Gradual shifts

In other locations, vegetations of Calluna vulgaris, Erica tetralix or Andromeda polifolia that have become increasingly shaded are taken over by Empetrum nigrum, Vaccinium vitis-idaea or V. myrtillus. One vegetation aspect silently transforms into the next. On a spot where Vaccinium macrocarpus has been growing for over 30 years, with a mat of mosses and stems as thick as 10 cm, Gentiana pneumonanthe, which formerly flowered there by the thousands, is gradually disappearing completely. It does not tolerate the competition of the thickening moss-and-stem mat and is pushed out. Long before this stage is reached, Empetrum nigrum, Erica tetralix and Calluna vulgaris have established themselves, in addition to the usual unwanted species. It is hard to remove them from the vegetation mat: deep mowing in early spring, which is tolerated well by Vaccinium macrocarpus, removes Empetrum nigrum but not the other two species. A phased combination of weeding and mowing may offer a solution.

Climatic influences are very important for a vegetation of Ericaceae. Wet years with a high humidity favour its development, whereas dry hot years impede it. This obviously applies to other vegetation types in a similar way. One therefore discerns ‘Ericaceae years’ and ‘Rosaceae years’, the former being the wet years and the latter years with little rain and low humidity. In dry years, the development of Vaccinium vitis-idaea stagnates; it withdraws, the vegetation’s size decreases. The resulting open spots may be left to other suitable species, self-seeding there because they are more drought-tolerant, for example Genista germanica, Arnica montana, Campanula rotundifolia and Jasione montana. When wetter times arrive, Vaccinium vitisidaea reclaims these spaces by sending out its shoots. This may be stimulated by trimming and cutting back its competitors.

As long as the park’s aspects with its vegetation remain attractive, one may continue working in the same vein. If not, one has to renovate parts of the park completely, with measures consisting of lifting, digging, applying fresh sand or peat where required, planting out pre-raised plants and sowing out others. Another round starts, the clock of succession has been turned back as an element of dynamic creative management.