Wild olive, tree lucerne, tagasaste, Atriplex, mulberry, albaida, argan and carob are identified in the LIFE ScrubsNet protocol as species of forage interest. However, they respond differently to drought, frost, salinity and soil conditions. Selection must therefore reflect the characteristics of each holding and comply with current regulations, particularly where non-native plants are concerned.
Woody vegetation can provide leaves, browse and fruit when herbaceous pasture becomes scarce. It can also diversify livestock diets, provide shade, protect the soil and support biodiversity.
However, a species with good forage value will not necessarily be suitable for every holding. Rainfall, extreme temperatures, soil depth and composition, salinity, livestock type and management objectives all influence how a plant will perform.
The LIFE ScrubsNet document “Livestock and scrub management for dehesa regeneration” presents several species of interest in Mediterranean areas and states that any plants selected for establishment must be adapted to local climate and soil conditions. It also advises that non-native species should only be considered in dehesas registered as arable land and always in accordance with current legislation.
What should a suitable forage species provide?
The protocol identifies several desirable characteristics for forage shrubs and trees.
A suitable species should produce abundant leaves, shoots or fruit; have good nutritional value and palatability; present no significant toxicity; tolerate pruning and browsing; and regrow effectively after use.
It should also establish relatively easily while having a low invasive potential. Ideally, it should allow herbaceous pasture to grow beneath its canopy and integrate into the holding’s vegetation mosaic.
Selection should not therefore be based only on the quantity of feed a plant can produce. Its long-term behaviour and ecological compatibility are equally important.
Wild olive: Mediterranean hardiness and multiple resources
The wild olive (Olea europaea var. sylvestris) is the wild form of the cultivated olive.
It is adapted to Mediterranean conditions with relatively mild winters and dry, hot summers, although severe frost may cause damage. It tolerates different soil types and can provide leaves, shoots and fruit.
The protocol describes traditional practices in which branches and regrowth were used as livestock feed. Its fruits have also been used to fatten Iberian pigs.
Where it already occurs naturally, its hardiness and ecological integration make it particularly valuable.
Tree lucerne: potential in semi-arid environments
Tree lucerne (Medicago arborea) is a perennial shrub that can grow to around two metres.
It is adapted to semi-arid Mediterranean climates with pronounced summer drought and warm temperatures. It can develop on both calcareous and siliceous soils, including shallow, nutrient-poor ground.
Its drought resistance gives it forage potential, but it does not tolerate frost well. Its use should therefore be considered carefully in inland or high-altitude areas subject to low winter temperatures.
Tagasaste: protein-rich forage
Tagasaste (Cytisus proliferus) is an evergreen shrub that may develop into a small tree with a dense crown.
It favours light, sandy and well-drained soils and performs particularly well on acidic and volcanic substrates. Although it tolerates some alkalinity, it is unsuitable for saline soils.
The protocol highlights its use as browse and its value for feeding livestock during dry summers. It is described as highly palatable, protein-rich and not associated with significant toxicity problems.
Its establishment must nevertheless be assessed against the specific environmental conditions of the location.
Atriplex: an option for aridity and salinity
The document presents different Atriplex species, including old man saltbush (Atriplex nummularia) and Mediterranean saltbush (Atriplex halimus).
- A. nummularia* is adapted to arid and semi-arid conditions and tolerates high temperatures. It is used as forage and is readily accepted by goats.
- A. halimus* can grow in very dry environments and on sandy, saline or marginal soils exposed to strong sunlight. It also tolerates wind and relatively low temperatures.
These characteristics may make Atriplex valuable where other plants struggle. However, the protocol warns that some species may become highly invasive under favourable conditions.
Their use therefore requires careful assessment of origin, dispersal capacity and applicable legal restrictions.
Mulberry: nutritious leaves but greater moisture requirements
Mulberries (Morus spp.) can provide valuable livestock forage. Their leaves have long been used for other purposes as well, notably in silkworm production.
Unlike species adapted to extreme aridity, mulberries generally favour deep, fertile soils and greater water availability.
They may be appropriate for cooler areas, productive soils or land close to wetter zones. Establishment on very dry or poor soils may require additional resources and management.
Albaida: adapted to a wide range of substrates
Albaida (Anthyllis cytisoides) is a pale or greyish shrub that occurs on a wide range of substrates, including gypsum, limestone, schist and coastal sands.
It favours free-draining soils and is not tolerant of severe frost. The protocol identifies it as an important forage plant, particularly for goats.
It also has value for pollinators and may therefore combine productive and ecological functions.
Argan: resistance to prolonged drought
Argan (Argania spinosa) is highly resistant to prolonged drought and high temperatures. It can grow in areas with limited rainfall but does not tolerate severe frost.
Its foliage and fruit have forage value, especially for goats, while its seeds also produce a high-value oil.
Because it is not native to most dehesa regions, any proposed introduction should be assessed from agronomic, ecological and legal perspectives.
Carob: fruit and leaves for mild climates
Carob (Ceratonia siliqua) is adapted to dry, warm and mild climates with little frost.
It can grow on rocky and arid land, provided there is sufficient sunlight. Its pods and tender leaves can both be used as livestock feed.
The fruit provides a concentrated resource that can be stored, but sensitivity to frost may prevent successful establishment in some inland regions.
No single species is suitable everywhere
One species may withstand drought but be highly sensitive to frost. Another may tolerate saline soils but present a risk of invasive spread. Some produce abundant foliage, while others are more valuable for fruit or for browsing livestock such as goats.
Before planting or reinforcing a species, managers should examine:
- maximum and minimum temperatures;
- rainfall and drought duration;
- soil type, depth and drainage;
- possible salinity;
- the livestock that will use the resource;
- the purpose of the paddock;
- regrowth and dispersal capacity;
- whether the species is native;
- environmental protection requirements and current regulations.
Introducing forage vegetation should never be treated as a standard solution. It must be tailored to each holding.
Prioritising local species
Where possible, conserving and managing forage species already present may be safer than introducing new plants.
Local species are already adapted to environmental conditions and form part of existing ecological relationships. They may also provide shelter, protect soil, feed wildlife and support natural regeneration.
Where introduction is being considered, nearby areas with similar soil and climate should be examined, ecological compatibility should be assessed and any administrative restrictions should be checked in advance.
Selecting species for both feeding and conservation
The LIFE ScrubsNet message is clear: forage value is not the only criterion that should guide species selection.
Wild olive, tree lucerne, tagasaste, Atriplex, mulberry, albaida, argan and carob have very different characteristics and may perform differently from one holding to another.
A well-founded choice can increase feed availability, diversify livestock diets and improve the resilience of the farming system. An inappropriate introduction may fail, generate unnecessary costs or cause ecological problems.
Choosing the right plant means combining livestock production, environmental adaptation, conservation and regulatory compliance.
The LIFE ScrubsNet project is co-funded by the European Union through the LIFE programme, LIFE20 NAT/ES/000978.