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The taxonomic classification of dwarf mistletoes (Arceuthobium spp., Viscaceae) in series Campylopoda requires a multi-trait approach, integrating plant genetics, morphologies, and phenologies as well as their host and geographic distributions. Thus, competing interpretations on the contribution of these traits to defining species and subspecies boundaries has spurred considerable debate. Accordingly, the recent reclassification of 12 previously recognized species in ser. Campylopoda to separate subspecies of Arceuthobium campylopodum in the Flora of North America (FNA) has furthered this debate. We contend that these taxa deserve separate species recognition, while subspecies described prior to and after the recombination of ser. Campylopoda taxa in the FNA also deserve recognition. Herein, we provide evidence that the treatment in the FNA does not adequately reflect the diverse morphological, geographic, host, and phenological differences across the series, and hence, we maintain that the reclassification of ser. Campylopoda taxa was not justified according to empirical evidence published prior to and following the FNA treatment. We conclude our critique of the FNA treatment of ser. Campylopoda by advocating for the continued application of the Hawksworth and Wiens' classification system, with minor modifications to the constitution of the series. [ABSTRACT FROM AUTHOR]

Mistletoe detection and sampling remain challenging for arborists, dendrologists, forest ecologists, and other specialists because of the limited access to host tree canopy. In this review, smart solutions for mistletoe detection based on airborne platforms are discussed. Airborne remote sensing (ARS) has the developing potential to provide rapid, accurate, and cost-efficient detection and research of mistletoe on tree level and large areas within the complex terrain. Herein, such mistletoe ARS research methods as image spectroscopy, infrared thermography, light detection and ranging, and structure from motion are overviewed. [ABSTRACT FROM AUTHOR]

The article presents a study related to cretaceous flora and fauna of the Sustut Group near the Sustut River, northern British Columbia, Canada. It mentions that the rarity of vertebrate fossils from the region, a detailed understanding of the stratigraphic context for RBCM P900 is crucial for interpreting its significance to broader patterns of dinosaur biogeography in western North America during the Late Cretaceous.

Paleogene sediments of the Huntingdon Formation, a correlative to the Chuckanut Formation of neighbouring Washington State, USA, are exposed in the Greater Vancouver area, British Columbia, Canada. Palynology and plant macrofossils suggest the Kanaka Creek section is Paleocene rather than Eocene in age. Detrital zircon dating is less decisive, yet indicates the Kanaka rocks are no older than Maastrichtian. Analyses of plant macro- and micro-fossils suggest an early to middle Paleocene age for the Kanaka fossil flora. Paleocene indicators include macrofossils such as Platanus bella, Archeampelos, Hamamelites inequalis, and Ditaxocladus, and pollen taxa such as Paraalnipollenites, Triporopollenites mullensis, and Duplopollis. Paleogene taxa such as Woodwardia maxonii, Macclintockia, and Glyptostrobus dominate the flora. Fungal spores including the Late Cretaceous Pesavis parva and the Paleogene Pesavis tagluensis are notable age indicators. Physiognomy of 41 angiosperm leaf morphotypes from Kanaka Creek yields mean annual temperatures in the microthermal to lower mesothermal range (11.2 ± 4.3 to 14.6 ± 2.7 °C from leaf margin analysis; 14.8 ± 2.1 °C from Climate Leaf Analysis Multivariate Program), with mild winters (cold month mean temperature 3.9 ± 3.4 °C). Paleoclimate was cooler than the upper Paleocene and Eocene members of the Chuckanut Formation. Mean annual precipitation is estimated at ∼140 cm with large uncertainties. The Kanaka paleoflora is reconstructed as a mixed conifer–broadleaf forest, sharing common taxa with other western North American Paleocene floras and growing in a temperate moist climate. Kanaka Creek is a rare coastal Paleocene plant locality that provides new insights into coastal vegetation and climate prior to the Paleocene–Eocene Thermal Maximum. [ABSTRACT FROM AUTHOR]

Landscape-scale prescribed burning may be appealing for natural community restoration due to operational efficiency and possible heterogeneity in fire effects across broad spatial scales. We monitored plant community responses for >15 years with variable prescribed fire frequencies applied across a Missouri Ozarks landscape stratified into distinct ecological site types. Through the study period, burning had no effect on the overstory tree density or basal area. Midstory stem densities decreased rapidly in periodically burned units and more gradually with annual fire. Burning increased total ground flora cover and the cover of forbs, grasses, and legumes. The effect of burning on species richness differed among site types, with increased species richness through time on exposed slopes. There was no effect of prescribed burning on species richness on two of three protected slope site types, and annual burning decreased species richness in upland waterways. Among the site types, the upland waterways had the most species associated with pre-burn communities. We conclude that (i) burning consistently increased cover of ground layer vegetation across the landscape, while decreasing the midstory stem densities, and (ii) site type moderated ground flora richness response, with more pronounced effects of prescribed burning on exposed sites than on protected sites. [ABSTRACT FROM AUTHOR]

The Carboniferous - early Permian plant genus Lesleya is a characteristic component of 'dryland floras' that occupied a wide range of moisture-stressed, well-drained environments in tropical regions of Euramerica. Fossil records of Lesleya are almost exclusively found in basinal lowlands. For example, occurrences in Early Pennsylvanian-age, seasonally dry, parautochthonous deposits in basinal lowlands of North America (e.g., Illinois Basin, USA) indicate that Lesleya lived in that region in low-altitude (lowland) paleoenvironments during dry climatic intervals. In this paper, we document the first occurrence of Lesleya during the Carboniferous on the Iberian Massif, in lower Gzhelian (Upper Pennsylvanian) strata of the Douro Carboniferous Basin, in northwestern Portugal. This newly discovered occurrence includes a new species, Lesleya iberiensis sp. nov., recognized on the basis of natural molds of leaves. The Portuguese Lesleya fossils are from upland intramontane deposits and occur between coal beds. Their fossil remains are preserved in mica-rich shales that were deposited between sandstone-dominated fluvial and shale-dominated lacustrine deposits, suggesting that this megaflora was deposited near freshwater bodies. These new data provide evidence that this megaflora grew in mountain riparian environments within the Variscan orogen, either in localized, well-drained areas or during drier climatic intervals in the Late Pennsylvanian. [ABSTRACT FROM AUTHOR]

Logging and burning of the resultant woody debris is a management tool to reduce fire risk. Burning of the debris as piles affects the underlying soil biota and soil physical and (or) chemical properties. The resulting disturbance created by the burns may create opportunities for the establishment and spread of non-native plant species. Here, we test three restoration treatments on recent, approximately 1-year-old, pile burn scars, including an arbuscular mycorrhizal fungal (AMF) inoculant (present or absent), a ground cover (straw or no straw added), and different seeding types (native seed mix, agronomic seed mix, and no seed). The most effective treatment in reducing undesired non-native species cover was the seeding of agronomic species; here 'native' and 'non-native' groups exclude sown agronomic species. Undesired non-native cover was 15.1% in plots with no seed, 9.1% in plots with native seed added, and 3.5% in plots with agronomic seed added. Total vegetation cover, mostly through the increase of agronomic species, was increased by seeding and by the application of straw cover. Commercial AMF inoculum was an ineffective treatment, suggesting that a better understanding of host specificity is warranted. Restoration efforts should be directed at burn scar sites after burning to ameliorate the effects of invasive species colonization, and the use of agronomic species may prevent non-native invasive plants from establishing. [ABSTRACT FROM AUTHOR]

Cambial activity and the formation of secondary xylem were investigated in the main stem of three arboreal leguminous species and one liana. To compare the seasonal vascular cambium behavior of these species, two methods were concurrently applied: induction of injury in the vascular cambium and anatomical analysis of the vascular cambium and adjacent zones (differentiation zone). One tree species, Pseudopiptadenia contorta (DC.) G.P.Lewis & M.P.Lima, was sampled in three forest formations: alluvial, submontane, and montane. Two more tree species, Apuleia leiocarpa (Vogel) J.F.Macbr. and Pseudopiptadenia leptostachya (Benth.) Rauschert, were sampled in submontane and montane forest, respectively. Dalbergia frutescens (Vell.) Britton var. frutescens, a liana, was sampled in montane forest. All species investigated showed distinctive formation of annual growth rings. Reactivation of the vascular cambium was observed at the end of spring, and it remained active during the summer. Thereafter, cambial activity either ceased or declined dramatically at the end of autumn. Similar to the tree species studied, cambial activity in D. frutescens var. frutescens showed similar seasonal cambial activity throughout the year. Based on both direct and indirect methods, our results showed that cambial activity and wood formation only occurred during the rainy season, suggesting the potential of these species for use in dendrochronological studies. [ABSTRACT FROM AUTHOR]

Studies on floral development have widened the knowledge on the floral morphology of Araceae, particularly in genera delimited through classical taxonomic treatments. In Pothoideae, floral ontogenetic studies are limited to some representatives of Pothoidium Schott and Pothos L. and only one species of Anthurium Schott, with no focus on gynoecium. This background reveals a lack of ontogenetic data on the largest genus in the clade. This paper presents gynoecial ontogeny of species circumscribed in different sections of Anthurium, describes gynoecial developmental patterns, and evaluates the relevance of ontogenetic characteristics in the taxonomy of the sections studied. New data for the Araceae include the recognition of four floral developmental phases, the carpellary nature of the ovarian septum, and the development of the symplicate and synascidiate zones of the gynoecium. The apical septum described in Anthurium scandens (Aubl.) Engl. is first reported for the genus in this study. We also highlight the importance of these ontogenetic data as new information for the Pothoideae within Araceae and to understand the notable phases of floral development in the reproductive biology of Anthurium. [ABSTRACT FROM AUTHOR]

The distribution of northern British Columbia alpine plants is poorly documented. To improve our understanding of the flora of this vast, remote region, we collected more than 11 000 specimens from 65 mountains during 2002-2011. Most of these locations had not been visited by botanists. Of the more than 400 species we have collected, two are new to the province, others represent significant range extensions. Twelve species share elements of a disjunct distribution that has apparently not been previously recognized and consists of three regions: (1) northwestern North America; (2) Beartooth Plateau; and (3) northern Colorado. These 12 species appear to be absent from the extensive areas of suitable habitat that occur in the intervening areas. The most reasonable explanation for this pattern is that these species, adapted to arctic-alpine tundra conditions, migrated throughout western North America during the Pleistocene, a time when suitable habitat was much more widespread than now, and subsequently went extinct in many areas as the climate warmed during the Holocene. [ABSTRACT FROM AUTHOR]

Resource sharing between connected ramets can be advantageous for clonal plants. However, widespread vascular integration bears the risks of enhanced internal pathogen spread, which may be one of the most prominent disadvantages of clonal growth. In this paper we analyzed patterns of internal virus spread in ramet groups of the stoloniferous herb L. (white clover) and investigated the effect of leaf ontogeny on intraclonal disease development. We inoculated single leaves of T. repens with White clover mosaic virus and analyzed the infection status of ramets at different distances from the point of infection and in leaves from different developmental stages. White clover mosaic virus infected all young developing plant parts positioned on basal branches or on the main stolon. Leaf ontogeny strongly affected disease development, and fully mature leaves on the main stolon remained virus free. The pattern of plant-internal virus spread was not affected by heterogeneous light conditions. Despite the well-described advantages of physiological integration, our data suggest that clonal integration may lead to negative selection pressures on clonal growth in pathogen-prone environments. [ABSTRACT FROM AUTHOR]

The main goal of this study was to examine different phyllotactic patterns and pattern transitions in seedlings of eastern white cedar ( L.). Four phyllotactic patterns were observed on the main stem of T. occidentalis: tetracussate, tricussate, (3, 5) spiral, and decussate. Only one phyllotactic pattern was observed on the side branches of T. occidentalis: decussate. Four types of phyllotactic pattern transition were observed: tetracussate to decussate, tetracussate to tricussate, tricussate to (3, 5) spiral, and (3, 5) spiral to decussate. For each phyllotactic pattern, the following phyllotactic parameters were examined using histological sections: divergence angle, plastochrone ratio, leaf insertion angle, parameter Г, and apical angle of the shoot apical meristem (SAM). Even though they varied widely, the phyllotactic parameters measured in T. occidentalis seem to fall within ranges observed in other plants for specific phyllotactic patterns. The results indicate that it is not possible to discriminate between the four different phyllotactic patterns observed on T. occidentalis by using the plastochrone ratio, leaf insertion angle, parameter Г, or apical angle of the SAM. In contrast to continuous transitions, where there is a good correlation between phyllotactic parameters, there was no correlation between the phyllotactic pattern (characterized by a given divergence angle) and other phyllotactic parameters in the discontinuous transitions observed in T. occidentalis. [ABSTRACT FROM AUTHOR]

Sexual reproduction is crucial for plant populations to track and adapt to climate change, but it is uncertain to what degree arctic vascular plants reproduce by seed. Several studies on arctic species show low germination. To re-examine seed germination and evaluate factors limiting sexual reproduction, seeds of 6-22 arctic species were germinated in five different, increasingly more realistic, conditions. Thirteen out of 15 species that were tested in an earlier study in Svalbard, Norway, germinated better in our study. Compared with perceived optimal conditions in a growth chamber, average germination per species was 6%-52% lower in five out of six species germinating at a colder temperature in soil, 36%-64% lower when germinating outdoors in soil, 49%-91% lower when germinating in a moss covered moraine, and 55%-91% lower when germinating in open soil on a moraine. Germination outdoors was below 5% in 10 out of 13 species and not correlated to germination in perceived optimal conditions. The high germination compared with earlier studies suggests that climate warming has already increased seed viability. However, caution should be taken when evaluating species-recruitment potential based on laboratory studies, as germination in the field was limited by species-specific responses to low temperatures, moisture, predation, and safe-site availability. [ABSTRACT FROM AUTHOR]

Clonal plant species dominate meadow vegetation where grazing can generate spatial heterogeneity at different scales and can select for species that express particular sets of clonal traits. This in situ study aimed to characterize fine-grained spatial patterns of defoliation (<1 m) induced by contrasting cattle grazing intensities and to link these spatial patterns with the abundance of species-specific clonal traits. Using correlogams and synthetic spatio-temporal indices, the heterogeneity of vegetation height and leaf damage was monitored along a cattle grazing gradient. Species were identified and their clonal traits retrieved from the database CLO-PLA3. Under moderate grazing, fine-grained spatial patterns of defoliation were not stable over time. Defoliation was heterogeneous during the first months of the grazing season and then became homogeneous. Intensive grazing generated homogeneous defoliation, regardless of the date. In the study meadow, grazing gave rise to communities containing a greater abundance of annual species. However, clonal traits assumed to enable clonal fragments to benefit from heterogeneity do not seem advantageous. Increasing grazing intensity promoted species with clonal traits expected to minimize costs associated with clonality (aboveground clonal growth forms, short-distance lateral spread, and (or) short-lived connections). Ungrazed conditions favoured species with clonal traits associated with a high competitive ability. [ABSTRACT FROM AUTHOR]

Trees owe their growth in girth to cambial activity that gives rise to secondary conducting tissues. Since cambium originates from the primary vascular meristem, called procambium, the main objective of the present study was to analyse the changes occurring during transition from procambium to cambium in Diospyros lotus L., characterized by the occurrence of double-storied cambium. In this species, procambium and primary vascular tissues are present only within the bud, whereas just below this level, cambium and secondary vascular tissues occur. Procambium differentiates as a continuous cylinder, which as a whole transforms into cambium during further development. Commonly used criteria distinguishing procambium and cambium - that is, the appearance of periclinal divisions, intrusive growth of meristematic cells, presence of rays, and primary versus secondary nature of derived vascular tissues - were analysed in D. lotus. All these features, however, were present in procambium, making the sharp distinction between both stages of vascular meristem based on these criteria difficult. In addition, the formation of fusiform and ray initial storeys in D. lotus was shown to appear in the third year of cambium activity and become more distinct with cambium age. The double-storied structure may result from the genetic control of cell fate and (or) the presence of epigenetic patterns determining cellular arrangement. La croissance des arbres en diamètre provient d'une activité cambiale donnant naissance aux tissus conducteurs secondaires. Sachant que le cambium tire ses origines du méristème vasculaire primaire, ou procambium, l'auteur s'est proposé d'analyser les modifications survenant au cours de la transition du procambium au cambium chez le Diospyros lotus L., caractérisé par la présence d'un cambium à deux étages. Chez cette espèce, l'on ne retrouve le cambium et les tissus vasculaires primaires que dans le bourgeon, alors que l'on retrouve immédiatement sous cet étage, le cambium et les tissus vasculaires secondaires. Le procambium se différencie comme un cylindre continu se transformant dans l'ensemble en cambium au cours du développement ultérieur. Les auteurs ont analysé, chez le D. lotus, les critères usuels distinguant le procambium et le cambium, c.-à-d. apparence des divisions périclinales, croissance intrusive des cellules méristématiques, présence de rayons, et nature primaire vs. secondaire des tissus vasculaires dérivés. Cependant, l'ensemble de ces caractères se retrouve déjà dans le procambium, rendant ainsi difficile la distinction nette entre les deux stades du méristème vasculaire, basée sur ces caractères. De plus, on démontre que la formation des couches de cellules initiales des cellules fusiformes et des rayons chez le D. lotus n'apparaît qu'après trois ans d'activité cambiale, tout en devenant plus distinctes avec l'accroissement en âge du cambium. La structure en deux étages pourrait résulter d'un contrôle génétique du sort des cellules et (ou) de la présence de patrons épigénétiques déterminant l'arrangement cellulaire. [ABSTRACT FROM AUTHOR]

Sexual dimorphisms are often found in reproductive allocation and vegetative growth, and these sexual dimorphisms may lead to a reduction of subsequent reproductive allocation in woody dioecious species. However, in some species, female-biased reproductive allocation does not result in a reduction of subsequent reproductive allocation in females. To clarify the mechanisms underlying this phenomenon, we studied the dioecious tree Zanthoxylum ailanthoides Sieb. et Zucc., in which leafing and inflorescence development occur sequentially. Reproductive allocation and vegetative growth were examined in both sexes at the shoot and tree levels. At tree level, they were evaluated with respect to flowering frequency and annual tree-ring width over 5 years. Reproductive allocation per shoot in females was 1.7× that in males. The ratio of reproductive to total current-year shoots per tree in males was 1.2× that in females. Reproductive allocation in females exceeded that of males by a factor of 1.5 at the tree level, which was less than that at the shoot level, owing to modular integrity. Biased vegetative growth was not detected at the leaf, shoot, or tree level, suggesting that a compensatory mechanism is not employed by this species. The results support the conclusion that a species-specific phenophase sequence of Z. ailanthoides enables females to achieve consecutive reproductive allocation. [ABSTRACT FROM AUTHOR]

Regrowth of injured plants occurs from dormant meristems. Its success is known to be dependent on extrinsic factors, such as the severity of an injury and nutrient availability, although little is known about the effect of intrinsic factors. We conducted a growth-chamber experiment with the short-lived root-sprouting herb Rorippa palustris (L.) Besser, where we evaluated the role of bud origin on plant regrowth after disturbance. In particular, we investigated whether shoots sprouting from either axillary or adventitious buds differ in compensatory growth and architecture. We triggered resprouting from axillary versus adventitious buds by two levels of disturbance: (i) removal of the whole aboveground biomass, with axillary buds on the stem base and adventitious buds on roots left intact; and (ii) removal of whole aboveground biomass including axillary buds on the stem base, and only adventitious buds left intact. Despite the fact that the adventitious buds were larger and contained more leaf primordia than axillary buds at the time of disturbance, the latter preferentially resprouted when both types of buds were present. Both axillary and adventitious shoots compensated for lost aboveground biomass; nevertheless, only axillary shoots compensated for fruit production. Shoot reiteration after injury was only partial in both types of shoot; however, adventitious shoots in differed more in their architectural characteristics than axillary shoots did. We confirmed that the output of plant regeneration after disturbance depends also on intrinsic factors such as the origin of the buds. [ABSTRACT FROM AUTHOR]

A region of contrastively wetter and milder climate occurs in inland northwest North America, separated from similar climates of the Pacific coast by 200–400 km. Researchers have long noted that numerous vascular plants divide their ranges between the interior wetbelt and coastal regions, although many such disjunctions have hitherto gone undocumented. Here I summarize all vascular plants shared between coastal and interior wetbelt regions, disjunct by at least 200 km. These disjunct taxa are assigned to north-coast and south-coast lists according to whether the coastal portions of the ranges occur primarily north or south of the southern limits of maximum continental glaciation. A list of interior wetbelt endemic taxa is also presented, focusing on those that occur at forested elevations. Presence/absence for coastal disjunct and endemic taxa were assigned to grid of 1° × 1°latitude–longitude cells. Using this grid, concentrations of disjunct and endemic taxa were detected, and total values per cell were tested in linear regression for a relationship to mean annual precipitation. In total, 116 coastal disjunct taxa were detected, 31 of them north-coastal and 85 south-coastal. Interior wetbelt endemic and subendemic taxa total 95, and of these, 46 were found primarily at forested elevations. North-coast taxa were found over a wide latitudinal range both north and south of the glacial limits, and their distribution had a weak positive relationship with annual precipitation. South-coast and endemic taxa were found mostly south of the glacial limits, and their distribution did not correlate to annual precipitation. The greatest concentrations of south coastal disjunct and endemic taxa occurred in the Clearwater region of north-central Idaho; a region noted by previous researchers to be a likely ice-age refugium for wet-climate dependent plants and animals. Inferences are made from these patterns, both for biogeographical understanding of the roles played by the interior wetbelt and some regions connecting to the coast, as well as for preservation of biodiversity and ecosystem continuity. On retrouve une région contrastée humide à climat plus doux à l’intérieur des terres dans le nord-ouest de l’Amérique du Nord, laquelle est éloignée de climats similaires sur la côte du Pacifique de 200 à 400 km. Les chercheurs ont noté depuis longtemps que de nombreuses plantes vasculaires divisent leurs aires entre la ceinture humide dans les terres et les régions côtières, bien que de telles disjonctions soient restées non documentées jusqu’ici. L’auteur résume l’ensemble des plantes vasculaires partagées entre les régions côtières et la ceinture humide dans les terres, séparées par au moins 200 km. Il attribue ces taxons disjoints aux listes côte nord et côte sud, selon que les portions côtières des aires se retrouvent prioritairement au nord ou au sud des limites sud de la glaciation continentale maximale. Il présente également une liste d’espèces endémiques de la ceinture humide de l’intérieur, avec accent sur celles qui se retrouvent dans les forêts de haute élévation. Il a attribué à des grilles cellulaires de 1°× 1°degré de latitude–longitude, la présence/absence des taxons disjoints et endémiques. à l’aide de cette grille, l’on a pu détecter les concentrations de taxons disjoints et endémiques, et tester les valeurs totales par régression linéaire afin d’établir une relation avec la précipitation annuelle moyenne. Au total, on a décelé 116 taxons disjoints, 31 d’entre eux nord côtiers et 85 sud côtiers. Les endémiques de la ceinture à l’intérieur des terres regroupent 95 taxons, 46 d’entre eux retrouvés prioritairement dans les forêts en altitude. On retrouve les taxons endémiques nord côtiers sur une grande aire latitudinale, surtout à la limite glaciaire sud, et leur distribution ne montre pas de corrélation avec la précipitation annuelle. Les plus grandes concentrations de taxons endémiques disjoints sud côtiers se retrouvent dans la région de Clearwater au centre nord de l’Idaho, une région désignée par des chercheurs antécédents comme refuge probable de l’âge glaciaire pour les plantes et les animaux dépendants d’un climat humide. À partir de ces patrons, l’auteur déduit des conséquences &#x [ABSTRACT FROM AUTHOR]

The allometric effects of Corispermum macrocarpum Bunge in response to soil nutrient content, water content, and population density were compared in a greenhouse experiment. The results showed that biomass allocation was size-dependent. The plasticity of roots, leaf allocation, and reproductive effort was “true” plasticity (i.e., changing biomass allocation in response to environmental conditions regardless of plant size), and no plasticity was detected in stem allocation in response to soil nutrient variation. At a low soil nutrient content, C. macrocarpum allocated more resources to reproductive organs than to roots and leaves at equivalent plant size, but the value of root allocation was consistent because of the trade-off between the effects of plant size and soil nutrient content. In the response to soil water variation, the plasticity of root allocation and reproductive effort was true plasticity, the plasticity of stem allocation was “apparent” plasticity (i.e., changing biomass allocation in response to plant size regardless of environmental conditions), which was caused by plant size, but there was no plasticity in leaf allocation. Except for the true plasticity of root allocation, there was no plasticity in stems, leaves, and reproductive organs in response to population density. [ABSTRACT FROM AUTHOR]

We conducted a fertilization experiment in polygon fens that were grazed by Greater Snow Geese on Bylot Island (Canadian Arctic) to determine whether mosses can interfere with nutrient cycling and thereby prevent a direct fertilizing effect of herbivore faeces on vascular plants. We measured the effects of nitrogen (N), phosphorus (P), and faecal addition on growth parameters and nutrient content of graminoids and mosses over a 2 year period. Growth and nutrient content of graminoids were enhanced only for high levels of N addition (5 g·m–2 per season), and showed little response to P addition. Although the growth of mosses showed a slight response to N or P addition, it is primarily nutrient content that was generally enhanced at all levels of fertilization. In many cases, stronger responses were detected when N and P were applied in combination, rather than singly. Addition of goose droppings had no effect on any measured parameters. Our results suggest that bryophytes act as a natural barrier by absorbing nutrients from external additions, thus blocking the access of highly assimilable nutrients to graminoid plant roots. At increased levels of N addition, bryophytes were apparently saturated so the nutrient surplus leached down to roots and was thus available for graminoid plant growth. The presence of a thick moss layer likely explains why the deposition of faeces by herbivores such as geese has no effect on graminoid growth in arctic polygon fens. [ABSTRACT FROM AUTHOR]

The herbaceous perennial Chrysosplenium tetrandrum (Lund ex Malmgr.) Th. Fr. (Saxifragaceae) is a self-pollinating, circumpolar species with a broad latitudinal distribution and a disjunct North American range. The southernmost populations are isolated in the Rocky Mountains of Colorado and Montana, distantly separated from elements of the main range, which is largely coincident with known glacial refugia (e.g., Beringia) and recently deglaciated regions. We employed analyses of inter-simple sequence repeats (ISSRs) and morphology to determine patterns of variation within the western North American range of C. tetrandrum and test hypotheses of glacial population history and reproductive strategy. Analyses revealed very low estimates of range-wide genetic differentiation (θII = 0.085) and diversity (HS = 0.077, HT = 0.084), which are similar to levels found in other arctic plant species and have been primarily attributed to recent population establishment. Low levels of genetic differentiation among populations of Alaska (θII = 0.072), British Columbia (θII = 0.088), and Washington (θII = 0.058) suggest recent bottleneck or range expansion events. Both the Colorado and Alaska regions showed strong differentiation from each of the other regions, suggesting long-term isolation. The non-association between morphological and genetic variation indicates the effects of phenotypic plasticity or sexual reproduction. [ABSTRACT FROM AUTHOR]

We examined the relationship between root carbohydrates and sprouting efficiency in four hybrid aspen (Populus tremula × Populus tremuloides) clones. Our hypothesis was that the interclonal variation in sprouting efficiency is due to the concentration of carbohydrates. In addition to that relationship, we wanted to study seasonal fluctuation of carbohydrates and how the –18 °C storage conditions of stock plants affects the stability of carbohydrate content and thus sprouting ability of roots cuttings. Clones varied in root carbohydrate content, and sucrose showed the greatest variation throughout the year. Sucrose levels were highest in the clone with the highest sprouting efficiency and lowest in the clone with the lowest sprouting efficiency. Carbohydrate concentrations were highest in winter and lowest in early autumn. In general, root cuttings sprouted most efficiently when root carbohydrate levels peaked. Although root cuttings taken from frozen (–18 °C) stock plants sprouted poorly in summer and autumn, they had high and almost constant carbohydrate concentrations throughout the year. [ABSTRACT FROM AUTHOR]

The formation of vein patterns in leaves has captivated biologists, mathematicians, and philosophers. In leaf development, files of vein-forming procambial cells emerge from within a seemingly homogeneous subepidermal tissue through the selection of anatomically inconspicuous preprocambial cells. Although the molecular details underlying the orderly formation of veins in the leaf remain elusive, gradually restricted transport paths of the plant signaling molecule auxin have long been implicated in defining sites of vein differentiation. Several recent advances converge to more precisely define the role of auxin flow at successive stages of vascular development. The picture that emerges is that of vein formation as a self-organizing, reiterative, auxin-transport-dependent process. [ABSTRACT FROM AUTHOR]

Two men were leaders in the development of plant physiology research in Canada: Professor G.W. Scarth at McGill University and Professor G.H. Duff at the University of Toronto. The latter was the driving force behind the formation of the CSPP in 1958. The contributions of these two men and their graduate students to plant physiology research in Canada are briefly summarized. [ABSTRACT FROM AUTHOR]

Managers increasingly use prescribed fire in oak forests to decrease fire-sensitive species, increase understory light, and improve oak (Quercus spp.) regeneration. To better understand woody seedling response to burning, single and repeated (3×) prescribed fires were implemented over 6 years (2002–2007) in eastern Kentucky, and leaf traits of red (Erythrobalanus spp.) and white oaks (Leucobalanus spp.) were compared with competitors red maple (Acer rubrum L.) and sassafras (Sassafras albidum (Nutt.) Nees). Burned seedlings had higher total leaf area (TLA) because of two to three times higher TLA of sassafras. Leaf mass per area (LMA) and leaf N content per area (Narea) increased postfire but were independent of seedling identity. Canopy openness during 2006, which was lower on unburned sites (4%–8%) compared with those burned 1× (4%–16%) and 3× (7%–33%), was positively correlated with sassafras TLA, oak and sassafras Narea, and LMA of all seedling groups the subsequent year. In 2007, TLA, LMA, and Narea were positively correlated with basal diameter of all groups but most significantly for sassafras and red maple. These findings indicate that low-intensity, early growing season prescribed fire can alter seedling leaf characteristics, but not in a manner that enhances oak seedling leaf traits relative to their competitors red maple and sassafras. Les aménagistes utilisent de plus en plus le brûlage dirigé dans les forêts de chênes pour éliminer les espèces sensibles au feu, augmenter la lumière en sous-étage et améliorer la régénération du chêne (Quercus spp.). Pour mieux comprendre la réaction des semis ligneux au brûlage, des brûlages uniques et répétés (3×) ont été effectués sur une période de 6 ans (2002–2007) dans l’est du Kentucky et les caractères des feuilles des chênes rouges (Erythrobalanus spp.) et blancs (Leucobalanus spp.) ont été comparés à ceux des espèces compétitrices : l’érable rouge (Acer rubrum L.) et le sassafras officinal (Sassafras albidum (Nutt.) Nees). Les semis brûlés avaient une surface foliaire totale (SFT) plus élevée à cause de la SFT du sassafras qui est 2–3× plus élevée. La masse foliaire spécifique (MFS) et la teneur en N foliaire par unité de surface (Nsurf.) ont augmenté après le passage du feu peu importe l’espèce de semis. L’ouverture de la canopée en 2006, qui était plus faible dans les stations non brûlées (4 % – 8 %), comparativement à celle des stations brûlées 1× (4 % – 16 %) et 3× (7 % – 33 %), était positivement corrélée avec la SFT du sassafras, la teneur en Nsurf. du chêne et du sassafras ainsi qu’avec la MFS de tous les groupes de semis l’année suivante. En 2007, la SFT, la MFS et la teneur en N surf. étaient positivement corrélées avec le diamètre basal de tous les groupes, mais la corrélation était la plus significative dans le cas du sassafras et de l’érable rouge. Ces résultats indiquent qu’un brûlage dirigé de faible intensité effectué au début de la saison de croissance peut modifier les caractéristiques des feuilles, mais pas de façon à améliorer les caractères des feuilles des semis de chêne relativement aux espèces compétitrices, c’est-à-dire l’érable rouge et le sassafras. [ABSTRACT FROM AUTHOR]

The routine micropropagation of Olea maderensis (Lowe) Rivas Mart. & Del Arco requires an adequate basal medium. To find the optimal basal medium, shoots were grown on four different media: olive medium (OM) and three modified OM media enriched with 2, 4, and 10 times the iron (Fe), magnesium (Mg), and manganese (Mn) concentrations of the OM medium, respectively (OMG, OMG4, and OMG10). For the elongation–proliferation stage, media were supplemented with 9.12 µmol·L–1 zeatin. Doubling the Fe, Mg, and Mn concentrations (OMG) provided green and healthy shoots, while in other media leaf chlorosis or necrosis and abscission occurred because of either deficiency (OM) or toxicity of the elements (OMG4 and OMG10). Shoots grown in the OMG medium also had the highest elongation–proliferation rates. Physiological studies were then performed only between OMG- and OM-grown shoots. Chlorophyll a and b contents and fluorescence (Fv, Fm) were higher in OMG-grown shoots. Doubling the concentration of Fe, Mg, and Mn (which are important in photosynthesis) stimulated leaf survival and photosynthesis. OMG-grown leaves had higher Mg, Fe, and Mn levels. Compared with field leaves, in vitro leaves had higher protein contents. Other physiological parameters (membrane integrity, water content, and osmolality) did not differ between the two media. The best rooting rates were obtained for shoots grown in OMG (>85%), and plants were successfully acclimatized. These studies improved the efficiency and quality of micropropagation of O. maderensis, thereby allowing germplasm preservation of this endangered species. La micropropagation courante d’Oleamaderensis (Lowe) Rivas Mart. & Del Arco requiert un milieu basique adéquat. À cette fin, des pousses ont été cultivées sur quatre milieux différents : le milieu d’olivier standard (OM) ou modifié par l’ajout de Fe, de Mg et de Mn, soit 2, 4 et 10 fois la concentration normale de ces nutriments (OMG, OMG4 et OMG10). Au stade de l'élongation et de la prolifération, les milieux ont été enrichis avec 9,12 µmol·L–1 de zéatine. En doublant la concentration de Fe, de Mg et de Mn (OMG), nous avons obtenus des pousses vertes et saines, alors que les autres milieux ont provoqué des ch1oroses ou des nécroses et causé l’abscission des feuilles, probablement à cause d'une déficience (OM) ou d’une toxicité (OMG4 et OMG10). Les pousses cultivées sur le milieu OMG avaient également les taux d'élongation et de prolifération les plus élevés. Des études physiologiques ont ensuite été effectuées en comparant seu1ement les pousses cultivées sur les milieux OMG et OM. Le contenu en ch1orophylle a et b et la fluorescence (Fv, Fm) étaient plus élevés dans les pousses cultivées sur le milieu OMG. Le fait de doubler les concentrations de Fe, de Mg et de Mn, des éléments importants dans la photosynthèse, a favorisé la survie des feuilles et la photosynthèse. La teneur en Mg, Fe et Mn des feuilles était plus élevée sur le milieu OMG. La teneur en protéines des feuilles était plus élevée in vitro qu’au champ. D'autres paramètres physiologiques (p. ex., l'intégrité des membranes, la teneur en eau et la pression osmotique) étaient semblables dans les milieux OM et OMG. Les meilleurs taux d’enracinement (>85%) ont été obtenus sur le milieu OMG et les plants ont été acclimatés avec succès. En améliorant l'efficacité et la qualité de la micropropagation d’O. maderensis, ces travaux contribuent à la conservation du patrimoine génétique de cette espèce en voie de disparition. [ABSTRACT FROM AUTHOR]

The exotic vines Vincetoxicum rossicum (Kleopow) Barbar. and Vincetoxicum nigrum (L.) Moench have become increasingly invasive in low- and high-light habitats in North America, and a biological control program is being developed. These plants experience little damage in North America, so it is unclear how they might respond to introduced herbivores. I conducted an artificial defoliation study on seedlings and mature plants of V. rossicum and V. nigrum grown under different light environments. Under high light, V. nigrum produced more seed and allocated more resources to aboveground tissue (root:shoot ratios < 1), whereas V. rossicum allocated more resources to roots with root:shoot ratios of 1.9 for mature plants and > 3 for seedlings. These differences disappeared with shading. Increasing frequencies of 100% defoliation caused greater reductions in biomass and seed production for both species and plant stages. Shading further reduced biomass and no seed was produced. Defoliation of shaded, but not unshaded, plants caused high mortality. Additional cutting of stem tips increased branching only. Defoliation may be effective against Vincetoxicum plants growing in low-light environments such as forest understories, but appears to be of more limited value in high-light environments unless repeated defoliation occurs. [ABSTRACT FROM AUTHOR]

Agave tequilana Weber var. azul is the raw material used in the production of tequila. This species has a life cycle of approximately 6–8 years; however, owing to the practice of removing the inflorescence to conserve accumulated sugar reserves, the main form of reproduction is asexual. Little attention has, therefore, been paid to the process of flowering and the factors leading to low levels of germination and seedling viability have not been investigated in detail. The objective of this study was to document gametophyte development, seed production, and germination in A. tequilana under different pollination treatments and in an interspecies cross with Agave americana L. Seed production and germination efficiency was low for both A. tequilana and A. americana under the different pollination treatments, although interspecies crosses did produce some viable seeds. Development of the male gametophyte in both species is of the successive type, producing pollen grains with dicolpate morphology. Female gametophyte development is of the Polygonum monosporic type. The results obtained suggest that genetic incompatibility, inbreeding effects, factors affecting pollen development and germination, or errors in female gametophyte development may contribute to the low fertility observed for A. tequilana and A. americana. [ABSTRACT FROM AUTHOR]

Tunisia has vast land tracts that are marginal, arid, semiarid, or desert (about three quarters of the surface of the country). Reforestation of these regions is one of the methods being used to rehabilitate degraded areas. Casuarina glauca Sieber, a fast-growing tree species that is widely used outside of its native range, was tested in the present study with respect to its degree of acclimatization and hardening in response to drought. Three water regimes, simulating the conditions of the reforestation sites, were applied to C. glauca seedlings. These regimes included a control treatment (T : predawn water potential Ψb = –0.2 MPa), a moderate stress treatment (M : Ψb = –0.5 MPa), and a severe stress treatment (S : Ψb = –1.0 MPa). Water relations parameters, estimated by pressure–volume curves through a repeat pressurization method, as well as accumulated dry mass were measured at the beginning of the experiment and 2, 4, and 6 months following treatment imposition. The total dry mass of M and S plants was significantly affected by the treatments. However, water stress favoured dry mass allocation to roots and decreased the shoot turgid mass / dry mass ratio (TM/DM). The evolution of water relations parameters under M or S regimes revealed an adaptive capacity of C. glauca seedlings, as expressed by a significant decrease of the osmotic potentials at full turgor (Ψπ100) and at the turgor loss point (Ψπ0), an osmotic adjustment in water-stressed plants reaching 0.31 and 0.56 MPa, and a significant increase in εmax reaching 26 % and 68 % of that of the control plants, respectively, at the end of the drought period. A reduction in shoot TM/DM combined with increases in εmax during water stress suggests the presence of a cell wall adjustment. These effects were more pronounced under the severe stress. Our results suggest that preconditioning seedlings to drought under nursery conditions by applying a moderate or severe stress, depending on the conditions of the planting site, for 4 months prior to outplanting, possibly will allow the seedlings to adapt morphologically and physiologically and improve their chance of survival in arid and semiarid zones. [ABSTRACT FROM AUTHOR]

Bryophytes are a dominant and functionally important component of the forest floor vegetation in boreal forests, yet little is known about the fungal diversity associated with these abundant plants. Using molecular identification, we document an ecologically and phylogenetically diverse array of fungi associated with the living parts of three widespread and abundant boreal forest bryophytes, i.e., Hylocomium splendens (Hedw.) Schimp. in B.S.G., Pleurozium schreberi (Brid.) Mitt., and Polytrichum commune Hedw. From 376 cloned ITS sequences, 158 operational taxonomic units (OTUs), roughly corresponding to the number of species, were defined based on sequence similarity searches (Fasta) and phylogenetic analyses. A main portion (62.8%) of the OTUs belonged to Ascomycota, 32.0% to Basidiomycota, 3.9% to Chytridiomycota, and 1.3% to Glomeromycota. The most common orders were Helotiales (18.6%), Agaricales (11.5%), Chaetothyriales (9.6%), and Tremellales (9.0%). Frequently detected OTUs of potentially high ecologic importance included two with high sequence similarity (>99%) to the agaric Entoloma conferendum (Britzelm.) Noordel and the endophyte Lophodermium piceae (Fckl.) Hoehn., and various OTUs with affinity to the Helotian genus Hyphodiscus. Several ectomycorrhiza-forming basidiomycetes were also detected. Most OTUs (77.2%) were only detected once and a very small overlap in composition of OTUs was observed among the three bryophytes, indicating the occurrence of an immense fungal diversity associated with boreal forest bryophytes that deserves further study. [ABSTRACT FROM AUTHOR]

I quantified the occurrence of all vascular plant species inhabiting 43 Thuja plicata Donn ex D. Don trees in a temperate rainforest in British Columbia, Canada, to test whether (i) epiphyte species richness increased with tree diameter, and (ii) epiphyte distributions showed evidence for nestedness, checkerboard distributions, or compartmentalization. Nine vascular plant species were observed growing epiphytically. One species (Polypodium glycyrrhiza Eat.) is an obligate epiphyte, while the remainder typically occurred on the forest floor. Smaller host trees (<0.5 m in diameter) lacked vascular epiphytes, and species richness increased with host diameter. No evidence for nested or checkerboarded distributions was observed. However, epiphyte distributions were compartmentalized, owing to five similar shrub species that tended to co-occur jointly, generating sharp turnover in species composition between host trees with and without shrubs. The lack of co-occurrence patterns indicative of interspecific interactions among epiphytes indicates that the epiphyte meta-community is structured stochastically from species that normally grow terrestrially. [ABSTRACT FROM AUTHOR]

Plant surfaces are a favourable niche for bacterial establishment, and hypothetically, plant species differ in their capacity to harbour epiphytic bacterial communities. This study was conducted to evaluate and describe the structural relationship of a bacterial community at the phyllosphere level with different plant species in a tropical ecosystem. Leaf blades of 47 plant species distributed in 27 botanical families were collected on a typical small Brazilian farm and prepared for observation under light and scanning electron microscopy. Naturally occurring bacteria were the most abundant settlers of the phylloplane, followed by fungal spore or hyphae. All plant species studied were colonized by phylloepiphytic bacteria, which were observed as solitary cells, microcolonies, and biofilms. However, independent of the family, the plant species differed in the pattern of phyllosphere colonization, as reflected in bacteria frequency and presence or absence of anatomical features that would favour the association. The phylloepiphytic bacteria were preferentially established on the following sites: epidermal cell wall junctions, glandular and nonglandular trichomes, veins, stomata, and epidermal cell wall surface. Profuse bacteria and fungi colonization was observed, at a level that was at least comparable with temperate regions. Interestingly, fungi seemed to alter the bacteria colonization pattern, most probably by microenvironmental modifications. The trichome type and density as well as the presence of epicuticular wax on the leaf blade surface seemed to be the most determinant anatomical features for the pattern of phyllosphere colonization. The presence of trichomes has a favourable, and epicuticular wax an unfavourable influence on the plant-bacteria interaction. [ABSTRACT FROM AUTHOR]

Plant architecture is determined by cell division and growth, thus simulation models describing these processes are ideal for determining how local development produces the overall plant form. Because fern gametophytes are structurally simple, they are ideal for investigating the effects of cellular growth and division on plant form. In this work we examine the gametophytic development of Schizaea pusilla Pursh., a small, bog-adapted fern whose gametophyte forms as a mass of single-celled filaments. Using light and scanning electron microscopy we made detailed observations of gametophyte development to generate data for a simulation mechanical model of S. pusilla gametophyte development. To examine how plant architecture is an emergent property of cell division, we constructed a simulation model expressed using the formalism of L-systems. While developing a model of growth in this fern we discovered a previously undescribed structure that contributes to the architecture of this plant, which we term knots. We document the development of knots and demonstrate how they contribute to the overall plant architecture. [ABSTRACT FROM AUTHOR]

I present the results of a molecular investigation into taxonomically unresolved issues of the California red fir – noble fir species complex. Samples were collected throughout the range of California red fir (Abies magnifica A. Murray), from the southern Sierra Nevada to the region in northern California and southern Oregon where morphological variation has suggested it hybridizes with noble fir (Abies procera Rehder). Two rbcL sequences were found within A. magnifica and showed perfect linkage with variation at the chloroplast trnD locus. Only populations in the region of hypothesized hybridization were polymorphic for rbcL. One haplotype is unique to A. magnifica in the southern part of its range, and the other is identical to that found in A. procera to the north, supporting a broad zone of hybridization. There was no evidence for a cryptic geographic barrier between the two species. A single A. procera tree from southwestern Washington also had the A. magnifica haplotype, suggesting that introgression from A. magnifica may be widespread. The type locality of Abies magnifica var. shastensis Lemmon was polymorphic, whereas the disjuct southern A. magnifica var. shastensis was monomorphic for rbcL. I also present corrections, based on replication, to two rbcL sequences for A. magnifica previously deposited in GenBank. [ABSTRACT FROM AUTHOR]

The establishment of plantations is the most common method of opencast reclamation, but few studies have addressed the influence of planted trees on the recovery of biodiversity in new forest sites. The goal of this study was to determine whether the formation of herbaceous vegetation was dependent on the tree species planted on the spoil of a reclaimed oil shale opencast in northeastern Estonia. From 2002 to 2005, the vegetation in eight different site types (distinguished according to the age and composition of tree layer) was surveyed. The results confirmed that the development of herbaceous vegetation was controlled by the dominant species of tree layer. The highest number of herbaceous species was recorded in naturally developed mixed stands. As compared with other site types, the herb layers of the pioneer stage (the vegetation in recently reclaimed sites) and alder stands were the most different. In the terms of the competitive, stress-tolerant, and ruderal strategy types, alder (Alnus spp.) stands tended to enhance the growth of competitors, whereas stress-tolerant species were more abundant in pine stands. Herbaceous vegetation remained sparse in coniferous stands, whereas broad-leaved trees tended to improve the performance of herbaceous species. Our results concur with the suggestions that planting with different tree species is one prerequisite for the development of diverse herb layer. [ABSTRACT FROM AUTHOR]

Black-fruited hawthorns in North America comprise two taxonomic groups within the genus Crataegus, section Brevispinae and section Douglasianae. The first of these has recently been shown to be monospecific, consisting of the blueberry haw, Crataegus brachyacantha Sarg. & Engelm., of Louisiana and Texas. Crataegus section Douglasianae, however, comprises several taxa in a single clade that is not closely related to section Brevispinae, and that is now one of the best-studied groups of hawthorns at least in North America. Most taxa in the group are found in, or west of, the Rocky Mountains. They include diploids, triploids, and tetraploids that can be ascribed to four or more species that differ in distribution and ecology, thorn morphology, leaf shape, and floral architecture. Diploids are self-incompatible, whereas polyploidy is associated with pseudogamous, gametophytic apomixis and self compatibility. Molecular data suggest that polyploids have arisen repeatedly, both within and from crosses between ploidy levels. We suggest that Crataegus section Douglasianae represents at least two agamic complexes that may serve as models for understanding the biology of, the relationships within, and the appropriate taxonomic treatment of other such groups that may make up much of the rest of the genus. [ABSTRACT FROM AUTHOR]

Erigeron trifidus Hook. (Asteraceae) is a rare species in Alberta thought to have originated via hybridization between Erigeron compositus Pursh and Erigeron lanatus Hook., and is disjunct in three alpine regions of Alberta. An analysis of uni- and bi-parentally inherited molecular markers from E. trifidus and its putative parents yielded data that support the hybridization hypothesis for some of the populations. In most cases, cpDNA haplotypes in E. trifidus were the same as in E. lanatus, suggesting that E. lanatus is the maternal parent. Sequencing and cloning the nuclear ETS region revealed multiple repeat types in most individuals. Erigeron trifidus contained only the repeat types also present in the putative parents. In addition, E. trifidus displayed the highest percentage of intra-individual repeat type polymorphism, consistent with a hybrid origin. All northern populations of E. trifidus exhibited a particular pattern of repeat type variation that was absent in central and southern populations. Since E. lanatus is absent from Ram Mountain (in central Alberta), it is likely that populations from this locality, previously identified as E. trifidus, are instead a different agamospermous variant of E. compositus. In southern Alberta (Waterton Lakes), populations of E. trifidus are thought to be the product of local hybridization, and are therefore of different origin from the northern populations. The identity of the putative parents in the southern region remains uncertain. [ABSTRACT FROM AUTHOR]

We used a combination of morphology, amplified fragment length polymorphisms (AFLP), and restriction-site data from 252 individuals from 51 populations to investigate species limits and hybridization in the Carex complanata complex. Principal coordinate analysis of the morphological data shows clear separation of entities corresponding to Carex bushii Mackenzie and Carex caroliniana Schwein. However, only leaf indumentum reliably distinguished between Carex hirsutella Mackenzie and Carex complanata Torr. & Hook. Despite this very subtle difference, AFLP data reveal very clear genetic separation of these two taxa. Contrary to the assertions of previous authors, we found no evidence of introgression among C. complanata, C. caroliniana, and C. bushii. Relatively high genetic variation within C. hirsutella may be an indication of gene-flow between this species and one or more other species, but further work is necessary to clarify this issue. We document six previously undescribed sterile or nearly sterile hybrids involving the species in this complex. [ABSTRACT FROM AUTHOR]

Sugar maple (Acer saccharum Marsh.) decline has occurred throughout its range over the past 50 years, although decline symptoms are minimal where nutritional thresholds of Ca, Mg, and Mn are met. Here, we show that availability of these elements also controls vascular plant species composition in northern hardwood stands and we identify indicator species of these nutrient thresholds. Presence and abundance of vascular plant species and data on 35 environmental variables were collected from 86 stands in New Hampshire and Vermont (NHVT) and Pennsylvania and New York (PANY). Nonmetric multidimensional scaling ordination was used to determine which variables affected presence and abundance of species; both measures gave similar results. A base cation – acid cation nutrient gradient on axis one accounted for 71.9% (NHVT) and 63.0% (PANY) of the variation in the nonmetric multidimensional scaling ordination. Measures of Ca, Mg, and pH formed the base end and Al, Mn, K, soil acidity, and organic matter the acid end in both subregions. In both subregions, sugar maple foliar Mg and Ca had the strongest association with the base end of axis 1; exchangeable Al in NHVT and foliar Mn in PANY were strongly associated with the acid end. McNemar’s exact test and indicator species analysis were used to determine which species were present in stands that met the nutritional thresholds for Ca, Mg, and Mn foliar chemistry. McNemar’s exact test identified 16 species in NHVT and PANY, 16 additional species in NHVT only, and 12 additional species in PANY only. Indicator species analysis identified a subset of these species with the highest frequency of occurrence. Indicator species could provide land managers with a diagnostic tool for determining where on the landscape sugar maple is “at risk” or likely to remain healthy in the face of stresses. Le dépérissement de l’érable à sucre (Acersaccharum Marshall) est survenu partout dans l’aire de répartition de cette essence au cours des 50 dernières années mais il y a très peu de symptômes de dépérissement aux endroits où les seuils nutritionnels pour Ca, Mg et Mn sont atteints. Nous montrons ici que la disponibilité de ces éléments régit également la composition en espèces de plantes vasculaires dans les peuplements de feuillus nordiques et nous identifions des espèces indicatrices des seuils pour ces nutriments. La présence et l’abondance des espèces de plantes vasculaires ainsi que 35 variables environnementales ont été mesurées dans 86 peuplements des tats du New Hampshire et du Vermont (NHVT) ainsi que ceux de la Pennsylvanie et de New York (PANY). L’ordination de mesures multidimensionnelles non paramétriques a été utilisée pour déterminer quelles variables influencent la présence et l’abondance des espèces; les deux mesures ont produit des résultats similaires. Un gradient de nutriments allant des cations basiques à acides sur l’axe un expliquait 71,9% (NHVT) et 63% (PANY) de la variation dans l’ordination. Les mesures de Ca, Mg et de pH formaient la partie basique et Al, Mn, K, l’acidité du sol et la matière organique formaient la partie acide dans les deux sous-régions. Dans les deux sous-régions, le Mg et le Ca foliaire de l’érable à sucre était le plus étroitement associé à la portion basique de l’axe un; l’Al échangeable dans la sous-région NHVT et le Mn foliaire dans la sous-région PANY étaient fortement associés à la portion acide. Le test de McNemar et l’analyse des espèces indicatrices ont été utilisés pour déterminer quelles espèces étaient présentes dans les peuplements où les seuils nutritionnels pour Ca, Mg et Mn étaient atteints dans les feuilles. Le test de McNemar a identifié 16 espèces dans les deux sous-régions, 16 autres dans la sous-région NHVT et seulement 12 autres dans la sous-région PANY. L’analyse des espèces indicatrices a identifié un sous-ensemble des ces espèces dont la fréquence était la plus élevée. Les espèces indicatrices pourraient fournir aux aménagistes du territoire un outil de diagnostique pour déterminer à quel endroit le paysage d’érable à sucre est à risque et où il restera sain face aux stress. Note : l.7 de l’abstract, saccharum Marshall au lieu desaccharum Marsh. [ABSTRACT FROM AUTHOR]

We measured interaction of photosynthetically active radiation (PAR) at a staghorn sumac (Rhus typhina L.) canopy near Peterborough, Ontario, during summer 2006. Measurements included above-canopy and below-canopy incoming and reflected PAR fluxes and leaf area index (LAI). The ratio of down-welling PAR below the canopy to the flux incident at the top of the canopy () and proportion of incident PAR absorbed by the canopy (fPAR), were calculated. While the canopy was leafless, the sumac stems absorb 10%–20% of incident PAR. LAI increased rapidly during the month of June, and correspondingly decreased rapidly while fPAR increased rapidly. Mean values of and fPAR at maximum LAI were 0.38±0.09 (SD) and 0.60 ±0.04, respectively. Neither variable showed a relationship with solar zenith angle. We present a simple idealized model of PAR interaction with sumac. Although only one stand was studied, we hypothesize that these results may be more widely applicable to other mature sumac stands. [ABSTRACT FROM AUTHOR]

We sampled dominant and codominant regeneration on 70 clearcuts, 21–35 years old, on the Hoosier National Forest in southern Indiana, USA, to evaluate influence of site variables on the competitive success of natural oak (Quercus L.) over time. Collected data was compared with data collected on these same sites 20 years prior. Regression tree analysis indicated aspect, natural region, and oak abundance in preharvest stands had the greatest influence on competitive success (relative density, RD) of oak species in the latter sampling, which was then examined across sites as defined by these three variables. Oak RD increased across all mid- and some lower-slope positions, sites on which oaks are expected to be replaced by faster growing species. Drought events between sampling periods apparently contributed to a decline in RD and vigor of yellow-poplar (Liriodendron tulipifera L.), a major competitor for growing space. Stump sprouts contributed 45% of dominant oak stems. Mean oak diameters were not significantly lower than those of other species groups, with the exception of yellow-poplar in younger stands and at mid-slope positions. Oak species drought tolerance, relative to more mesic species found on these sites, and the large proportion of oak stump sprouts likely contributed to oak competitive success. [ABSTRACT FROM AUTHOR]

We tested effects of shortened day length during nursery culture on Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) seedling development at dormancy release. Seedlings from a 42°N source were grown either under ambient photoperiods (long-day (LD)) or with a 28 day period of 9 h light : 15 h dark photoperiods (short-day (SD)). Seedlings were periodically removed from freezer storage from January to May. Sensitivity of plant tissues to cold temperatures was investigated via electrolyte leakage at nine test temperatures ranging from 2 to –40 °C. New root growth was assessed with rhizosphere temperatures of 10, 15, 20, and 25 °C. From 2 to –13 °C, there was no difference between treatments in cold hardiness. However, at or below –18 °C, LD seedlings exhibited higher indices of damage than SD seedlings. The LT50 (temperature at which 50% cell electrolyte leakage occurred) was consistently lower for SD than LD seedlings. Rhizosphere temperature differentially influenced new root proliferation: LD seedlings had greater new root production than SD seedlings at 20 °C, whereas the opposite response was detected at 10 °C. Our results confirm photoperiod sensitivity of Douglas-fir sources from relatively low (i.e., <45°N) latitudes. Increased spring cold hardiness and greater rooting at lower rhizosphere temperatures may improve field performance potential of SD-treated seedlings. [ABSTRACT FROM AUTHOR]

Trends in stem quality characteristics of loblolly pine trees were investigated by using data from unthinned control plots established in plantations across 12 southern states in the United States and measured at 3 year intervals. At each measurement, the stem quality was classified into (i) single stem or forked, (ii) normal top or broken top, (iii) straight or sweep (bole sweep, butt sweep, short crook), and (iv) no disease or disease. Data through the first 15 years of observation showed that, on average, 4% of the trees were forked, 5% had broken tops, 41% had sweep, and 12% had disease or insect damage; 48% exhibited single stem, normal top, straight, and no disease or insect damage. Recovery rates out of forked, broken top, sweep, and disease classes were 37%, 83%, 30%, and 11%, respectively, over the 15 years. Multicategorical logit models were developed to predict stem quality characteristics from stand-and tree-level variables. Forked trees were related with tree diameter; broken tops were related with stand density, DBH, and relative height; sweep was related with stand age. Significant predictor variables for the incidence of disease or insect attack were not found. The occurrence of undamaged and disease-free trees can be predicted from DBH and relative height. [ABSTRACT FROM AUTHOR]

In light of the risk of litigation following damage related to tree failure in urban and suburban settings, more empirical data related to tree risk assessment are needed. We measured drag and drag-induced bending moment (M) and calculated drag coefficient (CD) and trunk stress (σ) for three deciduous trees at wind speeds up to 22.4 m/s. We measured the modulus of rupture (MOR) of wood samples from trunks and calculated the factor of safety (SF = MOR / σ) for each tree. We also investigated which tree morphometric variables best predicted drag and M and whether simple two- and three-dimensional shapes accurately represented actual tree crowns. Drag, CD, M, σ, and SF differed among species in accordance with physical parameters. More massive trees experienced greater drag and M, but σ was greater for trees with smaller trunk diameters. Tree mass reliably predicted drag and M; crown dimensions, including crown area, were less reliable predictors. Crown reconfiguration varied only slightly among species, and CD values were similar to previously reported values for trees of similar size. Our study has important applications for practitioners who manage tree risk, particularly the critical wind speeds and percentage of trunk cross-sectional area that could be decayed before trunk failure. [ABSTRACT FROM AUTHOR]

We investigated soil microbial community structure by phospholipid fatty acid (PLFA) analysis in a mature boreal spruce forest landscape in southern Norway, with low diversity of vascular plants. We investigated the spatial variation in PLFAs and the importance of environmental variables in 10 plots (each 13 samples) in a study area of 1 km × 1 km. The scales investigated were 15 cm to 10 m within study plots and 100 m to 1 km between study plots. Soil microbial biomass varied 10-fold and we found a large variation in microbial community structure, even at distances of 15 cm. Samples aggregated into plots when PLFAs were subjected to a principal components analysis. Plot identity explained 36.3% of the variation in the PLFAs and geostatistical analysis showed that the microbial community structure displayed spatial dependence at within-plot distances. Environmental variables differed significantly between all plots but explained only minor parts of the variation in the overall PLFA pattern. The vegetation variables were, however, the best at explaining the PLFA pattern, and up to 60% of within-plot variation in individual plots, respectively, could be explained by vegetation variables, pH, and soil depth. [ABSTRACT FROM AUTHOR]

The traditional medicinal uses of plants by the Inuit of Nunavut, Canada were analysed using quantitative ethnobotanical methodology. Traditional knowledge was collected during interviews with volunteer Inuit informants and from historical interview transcripts. A total of 13 different species were mentioned, which included 1 moss, 1 algae, 1 fungus, and 10 vascular plant species. An informant consensus index value, Fic > 0.7, for many use categories revealed a high level of informant agreement, consistent with a well-preserved oral tradition and low flora biodiversity. The documentation of this information is a useful tool for the preservation of Inuit culture, as well as for the integration of Inuit traditional medicine with Western medical practices in Arctic communities (Inuit Qaujimajatuqangit, IQ). [ABSTRACT FROM AUTHOR]

This paper presents the results of an experiment replicating traditional Interior Salish pit-cooking methods to process balsamroot (Balsamorhiza sagittata (Pursh) Nutt.), a former food staple that contains the complex carbohydrate inulin. Analysis of fresh and cooked balsamroot samples reveals that with sufficient heat, moisture, and the release of volatile organic acids, inulin is hydrolyzed during pit cooking. This process converts complex carbohydrates into simple ones, resulting in an increase of 250% in the energy provided by simple sugars. When the average energy contributions of protein, simple and complex carbohydrates are tallied, the net result is an energy gain of approximately 65% between fresh and pit-cooked balsamroot. This research demonstrates the effectiveness of ancient pit-cooking practices in transforming unpalatable and inedible root resources into sweet-tasting, highly digestible sources of carbohydrate energy and supports my assertion that this processing technology was a key component of the wild plant food production systems of Interior Salish Peoples. [ABSTRACT FROM AUTHOR]

Knowledge and practices of indigenous peoples relating to local plants used for food, medicine, materials, and other purposes are threatened in many parts of the world. The reasons for declining knowledge and use of traditional resources are complex and multifaceted. We review a series of case examples of culturally valued food plants in British Columbia and identify a suite of interacting social and environmental factors that have resulted in decreased use of and dwindling cultural knowledge about these plants over the past 150 years. Reasons for this loss include compounding influences of changing knowledge systems owing to religious conversion and residential schools, loss of indigenous languages, loss of time and opportunity for traditional practices owing to participation in the wage economy, increasing urbanization of indigenous populations, loss of access to traditional resources, restriction of management practices for sustaining these resources, and most recently, forces of globalization and industrialization. Efforts to renew and restore traditional practices and relationships with plants and environments must recognize the cumulative effects of these factors and find ways to retain and reinforce the knowledge and practices still held by individuals and communities, to reverse some of the negative influences on cultural retention, and to develop new, relevant, and effective ways to revitalize languages, cultures, and ethnobotanical knowledge within contemporary contexts. [ABSTRACT FROM AUTHOR]

To examine the function of morphologically hermaphroditic, but functionally sterile, florets in female inflorescences of Petasites japonicus (Sieb. & Zucc.) Maxim., we conducted experiments in which all those florets were removed from female inflorescences. We hypothesize that those florets enhance female reproductive success by deceit, because they resemble the morphologically hermaphroditic, but functionally male florets, in male inflorescences. We found that the mean number of pollinator visits per inflorescence did not differ between the intact inflorescences and inflorescences in which such hermaphrodite florets had been removed. However, the mean duration of stay per visit to an inflorescence tended to be shorter in those with removed florets than in the intact inflorescences. The achene / female floret ratio was smaller in the inflorescences with removed florets than in the intact ones. We hence concluded that the hermaphrodite florets in female inflorescences enhance female reproductive success through prolonged duration of pollinator stay. [ABSTRACT FROM AUTHOR]