<i>Trientalis europaea</i> L.

Trientalis L. A perennial herb of the family Primulaceae, with a slender stoloniferous rootless rhizome, creeping horizontally close to the soil surface and an erect, glabrous stem 10–25 cm. Adventitious roots, developed on the tuber produced at the tip of each rhizome, occur in the soil surface organic layers. Leaves 10–90 × 5–15 mm, obovate to lanceolate, subsessile, stiff and shining, entire to minutely dentate at the apex, with cuneate base. Leaves (3–)5–8(–10) in a whorl at the top of the stem (occasionally a few alternate leaves below). Flowers usually 1–2 (rarely 3–4), erect (5–)7(–9)-merous, axillary, solitary on capillary pedicels (1–7 cm), ebracteate. Calyx 4–7 mm, deeply divided, teeth linear. Corolla rotate, 11–19 mm in diameter, white or tinged with pink; segments ovate, acuminate or acute; erecto-patent, longer than tube. Stamens (4–)6–7(–8) included; filaments adnate to top of tube. Superior ovary 1-celled, formed by the fusion of 5(–7) carpels; style 1 with capitate stigma. Capsule globose, c. 6 mm, average number two per plant; valves 5(–7) deciduous, leaving the seeds attached to the free-central placenta. The genus Trientalis is a complex of more or less boreal taxa with a circumpolar distribution (Hiirsalmi 1969; Anderson & Loucks 1973; Vergl. Chor., Vol. 2, 1978; Hultén & Fries 1986), including T. europaea, which is the native plant in the British Isles and in continental Europe. Phenotypically, T. europaea exhibits considerable plasticity which is expressed as variation in the morphology of all the vegetative and floral organs (Matthews & Roger 1941; Kovanda 1995). For a polyploid species with a vast geographical range, occurring in a variety of habitats, it is quite surprising that, from the taxonomic viewpoint, this variation appears to be negligible, not producing any appreciable infraspecific units (Kovanda 1995). However, both experimentally determined morphological and physiological differences appear to differentiate ecotypically a subarctic Swedish population from two British populations of T. europaea[see VI (E)]. Trientalis europaea is a native herb of open pine-woods, sessile oak-birchwoods and heather-moors, among moss in damp grassy places, usually rooting in humus, and mostly absent from both the driest and the wettest sites. Trientalis europaea is very local in England (Fig. 1): with a single record for Fritton in East Suffolk, now probably extinguished by flooding and felling (P. Lambley, personal communication); a single record in the Sheffield District of South Yorkshire (Clapham 1969), now effectively the southernmost locality; several localities in West and North Yorkshire northwards into Durham and Northumberland; with two records for north Lancashire (Livermore & Livermore 1987; P. Jepson, personal communication); and four sites in Cumbria (Halliday 1997). Mainly distributed throughout central and northern Scotland with an eastern bias (not recorded from the Inner or Outer Hebrides), locally common. Rare in Orkney (Bullard 1972); on Fair Isle; occurs locally in the Shetland Islands where it is often very dwarf (the so-called var. nana Druce), mainly found in the Dunrossness district of the southern Mainland (Palmer & Scott 1969), but also abundant on the hill behind Grutness, western Mainland (Scott & Palmer 1987). It occurs throughout northern Europe, extending southwards, mainly in the mountains, such as the Bohemian Massif especially in the Sudeten Mountains (Kovanda 1995), to the southern Alps, northern Romania and as far south as Corsica in the Mediterranean (Fig. 2). The distribution of Trientalis europaea in the British Isles. Each dot represents at least one record in a 10-km square of the National Grid. (○) pre-1950; (•) 1950 onwards. Mapped by Mrs J. M. Croft, Biological Records Centre, Centre for Ecology and Hydrology, mainly from records collected by members of the Botanical Society of the British Isles. The main distribution of Trientalis europaea in Europe and western Asia (modified from Vergl. Chor., Vol. 2, 1978; Danton & Baffray 1995; Kaesermann & Moser 1999). The base map is reproduced by permission of the Committee for the Mapping of the Flora of Europe (the bold dashed line shows the limits of Europe). Outside Europe, T. europaea extends eastwards throughout almost the whole of northern Asia to Okhotsk and Kamchatka; to Japan; in western North America, from Alaska southwards to British Columbia, Alberta and into California (Hiirsalmi 1969; Vergl. Chor., Vol. 2, 1978); and more recently recorded as a new species in Greenland (Bay 1993). Trientalis europaea is included in the northern montane element (Dist. Br. Fl.) and classified as circumpolar Boreal-montane by Preston & Hill (1997). The altitudinal range of T. europaea in the British Isles extends from sea level on the east coast in Aberdeenshire, Scotland to an upper limit of 1082 m on Lochnagar (Matthews & Roger 1941). It ascends to 600 m in northern Norway, to 1000 m in northern Sweden and to 1580 m on Jotunheimen, southern Norway (Atl. N.W. Eur.); up to 1380 m in the Hrubý Jeseník Mountains, Czech Republic, up to 1430 m in the Böhmerwald, Germany, to 1635 m in the Tatra, Slovenia, to 1400–1700 m in the Tirol, Austria (Vergl. Chor., Vol. 2, 1978), up to 1800 m in France (Danton & Baffray 1995), and in Switzerland in the cantons of Schwyz to 900 m, of Bern to 1400 m, of Ticino to 1700 m and of Grisons (= Graubünden) up to an altitude of 1900–2100 m (Kaesermann & Moser 1999). The 15.6 °C July mean isotherm approximates to the southern (lower) distribution limits of T. europaea in the British Isles (Atl. Br. Fl.). The geographical distribution and altitudinal restriction at the southern limits of its range in Europe correlate well with relatively high mean summer temperatures, i.e. limited by high temperatures. It has been demonstrated experimentally that the optimum temperature for carbon assimilation in T. europaea is 11–18 °C and that it declines at higher temperatures [see VI (E)]. Absent from the most open and most deeply shaded sites; characteristic habitats include moderately shaded sites in coniferous and deciduous woodland, and in treeless heathlands beneath the canopies of Calluna vulgaris, Juniperus communis, Myrica gale or Pteridium aquilinum. Less commonly, T. europaea occurs in open mountain mire communities and as part of a remnant ground flora after recent forest clear-felling. It has been shown that the growth performance of T. europaea is significantly reduced in open as compared to shaded sites [see V (B), VI (E)]. Trientalis europaea is a strict calcifuge, being found on soils which have highly acidic, humus-rich surface horizons (Table 1). The results of an assay of nitrate reductase activity in the leaves of T. europaea in native pinewood sites suggest that there is very little NO3− available during the growing season, but when fertilized with KNO3 the leaves do appear to possess the inducible isoform of the enzyme and have the capacity to assimilate NO3− (Table 2). However, in common with other non-nitrophilous species, T. europaea is more likely to utilize mixed sources of N (NO3−, NH4+ or organic-N) by root rather than shoot assimilation (Pearson et al. 1998). The species has also been reported to occur on a slightly podzolized brown loam (pH 5.2) in Vaccinium-rich birchwood (Pl. Comm. Scot.; Veg. Scot.), and on a humus iron podzol (pH 4.0–4.4) in a Betula pubescens community (Birse & Robertson 1976). In birch forest in northern Sweden, T. europaea also occurs on an iron podzol with a thick humus horizon (4–42 cm depth) of pH 3.7–4.3 in Vaccinium myrtillus dominated stands, and in Geranium–Vaccinium myrtillus stands with a thinner humus horizon (3–7 cm depth) of pH 4.2–5.2 (Sonesson & Lundberg 1974). The National Vegetation Classification records T. europaea in a range of communities (Rodwell 1991a,b). It is frequent in the Anemone nemorosa subcommunity of Quercus petraea–Betula pubescens–Oxalis acetosella woodland (W11), in north-east Scotland, where the oak when present shows some obvious robur characteristics. This vegetation type has affinities with communities described in earlier studies: in highland birchwood and oakwood (Tansley, Br. Isl.) and in the herb-rich birch and oakwood association of McVean (Veg. Scot.); in Aberdeenshire, north-eastern Scotland, T. europaea has been reported to occur locally in planted Beechwood, essentially type W11 in which there has been a canopy replacement with beech, on deep fertile loam derived from Old Red Sandstone (Watt & Tansley 1932; Tansley, Br. Isl.); and T. europaea and Luzula pilosa differentiate the seminatural Trientali-Betuletum pendulae association, which is largely found in the eastern Grampian mountains, from the other communities in the order Quercion robori-petraeae (Birse 1982). On base-poor soils T. europaea is occasional in the Rhytidiadelphus triquetrus subcommunity of Quercus petraea–Betulapubescens–Dicranum majus woodland (W17), which occurs in the more continental parts of eastern Scotland. This is equivalent to the Trientali-Betuletum pendulae subassociation with Vaccinium vitis-idaea of Birse (1982). Trientalis europaea is frequent in Juniperus communis ssp. communis–Oxalis acetosella woodland (W19) at high altitudes within the east-central Highlands of Scotland, particularly the hills of the Cairngorm and Monadhliath ranges. This vegetation type unites a variety of previously described kinds of scrub or woodland, more and less calcifugous, including that dominated by Betula pubescens ssp. odorata in the Morrone Birkwoods National Nature Reserve, near Braemar in Upper Deeside, Grampian Region, Scotland, the finest example in Britain of a subalpine woodland comparable with and floristically similar to some Norwegian and northern Swedish subalpine birchwoods. In this habitat, T. europaea is a constant species which occurs under a more or less continuous but low-growing understorey of Juniperuscommunis ssp. communis, both where the tree canopy is open in the Juniperus communis-Vaccinium vitis-idaea nodum, and in the treeless Juniperus communis-Campanula rotundifolia nodum (Huntley & Birks 1979). Trientalis europaea is scarce in Pinus sylvestris–Hylocomium splendens woodland (W18), especially in the drier eastern Scottish Highlands in the Speyside and Deeside forests. This vegetation type includes native pinewoods in Scotland (Steven & Carlisle 1959); where T. europaea is occasional to locally frequent in a dry Deschampsia flexuosa–Hypnaceous moss community; occasional in a dry Vaccinium–Deschampsia–Hypnaceous moss community, in both a dry and a moist Calluna–Vaccinium–Deschampsia-moss community, and in a dry grass pinewood community. It also includes communities described by McVean & Ratcliffe (Pl. Comm. Scot.) in the Scottish Highlands where T. europaea is thinly distributed in the Pinetum Hylocomieto-Vaccinietum, and sparse in the Betuletum Oxaleto-Vaccinietum association. According to Birse & Robertson (1976), T. europaea, which is a character species of the order Vaccinio-Piceetalia, is scattered in the Betula pubescens community and scarce in Erica cinerea–Pinus sylvestris plantations at lower altitudes in Scotland. Trientalis europaea is occasional in Carex curta–Sphagnum russowii mire (M7), in the Carex aquatilis–Sphagnum recurvum subcommunity, which is concentrated around the Clova–Caenlochan area of the east-central Highlands of Scotland. It is scarce in Carexrostrata–Sphagnum warnstorfii mire (M8), mainly in the Central Highlands of Scotland essentially as described by McVean & Ratcliffe (Pl. Comm. Scot.); and also in Trichophorum caespitosum (Scirpus cespitosus)–Erica tetralix wet heath (M15), particularly in the western Highlands of Scotland. Trientalis europaea is also found sparsely in two heathland communities: Calluna vulgaris–Vaccinium myrtillus heath (H12), in the east-central Highlands, south-east Scotland and the North York Moors; and in Calluna vulgaris–Arctostaphylos uva-ursi heath (H16), which occurs widely but fairly locally through the east-central Highlands of Scotland, especially in Speyside. In the Shetland Isles, T. europaea occurs locally in a few sites, including a very exposed headland, Compass Head, near the southern tip of south Mainland c. 70–100 m above mean sea level, which in winter and summer storms is drenched in salt spray. At this site it is associated with at least 31 other species in a sheep and rabbit grazed habitat, including Armeria maritima ssp. maritima, Calluna vulgaris, Danthonia decumbens, Galium saxatile, Holcus lanatus, Juncus squarrosus, Molinia caerulea, Nardus stricta, Plantago maritima and Potentilla erecta (T. Russell, personal communication). Above the timberline in the mountain regions of Lappland, in the low-alpine belt, the vegetation is dominated by low growing plants including stunted forms of ‘lowland’ plants, such as Trientalis europaea, Vaccinium myrtillus, V. vitis-idaea and V. uliginosum (Rune 1965). In the subalpine belt in the Torneträsk area of northern Sweden, T. europaea occurs in open forest ecosystems in which Betula pubescens f. tortuosa is the most abundant tree. Where the ground vegetation is of the heath type, T. europaea is frequent in the Vaccinium myrtillus type and variants and in the Geranium–Vaccinium myrtillus type (Sonesson & Lundberg 1974). This continental subalpine birchwood subregion extends southwards in Fennoscandia on the eastern slopes of the Lapponian Scandes. Below these birchwoods, Piceeto-Vaccinietum myrtilli is the prevailing kind of forest on mesic soils with a typical mor humus, predominant in the north, but also widespread in southern Sweden in the Boreo–nemoral zone. In this type of conifer forest, the understorey vegetation is usually dominated by Vaccinium myrtillus with co-dominant V. vitis-idaea or Deschampsia flexuosa and Trientalis europaea a local constant (Sjörs 1965). In the Finnish forest zone, T. europaea occurs in spruce mires in which Picea abies is usually the dominant tree, but Betula pubescens is also important (Eurola et al. 1984). In Central Europe, the boreal species Picea abies, Rubus saxatilis and Trientalis europaea are differential species of the north-eastern spruce–lime–hornbeam woods (Ellenberg 1988). Trientalis europaea, an acid-tolerating plant of needle-leaved woodland and related communities, also occurs in the east of the northern plain in Central Europe on glacial sands, as in the spruce–oak–pine wood in the ancient forest of Bialowieža in Poland. It is described by Ellenberg (1988) as a character species of communities in the order Vaccinio-Piceetalia, class Vaccinio-Piceetea, together with Arctostaphylos uva-ursi, Corallorhiza trifida, Diphasium tristachyum, Epipogium aphyllum, Homogyne alpina, Huperzia selago, Juniperus communis ssp. alpina, Linnaea borealis, Listera cordata, Lonicera caerulea, Lycopodium annotinum, Melampyrum sylvaticum, Moneses uniflora, Monotropa hypopitys ssp. hypopitys, Orthilia secunda, Pyrola media, P. minor, P. rotundifolia, Vaccinium uliginosum and V. vitis-idaea. In several mountain systems of the Bohemian Massif, T. europaea occurs in spruce forest, Pinus mugo scrub and subalpine peat bogs (Kovanda 1995). In the Netherlands, Westhoff & den Held (1969) record T. europaea as differential in both Vaccinio-Piceetea and Quercetea robori-petraeae. Trientalis europaea is present in base-deficient fen Birch woods in the north-west of Central Europe, and as a distinguishing species of intermediate mire communities without trees, together with Molinia caerulea, as in the Harz at c. 800 m. It is also found in Calluna heaths in the class Nardo-Callunetea, in inland Jutland (Ellenberg 1988). When loamy Calluna heath in north-west Germany is afforested, T. europaea is a differential species in the Danthonia–pine planted-forest. If birch–oak wood (Betulo-Quercetum) in Central Europe is converted into a coniferous planted-forest, T. europaea is a differential species together with Chamerion (Epilobium) angustifolium, Frangula alnus, Galium hercynicum, Dryopteris carthusiana and Pseudoscleropodium purum in Dryopteris–pine forest (Ellenberg 1988). In the subarctic birch forests of northern Finland, in Utsjoki, an area of Betula pubescens var. tortuosa about 1350 km2 was damaged in 1965–66 by the geometrid larvae of the moth Oporinia (Epirrita) autumnata. In damaged mesic areas of forest, the ground vegetation became more vigorous during the first 4–5 years after the attack, when the loss of the canopy resulted in more light penetration to the communities containing Cornus suecica, Deschampsia flexuosa, Solidago virgaurea and Trientalis europaea. The mean cover values of the species then declined until the pre-damage situation was restored in the ground vegetation (Kallio & Lehtonen 1975). Vegetation data from permanent plots were collected in 1931, 1961 and 1991 in an area protected from logging in boreal forest 20 km north of Oslo, southern Norway. Major changes were found in the vegetation composition during these 60 years. The main changes were a reduction in the frequency of species and the frequency of joint occurrences of species such as Andromeda polifolia, Calluna vulgaris, Cornus suecica, Eriophorum vaginatum, Maianthemum bifolium, Melampyrum pratense, Trientalis europaea, Vaccinium oxycoccos and V. uliginosum. The observed changes were interpreted as being induced by the increasing growth and dominance of Picea abies and Vaccinium myrtillus (Nygaard & Odegaard 1999). By marking individual plants in the field in a coastal locality and transplanting plants to a glasshouse, Wennström & Ericson (1990) have investigated the interaction between T. europaea and the host-specific smut fungus Urocystis trientalis. None of 100 plants but of 100 plants during the that produced plants produced significantly winter than plants of and was low and not between and were of any in in a in a However, in winter collected in from plants of T. europaea, then and was by the in of the The of by on winter in a under two light and was in the and in the a significantly higher level in the more A et al. has determined the of by in to the of T. europaea of populations have been in an area in the of In this area to is in on The above sea level of an is with and with the it was first by of T. europaea be in populations with a low of in The of to be to the intermediate of population in T. europaea. The results of a of a population of T. europaea in an inland mesic spruce forest that the of by Urocystis was lower and the than in the above and was not by reduced and the number and of all of which were with a on the low level of and of the in suggest a of the in the of this The interaction between Urocystis T. europaea, and two and has been in a on on the sea Sweden, by Ericson & Wennström (1997). The results that both the and the to the resulted in a in and a significantly higher level than were found in the data suggest that the not but also have a by the of of by and and of by have been in a population of T. europaea occurring in a mesic spruce forest in Sweden The of area by not any of plant In all of the of T. and during summer and tuber grazed produced and which in a lower winter and produced in the growing Trientalis europaea in sites to a by vegetative [see VI A of this kind from the of each new or also from a et al. have the plasticity of plants of T. europaea developed from in to four of in in a The plants were shaded by a which reduced to of without significantly the of to At after of there was a between and and a with This morphological plasticity to the of as well as to an of distributed in native also to variation in at higher of the plants produced but than at lower This also be of for the and of in the The morphological to has also been in a field in a mesic spruce forest in Sweden by et al. In plots individual were from the first in to the first of with an or In all with and were plants produced more and a main In was not by the By these results with of et al. the of variation in the morphological to be A & with data from the field was to the population of T. europaea in a The that the species was at its in but this was by The of this at the level that was mainly to the performance of in the or that a by In these the of and the of The and at which the of in was suggest that the of the morphological in T. europaea is by a high in the of the growth of T. europaea have been on the in a of forest and also in an area in the and by the of any J. & J. In both localities the plant was locally abundant a of vegetation from the two areas considerable In after the main of vegetative but the of in T. europaea, in most years between and shoot were in 100 × in a × m in each of the two On each previously × m at from the were to at least for the of mean shoot and mean shoot at the site declined significantly and during the there were also but in the equivalent values for the native site and The growth in leaves collected from the two sites, together with from an open and a are in a between July and and was not significantly in all four sites. However, area was in the open sites than in the the lower values of area in the open habitats an to the higher of expressed in the of In the in all four sites a similar to that described for species, Rubus & and for two subalpine birchwood species, Deschampsia flexuosa and Vaccinium myrtillus, at northern et al. 1975). At by N in T. europaea from to comparable with the acidic, of the reported for Rubus a range of habitats field were by J. and J. at in an area of wet heath dominated by Calluna vulgaris, to drier ground dominated by Juniperus The mean shoot of T. europaea in × cm areas in the was and in open areas was at The mean of from shaded areas was compared with from open areas the also at or for of the shoot from the open but from shaded In both these and the pinewood habitats the growth performance of T. europaea was significantly reduced in open as compared to shaded and was associated with the higher of and temperature in the to a in carbon assimilation on [see VI (E)]. The of and on the of forest vegetation the treeless zone, which and at has been by the most forest species, in of from the were Arctostaphylos uva-ursi, Cornus suecica, Deschampsia flexuosa, Trientalis europaea and Vaccinium uliginosum. during the years at Compass Head, Shetland Isles, on an exposed sea top that T. europaea an average population of plants, of which about in any and the plants in were more than 6 cm high (T. Russell, personal communication). in the growing the of T. europaea. According to (1969) mainly the an to ground level temperatures of to °C in southern in damaged such that when the were brown and A of slightly has a the plants and is less than an in the of a At the of the growing season, produced in the summer from the on the of the and In each tuber

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.