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The use of ecohydrologically suitable microsites, such as sink patches (i.e. zones intercepting and infiltrating runoff) and nurse shrubs, have largely been proposed as tools to improve the establishment of late-successional trees in Mediterranean reclaimed landscapes. Nonetheless, this technique needs to be accurately tested along with the influence of seedling water-use strategy. To that purpose, we monitored the short- and mid-term (i.e. 4 and 8 years, respectively) influence of sink patches and nurse shrubs (Genista scorpius) on seedlings of two species with contrasted water-use strategies, Pinus nigra, a more drought avoider and isohydric species, and Quercus ilex, a more drought tolerant and anisohydric species. In the short term, G. scorpius shrubs enhanced the establishment of seedlings planted in shaded spots under its canopy. This positive interaction was more relevant for Q. ilex in drier years, while P. nigra was more facilitated in wetter years. Sink patches ameliorated the survival of both species, but only promoted greater growth during wetter years. P. nigra seedlings showed a high sensitivity to precipitation reduction. Their survival and growth were strongly constrained in dry years, resulting in a very high cumulative mortality at the end of the 8-year study period regardless of the microsite the seedlings were planted in. Q. ilex showed better seedling performance than P. nigra in the mid-term, keeping also the positive effects of suitable microsites on plant survival in the mid-term, after 8 years of plantation. Our results support the use of suitable microsites that ameliorate ecohydrological conditions as key spots for enhancing ecological succession in reclaimed mining sites, particularly the use of G. scorpius as nurse shrub for improving Q. ilex seedling establishment and growth. Our results also suggest that seedling functional strategy to cope with drought is a critical factor conditioning the overall plantation performance in the mid-term. Thus, seedling water-use strategy should constitute a key species selection criteria in future restoration programs focused on Mediterranean ecosystems, especially under climate change. This work was funded by the project CGL2010-21754-C0-02 from the Spanish Ministry of Economy and Competitiveness. EV is supported by the Spanish Ministry of Economy and Competitiveness within project ALTERACLIM (CGL2015-69773-C2-1-P). MMH is beneficiary of a Serra Hunter fellowship on Physical and Environmental Geography funded by the Generalitat de Catalunya (UB-LE-9055).

Invasive tree Acacia dealbata was introduced in the Iberian Peninsula in the 19th century. Nowadays, it is spreading in wide areas in which native vegetation has been altered or removed by human-activities, as in the case of Quercus robur forests in the northwest of Spain. In this article we assess the impact of A. dealbata invasion on soil properties (pH, organic matter, total N, NH 4 + -N and NO 3 - -N ), light characteristics (direct and diffuse photon flux density and leaf area index) and soil seed bank and established vegetation. We selected three sites where native Q. robur forests and A. dealbata invaded patches grow nearby. Before 2008 autumn rains, we took soil samples under five trees per species (A. dealbata and Q. robur) and site to determine soil seed bank floristic composition and soil properties. In spring 2009 we monitored the floristic composition of the vegetation growing under the same trees. Our results show that A. dealbata presence increases total N, NH 4 + -N and NO 3 - -N and decreases pH in soils but does not affect light characteristics. Acacia dealbata modifies soil seed bank composition by decreasing species richness, seed density and the percentage of bryophyte and fern spores, and by increasing the percentage of Asteraceae and exotic species. Understorey of invaded A. dealbata forests shows a decrease in species richness and plant cover. Finally, A. dealbata reduces the similarity between the soil seed bank and the established vegetation. These results suggest that A. dealbata invasion produces a deep impact on Q. robur forests that hampers their regeneration, even after A. dealbata removal.

Vegetation, soil, and hydrology in drylands often collectively exhibit strong ecohydrological interrelationships in which vegetation both influences and is influenced by runoff, particularly on sites with more gradual slopes. These two-way relationships have important implications for ecological restoration of disturbed sites, such as those being reclaimed following mining, yet studies from both ecological and hydrological perspectives specifically evaluating how the strength of ecohydrological interrelationships varies for a range of natural and restored conditions are still missing. We assessed two-way relationships between vegetation and soil hydrological properties by evaluating patterns of both plant community structure and soil hydrological characteristics related to runoff for natural sites and restored sites following mining. At the plot scale, we identified eight ecohydrological units based on interrelationships between vegetation communities and hydrological properties associated with runoff along a progression from source to sink patch types. Similarly, at the hillslope scale, which included patches of different types, we found a correspondence between the proportions of source and sink patches and both vegetation community and hydrological properties. The relative strength of ecohydrological interrelationships in hillslope mosaics decreased with decreasing disturbance except for rilled hillslopes, likely because parts of the hillslope become isolated from the others. Our results highlight, in general, how ecohydrological interrelationships are related with degree of disturbance, and in particular, how rilling alters ecohydrological interrelationships, thereby precluding effective restoration.

Soil erosion in reclaimed mines may affect plant colonization and performance, and may compromise restoration success; however, the magnitude of this effect has seldom been quantified. We monitored the dynamics of vegetation (seed bank density, seedling emergence, plant mortality, and seed production) during a growing season (2003-2004) in three constructed slopes with differing past erosion rates. The slopes are located in the Utrillas coalfield in Spain, which experiences a Mediterranean-continental climate. In the most eroded slope, soil water availability was lower--especially in the interrill areas--and seedling emergence rate, plant survival, and seed production were also significantly lower than on the less eroded slopes. We found that vegetation recovery is dramatically constrained when rill erosion rate is 17 t ha⁻¹ yr⁻¹ and plant cover is 30%, but this effect disappears when plant cover is higher than 60%. Soil erosion in constructed slopes appears to inhibit natural plant colonization processes by increasing runoff water loss over the long-term. Thus, when rill erosion networks develop, human intervention would be needed to minimize the loss of water and facilitate vegetation colonization.

The knowledge of the spatial patterns of species richness and, particularly, of endemic and threatened species at the scale at which management activities take place is crucial for conservation. Yet, detailed descriptions of species’ distribution areas are often lacking or incomplete, especially in the tropics. This article focuses on the African island of Bioko and uses species accumulation curves to evaluate the completeness of its biological inventory for three plant groups (ferns, monocotyledons and dicotyledons), birds and monkeys. Results showed that the current inventory is fairly complete for monkeys and birds, but only covers half of the vegetation in the island. Bioclimatic models were used to estimate the potential distribution of each species and to assemble species richness patterns for each taxa and for endemic and threatened species, revealing that montane and lowland rainforests were the richest habitats, while high altitude shrubs and subalpine meadows were the poorest ones. Predicted richness values for monsoon forests were unexpectedly low for plants and birds, probably because of insufficient sampling in these areas. Additionally, the comparison of species richness patterns with the proposed delineation of protected areas for the island shows that these will cover most hotspots of species richness, endemism and threatened species, except for dicotyledonous plants and endemic birds. The potential utility of the predicted patterns for conservation priorities and initiatives in Bioko is discussed.

Mining reclamation results obtained in the Teruel coalfield (Mediterranean-dry Spain) during the last 30 years have been quite limited. In order to improve restoration operations we conducted a study to analyse the trajectories of ecological succession and identify the main driving forces that control vegetation dynamic in reclaimed artificial slopes. A total of 87 slopes of different ages and restoration treatments were classified and characterized after recording different variables related to topography, restoration techniques, vegetation, local disturbances and soil erosion. Successional trends were inferred from gradient analysis as well as the factors, mechanisms and processes implied. We found a wide variety of plant communities and successional trajectories. Initial conditions (soil quality and revegetation treatments) as well as the environmental scenario (climatic conditions and vicinity of preserved propagule sources) were the main driving forces directing vegetation succession. Soil erosion triggered by external run-on coming from surrounding structures was also identified as a key factor determining the evolution of vegetation in these dry environments. Other local disturbances (grazing and fungal pests) can favour vegetation transition in communities dominated by highly competitive non-native sown species to more diverse shrub communities. Some practical considerations for future reclamation projects are suggested.

Large areas of abandoned cropland in the world can be reforested with native shrubs and trees to gain a number of environmental benefits. In abandoned Mediterranean croplands, establishment and growth of woody plants are limited by high radiation and low water availability during summer, and weeds are strong competitors for resources, particularly water. We conducted a 3-year experiment in central Spain to study the response of three Quercus species (Q. coccifera, Q. ilex and Q. faginea) that differ in their habitat requirements under four treatment field conditions resulting from the combination of full-light versus artificial shading and weed presence versus weed mowing. We measured seedling survival, resprouting capability and growth, weed production, microclimate (incident photosynthetic active radiation (PAR), air temperature, soil water evaporation and effective precipitation) and soil moisture. Shading and weeds reduced PAR reaching the seedlings and soil water evaporation, and shading also reduced effective precipitation. Shading and mowing increased soil moisture. We found a clear positive synergic effect of shading and mowing on seedling performance. Weed competition limited seedling survival in all species more than high radiation, whereas the relative importance of these factors in limiting growth depended on the growth measure and species. As hypothesised, the effects of stress release on plot cover, an integrated performance index that combines survival and growth, were most noticeable in Q. faginea, the most mesic species, and least in Q. coccifera, the most xerophytic species. The release of weed competition allowed Q. ilex seedlings to invest resources in above-ground and, apparently, in below-ground growth. Shading increased simultaneous growth in diameter and volume only for Q. faginea. It is important that planted Quercus seedlings in abandoned Mediterranean cropland take advantage of a low competitive environment from weeds during the period before the first dry season. Once seedlings have established, an artificially shaded environment would provide benefits in terms of plot cover by the oaks, particularly for mesic species. Studies like this will be of great interest to optimize resource investment in active restoration of other ecosystems of the world.

Retama sphaerocarpa is a Mediterranean shrub that when adult, facilitates the establishment of herbaceous plants under its canopy. We test the hypothesis that during the establishment of R. sphaerocarpa seedlings, the interaction with the herbaceous plants is negative. We carried out a greenhouse experiment in which seedlings of R. sphaerocarpa were grown under different conditions of competition with herbs, watering and date of emergence. Measurements of seedling mortality, biomass and growth were taken during the first growing season. We found a significant relationship between R. sphaerocarpa seedling mortality and competition in early spring, presumably due to higher water demand of herbaceous plants. Generally, presence of herbaceous species, lower availability of water and late emergence had negative effects on biomass and growth of Retama seedlings. Additional water compensated for the negative effects of competition, except on leaves and cladodes of Retama seedlings, suggesting that other resources, such as light, could be the subject of competition. In contrast, Retama seedlings exerted a positive influence on the herbaceous plants by increasing their survival and biomass, probably as a consequence of the high availability of nutrients provided by the Rhizobia nodules in the roots of Retama seedlings. We concluded that, at the regeneration stage of the shrub, the interaction between the herbaceous vegetation and the shrub is negative for the shrub and positive for the herbs. This suggests a shift from competition to facilitation with age of Retama, as reciprocal positive interactions have been described between herbaceous plants and adult individuals of the shrub. © 2004 Elsevier SAS. All rights reserved.

We tested simulated effects of herb competition on the performance of planted seedlings of Quercus faginea ssp. faginea in Mediterranean abandoned cropland. We produced three types of environment with respect to herb competition: absence of competition (AC), below-ground competition (BGC), and total competition (TC). We assessed the performance of Q. faginea seedlings in each treatment in five ways: (1) seedling mortality, (2) leaf length and total plant leaf area, (3) water potential, (4) total biomass and biomass allocation, and (5) non-structural carbohydrate storage in different plant organs. We also measured (6) soil moisture at different depths and (7) biomass production of herbs. The TC treatment reduced water availability more than the BGC treatment, in agreement with the most pronounced water stress in seedlings under TC conditions. BGC and TC treatments showed a high and similar seedling mortality, which was one order of magnitude higher than that in the AC treatment. Competition treatments affected glucose concentration in both shoots and roots, and followed the rank TC > BGC > AC. Q. faginea seedlings might compensate a lower water availability through glucose accumulation in leaves to reduce the osmotic potential. There was a maximum starch concentration in the BGC treatment that hints that a moderate resource limitation would limit tissue growth but not carbon assimilation. We conclude that the negative effects of herbs on Q. faginea seedlings are mostly a result of competition for water, and that this competition is noticeable since the earliest stages of the establishment. Complete weed removal is a technique that would strongly improve seedling survivorship., This research has been funded by the projects Factores limitantes de la revegetación con especies leñosas autóctonas de áreas degradadas en ambientes mediterráneos. Rendimiento de distintas actuaciones de manejo (REN2000-745), granted by the CICYT (Spanish government) and Estrategias para la restauración de paisajes degradados en zonas secas (E040/2001), granted by the Universidad de Alcalá. We are indebted to the students Olivier Pastre and Antoine Aubeneau for their assistance in field and lab work. We acknowledge the comments on a preliminary version of this manuscript from our colleagues Fernando Valladares, Pedro Villar, and Miguel A. Zavala. Peter Buckley and an anonymous reviewer improved its final version.

Floristic data collected from permanent plots dur- ing 14 consecutive years are used to model the frequency of the 62 most abundant species in relation to post-ploughing succession, topography and rainfall in annual Mediterranean grasslands located in a Quercus rotundifolia dehesa. The interannual dynamics of species richness are also analysed. From 1980 to 1993, presence/absence data of grassland spe- cies were noted in five 20 cm × 20 cm permanent quadrats placed at random in 1980 in 14 permanent plots on a south- facing slope along the topographic gradient. Weekly autumn rainfall data over the 14 years were analysed using a profile attributes index and Hybrid Multidimensional Scaling to ar- range the years according to their autumn rainfall pattern. Generalized Linear Models were used to fit the species rich- ness and species frequency according to topographic position, age since the last ploughing episode, total rainfall in the growing season and autumn rainfall pattern using a forward stepwise procedure. The richness model includes all of these variables, and reveals a relatively high goodness-of-fit (71 %). The fact that the meteorological factors play a key role in modelling richness forces us to include them if we wish to use richness as an indicator of the degree of disturbance in these highly fluctuating annual pastures. Models of species dynam- ics show that although roughly 33 % of the species have a successional behaviour, the majority are more dependent on temporal heterogeneity associated with rainfall or spatial het- erogeneity linked to the topographic gradient.