During spring, excessive grazing pressure can jeopardise the growth of new trees. Young scrub shoots and newly emerged holm oak and cork oak seedlings are particularly vulnerable, which means that grazing must be managed carefully in regeneration areas.
Spring is a decisive stage for dehesa vegetation. As temperatures rise and moisture becomes available, trees and shrubs produce new shoots, while seedlings enter a fundamental phase of their development.
However, this period of growth can also become a time of particular vulnerability. When stocking rates are too high, livestock may consume the tender shoots of scrub vegetation and reach the small holm oaks and cork oaks that are beginning to establish themselves.
The document “Livestock and scrub management for dehesa regeneration”, produced as part of the LIFE ScrubsNet project, identifies spring as a sensitive period during which grazing management can determine whether natural regeneration is supported or interrupted.
When grass is scarce, livestock consume more shrubs
Livestock do not use all plant resources in the same way throughout the year. When there is not enough herbaceous pasture, animals begin to consume the leaves, fruit and shoots of available shrubs more intensively.
This can provide a useful supplement to their diet. However, it may also be counterproductive when the aim of a particular area is to encourage the regeneration of scrub and trees.
Excessive stocking during spring may lead animals to consume new shoots within scrub patches, including newly emerged holm oaks and cork oaks. If these young trees are repeatedly browsed, they may disappear before becoming part of the next generation of tree cover.
Tender shoots are especially vulnerable
Holm oaks and cork oaks grow slowly during their first years. Their limited height keeps them within the reach of livestock for a prolonged period.
Spring shoots are tender and accessible, making them easy to consume. A single browsing event does not always kill the plant, but repeated browsing prevents it from gaining height, weakens its reserves and delays its development.
This continuous pressure can keep young trees in the form of small shrubs for years or eventually cause them to disappear.
Natural regeneration therefore depends on more than an acorn simply germinating. The seedling must also have enough time and protection to overcome its most vulnerable stages.
Management adapted to each area
The LIFE ScrubsNet protocol states that grazing should be organised according to the sensitivity of each area, giving priority to vegetation recovery at critical times.
In regeneration areas, stocking rates should remain low. Where more intensive grazing is used, it should take place over a very short period. The aim is to avoid prolonged occupation, which allows livestock to select and repeatedly consume woody shoots.
Short, carefully planned grazing periods with greater competition between animals may encourage them to concentrate on herbaceous pasture. However, this option requires precise management to prevent damage to scrub and young trees.
Setting areas aside during the first years
One of the most effective ways to encourage regeneration is to exclude livestock temporarily from selected enclosures, patches or field boundaries.
These protected areas allow scrub to recover and give holm oaks, cork oaks and other woody species enough time to reach a sufficient level of development before being exposed to livestock again.
The required exclusion period will depend on the initial condition of each area. The presence of seedlings, small shrubs, scrub seeds and diverse vegetation may help accelerate the process.
During these years, any grazing should be occasional, involve low stocking rates and take place outside spring. Late summer and early autumn are identified as more suitable periods for certain grazing activities.
Protecting only the most sensitive areas
Excluding livestock from an entire field is not always possible or necessary. An alternative is to fence off only those patches where regeneration has already been detected or where conditions are particularly favourable.
Fixed fencing, electric fencing and other barriers can protect these areas while the remainder of the land continues to be grazed.
This approach helps combine livestock production with the conservation of new generations of trees. It also allows protected areas to be adjusted gradually according to the development of the vegetation.
Monitoring browsing to act in time
The condition of the vegetation provides valuable information about grazing intensity.
When damage appears on woody species that are not very palatable or have a limited ability to regrow, grazing pressure may already have reached a level that threatens tree regeneration.
Monitoring shoots, seedlings and scrub patches makes it possible to detect these problems before young trees disappear. Monitoring should be carried out in different parts of the farm because grazing pressure is not always evenly distributed.
Water points, feeding areas, shaded zones and places with better pasture may attract livestock and create very different impacts on vegetation.
Rest periods are also part of grazing management
Grazing management involves more than deciding how many animals enter a field. It also means determining when they enter, how long they remain and how much recovery time the vegetation needs afterwards.
Dividing the farm into enclosures and applying rational or rotational grazing systems allows areas to remain free from livestock long enough for plants to regrow before being grazed again.
These rest periods are particularly important during spring and in areas where the aim is to restore scrub or renew tree cover.
Protecting spring growth to safeguard the future
The mature holm oaks and cork oaks that shape today’s dehesa began as small seedlings that managed to survive years of slow growth and exposure to livestock.
Protecting young trees during spring does not mean removing livestock from the dehesa altogether. It means adapting grazing to the vegetation cycle and to the objectives established for each area.
The LIFE ScrubsNet message is clear: spring requires particular attention, planning and caution in regeneration areas. Excessive grazing pressure at the wrong time can eliminate young trees, while appropriate management can allow those same seedlings to secure the future of the dehesa.
The LIFE ScrubsNet project is co-funded by the European Union through the LIFE programme, LIFE20 NAT/ES/000978.