Research on meadows cenosis and its ecological restoration is particularly advanced in the Alpine area and, at least in Trentino, now implemented at a large scale . The restoration process takes place in four phases: (1) choice of the donor site; (2) collection and preparation of the seed or propagation material in different forms (green grass, hay, hayseed from brushing machines or combine harvesters); (3) distribution of the material on the receiver site; (4) evaluation in retrospect of the success or failure of the process (Table 1).
The choice of the donor site must necessarily consider the (local) seed origin, its floristic composition, fertility and availability. This requirement is particularly important to favor a sustainable evolution of the vegetation. Especially in environments with adverse soil and climate features and where local conditions are therefore prohibitive for the establishment of non-native species, the choice of local native seed varieties is the only solution.
In the last decades, some central European markets have moved in this direction, with Swiss, Austrian and German farmers and cooperatives specializing in the production of native seed mixtures. This, however, has not happened in Trentino or Italy in general, where the collection and selection of seeds from existing semi-natural meadows remains one of the few viable restoration methods. Additionally, this method is often the only effective one in environments with a high species and vegetation diversity .
Seeds are collected directly from the standing plant or through a seed bank. In both cases, the following factors must be carefully considered: the quality and quantity of the stems or seeds in the soil, the morphology and phenology of the plants, the availability, distribution in the soil and in-plant production of the seed.
Similar steps are followed when seeds are collected manually and then propagated with agricultural production techniques. Yet, there are some differences between direct collection and distribution on the receiver site, and the method involving agricultural production. Indeed, production time requirements lengthen the restoration process by some years because seeds must be propagated through several generations. Nonetheless, the total cost of a restoration process involving farming production is lower and is, today, the most cost-efficient method for large-scale ecological restoration of species-rich meadows. A combination of the two methods is often useful because not all species can be easily propagated with farming techniques and not all the desired species can be easily found and collected from the field.
The seed distribution phase at the receiver site ends the restoration process. Again, traditional agricultural techniques such as mechanic or manual seeding can support the process.
To properly evaluate the restoration process, the receiver site geography, climate and soil condition prior to the restoration must be characterized and the restoration objectives clearly defined. For a successful meadow restoration, the receiver site soil must be tilled to decrease the competition between the introduced seeds and the existing grass species, fertility must be reduced, when necessary, soil must be decompacted, and safe sites must be created, where possible.