonas and Stenotrophomonas were predominant in the rhizosphere and root interior, whereas Acinetobacter, Arthrobacter, Rhizobium, Streptomyces, Variovorax, and Xanthomonas were dominant in the root interior of all crops. The relative abundance of specific bacterial groups in the rhizosphere correlated with soil pH and silt and organic matter contents; however, there was no correlation between root endophytes and analyzed soil properties. These results suggest that the root microbiome may be modulated by plant factors rather than soil characteristics. [ABSTRACT FROM AUTHOR]

The potential expansion of mountain pine beetle ( Dendroctonus ponderosae Hopkins) from western North America into the Great Lakes Region (Michigan, Minnesota, Wisconsin, and Ontario) could negatively impact eastern pine forests. Currently, no metrics exist to assess susceptibility in the region. I have developed a hazard rating system for the Great Lakes Region that utilizes common attributes of forest structure and composition and have assessed the current susceptibility using the Forest Inventory and Analysis database. The vast majority of plots (∼90%) that contained at least one living pine species were classified as moderately or highly susceptible. Plots on federal (USDA Forest Service) lands had higher susceptibility ratings than those on private or state-owned lands. Ordination results highlighted differences among the susceptibility scores (high, moderate, and low) across plots. Plots with high susceptibility were associated with greater total plot density and pine density, and plots with low susceptibility were associated with lower total plot density and greater overstory species richness. There are still many unknowns regarding mountain pine beetle in the Great Lakes Region; however, as natural resource managers plan for the future, they may want to consider the potential arrival of mountain pine beetle in eastern pine forests when developing silvicultural prescriptions. [ABSTRACT FROM AUTHOR]

In this paper, we report an investigation of how forest stand mixture may affect biomass allometric relationships in Norway spruce ( Picea abies (L.) Karst.). Analysis of aboveground biomass data was conducted for 50 trees: 25 sample trees from a pure Norway spruce stand and 25 from a mixed stand of Norway spruce with European beech ( Fagus sylvatica L.). ANCOVA results demonstrated that individual-tree biomass allometry of the pure stand significantly differed from that of the mixed stand. Allometric characteristics depended on the biomass component recorded and the type of biomass predictor used. When predicted by diameter at breast height and (or) height, the total aboveground biomass of mixed-stand trees was significantly less than that for pure-stand trees. This 'apparent' lower aboveground biomass was attributed to the lower branch and needle biomass proportions of trees growing in mixed stand. The findings indicate that caution should be exercised when applying biomass allometric models developed from pure stands to predict tree biomass in mixed stands (and vice versa), as such data treatment may introduce significant bias. [ABSTRACT FROM AUTHOR]

In the context of global changes that modify the distribution range of species, there is an urgent need to identify climate variables affecting species dispersal. We investigated patterns of aerial propagule release (sexual and asexual) of boreal bryophytes in response to weather. We present the first community-level study that examines the impact of weather on the phenology of bryophytes, and we divided it into phases. Bryophyte propagule rain was trapped in 2013 (summer and fall) and 2014 (spring and fall), and climatic variables were collated from the years 2012 to 2014. The phases of the phenology and the weather variables one season to two years preceding propagule release, which may influence the dispersal of propagules, were identified. Propagule release varies with weather conditions at the time of dispersal (direct effects), but is also associated with weather during the winter and summer one year preceding dispersal (indirect effects), which presumably influences survival, growth, and fertilization of the mother plant as well as propagule and sporophyte development. We suggest that propagule release is related to weather conditions occurring from one to several previous seasons, particularly humidity, temperature, and length (duration) of winter. Dividing the phenology into phases, we present an innovative method that should provide new insights into bryophyte dispersal dynamics in response to climate. [ABSTRACT FROM AUTHOR]

Plant species are unique in their biological traits and biogeographical history, resulting in distinctive species distributions. Continuous and fragmented ranges of varying size and shape have captured the interest of biogeographers. Fragmented distribution into isolated populations is a common pattern of temperate and boreal species caused by contraction and expansion processes. Jack pine ( Pinus banksiana Lamb.), a North American tree species, is among a multitude of species showing range distributions fragmented to isolated populations. Whether disjunct jack pine forests are remnants of larger Holocene populations or newly established populations due to long-distance transport remains unanswered. We used a retrospective approach based on soil macrocharcoal analysis to address the question of residency of a disjunct population in the boreal forest. The studied forest forms a disjunct population of a former regional population that has contracted since the mid-Holocene. Short to moderately long fire intervals occurred over the last 6000 years to maintain the species in a fire-prone, sandy environment assuring its regeneration and survival. Disjunct distributions similar to the studied pine population are often caused by regional extirpation of populations in which environmental contraction produces small ecological refugia where local conditions remain suitable through time for a species to complete its life cycle. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Opuntia series Armatae is evaluated considering morphological (vegetative, floral, and carpological) and cytogenetical (diploid number, presence of heterochromatin, and physical localization of ribosomal genes) features to shed light on their systematics and evolution. Three complexes (named O. elata, O. megapotamica, and O. monacantha) are proposed to accommodate seven species according to the tepal, fruit, stigma, and seed aril traits. Additional systematic conclusions include the following: ( i) O. stenarthra, O. assumptionis, O. cognata, and O. subsphaerocarpa are synonyms; ( ii) O. elata is a variable species with two varieties (var. cardiosperma and var. obovata); ( iii) O. rioplatense is a synonym of O. elata var. obovata; and ( iv) O. megapotamica is a polymorphic species with two varieties (one newly described and a new combination). All species had small similar-sized symmetrical chromosomes and were tetraploid (2 n = 44), except for a population of O. arechavaletae and O. monacantha (2 n = 22). All showed one or two pairs with CMA+/DAPI− NOR associated bands. The 18-5.8-26S rDNA loci seem to coincide with CMA+/DAPI−/NOR blocks. The number of 5S signals detected was proportional to the ploidy level of the species. A combination of cytogenetic and morphological features helped to differentiate the complexes, species, and varieties of Opuntia ser. Armatae. [ABSTRACT FROM AUTHOR]

Copines are evolutionarily conserved calcium-dependent membrane-binding proteins with potentially critical biological functions. In plants, the function of these proteins has not been analyzed except for in Arabidopsis thaliana where they play critical roles in development and disease resistance. To facilitate functional studies of copine proteins in crop plants, genome-wide identification, curation, and phylogeny analysis of copines in 16 selected plant species were conducted. All the identified 32 plant copines have conserved features of the two C2 domains (C2A and C2B) and the von Willebrand factor A (vWA) domain. Different from animal and protozoa copines, plant copines have glycine at the second residue potentially acquiring a unique protein myristoylation modification. Phylogenetic analysis suggests that copine was present as one copy when evolving from green algae to basal flowering plants, and duplicated before the divergence of monocots and dicots. In addition, gene expression and protein localization study of rice copines suggests both conserved and different properties of copines in dicots and monocots. This study will contribute to uncovering the role of copine genes in different plant species. [ABSTRACT FROM AUTHOR]

The planning of wood procurement requires reliable information about the species-specific timber assortments on which the economic value of a production forest depends. The timber assortments refer to the stem volumes of the sawlog and pulpwood fractions, specified in terms of both timber quality and allowable log dimensions, e.g., the stem diameter at breast height (dbh). We propose here an airborne laser scanning based calibration framework for generating species-specific dbh distributions that combines the area-based approach (ABA) and individual-tree detection (ITD), two established and independent approaches for retrieving forest attributes from airborne laser scanning data. Both ABA- and ITD-derived dbh distributions were generated nonparametrically for pine, spruce, coniferous, deciduous, and all species and assessed with respect to the plot-level species-specific total stem volume (m3·ha-1) and approximations of volume of timber assortments. Although after calibration, the total volume of all species and the volume approximations of coniferous sawlog and spruce pulpwood decreased in accuracy by 4%-7%, the calibration improved the accuracy of the other 12 species-specific estimates by 2%-17%, testifying to the general effectiveness of the proposed calibration framework. [ABSTRACT FROM AUTHOR]

Understanding variation in tree stem form is fundamental to both ecological and economic assessments of forest ecosystem structure and function. Stem taper models (STMs) are widely used to describe tree form, but it can be challenging to apply them to trees with stems that diverge from an idealized norm, often leading to the exclusion of many trees from stem taper studies. Here, new 'whole-tree' form type classes are advanced as simple and useful groupings for capturing stem form variation of trees of diverse morphological types and tested with a large tree data set without exclusion criteria. New form type classes explained much more of main stem form variation than knowledge of tree species, while 'merchantable' form types explained the most variation between trees and stands. Broad-leaved species were much more likely to have complex stem forms than needle-leaved species, but species 'evergreenness' was a very weak predictor of stem form variation when tree- and stand-level form variation was accounted for. A new, generalized framework for stem taper modeling is demonstrated, using both species and merchantable form types to capture tree-level random effects. New form types and the STM approach are relatively easy to apply and should be relatively simple to integrate into any conventional forest inventory system. Overall, the study demonstrates the importance of including and accounting for the diversity of observed stem forms in developing STMs. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To analyze the implications of exotic radiata pine ( Pinus radiata D. Don) plantations for macrofungal diversity, a comparative mycocoenological survey was conducted over three consecutive years in pine plantations and native oak forests ( Quercus robur L.) in the Urdaibai Biosphere Reserve. Macrofungal diversity was analyzed at species and community levels, and multivariate techniques were used to obtain insight into the fungal community in all functional groups. A total of 513 species was recorded, with ectomycorrhizal fungi being the most abundant, followed by the lignicolous saprotrophs. Measurements at both the overall level and the plot level showed that oak forests were richer in macrofungal species than pine plantations. The two ecosystems shared 107 species, but they possessed distinct species assemblages in all functional groups, as confirmed by PERMANOVA analysis. Although more abundant in oak stands, host-specific fungi were recorded in both ecosystems, revealing that exotic pine plantations can easily access fungal inocula from natural pine forests in the vicinity. However, even though the macrofungal richness in plantations is comparable with that in other native conifer forests in Europe, the community was made up of generalists, i.e., species that were not habitat specialists. In contrast, rarely reported, uncommon fungi were recorded in oak plots, revealing the importance of residual, native forest patches for fungal conservation. [ABSTRACT FROM AUTHOR]

Tree species distributions and diversity could be explained by rank changes in performance over multiple spatiotemporal resource gradients, i.e., resource partitioning. For 14 species planted in 45 harvest gap and closed canopy locations in a mesic northern hardwood forest community, Michigan, USA, we asked the following questions: ( i) are species growth responses to light, nitrogen (N), or N form (ammonium vs. nitrate) related to their ecological distributions and phylogenies? and ( ii) is there evidence of growth-based resource partitioning over measured resource gradients? Growth responses to the N form were consistent with both differences in uptake energy requirements between N forms and their availability through succession and across fertility gradients; height growth was negatively related to the species shade-tolerance score, especially in high light, i.e., shade-intolerant species responded to soil nitrate-N and shade-tolerant species responded to ammonium-N; fertile soil associated species responded to nitrate-N and infertile soil associated species to ammonium-N; and gymnosperms responded to ammonium-N and angiosperm responses varied. Modeled growth responses to resources showed only modest evidence for rank changes over resource gradients, with N contributing less to rank changes than light. Thus, growth responses to resources were accurately predicted by species ecology and (or) phylogeny; however, there was only modest support for the notion that growth-based resource partitioning underlies community-scale diversity in a northern hardwood forest. [ABSTRACT FROM AUTHOR]

Density estimates for habitat objects are used for a variety of forestry and wildlife management applications, but supporting field work can be costly. We used point simulations and field studies of snags and shrub stems to evaluate and compare the plotless Batcheler-corrected point distance (BCPD) method of data collection with the plot-based belt transect (BT) method for estimating object density (snags and shrub stems). The program Transect Point Density () was used to calculate density and confidence limits. Relative to the BT method, we found the BCPD method performs well under a range of clustered and random dispersion patterns and point densities, with measurements made to the nearest neighbour of the initial point object allowing correction of bias caused by nonrandom spatial dispersion patterns. The BCPD parameter of spatial dispersion, A1, was correlated with I, the variance-to-mean ratio used to estimate spatial dispersion in plot-based samples. The BCPD method also allows measurement to the third object (next-nearest neighbour) to account for second-order clumping, but we found that this estimate was sensitive to measurement error or technique where dense mats of wetland shrub species Ledum groenlandicum Oeder or Myrica gale L. occurred. We also used BCPD to characterize shrub community structure and found no evident bias, relative to BT data, for estimating relative species composition, richness, and diversity. The BCPD method was cost-effective relative to the BT method, with cost ratios 4-47 times higher for the BT method, and for a given investment allowed sampling of a greater area and diversity of stand conditions. Consequently, the BCPD method will facilitate collection of better data for developing and testing habitat models as well as evaluating the effects and effectiveness of forest management options at both the stand and landscape scales. [ABSTRACT FROM AUTHOR]

Depletion of Ca from forest soils due to acidic deposition has had potentially pervasive effects on forest communities, but these impacts remain largely unknown. Because snails, salamanders, and plants play essential roles in the Ca cycle of northern hardwood forests, we hypothesized that their community diversity, abundance, and structure would vary with differences in biotic Ca availability. To test this hypothesis, we sampled 12 upland hardwood forests representing a soil Ca gradient in the Adirondack Mountains, New York (USA), where chronic deposition has resulted in acidified soils but where areas of well-buffered soils remain Ca rich due to parent materials. Along the gradient of increasing soil [Ca2+], we observed increasing trends in snail community richness and abundance, live biomass of redback salamanders ( Plethodon cinereus (Green, 1818)), and canopy tree basal area. Salamander communities were dominated by mountain dusky salamanders ( Desmognathus ochrophaeus Cope, 1859) at Ca-poor sites and changed continuously along the Ca gradient to become dominated by redback salamanders at the Ca-rich sites. Several known calciphilic species of snails and plants were found only at the highest-Ca sites. Our results indicated that Ca availability, which is shaped by geology and acidic deposition inputs, influences northern hardwood forest ecosystems at multiple trophic levels, although the underlying mechanisms require further study. [ABSTRACT FROM AUTHOR]

Riparian buffer strips are increasingly used to mitigate disturbance effects on terrestrial biota found adjacent to streams, yet it is unclear how the effects of canopy treatment (clear-cut, buffer, or intact forest) will interact with pre-existing stream-upland gradients. We questioned whether proximity to the stream would influence bryophyte richness and whether the effects of canopy treatment on bryophyte composition and functional group representation would differ along the stream-upland gradient. Bryophyte richness, abundance, and composition were sampled in continuous forest ( n = 6), two-sided buffers (buffer width approximately 15 m on both stream sides; n = 10), and clear-cuts ( n = 7) in the southern interior of British Columbia. At each site, bryophyte functional group frequency was sampled within 10 × 2 m belt transects located at 1, 5, and 10 m from the stream edge. Both distance from the stream and canopy treatment were strongly associated with bryophyte community variation. The richness of many functional groups was highest immediately adjacent to the stream. The richness and frequency of forest-associated species, as well as the overall extent of the bryophyte mat, had the highest values in continuous forests, intermediate values in buffers, and lowest values in clear-cuts. Although significant differences in bryophyte communities occurred between buffers and clear-cuts at all distances from the stream, differences between buffers and continuous forest were nonsignificant. These results indicate that riparian buffers can play an important role in the mitigation of harvesting effects on the bryologically rich communities along small headwater streams. [ABSTRACT FROM AUTHOR]

Mexico is a center of diversity of . As currently circumscribed, arborescent Gossypium species (subsection ) are widely distributed in dry deciduous forests located from Sinaloa in the north of its range to Oaxaca in the south of its range. However, extensive morphological variation exists among accessions from these different geographic regions. The objective of this work was to determine whether the observed morphological variation is reflected at the molecular level. Molecular diversity and phylogenetic relationships were estimated with 210 randomly amplified polymorphic DNA fragments and 766 amplified fragment length polymorphism fragments among 33 accessions of arborescent Gossypium, including 23 of , the most widely distributed of the arborescent Mexican diploid Gossypium species. Over 90% of the fragments were polymorphic; however, each accession contained only between 32% and 46% of the total loci. Two thirds of the loci among the G. aridum accessions had allelic frequencies lower than 80%. The genetic distance between (subsection ) and species of subsection Erioxylum ranged between 0.64 and 0.84. The genetic distance between two recognized species, and , within subsection Erioxylum was 0.32. Most molecular data support the traditional classification of Gossypium species and the geographical ecotypes of the G. aridum accessions. A newly collected accession, US-72, of subsection Erioxylum was genetically distant (range, 0.42-0.54) from the other species of the subsection. Molecular data support the recognition of this taxon as a new species. The molecular diversity among accessions of G. aridum was greater than that among the species of subsection Erioxylum. The results indicate this subsection deserves additional study to establish a defensible taxonomic treatment of the various taxa and to resolve genetically distant geographical ecotypes. [ABSTRACT FROM AUTHOR]

Forest herbs account for greater species richness than any other plant type in deciduous forests and are the most vulnerable to anthropogenic disturbances. We examined whether the limited distribution of rare Appalachian forest herbs in Nova Scotia is related to edaphic specialization or a history of anthropogenic disturbance. Remnant populations are restricted to floodplain forest, where both habitat factors and disturbance history differ significantly from those of adjacent upland sugar maple forest. Contrasting soil and litter layers between floodplain stands and adjacent upland sites revealed the latter to be deficient in key cations (calcium, magnesium, boron); however, regression models for uplands and for floodplains showed that native herb richness was related to soil fertility in each case. Soil calcium accounted for most of the species richness variation among floodplains for native herbs and for a large seeded guild that contains most of the rare species on floodplains. Given the widespread anthropogenic decalcification of forest soils throughout eastern North America, conservation efforts must ( i) increase and connect deciduous forest floodplain ecosystems and ( ii) understand how to manage and create suitable cation-rich migration corridors in the forest landscape. [ABSTRACT FROM AUTHOR]

In an environment of uncertain climatic change, there is an urgent need to develop robust reserve networks, i.e., networks that conserve species across multiple climatic futures. Using climatic envelopes based on multiple future climatic scenarios, we first estimate the impacts that these scenarios might have on the distributions of 63 native tree species in the Province of Ontario. Next, an optimization model is applied to expand an existing system of reserves in this province by determining the minimum number of optimal locations for additional reserves both with and without the need for migration. The optimization model formulated differs from previous work in that it meets the need for present and future distributions to occur in the same reserve and accommodates multiple differing climate change scenarios rather than a single scenario. The reserve selection approach described here can be applied anywhere that species' distributions and environmental grids are available. Although this approach is designed to produce a robust solution to the uncertainties over future climatic scenarios, it does not eliminate these uncertainties because the proposed solutions inherit the uncertainties of the global climate change models. Dans un contexte d'incertitude face au changement climatique, il est urgent de mettre sur pied des réseaux robustes de réserves, c.-à-d. des réseaux qui préservent les espèces face à un éventail d'avenirs climatiques plausibles. À l'aide d'enveloppes climatiques basées sur un ensemble de scénarios climatiques futurs, nous estimons d'abord l'impact que ces scénarios pourraient avoir sur la répartition géographique de 63 espèces indigènes arborescentes dans la province d'Ontario. Ensuite, un modèle d'optimisation est appliqué pour étendre le système existant de réserves dans cette province en déterminant le nombre minimum de localisations optimales pour des réserves additionnelles avec et sans besoin de migration. Le modèle d'optimisation qui a été développé diffère des modèles précédents en ce qu'il répond à la nécessité que les répartitions actuelle et future se retrouvent dans la même réserve et qu'il tient compte de plusieurs scénarios de changement climatique différents plutôt que d'un seul. L'approche présentée ici pour choisir des réserves peut être appliquée partout où la répartition des espèces et des grilles environnementales sont disponibles. Bien que cette approche soit conçue pour produire une solution robuste aux incertitudes inhérentes aux scénarios climatiques futurs, elle n'élimine pas ces incertitudes parce que les solutions proposées héritent des incertitudes des modèles de changement climatique planétaire. [ABSTRACT FROM AUTHOR]

Traits have been widely used in plant ecology to understand the rules governing community assembly, and to characterize primary strategies that define community structure and ecosystem properties. Relatively little is known as to whether the traits that are ecologically important at macroecological scales are either variable, or of consequence at fine scales within species. We measured trait variation within populations of the grassland plants Festuca ovina L. and Koeleria macrantha (Ledeb.) Schult., to test the hypothesis that fine-scale intraspecific trait variation drives local community structure. Both species showed large genotypic variation for all traits. Size-related traits of genotypes of K. macrantha observed under monoculture predicted their performance in model grassland communities that possessed both genetic and species diversity. The same correspondence was much weaker for the experimental population of F. ovina. A trade-off in allocation between shoot mass and relative allocation to reproduction was evident in the experimental population of F. ovina. Furthermore, both species showed evidence of a positive relationship between specific leaf area (SLA) and allocation to culm mass. This trait covariation indicates the existence of intraspecific trade-offs in life-history and growth strategies similar to those used to define primary plant strategies, which potentially buffers both species abundance and species coexistence against environmental challenges. En écologie végétale, on a largement utilisé les caractères génétiques pour comprendre les règles régissant l'assemblage des communautés, et pour caractériser les stratégies primaires définissant la structure des communautés et les propriétés des écosystèmes. On ne sait pas vraiment si les caractères écologiquement importants aux échelles macro-écologiques sont variables ou encore une conséquence aux fines échelles dans l'espèce. Les auteurs ont mesuré la variation de caractères á l'intérieur de populations de plantes des prairies, les Festuca ovina L. et Koeleria macrantha (Ledeb.) Schult., pour vérifier l'hypothèse à savoir que la variation intraspécifique des caractères aux fines échelles guide la structure de la communauté locale. Les deux espèces montrent une importante variation génotypique pour tous les caractères. Les caractères liés à la grandeur chez les génotypes du K. macrantha observés en monoculture permettent de prédire leur performance dans des communautés herbacées modèles possédant à la fois une diversité génétique et spécifique. La même correspondance s'avère beaucoup plus faible chez la population expérimentale du F. ovina. De plus, les deux espèces montrent l'existence d'une relation positive entre la surface foliaire spécifique (SLA) et l'allocation à la masse des chaumes. La co-variation de ces caractères indique l'existence de compromis intraspécifiques dans le cycle vital et des stratégies de croissance, semblables à celles utilisées pour définir les stratégies primaires des plantes, lesquelles tamponnent potentiellement l'abondance des deux espèces et leur coexistence devant des défis environnementaux. [ABSTRACT FROM AUTHOR]

The majority of species used for revegetation in semi-arid western rangelands of North America are grasses, with few forbs and nearly no legumes. Astragalus filipes (Torr. Ex A. Gray) is a western North American legume and a promising candidate for use in rangeland revegetation, but assessments of plant species diversity and structure are necessary to determine which collections should be used to constitute a conservation unit or regional seed source. To address this issue, we characterized within-collection genetic diversity, identified genetically differentiated groups, and tested genetic correlations with environmental variables on 67 collections of A. filipes. Within-population genetic diversity was greatest for collections in Oregon and lowest for collections in British Columbia and central Nevada. Five genetically differentiated groups were detected: one with strong support from central Nevada, one with strong support from British Columbia, and three with weak support comprising all other collections throughout Oregon, Washington, California, Idaho, and Nevada. Although there was significant correlation between genetic and linear geographic distance matrices, there was no correlation between genetic and phenotypic, elevation, temperature, or precipitation distance matrices. These results show that geographic distance contributes to genetic differentiation, and that structured populations have occurred in northernmost and southernmost groups of collections of A. filipes. La majorité des espèces utilisées pour la revégétation des prairies montagnardes semi-arides de l'Ouest nord-américain comporte des herbacées, avec quelques arbustes et pratiquement aucune légumineuse. L'Astragalus filipes (Torr. ex A. Gray) constitue une espèce de légumineuse de l'Ouest nord-américain prometteuse pour assurer la revégétation des prairie semi-arides, mais on doit d'abord évaluer la diversité et la structure des espèces de plantes afin de déterminer quelles récoltes devrait-on utiliser pour constituer une unité de conservation ou source régionale de semences. Pour examiner cette question, les auteurs ont caractérisé la variation génétique intra récolte ont identifié des groupes génétiquement différenciés, et ont testé des corrélations génétiques avec des variables environnementales de 67 récoltes de l'A. filipes. Ils ont observé une plus grande diversité génétique dans les populations de l'Oregon et plus petite dans celles de la Colombie-Britannique et du Nevada. Ils ont décelé cinq groupes génétiquement distincts : un fortement supporté venant du centre du Nevada, un fortement supporté de la Colombie-Britannique, et trois faiblement supportés distribué dans les autres collections venant de l'ensemble de l'Oregon, Washington, Californie, Idaho et Nevada. Bien qu'on trouve une corrélation significative entre la génétique et les matrices de distances géographiques linéaires, il n'a y a pas de corrélation entre les matrices de distances génétiques et phénotypiques, l'élévation, la température ou la précipitation. Ces résultats montrent que la distance géographique contribue à la différentiation génétique et qu'il existe des populations structurées dans les groupes de collections venant des régions les plus nordiques et les plus méridionales de l'A. filipes. [ABSTRACT FROM AUTHOR]

We used a nondestructive method to estimate aerial and detritus productivity of the cordgrass Spartina densiflora Brongn. and evaluated the relative contribution of newly emerged and preexisting tillers to net aerial biomass and detritus production, the relative contribution of tiller detachment and leaf shedding to detritus production, and the incidence of crab (Neohelice (Chasmagnathus) granulata (Dana, 1851)), herbivory in relation to tiller age and its implications for tiller survival. Estimates of aerial and detritus productivity varied between 706.72 (SD = 153.38) and 786.15 (SD = 162.75) g·m–2·year–1 and between 1054.23 (SD = 224.49) and 1223.17 (SD = 246.84) g·m–2·year–1, respectively. These estimates of aerial production are far below the higher productivity estimates known for species of the genus Spartina but within the range of values obtained with nondestructive methods (i.e., 300–1500 g·m–2·year–1). Detachment of standing-dead tillers and leaf shedding contributed virtually in equal quantities to detritus production (i.e., 52% and 48% of the total detritus biomass, respectively). On the other hand, net aerial biomass production was highly dependent on tiller recruitment, with 67% of total biomass production contributed by the growth of tillers that emerged during the course of the study. However, crabs seem to graze on tillers irrespective of their age. Such nonselective crab grazing on tillers of different age together with the long tiller survival after crab grazing (often more than a year) suggests that crabs do not ostensibly affect S. densiflora production. [ABSTRACT FROM AUTHOR]

Xylem conduits increase in size from the apex downwards. While conduit tapering in the stem has often been reported to converge towards a common pattern among all plants, information on conduit tapering in small plants and roots is extremely scarce. We selected 10 small trees (height < 3 m) of Pinus cembra L. and Larix decidua Miller along an altitudinal gradient and measured diameter and conduit dimensions along stems and roots in the last annual ring. Sections of 10 µm were cut from wooden disks taken at different heights in the stem and in the roots and then stained with safranine. Slides were observed under a microscope, the lumen areas of conduits were measured and mean hydraulic diameters (Dh) calculated. Dh increased from stem tip (Dh at 1 cm from the apex averaged 10.75 µm; s = 2.33) to base (Dh from 20.70 to 30.54 µm), following a power trajectory (i.e., Dh = a·Lb, with L being the distance from the tip). Such degrees of conduit tapering may have a considerable effect in minimizing the hydraulic constraints. Despite trees at the treeline being older and smaller than in the subalpine forest (age: 28–70 years at the treeline; 18–39 years in the subalpine forest), conduit tapering did not differ significantly between sites, suggesting that tree height is the main factor controlling the basipetal increase in conduit lumens. In the roots, the increase in conduit dimensions continued towards their tips, even more steeply than in the stem. The widest conduits were measured around the root tips (around 40 µm). Conduit tapering resulted as a stable structural feature in small plants as well as in tall trees. [ABSTRACT FROM AUTHOR]

Berry crops in the southwestern Yukon were quantified from 1997 to 2008 at 10 locations along 210 km of the Alaska and Haines highways. We tested the hypothesis that the size of berry crops could be predicted from spring and summer temperature and rainfall of years t, t–1 (1 year prior), and t–2 (2 years prior). Six common species were studied in the boreal forest of the Kluane region: Arctostaphylos rubra (Rehd. & Wils.) Fern., Arctostaphylos uva-ursi (L.) Spreng. s.l., Empetrum nigrum L., Vaccinium vitis-idaea L., Geocaulon lividum (Richards) Fern, and Shepherdia canadensis (L.) Nutt.. For the first five species we counted berries on fixed 40 cm × 40 cm quadrats to obtain an index of berry production for the Kluane region for each of the 12 years, and for S. canadensis we counted berries on two tagged branches of 10 bushes at each location. Stepwise multiple regressions were utilized to predict the size of berry crops for each species. For all species, predictive equations could explain statistically 80%–96% of the variation in berry crops. Different weather variables characterized each plant species, and there was no common weather regression that could explain the variation in berry crops in all species. Rainfall and temperature from years t–1 and t–2 were typically the significant predictors. There was no indication of a periodicity in berry production, and 43%–60% of the quadrats counted had large berry crops at one year intervals, while other quadrats never had a high crop during the study interval. [ABSTRACT FROM AUTHOR]

Early-flowering species may be especially susceptible to occasional pollen limitation and, therefore, may benefit from a mixed-mating strategy that provides reproductive assurance. We studied cleistogamous (CL) and chasmogamous (CH) fruit set of spring-flowering Viola praemorsa Dougl. ex Lindl. along an elevational gradient in the Rocky Mountains, testing whether pollen limitation or allocation to CL reproduction covaried with timing of flowering onset, within and across sites. Contrary to predictions, we found no pollen limitation of reproduction at any site, and variation among sites in the pattern of allocation to cleistogamy was not related to growing season length. Differences in reproductive strategy between early- and late-flowering plants within sites were attributable to differences in plant size, with relative allocation to cleistogamy increasing with size. This pattern has been found in some other cleistogamous species, and may indicate a cost of large CH floral displays, perhaps associated with geitonogamy or herbivory. We found no experimental evidence for resource reallocation in response to CH reproductive output, although a weak negative relationship between CH and CL fruit set across a larger sample of unmanipulated plants suggests such a trade-off. The significance of cleistogamy may be clarified by studying how pollinator visitation, self-pollination, and herbivore damage vary temporally and with floral display size. [ABSTRACT FROM AUTHOR]

Plants maintain mutualistic symbioses with multiple symbiont genotypes that differ in the benefits they provide. To investigate differences in the effect of nitrogen-fixing Frankia on Alnus species, spore-producing (sp+) nodules from Alnus rubra Bong. and Alnus incana subsp. rugosa (Du Roi) Clausen and non-spore-producing (sp–) nodules from Alnus viridis subsp. crispa (Ait.) Turrill, A. rubra, and A. incana subsp. rugosa were collected from each of four different populations and used to inoculate all three Alnus species. As expected, sp+ Frankia produced significantly more nodules on all three species. However, A. crispa, which normally does not have sp+ nodules in the field, was more susceptible to a high level of infection by sp+ Frankia in general, and by any source of sp+ Frankia in particular, whereas A. incana subsp. rugosa, which has the highest abundance of sp+ in the field, was less susceptible to high levels of infection. This suggests that A. incana subsp. rugosa develops resistance to high levels of infection. The infectivity of an sp+ Frankia source on A. viridis subsp. crispa and A. rubra was positively correlated with the proportion of sp+ nodules on the site it was collected from, suggesting that the variation in the abundance of sp+ in the field is caused by sp+ Frankia with different levels of infectivity. There was no effect of Frankia sources on nodule allocation. Plant growth was positively correlated with the specific nodule mass and the specific nodule activity, and negatively correlated with the nodule number per plant. Sp+ Frankia resulted in significantly smaller plants in A. rubra. While there was no overall sp+ type effect on the growth of A. viridis subsp. crispa, the largest plants always resulted when they were inoculated with sp–, and the smallest with sp+ Frankia. Neither spore type nor inoculum source had any effect on the performance of A. rugosa. These results suggest that Alnus species remain susceptible to infection by both Frankia spore types, but are able to modulate the effectiveness of these spore types when they are the common symbionts in the field. [ABSTRACT FROM AUTHOR]

The ability to retain their photosynthetic capacity through the winter may be important for plants in boreal conditions, where the growing season is relatively short and winter temperatures fluctuate from severe freezing up to near 0 °C. The snow cover is an important protector for field-layer plants against both extreme freezing and excessive light, both of which could damage the photosynthetic apparatus. To understand the importance of wintertime photosynthetic activity for evergreen boreal dwarf shrubs, the photosynthesis of Vaccinium vitis-idaea L. was monitored in field conditions for one year. A dynamic model was used to determine the relative effect of temperature on the photosynthetic capacity. Our results show that V. vitis-idaea retains its photosynthetic capacity throughout the winter: its average photosynthetic capacity in winter was almost 25% of the yearly maximum measured. Changes in photosynthetic capacity over the year reflect the changes in air temperature with a certain delay, except in summer. Concentrations of soluble sugars remained high during the winter months, probably as a consequence of CO2 uptake under the snow cover. Our measurements indicated no significant damage to the leaf tissue over the winter, but suggest that photoinhibition may occur immediately after snowmelt. [ABSTRACT FROM AUTHOR]

The occurrence of various types of calcium oxalate crystals was studied in 251 species and subspecies of Cactaceae to determine whether they are useful characters for Cactaceae systematics. Crystal hydration states were identified by X-ray powder diffraction and polarizing microscopy as monoclinic calcium oxalate monohydrate (COM) and tetragonal calcium oxalate dihydrate (COD). Ninety-eight percent of taxa studied contained either COM or COD crystals, or both. Different morphologies of crystals were further defined by light microscopy and scanning electron microscopy as druses, raphides, styloids (prisms), and crystal sand. In particular, the preponderance of one of the hydration states (COM or COD) was characteristic for certain Cactus subfamilies. Data showed that in Pereskioideae, Maihuenioideae, and Opuntioideae COM is predominant, while in Cactoideae COD prevails. In the remainder of Cactoideae, the crystals were quite variable. In tribe Hylocereeae, many species form both COM and COD as well. In the genera Hylocereus, Epiphyllum, Selenicereus, and Weberocereus, COM forms were almost exclusively represented by raphides together with different crystal forms in their epidermal cells. In the remainder of the Cactoideae, crystals did not follow any observable patterns. Development of crystallographic standards for identifying crystal forms microscopically is proposed for future crystal studies. [ABSTRACT FROM AUTHOR]

Forest fragmentation is prevalent in regions with high human population density, but also with high biological diversity, such as southwestern China. Predicting potential changes in species composition in native forest ecosystems resulting from forest fragmentation is an important approach in assessing forest ecosystems and sustainable management of forests. The term nonconstituent species is proposed for plant species that occur in a natural landscape but are not native to it. We hypothesized that fragmentation of continuous forests significantly increases both the richness and the size of soil seed banks of nonconstituent species. To test our hypothesis we compared soil seed banks in three small fragments and one large tract of subtropical evergreen broad-leaved forest in Yunnan Province, southwestern China. In total, 249 species were identified in all soil samples from the four sites. Nonconstituent species represented 36.4%–61.5% of the total taxa and 33.8%–59.6% of total germinants from soil samples in the three forest fragments, but only 3.7%–7.9% of total taxa and 7.5%–9.4% of total germinants from soil samples in the continuous forest tract. Both richness and size of soil seed banks of nonconstituent species were greater under forest fragments than under continuous forest. A majority of nonconstituent species were native weeds and annual herbs with wind-dispersed seeds; most were present in soil seed banks but not in aboveground vegetation. We suggest that nonconstituent species in soil seed banks could be used as an indicator species group for assessing human disturbance. If so, the richness and size of soil seed banks of nonconstituent species could play an important role in quantifying disturbance in forests. [ABSTRACT FROM AUTHOR]

This article reviews published data on the likely occurrence of basidiomycetous endophytes in jungermannialean (leafy) liverworts and presents a new overview based on observations on freshly collected specimens supplemented with confirmation, by transmission electron microscopy, of dolipore septa in representative taxa. These associations are widespread in the Lophoziaceae and Arnelliaceae and sporadic in the Jungermanniaceae, Scapaniaceae, and Geocalycaceae. They are almost exclusively confined to taxa growing on well-drained, humus-rich substrata and are absent from epiphytes and species from bare rocks and waterlogged habitats. Cross-infection experiments between axenically cultured liverworts (Lophozia, Nardia, Diplophyllum, Southbya, and Aneura in the Metzgeriales) and their mycobionts revealed the associations to be host specific, in striking contrast with the wide host ranges previously recorded for rhizoidal ascomycetes in the Cephaloziaceae and other families. More vigorous growth of resynthesized basidiomycete associations compared with their axenic counterparts is indicative of nutritional benefits to the liverworts. The fungi enter their hosts via the tips of the rhizoids and develop distinctive distributions within the liverwort stem. In the Arnelliaceae, this comprises a central medullary strand; in the Lophoziaceae and Scapaniaceae, the ventral medulla contains a mosaic of infected and noninfected cells. In the latter, pegs of host wall material overgrow penetrating hyphae. Electron microscopy revealed that all of the endophytes have straight imperforate parenthesomes typical of heterobasidiomycetes. The fungi form hyphal coils that outlive the host cytoplasm, and digestion of the mycobionts, as seen in Aneuraceae and orchidaceous mycorrhizas, are absent. Closely similar mosaic infection patterns in Lophoziaceae and Scapaniaceae strenghten the link between the two families based on molecular data, but the present cross-infection and ultrastructural data indicate that the Calypogeia endophyte is ascomycetous rather than a member of the Sebacinaceae as reported previously. The distribution of basidiomycete associations in liverworts suggests that these probably arose several times and are more recent in origin than associations with glomeromycotean fungi. [ABSTRACT FROM AUTHOR]

We collected and mapped epigeous fruitbodies of both ectomycorrhizal (ECM) and saprobic fungi in an old-growth Quercus ilex L. Mediterranean forest within a permanent transect of 6400 m2 over three consecutive fruiting seasons. Out of 5382 fruitbodies, a total of 234 species were found, including 166 and 68 ECM and saprobic taxa, respectively. Both communities were mainly composed of rare species. Two genera, Russula and Cortinarius, accounted for 34.4% of ECM fruitbodies and 50% of species diversity. The three most abundant ECM species were Laccaria laccata (Scop.: Fr.) Berk. & Broome, Inocybe tigrina R. Heim, and Lactarius chrysorrheus Fr. The fruiting ECM community encompassed a few Mediterranean species and numerous broad host range temperate species. We also analysed the fruiting patterns in relation to forest structure, host composition, and natural canopy gaps. The results showed (i) a significant correlation of species richness to tree density, (ii) a richness decrease as the number of vegetation layers increases, and (iii) a preferential fruiting of some species near Q. ilex or Arbutus unedo L. Another noteworthy feature was that richness and production were greatly enhanced in canopy gaps. Selective fruiting was also observed among species. These results highlight the importance of forest structure and large woody debris for fungal conservation. [ABSTRACT FROM AUTHOR]

I compared the species composition and diversity of vascular plants in the herbaceous layer from a chronosequence of intensively managed spruce (Picea) plantations in three age-classes (5–7, 10–12, 14–16 years) with natural, mature stands (ca. 90 years) in southeastern New Brunswick, Canada. Total species richness (stand level) averaged 81–84 species in the three plantation age-classes compared with 64 species in the natural stands; richness of forest habitat species alone was 33–36 in the plantations and 37 in the natural stands. More fertile sites had significantly higher values for Hill's diversity indices (N[sub 0] , N[sub 1] , N[sub 2] ). Mean N[sub 0] , N[sub 1] , and N[sub 2] (subplot level) did not differ among stand types for all species, but N[sub 1] and N[sub 2] were significantly greater in the natural stands than in one or two plantation age-classes for forest habitat species alone. The two younger age-classes of plantations differed significantly in composition from the natural stands and the plantations became slightly more similar (Sørensen's index) to the natural stands with increasing age. One forest habitat species was lost and 24 others decreased in cover in the plantations. Tracking of plantations over a longer time period will be needed to determine whether these forest habitat species eventually regain their former abundance.Key words: chronosequence, forest harvesting, herbaceous layer, plantations, species diversity, species composition.L'auteur a comparé la composition en espèces et la diversité des plantes vasculaires au niveau de la strate herbacée d'une chronoséquence de plantations d'épinettes (Picea) intensivement aménagées appartenant à trois classes d'âge (5–7, 10–12, 14–16 ans), avec des peuplements naturels matures (ca. 90 ans) dans le sud-est du Nouveau-Brunswick, au Canada. La richesse totale en espèces (au niveau du peuplement) comporte en moyenne 81–84 espèces dans les trois plantations selon la classe d'âge, comparativement à 64 espèces dans les peuplements naturels. La richesse en espèces forestières seulement est de 33–36 dans les plantations, et 37 dans les peuplements naturels. Les indices de fertilité de Hill (N[sub 0] , N[sub 1] , N[sub 2] ) sont significativement plus élevés dans les sites les plus fertiles. Les valeurs moyennes de N[sub 0] , N[sub 1] et N[sub 2] (niveau de la sous-parcelle) ne diffèrent pas entre types de peuplement pour l'ensemble des espèces, mais les valeurs de N[sub 1] et N[sub 2] sont significativement plus élevées dans les peuplements naturels que dans les plantations d'une ou deux classes d'âge, dans le cas des espèces forestières prises séparément. La composition des deux classes d'âge de plantation les plus jeunes diffère significativement de celle des peuplements naturels, et les plantations deviennent légèrement similaires (indice de Sørensen) aux peuplements naturels avec l'augmentation de l'âge. La couverture d'une espèce d'habitats forestiers a été perdue et 24 autres ont vu leur couverture diminuer dans les plantations. Il sera nécessaire de suivre les plantations pendant une période de temps plus longue, pour déterminer si les espèces d'habitats forestiers regagnerons éventuellement leur abondance originale.Mots clés : chronoséquence, récolte forestière, strate herbacée, plantations, diversité en espèces, composition en espèce.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Development of microsatellite markers for sunflower (Helianthus annuus L.) was performed to estimate their frequency, nature (structure), levels of polymorphism, usefulness for genotype identification, and calculation of genetic relationships between inbred lines representing the species diversity. Isolation was performed from a small-insert genomic library followed by hybridization screening using oligonucleotide probes containing different nucleotide arrays. In this work, 503 unique microsatellite clones were sequenced and 271 PCR primer sequences bordering the microsatellite repeat were designed. For polymorphism assessment, 16 H. annuus germplasm accessions were checked and 170 of the primers tested were shown to be polymorphic for the selected lines. The polymorphic microsatellites produced an average of 3.5 alleles/locus and an average polymorphism information content (PIC) of 0.55. The most frequently found motifs within polymorphic simple-sequence repeats (SSRs) were: (GA)[sub n] , (GT)[sub n] , (AT)[sub n] , followed by trinucleotides (ATT)[sub n] , (TGG)[sub n] and (ATC)[sub n] , and the tetranucleotide (CATA)[sub n] . Most of the 170 SSRs obtained showed important differences in the 16 reference inbred lines used for their characterization. In this work, 20 of the most informative SSRs destined to sunflower genotyping and legal fingerprinting purposes are fully described.Key words: sunflower, molecular markers, microsatellites, simple-sequence repeats.Le développement et caractérisation de marqueurs microsatellites chez le tournesol (Helianthus annuus) ont été accomplis pour estimer leur fréquence, naturesse (structure), niveau du polymorphisme, utilité pour l'identification et calcule des relations génétiques entre lignées endocries qui représentent la diversité génétique du tournesol. L'isolement a été accompli en utilisant une banque génomique de petits inserts de tournesol. Dans ce but, le criblage basé sur l'hybridation a été effectué en utilisant des sondes oligonucléotidiques composées de différents arrangements de nucléotides. 503 clones microsatellites positifs ont été séquences et 271 séquences d'amorces adjacentes à ces microsatellites ont été synthétisées. Pour l'évaluation du polymorphisme, 16 sources de accessions du H. annuus ont été vérifiées et 170 des amorces testées ont montré un polymorphisme pour les lignées étudiées. Les microsatellites polymorphiques ont produit une moyenne de 3.5 allèles par gène et une moyenne de 0.5 PIC (contenu en information de polymorphisme). Les motifs les plus fréquemment trouvés dans les SSR polymorphes étaient: (GA)[sub n] , (GT)[sub n] , (AT)[sub n] , suivis des trinucléotides (ATT)[sub n] , (TGG)[sub n] et (ATC)[sub n] et du tetranucléotide (CATA)[sub n] . La majeure partie des 170 séquence simple répétitive (SSR) obtenues ont montré des différences importantes dans les 16 lignées pures de référence utilisées pour sa caractérisation, 20 des SSR les plus instructives en termes d'information destinée à la détermination de génotypes de tournesol, et d'empreintes digitales dans un but légal, sont amplement décrits dans ce travail.Mots clés : tournesol, marqueur moléculaire, microsatellites, séquence simple répétitive.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Eight dinucleotide microsatellites were developed in Eucalyptus sieberi L. Johnson (silvertop ash), a member of the subgenus Eucalyptus. Transfer of six of these to the subgenus Symphyomyrtus and their Mendelian inheritance are demonstrated using a full-sib cross in Eucalyptus nitens. Genetic diversity parameters are presented for the eight loci based on a sample of 100 old-growth E. sieberi trees from a single natural stand. One locus, Es266, had an atypically high fixation index, and significantly deviated from Hardy-Weinberg equilibrium genotypic proportions, indicating the likely presence of null alleles. Two of the loci, Es076 and Es140, had many alleles that differed in size by only a single base pair, possibly because of short poly(A) or poly(T) stretches in their flanking regions. These two loci were by far the most polymorphic, but were difficult to score reliably on a capillary DNA sequencer. Reliability of scoring of these two one-base microsatellite loci was markedly improved by the incorporation of internal reference alleles into each sample analysed.Key words: SSRs, single base pair alleles, null alleles, internal reference alleles.Huit microsatellites dinucléotidiques ont été développés chez l'Eucalyptussieberi L. Johnson (« silvertop ash »), un membre du sous-genre Eucalyptus. Le transfert de six de ces microsatellites chez le sous-genre Symphyomyrtus ainsi que leur hérédité mendélienne sont démontrés à l'aide d'un croisement entre plantes soeurs chez l'E. nitens. Des paramètres de diversité génétique sont présentés pour les huit locus à partir d'un échantillon de 100 arbres de l'E. sieberi provenant d'une seule forêt naturelle établie de longue date. Un locus, Es266, montrait un indice de fixation anormalement élevé, indiquant la présence vraisemblable d'allèles nuls. Deux des locus, Es076 et Es140, possédaient de nombreux allèles qui ne différaient que par un seul nucléotide, potentiellement en raison de courtes suites poly(A) ou poly(T) dans les régions adjacentes. Ces deux locus étaient de loin les plus polymorphes, mais étaient difficiles à génotyper de façon fiable sur un séquenceur d'ADN à capillaires. La fiabilité du génotypage de ces deux microsatellites mononucléotidiques a été nettement améliorée en incorporant des allèles de référence interne dans chaque échantillon analysé.Mots clés : SSR, allèles mononucléotidiques, allèles nuls, allèles de référence interne.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]