The results of restoration efforts have been characterized as notoriously unpredictable. Many variables impact the trajectory of communities towards recovery, and ecological theory that takes traits, habitat configuration, and scale into account, can improve models. However, the most important questions regarding the predictability of species community restoration may be related to stochasticity. We investigated the assembly of a cyanolichen community in a chronosequence consisting of 88 new forest patches (30-140+ years old) comprising today 0.4% of a 170 km2 former treeless heathland area in south-western Norway. Two complete inventories were carried out 12 years apart, and we (1) tested inferences on colonization status and recovery time based on the first inventory only, (2) investigated the recovery of the lichen community by changes in species richness, species density, and composition at three different spatial scales, and (3) discussed how dispersal capacity and stochasticity affect community recovery in general. Colonization of sites by lichen species exceeded extinctions in young sites but not in old sites, and in the second inventory, the richness of species weighed by occurrences no longer differed significantly between young and old sites at landscape scale. However, the differences between old and young sites depended on the spatial scale and method of measurement. In accordance with inferences based only on the first inventory, colonization and extinction dynamics indicated that recovery of species richness in our study system will take 90-120 years at the landscape scale, whereas recovery of species composition was difficult to determine due to idiosyncratic development among sites.

Synthesis and applications. Using species composition as a template for the evaluation of restoration recovery in systems with a high degree of stochastic colonization and extinction is problematic, particularly at finer scales. Ideally, comparisons of restoration and reference communities should therefore be at large enough spatial scale to cancel out the major effects of stochasticity at finer scales. Furthermore, we suggest that a complete recovery of species numbers may not be needed as an indicator of restoration success if species richness measurements indicate that communities are en route to recovery.