T121 Riverine Fraxinus-Alnus forest, wet at high but not at low water

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Description

Deciduous hygrophilous riparian forests dominated by alder in riversides often and sometimes violently flooded, never too far from the permanent riverbed.

Protection

Protegido de manera prioritaria por el Anexo I de la Directiva Hábitat bajo el código 91E0* ("Bosques aluviales de Alnus glutinosa y Fraxinus excelsior [Alno-Padion, Alnion incanae, Salicion albae]").

Floristic Composition

Frequent species

Alnus glutinosa aggr. 100%, Brachypodium sylvaticum 69%, Hedera helix aggr. 68%, Athyrium filix-femina 62%, Salix atrocinerea 56%, Fraxinus excelsior 55%, Viola riviniana aggr. 53%, Corylus avellana 43%, Angelica sylvestris 43%, Geum urbanum 41%, Polystichum setiferum 41%, Carex pendula 40%, Euphorbia amygdaloides 37%, Lonicera periclymenum 36%, Crataegus monogyna 36%, Geranium robertianum 36%, Carex reuteriana 34%, Circaea lutetiana 34%, Hypericum androsaemum 34%, Ranunculus repens 33%, Carex remota 31%, Fraxinus angustifolia 30%, Poa nemoralis 30%, Osmunda regalis 30%, Oenanthe crocata 29%, Sambucus nigra 29%, Schedonorus giganteus 28%, Frangula alnus 28%, Cornus sanguinea 28%, Crepis lampsanoides 27%, Luzula sylvatica 27%, Dryopteris affinis 27%, Eupatorium cannabinum 26%, Dioscorea communis 25%, Rubus ulmifolius 25%, Filipendula ulmaria 25%, Equisetum arvense 24%, Heracleum sphondylium 23%, Scrophularia auriculata 23%, Ajuga reptans 22%, Blechnum spicant 22%, Lamium galeobdolon 21%, Acer pseudoplatanus 20%, Quercus robur 20%, Teucrium scorodonia 19%, Silene dioica 19%, Saxifraga hirsuta 19%, Arum italicum 19%, Lythrum salicaria 18%, Urtica dioica 17%, Euphorbia dulcis 17%, Omphalodes nitida 17%, Primula acaulis 17%, Dactylis glomerata 16%, Elymus caninus 16%, Pteridium aquilinum 16%, Alliaria petiolata 16%, Chaerophyllum hirsutum 16%, Solanum dulcamara 15%, Clematis vitalba 15%, Ligustrum vulgare 15%, Acer campestre 15%, Melica uniflora 15%, Stachys sylvatica 14%, Lysimachia nemorum 14%, Dryopteris filix-mas 14%, Euonymus europaeus 14%, Senecio bayonnensis 14%, Carex sylvatica 14%, Galium aparine aggr. 13%, Asplenium scolopendrium 13%, Laurus nobilis 13%, Aquilegia vulgaris aggr. 13%, Lycopus europaeus 12%, Deschampsia cespitosa aggr. 12%, Prunella vulgaris 12%, Rubus caesius 12%, Oxalis acetosella 11%, Bromus ramosus 11%, Valeriana pyrenaica 11%, Populus nigra 11%, Veronica montana 11%, Lamium maculatum 11%, Calystegia sepium 11%, Poa trivialis 11%, Humulus lupulus 10%, Helleborus viridis 10%, Stellaria holostea 10%, Mentha aquatica 10%, Glechoma hederacea 10%, Viola palustris 10%, Ulmus minor 10%, Ruscus aculeatus 10%, Castanea sativa 9%, Jacobaea aquatica 9%, Primula elatior 9%, Buxus sempervirens 9%, Rosa canina aggr. 9%, Viburnum opulus 9%, Cardamine raphanifolia 9%, Prunus spinosa 9%, Viburnum lantana 9%, Cardamine flexuosa 9%, Vicia sepium 9%, Ulmus glabra 9%, Lonicera xylosteum 9%, Galium broterianum 9%, Ficaria verna 9%, Erica arborea 8%, Holcus mollis 8%, Anthriscus sylvestris 8%, Myosotis martini 8%, Lapsana communis 8%, Brachypodium pinnatum 8%, Symphytum tuberosum 7%, Dryopteris borreri 7%, Crocosmia x crocosmiiflora 7%, Saxifraga spathularis 7%, Betula celtiberica 7%, Agrostis capillaris 7%, Ranunculus acris 6%, Dryopteris dilatata 6%, Cardamine hirsuta 6%, Lysimachia vulgaris 6%, Iris foetidissima 6%, Saponaria officinalis 6%, Salix purpurea 6%, Carex laevigata 6%, Bryonia dioica 6%, Solidago virgaurea 6%, Knautia legionensis aggr. 6%, Vitis vinifera 6%, Ilex aquifolium 6%, Veronica chamaedrys 6%, Mentha suaveolens 6%, Mercurialis perennis 6%, Chrysosplenium oppositifolium 6%, Galium palustre 6%, Digitalis purpurea 5%, Galeopsis tetrahit 5%, Rosa arvensis 5%, Juncus effusus 5%, Rhamnus cathartica 5%, Pentaglottis sempervirens 5%, Rumex acetosa 5%, Prunus avium 5%, Pimpinella major 5%, Cirsium palustre 5%, Fragaria vesca 5%, Epilobium obscurum 5%, Holcus lanatus 5%

Phytosociology

  • Galio broteriani-Alnetum glutinosae
  • Hyperico androsaemi-Alnetum glutinosae
  • Hyperico androsaemi-Salicetum atrocinereae
  • Scophulario scorodoniae-Alnetum glutinosae
  • Senecioni bayonnensis-Alnetum glutinosae
  • Stegnogrammo pozoi-Alnetum glutinosae
  • Valeriano pyrenaicae-Alnetum glutinosae

Relations with other habitat types

Even if the proximity of the river imposes a permanent waterlogging in their deep layers, soils are often rich in coarse blocks (those first deposited by floods, near the permanent riverbed) and tend to be less heavy than those supporting T111. Therefore, drainage can be significant at low water, enabling the survival of a rich contingent of nemoral herbs benefitting from the disturbance regime created by regular floods which, by generating a patchy distribution of light and nutrients, prevents outcompetition by clonal species (as often happens in T111 and T151) and facilitates the dispersal of asexual propagules along the river banks. In low- and mid-elevation headwaters, whose catchment areas are necessarily small and a deeper drying-up in summer is commonplace, less specialised communities prevail (namely T1D1 on acid, poorer substrates, and T1E1 elsewhere, with S912 in the highlands).

Regional distribution

In order to prevent fluvial erosion, traditional land-management preserved narrow fringes of these forests, a trend amplified by more recent policies that explains their relative abundance. Unfortunately, their conservation status is often poor, partly as a consequence of their particular vulnerability to invasive species, explained by how their intrinsic disturbance regime, their humid and fertile soils and their lineal continuous distribution facilitate the proliferation of species dispersed by fragmentation, popular in gardening for that very reason.

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

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Citation: IBEROATLANTICA – Flora and Habitats of the Cantabrian Mixed Forests ecoregion.
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