Comparison of Seed Mixtures for Technical Revegetation at High Altitude

With the aims of improving the success of sowings, enhancing the biodiversity, and reducing the impact of interventions (both in terms of energy input and genetic pollution), the use of seed mixtures including ‘site-specific’ species is increasingly recommended for revegetation interventions at high altitude. This germplasm is ecologically adapted to the prevailing pedoclimatic conditions and native to the target region. In this three-year study performed in Alpe Palu (Chiesa in Valmalenco, Sondrio, Italy) at 2,020 m a.s.l. elevation, ground cover and botanical composition of native seed mixtures were compared versus those of commercially available mixtures. Both a simpler and a more complex version (with greater number of species) were evaluated for both native and commercial mixtures. The commercial mixtures colonised faster the bare soil in the year following the sowing, but in the subsequent years the native mixtures reached over 80 % of ground cover being no longer different from the former ones. The complexity of mixture had only slight effects on the soil cover. A relative prevalence of grasses was evident in the commercial mixtures, and of non-legume dicots in the native ones. The better botanical balance featured by the native mixtures is likely to result in a more-lasting stability of the covers and an increase of biodiversity in the long term.