Summary 1.The balance between facilitation and competition through time is at the core of models for successional dynamics. However, since the 1980s, the studies of facilitation have shifted away from successional processes. In a return to the traditional roots of the study of facilitation, we assessed the phylogenetic signatures of competition and facilitation in Mediterranean successional communities and compared them with those recently quantified in non-successional communities of the Mexican desert. 2. Based on previous work, we hypothesized that facilitation between distantly related lineages is an important driver of successional dynamics, as has been shown in non-successional systems. However, we also predicted that the balance between facilitation and competition will be different in successional systems because many species disappear from communities during the process of succession, which does not occur in non-successional systems. 3. We sampled plant species composition over a chronosequence of post-fire succession and predicted phylogenetic clustering in communities at the early stages caused by species that reproduce by seed ('seeders', belonging to a few specific families) being favoured by fire; overdispersion in intermediate stages driven by facilitation interactions among distantly related species; and randomness in the final stage caused by the competitive exclusion of pioneer species belonging to a few families and the survival of species in many other families. 4. In the pioneer stage, we found a random phylogenetic pattern because seeders and many resprouter species were present at this stage, indicating that autosuccession was also occurring. In intermediate phases, once pioneers had recruited into open spaces and facilitated late-successional species, most of which were ancient taxa originating during the Tertiary, phylogenetic overdispersion predominated. Finally, in the later stages competitive exclusion of pioneer species reduced phylogenetic diversity, leading to a random phylogenetic structure. 5. Synthesis. As previously found for non-successional communities, facilitation among distantly related lineages appeared to drive successional dynamics. However, subsequent competition reduced phylogenetic diversity during succession in this Mediterranean system, and some species disappeared from the community.

Summary 1.Based on short-term experimental data, facilitative interactions between woody plants (nurse-recruit interactions) have been described as essential for the restoration of Mediterranean forests. However, the long-term effects of nurse plants on vegetation dynamics are unknown. This study aims to project post-fire vegetation dynamics from easily retrieved data, and to asses the long-term contribution of nurse plants to forest restoration. 2.In an area burned 20 years ago, we compared post-fire dynamics in three states of regeneration: pioneer scrubland; spontaneous pine regeneration stands; and late successional scrubland. For each regeneration state, we obtained an interaction matrix with the frequency of recruitment of a given species under the canopy of every other species in the community. These matrices provided the raw data to develop Markov chain models of community dynamics. We used sensitivity analyses to explore how small shifts in replacement probabilities between species (or between functional groups) may affect the similarity of the projected community to an undisturbed reference community. 3. Plots in the pioneer state had the lowest frequency of facilitative interactions. Matrix projection showed that, under the current frequency of facilitation, these pioneer scrublands would remain so in the long term. By contrast, the building state had the highest frequency of facilitation, and its projection suggested that it should reach a steady state very similar to the reference community. These results confirm that nurse facilitative effects are fundamental for a secondary successional trajectory of the post-fire dynamics. 4. Sensitivities showed that secondary succession may be launched in the pioneer state by increasing the frequency of seedlings of tall shrubs, evergreen and deciduous trees under small shrubs. 5. Synthesis and applications . Our Markov chain successional model is an analytical tool which can be applied rapidly and easily to determine successional trajectories for forest restoration. It allows: (i) evaluation of post-fire dynamics and identification of areas in need of intensive intervention (i.e. where secondary succession remains arrested leading to stasis in the pioneer state); (ii) assessment of the role of long-term facilitative nurse effects on restoration; and (iii) identification of species-pair combinations and functional nurse groups of value for further planting efforts.

Summary1. Many restoration projects aim to transform degraded vegetation into mature native plant communities. The recovery of the structure and properties of reference native plant communities is acknowledged as a landmark of restoration, and the success of restoration practices is measured in terms of community metrics. Nurse-assisted planting has been proposed as a promising technique for the restoration of Mediterranean and arid vegetation based on its success at seedling establishment rather than on the recovery of reference community properties. We investigate the adequacy of this restoration practice by shifting the focus of restoration from the species to the community level. 2. In contrast to previous studies in the Mediterranean region, we assessed the efficacy of several management techniques, including nurse-based planting, in the recovery of the structure and properties of mature native reference communities. In a burned area of southern Spain, we applied widely used community analysis tools (rarefaction and species accumulation curves, Chao 2 richness estimator, species evenness and beta diversity) to compare the profiles of a reference native community and the community achieved through different management practices: traditional planting, nurse-based planting and controls where natural regeneration was allowed to occur. 3. Our results showed that post-fire establishment of planted seedlings was higher under the canopy of nurses than in open ground. More importantly, nurse-based restoration increased the species richness and evenness of tall-shrubs and trees as well as the life-form diversity, with the restored community approaching the reference community in terms of both composition and structure of the bank of juveniles. 4. Synthesis and applications. We conclude that in contrast to traditional reforestation, where diversity is constrained by the elimination of pioneer and regenerated tall-shrubs, nurse-based restoration contributes to accelerated recovery of important community structure and properties. Thus, it should be used preferentially over traditional reforestation in Mediterranean mountains where restoration of native communities, and not merely tree establishment, is dictated under current habitat directives.

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Vegetation restoration is usually based on predefined species assemblages from large-scale maps of potential vegetation. However, most restoration plans apply to smaller spatial scales, so a homogeneous species assemblage is usually assigned to the target site. We propose defining species assemblages for restoration by modeling the distribution of individual target species. The example presented here is about postfire restoration, but it can be used in other types of disturbed areas. We surveyed 212 plots in well-preserved vegetation around the burned area to obtain a list of target species and physical parameters of the plots. The burned area was divided in a grid of 723 squares, 1 ha each, and then characterized according to the same physical parameters. From these data, we modeled the distribution of 23 target species. A target map of predicted species assemblages was built combining species maps. This map largely resembles the native vegetation in terms of species richness per plot, environmental gradients in a-diversity, spatial variation in b-diversity, and frequency of species occurrence. Comparison between the target map and the current vegetation (recovery status) indicated that, on average, only half of the potential set of species is already present in each plot. Analysis of the recovery status suggested that both rock outcrops and areas at lower altitude, with gentle slope and deeper soil, recover faster. This illustrates the utility of target maps to outline plots in more need of restoration.

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This study analysed the germination success of pods of six annual native legumes species: Astragalus hamosus, Medicago minima, Medicago orbicularis, Medicago polymorpha, Medicago rigidula and Scorpiurus muricatus. The use of these species has been proposed as a means of generating and improving herbaceous cover in olive groves. Germination success was studied in terms of the variability in the number of seeds germinated per pod after 18 months at two different sowing depths, on the surface (S) and buried 10 mm (B). Pods were subject to five different pre-germination treatments: chemical scarification, consisting of immersion in sulphuric acid for 15 min (S_15) and 20 min (S_20), immersion in water for 48 h (W_48), pod precooled to -18ºC for one month (P_18º) and untreated pods (Con). The results showed that the effectiveness of the different treatments and sowing depths depended on the species, and that there were no problems of 'sibling-competition' in any of the treatments or at any of the sowing depths. Species with larger, non-spiralled pods, such as A. hamosus or S. muricatus, or with very loosely spiralled pods such as M. orbicularis, had greater germination rates when buried, mainly in the case of untreated pods and pods that were immersed in sulphuric acid for 20 minutes.Additional keywords: burial depth; spontaneous cover; scarification Abbreviations used: B (buried); Con (untreated pods); Dmax (maximum diameter); GEE (generalized estimating equations); GS/P (germinated seeds per pod); P_-18° (precooled to -18 °C for one month); S (surface sowing); S_15 (soaking pods in 95% concentrated sulphuric acid solution for 15 min); S_20 (soaking pods in 95% concentrated sulphuric acid solution for 20 min); SPE (seed production efficiency); SPP (seed production potential); W_48 (soaking pods in distilled water for 48 h).