Evaluating a vegetation-recovery plan in Mediterranean alpine ski slopes: A chronosequence-based study in Sierra Nevada (SE Spain)

In this paper, we assess the results found in the restoration of vegetation on ski runs in the Mediterranean high mountain, contrasting different issues widely used for evaluating recovery plans, such as cover, richness, diversity, growth, and qualitative species composition, with the aim of establishing their relative validity as well as finding a straightforward model to assess the success of the restoration of degraded areas. Ski runs were selected in Sierra Nevada ski station (SE Spain) in which hydroseeding was performed from 2002 to 2005. The sampling design was based on a chronosequence approach, using natural areas established as 'models' (i.e. target for long-term restoration) to evaluate the restoration success based on the similarity to the model. Although parameters such as growth, cover, and even richness or diversity reached similar values to the ones in the model areas after 4 years (i.e. natural perennial mountain pastures), other indicators such as composition, measured in a qualitative way as the ratio of colonizing species to total species, showed different occurrence values for the most abundant species. Moreover, when the whole pool of species was taken into account using discriminant analysis, the results differed, showing that although the process performed well, the recovery (sensu stricto) requires longer periods than the duration assessed to be fully successful. The results showed that common parameters, such as growth, cover, richness, or diversity, when used solely may lead to misinterpretation, and therefore additional methods to compare composition, such as the discriminant analysis, are strongly recommended.