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blossoming - since 1983

1. Principles

In a condensed version, the below article describes technical - mechanical procedures for establishing vegetation on problematic and severe sites and protecting them against erosion. The target of extreme site revegetation is the quick establishing of a dense, permanent vegetation suitable to the respective site in an area, which without adequate measures would remain without permanent vegetation for a long time. Several specialized seeding and bioengineering techniques are available for restoration and erosion control on such areas.

Sites without sufficiently dense and well-rooted vegetation are exposed to various forms of erosion (by water) and deflation (by wind). In extreme cases, entire slopes begin to slide and may bury roads and even buildings and residentials. At first, soil layers close to the surface benefit from the effects of revegetation, as the root system of the vegetation to be established effectively protects those layers against erosion. With slopes and acclivities, which - due to menacing landslides or a particular hydrological situation - need additional reinforcement including deeper soil layers, bioengineering techniques are applied. Those include the use of especially deep rooting plants (e.g. groves) and/or appropriate constructions with deeper penetration. In certain cases, even inanimate, but natural components may be used.

This ensures a lasting, dynamical and ecological reinforcement of especially sensitive and endangered sites.

The utilization of the restoration method, which for the respective site is the most effective, and the combination of methods complementing one another result in a multi-functionality which cannot be valuated enough: soil protection and erosion control, landscape aesthetics, ecology, nature conservation and environmental protection as well as leisure and local recreation similarly benefit from professional restoration.

The Major Tasks of Establishing Vegetation on Problematic Sites:

    •  establishing of a site-adapted and permanent vegetation cover
    •  erosion control
    •  soil amelioration 
    •  optimization of the stability of the earth and landscape constructions
    •  reduction of ecological damage caused by interferences in nature and landscape
    •  integration of sites into the landscape
    •  linking and connection of ecosystems, creation of buffer areas and habitats for flora and fauna 
    •  creation of recreational areas

    Here, the Following Principle Applies:

    For establishing vegetation on problematic sites with machines, it is important to select the respective adequate method and the required additives under consideration of the respective site conditions.

    Prerequisites of successful revegetation are the knowledge and consideration of the given soil and site conditions:

    With increasing site problematics, the procedures for the establishing of vegetation and for bioengineering get more complicated, more complex and more expensive. Sites with low space for roots (e.g. rocky soils with only a thin loose layer), poor in clay mineral and organic matter (raw soils), low soil-pH or strong slope inclination (steep slopes) demand for specific seed mixtures and hydroseeding recipes especially rich in components. To be able to select all components adequately, an as comprehensive as possible analysis of the site is necessary.

    Restoration procedures and operation methods of bioengineering are successful only, if plants and components are optimally adjusted to the respective site conditions.

    The biggest erosion damages are usually caused by runoff water. Thereby, soil particles are dissolved and moved down the slope, the water acting as transportation medium. Water can act especially agressively in places, where it cannot drain away quickly enough, but flows down the slope and meets easy-to-solve soil particles. This is why coarse-grained soils like e.g. sand and gravel as well as coherent soils (clays) are less endangered by erosion. It is not only precipitation water, but also spring and slope water, which again and again cause slips, massive depression and rift erosion. Such site conditions demand for project-individual and partly very specific measures.

    Incidental surface and spring water as well as leaking seepage water ought to be drained off as comprehensively as possible.

    The threat of soil erosion is prevented by largely withdrawing the soil's surface from the attacks of water or wind applying appropriate surface forming.

     

    Preconditions for this are, for example

    • a flat structuring of slopes and landscape constructions;
    • the rounding of slope tops and other hard contours;
    • the creation of a rough soil surface with vivid micro-relief;
    • the creation of structures parallel to the slope, when preparing the soil (following the principle of "contour farming");
    • the elimination of wind cones in areas with sites endangered by winds.

    Here the Following Principle Applies:

    Only a procedure, where the techniques of earth moving are adapted to the soil conditions, and a correspondingly adjusted reliefing of the problematic area ensures a successful, permanent protection against erosion by establishing vegetation.

    Establishing of vegetation on raw soils poor in humus generally requires considerably higher efforts than seedings on topsoil. Mainly sites with low nutrients and often coarse soil texture, but also microbial sterility make establishing vegetation in such sites a challenge. If then problematic pH-values are added (extremely high values like e.g. with ashes, clinkers, building rubble, or extremely low values like with pyrite-containing tertiary sands) a complete measurement catalog of melioration measures is to be considered to allow the growth of a permanent and vital vegetation.

    From the view of professional aspects, raw soils are to be preferred to topsoil coverings, as they show better medium and long-term results in what concerns erosion control, ecology and aesthetics. Topsoil coverings frequently result in strict separating layers between topsoil covers rich in nutrients and sterile deeper soils, which are not or only insuffienctly penetrated by the root system. This leads to an only flat root system causing high susceptibility to droughts as well as reduced slope reinforcement.

    Spontaneous vegetation, sometimes also called "undesired uncontrolled growth" or "weed growth", often provides precious hints on the quality of the site as recultivation or seeding area. As indicator plants for site conditions like light, temperature, climate, humidity, soil reaction and trophy, they frequently render elaborate site analyses dispensable. On the basis of the respective spontaneous vegetation, a complete hydroseeding recipe may be developed sometimes.

    The time, when realizing restoration measures, may have a considerable influence on the revegetation method and the composition of the grassing recipe. For example, measures for the improvement of the soil water retention capacity are considerably more important with spring and summer seedings than with seedings in autumn, while the application of quickly available, water soluble fertilizers at the end of the vegetation period does not really make sense. Additional erosion control measures - e.g. increased amounts of tackifiers, addition of mother crops - are particularly important, if the period between seeding and germination or the development of the vegetation is extremely long, e.g. with measures in the late autumn (limiting factor: temperature) and in early summer (limiting factor: water).

    Only the knowledge of all vegetation-relevant site factors permits an optimal adjustment of the recultivation procedures and techniques to be applied to the conditions in site. Our long-term experience in the most differing sites all over Germany and Europe enables us to evaluate many projects without inspection of the area but corresponding to the site, so that developing an adequate technical procedure and a seeding recipe suitable to the respective site is possible without any problem.

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