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Graphical abstract Highlights • The effect of abiotic and biotic elicitors on R. tomentosum essential oil was tested. • The aphid extract was used as a new elicitor of insect origin in plant biotechnology. • The elicitors most suitable for improving the production of terpenes were selected. • Addition of nickel salts, the aphid extract and P. carotovorum gave promising results. • The RITA® bioreactor was suitable for elicitation studies in plant in vitro cultures. Abstract Rhododendron tomentosum Harmaja, previously Ledum palustre L., is a fragrant plant growing in swampy areas, which is characterized by well-known repellent properties and the anti-arthritic potential. In the present study, R. tomentosum microshoots cultivated in RITA® bioreactor, providing the alternative, environment-independent source of the valuable essential oil, were treated for 7 days with copper and nickel salts, methyl jasmonate, chitosan, ergosterol, lysates of: Candida albicans , Escherichia coli , Enterobacter sakazaki, Pectobacterium carotovorum and Dickeya dadantii , to stimulate the production of secondary metabolites. Moreover, for the first time, the aphid ethanol extract was tested as an elicitor of insect origin. Suspensions of all pathogens added to in vitro culture reduced significantly the biomass growth parameters. The application of the aphid extract and lysate of P. carotovorum increased the volatile fraction content by 14%, while Ni2+ and ergosterol by 8%. The influence of the studied elicitors on the chemical composition of R. tomentosum essential oils was presented and discussed thoroughly, taking into account a percentage of 22 main terpenoid compounds, determined by GC/MS (i.a. p -cymene, geranyl acetate, δ -cadinene, shyobunone, methyl everninate, ledene oxide (II) and alloaromadendrene). The biosynthesis of monoterpenes was primarily proven to be affected by the elicitation. The conducted experiments suggest that R. tomentosum is rather resistant to elicitation strategies, both abiotic and biotic as well as methyl jasmonate. [ABSTRACT FROM AUTHOR]

Hyperuricemia is a common metabolic disorder and several homeopathic ultra-high dilutions are being used in the treatment of hyperuricemia and its related diseases. Conventional treatment for the hyperuricemia is allopurinol but it gives many side effects like allergic reactions, gestrohepatic ailment, hepatic and renal complaints. It is the need of the hour to introduce an alternative system of medicine with minimal side effects. The study aimed to find hypouricemic effects of Ledum palustre 30c and 1M in potassium oxonate induced hyperuricemia rat model. The study comprised of 11 groups of rats (E = 33). All the groups except normal control were treated with potassium oxonate. Normal control group received distilled water, hyperurecemic control group succussed alcohol mixed in distilled water. Allopurinol, Ledum palustre 30c and 1M were administered for one day, 3 day and 7 days (single dose/day) in different study groups (3×3 = 9 groups). Blood samples were collected by rat tail vein bleeding. Serum uric acid and serum creatinine levels were checked by using standard kits. Student's t-test for independent means was used for statistical analysis of difference between the groups. p = 0.05 (two tailed value) was considered significant. Oral administration of Ledum palustre 30c and 1M decreased serum uric acid levels of hyperurecemic rats in time dependent manner. 3 day and 7 day administration of Ledum palustre 30c and 1M reduced serum uric acid level more significantly as compared to one day administration. However, allopurinol normalized serum uric acid levels in all study groups. The present study indicated marked hypouricemic effects of Ledum palustre 30c and 1M in hyperuricemia induced by potassium oxonate in rats. However, clear conclusion of hypouricemic potential of Ledum palustre required replication of experiment. [ABSTRACT FROM AUTHOR]

Rhododendron tomentosum Harmaja (formerly Ledum palustre L.) is a medicinal peat bog plant native to northern Europe, Asia and North America. This plant has a distinctive aroma thanks to the presence of essential oil, to which it also owes its anti-inflammatory, analgesic, antimicrobial and insecticidal properties. However, in Europe R. tomentosum is classified as an endangered species, mainly due to degradation of peatlands. In the present work, the micropropagation protocol for R. tomentosum was established for the first time, providing both an ex situ conservation tool and a means of continuous production of in vivo and in vitro plant material for further studies. R. tomentosum microshoots were initiated from leaf explants and further multiplied using Schenk-Hildebrandt (SH) medium supplemented with 9.84 μM 2iP and 1.00 μM TDZ. The shoots were elongated on the SH medium supplemented with 24.6 μM 2iP and subsequently rooted using the perlite substrate saturated with half-strength Woody Plant medium supplemented with 1.0% sucrose and 4.92 μM IBA. The regenerated plants were hardened on the phytohormone-free SH medium and acclimatized using 3:1:1 deacidified peat:perlite:gravel substrate. The identity of the mother plant was confirmed at morphological and molecular levels and Random Amplified Polymorphic DNA (RAPD) method was implemented to assess the genetic fidelity of the regenerants. The essential oil content of the maternal plant, in vitro shoots and the regenerants was determined by steam-distillation, and the obtained volatile fractions were analyzed by GC/MS. [ABSTRACT FROM AUTHOR]

ContentOur team has identified Labrador tea [Rhododendron groenlandicumL. (Ericaceae)] as a potential antidiabetic plant from the traditional pharmacopoeia of the Eastern James Bay Cree. In a previousin vivostudy, the plant extract was tested in a high-fat diet (HFD)-induced obese model using C57BL/6 mice and it improved glycaemia, insulinaemia and glucose tolerance. ObjectiveIn the present study, we assessed the plant’s potential renoprotective effects. Materials and methodsRhododendron groenlandicumwas administered at 250 mg/kg/d to mice fed HFD for 8 weeks to induce obesity and mild diabetes. Histological (periodic acid–Schiff (PAS), Masson and Oil Red O staining), immunohistochemical (IHC) and biochemical parameters were assessed to evaluate the renoprotective potential ofR. groenlandicumtreatment for an additional 8 weeks. ResultsMicroalbuminuria and renal fibrosis were developed in HFD-fed mice. Meanwhile, there was a tendency forR. groenlandicumto improve microalbuminuria, with the values of albumin-creatinine ratio (ACR) reducing from 0.69 to 0.53. Renal fibrosis value was originally 4.85 arbitrary units (AU) in HFD-fed mice, dropped to 3.27 AU after receivingR. groenlandicumtreatment.Rhododendron groenlandicumreduced renal steatosis by nearly one-half, whereas the expression of Bcl-2-modifying factor (BMF) diminished from 13.96 AU to 9.43 AU. Discussion and conclusionsTaken altogether, the results suggest thatR. groenlandicumtreatment can improve renal function impaired by HFD. [ABSTRACT FROM AUTHOR]

Few guidelines exist for the effective revegetat'on of peatlands following the removal of in-situ oil and gas infrastructure. We conducted a manipulative field study in northeast Alberta, Canada, on a well pad undergoing removal and revegetation to test different management practices for facilitating vegetation establishment and recovery of a sphagnum-dominated peatland. A randomized block design was used to evaluate the effect of various revegetation practices, including augmenting natural recovery with the use of native transplants, acrotelm transfer from a similar intact donor peatland, and the use of variable surface microtopography. Although overall survival of transplants was similar between areas smoothed and left rough, areas th at were rough had greater species richness under natural recovery, including trees, shrubs, and other perennial herbs. Moreover, survival and growth of woody transplants (Picea mariana-black spruce and Ledum groenlandicum-Labrador tea) were greater when planted with in the top and middle microtopographic positions rather than micro-depressions. Survival of transplanted sedges (Carex spp.) was high at all topographic positions, but benefited the most in g rowth from planting in depressions. Contrary to expectations, no benefits of acrotelm application were found on vegetation recovery during the first tw o seasons, and even reduced the presence of some native vegetation. Although transplants directly contributed to revegetation, the recovering peatland remained highly dissimilar (> 90%) in composition relative to the neighboring peatland after two years. [ABSTRACT FROM AUTHOR]

How can cross-disciplinary speculative narratives give us insights and open new paths of research? Borrowing from a number of disciplines, from Anthropology to Psychology or Art history, I will draw a hypothetical blueprint of processes that possibly led to the creation of the Ainu people's patterns, an indigenous tribe from north Japan. From some particular key points I will narrate a speculative tale giving us possible insights about those specific patterns, as well as about the questions encapsulated in the split representation in the art of Asia and America, questions that were raised by various anthropologists, from Franz Boas to Claude Levi-Strauss. I will demonstrate that those pattern-making habits were inherent to human being as a species until very recently. What kind of unconscious purpose or meaning they could have had and what it could mean in terms of the evolution of consciousness. [ABSTRACT FROM AUTHOR]

Labrador tea is a name for the dried leaves of Rhododendron groenlandicum, R. tomentosum or R. neoglandulosum (family Ericaceae, previously genus Ledum) as well as for the beverage native to North America, which is made from them. The above species are rich in the essential oil, which gives a conifer aroma to the tisane. Labrador tea is a valuable source of ascorbic acid, with tonic, improving digestion and relaxing activity. However, this beverage should not be drunk more than once daily because of the ledol and grayanotoxin toxicity. The common recipe for making Labrador tea is to add one teaspoonful of dried leaves to one cup of boiling water and to brew for 5 min. It is often sweetened or enriched with other flavors. Additionally, Labrador tea dried leaves are used to spice meat, soups, sauces, salads, beer, cakes and other dishes. In agriculture, its insecticidal properties can be useful for controlling pests. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The impact of several environmental factors on the production of phenolic compounds in a North American medicinal plant, Labrador tea ( Rhododendron groenlandicum (Oeder) Kron & Judd), was studied. Leaves were harvested in 2006 and 2010 over a latitudinal gradient in northern Quebec, and known phenolic markers were quantified by HPLC-DAD. The concentration of selected compounds varied geographically where they were higher between the 51st and 53rd parallel of northern Quebec and lower in the peripheral northern and southern region. Major variations were observed in the following marker compounds: (+)-catechin, (-)-epicatechin, quercetin-3-galactoside, and an undetermined quercetin-glycoside. The variation in phenolic compounds was best explained by short-term changes in annual temperature range and long-term estimates of insolation parameters such as solar radiation and photoperiod in the month of June. [ABSTRACT FROM AUTHOR]

Lodgepole pine ( Pinus contorta var. latifolia) stands were sampled in central Yukon, Canada (61.5-64°N latitude), which represented the northernmost 9% of the tree's North American range. Within this area, lodgepole pine occupied only ˜ 2% of the landscape. This study determined: 1) what forest sociations occurred (i.e. structural dominance-types); 2) how plant growth form composition and richness differed from the central portion of the species' geographical range; and 3) if stands were biased towards occurring on more thermally favorable south-facing slopes. Five lodgepole pine sociations were recognized among 100 relevés: Rhododendron groenlandicum (Labrador tea); Cladonia arbuscula (green reindeer lichen); Calamagrostis purpurascens (purple reedgrass); Hylocomium splendens (stairstep moss) and Alnus viridis (green alder, n = 4 relevés). Rhododendron stands were proportionally more common on low gradient sites and had more total plant cover than the other sociations. Cladonia and Calamagrostis stands were typically associated with dry coarse-textured soils and warm dry sites, respectively; whereas the composition of the Hylocomium sociation reflected the detrimental influences of atypically dense forest canopies on understory vascular plants. Only the Calamagrostis sociation was unique to the study region. Species richness among common northern lodgepole pine sociations averaged 16-19 taxa per relevé (p > 0.05). Northern compared to central range (n = 1394) relevés were compositionally different based on little overlap of their datasets in the ordination space. Northern vegetation had less (p < 0.001) total plant (129% vs 184%), deciduous shrub (9% vs 26%), broad-leaved herb (5% vs 25%), and bryophyte (27% vs 54%) cover; had greater macro-lichen cover (13% vs 5%) and lower floristic richness (11 vs 24 taxa) and was less than half as phytosociological diverse. Lodgepole pine stands in the northernmost portion of their range were not biased towards occurring on south-facing slopes, which suggested an ecological potential for range expansion. [ABSTRACT FROM AUTHOR]

Plant resorption of multiple nutrients during leaf senescence has been established but stoichiometric changes among N, P and K during resorption and after fertilization are poorly understood. We anticipated that increased N supply would lead to further P limitation or co-limitation with N or K [i.e. P-(co)limitation], decrease N resorption and increase P and K resorption, while P and K addition would decrease P and K resorption and increase N resorption. Furthermore, Ca would accumulate while Mg would be resorbed during leaf senescence, irrespective of fertilization. We investigated the effect of N, P and K addition on resorption in two evergreen shrubs ( Chamaedaphne calyculata and Rhododendron groenlandicum) in a long-term fertilization experiment at Mer Bleue bog, Ontario, Canada. In general, N addition caused further P-(co)limitation, increased P and K resorption efficiency but did not affect N resorption. P and K addition did not shift the system to N limitation and affect K resorption, but reduced P resorption proficiency. C. calyculata resorbed both Ca and Mg while R. groenlandicum resorbed neither. C. calyculata showed a higher resorption than R. groenlandicum, suggesting it is better adapted to nutrient deficiency than R. groenlandicum. Resorption during leaf senescence decreased N:P, N:K and K:P ratios. The limited response of N and K and the response of P resorption to fertilization reflect the stoichiometric coupling of nutrient cycling, which varies among the two shrub species; changes in species composition may affect nutrient cycling in bogs. [ABSTRACT FROM AUTHOR]

Sustainable management of boreal ecosystems involves the establishment of vigorous tree regeneration after harvest. However, two groups of understory plants influence regeneration success in eastern boreal Canada. Ericaceous shrubs are recognized to rapidly dominate susceptible boreal sites after harvest. Such dominance reduces recruitment and causes stagnant conifer growth, lasting decades on some sites. Additionally, peat accumulation due to Sphagnum growth after harvest forces the roots of regenerating conifers out of the relatively nutrient rich and warm mineral soil into the relatively nutrient poor and cool organic layer, with drastic effects on growth. Shifts from once productive black spruce forests to ericaceous heaths or paludified forests affect forest productivity and biodiversity. Under natural disturbance dynamics, fires severe enough to substantially reduce the organic layer thickness and affect ground cover species are required to establish a productive regeneration layer on such sites. We succinctly review how understory vegetation influences black spruce ecosystem dynamics in eastern boreal Canada, and present a multi-scale research model to understand, limit the loss and restore productive and diverse ecosystems in this region. Our model integrates knowledge of plant-level mechanisms in the development of silvicultural tools to sustain productivity. Fundamental knowledge is integrated at stand, landscape, regional and provincial levels to understand the distribution and dynamics of ericaceous shrubs and paludification processes and to support tactical and strategic forest management. The model can be adapted and applied to other natural resource management problems, in other biomes. [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]

Marsh rosemary (Rhododendron tomentosum L. Stokes) H. Harmaja (formerly Ledum palustre) plants were collected at the flowering stage in marshes near Šulnys Lake (Šalčininkai District, Eastern Lithuania) in 2004. Essential oils were prepared by hydrodistillation and analyzed by GC and GC/MS. The major oil constituents were p-cymene (6.2-20.3%), isoascaridol (16.7-24.1%), palustrol (1.2-31.8%) and ledol (5.2-23.4%); and their percentage changed according to the sampling sites. Despite that the plant material was gathered from the limited area, significant compositional variability was observed in the essential oils. Ninety identified (two of them tentatively) compounds comprised up to 97.9% of the oils. [ABSTRACT FROM AUTHOR]

Harvesting of medicinal plants from wild populations is increasing worldwide, however, studies on sustainable harvesting techniques are lacking. In this exploratory study, we investigated the impact of leaf harvesting on (Oeder) Kron & Judd, a North American temperate shrub, used traditionally as a medicinal plant by the Cree Nation. The species is widely distributed, but Crees are worried that commercial harvesting could threaten local plant populations. Our study was conducted near the Cree Nation of Mistissini (James Bay, Northern Quebec). Three leaf harvest regimes were tested in 2008 and 2009: no harvest, all leaves harvested, and only old leaves harvested; each treatment was performed on 30 plants. The harvesting of all leaves had a negative impact on stem elongation after the first harvest, while leaf production and stem radial growth decreased after the second harvest. Two-thirds of the plants also died following the second regime of harvesting all leaves. The harvesting of old leaves had no significant impact on growth, leaf production, or survival of R. groenlandicum, even after 2 years of harvest. These results lead to the conclusion that sustainable harvest of this species is possible, but further study is required to make definite recommendations. [ABSTRACT FROM AUTHOR]

The article presents the Rhododendrum groenlandicum (Oeder) Kron and Judd, bog Labrador tea, an evergreen shrub from the Ericacae family native to North America. Its other names include bot tea, rusty Labrador tea and Hudson Bay tea and has long been known as Ledum groenlandicym Oeder 1771, non Retzius 1779. Its leaves are described as alternate, simple 2.5 cm long and 0.5-2 cm wide sessile or short-petioled. It cites its responses to herbivory such as mammals, insects and nematodes, diseases such as fungi, viruses and bacteria.

In boreal black spruce (Picea mañana (Mill.) BSP) dominated stands, careful logging around advance regeneration contributes to protect the shrub layer while increasing light availability. Therefore, it may promote expansion of bog Labrador tea (Rhododendron groenlandicum (Oeder) Kron & Judd), which can impair black spruce growth by direct competition for nutrients and by alteration of soil biochemical conditions. Such harvesting approaches may not be suited for irregular, uneven-aged black spruce stands in the context of ecosystem-based management. Our objectives were to evaluate the effects of different intensities of partial harvest on critical resource availability and to compare the physiological and morphological responses of black spruce and Rhododendron to different intensities of partial harvest treatments. Two years after harvest, photosynthesis rate of black spruce was unchanged and was lower than that of Rhododendron, which was 63% higher after harvest. Nitrogen and water use efficiency were, respectively, 171% and 42% higher in Rhododendron than in black spruce after logging. Following harvest, black spruce physiology appeared to be regulated by the atmospheric humidity deficit, but for Rhododendron, physiology was regulated by light availability. The high plasticity of Rhododendron leaf traits could be indicative of the future advantage of this species in these stands following canopy removal associated with harvest. [ABSTRACT FROM AUTHOR]

Abstract: Vegetative layering of black spruce (Picea mariana [Mill.] B.S.P.) is the principal mode of regeneration for over mature, uneven-aged stands subject to long fire cycles (>300 years) in northeastern Québec, Canada. However, growth response of black spruce layers following disturbance by fire or harvest can be slow, due to a lag of morphological acclimation and potential nutrient limitation. This phenomenon can be accentuated if black spruce is associated with ericaceous shrubs such as Kalmia angustifolia and Rhododendron groenlandicum, which are known to interfere with conifer growth through direct and indirect competition. Such interactions can result in productive stands being converted to unproductive heathlands. It is not known whether these effects of ericaceous shrubs on black spruce are accentuated on low fertility sites, or if the impacts are independent of inherent site fertility. The objectives of this study were to evaluate the effects of ericaceous shrubs on both resource availability and on functional traits of black spruce advance regeneration across a gradient of site fertility (as defined by a site classification system). We monitored black spruce advanced regeneration physiology and soil nutrient availability over two growing seasons on a gradient of ecological site types in northeastern Québec (Canada). The eradication of competing vegetation favored higher soil NH4-N and K availability, with increases of 67% and 28% compared to control conditions, respectively. Black spruce photosynthesis rate (A) and foliar K content were higher in plots where vegetation was eradicated, compared to the control plots, but did not vary among ecological site types. Photosynthesis did not appear to be limited by nitrogen or water relations, but was possibly limited by a deficit of foliar K+, probably resulting from reduced availability following sequestration by the ericaceous root systems. The absence of interaction between inherent site fertility and the eradication of ericaceous shrubs suggests that vegetation management of ericaceous shrubs must be planned independently from the ecological site type. [Copyright &y& Elsevier]

Wild Ledum palustre L. plants were collected near Juodupė (Rokiškis region) and Šilėnai (Vilnius region) villages. Essential oils from young and aged shoots, obtained by hydrodistillation, were analysed using GC and GC/MS. The major constituents were palustrol (31.4-42.8%), ledol (23.6-30.8%), cyclocolorenones (4.0-9.3%), myrcene (1.2-8.6%) and limonene (11.0%). The essential oil from plants growing near Šilėnai village differed from that of L. palustre near Juodupė by a higher content of compounds with the menthane carbon skeleton (10.9-18.0% and ≤1.2%, respectively) and by the content of limonene (3.7-11.0% and not detected, respectively). All essential oils included furyl containing monoterpenoids. Young shoots biosynthesized 3-4 times larger amounts of essential oils and contained larger quantities of terpenoids than did aged shoots. The content of palustrol in the essential oils of aged shoots was higher than of young ones. The dependence of ledol quantities on the age of shoots was opposite in the localities under study. The sixty nine identified compounds comprised 98.0-99.4% of L. palustre essential oils. [ABSTRACT FROM AUTHOR]

The distribution of polycyclic aromatic hydrocarbons (PAHs) in plant and organic soil from 14 peatland sites in NE Poland and 7 peatland sites in SE Poland have been investigated. The total PAH concentration in the leaves of Ledum palustre collected from peatlands in NE Poland ranged from 232 ng/g to 1523 ng/g and was higher than the total PAH concentration in pine needles (Pinus sylvestris) taken from those same peatlands (the values ranged from 181 to 307 ng/g). A similar trend was observed in the case of plants from the peatlands in SE Poland, except that the overall PAH concentration in the majority of the plant samples was found to be higher than those found in NE Poland. Phenanthrene and fluoranthene had the biggest share in the overall PAH concentration in all the peat and plant samples. The lack of 5- and 6-ringed PAHs in the plant and soil material indicates the lack of any direct emission sources of these compounds in regions adjacent to those examined in the study. Total sum of PAH pollution levels in peats and plants as well as vertical distribution of the concentrations in the soil profile of particular study sites integrates long-range pollution sources. To compare natural and antropogenic PAH input in the pealtlands, we have used parent PAH ratios: ANT/(ANT&PHE ); FLT /(FLT&PYR ). Our data suggest that PAHs with four and more rings do not allow a simple segregation into combustion or petroleum sources. [ABSTRACT FROM AUTHOR]

Conifer-regeneration failure is often observed on sites invaded by ericaceous shrubs. In northeastern Quebec, Canada, these sites are frequently characterized by dense Kalmia angustifolia L. – Rhododendron groenlandicum (Oeder) K.A. Kron & Judd cover. Such failures are potential consequences of nutrient limitation, allelopathy, or low soil temperatures. Conversion of productive forests into heaths poses a threat to the maintenance of forest productivity and biodiversity. We evaluated scarification, spot fertilization, and increased seedling foliar N concentration as treatments to promote planted black spruce (Picea mariana (Mill.) BSP) seedling survival and growth. We measured seedling, vegetation, and soil responses to the treatments for 5 years following planting. Scarification had positive impacts on seedling growth: the differences between scarified and unscarified plots increased over time, and double-pass scarification proved slightly more effective than a single-pass treatment. Responses to scarification were enhanced when seedlings were fertilized. A slow-release fertilizer with micronutrients proved slightly more effective than the 26N–12P–6K formulation; the latter also induced higher mortality than the former or no fertilizer. Gains due to increased N concentrations based on nursery practices were significant but short-lived. Our results demonstrate how silviculture and nursery practices can be used for resetting the secondary succession where ecosystem retrogression is observed following K. angustifolia – R. groenlandicum invasion. [ABSTRACT FROM AUTHOR]

Northern peatlands are substantial sinks of carbon (C), yet the sources of carbon dioxide (CO2) emitted from peatlands are largely unknown. Since the relationship between roots and peat in C cycling is important, vascular plants growing on the surface of peat deposits should influence CO2 efflux from the peat surface and the overall C balance in peatlands. In our study, 30-cm peat cores were removed from an ombrotrophic bog in boreal, continental western Canada. Surface vegetation in the cores remained intact and included a continuous bryophyte cover dominated by Sphagnum fuscum. In addition, some cores were collected such that either ericaceous shrubs (Ledum groenlandicum) or sedges (Eriopho rum vaginatum) were present. We investigated how the presence of each vegetation type influenced soil respiration and the microbial mineralization of root exudates using a pulse 14C labeling of vegetation in the intact peat cores. The role of root biomass and root respiration in CO2 emission and C allocation was quantified for each type of vegetation and compared through both measurement and modeling. Our results show that vascular plants contributed 35-57% of total CO2 efflux from the peat surface, primarily derived from rhizosphere processes, including root respiration as well as microbial mineralization of root exudates. The mineralization of root exudates contributed 14-53 μmol C-CO2∙m-2d-1 (17- 24% of total) to CO2 efflux, depending on vegetation type and moisture conditions. The type of vegetation present did not influence the total amount of photosynthetic fixation over the course of the study, but did affect how C was allocated within and between both the aboveground and belowground components of the peat column. [ABSTRACT FROM AUTHOR]

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Alpine populations of Ledum groenlandicum Oeder have higher photosynthetic rates and appear to achieve maximum photosynthesis at lower temperatures than bog populations. These photosynthetic differences presumably adapt alpine populations to the shorter seasons, lower carbon dioxide concentrations, and lower temperatures experienced in alpine environments, and they agree with similar patterns observed in other species which grow at a range of elevations. Reciprocal transplant experiments show that the differences in photosynthetic characters are correlated with differences in the relative fitnesses of bog and alpine plants in bog and alpine environments. [ABSTRACT FROM AUTHOR]