Leyendas

The terrestrial biocoenoses of the Maltese Islands may be grouped in three categories:

?? Major communities that are part of the successional sequence towards the climatic climax.

?? Minor communities which are either specialised to occupy particular habitats, or occupy habitats that are rare in the islands, or are relics from a previous ecological regime, now surviving in a few refugia.

?? Biocoenoses that owe their existence to anthropic activities.

Descriptions of Maltese terrestrial biocoenoses are based mainly on vegetation. Figs 2.1 to 2.7 show the distribution and location of the various habitat types and biocoenoses described below.

3.2.1.1 Biocoenoses That Are Part Of The Successional Sequence

? Woodland

It is thought that before man colonised the Maltese Islands, large areas were covered with Mediterranean Sclerophyll Forest, which is the highest type of vegetation that can develop in the Mediterranean climatic regime. In the central Mediterranean this forest is characterised by Holm Oak (Quercus ilex) and Aleppo Pine (Pinus halepensis) with an undergrowth of smaller trees, shrubs and climbers. The early settlers cut the trees for their wood and to clear the land for agriculture and buildings. Additionally, these colonisers introduced sheep and goats to the islands, whose grazing causes some damage to mature trees but more importantly prevents them from regenerating. In the Maltese Islands, the native forest is all but extinct and only remnants remain at four localities (Ballut tal-Wardija, Ballut ta' l-Imgiebah, Ta' Baldu/Wied Hazrun, and Il-Bosk near Buskett) all on the island of Malta. These forest remnants take the form of small copses of Holm Oak where the total number of trees is often less than thirty. Some of these trees are estimated to be between 500 and 900 years old.

? Maquis

Maquis is a more or less dense, mostly evergreen shrub community where the individual shrubs reach a height of between 1m and 3m. In Malta, a semi -natural maquis develops in relatively inaccessible sites such as the sides of steep valleys and at the foot of escarpments and rdum, while a secondary maquis develops round trees, mainly olives and carobs, planted by man.

The local maquis is characterised by a number of small shrubs principally Carob (Ceratonia siliqua), Olive (Olea europaea), Lentisk (Pistacia lentiscus), Mediterranean Buckthorn (Rhamnus alaternus), Hawthorns (Crataegus spp.), Bay Laurel (Laurus nobilis) and others.

Various subtypes of maquis occur, some of which (e.g. those based upon Myrtus communis, Spartium

junceum and Tetraclinis articulata) are very rare and threatened.

Garigue (or garrigue) is a community of low (less than 1m) scattered, often spiny and aromatic shrubs with a herbaceous undergrowth. This is the most common natural vegetation type present in Malta. Some garigue communities are natural edaphic climaxes, others result from degradation of forest and maquis. Garigues are typical of rocky ground, particularly karstland, and are characterised by such species as Mediterranean Thyme (Thymus capitatus), Yellow Kidney-vetch (Anthyllis hermanniae), Tree Germander (Teucrium fruticans), Mediterranean Heath (Erica multiflora ), Tree Spurge (Euphorbia dendroides), Olive-Leaved Bindweed (Convolvulus oleifolius) and the endemic Maltese Spurge (Euphorbia melitensis), accompanied by numerous geophytes (herbs with perennating buds below soil level) and therophytes (herbs which survive the unfavourable season as seeds).

Many subtypes of garigue exist, including Erica garigue (dominated by the Mediterranean Heath Erica

multiflora), Thyme garigue (dominated by Mediterranean Thyme Thymus capitatus), Anthyllis garigue

(dominatd by Shrubby Kidney-vetch (Anthyllis hermanniae) and, less commonly, Euphorbia melitensis garigue (dominated by the endemic Maltese Spurge Euphorbia melitensis). Other types (for example, Tree- spurge garigue) and mixed garigues also occur (for example, various combinations of Erica/Thymus/Anthyllis/Euphorbia garigues, and even all four together).

It is useful to distinguish between high and low garigues since there are marked structural difference between the two. Low garigues are characterised by low-growing bushes (less that 0.5m high) while high garigues are dominated by large bushes of up to 1m height. Anthyllis garigue can occur as both low and high varieties while an important type of high garigue is that dominated by Tree-spurge (Euphorbia dendroides) which normally occurs on steep rocky ground.

? Steppic grassland

This is a treeless grassland dominated by grasses, umbellifers, thistles and geophytes. Steppic grasslands are widespread and result from degradation of the maquis and garigue, mainly due to grazing, but also in response to other factors. Some steppic communities are, however, climactic or semi-climactic, for example, those dominated by Esparto Grass (Lygeum spartum) which develop on clay slopes. The more degraded steppes are characterised by Common Awn-grass (Stipa capensis), Aegilops (Aegilops geniculata) and a variety of thistles (e.g. Clustered Carline Thistle Carlina involucrata, Horse Thistle Notobasis syriaca, Mediterranean Thistle Galactites tomentosa) and geophytes (e.g. Asphodel Asphodelus aestivus, Seaside Squill Urginea

pancration) and Sicilain Squill (Scilla sicula). Other steppic communities may also develop on abandoned

agricultural land.

3.2.1.2 Specialised Biocoenoses

? Coastal communities

Saline marshlands

Saline marshlands form an interface between the marine, freshwater and terrestrial environments. Maltese coastal marshes are characterised by a muddy substratum on which a pool of brackish water collects in the wet season. During the dry season this water becomes progressively more brackish until it finally disappears completely, leaving the marsh dry until the following wet season. Because of these harsh environmental conditions, saline marshlands support a highly specialised biota that is only found in this type of habitat. Although several species are common to all local marshlands, yet each site has its own peculiar habitat characteristics and suite of species.

Transitional coastal wetlands

Some coastal wetlands appear to be transitional between freshwater wetlands and saline marshlands in the sense that the biotic assemblages they support consist of species typical of both freshwater and saline habitats. Such wetlands have been termed 'transitional coastal wetlands'. Such wetlands arise when rainwater collects in depressions close to the sea. Under appropriate conditions, these pools become colonised by species typical of freshwater and which have some degree of tolerance to maritime influence. During the dry period, the only water arriving in these depressions is seawater carried by wind and wave

action; conditions therefore favour brackish water species. The same habitat therefore supports different suites of species at different periods of the annual cycle. Some long-lived and tolerant brackish water species (mainly plants) may persist throughout the freshwater phase, giving rise to the specific biota which characterise such wetlands. The most important of such wetlands are Ghadira s-Safra, on the northeast coast of Malta between Maghtab and Ghallis, the Qammieh pools, and Il-Qattara on Gozo.

Sand dunes

Many local sandy beaches were backed by dune systems, but at present only very few still persist and even these have been much degraded due mainly to human activities connected with beach development for touristic purposes and with recreational use. Sand dune ecosystems are thus amongst the rarest and most threatened of local ecosystems. . Local dunes are dominated by the dune grasses Elytrigia juncea and

Sporobolus pungens, and, until recently, also by Southern Marram Grass (Ammophila littoralis) which has

now been totally extirpated.

Case study: Ramla l-Hamra dunes, Gozo

Due to its extent, species richness and ecosystem stability, this is the most important dune ecosystem of the Maltese Islands and in spite of the fact that it has suffered much disturbance in recent years, it still includes most of the recorded dune species, including a number found only here and nowhere else in the Maltese Islands.

The main sand binders at Ramla are the Sand Couch and the Dropwort grass. These are accompanied by other typical sand dune species such as the Spiny Echinophora (Echinophora spinosa - RDB 25: endangered) which occurs only in one other locality in Malta, the Sea Daffodil (Pancratium maritimum - RDB 40: vulnerable), the Sea Holly (Eryngium maritimum - RDB 25: vulnerable), and the Sea Spurge (Euphorbia paralias - RDB 22: endangered), the Coast Spurge (Euphorbia terracina - RDB 22: vulnerable) and the Purple Spurge (Euphorbia peplis - RDB 22: endangered), which is now restricted to Ramla Bay. Also common are the Sea Medick (Medicago marina - RDB 19: vulnerable), Sea Kale (Cakile maritima ) and the annual Sand Fern Grass (Cutandia maritima - RDB 43: rare). Rarer species include the Sand Restharrow (Ononis variegata - RDB 19: endangered) which occurs only in this locality, and the Sand Carrot (Pseudorlaya pumila - RDB 25: endangered). An unusual and very rare sand-dwelling mushroom,

Montagnites arenaria (RDB 54: endangered) is also known only from this locality. The dune is traversed

by a belt of the African Tamarisk (Tamarix africana - RDB 23: rare). Clumps of Tamarisk also skirt the easternmost part of the bay. In this area, isolated shrubs of the Chaste Tree (Vitex agnus-castus - RDB 29: rare) also occur. This shrub, having habitat requirements similar to those of the Tamarisk, occurs mainly in Gozo, but is very rare in Malta.

Among the more important animal species one finds: two endemic collembolans, Odontellina sexoculata and Mesophorus schembrii, to date, both known only from the Ramla dunes; the subterranean cricket

Brachytripes megacephalus (RDB 91: vulnerable) known only from the dunes at Ramla and Ghadira

(Malta); the histerid beetles Hypocaccus dimidatus (RDB 110: restricted) for which Ramla is one of the only three sites and Xenonychus sp. and Hypocaccus sp. until now only recorded from Ramla; the anthicid beetle Anthicius fenestratus for which Ramla is the only known locality; at least four different species of carabid beetles all of which are only known from Ramla; the ants Trachymesopus darwini, known only from this area and Leptothorax sp. known from only one other site, also in Gozo; the sphecid wasps

Prionyx lividocinctus, Sphex pruinosus, Philanthus raptor siculus (RDB 93: vulnerable), Bembix oculata

and Bembecinus tridens (RDB 94: vulnerable), all species with very restricted distributions in the Maltese Islands; the halictid bee Psuedoapis unidentata which has a restricted distribution in the Maltese Islands; the amphipod Talitrus saltator and the burrowing isopod Tylos latreilli both of which have a restricted distribution in the Maltese Islands.

Note: RDB refers to the Red Data Book for the Maltese Islands (1989), and the number refers to the

Maritime fringe

On gently sloping rocky shores, halophytic vegetation grows in isolated patches in the shallow saline soil which accumulates in pockets in the rock. The species present are typical of this type of habitat and mainly form part of the Mediterranean vegetational community called the Crithmo-Limonietum. In the Maltese variants of this biocoenosis, several endemic plants are found only in this community type and others also occurs, although not exclusively on low-lying maritime rock.

? Rupestral communities

These grow on sheer rock faces (sisien) and in cliff/scree environments (rdum). The south, southwest and west coasts of the island of Malta consist of vertical cliffs rising from the sea to heights of c.70-130m. In the Dingli Cliffs area, these cliffs give way to a steeply sloping substratum. This sloping ground is terraced and partly under cultivation. Further inland there is a second tier of vertical cliffs. The south and southwest coasts of Gozo consist of sea-cliffs similar to those of southern Malta. Because of the shelter they provide and their relative inaccessibility, both the sea-cliffs, and the second tier of inland cliffs with the boulder screes which form beneath them, provide important refuges for many species of Maltese flora and fauna, including many endemics.

The fauna of coastal cliffs includes some of the rarest of Maltese animals; for example, the endemic Maltese Door-snail (Lampedusa melitensis) occupies a very precarious habitat of a few tens of square metres only on the southwest cliffs of mainland Malta, while two other rare endemic snails are found in a few cliff-side localities only. Cliff-side communities are dominated by shrubs and are especially significant due to the presence of a large number of endemic plant taxa including two (Palaeocyanus crassifolius and

Cremnophyton lanfrancoi) belonging to monotypic genera.

? Caves

In spite of being made up almost exclusively of limestone, the Maltese Islands have surprisingly few known deep caves (although unexplored examples may occur). Maltese caves are inhabited by organisms which are adapted to live in such habitats and therefore have a very restricted distribution. The best known cave-dwellers are bats but there are many other species, particularly invertebrates. Moreover, a number of these species are endemic to the Maltese Islands and therefore of great scientific interest. They are also highly vulnerable, both because of the limited habitat available and because of their poor dispersive ability. Additionally, many caves have deposits of Quaternary age (for example, Ghar Dalam), study of which is important for an understanding of the islands' palaeoenvironment and biogeography. One cave, that at Harq il-Hamiem near Pembroke is unique in that it houses a deep pool of freshwater, the only such body known in the Maltese Islands.

3.2.1.3 Anthropogenic Biocoenoses

? Communities of disturbed ground

Given the islands' high human population and its considerable land use, these biocoenoses have a large coverage. They are dominated by a variety of plant species, many of which are aliens. Sub-types occur in abandoned fields, along roadsides and in disturbed seaside habitats.

? Afforestation

Most of Il-Buskett was originally planted by man but is now self-regenerating and has the character of the natural climax community and may be described as a semi-natural woodland. Here the wood is dominated by Aleppo Pine (Pinus halepensis) with various other trees being sub-dominant (e.g. Olive, Carob, Holm Oak) and there is an extensive undergrowth of shrubs (e.g. Lentisk, Mediterranean Buckthorn and Hawthorns), herbs and climbers. This semi -natural wood is very important since it represents the only full woodland ecosystem on the islands and consequently harbours a large number of woodland plants and animals which, because of the lack of suitable habitats in Malta, are locally very rare. Particularly important

woodland species are fungi that are symbiotic with trees, insects which feed, breed or live in trees and dead wood, and leaf-litter inhabiting invertebrates.

Many other wooded areas exist in the islands, however, all are man-made (e.g. public/private gardens, afforestation sites, orchards, etc.) and do not possess the character of the native climax forest ecosystem nor are they self-maintaining and self-regenerating as is Il-Buskett, and therefore do not qualify as semi-natural woodlands.