S42x Atlantic Erica-Ulex heaths

Description

Short (<1 m) lowland heaths on acid, leached soils, eroded by winter rains after human deforestation, impoverished and thinned, all of which reduces their capacity to store water and may occasionally lead to severe drought.

Protection

Protected under the code 4030 ("European dry heaths") by the EU Habitat Directive (certain coastal stands might qualify as the prioritary 4040*["Dry Atlantic coastal heaths with Erica vagans"], but, judging by the definition in the official Manual, not those topping sea-cliffs right above N316, as it has been generally but inappropriately accepted).

Floristic Composition

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Floristic Composition

Frequent species show the percentage of occurrence of species in each habitat, with higher values indicating more observations within the total number of samples. Indicator species show the fidelity of species to each habitat, with higher values indicating a stronger association, based on the IndVal metric (Dufrêne & Legendre, 1997). All species values were obtained from numerical classification (Jiménez-Alfaro et al. 2025). The classification of anthropogenic habitats (EUNIS code “V”) was conducted separately (Fernández-Pascual et al. 2025).

References

• Dufrêne, M., & Legendre, P. (1997). Species assemblages and indicator species: the need for a flexible asymmetrical approach. Ecological monographs, 67(3), 345-366.
• Fernández-Pascual, E., González-García, V., Ivesdal, G., Lázaro-Lobo, A., & Jiménez-Alfaro, B. (2024). Classification and Characterization of Anthropogenic Plant Communities in the Northwestern Iberian Peninsula. Applied Vegetation Science, 28(1), e70010. https://doi.org/10.1111/avsc.70010
• Jiménez-Alfaro, B., González Le Barbier J., Carlón L., Álvarez Martínez JM, Espinosa del Alba, C., Fernández-Pascual, E., González-García V., Lázaro-Lobo A, Mendieta-Leiva, Roces Díaz JV (2025) Regionalization of European EUNIS habitat classification for effective ecosystem assessment. In prep.

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Frequent species

Ulex minor aggr. 85%, Erica cinerea 80%, Calluna vulgaris 74%, Daboecia cantabrica 69%, Agrostis curtisii 65%, Potentilla erecta 60%, Erica vagans 53%, Helictotrichon thorei 46%, Pteridium aquilinum 45%, Cirsium filipendulum 27%, Erica ciliaris 26%, Helictochloa marginata 24%, Danthonia decumbens 24%, Ulex europaeus aggr. 22%, Agrostis capillaris 22%, Serratula tinctoria 22%, Glandora diffusa 21%, Molinia caerulea 21%, Brachypodium pinnatum 20%, Erica tetralix 20%, Glandora prostrata 16%, Potentilla montana 15%, Erica umbellata 15%, Polygala vulgaris 15%, Polygala serpyllifolia 15%, Arenaria montana 14%, Halimium alyssoides 14%, Vaccinium myrtillus 14%, Avenella flexuosa 13%, Stachys officinalis 13%, Simethis mattiazzii 12%, Scilla verna 12%, Carex pilulifera 12%, Carex binervis 11%, Lotus corniculatus 11%, Hypochaeris radicata 11%, Erica mackayana 11%, Hypericum pulchrum 11%, Galium saxatile 9%, Genista tridentata 9%, Viola riviniana aggr. 9%, Festuca rubra 9%, Teucrium scorodonia 8%, Erica arborea 8%, Quercus pyrenaica 8%, Jasione montana 8%, Pilosella officinarum 7%, Blechnum spicant 7%, Quercus robur 7%, Asphodelus albus 7%, Euphorbia polygalifolia 6%, Rubus ulmifolius 6%, Anthoxanthum odoratum 6%, Scorzonera humilis 6%, Gentiana pneumonanthe 6%, Neoschischkinia truncatula 6%, Cruciata glabra 5%, Genista micrantha 5%, Carex flacca 5%, Pedicularis sylvatica 5%, Erythronium dens-canis 5% view more...

Indicator species

Ulex minor aggr. 0.83, Erica cinerea 0.74, Daboecia cantabrica 0.63, Agrostis curtisii 0.6, Potentilla erecta 0.5, Calluna vulgaris 0.49, Helictotrichon thorei 0.42, Erica vagans 0.39, Erica ciliaris 0.25, Cirsium filipendulum 0.25, Pteridium aquilinum 0.24, Danthonia decumbens 0.21, Serratula tinctoria 0.21, Molinia caerulea 0.19, Helictochloa marginata 0.16, Polygala serpyllifolia 0.14, Agrostis capillaris 0.13, Potentilla montana 0.13, Glandora diffusa 0.13, Erica tetralix 0.12, Glandora prostrata 0.11, Stachys officinalis 0.11, Polygala vulgaris 0.11, Scilla verna 0.11, Carex pilulifera 0.11, Erica mackayana 0.11, Brachypodium pinnatum 0.1, Erica umbellata 0.1, Carex binervis 0.1, Simethis mattiazzii 0.09, Arenaria montana 0.09, Hypericum pulchrum 0.09, Hypochaeris radicata 0.07, Halimium alyssoides 0.07, Lotus corniculatus 0.06, Scorzonera humilis 0.05, Festuca rubra 0.05, Euphorbia polygalifolia 0.05, Asphodelus albus 0.05, Gentiana pneumonanthe 0.05, Pilosella officinarum 0.05, Pedicularis sylvatica 0.05, Galium saxatile 0.05, Viola riviniana aggr. 0.04, Laserpitium prutenicum 0.04, Anthoxanthum odoratum 0.04, Erythronium dens-canis 0.04, Cuscuta epithymum 0.04, Blechnum spicant 0.03, Jasione montana 0.03 view more...

Phytosociology i

Phytosociology

List of phytosociological associations described in the Ibero-Atlantic region for each habitat. The association concepts mainly follow Rivas-Martinez et al. (2001), with further updates by Fernández-Prieto et al. (2023), and others.

References

• Rivas-Martinez, S., Fernández González, F., Loidi Arregui, J., Fernández Lousã, M. & Penas Merino, A. (2001) Sintaxonomical checklist of vascular plant communities of Spain and Portugal to association level. Itinera Geobotanica 14., 5-341. Fernández Prieto, J.A., Amigo, J., Bueno, A., Herrera, M., Rodríguez-Guitián, M.A. & Loidi, J. (2023) Bosques y orlas forestales de los territorios atlánticos del Noroeste Ibérico. Guineana, 23, 3–240 https://doi.org/10.1387/guineana.25055

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• Angelico pachycarpae-Ulicetum maritimae
• Arctostaphylo crassifoliae-Daboecietum cantabricae
• Cirsio filipenduli-Ericetum ciliaris
• Cisto salviifolii-Ulicetum humilis
• Daboecio cantabricae-Ulicetum gallii
• Erico tetralicis-Ulicetum gallii
• Gentiano pneumonanthes-Ericetum mackaianae
• Halimio alyssoidis-Ulicetum breoganii
• Halimio umbellati-Daboecietum cantabricae
• Sileno maritimae-Ulicetum humilis
• Ulicetum latebracteato-minoris
• Ulici breogani-Ericetum mackaianae
• Ulici europaei-Ericetum cinereae
• Ulici europaei-Ericetum vagantis
• Ulici gallii-Ericetum ciliaris
• Ulici humilis-Ericetum vagantis

Relations with other habitat types

These heathlands are mostly interpretable as a dysclimax of the unit T1Bx. In the northernmost areas, cool and cloudy summers keep the organic litter permanently wet, enabling transitions towards S412 and even Q12x. Since, for geographic reasons, EUNIS would include some of the heaths in this unit of in its S423 and others in S424, such units are inconsistent with our results and a new regional umbrella level IV unit is in order. In more inland, drier-summer, submediterranean areas, they transition towards S42y.

S42x

S42x

S42x

S42x

S42x

The most likely original position of this shrubland, as revealed by the tiny, very dispersive seeds of Erica and its massive flowering, seen from afar, were scattered steep siliceous ridges where trees couldn't stand, soils were intensively leached by rains and wind in winter and, in summer, very dry and, hit by lightning, exposed to episodic spontaneous fires, setting the selective pressures leading to all these short, profusely flowering, ligneous, evergreen, small-leaved, tiny-seeded, resprouting shrubs and their characteristic fungal root partnership with lignicolous fungi. Anthropic deforestation through fire, starting some 6000 years ago, by eliminating taller competitors and chronically impoverishing soils, gave them an unexpected advantage and inverted the ancient picture, turning the original shrubby islands into the new matrix and relegating forests into isolated pockets. In recent decades, heathlands in coastal areas have experienced a frank regression, replaced by industrial pine or eucalyptus plantations or, in flat areas suitable for mechanised agriculture, by fodder crops or artificial meadows, plowed and improved with synthetic fertilisers. Heathlands in S42y, for mutually reinforced climatic, topographic and socioeconomic reasons, are less affected by these regressive trends.

Known occurrences and potential area of occupancy of the habitat type in the study region.