A forest is more than just trees: Open your eyes and ears, breathe in and feel the forest
Anyone who enjoys outdoor activities has probably noticed that Poland is home to a wide variety of forests. They affect our psyche in different ways, evoking diverse aesthetic experiences and emotions.
How do we feel in the summer in a beech forest, which scientists call Luzulo pilosae-Fagetum (acid lowland beech forest), surrounded by the deep shade cast by the trees? This shade is a godsend on a hot day, but at the same time, such a forest can evoke a certain primal anxiety, especially as dusk falls and the light begins to fade. At that time, the beech forest can be an almost terrifying place. We experience a completely different experience in spring in a forest called Potentillo albae-Quercetum (subcontinental oak forest). This type of forest seems designed to inspire joy. It resembles a park where you can wander from one flowering plant to another and admire the lush greenery. Cladonio-Pinetum (dry pine forest) offers yet another experience. The distinctive scent of pine needles is striking here and the undergrowth, dominated by lichens, creates an almost fairytale landscape. The diversity of our forests is a value in itself and a tremendous resource that is still often underestimated. And it's not just about the fashionable concept of biodiversity. It's about experiencing the beauty that forests offer us. We can't always travel to the mountains or the seaside. We can't always afford the vacation of our dreams. Meanwhile, a mindful walk through a nearby forest can become a source of respite and profound joy, brought on by the awe of the beauty that surrounds us.
How do forest communities differ?
Forest communities differ primarily in species composition – not just in the stand. Each has its own characteristic combination of species. There are plants that occur almost exclusively in a specific forest type (scientists would say: in a specific syntaxon), and plants that are also found elsewhere but are typical of the forest community being observed. Distinguishing forest communities is an art requiring knowledge and experience. However, even those not professionally involved in nature studies can easily distinguish a pine forest from an oak forest. A few walks through the forest are enough to notice that where pine trees grow, blueberries grow alongside them and where oaks grow, in spring we have the chance to see a white carpet of flowers from plants called wood anemones (Anemonenemorosa). Mushroom pickers also intuitively recognise different forest types – when they look at a forest, they can predict which mushroom species they will find there.
Where plants create patterns and trees create a roof
The plants in the forest form a unique mosaic. In the pine forest, we'll see entire patches of blueberries (Vaccinium myrtillus), called bilberries – because of the black berries we enjoy picking – but alongside them we'll see patches of lingonberries (Vaccinium vitis-idaea), with red berries. In some places, hairy wood-rush (Luzula pilosa), often mistaken for grass (you have to look closely at its inflorescences to tell the difference), will appear. Nearby, wood sorrel (Oxalis acetosella), a plant with leaves resembling clover but with a distinctly sour taste, grows. Beneath all this lies the world of bryophytes: vast carpets of common sedge (Pleurozium schreberi), and elsewhere, patches of pure papilloma (Pseudoscleropodium purum), interspersed with single shoots of the related sedge (Plagiomnium affine). A careful observer will notice that these plants do not form a uniform layer; their arrangement resembles a mosaic – more of a multicoloured carpet than a uniform fabric.
A forest is not just a mosaic of plants seen as different species growing side by side. A forest also has a vertical structure. It's easiest to distinguish four layers: trees, understory, ground cover, and the lichen-moss layer. In reality, however, this structure is much more complex. In oak-hornbeam forests – multi-species deciduous forests – tall English oaks (Quercus robur) and much shorter hornbeams (Carpinus betulus) can grow side by side. Even within the tree layer itself, variation in height is evident. In oak-hornbeam forests, in addition to oaks and hornbeams, we find maples, limes and in central Poland, even individual spruces. These trees vary in leaf shape and size, creating an openwork "forest roof." Furthermore, there are age differences: alongside tall, old trees with powerful trunks, grow young trees just entering the canopy layer. Oak-hornbeam forests are forests with a lush understory; therefore, shrubs of varying sizes grow here. And although scientists studying forest communities often lack the patience for this, it would be possible to distinguish higher and lower layers within the undergrowth. As a result, a forest is much more than just a cluster of trees! It's a multi-level and dynamic living structure.
Saving the forest's microworld
Not only is the light intensity higher in the treetops than at ground level, but the air temperature and humidity are also different, as are the wind speeds. It's no surprise, then, that organisms with completely different habitat requirements can coexist in the forest, for example, light-demanding and shade-loving species, preferring higher soil moisture and tolerant of water shortages. The forest is a mosaic of microhabitats that support countless organisms – plants, animals and fungi, including lichenized fungi, commonly known as lichens. Those who would like to see this world even more closely may be fascinated by the forest soil, where, in addition to mycelial hyphae, we find a staggering number of microorganisms.
It's not true that we scientists fully understand how a forest ecosystem functions. It's a world so complex that it's difficult to describe it exhaustively, let alone understand all the relationships between the organisms living here. Even the forest air is full of life and chemistry. In addition to the known phytoncides – compounds secreted by plants and inhibiting the development of microorganisms – there is a whole “cocktail” of microscopic particles floating in it, the composition of which depends on the type of forest and environmental conditions.
A forest that breathes diversity
Here, we return to the beginning – forests are diverse and this diversity must be protected. Intensive forest management can lead to their uniformity: in terms of species (when a single species is planted) and age (when trees are the same age). This leads to the uniformity of the forest community structure described earlier. Another problem is the very dense planting of individual trees over large areas. After a few or a dozen years, even-aged, single-species thickets (as we call such young stands) can become so dark that most light-loving plants disappear. Meanwhile, in a natural forest, there is always a sunnier spot. Such a forest "pulsates": an old tree falls somewhere and light appears, somewhere else a young generation grows densely, and even further away, old trees stand in such a loose arrangement that one can see far into the forest complex. Thanks to the coexistence of different stages of stand development, we have a tremendous wealth of habitats for the remaining forest inhabitants. Maintaining such diversity in commercial forests is difficult, and perhaps not entirely possible. Therefore, we must support foresters who strive, sometimes against economic goals, to preserve the diversity of our forests. The concept of respecting the diverse functions of forests, recognizing that they have ecological and social functions in addition to their economic function, is something guaranteed in Poland by the Forest Act of 28 September 1991.
When celebrating Forest Day, we should simply... go to the forest and seek the joy of spring.
Dr hab. Katarzyna Zielińska is a researcher specialising in plant ecology and biogeography. She conducts research on relict species and analyses their specialised ecological niches. She is a member of the Refugia and Relict Plants team, where she develops analyses of the distribution of relict plants and co-creates methods for their active conservation. As an educator, dr hab. Katarzyna Zielińska teaches classes on phytogeography, research methods used in geobotany, and taxonomic diversity of flora. She supports the development of young scientists as the supervisor of the Student Science Club for Nature Conservation. She is active in the Łódź branch of the Polish Botanical Society.
Source: dr hab. Katarzyna M. Zielińska (Department of Biogeography, Paleoecology and Nature Conservation, Faculty of Biology and Environmental Protection , University of Lodz
Edit: Kamila Knol-Michałowska (Promotion Centre, Faculty of Biology and Environmental Protection , University of Lodz)
Graphic: Mateusz Kowalski (Promotion Centre, Faculty of Biology and Environmental Protection , University of Lodz)
