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Monospecific pine forests are widespread due to extensive afforestation efforts and natural colonization of abandoned croplands in the Mediterranean Basin. It was originally thought that pines would facilitate the natural colonization of native late-successional resprouter species (e.g., hardwoods), but these species can be compromised if competition with pines outweighs their facilitative effect on these hardwood species. Managing the density or canopy cover of these widespread pine forests can potentially provide some “optimum” balance between facilitation and competition to maximize success in the introduction of late successional species while maintaining a tree stratum. We tested the response (survival and growth across 10 years) of six resprouter species covering a wide range of plant functional strategies, from drought-tolerant sclerophyllous shrubs and trees to malacophyllous drought-sensitive trees, across an experimental gradient of Aleppo pine canopy cover. Seedling performance varied according to the functional strategy, pine cover and time. High pine cover generally enhanced seedling survival, whereas moderate pine cover generally enhanced seedling growth, although this response was modulated by the functional strategy of the seedling species. Interactions between pines and seedlings were only detectable 2–3 years after plantation, increasing in intensity with time. The latter highlights the need of medium to long-term studies to evaluate plant-plant interactions in these water-limited environments with slow successional trajectories. Our results could be attributed to the shade tolerance of most of the introduced trees, combined with their low tolerance to the combination of high sunlight radiation and drought. We found an optimal pine cover of ca. 50% (equivalent to 300–400 trees/ha) in which both survival and growth of late successional species can be maximized, which help to select best locations for more efficient reforestation programs and set a threshold value to decide whether or not to perform tree thinning to enhance ecosystem diversity and, subsequently, resilience. The study was funded by the FUME (EU FP7-Environment, GA. 243888), SURVIVE-2 (CGL2015-69773-C2-2-P MINECO/FEDER) and INERTIA (PID2019-111332RB-C22) projects, from the Spanish Government and IMAGINA project (PROMETEU/2019/110) from Generalitat Valenciana. L.M. was supported by the Spanish MICINN (PTA2019-018094). S.S. was supported by the Ramón y Cajal fellowship (RYC-2016-20604) and the FOBIASS project (RTI2018-098895-A-100), both from the Ministry of Science and Innovation. CEAM foundation is funded by Generalitat Valenciana.

During the last decades, climate and land use changes led to an increased prevalence of megafires in Mediterranean-type climate regions (MCRs). Here, we argue that current wildfire management policies in MCRs are destined to fail. Focused on fire suppression, these policies largely ignore ongoing climate warming and landscape-scale buildup of fuels. The result is a 'firefighting trap' that contributes to ongoing fuel accumulation precluding suppression under extreme fire weather, and resulting in more severe and larger fires. We believe that a 'business as usual' approach to wildfire in MCRs will not solve the fire problem, and recommend that policy and expenditures be rebalanced between suppression and mitigation of the negative impacts of fire. This requires a paradigm shift: policy effectiveness should not be primarily measured as a function of area burned (as it usually is), but rather as a function of avoided socio-ecological damage and loss., This work was financed by national funds through FCT—Foundation for Science and Technology, within the scope of project PCIF/AGT/0136/2017 (People&Fire: reducing risk, living with risk) and PTDC/AGR-FOR/2586/2014 (RurIntFIre: Fire in the Rural-Urban Interface: characterisation, risk mapping, and fuel break design). FM was funded through contract IF/01053/2015 (FCT). JMCP was supported by the Forest Research Centre, a research unit funded by Foundation for Science and Technology I.P. (FCT), Portugal (UID/AGR/00239/2019). PF work was carried under project UID/AGR/04033/2019 supported by FCT. JMM acknowledges funding from Ministerio de Ciencia, Innovación y Universidades (project CGL2016-78357-R)

Deforestation, rising temperatures, drought, fire and other ecological disturbances are reducing forest cover on much of the earth, and compromising the ability of forests to supply important ecosystem services. Ecosystem management and ecological restoration are focused on preventing and repairing ecosystem degradation, but the rapidity and pervasiveness of these global transformations threaten to exceed our capacity to plan for or respond to them at sufficient spatiotemporal scales. In this chapter we focus on forests in two contrasting biomes – boreal and Mediterranean – that are anticipated to experience major ecological changes in the 21st century. The relatively species-poor boreal forest covers 11% of the earth's surface and exerts a major influence on the global climate. Mediterranean climate region (MCR) forests are highly fragmented and cover less than 0.5% of the earth's surface, but the MCR regions support nearly 1/5 of the world's flora. Forests in both biomes are dominated by stress-tolerant taxa, but the principal source of ecological stress is very different: low air and soil temperatures in the boreal region, and lack of soil moisture during the warm growing season in the MCRs. Projected climatic changes will ameliorate the central ecological stress in boreal forests, with rising temperatures and increasing precipitation leading to generally better growing conditions for trees. In the MCRs, projected climatic changes will exacerbate hydrological stress, as warming and projected decreases in growing-season soil moisture worsen the annual drought. Overall, the direct effects of climate change on tree survival and growth are likely to be positive in the boreal region and negative in the MCRs, but interactions between these climate drivers and other stressors – changes in precipitation type, fire and pest outbreaks, invasive species, and so on – will have important and potentially contrasting indirect effects on soils and the forests that grow in them. In both biomes the implications for forest composition, structure, function, dynamics and sustainability are profound. We examine how interactions between global change, soils and disturbance are likely to affect boreal and MCR forests, and what the implications of these effects may be for ecosystem management and ecological restoration. We describe general patterns of climate, vegetation, soils, human history, and disturbance ecology in the two biomes and we summarize climate trends and projected future conditions, with focus on effects to soils. We finish with biome-specific summaries of current restoration strategies and practices, and a consideration of how soil responses to global change-related stressors and disturbances might require changes in the way we plan for and implement forest management and restoration. Both boreal and MCR forests and their soils will experience major changes over the next 50–100 years. Adherence to the basic tenets of ecosystem management and ecological restoration will provide the best chance of conserving these forests and sustaining the ecosystem services they provide.

El presente trabajo consiste en el seguimiento y evaluación de los resultados de la restauración forestal ecológica realizada en la cuenca de Albatera durante los años 2003 y 2004, poniendo énfasis en la supervivencia después del verano de 2014 comparada con la supervivencia registrada en los años anteriores.Para la toma de los datos ha sido necesario desplazarse a la cuenca durante 20 días entre los meses de febrero y marzo del 2015 para recoger datos de supervivencia y tamaño de las diez especies estudiadas: tres especies arbóreas (Pinus halepensis, Tetraclinis articulata, Ceratonia siliqua) y siete arbustivas (Pistacia lentiscus, Quercus coccifera, Rhamnus lycioides, Ephedra fragilis, Chamaerops humilis, Juniperus oxycedrus y Olea europea ssp sylvestris). Además fue necesario realizar otras tareas como la revisión de los datos históricos de las repoblaciones realizadas como del clima de la zona.Los resultados muestran mayor supervivencia y crecimiento de los plantones plantados en la solana sobre los de umbría, y sobre todo sobre los ubicados en la unidad de terrazas forestales. Además se encontró una mayor supervivencia de los especímenes plantados en la campaña del año 2004 respecto a los introducidos en la campaña del 2003.

Pinus pinaster (maritime pine) is widely planted in the Mediterranean Basin. Maritime pine forests’ carbon stocks are dynamic because of the effect of wildfires and timber activities. Management practices offer an opportunity to mitigate climate change via increasing carbon storage in various ecosystems. In this work, we quantified carbon pools in P. pinaster forests in relation to fire occurrence and different post-fire salvage logging techniques. For this, we studied an area in northern Portugal where different parts had burned zero, one and four times during the last three decades. Following the last fire in 2012, two salvage logging treatments were carried out: (1) typical logging where all logs and tree biomass were removed and (2) conservation logging where burned tree branches were left in piles and log extraction was restricted to specific extraction trails. We assessed the carbon stocks for the aboveground and belowground compartments, taking into account their different components (vegetation, litter, roots and soil organic carbon). Our main findings were, firstly, that recurrent fires can be catastrophic in terms of carbon sequestration if the overstory dominated by P. pinaster does not regenerate after fire (2.4 times less). Secondly, soil organic carbon constituted an important carbon pool, being the most important when pines are eliminated due to recurrent fires with short intervals (90–95 %). Finally, the conservation technique applied here, leaving piles of branches on the soil surface, would be a suitable measure to increase carbon storage, at least in the short term, but might interfere with the recruitment of the pine stand.

Recent observations suggest that repeated fires could drive Mediterranean forests to shrublands, hosting flammable vegetation that regrows quickly after fire. This feedback supposedly favours shrubland persistence and may be strengthened in the future by predicted increased aridity. An assessment was made of how fires and aridity in combination modulated the dynamics of Mediterranean ecosystems and whether the feedback could be strong enough to maintain shrubland as an alternative stable state to forest. A model was developed for vegetation dynamics, including stochastic fires and different plant fire‐responses. Parameters were calibrated using observational data from a period up to 100 yr ago, from 77 sites with and without fires in Southeast Spain and Southern France. The forest state was resilient to the separate impact of fires and increased aridity. However, water stress could convert forests into open shrublands by hampering post‐fire recovery, with a possible tipping point at intermediate aridity. Projected increases in aridity may reduce the resilience of Mediterranean forests against fires and drive post‐fire ecosystem dynamics toward open shrubland. The main effect of increased aridity is the limitation of post‐fire recovery. Including plant fire‐responses is thus fundamental when modelling the fate of Mediterranean‐type vegetation under climate‐change scenarios. This research was supported by the European Union’s Seventh Framework Program (FP7/2007-2013) under grant agreement 283068 (CASCADE). AGM was supported by the EU-funded Marie Sklodowska-Curie Action ECOHYDRY (GA660859), SB by the project DRYEX2 (CGL2017-89804-R) funded by the Spanish Ministry of Economy and Competitiveness, and VMS by a ‘Beatriu de Pinós’ fellowship (2014BP-B-00056).

The extensive abandonment of agricultural lands in the Mediterranean basin has led to large landscapes being dominated by early-successional species, characterized by high flammability and an increasing fire risk. This fact promotes fire occurrence and places ecosystems in a state of arrested succession. In this work, we assessed the effectiveness of several restoration actions in redirecting these ecosystems toward more resilient communities dominated by resprouting species. These actions included the mechanical clearing of early-successional species, the plantation of resprouting species, and the combination of both treatments. For 13 years, we assessed shifts in the successional trajectory and ecosystem flammability by changes in: species composition, species richness, ecosystem evenness, the natural colonization of resprouting species, total biomass and proportion of dead biomass. We observed that the plantation and clearing combination was a suitable strategy to promote resilience. Species richness increased as well as the presence of the resprouting species introduced by planting. The natural colonization of the resprouting species was also enhanced. These changes in the successional trajectory were accompanied by a possible reduction of fire risk by reducing dead fuel proportion. These findings are relevant for the management of Mediterranean basin areas, but also suggest new tools for redirecting systems in fire-prone areas worldwide. This research was financed by the DESESTRES (PROMETEO II ES/2014/038), GESFIRE (ULE/CEAM), SURVIVE-2 (CGL2015-69773-C2-2-P) and the CASCADE (European Commission FP7/GA283068) projects. VMS was supported by a “Beatriu de Pinós” fellowship (2014BP-B-00056) from the Generalitat de Catalunya.

The adoption of sustainable land management strategies and practices that respond to current climate and human pressures requires both assessment tools that can lead to better informed decision-making and effective knowledge-exchange mechanisms that facilitate new learning and behavior change. We propose a learning-centered participatory approach that links land management assessment and knowledge exchange and integrates science-based data and stakeholder perspectives on both biophysical and socio-economic attributes. We outline a structured procedure for a transparent assessment of land management alternatives, tailored to dryland management, that is based on (1) principles of constructivism and social learning, (2) the participation of stakeholders throughout the whole assessment process, from design to implementation, and (3) the combination of site-specific indicators, identified by local stakeholders as relevant to their particular objectives and context conditions, and science-based indicators that represent ecosystem services of drylands worldwide. The proposed procedure follows a pattern of eliciting, challenging, and self-reviewing stakeholder perspectives that aims to facilitate learning. The difference between the initial baseline perspectives and the final self-reviewed stakeholder perspectives is used as a proxy of learning. We illustrate the potential of this methodology by its application to the assessment of land uses in a Mediterranean fire-prone area in East Spain. The approach may be applied to a variety of socio-ecological systems and decision-making and governance scales. The PRACTICE protocol was developed in the framework of the project PRACTICE: Prevention and Restoration Actions to Combat Desertification. An integrated Assessment, funded by the European Commission (GA226818). This research was also funded by the European project CASCADE (GA283068), and the Marie Skłodowska-Curie Actions Fellowship of the European Union (GA 629677) “S4S, Science for Society Solutions”, awarded to B.J.O.

This study focuses on the synthesis of merlinoite from Chinese coal fly ashes by KOH direct conversion method, with special emphasis on the application of synthetic merlinoite as fertilizer. These fly ashes were collected from two pulverized-coal combustion (PCC) power plants in Xinjiang, Northwest China. The synthesis results are influenced by fly ash characteristics and different synthesis conditions (KOH solution concentrations, activation temperature, time, and KOH/fly ash ratios). A high quality merlinoite-rich product was synthesized under optimal activation conditions (KOH concentration of 5 M, activation temperature of 150 °C, activation time of 8 h and KOH/fly ash ratio of 2 l/kg), with a cation exchange capacity (CEC) of 160 cmol kg−1. The synthetic merlinoite is proved to be an efficient slow release K-fertilizer for plant growth, indicating that it can be widely used for high-nutrient demanding crops growing in nutrient-limited soils and for large-area poor soil amendment in opencast coal mine areas around the power plants that will substantially grow with the increasing coal combustion in Xinjiang in the near future.

In the last decades, several studies have reported the increase of land degradation and desertification in the Mediterranean Basin. Depending on degradation severity, ecological restoration might be needed in order to promote ecosystem recovery. The ecology of the selected species and intra specific variability should be considered in order to improve restoration options, especially facing climate change. The present study tested the hypothesis that seedlings from drier provenances would be better adapted to low water content conditions. Seeds were germinated under controlled temperature after which seedlings were grown in a phytotron under two contrasting watering regimes. Seedling performance was analysed using morphological and physiological parameters. Low water content had a clear negative effect on the seedlings’ aboveground biomass (total dry weight, root collar diameter, leaf dry weight and leaf weight ratio) and a positive effect on belowground biomass (root weight and root:shoot ratio). This response was not unequivocal, since provenances differed in morphological adaptations to low water content. Seedlings from the wettest provenance revealed a higher relative growth rate under high water content but a poor adaptation to limited water availability when compared to the other two provenances. This was observed by the absence of a significant belowground investment in this provenance. Seedlings from the wettest provenance also presented a significant reduction of total leaf area that was not observed in the other two provenances. This can however be hardly considered as a successful adaptation to cope with drought since this provenance produced less sclerophyllous leaves, less belowground biomass and also lower sapwood to leaf area ratio independently from the water content conditions. By contrast, seedlings from the dry provenance with the hottest summer had similar root collar diameter, leaf dry weight and physiological performance under both watering regimes. The observed adaptations to water regimes seem to be related with the climate of the seed source and highlighted the importance of seed provenance in ecological restoration actions using Mediterranean species. This knowledge could improve early establishment success predictions for different plant populations, allowing more reliable and cost-effective management decisions under climate change scenarios.

Forest fire emissions modify the chemical composition of the atmosphere and the earth's climate system. The Ayoraburning experiment was designed to assess and quantify fire emissions from Mediterranean shrublands. A number of gaseous pollutants and particulate matter metrics (CO2, CO, CH4, PM2.5) were measured during 3 burning replicates by using real-time monitors. Quantification of carbon emissions released during the experiments showed that 71% was CO2, 26% CO, 3% CH4, and only 0.3% was particulate carbon. Emission factors obtained for CO2, CO and CH4 were 1257 ± 40, 453 ± 28 and 46 ± 12 g kg−1 dry matter, respectively, and combustion efficiencies ranged from 0.46 to 0.99. The experiments allowed the estimation of carbon emission in the different fire phases. Thus, 25% of carbon was sampled in the flaming phase and 75% of C in the smoldering phase. Current natural greenhouse gas (GHG) emission inventories in Mediterranean countries underestimate the actual emissions from forest fires since they do not consider forest shrub understory and shrublands and since they assume that the CO2 emitted is offset by forest re-growth. Our results may be used to improve current forest-fire emission inventories in southern Europe with special emphasis on shrublands.

Restoration works in opencast mining are mostly done with fast-growing herbaceous species to control the erosion of embankments during rainfall, especially immediately after their construction. Such species often exhibit a high demand for water and their survival is therefore associated to an adequate hydric supply. If this fails, these species can rapidly disappear when water is scarce. This paper shows the results of a restoration experiment where two stony mineral substrates were used in a quarry area (NE Spain). The experiment was carried out at lysimeter scale and the aim was to evaluate the short time vegetation response to common restoration practices in semiarid areas with two types of substrates and two types of irrigation practices. Lysimeter results were used to indirectly draw implications for the usual irrigation practices in the area. During periods of the first year after sowing, irrigated and non-irrigated lysimeters were monitored for substrate humidity, water leachates and plant development. The population cover of sown plants fluctuated according to the water availability in the substrate before drought. Density of total basal shoots decreased dramatically during the period of water stress, reaching negligible cover values on both types of substrates. Water content in the top substrate (0–20 cm) was dramatically reduced in June, just after the maximum plant cover and water demand were reached (May). According with our results, it is not advisable to aim at a continuous and dense herbaceous cover composed of species that are not drought tolerant in restoration works, especially if embankments are constructed with spoil mine substrates. The restoration of opencast areas should include the use of water stress-resistant plants and careful irrigation plans.

Restoration of woodlands and shrublands 131 In spite of the similarities in climate, many striking differences can be found among MCRs, in addition to fi re regime. As mentioned, historical differences in land use practices, including the time span of degrada-tion processes, socio - economic dependence on local resources and cultural perceptions of the relationship between humans and nature, all have great impact on biota and ecosystem dynamics. The Mediterranean Basin is the only MCR in the so - called Old World, where humans have practised agriculture for as long as 13 millennia in some areas (Purugganan & Fuller 2009 ). The process, initiated in the Near East, is thought to have spread to the entire Mediterranean region over the course of about three millennia (Zeder 2008 ). In the process, people consumed resources and trans-formed, or ‘ resculpted ’ natural

Land degradation and desertification is a common feature in Mediterranean landscapes due to extensive and intensive land use and natural or man induced disturbances. The ecosystem may need external inputs to recover its composition and function as soils are often impoverished and vegetal key stone species lost. We evaluated the effects of the application of fresh and air-dried biosolids in the establishment and morphological and physiological performance of seedlings of Pinus halepensis and Quercus ilex under dry Mediterranean field conditions. Seedling survival was not affected by biosolid treatments in any of the studied species both two and ten years after planting. During the first two years, growth was enhanced by the two biosolid treatments in relation to control, although the change in the biomass allocation pattern differed between species. Rooting depth was significantly enhanced by liquid biosolid in Q. ilex and marginally reduced in P. halepensis as well as the exploration of soil. As a consequence, root-to-shoot ratio reduced significantly with dry and liquid sludge due to promoted aboveground growth while maintaining and even reducing belowground fractions. An improvement of the nutritional status, of fertilized seedlings especially of phosphorus, is the explanation for the better field performance. Vector analysis revealed an important phosphorus limitation for both species that was overcome with the application of liquid (both species) and air-dried biosolid (pine). The higher growth of pine seedlings attained in the liquid biosolid treatment was coupled with a significant decrease in foliar δ 13 C, suggesting lower water use efficiency. The significant increase in foliar δ 15 N in the biosolid treatments in both species suggested that a large proportion of the total nitrogen uptake came from the applied biosolids. Instead, with regard to the low biosolid application rate used in the study, treatments had an overall positive effect as a restoration tool by improving nutritional status and promoting growth of planted seedlings.

In dryland ecosystems, post-transplant water stress produces high seedling mortality after the first summer following outplanting. Our aim was to assess the effects of clay and hydrogel, both on the water holding capacity of the growing media and on various morphological and physiological characteristics of Quercus suber seedlings in the nursery and, subsequently, during the first 2 years in the field. Quercus suber L. seedlings were grown in four types of growing media: CS (Control growing media, standard mixture of limed peat and coconut peat, 1:1 v/v ratio), SC-10 (CS mixed with sepiolite clay at 10% v/v) and HS (CS mixed with hydrogel Stockosorb® K-400 at two doses, 0.7 and 1.5% w/w). HS-1.5 showed the best results, increasing the water holding capacity of the root plug, improving seedling water status and increasing seedling survival in the field. SC-10 showed an intermediate effect on seedling response in the field. Mixing hydrogel with a peat-based growing medium to form root plugs is a suitable technique for cultivating species to be planted in areas with a strong water deficit. This technique reduces post-transplant water stress in seedlings during their first months in the field and contributes to improve forest-restoration methods in dryland ecosystems.

Planting woody vegetation is frequently a first step towards the restoration of degraded drylands. Seedling establishment on unfertile soils may be favoured by applying organic amendments such as biosolids. But the outcome of such a practice is strongly dependent on the type of amendment and the application rate used. High application rates may have deleterious effects on plant performance and compromise plantation success. Thus amendment type and dose should be carefully selected to optimise benefits and minimize risks. In this study, we evaluated the effect of two organic amendments (composted and air-dried sewage sludge) applied at 5 doses (0, 15, 30, 45 and 60 Mg ha −1 ) on soil properties and on the performance of 1-year-old Pinus halepensis seedlings planted in a dry Mediterranean degraded area. Soil organic matter, electrical conductivity and nutrient availability increased with the application rate, but the magnitude of this increase depended on the type of amendment and the time. Organic amendments improved N and P status and promoted seedling growth. Nevertheless, at the higher application rates they showed a negative impact on seedling survival 1 and 3 years after application. Drought effects intensified by root competition with extant vegetation and reduced water availability within the planting hole were the main causes attributed to the higher mortality. Low to moderate doses showed the best combination of seedling survival and growth and can thus be recommended to promote the establishment of P. halepensis in dry Mediterranean areas.

In the Mediterranean Basin, most cultivated areas were abandoned in the last century and are now in various stages of old-field succession. The aim of this work was to analyse the successional trajectories of these ecosystems, and to assess possible deviations in these pathways due to fire occurrence at high or low recurrence levels. Old-fields abandoned either about 50 or about 100 years ago were selected in SE Spain. Within the 50-year-old abandoned fields, plots were established which had been burned by 1, 2 and 3 fires in the last 25 years. Cover values of vascular species were sampled and then analysed by means of multivariate analysis. Euclidean distances between resulting communities were used as an indicator of the possible deviation from the unburned successional pathway. Our results pointed to the possibility that different successional pathways may exist depending on fire occurrence and recurrence. In the absence of fire, the vegetation is dominated by pioneer species, mainly Pinus. With the passage of time this vegetation will become dominated by later successional tree species (Quercus). However, when early-successional communities are affected by fire, the succession can be diverted. A single fire is enough to change Pinus forests into alternative stable states dominated by Rosmarinus officinalis shrub communities, where the colonisation of species in later successional stages is arrested. This deviation increases in high fire recurrence regimes where the vegetation changes to dwarf shrubs and herbs.

We measured plant and soil carbon (C) storage following canopy-replacing wildfires in woodlands of northeastern Spain that include an understory of shrubs dominated by Quercus coccifera and an overstory of Pinus halepensis trees. Established plant succession models predict rapid shrub recovery in these ecosystems, and we build on this model by contrasting shrub succession with long-term C storage in soils, trees, and the whole ecosystem. We used chronosequence and repeated sampling approaches to detect change over time. Aboveground plant C increased from100 to ~3,000 g C m(-2) over 30 years following fire, which is substantially less than the 5,942 ± 487 g C m(-2) (mean ±1 standard error) in unburned sites. As expected, shrubs accumulated C rapidly, but the capacity for C storage in shrubs was600 g C m(-2). Pines were the largest plant C pool in sites20 years post fire, and accounted for all of the difference in plant C between older burned sites and unburned sites. In contrast, soil C was initially higher in burned sites (~4,500 g C m(-2)) than in unburned sites (3,264 ± 261 g C m(-2)) but burned site C declined to unburned levels within 10 years after fire. Combining these results with prior research suggests two states for C storage. When pine regeneration is successful, ~9,200 g C m(-2) accumulate in woodlands but when tree regeneration fails (due to microclimatic stress or short fire return intervals), ecosystem C storage of ~4,000 g C m(-2) will occur in the resulting shrublands.

Uptake of 137 Cs was measured in different agricultural plant species (beans, lettuce, barley and ryegrass) grown in 5 undisturbed soil monoliths covering major European soil types. The first cultivation was made three years after soil contamination and plants were grown during 3 successive years. The plant–soil 137 Cs transfer factors varied maximally 12-fold among soils and 35-fold among species when grown on the same soil. Single correlations between transfer factors and soil properties were found, but they varied widely with plant type and can hardly be used as a predictive tool because of the few soils used. The variation of 137 Cs concentrations in plants among soils was related to differences in soil solution 137 Cs and K concentrations, consistent with previous observations in hydroponics and pot trials. Absolute values of transfer factors could not be predicted based on a model validated for pot trials. The 137 Cs activity concentration in soil solution decreased significantly (11- to 250-fold) for most soils in the 1997–1999 period and is partly explained by decreasing K in soil solution. Transfer factors of lettuce showed both increasing and decreasing trends between 2 consecutive years depending on soil type. The trends could be explained by the variation in 137 Cs and K concentrations in soil solution. It is concluded that differences in 137 Cs transfer factors among soils and trends in transfer factors as a function of time can be explained from soil solution composition, as shown previously for pot trials, although absolute values of transfer factors could not be predicted.

Because Mediterranean ecosystems are prone to fire, their soils are expected to contain relevant amounts of black carbon (BC); nevertheless, quantitative information is scarce. Herein, we provide data on the abundance of BC in the surface soil (uppermost 5cm) of shrubland plots on old agricultural fields diversely affected by fires (0,1, or 2 wildfires in the last 25 y) and with contrasted land-use histories (either never cropped, early abandoned, or recently abandoned). Black C and black nitrogen (BN) were quantified in the surface horizon (0-5 cm) as the residue of low-temperature dichromate oxidation, after previous destruction of mineral matter with HF. The obtained amounts of BC ranged from 0.73 to 10.32 g (kg dw) -1 (mean: 3.07, which corresponds to an average of 8.62% of the total organic C), while the amounts of BN ranged from 21.5 to 373.0 mg (kg dw) -1 (mean: 97.1, or an average of 4.30% of the total N of the samples). Repeated fires did not consistently increase either the BC or the BN amounts. Black-C and (especially) BN accumulation seems related to fine silt, whereas the effect of clay is unclear. Even though the amounts of BC obtained in this study are slightly higher than those from other ecosystems, including Mediterranean broad-leaved forests, overall they are far from the very high values reported in the literature for chernozems from Germany or Canada. Thus, on the whole, in Mediterranean shrublands affected by wildfires, BC does not seem to be a dominant fraction in the soil organic C.

Soil microflora can directly take up the amino acids (Aas) released by decomposing plants and use them, together with de novo synthesized Aas, as building blocks for their own structures, which are expected to have an Aa composition that differs from plant-derived structures. The degree of change in the Aa composition during OM decomposition should reflect the degree of N evolution. Here we apply this concept to the study of three litter decomposition sequences in European forests: boreal (Pinus sylvestris L., Jadraas, Sweden), cool Atlantic (Pinus sylvestris L., La Gileppe, Belgium), and warm Atlantic (Pinus pinaster L., Montemor, Portugal). Litter was sorted into six decomposition stages according to morphological features: from intact, light-brown needles to dark needle fragments with faunal perforations. At each stage, the Aa composition of the litter was studied by acid hydrolysis plus liquid chromatography of the hydrolysates. Both the Aa content of the litter and the unhydrolyzable/total OC ratio increased with decomposition, but this was not the case with the unhydrolyzable/total N ratio. There is no sole pattern of Aa change with decomposition: in Jadraas and Montemor most of the changes occur in the initial and final steps, while in La Gileppe the changes seem quite evenly spread throughout the decomposition. The fact that the Aa composition of the litter did not converge with decomposition suggests the existence of site-specific biotas with contrasted Aa fingerprints. The abundance of a given Aa relative to the total differed among Aas and sites; but for some Aas it was possible to detect common patterns of decomposition behaviour (either a consistent increase or a consistent decrease). The aa/total ratio for Gly, Ala and Thr consistently increased with decomposition. These Aas were used to search for a numerical index, the Aa signature (AaSIG), which would reflect the changes in Aa composition from fresh debris to highly decomposed organic materials. The change in the proposed AaSIG was found to correlate well with the mathematical distance from the starting point (calculated as the euclidean distance); this suggests that it could be potentially useful as an indicator of N evolution during litter decomposition, at least in its first stages.

The current view on the relationship between the δ 13 C of pedogenic carbonates and soil organic matter is based on static studies, in which soil profiles are analysed at a given moment of their development. A dynamic approach to this question should also be possible by studying under field conditions how the δ 13 C of carbonates changes as organic matter decomposes. No such study has been undertaken owing to the slowness of the changes in the δ 13 C of carbonates, since it has been calculated that a detectable change will occur only after millenia. Nevertheless, this may not be true where soil CO 2 efflux is intense, as expected in soil zones with high microbial activity. In this paper we test the latter assumption by incubating mixtures of plant material and carbonate-rich red earth in the field at depths of 5, 20 and 40 cm. Four types of plant material were tested: Medicago sativa , Eucalyptus globulus , Quercus ilex and Pinus halepensis . Because the isotopic composition of these plant materials is known, we can determine the isotopic composition of the respired C and study how it relates to the (expected) changes in the δ 13 C. After two years of field incubation, the changes in δ 13 C of carbonates were high enough to be reliably detected and quantified, thus showing that the isotopic composition of soil carbonates can change quite rapidly in biologically active soil horizons. The observed changes are possible only if we assume that the increase in δ 13 C in the overall path respired C → pedogenic carbonate is much higher than the usually applied standard factors (about 15‰). These enrichments can be explained by assuming, as does the currently accepted paradigm, that the precipitation of new carbonates occurs in an open system in which the penetration of free-air CO 2 plays a major role. On the other hand, these enrichments can also be explained by an alternative interpretation, which assumes that the dissolution–precipitation carbonate cycles occur in systems that can be at least temporarily closed. Thus, we suggest that both possibilities (carbonate dissolution and precipitation in either an open or closed system) can coexist in a given soil, even though one or the other will dominate in any given time period.

Question: Is post-fire, medium-term vegetation dynamics determined by land-use or fire history prior to fire? Location: South-facing slope in the Gallinera valley, Alicante province, eastern Spain. Methods: After mapping the land-use and fire history of the study site using photo-interpretation, we sampled vegetation structure on a set of plots representing the most frequent land-use and fire history combinations on an area burned six years before sampling. We studied the effects of land-use history, comparing the one-fire land-use trajectories. We analysed the effects of fire history; comparing one- and two-fire plots for both previously cropped and uncropped areas. Results: Most variables were not significantly different between the earliest abandoned plots (abandoned at least 38 years before the fire) and the uncropped plots. On the most recently abandoned plots (abandoned between one and four years before the fire), the therophyte richness and the ratio of seeder:resprouter richness were sign...

To verify the paradigm that organic matter (OM) quality ( q ) decreases with decomposition it is necessary to define q in strictly chemical, operational terms. We suggest defining q as the result of a balance between the energy stored in OM and the external supply of energy needed to release it. We apply this concept to the study of litter decomposition in four European pine forests: boreal, cool Atlantic, Mediterranean and warm Atlantic. Intact litter cores were taken and transported to the laboratory, where needles were sorted into six classes that summarize the main facts of the decomposition: melanisation, fragmentation and perforation by mesofauna. Each class was analyzed by both differential thermogravimetry and differential scanning calorimetry to obtain its spectra of weight loss and energy release. In the non-decomposed needles, two peaks of weight loss and energy release appear: a labile peak at about 350 °C, and a recalcitrant peak at about 450 °C. During decomposition, both peaks (but especially the recalcitrant one) move to lower temperatures, and their shapes change from well defined to flattened. In Mediterranean litters, a third peak appears at about 500 °C, due probably to refractory products of neoformation. There is a continuous increase in the energy stored in the remaining litter (in Joules per unit OM): this increase is concentrated in both the most thermolabile fractions (lost at temperatures 450 °C). With decomposition OM becomes more recalcitrant (i.e., it is lost at higher temperatures), but its stored energy becomes more available (i.e., it is released at lower temperatures). Overall, the energetic benefit/cost ratio increases. Thus, our results to date do not agree with the current paradigm that q decreases with decomposition; rather, they suggest that, at least in the first phases we studied, q is maintained or even increases.

The biochemical quality of soil organic matter (SOM) was studied in various profiles under Quercus rotundifolia Lam. stands on calcareous parent material. Special attention was paid to the question of how biochemical quality is affected by position within the soil profile (upper versus lower horizons). The following global SOM characteristics were investigated: (a) overall recalcitrance, using hydrolysis with either hydrochloric or sulphuric acid; (b) hydrolyzable carbohydrates and polyphenolics; (c) extractability by hot water and quality of the extract; and (d) abundance of inert forms of SOM: charcoal and soot-graphite. The recalcitrance of soil organic carbon (OC) decreases with depth, following the order: H horizons>A horizons>B horizons. In contrast, the recalcitrance of nitrogen is roughly maintained with depth. The ratio carbohydrate C to total OC increases from H to B horizons, due to the increasing importance of cellulosic polysaccharides in B horizons, whereas other carbohydrates are maintained throughout the soil profile at a relatively constant level, 12–15% of the total OC in the horizon. Whereas the quality of the hydrolyzable carbon (measured by the carbohydrate to polyphenolic C ratio) decreases with depth from H to B horizons, the quality of the hot-water extractable organic matter is much higher in B horizons than in A or H horizons. The relative importance of both charcoal and soot-graphitic C and N tends to increase with depth. The ratio black/total is usually higher for N than for C, a result that suggests that inert SOM may represent a relevant compartment in the nitrogen cycle. Overall, our data suggest that in Mediterranean forest soils the organic matter in B horizons could be less stable than often thought.

The restoration of heavy metal contaminated areas requires information on the response of native plant species to these contaminants. The sensitivity of most Mediterranean woody species to heavy metals has not been established, and little is known about phytotoxic thresholds and environmental risks. We have evaluated the response of four plant species commonly used in ecological restoration, Pinus halepensis, Pistacia lentiscus, Juniperus oxycedrus, and Rhamnus alaternus, grown in nutrient solutions containing a range of copper, nickel and zinc concentrations. Seedlings of these species were exposed to 0.048, 1 and 4 microM of Cu; 0, 25 and 50 microM of Ni; and 0.073, 25 and 100 microM of Zn in a hydroponic silica sand culture for 12 weeks. For all four species, the heavy metal concentration increased in plants as the solution concentration increased and was always higher in roots than in shoots. Pinus halepensis and P. lentiscus showed a higher capacity to accumulate metals in roots than J. oxycedrus and R. alaternus, while the allocation to shoots was considerably higher in the latter two. Intermediate heavy-metal doses enhanced biomass accumulation, whereas the highest doses resulted in reductions in biomass. Decreases in shoot biomass occurred at internal concentrations ranging from 25 to 128 microg g-1 of Zn, and 1.7 to 4.1 microg g( -1) of Cu. Nickel phytoxicity could not be established within the range of doses used. Rhamnus alaternus and J. oxycedrus showed higher sensitivity to Cu and Zn than P. halepensis and, especially, P. lentiscus. Contrasted responses to heavy metals must be taken into account when using Mediterranean woody species for the restoration of heavy metal contaminated sites.

Aleppo pine stands can be made more resilient to disturbances such as forest fires, by introducing native and resprouting hardwood species. Pine density impacts seedling establishment by modifying resource availability and abiotic stress. Under Mediterranean conditions, moderate thinning (15–20 m 2 /ha) was the most effective in promoting the establishment and growth of a number of hardwood species. Developing silvicultural methods to help Mediterranean forests adapt to climate change is of high importance. Introducing resprouting hardwood species below pine stands is expected to promote diversity and resilience of these stands, particularly to forest fires. The aim of this study was to examine how the intensity of pine thinning influences understory microenvironment and the establishment of various hardwood seedlings in two Mediterranean sites. Aleppo pine stands were thinned down to three levels of basal area (uncut 30 m2/ha, moderate thinning 13–20 m2/ha, heavy thinning 7–10 m2/ha) at two Mediterranean sites (South-East France and South-East Spain). Seedlings of six hardwood species were introduced in the understory, and their survival and growth were monitored and related to changes in microenvironment induced by thinning. At both sites, thinning improved light availability and seedling diameter increment of all target species. Thinning increased extreme temperature and evaporative demand. Heavy thinning increased summer soil moisture in SE Spain but not in SE France. The worst conditions for seedling survival were reached under uncut stands in SE France and low-density stands in SE Spain. Thinning in pine stands accelerated seedling growth, but excessive thinning worsened summer drought and affected seedling survival. Moderate thinning (15–20 m2/ha) seems to be the best option in support of the introduction of hardwoods in the understory, which can improve forest diversity and resilience in the future.

Postfire restoration is meant to mitigate or reverse negative fire impacts. Impacts are related to fire regime and its interactions with ecosystem fire resilience. In the case of severe fire regimes, the main ecological impacts affect nutrient budget, soil-erosion risk, and the reduction of biodiversity. Planning postfire restoration requires the identification of the specific degradation processes triggered by fire, including their time and spatial dimensions, and vulnerable ecosystems. Restoration should address identified vulnerable areas, and mitigate soil erosion and runoff risk in the short term, and the recovery of nutrient cycling and keystone plant species in the longer term. We present the approach developed for assessing postfire restoration in the Mediterranean basin based on the prediction of soil-erosion risk and vegetation vulnerability.

This project studied the amino acid composition of samples taken from an experiment of in situ incubation of plant debris, mixed with mineral earth, to identify changes during decomposition. Medicago sativa debris, and Eucalyptus globulus and Pinus halepensis ground litter, were mixed with a OM‐poor mineral earth, and buried in the soil at 5, 20, and 40 cm depth, for 2 years. The total amino acid composition of the final samples was compared with that of the initial ones. The amino acid composition of the several initial mixtures was quite similar. Also, the differences between initial and incubated samples were small, but still large enough to detect consistent changes. The pattern of change was consistent for only nine amino acids: Gly consistently increased, whereas Lys, His, Leu, and (to a lesser extent) Arg, Tyr, Phe, Ser, and Tau consistently decreased. The ratio Gly/(Lys+His+Leu+Arg+Tyr+Phe+Ser) is taken as the amino acid signature (AaS). This ratio increased from about 0.30–0.35 in the un...

The purpose of this study was to determine whether fire recurrence modifies the regeneration capacity of Quercus coccifera garrigues in the Valencia region (eastern Spain). We studied several areas with different fire recurrences (1, 2 and 3 fires in 16 years), all of which had sustained a common last fire in 1994. Three-and-a-half years after the last fire, differences between the 3 fire recurrences were not detected with respect to total plant cover and Q. coccifera cover, with a mean value between 92 and 76%. On the most frequently burned sites, herbaceous and subshrub species cover showed a tendency to increase, while that of the obligate seeding shrub, Ulex parviflorus, decreased with both fire frequency and shorter last-fire interval. The most recurrently burned areas with the shortest last-fire intervals presented higher species richness, which mainly affected the herbaceous and subshrub species group, and of these, the hemichryptophytes. The major effect of fire recurrence was the significant decrease in stem and total biomass of Q. coccifera in the three studied sites. Three-and-a-half years after the fire, the mean total biomass values were around 1500, 1000 and 700 g. m−2 in the garrigues with 1, 2 and 3 fires respectively. Stem production was more affected than leaf production. Leaf area index values showed the same pattern as leaf biomass. Recurrent fires also caused a decrease in net primary production measured the fourth year after fire. The results point to the fact that fire recurrence can cause depletion in garrigue productivity and recovery capacity in southern areas, in contrast with the high resilience observed in northern Mediterranean garrigues.

The evergreen Nothofagus betuloides and deciduous Nothofagus pumilio live close together in Tierra del Fuego. The fact that these two species rarely form mixed forests suggests that the soil factor can contribute to the distribution of two species on a local scale. Most of these forests are undisturbed; therefore, soil characteristics may reflect both the influence of the species and of the dominant pedogenetic processes. In this paper, we aim to study how soil characteristics can affect nutrient cycling, the strategies of tree nutrition and the distribution of Nothofagus forests in Tierra del Fuego. Twenty-two soils in these two types of forests in contrasted topographic positions were sampled and analysed. The dominant soil processes were waterlogging in the evergreen forest and podzolisation in the deciduous one. Within each type of forest we observed large variability in soils. Nutrient-poor litter slowed down nitrogen cycling. However, phosphorus mobilisation was high in nutrient-poor environments because of low pH and waterlogging. Chemical and biological characteristics of the Oa horizon were able to discriminate between forest types while mineral soil characteristics were not. Biological activity of the organic horizons was limited by low pH and, in N. betuloides forests, also by waterlogging conditions. According to this pattern, N. betuloides grows in less fertile soils and thus has lower nutrient concentrations in leaves. In contrast, N. pumilio grows in soils with higher fertility and consequently has high nutrient content in leaves. Despite growing in low fertility sites, N. betuloides grows at a rate similar to that of N. pumilio. This suggests that the evergreen species is more efficient in using nutrients and better adapted to waterlogging conditions.

Physical protection is one of the most important ways for stabilization of organic carbon (OC) in soils, and in order to properly manage soils as a sink for carbon, it is necessary to know how much OC a given soil could protect. To this end, we studied individual horizons taken from 16 soil profiles under Quercus rotundifolia stands, all over calcareous parent materials. Horizons were subjected to a sequential extraction using solutions of sodium polytungstate (NaPT) of increasing density: (i) NaPT d =1.6, using slight hand agitation, to obtain the free light fraction (FL); (ii) NaPT d =1.6 and ultrasonic dispersion, to obtain the Occluded Fraction I (Ocl I); (iii) NaPT d =1.8, to obtain the Occluded Fraction II (Ocl II); and (iv) NaPT d =2.0, to obtain the Occluded Fraction III (Ocl III). The fraction of density>2.0 are taken as dense fraction (DF). The free organic matter was further divided into FL>50 (retained by a 50 μm mesh: coarse organic fragments) and FL 50 and FL For both OC and N, the fractions FL>50 and DF are dominant; the rest of the fractions are of much lower quantitative importance. In H horizons and in most A horizons, most of the OC and N are free, whereas in B horizons both OC and N are mostly protected. Overall, the percentages of free OC and N are very high and are currently amongst the highest ever recorded. Organic matter recalcitrance is lowest in the two most protected fractions (Ocl III and especially DF), and highest in the first occluded fractions (Ocl II and especially Ocl I). The free organic matter (FL>50 fraction) has an intermediate quality: it includes recognizable plant fragments, but the indicators tested (recalcitrance, carbohydrate content, cellulose to total carbohydrates ratio) suggest that it is not always the most fresh and non-decomposed fraction. There are clear maxima for both protected OC and N, which can be approached by curve fitting. By exponential fit, the obtained maxima are 84.1 g of OC and 7.7 g of N kg −1 of mineral particles

The quality of soil organic matter (OM) depends on its distribution among labile and recalcitrant pools and the quality of each pool considered. OM quality is assumed to decrease as decomposition proceeds, but to verify this assumption it is necessary to define quality in operative terms. Here we study the change in OM quality during decomposition of mixtures of four plant materials (Medicago sativa whole ground plants, and ground litter of Eucalyptus globulus, Quercus ilex and Pinus halepensis) with a mineral red earth, incubated at different depths (5, 20, and 40 cm) for 2 years. OM quality was evaluated from acid hydrolysis, considering three pools: (a) Labile Pool I, obtained by hydrolysis with 5 N H2SO4 at 105 °C for 30 min; (b) Labile Pool II, obtained by hydrolysis with 26 N H2SO4 at room temperature overnight, then with 2 N H2SO4 at 105 °C for 3 h; and (c) Recalcitrant Pool, the unhydrolyzed residue. In agreement with previously published results, the recalcitrant C/total OC (RIC), and recalcitrant N/total N (RIN) ratios are regarded as indicators of global OC and N quality. In addition, in Labile Pools I and II, the ratio carbohydrate C/polyphenol C is used as indicator of OC quality. The main findings obtained by applying this approach can be summarized as follows: (1) In undecomposed plant materials, initial RIC ranged from 25% to 60% (Medicago and Pinus mixtures, at extreme values). Throughout decomposition, RIC values increased strongly (Medicago mixtures), slightly (Eucalyptus), or were roughly maintained (Quercus and Pinus), suggesting that strong decreases in OC quality occur only for easily decomposable plant materials. (2) Initial RIN values were between 15% and 30%, i.e., much lower than RIC ones. In contrast with the behaviour of RIC, the RIN values strongly increased in all cases, or, in other words, N quality clearly decreased for all plant materials, owing not only to a lower mineralization of the recalcitrant N, but also to a net incorporation of N to this pool. The amount of incorporated N is significantly related to the initial lignin content of the incubated plant material. Such incorporation seems to occur during wet periods; in contrast, its relationship with temperature was hardly detectable. No similar phenomenon was detected for recalcitrant C. (3) The 13C-CPMAS-NMR spectra of the recalcitrant pool showed prominent peaks in the 0–45 ppm region, which corresponds to the alkyl C and accounts for up to 50% of the total unhydrolyzable C in Quercus mixtures. In contrast, the aromatic zone, 110–160 ppm, was poorly apparent. These features were maintained more or less intact during the 2 years of field incubation, and suggest that lipidic polymers represent a substantial part of the recalcitrant pool. (4) Throughout the decomposition process, the ratio Labile Pool II/Labile Pools I+II decreased for carbohydrates, and increased for phenolic compounds. The use of these ratios is suggested to evaluate the degree of decomposition of plant residues. In Labile Pool I the ratio carbohydrate C/polyphenol C remained the same, whereas for Labile Pool II this ratio decreased strongly, suggesting that the changes in quality may be restricted to a single pool. (5) Samples incubated in upper horizons (5-cm depth) were subjected to a much drier pedoclimate than those incubated at deep layers (20 and 40 cm), resulting in a slower mineralization of both the labile and the recalcitrant pools of C and N. Nevertheless, on a mineralized OC basis, most indicators of quality did not differ statistically between depths. Hence, the drought in the upper horizon retarded the decomposition, but did not result in a different biochemical evolution. Because of its simplicity, chemical fractionation into three pools is a useful approach to characterize biochemical changes in C and N quality during plant residue decomposition.

The relationship between particle size and mineralization has been well established for organic carbon (OC). It has repeatedly been reported that mineralization decreases with decreasing particle size, and that the OC of fine particles (fine silt, clay) has a much slower turnover than that of coarse organic fragments. For nitrogen (N), however, the available data are contradictory. Here, we study the behaviour of OC and N in a range of size fractions over two years of field decomposition. To this end, Medicago sativa ground plants, and Quercus ilex ground litter were mixed with an OC-poor red earth, and were buried at 5 and 40 cm depth, in nylon mesh bags. Selected samplings were taken to study the changes in the distribution of OC and N among the size fractions, obtained by ultrasonic dispersion: coarse sand (2000–200 μm), fine sand (200–50 μm), coarse silt (50–20 μm), fine silt (20–2 μm), and clay ( 2 O 2 . The losses of OC (as % of the total OC in the size fraction) consistently decreased with decreasing fraction size, and loss of this element was minimal for clays. In Quercus mixtures, a net input of OC to clays was observed, indicating OC redistribution during decomposition. The losses of N did not show such a clear pattern; in Medicago mixtures, no relationship with size was observed, whereas in Quercus mixtures, they fell slightly with decreasing size. Clay acted as a net sink for N in Quercus mixtures, especially at 40 cm depth. Overall, the clay-occluded OC and N was the most stable fraction. In most cases, losses were significantly greater at 40 cm depth; when a net input of either OC or N was observed for a given fraction, the input was also greater at this depth. Most detectable changes were observed in the light subfraction ( d d ≥2.0) changes were much smaller. The OC/N ratios of the coarse fractions (coarse sand, fine sand) decreased dramatically, whereas those of finer fractions were largely unaltered. There was a clear trend towards the uniformity of the OC/N ratios of the fractions, and we suggest that this trend might, to some extent, control the N dynamics. Hence, while OC dynamics is driven mainly by physical availability, which depends on fraction size, that of N is also controlled by the quality of the organic debris (OC/N ratio, among other indicators), and the interaction of both controlling factors may result in a size–mineralization relationship that is not as clear as that observed for OC.

Wildfires produce a significant release of gases and particles affecting climate and air quality. In the Mediterranean region, shrublands significantly contribute to burned areas and may show specific emission profiles. Our objective was to depict and quantify the primary-derived aerosols and precursors of secondary particulate species released during shrubland experimental fires, in which fire-line intensity values were equivalent to those of moderate shrubland wildfires, by using a number of different methodologies for the characterization of organic and inorganic compounds in both gas-phase and particulate-phase. Emissions of PM mass, particle number concentrations and organic and inorganic PMx components during flaming and smouldering phases were characterized in a field shrubland fire experiment. Our results revealed a clear prevalence of K+ and SO42- as inorganic ions released during the flaming-smouldering processes, accounting for 68 to 80% of the inorganic soluble fraction. During the residual-smouldering phases, in addition to K+ and SO42-, Ca2+ was found in significant amounts probably due the predominance of re-suspension processes (ashes and soil dust) over other emission sources during this stage. Concerning organic markers, the chromatograms were dominated by phenols, n-alkanals and n-alkanones, as well as by alcohol biomarkers in all the PMx fractions investigated. Levoglucosan was the most abundant degradation compound with maximum emission factors between 182 and 261 mg kg-1 in PM2.5 and PM10 respectively. However, levoglucosan was also observed in significant amounts in the gas-phase. The most representative organic volatile constituents in the smoke samples were alcohols, carbonyls, acids, monocyclic and bicyclic arenes, isoprenoids and alkanes compounds. The emission factors obtained in this study may contribute to the validation and improvement of national and international emission inventories of this intricate and diffuse emission source. This study was funded by the FEEDBACKS-PROMETEO Programme (Prometeo 2009/006), and the CONSOLIDER-INGENIO 2010 Programme (GRACCIE, CSD2007-00067). Support for infrastructure projects of scientific and technological co-financed with the European Regional Development Fund (FEDER). The CEAM Foundation is supported by Generalitat Valenciana (GVA).

High-intensity and fast-spreading wildfires are natural in the Mediterranean basin. However, since 1960, wildfire occurrence has increased because of changes in land use, which resulted in extensive land abandonment, increases in the fuel load and continuity in the landscape. The level of soil degradation related to wildfire occurrence depends on fire recurrence, topography of the site, intensity of the soil erosion processes and plant cover post-fire regeneration rate. Therefore assessing fire impacts on soil properties is critical to quantify land degradation processes and to assess post-fire restoration plans. This article reviews the changes in soil nutrient status of Mediterranean ecosystems affected by wildfires by focusing on the interactions between the different drivers and factors, and the underlying processes of these changes. Articles dealing with wildfires in areas belonging to the Mediterranean basin and characterized by an annual average rainfall of 300–900 mm and a mean annual temperature around 14–19 °C, have been reviewed. The data show that the soil nutrient content in Mediterranean drylands affected by wildfires depends on the vegetation type, fire recurrence and fire intensity. Immediately after a fire, the nutrient content in both the O and A horizons often increases because of ash deposition, nutrient release from the burnt vegetation and formation of stable nutrient forms. Ash deposition persistence on the soil surface is one of the most important factors in determining the soil nutrient content both immediately after a fire and for the long-term. For the restoration of burned habitats it is important to know the content and the spatial distribution of nutrients in the soil because this can act as a limiting factor to vegetation recovery. Carbon and nitrogen pools in the soil have been recognized as fundamental to vegetation recuperation after a fire. To promote the accumulation and retention of nutrients in soil after a fire, it is important to stabilize the burnt site by applying post-fire measures that limit soil erosion, surface runoff and wind loss of the ash. Depending on the plant species and the time elapsing between consecutive wildfires, fire is responsible for the transition from mature ecosystems (i.e. conifer forests) to shrublands, which are poorer in soil nutrient status. Wildfire occurrence can be reduced by planting fire-resilient plants in fire-prone areas. To define the best post-fire and restoration treatments, the impacts of fire on both the O and the A horizon as well as the impacts of different post-fire treatments on the soil nutrient content require further study.

13C labelled plant material was incubated in situ over 2 to 3 years in 8 conifer forest soils located on acid and limestone parent material along a north-south climatic transect from boreal to dry Mediterranean regions in western Europe. The objectives of the experiment were to evaluate the effects of climate and the soil environment on decomposition and soil organic matter dynamics. Changes in climate were simulated using a north-to-south cascade procedure involving the relocation of labelled soil columns to the next warmer site along the transect. Double exponential, decay-rate functions (for labile and recalcitrant SOM compartments) vs time showed that the thermosensitivity of microbial processes depended on the latitude from which the soil was translocated. Cumulative response functions for air temperature, and for combined temperature and moisture were used as independent variables in first order kinetic models fitted to the decomposition data. In the situations where climatic response functions explained most of the variations in decomposition rates when the soils were translocated, the climate optimised decomposition rates for the local and the translocated soil should be similar. Differences between these two rates indicated that there was either no single climatic response function for one or both compartments, and/or other edaphic factors influenced the translocation effect. The most northern boreal soil showed a high thermosensitivity for recalcitrant organic matter compartment, whereas the labile fraction was less sensitive to climate changes for soils from more southern locations. Hence there was no single climatic function which describe the decay rates for all compartments. At the end of the incubation period it was found that the heat sum to achieve the same carbon losses was lower for soils in the north of the transect than in the south. In the long term, therefore, for a given heat input, decomposition rates would show larger increases in boreal northern sites than in warm temperate regions. The changes in climate produced by soil translocation were more clearly reflected by decomposition rates in the acid soils than for calcareous soils. This indicates that the physicochemical environment can have important differential effects on microbial decomposition of the labile and recalcitrant components of SOM.

Differential thermogravimetry (DTG), differential scanning calorimetry (DSC), and stepwise thermogravimetry (STG), together with two acid hydrolysis methods (hydrolysis with hydrochloric acid in a single step, and hydrolysis with sulfuric acid in two steps), were evaluated to determine the quality of four plant materials (Medicago sativa, Eucalyptus globulus, Quercus ilex, and Pinus halepensis) before and after mixing with a red earth. These quality indices were then compared with the same materials in the field, whether their decomposition could be predicted. All the thermal methods gave poor results. In both DTG and DSC, the presence of the mineral matrix gave rise to strong distortions in the spectra. Since the spectrum of any mixture is not simply the sum of the spectra of the two components (organic matter + mineral matter), these distortions could not be corrected by simply subtracting the spectrum of the red earth alone. STG trials also gave poor results, because the presence of the minera...

Reports on the dynamics of carbon and nitrogen at different depths in soil profiles usually describe a higher mineralization of both at upper horizons. Nevertheless, under Mediterranean climate, upper soil horizons are strongly affected by drought, especially in summer, and may offer pedoclimatic conditions less favorable to microbial activity than deep soil layers. Therefore, decomposition could be slower in the upper soil layers. To test this hypothesis, mixtures of Medicago sativa ground plants and soil material were incubated in the field, at 5, 20, and 40 cm depth, in nylon mesh bags. Mineralization of carbon and nitrogen was studied for two years. At 5 cm, mineralization of both elements was lower, and no differences were found between 20 and 40 cm. After two years of field incubation, the remaining carbon (as a percentage of the initial content) was 27.95 % +/- 0.88 at 5 cm depth, 19.87% +/- 0.77 at 20 cm, and 18.78 % +/- 1.19 at 40 cm. Mineralization of nitrogen exceeded that of carbon. After two ...

Fire may generate soil degradation and accelerate erosion processes, depending among other factors, on the regeneration capacity of the ecosystem. Conservation measures will be beneficial in those fragile systems where a high degradation hazard is estimated. Mulching treatment was evaluated in order to establish its efficiency in protecting soil and preventing runoff generation in a semiarid area affected by a wildfire. Straw mulch was applied at 200 g m‐2 in three replicated plots. Paired mulched and control plots were established in a three block experimental design. Runoff, sediment yield, plant cover, and dynamics of soil physical properties were measured in these plots over a 2‐year period. Most of the plant regeneration after the fire resulted from resprouting of the dry grassland species, dominated by Brachypodium retusum. Total plant cover was only 50% two years after passage of the fire. Runoff and sediment yield were significantly greater from control plots. Soil loss from control plots was abou...

In occidental Europe, Spain is one of countries the most severely affected by desertification (Arnalds & Arsher 2000). Particularly, South-eastern Spain is considered as one of the most threatened areas by desertification in Mediterranean Europe (Vallejo 1997). In 2003, the Valencia Regional Forest Service implemented a restoration demonstration project in this area. The project site is a small catchment (25 ha) located in the Albatera municipality. The catchment is highly heterogeneous, with terraced slopes, south-facing slopes and north-facing slopes. The restoration strategy was based on planting evergreen trees and shrubs which can grow quickly after disturbances, and on field treatments aimed at maximizing water collection (micro-catchments, planting furrows), organic amendment (compost), and conservation (tree shelters, mulching). On south landscape unit, the whole category of restoration treatments was applied : water micro-catchment + Tubex tree shelters + mulching & compost, while on north landscape unit : netting tree shelters + mulching & compost only were applied, while in terrace landscape unit : furrows + netting tree shelters + mulching & compost were applied. Survival and growth of the planted seedlings were used as metrics of restoration success. To assess the effects of the treatments applied for soil conservation, soil loss rates (from 2005 to 2009) were evaluated using the erosion pin method. We conclude that, despite the limiting conditions prevailing on the south unit, this landscape unit showed the highest survival and growth plant rates in the area. The best seedling performances on the south landscape unit were probably due to the highest technical efforts applied, consisting in the water micro-catchment installation and the Tubex plant shelters addition. In addition, soil loss rates followed decreasing trends throughout the assessment period. Soil loss rates were highest on south landscape unit in comparison with the other landscape units, due to the more accentuated relief. North landscape unit and terrace unit showed a net soil mass gain, probably reflecting the trapping of sediments produced by plantation works., La désertification est un phénomène mondial (Arnalds & Arsher 2000). En Europe occidentale, l’Espagne est le pays le plus sévèrement touché. Particulièrement, le sud-ouest de l’Espagne est considéré comme l’une des zones les plus désertifiées de l’Europe méditerranéenne (Vallejo 1997). En 2003, le service forestier régional de Valence a exécuté un projet d’aménagement forestier expérimental dans cette zone. La zone d’étude est un bassin versant (25 ha), localisée dans la commune d’Albatera, Espagne. Le bassin versant est très hétérogène, constitué de trois unités environnementales : une zone en terrasses, un versant sud (adret) et un versant nord (ubac). La stratégie de restauration écologique adoptée dans cette étude est basée sur l’introduction des plantules forestières d’arbres et d’arbustes qui se caractérisent par une croissance rapide après perturbation, et de l’application d’actions de restauration écologique visant à optimiser les ressources hydriques (micro-bassins, sillons de plantation), l’amendement organique au sol (compost), la conservation de plantes (protecteurs de plantules) et la préservation des sols (paillage). Dans l’unité sud nous avons appliqué l’ensemble des traitements de préparation du terrain pour la plantation (micro-bassins + protecteurs de plantules Tubex + paillage et compost), pour l’unité nord nous n’avons appliqué que les protecteurs de plantules en maille + paillage et compost. Par contre, pour l’unité de terrasses, nous avons appliqué les sillons de plantation + protecteurs de plantules en maille + paillage et compost. La survie et la croissance en hauteur des plantes introduites sont utilisées comme des paramètres métriques pour l’évaluation du succès de restauration. Afin d’évaluer l’effet de ces actions de restauration sur la conservation des sols, nous avons mesuré des taux d’érosion (de 2005 à 2009) en utilisant la méthode des clous d’érosion. Malgré les conditions bioclimatiques limitantes présentes dans l’unité sud, celle-ci a enregistré les pourcentages de survie des plantes et les croissances en hauteur les plus élevés. Les meilleurs résultats obtenus dans l’unité sud pour la survie et la croissance en hauteur des plantules sont probablement causés par les efforts techniques appliqués, et qui consistent dans l’installation de micro-bassins et l’application de protecteurs de plantules Tubex. Généralement, les taux d’érosion ont suivi une tendance décroissante durant la période de suivi ; les taux les plus élevés sont observés dans l’unité sud, principalement dus aux propriétés topographiques très accidentées de cette unité. Les unités expérimentales nord et de terrasses ont eu un gain de la masse du sol, qui reflète probablement l’accumulation des sédiments causée par la plantation., Kribeche H., Bautista Susana, Chirino Esteban, Vilagrosa Alberto, Vallejo V. Ramon. Effects of landscape spatial heterogeneity on dryland restoration success. The combined role of site conditions and reforestation techniques in southeastern Spain. In: Ecologia mediterranea, tome 38 n°1, 2012. pp. 5-17.

Context: Maritime Pine forests cover important mountain areas in Portugal and are known to be a particularly fire-prone forest type. Understory composition plays an important role in maintaining biodiversity and ecosystem services after recurrent wildfires. Aims: This study aims to improve the knowledge on the germination ecology of understory species of Maritime Pine forests, focusing on the importance of seed provenance, including in relation to germination enhancement by heating. Methods: The selected species were Cistus ladanifer L., Erica australis L., Erica umbellata L., Pterospartum tridentatum L. (Willk), and Genista triacanthos Brot. Seeds were collected from two or three distant populations. Besides a control treatment, two heating regimes were applied, i.e., 100°C during 5 min and 80°C during 30 min. Results: Heating treatments significantly enhanced germination in four out of the five species. Differences between provenances were most evident for C. ladanifer and E. australis, especially following the heating treatments. Overall, the seeds from the southern provenances germinated better and, at the same time, were smaller. Conclusion: The present results confirmed that seed provenance should not be ignored as a key factor in germination ecology, so that further work is needed to untangle the roles of environmental and genetic factors in the observed differences between provenances. published

In this chapter we start by making an overview of plant adaptations to fire and post-fire response types, which will determine the post-fire management alternatives that might be used in specific forest and shrubland types. Some implications of climate change on fire regimes and plant responses are addressed, and the more fire prone forest types in Southern Europe are identified. We finish by discussing the major post-fire questions and management alternatives faced by forest managers, common to all forest and shrubland types affected by wildfires. These include measures to protect soil and reduce erosion risk, how to manage the burned trees, the use of restoration or conversion, active or indirect restoration, the management of herbivory, alien species, and pests and diseases.

This chapter sets the scene for post-fire management and restoration approaches in Southern Europe. It starts with a short overview of wildfire trends in Europe, and then introduces the main questions that need to be addressed when managing burned areas. Key concepts in restoration ecology, as well as a framework for planning post-fire restoration, are presented. The importance of the time and spatial scales for management is also addressed.

The current chapter describes the ecological context and post-fire management practices for the most important and fire-prone coniferous tree species in the Mediterranean Basin, the serotinous pine trees. The state of art about evolution, habitat and adaptive strategies of Pinus halepensis Mill, Pinus brutia Ten. and Pinus pinaster Aiton are included. The management of burned areas, from emergency to long-term actions, are included but also the influence of climate change and the changing fire dynamics are discussed. To illustrate it, we included some case studies for the serotinous pine species in both Eastern and Western Mediterranean Basin.

In degraded Mediterranean woodlands, nutrients, in addition to water, may be the major factors controlling reforestation success. But information on nutritional status of planted seedlings is scarce. We aimed to evaluate the nutritional status and field performance of Pinus halepensis and Quercus ilex seedlings planted on two characteristic Mediterranean forest soils developed from marl and limestone. We used root growth response to localized N and P enrichment, and foliar analysis as indicators of nutrient limitation. Vermiculite cores enriched with P showed higher root density than N-enriched and control cores, particularly on soils derived from marl. Three years after planting, seedlings showed low foliar P and K as compared to other species and adult trees. Principal Component Analysis conducted on foliar macronutrient concentration clearly separated species and soil type. Foliar K and Mg depended on soil type (higher on limestone and marl, respectively), whereas N, P and Ca concentration in leaves and needles differed between species (higher N and P in pine, higher Ca in oak). Survival and growth depended on species and site, but we found no effect of soil type on these variables, suggesting that seedling performance may not be strongly affected by nutrient status within the range of soils evaluated., État nutritionnel et comportement de jeunes arbres plantés dans des terrains méditerranéens dégradés. Le succès des reboisements dans les forêts méditerranéennes dégradées peut être conditionné par la disponibilité en eau et en nutriments. Cependant, il existe peu d'information sur l'état nutritionnel des semis en reboisement. Nous avons évalué l'état nutritionnel et le développement en conditions de terrain des semis de Pinus halepensis et de Quercus ilex plantés dans deux types de sols caractéristiques des forêts méditerranéennes : les marnes et les calcaires. La réponse de la croissance des racines en des points enrichis en N et P et les analyses foliaires furent utilisées comme indicateurs de limitation nutritionnelle. Les carottes de vermiculite enrichies en P montrèrent une plus forte densité de racines que celles enrichies en N et celles des témoins, spécialement sur les marnes. Trois ans après la plantation, les semis présentèrent une faible teneur en P et K foliaire en comparaison avec d'autres espèces et arbres adultes. L'analyse en composantes principales de la concentration foliaire de macro nutriments, sépara clairement les espèces et le type de sol. La concentration foliaire de K et Mg dépendait du type de sol (respectivement plus grande sur le calcaire et la marne) alors que la concentration en N, P et Ca fut différente entre les espèces (plus importante en N et P chez les pins, et en Ca chez les chênes). La survie et la croissance dépendaient de l'espèce et du site de plantation, mais on n'a pas rencontré d'effet du type de sol sur ces variables, ce qui suggère que le développement des semis ne peut pas être fortement déterminé par l'état nutritionnel des sols dans la gamme de ceux que nous avons évalués.

We investigated the response of Pinus halepensis seedlings to the application of biosolids enriched with Cu, Ni and Zn on three Mediterranean forest soils under semiarid conditions. One-year-old seedlings were planted in lysimeters on soils developed from marl, limestone and sandstone which were left unamended, amended with biosolids, or amended with biosolids enriched in Cu, Ni and Zn. Enriched biosolids increased plant heavy metal concentration, but always below phytotoxic levels. Seedlings receiving unenriched biosolids showed a weak reduction in Cu and Zn concentration in needles, negatively affecting physiological status during drought. This effect was alleviated by the application of enriched sludge. Sewage sludge with relatively high levels of Cu, Zn and Ni had minor effects on plant performance on our experimental conditions. Results suggest that micronutrient limitations in these soils may be alleviated by the application of biosolids with a higher Cu, Zn and Ni content than those established by current regulations.

La Fundación Centro de Estudios Ambientales del Mediterráneo desarrolla desde 1991 un amplio programa de I+D+I sobre "Restauración de la cubierta vegetal en la Comunidad Valenciana", por iniciativa de la Generalitat de esta Comunidad y con el apoyo financiero de la misma y de los diversos programas de investigación nacionales y europeos. Dicho programa de I+D analiza las causas de la desertificación en ambiente mediterráneo semiárido y seco-subhúmedo y desarrolla procedimientos y tecnologías para mejorar la prevención de incendios y la restauración de ecosistemas degradados. Las actividades se realizan en estrecha colaboración con los servicios forestales de la Comunidad Valenciana, e incluyen desde investigación orientada a la resolución de problemas de gestión forestal hasta la puesta en marcha de proyectos piloto de demostración.