Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Reference - past-natural beech forests

Present-day forest composition and genetic structure is strongly influenced by past history. Beech has increased its natural European range throughout the last 10 000 years and occurred together with many combinations of tree species in the past. The aim of the research was to document the changing distribution of beech during the Holocene and describe the past and present forest types that contained beech.

Methods for assessing the distribution of beech included: pollen diagrams that contained significant records of beech (2% threshold - crudely equivalent to one tree in 50 being Beech within the surrounding 5 km of the collection site). These were collated from the European Pollen Database (EPD), the published literature, and personal contacts. 116 data points were grouped into 5 age categories: <1000, 1000-3000, 3000-5000, 5000-7000 and >7000 years BP. Latitude and longitude for each site was obtained from the EPD, published papers or an atlas, and the data-points were mapped using distinctive symbols for each age category. Using this base map, a sequence of four time-slice scenarios was reconstructed for 7000, 5000, 3000 and 1000 years ago. Data from the point samples were interpolated over the European landscape with consideration given to topography.

Methods concerning forest types included: samples selected at 1000-year intervals up to the present day from most of the sites that were included in the distribution map database. The proportions of the following 14 arboreal pollen types were calculated for 326 data points: Abies, Acer, Alnus, Betula, Carpinus, Corylus, Beech, Fraxinus, Picea, Pinus, Quercus (deciduous), Quercus (evergreen), Tilia, and Ulmus. The 326 data points from all time periods were clustered into 7 forest types using the total sum of squares method. Euclidean distance between samples was chosen as the distance measure.

The findings indicate 5 separate centres of beech distribution 7000 years ago, all in mountainous areas in Italy, Spain, Swiss/France, Balkan and Greece. However, 5000 years ago, four populations begin to spread - the Spanish population had become extinct. 5000 to 3000 years ago beech expands rapidly in Europe, with a maximum in the number of new sites showing rapid population increase. For the first time during the Holocene, beech begins to become established in sites away from the mountains. Long-distance colonisation and expansion are apparent with pollen evidence for populations in southeast England and southern Sweden.

The rate of expansion slows down between 3000 and 1000 years ago. One possible explanation is that most of the available habitat has been colonised, but climatic explanations are also possible. Comparison with current distribution maps of beech shows little change during the last 1000 years.

The seven forest types generated by the cluster analysis were named after the two or three most abundant pollen types. The types are pollen assemblages rather than stands of trees and are best interpreted as average forest composition within a plot of several kilometres radius.

Betula-Beech-Corylus: This forest type has the second highest mean Beech content and at present is the commonest forest type to include Beech in Scandinavia. Peak abundance was at 1000 BP.

Pinus-Beech: This forest type is one of two that is dominated by Pinus pollen, much of which can be of long-distance origin. This forest type increases in importance through time and is characteristic in mountainous regions of central and northeastern Europe.

Picea-Abies-Beech: This forest type with co-dominance of three tree species first developed 4000 years ago and has had its stronghold in the Czech Republic with some outposts in Switzerland.

Beech-Abies: This classic Beech forest type dominated central and Western Europe between 4000 � 2000 BP, but has recently declined in importance. This forest type has the highest mean Beech content and its recent decline reflects a general reduction in the central European populations of Beech during the last 2000 years.

Quercus-Beech-Corylus: This forest type is dominated by deciduous Quercus species and contains almost as much Carpinus as Beech. It has always maintained a southerly distribution and been a constant feature in Bulgaria.

Alnus-Quercus-Beech: This forest type has a centre in the Swiss Alps but is widely spread through Europe. The high values of Alnus partially reflect the bias towards wetland sites where pollen is preserved. Beech-Quercus woodland also often survives close to poorly drained areas that were deemed unsuitable for cultivation.

Pinus: This forest type has increased in importance through time, particularly in Bulgaria and Spain. Recent planting has spread it further north as well. Beech is only present in small amounts on landscapes dominated by Pinus pollen.

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