Madeiran xerophytic scrub

Xerophytic nano- to microphanerophytic communities, sclerophyllous, succulent (or having other kinds of morphological adaptations to drought) of the lower altitudes in Madeira island. These include: (1) communities dominated by paleomediterranean shrubs or small trees: Olea, Maytenus, Chamaemeles: with hard leathery leaves (Mayteno-Oleion maderensis) that stand for mature zonal vegetation of permanent character in thin cambisols of rocky steep cliffs in the infra to thermomediterranean (sometimes infra-thermotemperate in the north face) semi-arid to dry belts. In their upper altitude limit some of these communities (Myrtus communis with Hypericum canariense) may be the natural edge or first seral stage of the Apollonias barbujana thermomediterranean sub-humid forests (included in G2.3 type, Visneo-Apollonion); (2) Thick succulent stemmed Euphorbia piscatoria summer-deciduous communities that are seral stages of the former (i.e. i)), permanent communities or pioneer in rocky leptosols, for instance in low altitude abandoned fields; (3) inframediterranean/temperate sub-humid half-sclerophyllous tall shrub communities of the northern face, transitional from xerophytic to mesophytic heathlands (Syderoxylon mirmulans community: Visneo-Apollonion barbujanae); (4) chamaephytic communities of neomediterranean shrubs, having rolled, hairy, waxy or resinous leaves, or exhibiting leaflessness the most part of the year, that are seral stages of the zonal sclerophyllous types, pioneer or sometimes permanent in semiarid steep rocky cliffs (Soncho-Artemision argenteae); (5) xerophytic succulent low-scrub semi-halonitrophyllous under some influence of salt winds and nitrates from bird dropping deposition of Calendula maderensis (Argyranthemo suculenti-Calendulion maderensis).

The two later variants (iv) and v)) could be together separated as a subtype within the F8.2 type, but since they are found usually in mosaic with the other variants without regional or landscape separation, this is superfluous for habitat typology purposes. The main contacts of the F8.2 type are with Grenovio-Aeonietea succulent rock wall vegetation (Sinapidendro-Aeonion glutinosi, H3.3 Macaronesian inland cliffs). Where the semi-halonitrophyllous scrubs are not found in mosaic with other communities of H8.2, they can be considered as type H6.8a Mediterranean halo-nitrophilous scrubs.

Indicators of good quality:

In general, dominant plants and the bioindicator set should be identified at its maximum mumber as a measure of ecological integrity (see characteristic species, flora, vascular plants). As to the sclerophyllous or half-sclerophyllous variants (i and ii) that are successionaly replaced by the ii) or iv) variants by disturbance, the more elements of Euphorbia piscatoria community (E. piscatoria, Echium nervosum or Globularia salicina) or any of the iv) variant (Carlina salicifolia, Artemisia argentea, Erysimum maderense, Genista tenera, Helichrysum monizii, Micromeria varia subsp. thymoides and Phagnalon lowei), the more the sclerophyllous i) variant is formally close to collapse. Nevertheless, since this happens from natural or expected human-induced causes and the seral stages are themselves floristically valuable, some care should be taken in evaluating the whole of the mosaic of variants within the F8.2 type for conservation purposes. The same reasoning applies to the v) variant (indicators: Argyranthemum pinnatifidum subsp. suculentum and Calendula maderensis). Reliable indicators of degradation are the increase in dominance of tall-grass stages: Hyparrhenia sinaica (=H. hirta auct mad.), Cenchrus ciliaris, Dactylis glomerata subsp. hylodes or any kind of disturbance-prone or nitrophyllous vegetation.

Note on delimitation of habitat type

We restrict the habitat concept to the xerophytic hard-leaved/succulent in low-altitude (infra-thermomediterranean) semi-arid to dry nano-microphanerophytic shrub communities (Rhamno-Oleetea cerasiformis) and also including xerophytic low-scrub in high sea cliffs under the moderate influence of salt winds and nitrates from sea bird droppings (semi-halonitrophyllous communities: Pegano-Salsoletea). Due to its transitional character between xerophytic high scrub (Mayteno-Oleion) and driest /hottest laurel forest (Visneo-Apollonion), the Sideroxylon mirmulans tall-scrub is also included in the type. Chamaephytic communities of salt-rich soil in sea-cliffs under strong influence of salt spray close to wave breaks are not included (Helichrysio obconico-devium) and belong to habitat type B3.1-3c – Macaronesian rocky sea cliffs and shores. Also, chamaephytic vegetation dominated by succulent crassulaceae (Aeonium sp. pl.) is excluded and considered in H3.3.- Macaronesian inland cliffs.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats