Iberian conifer Forests

• Category: Forest Biomes.
• Geographic Location: Europe.
• Summary: This outstanding, diverse set of forest communities is distributed across the whole Iberian Peninsula, from the Mediterranean coastline to the high mountain areas.

Because of its location in southwestern Europe and its mountainous topography, the Iberian Peninsula of Portugal and Spain has a diverse gradient of climatic conditions that becomes evident in three main biogeographical domains. First, the Mediterranean bioregion is the largest in the Iberian Peninsula, and covers about three-quarters of its territory from the northeast (Catalonia) to southwest (Andalusia and south-central Portugal). Second, the Euro-siberian or Atlantic bioregion extends from northwestern Galicia and northern Portugal to the north-central Iberian Peninsula (Cantabrian Mountains and Euskadi). Finally, the Boreo-alpine bioregion occupies a reduced territory in the northeastern Iberian Peninsula, mostly in the area of the Pyrenees, and in a scattered manner in the summit areas of the Iberian and Central mountain systems and the Sierra Nevada.

Conifer forests occur in all three of these bioregions, which are also conditioned by human intervention, especially land-use changes linked to forestry. Examples of this influence are reforestation plans, promoted in the Iberian Peninsula since the 1950s to control soil erosion; water-flow management; and timber production in which conifers, especially pines, have been widely used.

In the Mediterranean bioregion, general bioclimatic conditions are characterized by mild temperatures, which average 61 degrees F (16 degrees C) annually, and seasonal rainfall that averages less than 24 inches (600 millimeters) annually. Rainfall occurs mostly during the spring and autumn, with a typical summer drought period.

Flora

The Iberian conifer forests are dominated by thermophilous species that have adapted to low water and poor soils. In addition, they show outstanding resprouting capacity as an adaptation mechanism to wildfires.

The most extended conifer is Aleppo pine (Pinus halepensis), which covers large areas of the eastern Iberian coastline and the Ebro River valley. It is the most extended conifer in the whole Mediterranean basin, due mainly to its high colonization capacity. Two other important pines are the maritime pine (Pinus pinaster) and the stone pine (Pinus pinea); the first appears on the Mediterranean coastline, while the second occupies the northwestern and central Iberian Peninsula.

Junipers are present from the coast to about 3,281 feet (1,000 meters). Cade juniper (Juniperus oxycedrus) and Phoenician juniper (Juniperus phoenicea) appear in basal areas of the central and eastern Iberian Peninsula, while Spanish juniper (Juniperus thurifera) occupies higher areas in central Spain. Finally, Mediterranean cypress (Cupressus sempervirens) has relict populations; most of the time, it has been planted as an ornamental tree. In certain coastal environments of the Murcia region, characterized by water scarcity, sparse relict stands of barbary thuja (Tretraclinis articulata) remain.

In mountain areas from approximately 3,281–5,906 feet (1,000–1,800 meters), Mediterranean bioclimatic conditions are replaced by Euro-siberian conditions, similar to those present in central Europe. This area is characterized by more abundant rainfall with an annual average of 39 inches (1,000 millimeters), and cooler temperatures averaging 50–53°F (10–12°C).

Two main conifer species form broad forest stands: Scotch pine (Pinus sylvestris) and European black pine (Pinus nigra). Scotch pine occupies large areas of the northeastern Iberian Peninsula, especially in the Pyrenees, Iberian, and central mountain systems; it has also been widely planted in the Cantabric Mountains and in the Sierra Nevada. Nevertheless, due to its high tolerance to a wide range of environmental conditions, and to recent land-use changes such as the abandonment of traditional grazing, this conifer is increasing its extension. European black pine appears in the Pyrenees south of the Iberian mountain system, and in the highest Mediterranean coastal mountains; it has also been planted in northern and central Spain. At this altitude, common juniper (Juniperus communis) occurs in the understory of northeastern evergreen holm oak (Quercus ilex) forests. Yew (Taxus baccata) forms sparse stands predominantly mixed with beech (Fagus sylvatica) forests on shady and humid slopes, mainly in the Cantabric Mountains.

High-mountain conifer forests include those geographically limited to the highest ranges from about 5,906 feet (1,800 meters) to the timberline at about 7,546 feet (2,300 meters), just below the summit areas occupied by alpine grasslands where dwarf juniper (Juniperus nana) sometimes appears. At that altitude, bioclimatic conditions are Boreo-alpine, characterized by cold temperatures year-round below 50°F (10°C), high rainfall of up to 59 inches (1,500 millimeters) per year, and abundant snowfall during the winter months.

Three conifer forest communities are represented at this stage. First, European silver fir (Abies alba) forests occur on cold and shady slopes of the central and western Pyrenees, and also in two little relict areas in the Guara and Montseny massifs, which represent the southern stands of this conifer in its whole European distribution range. Another singular forest, dominated by Spanish fir (Abies pinsapo), occurs in a small area of southern Spain. This species represents a flora relict from cold periods in three mountain systems: Sierra de las Nieves, Grazalema, and Sierra Bermeja. Finally, mountain pine (Pinus mugo ssp. uncinata) forests reach the highest altitudes in the Iberian forests. Its geographical distribution is limited to areas up to 5,577 feet (1,700 meters), predominantly in the Pyrenees and to a lesser extent in the Iberian mountain system.

Exotic conifer plantations have been increasing in mountain landscapes, mainly in the northern Iberian Peninsula, because of their high timber production capacity. The most commonly used species are Monterrey pine (Pinus radiata) and Douglas fir (Pseudotsuga menziessi).

Fauna

The Iberian Conifer Forests biome offers a wealth of diversity, especially among bird species, of which at least 150 are present. These include the endangered griffon vulture (Gyps fulvus), the Spanish imperial eagle (Aquila heliaca adalberti), and many others. Mammals common to the area include several endangered species, such as the Gredos ibex (Capra pyrenaica victoriae) and the wolf. Red and roe deer are quite common in the forest areas.

Threats

Modern threats to this biome are mainly from overuse, such as clear-cutting trees for the lumber industry; road construction; overgrazing; and, more recently, tourism. Climate changes for the Iberian conifer forests may cause changes in the distribution of various plant and animal types; certain species may be forced to migrate to find suitable habitat at different altitudes, and latitudes, than they previously occupied, due to altered temperature, extreme weather patterns, moisture, and fire regimes. Changes in the onset timing of seasons is also a concern. Species adapted to temperate Mediterranean climate areas, for example, may some day populate areas that are too cool or even too warm to accommodate them. A study published in 2022 analyzed whether the atlas cedar, which comes from a more arid ecosystem, could help mitigate the effects of climate change in Iberian forests. Scientists believed that the atlas cedar had the potential to replace other conifers affected by climate change. Another study, published in 2023, found that certain broadleaf species and mixed forests may benefit regions, such as the Iberian conifer forests, in adapting to climate change.

Bibliography

Andersson, F. A., ed. Coniferous Forests. Ecosystems of the World, Vol. 6. Elsevier Science, 2005.

"Atlas Cedar as an Alternative to Mitigate the Effects of Climate Change on the Iberian Peninsula." Phys Org, 15 Feb. 2022, phys.org/news/2022-02-atlas-cedar-alternative-mitigate-effects.html. Accessed 8 Aug. 2022.

Garzón, Marta B., and Helios S. Ollero. "Effects of Climate Change on the Distribution of Iberian Tree Species." Applied Vegetation Science, vol. 11, no. 2, 2008, pp. 169-178. doi.org/10.3170/2008-7-18348. Accessed 8 Nov. 2024.

Eckenwalder, James E. Conifers of the World: The Complete Reference. Timber Press, 2009.

Farjon, Aljos. A Handbook of the World’s Conifers, Vols. 1 and 2. Brill Academic Publishers, 2010.

“Iberian Conifer Forests.” One Earth, www.oneearth.org/ecoregions/iberian-conifer-forests/. Accessed 8 Nov. 2024.

Rull, Valenti and Teresa Vegas-Vilarrubia. "Conifer Forest Dynamics in the Iberian Pyrenees during the Middle Ages." Forests, vol. 12, no. 12, 1 Dec. 2021, doi.org/10.3390/f12121685. Accessed 8 Aug. 2022.

Sánchez de Dios, R., et al. “The Renaissance of Mixed Forests? New Insights into Shifts in Tree Dominance and Composition Following Centuries of Human-Induced Simplification of Iberian Forests.” Ecosystems, vol. 26, 2023, pp. 1159–1172. doi.org/10.1007/s10021-023-00823-7. Accessed 8 Nov. 2024.