October 2023 Notes

The Mediterranean region is warming 20% faster than the world as a whole, raising concerns about the impacts that climate change and other environmental upheaval will have on ecosystems, agriculture and the region’s 542 million people.

Heat waves, drought, extreme weather and sea-level rise are among the impacts that the region can expect to see continue through the end of the century, and failing to stop emissions of carbon dioxide and other greenhouse gases could make these issues worse.

Charting a course that both mitigates climate change and bolsters adaptation to its effects is further complicated by the Mediterranean’s mix of countries, cultures and socioeconomics, leading to wide gaps in vulnerability in the region.

• In the parts of the Mediterranean that rely on rain-fed crops, the more concentrated and intense winter rainfalls anticipated by climate forecasts are likely to leech soils of key nutrients.
• Soil biodiversity, which includes everything from invisible microbes to insects and earthworms, is waning in the Mediterranean and could be pushing a critical food-producing region toward utter collapse.
• The loss of soil moisture could lead to a self-perpetuating cycle of drought. With less water evaporation as temperatures continue to bake the soil, there’s less rain to replenish that moisture, leading in turn to more drought.
• One way to adapt would be the introduction of drought-adapted crop varieties. That transition has already begun in parts of France’s wine industry.
• Irrigation may provide stopgap relief by bringing enough water to coax a few more harvests from drier soil. But the longer-term impacts could lead to a broader drawdown of the region’s water resources, and to a buildup of salt in soils — an effect that wrecked ancient Mesopotamian civilizations.

Mediterranean climate

The Mediterranean has a subtropical climate with hot summers and mild winters. Precipitation is concentrated in the winter.

The subtropics fall outside of the tropics of Cancer (in the northern hemisphere) and Capricorn (southern hemisphere).

The tropics mark the most northerly and southerly (subsolar) points.

The Tropic of Cancer (or the Northern Tropic) is the circle of latitude that contains the subsolar point at the June (or northern) solstice when the Northern Hemisphere is tilted toward the Sun to its maximum extent.

The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice when the Southern Hemisphere is tilted toward the Sun to its maximum extent.

On the June solstice the Tropic of Cancer receives more sunlight than anywhere else on earth.

On the December solstice the Tropic of Capricorn receives more sunlight than anywhere else on earth.

Mediterranean climate has a Köppen climate classification of Csa/Csb (Temperate/Semi-arid/Hot summer or Warm summer).

Unimagined

My thoughts break in two directions - towards despondency (that my archetypal landscape is artificial, a consequence of millenia of human disruption) - and towards hope (that this counterfeit is a savage-benign successor to the original).

It is perfect and imperfect, a human place, made by us for us; an example of what is best for us and a reflection of what is best in us.

We need to turn things around; not congratulate ourselves for small sacrifices. Instead we must describe how we should behave, and to reveal every step backwards for the failure that it is.

We do not like to say must; but we must. We must be clear-eyed in our observations and we must be categorical in our demands (both those we make of ourselves and those we make of others).

Mediterranean climate on a retrograde rotating Earth

Wetter and stormier.

Did human intervention lead to a Lost Eden, or was it a benign influence?

• One cannot understand the components and dynamics of current biodiversity in the Mediterranean without taking into account the history of human-induced changes.
• The various systems of land use and resource management that provided a framework for the blossoming of Mediterranean civilizations also had profound consequences on the distribution and dynamics of species, communities, and landscapes.
• The processes of domestication of plant and animal species, which first occurred in the eastern Mediterranean area some 10,000 years ago, contributed to the increase of certain components of biodiversity at several spatial scales. Positive and negative feedback cycles between cultural practices and natural systems at the local and regional levels have kept ecosystems robust and resilient.
• Assuming that human action can, to a certain extent, be considered a large-scale surrogate for natural sources of ecosystem disturbance, such patterns give support to the diversity-disturbance hypothesis—specifically, intermediate levels of disturbance have promoted biological diversity.
• Intraspecific adaptive variation increased as a result of human-induced habitat changes over millennia, resulting in bursts of differentiation during the later Holocene of local ecotypes and gene pools of domesticated and wild plant and animal species, with region-specific characters fitting them to local climate and environmental conditions.

It is concluded that a high degree of resilience of Mediterranean ecosystems resulted in a dynamic coexistence of human and natural living systems, which in some cases provided stability, while fostering diversity and productivity.

Olive oil

Papers

The SHD olive orchard system may change the soil nematode community associated with olive orchards, especially concerning plant-parasitic nematodes.

The negative effects were mainly evident in stressed environments due to the dry summers and the lowest TOC content. Nevertheless, using a conservative and sustainable soil management method may maintain or improve the soil nematode community functionality and prevent the plant-parasitic nematode increase.

Olive (Olea europaea L.) is a widely spread tree species in the Mediterranean.

In the last decades, olive farming has known major management changes with high economic and environmental impacts. The fast track expansion of this modern olive farming in recent years casts doubts on the sustainability of such important tree plantations across the Mediterranean.

Main olive grove types

• Low density LD (100 trees ha-1)
• Medium density MD (200 trees ha-1)
• High density HD (400 trees ha-1)
• Super high density SHD (1650 trees ha-1)

10.8 Mha of olive trees are cultivated worldwide, 95% of which are in the Mediterranean region.

They help preserve natural resources by protecting the soil and sequestering carbon.

Agricultural management of olive trees has the potential to increase the accumulation of soil organic matter.

The potential of olive tree plantations to store stable organic carbon acting as CO2 sinks has been confirmed under some soil conservation practices.

Olive trees are drought-tolerant but water affects vegetative growth.

Olive trees are also limited by frost and high temperatures, and to a lesser extent by low soil fertility.

Trees in SHD orchards are usually irrigated, fertilized and trained to be suitable for mechanical harvesting and pruning, thus increasing productivity and profitability.

Paper based on studying trials on OliveCan, a process-based model of olive trees.

The rest of the paper is unavailable without payment…

Deficit Irrigation

Water

Traditionally, olive trees have been grown in the region surrounding the Mediterranean, mainly as a rainfed crop with low productivity given the typical dry environment of this region.

In recent years, the expansion of olive oil and table olive production has been achieved through both an increase in the planted area and through intensification within and beyond the Mediterranean countries by increasing the orchards’ density and via the introduction of irrigation.

In the last two decades, HD and SHD orchards, known as hedgerow olive orchards, have been developed to further reduce harvesting costs using over-the-row harvesting machines.

Current water scarcity in traditional olive-growing regions, like Alentejo, along with the expected increase in heat waves and droughts caused by climate change [16,19,20], imply an urgent need to reduce the use of water for irrigation of crops in these regions and to adopt measures to avoid the degradation of soil resources and biodiversity.

The Olive Orchard Mosaic

• Management of cover crops is conducted by tillage or total herbicide coverage. Grain crops were traditionally grown within olives as primary sources of farmers' income. Soil erosion can be dramatic and temperature of the soil's top layer is high in the summer (over 40 °C). Although olive is a well-adapted species to drought conditions, the soil's exposure to direct sun and the lack of canopy shade over the tree root zone leads to water and heat stress, and can induce summer dormancy in the trees.
• Farmers use few fertilizers and apply a reduced number of chemical pest and disease treatments in the olive groves. They are pruned every four years by chainsaw, and the pruning residue is generally burned. The alternate bearing is very strong, with a sparse yield in the year following pruning. Since these orchards are rainfed, the biodiversity of species is sometimes low due to the lack of water and cover crops.
• Traditionally, the harvest is performed by hand with wood sticks, although nowadays, some growers use portable backpack shakers with or without nets covering the floor.
• Net production of these olive ecosystems is less than 3t ha-1 of fruits

• The most common olive orchards in the Mediterranean area are those with MD (e.g. in lime soils of the southern parts of Portugal or Spain).
• They are rainfed or little irrigated, and the soil is kept weed-free by tillage or by partial (in the rows) or total herbicide application.
• Many have spontaneous cover plants, mainly in the interrows, which are used to some extent as grazing lands. In this case, animal manure provides some nutrient recycling for the ecosystem and complements the annual fertilization.
• The pruning is carried out in alternate years and is less intense than in the traditional orchards. The pruning residue is often burned.
• The sun exposure of the soil is lower due to the improved tree shade, resulting in better development of resident herbaceous vegetation that increases insect populations, improving biodiversity, and provides more protection against soil erosion than in the TD systems.
• The harvest is carried out by tree shaking using floor nets or wraps around the trees as collecting systems.
• These orchards have been upgraded over time by increasing plant density and providing better irrigation. This agricultural system is undergoing a fast transition to a higher-density system.
• Net production of these olive ecosystems is 3-6t ha-1 of fruits

• The success of the higher-density olive agricultural systems is based on water availability.
• The olive tree is an evergreen species with a remarkable water control process that manages water losses, requiring less water in the summer than in the remaining period of the year.
• Nevertheless, in a region with 562 mm year-1 of average rainfall [44], 250 mm to 500 mm year-1 of supplemental irrigation water are the necessary values for the trees to achieve their maximum productivity.
• This demand is lower when compared to the 500–800 mm year-1 required by other perennial species. Under these conditions, higher densities lead to increased productivity.
• For soil management, the soil is normally covered with spontaneous or sowed herbaceous vegetation to minimize soil erosion. The sowed cover species could be Fabaceae sp., like Medicago sativa, Vicia sp. or Trifolium spp., which are quite important nitrogen recyclers.
• Spontaneous or sowed cover crops are also important refuges for beneficial insects or pollinators, which improve the general biodiversity of HD and SHD orchards.
• Inter-row weed management is usually carried out by shredding 3 to 5 times a year to keep the weeds below 0.5 m in height. The shredding also recycles the pruning residues left in the topsoil of these orchards.
• One advantage of HD and SHD olive orchards is the soil temperature. In the same location, the temperature of the topsoil in the summer, measured with a FLIR (Forward Looking InfraRed) device, was about 20 °C lower at the top of the cover grass when compared to bare topsoil.
• Harvests in HD and SHD olive orchards require tractor trunk shakers with wraps around the tree collectors or over-the-row self-propelled machines. The latter can harvest up to one hectare per 1 h (12–22 t of fruits). As the fruits are never in contact with the ground, they are quite suitable for virgin or extra-virgin oil production.
• In Portugal, the harvest is restricted to the period from sunrise to sunset in order to prevent involuntary bird losses, since these animals often use olive trees as refuges overnight.

Water Management

• Crop water requirements (CWR) are defined as the amounts of water needed to replace the water lost through evapotranspiration by a disease-free crop growing in large fields under no limitations regarding soil conditions, including soil water and fertility, and achieving full production potential in the given growing environment.
• In the case of irrigated crops, the concept of irrigation water requirement (IWR) must be considered. The IWR is the amount of water that is required to be applied to a crop to fully satisfy its specific crop water requirement whenever rainfall, soil water storage, and groundwater contributions are insufficient.
• Olive trees' water requirements are a function of cultivar characteristics, management, and environmental demands. Olive trees withstand long periods of drought and can survive in very sparse plantings, even in climates with very low annual rainfall: values of 150–200-250mm year-1.
• However, for economic production, much higher precipitation or irrigation are required: an average annual precipitation or irrigation 600-950mm year-1, in soils with good water-holding capacity, is needed for successful cultivation.
• Water needs throughout the year (budding, flowering) and at different points in the life cycle (young, old) of the tree.
• Vegetative development, yield, and fruit quality are affected by water availability and controlled by irrigation.
• In Sustained Deficit Irrigation (SDI), the irrigation water used at any moment during the season is below the crop evapotranspiration demand. This is based on the idea of allotting the water deficit uniformly over the entire growing season. Thereby, the water deficit increases progressively as the season advances due to a combination of the uniform application of a reduced amount of water and the depletion of available soil water. This allows water stress to develop slowly and for the plants to adapt to the water deficits when the soil presents significant water storage capacity.
• Times when water needs of the tree must be met
  • From the last stages of floral development to full bloom, normally in mid-April, when water stress can affect flower fertilization.
  • At the end of the first stage of fruit development, normally in June, when water stress causes reductions in fruit size.
  • After the midsummer period, normally from late August to mid-September, when a marked increase in oil accumulation occurs.
• Net production of HD ecosystems is 6-12t ha-1 of fruits
• Net production of SHD ecosystems is 12-22t ha-1 of fruits

Agroecological Practices

• Semi-arid Mediterranean regions are among the most productive areas in the world [118]. However, the soil has a low carbon content and is susceptible to degradation.
• Tillage increases CO2 emission at the expense of organic matter, contributing to global climate change.
• In irrigated olive orchards such as HD or SHD, it is possible for non-tillage practices to be implemented.
• Non-tillage system avoids the propagation of soil-borne diseases such as Verticillium dahliae, the main soil-borne disease for this perennial species worldwide. Preventing soil disturbance and minimizing the contact of fungus mycelia from root to root decreases the infection rate.
• Herbaceous vegetation can have a positive impact on erosion reduction, especially in orchards planted on slopes, contributing to carbon and nitrogen sequestration and acting as a nutrient buffer.
• Herbaceous cover also provides shelter and food for many beneficial and pollinator insects.
• Vectors for the bacteria Xylella fastidiosa could also live and feed on orchard weeds.
• The generalized application of herbicides dramatically decreases the number of species, plants, animals, and other living organisms present in an olive orchard ecosystem. For instance, the abundance and diversity of nematodes is lower in bare soils treated with herbicides, and is intermediate in non-herbicide areas. Normally, tillage reduces the number of arthropod species.
• The use of herbicides in the total area of an orchard increases the rainwater runoff and contributes to faster soil erosion and lower nutrient availability. The use of herbicides sprayed in stripes, as in rows of trees, seems to have a lower impact on soil erosion.
• Weed species present on an olive orchard’s floor, like Conyza sp., present significant challenges nowadays, as they are not effectively controlled by glyphosate spray treatment. The eventual withdrawal of this herbicide will lead to the implementation of other non-herbicide solutions for orchard floor management.

• In HD and SHD olive orchards, the pruning wood is normally shredded together with the cover weeds, and its nutrients are slowly released over time. This is a way to recycle nutrients and organic matter. The presence of chopped wood pieces and weed residues on the orchard floor has four main benefits.
  • Decreases the rainwater runoff speed and helps to prevent erosion.
  • Promotes the rainwater infiltration rate, which is quite important in the case of heavy rain events.
  • Improves machines’ traction, preventing tractor or harvesters’ wheels from sliding.
  • Crossed chopped wood pieces act as a physical barrier over the floor, preventing soil compaction.
  • High tree density has an impact on biodiversity e.g. bird population reduction. Heavier machinery and increased fertilizer, pesticide, and water usage are also said to negatively impact ecosystems’ biodiversity. The generalized adoption of drip irrigation increases the Verticillium dahliae in the soil. The inoculum density in all experiments was higher in wet than in dry areas, and after 4 months of watering, the soil pathogen population increased considerably in both wet and dry areas. The inoculum density remained higher in the wet soil.

• The increase in tree densities, the introduction of irrigation, and the development of new training systems to facilitate mechanical pruning and harvesting have contributed significantly to the intensification and expansion of olive oil and table olive production. In recent years, concerns about the potential detrimental impacts of high-density olive cultivation have emerged, bringing into question the trade-offs between production benefits and environmental costs.
• Water-saving irrigation practices and more sustainable soil management or other agroecological practices can mitigate the negative effects of climate change and improve the ecosystem services of dense irrigated olive cultivation.

Cradle to grave study on 6 production methods

The above is worth following up if I want to go deeper on this subject e.g. bottling contributes most to emissions.

Considers e.g. use of chemicals during oil production and polluted wastewater, and water availability.

Industry articles

Commercial cultivars

The Mediterranean - naturalised home of the olive tree

The Mediterranean Basin is the cradle of civilisation and has thus been heavily influenced by man over the last 6,000 years or so.

Devoid of man’s intervention the Mediterranean Basin would typically be a climax of evergreen sclerophyllous forest dominated by evergreen oaks or pines. Below this dominant tree layer would be found a mixed evergreen sclerophyllous shrub layer and below this a perennial herbaceous layer.

Around the Mediterranean due to man’s interactions this primaeval climax community is now fairly rare and it can be found only in isolated patches in the valleys and hills.

The rare original Mediterranean evergreen forests now represent only 1.8% of world’s forested areas.

Climax communities are stable, but once the forest trees are cleared for whatever reason rapid degeneration follows (though it may be reversed).

Evergreen forest -- Maquis -- Garrigue -- Steppe

Evergreen Forest

The dominant evergreen forest in the Western Mediterranean is Holm Oak (Quercus ilex), which grows on all the Mediterranean soils and occasionally forms dense forests, but is more commonly seen in scattered groups now.

In the Eastern Mediterranean the Kermes Oak (Quercus coccifera) replaces the Holm Oak, but there it does not form forests except in Crete and the rest of the Peloponnese.

These forests are rarely seen in their climax state: dense dark woodlands up to 15 metres high, with an understory shrub layer of:

• Strawberry Trees (Arbutus unedo)
• Green Olive Tree (Phillyrea angustifolia)
• Mock Privet (Phillyrea latifolia)
• Buckthorn (Rhamnus alaternus)
• Laurustinus (Viburnum tinus)
• Climbers (Clematis flammula, Clematis cirrhosa, Clematis viticella)
• Honeysuckle (Lonicera spp)
• Sarsaparille (Smilax aspera)
• Black Bryony (Tamus communis)

Typically, in their climax state there is little light reaching the ground if these forests are dense, and so there is no herb layer, but they are sparse now and it is more usual to see scattered trees with a well-developed Maquis vegetation below.

Cork Oak (Quercus suber) forests can be found in the Central and Western Mediterranean, as well as Portugal, but only on siliceous soils in warmer and maritime zones. The Cork Oak forests have been carefully managed by man for decades and so are typically more open occasionally with a Maquis layer beneath.

The Aleppo Pine (Pinus halepensis) forests are dominant in the hotter and drier Mediterranean zones, forming climax vegetation on limestone and littoral soils. It’s drought tolerance is remarkable and it can be found at altitudes of 1,000 metres above sea level. These forests are however open rather than dense, again with Maquais vegetation beneath.

There is a climax of cultivated and wild Olive, (Olea europea subsp. europea var. europea and Olea europea subsp. europea var. sylvestris respectively), and numerous feral forms plus Carob (Ceratonia siliqua) in hot and arid zones and the Aleppo Pine is fond scattered here too.

In Mediterranean North Africa to this association one can also find the Drawf Palm (Chamaerops humilis).

The Maritime Pine (Pinus pinaster) forms pure stands only in maritime locations on siliceous outcrops and these can be seen in Spain, France and Italy especially.

The Umbrella or Stone Pine (Pinus pinea) have a wider distribution on sandy littoral dunes, and typically these have a luxurious undergrowth.

Cypress (Cupressus sempervirens) occur as scattered tress with evergreen undergrowth and some Garrigue species, notably on: Crete, Rhodes and Cyprus.

Laurel (Laurus nobilis) woods are found in Greece, Crete and the Balkans.

The Maquis Biome

Two distinct and major Maquis variations have been determined by ecologists. One is referred to as PRIMARY Maquis and the other is referred to as SECONDARY Maquis. It is not possible to know if the Maquis is the highest expression of vegetative development, or whether it is a climax developing under certain conditions intrinsic to the Mediterranean. The Primary Maquis is probably the highest form, but because of the long intervention of man in the Mediterranean, in most cases the Maquis is a Secondary Maquis, that is the result of felling the primaeval evergreen forests.

Products:

• Resins
• Tannins
• Gums
• Dyes
• Charcoal
• Fibres

Humans constantly cut down the vegetation and cultivate the ground for pasture or/and orchards and vineyards, only to abandon these at some later time. This has been a cyclic operation, (review again the model presented earlier in the discussion,) and consequently the Maquis has numerous variations which defy complete organisational categorisation.

After Polunin and Huxley's "Flowers of the Mediterranean"

High Maquis: Tall shrubby formations to 4 or 5 metres in height of the meso- and thermo-Mediterranean zones of the Mediterranean basin. Generally the High Maquis has a more or less closed canopy with a dominant stratum of: Tree Heather (Erica arborea), Strawberry Tree (Arbutus unedo), Greek Strawberry Tree (Arbutus andrachne), Holm Oak (Quercus ilex), Kermes Oak (Quercus coccifera), Olive (Olea spp), Judas Tree (Cercis siliquastrum), Phoenician Juniper (Juniperus phoenicea), Aleppo Pine (Pinus halepensis), Wig Tree (Phillyrea media), Spanish Broom (Spartium junceum), and Mastic Tree or Lentisk (Pistacia lentiscus), but sometimes the emergent Oaks are few or missing altogether. NB: Between this High Maquis and the Low Maquis (documented below) there are many gradations;

Low Maquis: Very shrubby formations usually between 1.5 and 2 metres in height, with a distinct lack of tall tree species. This formation has associations of, Wig Tree (Phillyrea media), Mastic Tree or Lentisk (Pistacia lentiscus), Rosemary (Rosmarinus officinalis), Jerusalem Sage (Phlomis fruticosa), Butcher’s Broom (Ruscus aculeatus), Jerusalem Thorn (Paliurus spina-christi), Sage-leaved Rock-rose (Cistus salviaefolius), Montpellier Cistus (Cistus monspielensis), Hairy Rockrose (Cistus villosus) and numerous Heathers (Erica spp.). In open zones low herbaceous perennials and sub-terranean bulbous and tuberous species can also be found along with many annuals.

Cistus Maquis: is a variant of the Low Maquis, widespread in hot arid zones, Montpellier Cistus (Cistus monspielensis) is often dominant in the Western Mediterranean, while Hairy Rockrose (Cistus villosus) dominates in the Eastern Mediterranean, and this biome tolerates heavy grazing, it often appears on abandoned land which had previously been cultivated;

Mixed (Lentisk-Carob-Myrtle) Maquis: occurs on hot arid maritime hillsides especially in the Eastern Mediterranean. This association itself has many variants and contains many different species, such as: Kermes Oak (Quercus coccifera), Hawthorn (Crataegus azarolus), Spiney Broom (Calicotome spinosa), Terebinth (Pistacia terebinthus), Italian Buckthorn (Rhamnus alaternus).

In the Mediterranean landscape the wild olive, (Olea europea spp europaea var. sylvestris) is now naturally found in the sclerophyllous and heathland shrubby biome called the: Maquis (French), Macchia (Italian), Chaparral (Portuguese) Matorral (Spanish), Phrygana (Greek), Garig (Croatian), Batha (Hebrew). Feral forms of the domesticated Olive are here also. Feral forms of olive arise from cultivar crosses and cultivar and wild olive crosses.

Wildfires in the Maquis

Thanks to its lignotuber the olives can recover from some of these types of wildfires and all that scrubby congested inner weedy branch structure which wild untended olives possess is removed – this is natural pruning.

The olive tree (wild and domesticated) typically has around 82% leaf moisture during the dry season and around 86% during the wet seasons, and that is not much of a variance illustrating its immense water retention capacity. This becomes clearer when you compare it to other non-sclerophyllous Mediterranean species like, Hawthorn (Crataegus monogyna) which has 58% leaf moisture in the dry season and 114% in the wet season.

In furnace trials at 750° C the ignition delay of olive leaves was between: 2.77 and 4.36 seconds during the dry season, and between: 4.07 and 6.43 seconds in the wet season. If we compare that to the Hawthorn (Crataegus monogyna) which had an ignition delay of between: 2.62 – 1.98 seconds in the dry season, and between: 2.18 and 3.63 seconds in the wet season we can see that the resistance of the olive leaf to fire is high.

Of the 45 Mediterranean species in the trial the Hawthorn was ranked at position 4 (wet and dry season) making it very fire susceptible, while the olive was at position 25 (dry season) and 33 (wet season), placing it in the middle and top division of the study. The full report PDF entitled: ‘Mediterranean Forest Ecosystems, Wildland Fires, Cypress and Fire-Resistant Forests’ by: Tuncay Neyisci of the Akdeniz University can be found online.

Throwing in a general note of interest on the Maquis, as well as lignotubers many species produce seeds which generally require stratification by fire to break seed dormancy, for example the Spanish Broom (Spartium junceum), which not only requires fire to stratify the seeds, the seed pods actually explode with heat and projects the seeds outwards in all directions – seed dispersal by fire.

Garrigue

Found on shallow limestone and marl stony slopes, rarely higher than half a metre.

Many of the species habiting these regions are: spiny, heath-like, and often possess woolly grey leaves, they are xerophytic species adapted for drought stress.

Plants aromatic herbs with medicinal and culinary uses such as: Lavander (Lavandula officinalis), Tarragon (Artemisia dracunculus), Sage, (Salvia officinalis), Rosemary (Rosmarinus officinalis), Thyme (Thymus vulgaris), Oregano (Origanum vulgare), Majoram (Origanum marjorana), Rue (Ruta graveolens), Savoy (Satureja montana), Hyssop (Hyssopus officinalis), Garlic (Allium sativum).

And bulbous and tuberous species also. Species like: Tulips, Crocus, Iris, Hyacinth, Fritillaries, and the Star of Bethlehem for example.

The Eastern Garrigue has plants like: Conehead Thyme (Coridothymus capitatus), Sparrow-Wort (Thymelelaea tartonraira), Yitran (Thymelelaea hirsuta), Genista acanthoclados, Greek Spiny Spurge (Euphorbia acanthothamnos), and St john’s Wort (Hypericum empetrifolim and other H. spp).

Steppe

The term steppe designates a mosaic of open, low plant formations composed of xerophytic, herbaceous and ligneous vegetation, often in scattered clumps and devoid of trees.

May often represent the final stage of landscape degeneration caused by humans (disputed).

Natural steppe is found where rainfall is too low to support a forest, but high enough to not create a desert. Mediterranean steppe varies tremendously according to rainfall from north and south, and from east and west. It is often found on interior plateaus and mountain ranges where natural vegetation has been cleared or/and extensive grazing has removed most of the vegetation.

When all the arborescent shrubs which play an important role in building up soils and creating protection for herbaceous species have been removed what remains are annuals and the tough herbaceous perennials which can survive the hostile droughts of the Mediterranean summers.

Grasses, Irises, Poppies and members of Composite family exist on the steppe where low rainfall (100-300mm paer annum) and high temperatures (to 40°C).

Diet

Tomatoes, Potatoes, Peppers (Sweet and Chili), Sweet Corn and Green Beans all came from South America fairly late in the history of the Mediterranean, after the Spanish conquests there commencing in 1492.

Citrus (Oranges, Limes, Grapefruits, Tangerines and Lemons) originate in Asia, along with the Aubergine (Eggplant).

Vines, Olives, Figs, Dates, Citrus and Pomegranates originate in the Levant.

Why Do Olive Trees Live So Long?

The olive tree has a very effective lignotuber allowing it to regrow after fire and frost and this equals continuation via rapid regeneration. In the Mediterranean, forest fires are a normal part of the ecosystem, and frosts though rarely harsh, as they are in the cold temperate zones do occur in the Mediterranean if infrequently. If the leaves and small aerial parts of the tree are burned off by fire or killed by frost, regrowth is rapid because the root system remains intact and full of stored energy and vigour to power the regrowth. So, what would kill a tree from another species is merely a form of natural pruning to an olive, and in some respects it’s an advantage because olives benefit from quite hard pruning.

The olive tree and its numerous cultivars are evergreen xerophytic (drought hardy) trees possessing hypostomatic leaves covered with trichomes (glandular hairs) on both sides. These epidermal trichomes conserve moisture and humidity around the stoma thus allowing them to stay open for prolonged respiration and photosynthesis in harsh arid conditions.

These evergreen leaves are also sclerophyllous (hard and heat resistant) to further conserve moisture. The leaves are ever present meaning photosynthesis can commence at any time when conditions are right. So, working together the trichomes and sclerophyllous leaves allow the olive tree to tolerate severe drought and harsh solar conditions which would kill other tress.

The extended photosynthesis allows for sugars to become more concentrated in the cells and thus the cells are more resistant to freezing. This is a common factor with many species from all the Mediterranean zones around the world. For example, a -5°C will kill certain Mediterranean species in the UK, but the same temperature will not kill that same species in the Mediterranean because the cell sap is denser wither sugars, and thus resists freezing.

Olive trees are slow growing hardwoods and the olive root system is wide spreading and shallow to exploit surface water (i.e., dew) again preventing desiccation and death in an otherwise hostile environment.

Once established its secondary thickened root plate is extremely hard like its trunk, the wood of which has a crushing strength of 11,180 lbf/in2 (77.1 MPa) and thus it is more difficult for pathogens to penetrate. It doesn’t stop pathogens completely, but it certainly does diminish their efficacy.

In its native environment soils are poor shallow and stony, thus in conjunction with the arid aerial environment leaf systems, the vegetative growth of olive trees are further slowed down and this results in even harder denser heartwood. These native soils also have high alkaline pH levels and many pathogenic fungi favour moist acidic soil pH, so the pathogens in the natural environment are to some extent restricted also by the environment.

Fire

There are two broad mechanisms by which plant populations persist under recurrent disturbances: resprouting from surviving tissues, and seedling recruitment. Species can have one of these mechanisms or both.

Postfire regeneration traits

• Postfire resprouting The ability to generate new shoots from dormant buds after stems have been fully scorched by fire. This term is preferable to sprouting, which refers to initiation of new shoots throughout the life cycle of a plant. Species are typically classified as resprouters or nonresprouters depending on this ability. There are different types of resprouting depending on the location of the buds (epicormic, lignotuber, rhizome, roots, etc.)
• Postfire seeding The ability to generate a fire-resistant seed bank with seeds that germinate profusely after fires (fire-cued germination). Typically, such species restrict recruitment to a single pulse after a fire. Seeds may be stored in the soil or in the canopy (seed bank; Box 3). Species are typically classified as seeders or nonseeders (or fire-dependent/fire-independent recruiters) depending on this ability. There are different types of postfire seeding.

Postfire strategies

• Obligate resprouter Plants that rely on resprouting to regenerate after fire (resprouters without postfire seeding ability). These plants do not germinate after fire because they lack a fire-resistant seed bank. Note that obligate resprouters might reproduce by seeds during the fire-free interval, but the terminology of seeders and resprouters refers to the postfire conditions.
• Facultative seeders Plants that have both mechanisms for regenerating after fire, that is, they are able to resprout and to germinate after fire.
• Obligate seeders Plants that do not resprout and rely on seeding to regenerate their population after fire (nonresprouters with postfire seeding ability). Because they tend to recruit massively once in their lifespan (after fire) and fire kills the adults and typically exhausts their seed bank, they can be considered semelparous species with nonoverlapping generations and a monopyric life cycle. Note that the term ‘seeders’ refers strictly to postfire conditions, and cannot be attributed to plants that regenerate by seeds in other conditions.
• Postfire colonizers Plants that lack a mechanism for local postfire persistence, but they recruit after fire by seeds dispersed from unburned patches or from populations outside the fire perimeter (metapopulation dynamics).

Life cycle in relation to fire

• Monopyric Species that perform all their life cycle within a fire cycle. In plants, examples are annual and biennial species, postfire obligate seeders and some bamboos.
• Polypyric Species that perform all their life cycle through multiple fire cycles. In plants, examples are those with postfire resprouting capacity as well as trees with other survival strategies such as very thick bark.

Basic fire regimes

• Surface fires Fires that spread in the herbaceous or litter layer, such as the understory of some forests and in savannas and grasslands. These fires are usually of relatively low intensity and high frequency.
• Crown-fires Fires in woody-dominated ecosystems that affect all vegetation including crowns. They are typically of high intensity. Examples are fires in some Mediterranean-type forest and shrublands and in closed-cone pine forests.

Revisions

• Rename guides to waymarks
• Make all waymarks personal (narratives)
• Add option to toggle between species count and observations; and other params?
• Get both taxa list and observations (by date range e.g. one day).
• Include both the default image (check rights) and user observation (cf. specimen against the 'standard' or typical species)

• Specimen over species
• Observation over type
• Particular over general
• Account over abstraction

Fire

Eucalyptus globulus in Portugal

Também em Portugal esta árvore se comporta como uma espécie invasora embora nenhuma medida de erradicação tenha sido levada a cabo sobretudo devido ao valor económico da espécie. Contudo, dado que o eucalipto consegues absorver grandes quantidades de água no verão, apresenta vantagem competitiva sobre as demais espécies vegetais, com consequências nefastas para a biodiversidade das florestas.

Outra polémica em torno desta espécie prende-se com os fogos florestais, um flagelo recorrente em Portugal na época de verão. E assim, o Governo português começou a estabelecer limites para as de eucalipto no país a fim de conter a expansão da espécie e incentivar o plantio de espécies de árvores nativas europeias, porém não nativas de Portugal, que também possuem importância económica e cultural quanto a espécie invasora possui, mesmo assim a medida se baseou na controversa da plantação de Eucalyptus globulus e das outras espécies de eucalipto em Portugal.

“By the early ’70s Portugal was fighting wars in three African countries, so we needed the money. Special laws were created for the expansion of the eucalyptus.”Pedro Bingre, Quercus

The exotic blue gum is the most abundant tree in Portugal, covering about 7% of the land.

Plantation eucalypts are grown in rotation periods of 12 years, during which time the undergrowth is cleared at least twice. “In a native oak forest you’d find, in one hectare of woodland, at least 70 or 80 species of plant,” says Bingre. “In a eucalyptus forest, you would hardly find more than 15.”

• 23% eucalyptus
• 27% maritime pine
• 23% cork oak
• 27% other tree species

Main culprits are small landowners

• The rural exodus had, and still is having, relevant effects on forest management.
• Decrease in the demand for flammable forest sub-products generated from pine resin = increased risk of forest fires. (Resin tapping yielded an average of 115243 tons / year in the 1980’s decreased to 21326 tons in the period 1996 – 2002).
• The scarcity of workers capable and available to undertake forest maintenance operations increases the labour costs to forest owners, leading to…
• Forest owners are less willing to hire workers to clean their forest holdings, leading to…
• The direct consequence of abandonment of forest land by the owners due to low forest revenues unable to cover the high maintenance costs = increased risk of forest fires.
• Urban lifestyle and the distance the owner’s residence and their forest holding also contributes to abandoned forests, left to regenerate naturally.

Where eucalyptus is primary

• Do not perform cleaning and stand tending, and the average number of types of silvicultural practices they exhibit is practically zero.
• Harvesting is outsourced to the product’s buyer charged with mobilising the required workforce and equipment.
• The forest establishment results from wild germination and seedlings.
• They correspond to the group of owners who least apply their own or their family’s labour.
• They are the oldest ( <70 years of age) owners, with a comparatively higher rate of female ownership (30%), and lower proportion of owners living in the same parish where the forest is located (73%), and having a farm (64%).
• Their properties are very small ( <1 ha), small (1 to <5 ha) and medium (5 to <20 ha) sized.
• Forest is viewed as a Property Reserve (54%) where owners do not invest or implement silvicultural practices and forest is viewed as a reserve where harvest timing is mainly decided by criteria other than profitability, OR as an Investment Reserve (25%) where owners invest and harvest themselves but do not carry out silvicultural practices.

Where maritime pines are primary

• The owners carry out silvicultural practices using mainly their own or their family’s labour and equipment, and a clearing saw when it comes to bush cleaning.
• They stand out for the highest number of types of silvicultural practices, about half of the owners performing three, four, or five types of practices.
• However, they do not harvest during the reference period and show the lowest rate of forest establishment.
• They mostly own very small (<1 ha) forest properties.
• These owners are distinguished by a stronger presence of male ownership (80%), with wages from industry and services as chief source of income beyond the forest (18%).
• Owners permanently living in the same civil parish where the forest is located (87%), and daily attendance to it is 83%.
• The forest is seen as a Labour Reserve (59%) where owners carry out silvicultural practices but do not invest in the forest, which is seen as a reserve, OR as a Holding Reserve (26%) where owners invest and carry out silvicultural practices and tend to view forests as a reserve where they can harvest mainly without profitability criteria.

Eucalyptus in wildfires

With reference to Pedrógão Grande

• The whole eucalyptus tree is full of flammable oil which has the distinct smell commonly used in decongestant products.
• This oil is not only in the trunk, it is in the leaves and long bark strips which peel off and collect on the forest floor or remain suspended on the trees. Essentially, left to its own devices, the eucalyptus stands in a pile of its own debris, ready to burn, and so continue its life-cycle (fire opens the seed pods).
• This debris ignites like gasoline drawing the super hot ground flames into the canopy where the fire may spread on a second high and fast moving front – crown to crown.
• With the atmospheric phenomena that occurred on 17 June, a ‘normal’ forest wildfire can turn into a terrifying, explosive firestorm in minutes where it attains such intensity that it creates and sustains its own wind system, flinging out flaming embers which ignite new fires.
• The steep eucalyptus and pine clad hillsides of Central Portugal further facilitate fire spread…depending on the gradient, the oil-fuelled, wind-driven fires will double or quadruple their speed going uphill, also further increasing the heat intensity.
• In very hot air temperatures, the eucalyptus oil gives off fumes or vapour similar to petrol which can explosively ignite, occasionally blowing the burning crown off to travel through the air to start a new ignition point miles away. In Australia there are records of secondary outbreaks within 20 km of the original fire front.

Eucalyptus after a wildfire

• Depending on the severity of the fire, the eucalyptus re-sprouts readily post-fire even if the tree is destroyed above ground (top-killed). It sends up new shoots from lignotubers (woody growths at ground level or underground) and/or from epicormic buds on the trunk. These epicormic buds are stored deep in the trunk where the bark is thickest.
• The proportion of pine trees in the eucalyptus stand in a wildfire positively affects mortality and top-kill of the eucalyptus.
• In a managed eucalyptus stands the burned trees are usually cut and the basal re-sprouts may be retained for coppicing.
• The seeds of a eucalyptus are stored in woody capsules in the canopy where they are safer from fire heat damage as ground fire temperatures are higher than those at the canopy. If seed capsules are on the ground in a fire they will burn like everything else.
• The heat of a fire triggers the capsule to split (dehiscence), which allows for germination (in its original region) in the optimal post-fire conditions and when the risk of new fire is low.

Is the eucalyptus to blame for the 2017 fire tragedy?

The answer has to be no. It is the extraordinary level of neglect and mismanagement of the eucalyptus by man that is to blame, allowing the unchecked accumulation of fuel. Man has permitted the unimpeded spread of continuous forests and the ‘double jeopardy’ of these forests composed of mixed flammable eucalyptus and pine, right to the very edges of our roads, houses and villages.

The flammable eucalyptus tree is demonised for many reasons but especially when it comes to wildfires by causing them to spread and burn faster. However, there is not one scrap of empirical scientific evidence that demonstrates this despite all the articles written to the contrary and repeated so often that everyone believes it.

It has been demonstrated that any unmanaged forest plantation with a high density of undergrowth, brushwood or scrub responds to fire in a similar manner, regardless of the dominant species, compared to the fire behaviour of other plantations with intense management of the understorey vegetation. So, whenever there is eucalyptus, pines or cork oak stands without understorey management, fires can burn for days.

Given a ‘choice’ a fire, by far, ‘prefers’ to burn scrubland over forest. In a forest area however, a fire will avoid Ceratonia siliqua (Carob tree), evergreen oaks and Pinus pinea (Stone pines) in favour of Pinus pinaster (Maritime pine), Eucalyptus globulus and deciduous oaks. Further analysis showed maritime pine stands are more fire prone than all other forest types, including eucalyptus.

Eucalyptus also gets a lot of stick for using excessive amounts of water, consequently drying out the ecosystem and thereby increasing the wildfire risk. Research from Australia has reported the remarkable finding that all eucalyptus measured across Australia used the same amount of water for a given amount of leaf material – other tree species use various different amounts of water. Estimations of the amount of eucalyptus tree cover at a given location using satellite images of the leaves can help calculate how much water the entire forest or catchment area uses. Of course controlling eucalyptus water consumption by reducing leaf material would require additional forest management measures, the basics of which are lacking in most areas of Portugal.

Maritime pine trees in wildfires

A mature maritime pine can usually survive a low to moderate intensity surface fire because it has thick, fissured bark.

However, a pine rarely survives when it is in the path or head of an exceptionally hot, intense wildfire such as in 2017. Where you see the trunk completely charred from top to bottom, the tree is likely to be dead. Young maritime pines nearly always perish in fierce forest fires as they have thinner bark and not having reached a mature height, they burn as understorey vegetation. As intense wildfires happen more frequently than they did in the past, the pine forests are decreasing in size. In their place there is the progressive substitution of eucalyptus in the region.

• The needles and wood litter of the maritime pine is prone to easy ignition, fast and complete combustion and high heat release.
• The close density of the pines (often mixed with eucalyptus) in unmanaged forests makes for extreme amounts of surface fuel that exacerbates the potential for conflagrations. The canopies are also close or overlapping which facilitates crown-to-crown ignition.
• Like the eucalyptus, pines produce their own volatile compounds (such as α-pinene) which are present in pine needles. These compounds are released when temperatures reach around 150-175 º C. They accumulate locally in the air around the trees and when ignited as the flames reach the area, burn rapidly and intensively possibly causing the phenomena of a fire ‘flash-over’ or explosion.
• Where there are more frequent successive fires in a maritime pine forest area, the trees become even more of a fire hazard because the new young pine trees can never reach maturity and act like understorey shrubs that greatly increase the probability of fire.
• Stands of maritime pine commonly grow on the steep hillsides of Central Portugal so the speed and heat intensity of the fire increases as it travels uphill and at the crest. This also makes fighting the fire very difficult.
• It must be noted that where stands of pines have been thinned, there will be increased wind movement and litter drying which may aggravate a future ground fire.

Maritime pine trees after a fire

• The pine is partially serotinous and seeds stored in cones in the canopy are the major source for the post-fire regeneration of the tree.
• Cone serotiny (closed cones which require heat to open) may vary among individual trees in the same population – particularly found in the younger trees.
• The serotinous cones of maritime pine begin opening at temperatures around 50º C.
• The cones open gradually in the two or three days that follow the thermal shock such that when seed dispersion begins the fire is extinct and seeds land on a cool bed of ash.
• Adult trees are often killed by fire, depending on the degree of crown and cambium damage, and there is no re-sprouting in the species.
• Typically the burned trees are salvage logged and natural regeneration from seeds occurs.

Where pines have been cut, thinned or pruned, the crown branches with attached needles are frequently left on site which significantly increases the risk of future fires – less shade on surface fuels, increased wind speeds, reduction of relative humidity, increased fuel temperature and reduced fuel moisture. Immediately after the 2017 fires, there was a rush to cut the dead pines before they lost weight and became less valuable, and later cutting to comply with the land cleaning deadlines. In many cases the owners have left vast piles of pine debris which will not decompose any time soon. It can take more than 7 years for pine litter to completely decompose – longer, if there are prolonged spells of dry weather which slow the action of fungi, bacteria and gastropods etc.

In the forests away from human habitation, it may be that the debris is deliberately spread across a cut site in order to mitigate the effects of erosion. This is an common method of erosion control after a fire. However, some experts believe that due to climate change, ‘mega-fire’ events will become more frequent in the near future, essentially becoming the new ‘normal’ wildfire. This then makes extensive salvage logging and leaving debris in situ look to be a decidedly dangerous option.

Mitigation

Cercis siliquastrum and Ceratonia siliqua

Classically, vicariant phenomena have been essentially identified on the basis of biogeographical and ecological data. Here, we report unequivocal evidences that demonstrate that a physical–chemical characterization of the epicuticular waxes of the surface of plant leaves represents a very powerful strategy to get rich insight into vicariant events. We found vicariant similarity between Cercis siliquastrum L. (family Fabaceae, subfamily Cercidoideae) and Ceratonia siliqua L. (family Fabaceae, subfamily Caesalpinoideae). Both taxa converge in the Mediterranean basin (C. siliquastrum on the north and C. siliqua across the south), in similar habitats (sclerophyll communities of maquis) and climatic profiles.

These species are the current representation of their subfamilies in the Mediterranean basin, where they overlap. Because of this biogeographic and ecological similarity, the environmental pattern of both taxa was found to be very significant. The physical–chemical analysis performed on the epicuticular waxes of C. siliquastrum and C. siliqua leaves provided relevant data that confirm the functional proximity between them.

A striking resemblance was found in the epicuticular waxes of the abaxial surfaces of C. siliquastrum and C. siliqua leaves in terms of the dominant chemical compounds (1-triacontanol (C30) and 1-octacosanol (C28), respectively), morphology (intricate network of randomly organized nanometer-thick and micrometer-long plates), wettability (superhydrophobic character, with water contact angle values of 167.5±0.5° and 162±3°, respectively), and optical properties (in both species the light reflectance/absorptance of the abaxial surface is significantly higher/lower than that of the adaxial surface, but the overall trend in reflectance is qualitatively similar). These results enable us to include for the first time C. siliqua in the vicariant process exhibited by C. canadensis L., C. griffithii L., and C. siliquastrum.

Fire resistant trees

• Mediterranean Cypress ( Cupressus sempervirens)
• Mulberry ( Morus alba / nigra )
• Willow ( Salix spp.)
• Fig ( Ficus carica )
• Paulownia ( Paulownia tormentosa)
• Cork Oak ( Quercus suber)
• Strawberry Tree ( Arbutus unedo )
• Carob ( Ceratonia siliqua )
• Sweet Chestnut ( Castanea sativa )
• Turkish Hazel ( Corylus colurna )

Fieldnotes

Field Note

• Field Notes should be under 500 words. Species lists may exceed the 500 word limit.
• If you wish, Field Notes may consist of photos, drawings, or videos only.
• Unlike articles, Field Notes may be (but don't have to be) very limited in scope, e.g. describing a single observation, musings about the natural world, or photos/descriptions of a species you weren't able to identify.

Article

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• Articles should explore a topic, species, group of species, habitat, region, or study in some depth. Including a "Literature Cited" section at the end of your article is encouraged if appropriate but not required.

Habitats

Succession

Ecosystems are formed by the interactions between a community of living organisms and the physical environment that surrounds them. These ecosystems undergo ecological succession in response to changes in environmental conditions; this is a natural process of change over time that is brought about by progressive replacement of one plant or animal community with another.

This process starts with what is called as the “pioneer community”, and eventually leads to the development of a stable and mature community, referred to as the “climax community”. The process of succession can halt at a pre-climax stage when some factor is limiting; such as when the organism needed to bring about the necessary changes that lead to the creation of the following community is absent. Apart from biotic factors (living), limiting factors may also be abiotic (non-living), such as lack of water.

• Primary succession Begins when pioneer species, like mosses and lichens, colonise barren substrate, such as rock, sand or soil, which has never before supported any vegetation
• Secondary succession Occurs in areas where natural vegetation has been disturbed or destroyed. The latter type is generally less species rich.

Habitats that form part of the process of succession:

• Steppe
• Garrigue
• Phrygana
• Pre-desert scrub
• Maquis
• Woodland

Steppe

Steppe is considered as the first stage in the ecological succession process. It is derived from maquis and garrigue as a result of some form of degradation, such as that caused by fire or animal grazing. It is widespread, and is characterised by herbaceous plants, especially grasses.

Umbellifers (Foeniculum vulgare), Daucus carota, Legumes (Vicia sativa subsp. nigra), Tuberous or bulbous species (Ornithogalum narbonense)

This habitat is generally devoid of shrubs, and is mainly comprised of annuals, that is, plants that live up to one year. During the dry season, this habitat type appears dry and impoverished because most plant species will, at the time, exist in the form of seeds. In contrast, the wet season brings about a change in this habitat type, which results in steppe being entirely covered by a large variety of herbaceous plants.

One also finds other types of steppe locally, including some natural ones. These are formed through climatic factors, and include the rocky steppe and the clay slope steppe.

Steppes may also be characterised by: Stipa capensis, Carlina involucrata, Galactites tomentosa, geophytes (Asphdelus aestivus), Drimia pancration

Garrigue

The second stage in ecological succession is garrigue. It is characterised by limestone rocky ground with a rugged surface, known as karst, and is heavily exposed to the brute force of the elements. Garrigue is typified by low-lying, usually aromatic and spiny woody shrubs that are resistant to drought and exposure. This type of habitat appears desolate, and is often referred to as wasteland. Nevertheless, it is probably the most species-diverse habitat in the Maltese Islands, and is of great importance not only to biodiversity, but also to ecosystem services.

Euphorbia dendroides, Periploca angustifolia, sages, rockroses, Rosmarinus officinalis, Thymbra capitata

Maquis

Maquis is the stage following that of the pre-desert scrub in the ecological succession. It is usually characterised by small trees and large shrubs, consisting mostly of an evergreen shrub community, reaching a height of up to 5m, often more. It occurs along the sides of valleys, along slopes and other areas, which are inaccessible to man, and relatively sheltered from the wind.

Myrtus communis, Ceratonia siliqua, Olea europaea, Pistacia lentiscus, Ficus carica, Prunus dulcis, Laurus nobilis, Hedera helix, Asparagus aphyllus, Rubia peregrina, Tamus communis, Acanthus mollis, Arisarum vulgare

Mediterranean woodland

Mediterranean woodlands are characterised by sclerophyllous (hard-leaved, evergreen) trees with an undergrowth of smaller shrubs. This is the highest type of vegetation that can develop in the Mediterranean climatic regime, in other words, the climax of the ecological succession. This habitat type develops from maquis, in the absence of disturbance caused by man.

In Malta, this habitat was virtually exterminated, following colonisation by man and through the grazing effects of introduced sheep and goats.

Quercus ilex, Pinus halepensis, Ceratonia siliqua, Olea europaea

Saline marshlands

Saline marshlands are transitional areas that form at the interface between the marine, freshwater and terrestrial environments. Saline marshlands are dynamic systems and undergo annual cycles of changes in salinity. The salt content changes depending on rainfall, whereas in winter the saline content is low due to a diluting effect of the rain, in summer, the salt content is more concentrated as water levels drop. Salinity in the salt marsh also depends on how close this is to sea and the influx of seawater into the system.

Limbarda crithmoides, Arthrocnemum macrostachyum, Salicornia ramosissima, tamarisks

Vegetation patterns are observed in saline marshlands that reflect differences in chemical and physical conditions. Areas that remain dry or moist harbour those plants that are not aquatic, such as the smooth-leaved saltwort (Salsola soda). Shallow parts of the salt marsh that hold a small volume of water for several days, are colonised by plants, which although not aquatic, are still able to withstand short periods of inundation until the water dries up or evaporates. Deeper areas, which remain filled with water for longer periods, only support aquatic and semi-aquatic plants.

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 as when wetlands arise when rainwater collects in depressions close to the sea.

Rainwater rock pools

The movement or flow of acidified water derived from precipitation and runoff, leads to the gradual erosion of limestone substratum and the eventual formation of hollows or kamenitzas. The latter collect rainwater in winter, forming shallow freshwater rock pools, which provide a suitable habitat for a number of rare species. Freshwater rock pools are ephemeral, that is, last for only a short period, because in summer these dry up completely and may become colonised by terrestrial vegetation.

Species that are specialised to this habitat type remain dormant in the soil during the dry stage, and emerge during the wet stage. Other species move out of the rock pool, when this is in the dry state, and return when conditions become favourable.

The duration of how long the rock pool remains with water determines the species richness of that particular rock pool.

Sand dunes

Sand dunes are dynamic systems that form by a slow process of accretion, that is, the build-up of sand because of natural wave action. Sandy beaches are backed by dune systems, which provide an essential role in the stability, as well as in the defence of coastal communities. The formation of sand dunes depends on the sand that is carried inland by wind from the beach. Subsequently, sand is deposited and trapped upon encountering clumps of vegetation or some other form of obstacle.

Dune vegetation is adapted to the harsh conditions present in this type of habitat. Such conditions include high temperatures, dryness, occasional inundation by seawater and accumulation of sand. Plant adaptations include extensive root systems that provide efficient anchorage in the porous and mobile substrate and other distinctive morphological features, such as fleshy leaves to limit water loss, and the presence of short white hairs to help in temperature regulation.

Vegetation type changes across the dune system with distance from the beach, forming a typical zonation pattern.

Valley watercourses & riparian communities

Valley watercourses are one of the most species-rich habitats on a national scale. Yet, they are considered as one of the most endangered habitats in the Maltese Islands.

In gently sloping valleys, the watercourse community is similar to that of the valley sides, whereas in steep-sided valleys there is a clear distinction between communities along the watercourse and those vegetating valley-sides. Where the terrain permits, the valley sides are terraced and cultivated. The construction of man-made dams in certain valley systems has intentionally retarded the water flow for irrigation purposes. Such dams have created new freshwater habitats where varieties of aquatic and semi-aquatic species thrive.

The watercourse community is by nature dynamic, and its integrity depends on the amount and frequency of rainfall as well as other abiotic factors, such as the rate of siltation. Valleys are dry for some months of the year and water only flows during the wet season. However, some local valleys drain springs originating from the perched aquifers and retain some surface water even during the dry season.

In general, the greater part of local plant and animal species reliant of water during some part of their life cycle are found in valley watercourses.

Caves

Cliffs & screes