Pioneer communities of open gravel plains

04.12.2023 Thomas Wagner 3 min read

Sparse pioneer vegetation can be found on the occasionally still overturned gravel areas. Plant cover is low, and the individual plants are scattered and widely spaced. The gravels are not decalcified, the soils are shallow and undeveloped. Plant species found here are adapted to the nutrient-poor and often unstable situation. The vegetation consists of mainly herbaceous plants, often rosette- or cushion-forming, grasses, and low shrubs, occasionally interspersed with the young growth of pioneer tree species such as black poplar (Populus nigra) or willow species (Salix eleagnos or others).

Characteristic pioneer species include mountain avens (Dryas octopetala), the today rare alpine Chondrilla (Chondrilla chondrilloides), or the heart-leaf globe daisy (Globularia cordifolia). Some species of the Magredi are endemic and only found here or in the surrounding area and similar ecosystems, such as Kerner’s spurge (Euphorbia kerneri) or the bicolored knapweed (Centaurea dichroantha). In addition to vascular plants, there are various species of mosses and lichens. However, invasive grass and shrub species are also increasingly found here. Although these pioneer communities can hardly be used for agriculture due to the low productivity of the soil, their area has been considerably reduced to date due to hydraulic engineering measures and gravel mining.

Credits: Thomas Wagner — Dyras octopetala

Magredo primitivo: Calcareous grasslands on fluvial gravel

The Magredo primitivo, a calcareous grassland, is found on higher terraces with occasionally flooded or groundwater-influenced sites with weakly developed soils on fluvial gravel.Carbonate leaching and the decomposition of plant material by bacteria and fungi form a thin layer of soil that retains water better and has a higher nutrient content. This allows the occurrence of more demanding plant species and a much more dense vegetation than the fluvial gravels. In addition to the common dwarf sedge (Carex humilis), grasses such as brush grass (Chrysopogon gryllus), furrowed fescue (Festuca stricta ssp sulcata), meadow brome (Bromus erectus) or the conspicuous European feather grass (Stipa pennata) dominate. Typical herbaceous species are common ballflower (Globularia bisnagarica), branched toadflax (Thesium rostratum) or salad burnet (Sanguisorba minor). Beside these, there are also dwarf shrubs such as creeping broom (Cytisus pseudoprocumbens) and various smaller shrubs and trees such as willows (Salix eleagnos) or … Although the Magredi primitivi are not intensively used or managed today, they are occasionally used for transhumance with sheep.

Evolved Magredi grasslands

As the soils develop, the Magredo primitivo turns to Magredo evoluto on soils with a higher proportion of fine soil, more nutrients and better water capacity. Here, the plant cover is dense, the vegetation dominated by grasses, and numerous herbaceous species and perennials, including species that are often rare today. Flooding occurs very rarely here and only during severe floods. River dynamics are now replaced by anthropogenic disturbances such as mowing and grazing.

During the relatively wet early summer, the vegetation of the Magredi evoluti is most developed, and the Magredi meadows form a sea of different flowers. With almost 100 plant species per hectare, the Magredi meadows are among the most species-rich habitats in Europe. In the summer, the Magredi meadows are hot and dry. Many plant species are, therefore, adapted to high light intensities and temporary drought.

The floral abundance and high diversity of the Magredi meadows is also reflected in a diverse fauna. It is assumed that each plant species supports 8-9 animal species and, in addition, an even greater number of mushroom species.

The productivity of the Magredi meadows is comparatively high at around 2.5 tons of dry hay per hectare, and the grasses have a high grazing quality. This makes the Magredi evoluti attractive for litter mowing and grazing. This use, which has been practiced for centuries and continues to this day, prevents the growth of trees and avoids scrub encroachment. As a result, only isolated trees or small groups of trees can be found interspersed in the vast grasslands.

In addition to the dominant grasses brush grass (Chrysopogon gryllus) and meadow brome (Bromus erectus), there are perennials such as meadowsweet (Filipendula vulgaris), mountain parsley (Peucedanum oreoselinum) and numerous orchid species, including Green-winged Orchid (Anacamptis morio), Dark-winged Orchid (Neotinea ustulata), toothed Orchid (Neotinea tridentata), Long-lipped Serapias (Serapias vomeracea), Long-leaved Helleborine (Cephalanthera longifolia), Greater Butterfly Orchid (Platanthera chlorantha), Fragrant Orchid (Gymnadenia conopsea) and Bee Orchid (Ophrys apifera).

There are also numerous endemics, such as cluster head pink (Dianthus sanguineus) or the endemic widow flower Knautia velutina.