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The effects of leaves and litter of the boreal forest understory shrub, Ledum groenlandicum, on soil characteristics and black spruce (Picea mariana) seedling growth were investigated. Organic and mineral soils, not previously associated with L. groenlandicum, were amended with leaves and litter of this species. The objectives of the present study were: (i) to determine the changes in soil characteristics after amending with L. groenlandicum, (ii) to determine the quantitative variation in the concentration of water-soluble phenolic allelochemicals in mineral and organic soil layers modified by L. groenlandicum and (iii) to study the growth response of black spruce in soils treated with different L. groenlandicum amendments. The amended organic and mineral soils were analyzed for pH, organic matter, PO4, N, Ba, Cu, Zn, Fe, Mn, Ca, Na, K, Mg, Al and total phenolics equivalence. Results indicate that organic soils amended with L. groenlandicum leaves and litter were significantly different from unamended control soil for most of the chemical characteristics, while amended mineral soil was different from that of unmodified mineral soil for PO4, organic matter, K and total phenolics equivalence. Water-soluble phenolics from L. groenlandicum and changes in nutrient availability are plausible causes of L. groenlandicum interference with black spruce seedling growth.

A total of 27 extracts from non‐cultivated and weedy vegetables traditionally consumed by ethnic Albanians (Arbëreshë) in the Vulture area (southern Italy) were tested for their free radical scavenging activity (FRSA) in the DPPH (1,1‐diphenyl‐2‐picrylhydrazil radical) screening assay, for their in vitronon‐enzymatic inhibition of bovine brain lipid peroxidation and for their inhibition of xanthine oxidase (XO). In both antioxidant assays strong activity was shown for Leopoldia comosa(bulbs, syn.: Muscari comosum) and Centaurea calcitrapa(young whorls). In the lipid peroxidation assay, extracts from leaves of Origanum heracleoticum, Urtica dioicaand Tordylium apulumshowed a remarkable inhibitory activity (>50%), too. In the case of Leopoldia comosaand Origanum heracleoticumthis activity was comparable to quercetin (at a concentration of 50 μM) and Rhodiola roseaextract. Extracts from non‐cultivated Cichorium intybus, Chondrilla junceaand Stellaria mediashowed strong in vitroinhibition of xanthine oxidase, with an activity higher than that of a reference extract from Ledum groenlandicum. These findings suggest that weedy vegetables may be useful antioxidants of interest in the prevention of ageing related diseases, CNS disorders and as potential sources of phytomedicines against hyperuricaemia and gout. Copyright © 2002 John Wiley & Sons, Ltd.

The rust fungus Chrysomyxa woroninii causes perennial witches' brooms on several species of Ledum in northern and subalpine regions of Europe, North America and Asia. Spruce bud rust has been assumed to be the aecial state of C. woroninii because of the close proximity of infected Ledum plants and systemically infected buds on Picea. The lack of experimental evidence for this connection, however, and the presence of other species of Chrysomyxa on the same hosts has led to confusion about the life-cycle of C. woroninii. In this study, infections on both spruce and Ledum were studied in the field and in a greenhouse. The link between the two states was proven by inoculating spruce with basidiospores from Ledum groenlandicum. After infection of spruce in spring, probably through the needles, the fungus overwinters in the unopened buds until the next spring, when the infected shoots are distinguished by stunting and yellow or red discolouration. Microscopic examination of dormant Ledum shoots showed that C. woroninii overwinters in this host in the bracts and outer leaves of the vegetative buds, and in the pith and cortex of the stem. The telia of C. woroninii, on systemically infected Ledum leaves of the current season, are easily distinguished from the telia of other Chrysomyxa species on the same hosts. The latter produce localized telia and uredinia only on overwintered leaves, produce aecia on spruce needles in the same year as infection occurs, and are not systemic in spruce. The restricted habitat distribution of C. woroninii and the need for overwintering outdoors suggest that this rust fungus has specific environmental requirements for survival.

This study documents changes in community and functional group across environmental gradients sensitive to climate warming in boreal permafrost peatlands and describes how future changes in temperature and precipitation may lead to changes in species composition and ecosystem properties. At the landscape scale, the presence of permafrost strongly influenced species composition. The position of permafrost thaw affected surface water pH and species composition. At local scales, a combination of water table depth and vegetation structure strongly controlled community composition. Permafrost plateau plots with high Picea marianabasal area were characterized by darker and drier understorey conditions, low cover of Sphagnumfuscum, Ledum groenlandicum, and lichen, and high cover of feather mosses. Aquatic collapse scar plots were dominated by aquatic Sphagnumand Carex, whereas more xeric plots were dominated by hummock Sphagnumand ericaceous shrubs. Functional group responses indicated that changing environmental conditions with climate warming may have significant impacts on community composition and ecosystem processes. A decomposition example is presented to show how changes in species and functional group composition could have important implications for ecosystem-level processes like peat accumulation during climate warming.Key words: bogs, fens, boreal, permafrost, vegetation, ordination

The teleomorphic state of the ericoid mycorrhizal Hymenoscyphus ericae is known only from the type deposition. The production of both the teleomorph and anamorph by an isolate recovered from Ledum groenlandicum collected in an acidic peatland in Alberta, Canada, provided an opportunity to describe and illustrate the holomorph for a North American collection as a new record and as a supplement to the original diagnosis. It also provided further evidence that Hymenoscyphus ericae and Scytalidium vaccinii represent states of a single species, a hypothesis that previously had been tested using nuclear ribosomal DNA analysis. Appropriate cultural conditions and the use of molecular markers are advocated in order to facilitate the identification of mycorrhizal isolates which often remain sterile in pure culture.

Four small oligotrophic basin mires on the Precambrian Shield were quantitatively analyzed for vegetation patterns and surface water and groundwater chemistry. Mean concentrations of ions in the surface waters of all vegetation stands indicate these mires to be characterized by low calcium content (0.6–1.9 mg Ca L−1), low corrected conductivity (12–31 μmho cm−1(1 mho = 1 S)), and relatively high pH (4.0–5.7). Mire 224 is dominated by Chamaedaphne calyculata, Scheuchzeria palustris, and Carex oligosperma. The surface water mean determinations are Ca, 1.10 ± 0.51 mg L−1; Mg, 0.57 ± 0.2 mg L−1; corrected conductivity, 16.7 ± 4.2 μmho cm−1; and pH 4.37. Abundance patterns of the dominant Carexspecies can be correlated with pH of the surface water of the mire. Mire 239 is characterized by Smilacina trifolia, Ledum groenlandicum, and Carex trisperma. The mean surface water determinations are Ca, 1.53 ± 0.36 mg L−1; Mg, 0.59 mg L−1; corrected conductivity, 21.2 ± 2.0 μmho cm−1; and pH 4.0. Significant differences in pH, Ca, and Mg occur between the interior and edge portions of this bog. Water chemistry from portions burned in 1974 showed no difference from unburned portions. The vegetation of mire 661 contains a sequence of communities positioned relative to the inflow streams, with a Myrica gale– Alnus rugosacommunity followed by a zone dominated by Picea marianathen a Larix laricinazone and then by an open Sphagnum papillosum– Menyanthes trifoliatalake edge zone. More ombrotrophic areas are dominated by Sphagnum fuscum. Ca, Mg, and Fe concentrations, pH, and corrected conductivity were reduced through this sequence. Comparison of weekly samples of water entering and leaving this mire in 1981 showed a reduction of Ca, Mg, SO4, NO3N, alkalinity, and pH.

Three patterned fens in north central Alberta were analyzed to elucidate vegetation patterns in vascular plants and bryophytes. Two flark associations dominated by Menyanthes trifoliataand Carex limosa, both of which had Sphagnum jenseniiand Drepanocladus exannulatusphases, were recognized. The strings consist of two associations; one is dominated by Betula glandulosa, Tomenthypnum falcifolium, and Aulacomnium palustre; the second is dominated by Picea mariana, Sphagnum magellanicum, and Ledum groenlandicum. An intensive analysis of one fen reveals that these mires are ‘poor fens’ with a mean pH of 5.2 and Ca2+concentration of 2.3 ppm. The fens occur on low drainage divides and Ca2+is depleted as water flows through the fens. An ecological series of bryophytes is described in the transitions between flarks and strings.

Open woodland forests dominated by Pinus banksianaoccur on sandy soils in northeastern Alberta and northwestern Saskatchewan and are generally even-aged and uniform in height. Ordination techniques were used to divide the stands (n = 38) into the following communities: Pinus banksiana/Vaccinium myrtilloidesseral community; Pinus banksiana/Cladina mitis, Pinus banksiana/Vaccinium myrtilloides/Cladina mitisin uplands; and Pinus banksiana–Picea mariana/Ledum groenlandicum/Cladinaspp. in lowlands. Fires occur with a mean return interval of 38 years (range at six locations, 28–54 years). Pinus banksianarecolonizes rapidly after fire, and average thickness of lichen cover is reached in 45 years. This is a shorter time interval for recovery than is reported for the Northwest Territories. Stands that escape fire 90+ years become more open in upland sites, but in lowlands Picea marianabecomes codominant with associated shift in lichen species and an increase in bryophytes.

The seasonal timing of shoot extension by three ericaceous shrubs (Ledum groenlandicum, Chamaedaphne calyculata, and Kalmia polifolia) was monitored at eight peat bogs along an 800-km latitudinal transect through Ontario, Canada, and at a transplant garden containing plants from four of the peat bogs. The timing of shoot extension varied among plants from different locations, both in the transplant garden and in the field. A regression model containing two independent variables (heat units (i.e., degree-days) and either the average annual degree-day total for a plant's geographic origin or the average frost-free period) could account for 95 to 99% of the seasonal plus intersite variation in shoot extension recorded in the transplant garden. The seasonal pattern of shoot extension predicted for each of the eight peat bogs with the regression model was close to the observed pattern in most cases. The average difference between predicted and observed percentages of shoot extension ranged from 4% for L. groenlandicumto 7% for K. polifolia.

Labrador tea (Ledum groenlandicum), a slow-growing late successional evergreen, is highly unpalatable to snowshoe hares (Lepus americanus). Germacrone, a sesquiterpene that is the major component of the essential oil ofL. groenlandicum, was shown by bioassay to be a potent antifeedant to hares. Its concentrations in leaves and intemodes of the plant are high enough to defendL. groenlandicum from hares. This chemical defense of Labrador tea from herbivory is consistent with the resource availability theory of antiherbivore defense.

For 21 study sites in the Acadia Forest Experiment Station, near Fredericton, New Brunswick, 34 commonly occurring understory species were studied to determine the depth of underground plant organs capable of growing shoots. Depth of these plant parts tended to be species specific. These depth data, together with a knowledge of the sprouting ability of the underground organs, were used to postulate which species would survive fires of varying intensities. Most species found in the litter layer or in the F and H layer of the forested study sites would be susceptible to fires of low intensity. Rubus canadensis, Kalmia angnstifolia, Vaccinium myrtilloides, Pteridium aquilinum, and Viburnum cassinoideswould probably survive severe fires because the subterranean plant organs capable of reproduction were found in the mineral soil. In the bog study sites, Vaccinium oxycoccos, Andromeda glaucopliylla, Kalmia angustifolia, Chamaedaphne calyculata, Ledum groenlandicum, and Rhododendron canadensewould likely survive severe fires because the plant organs capable of vegetative reproduction were found 25 cm below the surface of the bog.

Individual leaves of three bog ericads, leatherleaf (Chamaedaphne calyculata), bog laurel (Kalmia polifolia), and Labrador tea (Ledum groenlandicum), were retained for a maximum of two growing seasons in a peat bog in southern Ontario. The premature loss of mature leaves, resulting from artificial defoliation, significantly reduced the growth of new shoots of L. groenlandicumand K. polifoliabut not of C. calyculata. Defoliation effects were directly proportional to the normal retention time for overwintering leaves. Mature leaves probably translocate photosynthate, nitrogen, and phosphorus to other plant parts. This would explain why leaf dry weights were greatest at the start, rather than at the end, of the leaves' second growing season. Net photosynthetic rates decreased with leafage, but in terms of leaf nitrogen content, new and old leaves fixed equal amounts of carbon.

Bog ericads, such as Labrador tea (Ledum groenlandicum), bog laurel (Kalmia polifolia), and leatherleaf (Chamaedaphne calyculata), retain individual leaves for two growing seasons in southern Ontario, presumably to facilitate nutrient movement between overlapping leaf cohorts. The objective of this study was to evaluate the effects of nutrient availability, shade, and the removal of new growth on the longevity of leaves during their second growing season. Longevity was extended significantly (p < 0.05) by removing new growth, but not by shading leaves (p > 0.05). The addition of nitrogen fertilizer increased only C. calyculatalongevity. Interspecific variation in treatment effects appeared to be related to the positions occupied by the three species on environmental gradients. None of the experimentally treated leaves survived past the end of their second growing season, with the magnitude of treatment effects ranging from a reduction in longevity of 10 days to an increase of 25 days.

During powerline construction, a portion of a wooded (Picea mariana) peat plateau in northern Manitoba was stripped of surface vegetation. Seven years later, aerial biomass of plants recolonizing the surface of the disturbed area was estimated to be 2098 kg ha−1, only 26.4% of the undisturbed portion's aerial biomass of 7939 kg ha−1.Tree biomass represented 28.7% of the aboveground biomass of the wooded plateau. The relative proportions of photosynthetic phytomass increased from 17% in the wooded to 53% in the disturbed area. Major ericaceous species (Ledum groenlandicum, Chamaedaphne calyculata, and Kalmia polifolia) responded after disturbance by increasing reproductive effort and the ratio of photosynthetic to woody tissue.Permafrost subsidence in the disturbed portion was not evident in the period since vegetation removal, although surface erosion of peat was visible and could be expected to increase in the next several years.

The pattern of geographic variation in the annual shoot production of the three bog shrubs (leatherleaf (Chamaedaphne calyculata), bog laurel (Kalmia polifolia), and Labrador tea (Ledum groenlandicum) was examined using data collected at eight peatland sites along an 800-km latitudinal transect. Productivity varied significantly among sites, with L. groenlandicumexhibiting the greatest range of values (114–505 mg/shoot), followed by K. polifolia(83–341) and C. calyculata(73–241). This variation could be best interpreted by including both climatic and substrate variables in a multiple regression equation. The combination of three site variables (heat sum, depth to standing water, and water conductivity) accounted for between 63 and 86% of the observed variation in shoot productivity. Adding four other variables increased the percentage of variation explained to between 95 and 99%.

In Rhododendron spp. and Ledum groenlandicum a callose wall is laid down around the zygote in the first 2 days after fertilization. The periodic acid/Schiff-positive, aniline blue-fluorescence-positive callosic wall is initiated adjacent to the degenerating synergid, extends to cover the entire zygote surface, and remains visible during the initiation of embryogeny as the zygote elongates before the first proembryonal division. Unfertilized ovules show eventual callose deposition in the ovule wall cells during senescence in undeveloped abscising pistils, but show no development of callose within the embryo sac. Possible roles of a zygote special callose wall are discussed.

Random samples of Cladonia alpestrisshow a strong correlation of podetial length, podetial diameter, and internode length, with soil moisture. The level of soil moisture is effectively an integration of net radiation and thus also reflects drying rates of the lichen canopy and the relative metabolic activity of the lichen. The existence of a large-scale mosaic pattern of 'drying rates' is demonstrated by traditional pattern analysis. The interactions of all pattern scales in Cladonia alpestris, C. rangiferina, Ledum groenlandicum, and lichen depth are examined by covariance analysis and interpreted in terms of water relations of the lichen. Experimental evidence is presented of the relative magnitude of evaporation gradients in open and closed spruce–lichen woodland.

In laboratory freezing trials, cold hardiness of six types of bog ericad flowers differed significantly (i.e., Chamaedaphne calyculata> Andromeda glaucophylla> Kalmia polifolia> Vaccinium myrtilloides> Ledum groenlandicum> Vaccinium macrocarpon) at air temperatures between −4 and −10 °C but not at temperatures above −2 °C. At the Luther Marsh bog in southern Ontario, low temperatures (−3 to −7 °C) would select against May flowering by the least cold hardy ericads. Availability of pollinators, on the other hand, would encourage May flowering by the most cold hardy species. Presumably, competition for insect pollinators has promoted the diversification of bog ericad flowering peaks, while air temperature, in conjunction with flower cold hardiness, determined the order in which flowering peaks were reached.

The reproduction of lowbush blueberry (Vaccinium angustifolium Aiton) is closely tied to insect pollination, owing to self-incompatibility. Many species are known to have greater pollination efficiency than the introduced Apis mellifera L., commonly used for commercial purposes. In this study, we measured the pollen loads of several antophilous insect species, mostly Apoidea and Syrphidae, present in four lowbush blueberry fields in Lac-St-Jean, Québec. To measure pollen loads and species specificity toward V. angustifolium, we net-collected 627 specimens of pollinators, retrieved their pollen loads, identified pollen taxa, and counted pollen grains. We found that the sizes of pollen loads were highly variable among species, ranging from a few hundred to more than 118,000 pollen grains per individual. Bombus and Andrena species in particular carried large amounts of Vaccinium pollen and thus may have greater pollination efficiency. Also, two species (Andrena bradleyi Viereck and Andrena carolina Viereck) showed nearly monolectic behavior toward lowbush blueberry. Finally, we identified alternative forage plants visited by native pollinators, notably species of Acer, Rubus, Ilex mucronata, Ledum groenlandicum, and Taraxacum. Protecting these flowering plants should be part of management practices to maintain healthy pollinator communities in a lowbush blueberry agroecosystem.