Human activity, both historically and in the present day, has significantly influenced the composition of forests in the densely populated Central European region. The forests growing in Central Europe today cannot, for the most part, be considered natural, but rather as cultural landscapes shaped by humans over thousands of years.

The oldest evidence of human-forest interaction in Central Europe is considered to be the beginning of the use of axes approximately 10,000 years ago. Estimating the degree of human impact and the extent of the natural state of forests in such ancient times is complex. It is believed that during the ice age periods, Central Europe was largely deforested, and as the last glacial period — the Würm glaciation (approximately 11,700 BC) — came to an end and the forest regenerated naturally, humans began to take part in transforming the potentially untouched vegetation. Neolothic farmers living in settlements, belonging to the Linear Pottery culture, began significantly changing the forest landscape about 7,500 years ago.

Due to feudal formations, forest management and property rights were not clearly defined for many centuries, which led to large-scale 'over-exploitation' of forests. As a result, between 1750 and 1850, forests in Central Europe were destroyed, causing a serious timber shortage. Some modern sources, when speaking of this period, even mention desert-like landscapes.

In the late 19th and 20th centuries, artificial forest regeneration was carried out on a large scale.

Modern forests in Central Europe are influenced by the utility of individual tree species. Excluding a few small remnants of 'near-natural forests', the majority of Central European forests today are either artificially regenerated, or their current species composition has formed as a result of active or passive human intervention. The most common are commercial timber forests, which could be considered more or less close to natural forests [1]. For example, beech and oak or spruce and pine forests. The term 'ancient forests' in Central Europe refers to a few remaining forest stands that have not been and are not currently used for forestry.

Given the aforementioned types of human impact on forests, one must also take into account, for example, the feeding of animals on forest plants. Therefore, the composition and development dynamics of 'old' Central European forests must be reconstructed from forest research areas and natural forest sectors — after they are no longer in use, and which, compared to forest types in similar climatic conditions, are still truly primary forests, especially the Hyrcanian forest on the shore of the Caspian Sea [2].

There is almost no usable data on prehistoric megaherbivores; only assumptions exist. Many forest scientists and hunters believe that the long-lived forest structures beneficial to the forestry industry and ecology cannot be created without serious hunting measures to regulate herbivore numbers and, consequently, ensure their low density. For example, overly large deer herds, due to their selective feeding, not only economically harm the forest but also delay its natural regeneration, thereby hindering the forest's natural development.

The megaherbivore theory suggests that a higher deer density should be allowed in a certain territory, which would create a semi-open and diverse landscape. Apart from red deer and roe deer, there are no other large herbivore herds in Central Europe today, and they have few natural enemies. In the modern cultural landscape, the establishment of continuous forest is considered an economic and ecological goal, therefore herbivores that roam over large areas, causing economic losses, are hunted. Thus, the restriction of wild herbivore grazing is used as a landscape conservation tool to increase nature reserves, in which a species-diverse and partially open landscape is to be preserved accordingly; in this context, economic goals are considered secondary.

Types of forest use

In modern Central Europe, forestry and forest management dominate in terms of silviculture.

• Hunting is arguably the oldest form of forest use. Roe deer, various species of red deer, wild boar, red foxes and some smaller mammals are among the most important game species. In the past, large predators — lynx, brown bears and wolves — also belonged to this group, however, in German-speaking countries today, only very small populations of these species remain, which are also confined to very narrow territories, meaning these animals are currently considered protected. Formerly, parts of forests were maintained as hunting reserves (so-called 'wildlife sanctuary forests' (Wildbannforste)), in which only the nobility were permitted to organise hunts, so these forests may have been better preserved and perhaps resemble their original state.

• Forest grazing is an early, historical agroforestry form of forest use, where livestock were taken to graze in the forest. Depending on the frequency of this type of grazing, the forest was either thinned out or perished. Woody plants that are not easily 'eatable', such as juniper, on the other hand, spread. As a result, in the Middle Ages and the early modern period, sparse, park-like fields (clearings) and juniper heaths were created in many places. Territories with such plant communities later decreased as agriculture developed or forest areas were replanted.

• In the 20th century in Central Europe, with the emergence of a 'leisure society', recreation in forests became increasingly popular. The importance of the social functions of European forests is constantly growing and is beginning to compete with the use of the forest in its traditional sense.

• The economic outcome of the use of protection forests (Schutzwald) has a low priority. They provide additional security regarding terrain features (e.g., unstable soil), threats in the vicinity of residential objects (protecting populated areas from avalanches), habitat conservation and other ecologically significant factors, as well as serving as a gathering place. This protective function provided by the forest is considered the third most important type of forest use today, immediately after forestry timber extraction needs and hunting.

The impact of ice ages

Four million years ago, in the Pliocene period, atypically extreme climatic conditions began to appear. During the subsequent Pleistocene period, these fluctuations reached their climax in the form of several long-lasting ice ages, which ended in Central Europe approximately 12,000 years ago.

During these cold periods, the average temperature in Central Europe dropped by up to 12°C. The snow line in the Alps lowered by 1,200 metres: to an altitude of 1,400 metres. Between the Alpine glaciers and the Scandinavian ice shield, there was an ice-free strip up to 3,000 metres thick but relatively narrow.

Central Europe was not forested at this time, except for individual wooded areas in steppes and tundras, where cold-hardy birches and pines grew. The vegetation of this period is called Dryas flora, named after its representative species — the mountain avens (Dryas octopetala).

Extinction

Unlike the North American continent, where mountain ranges are oriented in a north-south direction, the east-west oriented European mountain ranges blocked the retreat of forest species as the ice shields approached. This barrier caused the extinction of several species in Europe. During the early ice ages, the horse chestnut (Aesculum hippocastanum) and sweetgum (Liquidambar) disappeared. The next cold period led to the extinction of the sequoia (Sequoia), Japanese umbrella-pine (Sciadopitys verticillata), arborvitae (Thuja), tulip tree (Liriodendron) and Douglas fir (Pseudotsuga). Hemlocks (Tsuga) and hickories (Carya) went extinct in Central Europe during the Quaternary period glaciation.

Furthermore, of the many oak species, only three — the pedunculate oak (Quercus robur), sessile oak (Q. petraea) and downy oak (Q. pubescens) were able to 'return' to Germany and Central Europe from their refugia. By way of comparison, it is worth mentioning that there are more than 80 oak species in North America. Other tree species, such as the silver fir (Abies alba), lost significant diversity during re-immigration.

Refugia

Due to climate change, forest flora was gradually pushed back. During the last ice age, refugia were most likely in Southern Europe, but they were also located elsewhere. Some species on the modern Atlantic coast between England and France could have also survived the cold period of the forest steppe. Another place of retreat was Eastern and Southeastern Europe. Unlike Scandinavia and Russia, the Carpathians remained free of an ice sheet, so some species were able to survive there. However, the Mediterranean region remained fundamentally the most important refuge, where the proximity to the sea ensured a balanced climate, and rugged mountain ranges enclosed the surviving plant populations.

Re-immigration

Species that avoided extinction gradually recovered in the respective regions during interglacial periods. Re-immigration occurred at different paces for different tree species. Determining factors for the speed at which tree species re-established themselves in 'former' areas were, for example, the method of seed dispersal, flowering duration, frost resistance and the plants' ability to absorb nutrients. The re-immigration pattern can be reconstructed using the pollen analysis method.

The so-called pioneer tree species, such as birches and pines, which were able to spread quickly, 'stood out' the most in terms of speed. Heat-loving species, such as oaks, were the next 'most agile'. Finally, they were followed by the slower, migrating species. As the interglacial period ended and colder climatic conditions set in, these species retreated to their refugia or simply died out.

The most recent post-glacial period

In the most recent phase of the Quaternary period, the Holocene or post-glacial period approximately 11,700 years ago, forests began to return to the open post-glacial steppes. The results of pollen analysis have largely clarified the process of this re-immigration. Ten phases of this process were identified in Central Europe (based on the theory of Franz Firbas), which are referred to as pollen zones and are numbered with Roman numerals, as parts of the Blytt-Sernander scheme.

In more recent research work, individual pollen zone classification schemes are increasingly used to more accurately reflect conditions in different locations. The forest regeneration process is consistent on a fairly large scale, however, due to local conditions, there are some regional peculiarities. Because of migration speeds from south to north (e.g., for the beech, it is about 260 metres per year), there is often a temporary delay in the determination of the various phases of the migration process.

Late Arctic period, Allerød and Younger Dryas period

This time refers to pollen zones with sequence numbers I–III (approximately in the time period from 12,400 BC to 9,500 BC) and roughly corresponds to the Late Palaeolithic period. Although various willow (Salix) species belonged to the pioneer plant species in the early post-glacial period (Holocene), birches (Betula) and pines (Pinus) managed to regain stable positions in Central Europe. However, brief temperature fluctuations at the end of this period halted any further forest development.

Pre-interglacial (Preboreal) and early interglacial stage (Boreal)

In the Preboreal stage, which coincides with the beginning of the Mesolithic, birch and pine became the dominant species. Since then, new freezing periods did not follow. Hazels (Corylus) spread rapidly, finding favourable growth conditions under the branches of pines.

Middle interglacial stage (Atlantic period)

At the end of the Middle Stone Age, the average air temperature increased significantly. Phytosociologically, this time is considered the beginning of the Atlantic period. Earlier tree species were replaced by others, such as oak (Quercus) and elm (Ulmus) species. Most of these species were demanding regarding the necessary nutrients and heat. Shade-intolerant pines were pushed to sandier locations with poorer soil, as well as to heaths. At that time, the dominant stands in Central Europe began to be formed by oaks, elms and limes, creating mixed deciduous forests.

During this time, people transitioned from nomads and wanderers to the farming society characteristic of the Neolithic with permanent settlements. In the mightier settlements of the Linear Pottery culture, the demand for timber increased, which created great pressure on the still limited forest resources. By the beginning of the Neolithic, forests were already being intentionally managed for timber production. [3]

During the Neolithic, several heat-loving shrub species spread from Southern Europe to Central Europe. The existing flora was also supplemented by maples (Acer) and ashes (Fraxinus). During this time, the average air temperature was 2–3°C higher than it is today. The downy oak (Quercus pubescens) returned to German territory. Above marshy depressions, alder (Alnus glutinosa) forests or alder carrs formed, and Norway spruce (Picea abies) reached the Harz mountains.

Late interglacial stage (Subboreal)

In the late interglacial stage, climatic conditions became colder and wetter. For the first time since the last ice age, European beeches (Fagus sylvatica), European hornbeams (Carpinus betulus) and silver firs (Abies alba) appeared.

In the Bronze Age, the average air temperature fell further. Beeches retreated to forests that had until then been formed mostly by oaks. In the Iron Age, in the period from 1000 BC, beeches threatened to suppress oak stands almost everywhere. Thanks to Central Europe's humid maritime climate and the beech's ability to supplement its habitat even at a great age, the beech became the dominant tree species. In drier locations (with rainfall below 500 mm/year) to the east, the European hornbeam became the dominant tree species.

As beeches gradually occupied mountain territories, mixed deciduous forests formed in the Central Highlands. Shade-tolerant silver firs also managed to occupy the foothills of these forests, sometimes even displacing Norway spruce and beech from their usual conditions. However, it is possible that it was precisely during this time that the opportunity for the creation of potentially untouched vegetation disappeared, as human settlements in the territory of Central Europe continued to expand and large herds of herbivores continued to roam the surroundings.

Post-interglacial period (Subatlantic period)

The drop in average air temperatures divided, for example, the distribution areas of the downy oak. This is the moment when the impact of populated areas on forests became increasingly noticeable. The vegetation zones known today began to emerge, the origin of which is influenced by altitude zones. (To be continued)

*translation from German
1. Helge Walentowski, Susanne Winter (2007): Naturnähe im Wirtschaftswald – was ist das? Tuexenia 27: 19–26
2. Reinhard Mosandl: Geschichte der Wälder in Mitteleuropa im letzten Jahrtausend. Aktuelle Beiträge zum Verständnis der historischen Entwicklung. In: Bernd Herrmann (Hrsg.): Beiträge zum Göttinger Umwelthistorischen Kolloquium 2008–2009. Universitätsverlag Göttingen, 2009, S. 91–114. Vorschau bei Google Books
3. Nils Bleicher: Altes Holz in neuem Licht. Archäologische und dendrochronologische Untersuchungen an spätneolithischen Feuchtbodensiedlungen in Oberschwaben. Dissertation, Mainz 2007. Materialhefte zur Archäologie in Baden-Württemberg, Stuttgart 2010.