top of page

Mülibach gravel pit neophytes and maintenance work

Realized:

2019

performed by:

Naturnetz Mittelland

The Mülibach gravel pit is run by the AGIR company and is located in Ottenbach. Extensive improvement work was carried out as an ecological replacement for gravel mining and construction waste processing. In this context, shallow water ponds were created, which are now populated by many amphibians. The pit is an amphibian spawning area of national importance. The rare natterjack toad ( Bufo calamita ), for example, is found here. This is a species that used to be found primarily in river floodplains. However, as a result of water corrections in the 19th century, around 90% of river floodplains in Switzerland were lost and the toads increasingly migrated to gravel pits. They typically populate quickly warming ponds or puddles with little or no vegetation.

Another natural gem of this pit is the breeding colony of the sand martin ( Riparia riparia ), which is found on the clayey, steep slopes of the pit. Even this sparse breeding bird is now almost exclusively dependent on secondary habitats such as gravel pits, as river dams mean that hardly any natural breeding sites are created on steep slopes. These locations must be protected!

On behalf of the Nature Conservation Department, the Planikum Eco Office, together with other specialists, has drawn up the protection ordinance and maintenance plan as well as protection and support measures for the rare plant and animal species in the pit.

This year, the community service workers from the nature network carried out extensive maintenance work. This included combating invasive neophytes (goldenrod, fleabane, goat's rue, buddleia, etc.). In this context, we were also supported for the first time by goats, which grazed a large proportion of the fleabane within the pasture area. At the foot of the slope of the lean meadows, populations of flowering rush ( Sisyrinchium montanum ) were found. This is also a neophyte. However, it is unclear how invasive it really is. We have decided to combat this species next year. Other work to be carried out in spring and autumn included mowing the lean meadows (slopes), the reed meadow, and underwater mowing of the shallow water pools. The mowing work was carried out using blade bars, brush cutters, and underwater mowers. The areas were mown in stages and 20-30% of the meadow areas were left as a refuge for insects. The cuttings were left for 2-3 days after mowing so that insects had enough time to escape and the flowering plants could still produce seeds. The cuttings were then gathered together to form “Mädli” (small grasses), loaded onto a tractor and loading wagon and disposed of. In the autumn, after the flowering period of the lungwort ( Gentiana pneumonanthe ), the reed meadow near the ponds and, after the water level had been artificially lowered, the aquatic plants (mainly reeds and cattails) were mown and the cuttings were piled up to form tristen. This was not a problem because the amphibians had already left the spawning area by this time. The work was rounded off by cutting down fast-growing shrubs (pollinated willows, dogwoods, hazel, etc.) and clearing the bench by felling individual small trees using a chainsaw. The resulting wood material will be used next year (2020) to build small structures along the hedges.

bottom of page