The Białowieża Forest contains the last remnants of old-growth forests in the North European Plain. The forest is predominantly composed of deciduous and mixed forests. A notable trend observed in the Białowieża National Park is the decline of Scots pine in favor of deciduous species.
The forest is home to 26 species of trees, excluding those cultivated by humans in parks. Among these, the pedunculate oak stands out for its size and age, while the tallest tree in the forest is a spruce. However, the yew has disappeared from the forest, and the European silver fir is considered a threatened species. Conversely, human activity has introduced new tree species to the area.
The forest stands in Białowieża Forest form extensive tracts of natural woodland, exhibiting significant species diversity depending on the habitat. Human intervention and forestry demands have historically altered the proportions of certain species. Monospecific stands, mainly found in coniferous forests, are the result of afforestation efforts during the interwar and post-war periods.
Calls for the protection of the forest arose almost simultaneously with the onset of its industrial exploitation. The first nature reserves were established in 1921. The Białowieża National Park was created in an area that was never subjected to industrial exploitation, with minimal human impact throughout its history.
Natural history of the Białowieża Forest
The flora currently found in the Białowieża Forest gradually developed as a result of plant migration from unglaciated areas, influenced by climatic changes and the formation and transformation of soils. Initially, plants arrived from the south and west, later from the north and east. Heavy-seeded tree species (oak, linden, hornbeam) were unable to colonize treeless areas and could only appear once light-seeded species (birch, pine, aspen) had already forested the area, creating the right ecoclimate and soil conditions for more demanding species. The seeds of these trees were carried by birds.
It is estimated that during the period of partial climatic warming (10–9 thousand years ago), pine-birch forests appeared in the area that is now the Białowieża Forest. Pine was the dominant species, with birch as a secondary species. Alder appeared rarely along river alluvium, and by the middle of this period, the first spruces and hazels emerged.
The pine-birch forests later retreated due to a cooling climate during the Younger Dryas (9000–8250 BCE). These changes mainly involved a reduction in forest area and a significant increase in the role of birches and herbaceous plant communities dominated by true sedges.
Pine-birch forests returned during the Preboreal period (8250–6750 BCE), giving rise to the forest formations in the geographical area now known as the Białowieża Forest. Birch was the dominant species, but its dominance was short-lived. Gradually, hornbeam, elm, and linden appeared, along with hazel, forming the beginnings of mixed forests. This led to the retreat of pine-birch forests. Later, during the Boreal period (6750–5500 BCE), the role of birch diminished while pine spread extensively during the Holocene. Maple appeared during the Boreal period, and spruce arrived during the Subboreal period, around 2500–500 BCE. The current forest types were formed around 500 BCE.
During the Atlantic period (5500–2500 BCE), the proportion of deciduous forests increased. In the Subboreal period (2500–500 BCE), the climate cooled and became more humid. The proportion of pine and mixed forests likely remained unchanged, but spruce joined their composition, and the role of oak slightly increased. During the Subatlantic period (500 BCE–60 CE), the proportion of elm, oak, and linden decreased, and hazel significantly declined in the forest understory. Additionally, the role of alder decreased due to the lowering of groundwater levels. The cooling climate favored the spread of spruce.
The final stage of the formation of the Białowieża Forest's flora involved not so much the migration of new species, but rather the partial or complete extinction of warm-loving species. As spruce and the forest floor vegetation, which thrives in cooler temperatures, spread, the flora became impoverished.
Current forest types
Classification
Various types of forests have been distinguished in the Białowieża Forest. In 1559, G.B. Wołowicz used the terms grud, oles, jełosmycz, bór ljago, and bór bagno to describe different forest types. These terms had long been used by the local population. The term grud (now grąd) referred to deciduous forests dominated by hornbeam, maple, elm, and linden. The term jełosmycz referred to spruce forests, oles to forests with a predominance of alder and ash, bór ljago to pine forests, and bór bagno to coniferous swamps.
Jan Jerzy Karpiński identified seven forest types in the Białowieża Forest: pine forest, pine-spruce forest (or coniferous forest), pine-spruce-oak forest (or mixed forest), coniferous swamp, fresh deciduous forest (or highland hornbeam forest), moist deciduous forest (or lowland hornbeam forest), and alder-ash forest (or alder carr). In the managed part of the forest, human activity has altered the natural proportions between forest types, though these have remained largely intact within the Białowieża National Park. Additionally, this depends on soil fertility. The dominance of deciduous trees stems from the fact that fertile habitats dominate in the central part of the forest.
proposed a different classification based on four classes of forest communities:
Deciduous and mixed forests Coniferous forests, i.e., pine forests Wetland forests and thickets, i.e., alder carrs Willow riparian forests (Łęgi Wierzbiowe)
According to Faliński, the Białowieża Forest is primarily made up of hornbeam forests and mixed pine forests. Hornbeam forests make up 47.2% of the managed part of the forest and 44.4% of the Białowieża National Park, while mixed pine forests make up 26.5% of the managed area and 20.4% of the Białowieża National Park.
Deciduous and mixed forests
The hornbeam forest occurs in two variants: highland hornbeam forest and lowland hornbeam forest. The highland hornbeam forest (or fresh forest) occurs on clay soils with a linden admixture, covered with a thick layer of humus, with weak influence from groundwater. The tree stand background consists of oak and spruce, with linden, larch, aspen, maple, and hornbeam present as admixtures. The most common components of the groundcover are: wood sorrel, wall lettuce, common hepatica, greater stitchwort, bugle, common hemp-nettle, mountain melick, wood anemone, false lily of the valley, and finger sedge. The understory includes hazel, spindle, honeysuckle, buckthorn, dogwood, rowan, alpine currant, and elder. This forest type is widespread in the Polish part of the forest and in the Białowieża National Park.
Lowland hornbeam forest, also known as moist forest, grows on chalky deposits overlaid with fertile, moist sands and clays. Its canopy is less dense than the highland type, but it features larger hornbeams and more oak and linden. Elm, ash, common alder, downy birch, and aspen are occasional additions. The groundcover includes yellow archangel, sweet woodruff, greater stitchwort, wood sorrel, yellow loosestrife, Carex sylvatica, bugle, and lady fern. The understory contains alder buckthorn, elder, red elderberry, blackcurrant, Viburnum, bird cherry, dogwood, and spindle.
Hornbeam forests in Białowieża National Park's strict reserves are particularly stable due to minimal human interference. Species proportions shift naturally without any species showing signs of decline. These forests exhibit unification processes, potentially reflecting regeneration after past human pressures.
Light oak forest features a canopy dominated by pedunculate oak, with minor contributions from aspen, hornbeam, and linden. It has a park-like appearance with sunlight reaching the ground layer, supporting a richer and more diverse flora than other forest types. Warmth-loving plants more common in southern and eastern regions dominate, while the understory is sparse, including hazel, scattered hornbeam, and Euonymus verrucosus. The groundcover contains Potentilla alba, Ranunculus polyanthemos, wood cranesbill, yellow foxglove, peach-leaved bellflower, bristly bellflower, Kashubian vetch, narrow-leaved lungwort, mountain sedge, white swallow-wort, bastard balm, Lathyrus laevigatus, black pea, Dracocephalum ruyschiana, stemless carline thistle, and various clovers. The moss layer is sparse.
Some historical oak forests were replaced by settlements, such as the Palace Park in Białowieża, once the site of an oak forest, and nearby villages that replaced hornbeam forests. Gravel pits created during the 20th century further reduced the extent of these oak forests.
Coniferous forests
Fresh coniferous forest occupies dry, fresh sands, with no significant influence from groundwater. The dominant tree is pine, with birch and spruce occurring as minor admixtures. Characteristic species in the groundcover include red-stemmed feathermoss, lingonberry, common heather, and broom forkmoss. The understory consists of juniper, rowan, and oak.
Moist coniferous forest occupies moist sands. The dominant trees are pine and spruce, with birch as a secondary species. The understory includes alder buckthorn, rowan, juniper, and shrubby willows. Characteristic groundcover species include European blueberry, red-stemmed feathermoss, lingonberry, , and glittering woodmoss. Differentiating species compared to the fresh coniferous forest are bog bilberry, marsh Labrador tea, purple moor-grass, and flat-topped bogmoss.
Bog coniferous forest occurs in swampy depressions and hollows lacking water drainage. The terrain is hummocky, with hollows filled with water between the hummocks. It is dominated by stunted pine, with downy birch as a rare admixture. The role of downy birch is minimal. The understory is sparse and primarily consists of pine regenerating naturally in abundance, occasionally accompanied by downy birch and common sallow. The groundcover is species-poor and mosaic-like, comprising peat mosses, reed grass, cottongrass, cranberry, bogbean, and other plants typical of swampy peatlands. Among shrubs, shrubby birch, a glacial relict, occurs. Its seeds are not dispersed by the wind but are carried by water from melting snow during the early spring thaw.
Mixed coniferous forest occurs in relatively nutrient-poor habitats with acidic soils. Floristically and ecologically, it relates to both deciduous and coniferous forests. The dominant species is generally spruce, while pine, although consistently present, plays a minor quantitative role. Two types of mixed coniferous forests are distinguished: fresh mixed coniferous forest and moist mixed coniferous forest. The first type features deep or moderately deep groundwater and benefits from short periods of soil and rainwater. The second type occupies mineral soils under moderate or relatively strong influence from groundwater or soil and rainwater. Fresh mixed coniferous forest is formed by pine and spruce, with oak, larch, and birch as admixtures. The understory consists of juniper, rowan, honeysuckle, hazel, buckthorn, and spindle. The groundcover is diverse, with frequent components including European blueberry, red-stemmed feathermoss, glittering woodmoss, chickweed-wintergreen, hairy wood-rush, and others.
The tree stands of moist mixed coniferous forest consist of spruce and pine, with oak, birch, and aspen as secondary species. The understory features buckthorn, shrubby willows, hazel, rowan, and juniper. The ground layer is mainly composed of European blueberry, purple moor-grass, sphagnum moss, chickweed-wintergreen, red-stemmed feathermoss, glittering woodmoss, hairy wood-rush, bog bilberry, and marsh Labrador tea.
Alder carrs