Floodplain Forests: What Are They?
In Europe, floodplain forests are considered the equivalent of tropical rainforests. But what exactly are they? A floodplain forest is a type of forest community typically closely associated with flowing waters. These forests grow in areas near rivers and streams, within the reach of floodwaters. During floods, fertile silt is deposited on their terrain. These forests usually grow on fertile and very fertile soils, with the most typical being Holocene river alluvium. They are also found on post-bog and alluvial soils, and less frequently on brown earth or black soils. These soils are rich in organic matter, have high groundwater levels, and are most often flooded during winter thaws. The tree species found in floodplain forests include alder, willow, poplar, ash, elm, and oak. Characteristic species of floodplain communities include stinging nettle, ground-ivy, goutweed, meadowsweet, and giant fescue. These forests are known for their lush vegetation and favorable microclimate, making them an ideal habitat for many species of plants and animals. European floodplain forests are considered the equivalent of tropical rainforests due to their similar microclimate (resembling a suboceanic climate). The tree canopy allows enough light to penetrate for wild fruit trees, shrubs, and mushrooms to thrive in the lower parts of the forest. Dense undergrowth provides shelter for numerous bird and mammal species. Unfortunately, the existence of floodplain forests is threatened by activities related to riverbed regulation, water drainage, and land reclamation for agriculture.
Floodplain Forests: Microclimate as a Defining Feature
As mentioned earlier, a defining feature of floodplain forests is their unique microclimate, which is influenced by several factors. The tallest trees in a floodplain forest typically reach about 30 meters in height. This, combined with the proximity of water bodies, allows the lower layers of vegetation to flourish. The undergrowth protects the nutrient-rich soil from drying out or losing moisture. The conditions in these habitats, particularly the heavy shading in the forest's lowest parts, are ideal for plants like elderberry and wild currants. Due to the presence of ash and elm trees in floodplain forests, morel mushrooms often appear, dominating the forest floor. During the growing season, the forest floor and undergrowth are characterized by relatively high temperatures and humidity, along with shade or partial shade. The soil is fertile and moist, with the driest period being summer. As a result, floodplain forests are characterized by high biodiversity, both in terms of vegetation and the fauna that inhabit them.
There are two types of floodplain forests: lowland floodplain forests and foothill-mountain floodplain forests. The former are characteristic of lowlands and lower mountain areas. They have a diverse tree species composition, with ash and common elm dominating, accompanied by mountain elm, pedunculate oak, small-leaved lime, hornbeam, field maple, and crab apple. In some places, pedunculate oak may be the dominant species. Foothill-mountain floodplain forests, on the other hand, grow on uplands and lower mountain areas near spring complexes. They are dominated by ash, with a mix of black and grey alder, and also feature sycamore, European beech, and mountain elm.
Floodplain Forests: Distribution
Where can floodplain forests be found? The distribution of these forest communities is characteristic of all of Europe. Floodplain forests typically grow in lowlands and uplands, sometimes also in lower mountain areas (up to about 400 meters above sea level), located in valleys near larger rivers. These are generally flat or slightly sloping areas. Floodplain forests can be found in river flood zones, as well as in areas where excess rainwater or snowmelt flows down slopes.
Where Are Floodplain Forests in Poland?
Where are floodplain forests found in Poland? Like in the rest of Europe, they are primarily found in lowland areas, growing in the valleys of large rivers and their tributaries. Some of the largest areas covered by floodplain forests in Poland are found along the Oder River in the Lower Silesian Voivodeship (Oder Floodplain Forests and Riparian Forests in the Oder Valley). In addition to the lower Oder River areas, floodplain habitats can be found in the Greater Poland Lakeland, in the Vistula Valley, and in the Toruń Basin. Floodplain forests are also found in the Żuławy region.
