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Trabajo presentado en Falta INTECOL 2022, celebrado en Ginebra (Suiza) del 28 de agosto al 02 de septiembre de 2022., We analyzed Quercus ilex (holm oak) recruitment during the last 50 years in eastern Spain, where aridity has increased in the last century due to temperature increase. We searched for recruits in 5.3 ha plots along a gradient of deforestation intensity-from maximum forest cover to treeless areas-in two contrasting climates within the species' range; one at the lower limit of the species' precipitation niche (450 mm, semi-arid) and one at the optimum of that niche (750 mm, sub-humid), all other environmental factors affecting recruitment being equal. We established the age of recruits from root collar measurements of recruits and using a model relating root collar diameter to age estimated from the number of tree rings. We found a large difference in recruitment between semi-arid and sub-humid populations. In semi-arid populations, we found less than 50 plants.ha-1, even when Q. ilex adult tree cover and nurse plant cover were similar to those of nearby sub-humid populations. In the sub-humid populations, recruitment was very high, around 1000 plants.ha-1. Despite its high longevity and ability to sprout after disturbances or stress, the recruitment of holm oak in the forests of the semiarid areas studied is too low to guarantee the long-term replacement of Quercus ilex forests under climate change scenarios, suggesting that forests dominated by this species in the semiarid region are in danger of disappearing.

Trabajo presentado en el 1st Meeting of the Iberian Ecological Society (SIBECOL) & XIV AEET (Asociación Española de Ecología Terrestre) Meeting, celebrado en Barcelona (España), del 4 al 7 de febrero de 2019, In this study, we analyze the recruitment of Q. ilex in the Iberian Range, where this species still forms extensive forests, is recovering from the intense past human use (mainly coal and grazing with sheep and goats) and where the average temperature has increased over the last century. To unravel the effect of climate and changes in use, we searched for recruits aged 50 years or less in several plots of 5.3 ha along a gradient of intensity of deforestation, from the maximum forest cover to areas without trees, in two contrasting climates within the range of the species; one in the lower limit (450 mm, semi-arid) and the other in the optimum of that range (750 mm, sub-humid). The age of the recruits was established from models relating the diameter of the root-collar and the number of tree rings. A great difference was found in the recruitment between the semi-arid and sub-humid populations. In semi-arid populations, less than 50 plants.ha-1 were found, even when the cover of adult Q. ilex trees and the coverage of nurse plants were similar to that of nearby populations that received a greater amount of precipitation and exhibited a very high recruitment, about 1000 plants.ha-1. Despite the great longevity and capacity to regrowth after disturbances or stress, the recruitment of Q. ilex in semi-arid areas was too low to ensure long-term replacement of populations, suggesting that the forests dominated by this species in the semi-arid should be considered as fossil forests.

[ES] Mediante un diseño factorial, se analizaron las consecuencias de la actuación simultánea de dos factores de cambio global sobre las propiedades de los ecosistemas. Usamos como factores el clima y la pendiente del terreno como aproximaciones respectivamente del efecto del cambio climático esperado para mitad del siglo XXI y del efecto de la deforestación. Como propiedades del ecosistema se usaron variables de vegetación y suelo. Los resultados muestran un efecto negativo del cambio climático y de la erosión sobre la riqueza de especies y las propiedades del suelo cuando ambos actúan de manera aislada. Ahora bien, cuando ambos factores actúan simultáneamente, el efecto total es menor que la suma del efecto de ambos por separado, menos para la cobertura vegetal en que el efecto fue igual a la suma. También encontramos que las propiedades del suelo se correlacionan más fuertemente con la riqueza de especies que con la cobertura vegetal., [EN] In this study we analyze the consequences on ecosystems of the simultaneous action of several factors of global change. For this, we analyze separately and simultaneously the consequences of climate change and erosion on vegetation and soil variables using a factorial design of two climates and two terrain slopes. These factors were used as approximations to the effect of climate change expected for the middle of the 21st century and the effect of deforestation. The results indicate that when climate change and erosion act independently, their effects are negative on all variables. However, when both factors act simultaneously, their effects on species richness and soil properties are lesser than the sum, except in the case of vegetation cover, where the effects of climate change and erosion add up. We also find that soil properties correlate more strongly with species richness than with plant cover., Esta investigación se pudo realizar gracias al Proyecto CGL2005-03912/BOS del Plan Nacional de Investigación, Desarrollo e Innovación

[ES]: Dadas las predicciones de cambio climático global, es necesario prepararse para dichos cambios y, en su caso, para responder a las consecuencias que pueden tener sobre nuestros montes. Ello requiere del desarrollo de herramientas adecuadas. En este sentido, y dadas las íntimas relaciones que existen entre clima, vegetación y erosión, la utilización de los actuales gradientes de aridez y degradación como contexto de estudio nos permite explorar las adaptaciones de las plantas a la sequía y la erosión. En el presente trabajo se pretende identificar las variaciones en algunos rasgos morfológicos y funcionales de las especies de encinares mediterráneos abiertos cuando son sometidas a un incremento de la aridez y de la erosión. Para ello se han medido y analizado distintas características relativas a las hojas, las semillas, las raíces, los tallos y la longevidad de un conjunto de especies inventariadas en comunidades de plantas presentes a lo largo de un gradiente de aridez y sometidas a distintos niveles de erosión. Los resultados obtenidos indican que la erosión y la aridez juegan un papel importante en la selección de los rasgos de las especies. De forma general, la erosión tiende a favorecer a las especies perennes, leñosas, con una raíz pivotante y unos propágulos de peso relativamente elevado, mientras que la aridez favorece a las especies anuales, no rebrotadoras, pero con raíz pivotante y caracterizadas por una elevada área foliar específica y un bajo contenido foliar en materia seca. Esta información puede resultar muy valiosa a la hora de seleccionar especies para la lucha contra la erosión en un escenario de cambio climático., [EN]: Identification of morphological and functional types of traits in plant communities of the Teruel Province for the selection of species useful to combat desertification in the context of climate change. In the actual context of global change, we need to be prepared to respond to the consequences of future changes on our ecosystems with the development of appropriate tools. Due to the strong relationships between climate, vegetation and erosion, the use of present gradients of aridity and degradation allows for the exploration of plant adaptations to drought and erosion. In this study, we aim to identify the variations in some morphological and functional traits of species living in sparse Mediterranean oak forests that are exposed to an increase in aridity and erosion. We measured and analyzed different plant traits related to leaves, seeds, stems and longevity of species living in plant communities along an aridity gradient and suffering different levels of erosion severity. Results indicate that erosion and aridity play an important role in plant trait selection. In general, erosion enhances the presence of perennial, woody, tap-rooted species with quite heavy propagules, whereas aridity enhances annual, non-sprouting, but tap-rooted species displaying high specific leaf area and low leaf dry matter content. These results can be very useful for species selection in order to combat desertification in the context of climate change.

Trabajo presentado en la Ecological Society of America (ESA) Annual Meeting 2017 celebrado en Portland, Oregon (Estados Unidos), del 6 al 11 de agosto de 2017

Trabajo presentado en la XIV MEDECOS & XII AEET Meeting. Human driven scenarios for evolutionary and ecological changes, celebrado en Sevilla (España) del 31 de enero al 4 de febrero de 2017, Drylands are experiencing major alterations as a result of complex interactions between climatic fluctuations and disturbances caused by human activities. Theoretical models suggest that these ecosystems are particularly prone to suffer critical transitions with abrupt non-linear changes in their structure and functions in response to climate variation and human disturbance. How drylands undergo environmental change has become an important issue in ecology which needs empirical data to validate theoretical models. We studied the functional response of holm oak (Quercus ilex) woodlands to human disturbance along an aridity gradient (from semi-arid to sub-humid conditions) in eastern Spain, using (a) remote-sensing estimations of precipitation-use-efficiency (PUE) from enhanced vegetation index (EVI) observations performed in 231x231 m plots of the Moderate Resolution Imaging Spectroradiometer (MODIS) and (b) soil parameter determinations (extracellular soil enzyme activity: phosphatase, ß-glucosidase and urease, and associated nutrient cycling processes) from soil sampled in the same plots. We evaluated and compared the shape of the relationship between ecosystem functionality (in terms of PUE and soil parameters) and disturbance intensity for our holm oak sites along the aridity gradient by fitting the experimental data to linear vs. non-linear model equations. Overall, our results demonstrated that climatic conditions along the aridity gradient played a relevant role in the shape of the functional response of Quercus ilex woodlands to human disturbance. Whereas sub-humid areas showed a linear decrease with an increasing disturbance intensity, semi-arid areas were characterized by non-linear dynamics with the existence of abrupt changes at critical disturbance intensity values.

Trabajo presentado en la American Geophysical Union Fall Meeting, celebrado en New Orleans (Estados Unidos) del 10 al 15 de diciembre de 2017, Theoretical models predict that drylands are particularly prone to suffer critical transitions with abrupt non-linear changes in their structure and functions as a result of the existing complex interactions between climatic fluctuations and human disturbances. How drylands undergo functional change has become an important issue in ecology which needs empirical data to validate theoretical models. We aim at determining the response of Mediterranean holm oak woodlands to human disturbance in three different climatic areas from Eastern Spain, under the hypothesis that semiarid and dry-transition landscapes are more prone to suffer abrupt functional changes than sub-humid ones. We used (a) remote-sensing estimations of precipitation-use-efficiency (PUE) from enhanced vegetation index (EVI) observations performed in 231 x 231 m plots of the Moderate Resolution Imaging Spectroradiometer (MODIS); (b) soil parameter (enzyme activity, organic matter) and (c) vegetation parameter (functional groups) determinations from soil sampling and vegetation surveys, respectively, performed in the same plots. We analyzed and compared the shape of the functional change (in terms of PUE, soil and vegetation parameters) in response to human disturbance intensity for our holm oak sites in the three climatic areas. Although no threshold of abrupt change is observed, important differences in the functional response of holm oak woodlands to disturbance exist between climatic conditions. Overall, semiarid and dry-transition woodlands suffer a non-linear functional decrease in terms of PUE, soil organic matter and enzyme activity with disturbance intensity. Differently, sub-humid woodlands experience a linear decrease of PUE with disturbance intensity and an increase of both soil parameters at high disturbance intensities after an important decrease at low disturbance intensities. The structural change from woody- to herbaceous-dominated landscapes in sub-humid areas explains the recovery of the functional state of the system at high disturbance intensities. This structural change in the vegetation provides resilience to sub-humid woodlands at high intensity levels where semiarid and dry-transition woodlands suffer a pronounced degradation.

Trabajo presentado en el 4th International Conference on Biohydrology. Walking on drylands , celebrado en Almería (España), del 13 al 16 de septiembre (2016), The effects of land degradation are pervasive worldwide, particularly under the present context of global changes in climate and land uses, which are affecting biodiversity and landscape functioning at an unprecedented rate. How ecosystems undergo environmental change is recognized as one of the main frontiers in ecology and environmental sciences. Land degradation may take place in either a smooth gradual way or a more abrupt manner. Theoretical studies and empirical evidences increasingly suggest that drylands are particularly prone to develop abrupt changes in their structure and functions in response to climate variations and human disturbance. Precipitation-use efficiency (PUE) represents the ratio of vegetation production to annual precipitation, and provides an excellent evaluation tool for the assessment of human and climate impacts on landscape functionality. Holm oak (Quercus ilex) forests are one of the most conspicuous dry woodlands in the Iberian Peninsula and the Mediterranean basin, and show a variety of conservation status, due to their very long history of human use. We study the response of holm oak woodlands to human disturbance along an aridity gradient (i.e. semiarid, dry-transition and sub-humid landscapes; annual precipitation to potential evapotranspiration aridity ratio 0.40-0.50, 0.50-0.65, and >0.65, respectively) across a 20,000 km2 region in eastern Spain, using remote-sensing estimations of PUE from enhanced vegetation index (EVI) observations of the Moderate Resolution Imaging Spectroradiometer (MODIS). PUE decreases from semiarid to sub-humid climate conditions in the studied holm oak landscapes, suggesting that as aridity and water stress decrease, other factors (e.g. nutrient and light availability) may control vegetation production. Overall, our results indicate that aridity largely impacts the response of PUE to human disturbance, assessed as a function of the integrity of vegetation conditions. PUE decreases linearly with the degradation of tree cover in subhumid holm oak woodlands. Differently, semiarid and dry-transition landscapes show little change in PUE by increasing disturbance intensity until a threshold is passed in vegetation conditions (30%-50% cover), where PUE decreases abruptly. The impact of disturbance on PUE is larger for dry years than for wet years, and increases with climate aridity from sub-humid to dry-transition and semiarid woodlands. Therefore, aridity may also interact with land degradation in Mediterranean holm oak woodlands by intensifying the loss of the ecosystem ability to buffer large changes in vegetation production caused by climate variability.

Trabajo presentado en el congreso 2nd Conference Of Cost Action: Connecting European Connectivity Research, celebrado en Valencia, España, del 12 al 17 de enero de 2015

Ponencia presentada en el XI Congreso Nacional de la Asociación Española de Ecología Terrestre celebrado en Pamplona del 6 al 10 de mayo de 2013, La erosión del suelo se considera habitualmente sólo como un problema ambiental. En la presente comunicación pretendemos mostrar que debería considerarse también un factor de selección natural y ensamblaje de comunidades. Para ello analizamos la relación entre la erosión y la mixospermia - la capacidad de semillas y frutos de algunas especies de secretar sustancias mucilaginosas en contacto con el agua y que las fija al suelo. A partir de experimentos con propágulos de 140 especies de plantas de ambientes secos y semiáridos, hemos determinado que la tasa de remoción por erosión depende principalmente del tamaño del propágulo. Pero también encontramos que ma mixospermia disminuye notablemente la probabilidad de arrastre de los propágulos por de las clases de tamaño menores. En comunidades vegetales del matorral en ambientes semiáridos encontramos que el aumento de la erosión pero no el de la aridez incrementan la proporción de especies con diásporas mixospérmicas. En especies leñosas de esas mismas comunidades vegetales encontramos una importante variabilidad fenotípica en la expresión de la mixospermia. Dicha variabilidad se relaciona positivamente con su capacidad de evitar la remoción por distintos mecanismos a través de los cuales actúa la erosión. En las especies en las que dicha relación existe, encontramos además que la variabilidad fenotípica en la expresión de la mixospermia se correlaciona positivamente con la intensidad de la erosión que experimentan las poblaciones. Las evidencias obtenidas apoyan que la erosión del suelo debería considerarse un factor de ensamblaje de comunidades vegetales y de selección natural en ambientes semiáridos.

Ponencia presentada en la European Geosciences Union General Assembly celebrada en Viena del 7 al 12 de abril de 2013, Semiarid Mediterranean ecosystems are experiencing major alterations as a result of the complex interactions between climatic fluctuations and disturbances caused by human activities. Future scenarios of global change forecast a rapid degradation of these ecosystems, with a reduction of their functionality, as a result of changes in relevant vegetation and soil properties. Some theoretical models indicate that these ecosystems respond non-linearly to regular variations in the external conditions, with an abrupt shift when conditions approach a certain critical level or threshold. Considering these predictions, there is an urgent need to know the effects that these alterations might have on semi-arid ecosystems and their components. In this study, we aim at analyzing the consequences of climate change and increasing soil erosion on soil and vegetation properties and the functional dynamics of semiarid Mediterranean shrublands. We predict that the combined effect of both drivers will be additive or synergistic, increasing the negative effects of each one. We compared vegetation and soil properties of flat areas (low erosion) and steep hillslopes (high erosion) in two climatic areas (484 mm and 10.3ºC, and 368mm and 11.9ºC, respectively) that reproduce the predicted climate change in temperature and precipitation for the next 40 years. Species richness, vegetal cover, plant life-form composition were determined in 20 m2 plots and soil was sampled in the same plots to determine bulk density, aggregate stability, fertility and water holding capacity. All soil and vegetation properties were negatively affected by soil erosion and climate change. However, contrary to our hypothesis, the joined effect of both drivers on all soil and vegetation properties was antagonistic, except for the vegetal cover that showed an additive response to their interaction. Our results evidence that soil erosion affects more negatively the soil and vegetation properties in the cooler and wetter climatic area than in the warmer and drier one, and support moreover the idea that a functional threshold has been crossed between the two climatic areas.

Ponencia presentada en el 4th International Society for Seed Science Meeting on Seeds and the Envoronment celebrado en Shenyang (China) del 22 al 26 junio de 2013, Introduction: Soil particle detachment and transport along hillslopes caused by raindrops and runoff are the main mechanisms of soil erosion by rainfall in semiarid regions. Seeds resting on the soil surface after seed dispersal are at a risk of being removed downslope by erosion and deposited in the lower parts of hillslopes where seed burial or competition with pre-established vegetation may reduce plant fitness of plant species with low competitive abilities. Diaspores of many plant species inhabiting open vegetation in semiarid environments secrete mucilage after wetting (myxospermy), gluing them to the ground and preventing further movement when the mucilage dries. Although several different ecological roles have been proposed for myxospermy, in the present paper we tested whether mucilage secretion may be considered a response to soil erosion in plant species inhabiting semiarid environments. Methods: We related the amount of mucilage secretion by seeds of Helianthemum violaceum and Fumana ericifolia (Cistaceae) with the number of raindrop impacts needed to remove these seeds after gluing them with their own mucilage to the ground and the time that these seeds resist water runoff without detaching,. We also compared the amount of seed mucilage production by plants growing in habitats with contrasted erosion. Results and Conclusions: Our results show an important phenotypic variation in the amount of mucilage secretion in both species but suggest that the effect of mucilage secretion in the rate of seed removal by erosion is species and mechanism dependent. In F. ericifolia, the amount of mucilage secreted by the seeds is directly proportional to their resistance to raindrop impacts and is positively related, although weakly, to the intensity of erosion processes that plants experience. Nevertheless, all the seeds resist the force of runoff during 60 minutes irrespective of the amount of mucilage they produce. However, in H. violaceum mucilage secretion per se, but not the amount of mucilage produced by the seeds has an effect on the rate of seed removal by erosion processes and relates weak but inversely to the intensity of these processes that plants experience.

Poster presentado en la 3rd International Conference on Soil Bio- en Eco-Engineering celebrada en Vancouver (Canada) del 23 al 27 de julio de 2012, Recent studies have evidenced the major role of plant roots in the control of gully development in a large range of environments. However, few attention has been paid to the effectiveness of plant roots in controlling concentrated flow erosion in Mediterranean ecosystems, where gully erosion represents an important sediment source. Since scrublands are the most common plant communities in Mediterranean eroded areas, in our study, we aim at (1) comparing the erosion-reducing potential of roots of two common Mediterranean shrubs (Genista scorpius and Thymus vulgaris), paying special attention to their morphology (tap- vs. branched-rooted, respectively) and (2) determining, for each species, the root parameters that better control concentrated flow erosion. Laboratory experiments simulating concentrated flow were conducted with a flume. After sowing both species at different densities, samples with different root densities were achieved and submitted to concentrated flow. Root density, root length density, root surface area density and root area ratio were assessed. Relative soil detachment rates were calculated. The results indicate that both root systems reduce efficiently concentrated flow in a non linear exponential relationship. Contrary to our expectations, the root system of Genista seedlings showed a larger erosion-reducing potential than the one of Thymus. Results are discussed in accordance to the plant root parameters and the specific experimental conditions.

Poster presentado en la European Geosciences Union General Assembly celebrada en Viena del 3 al 8 de abril de 2011, Soil erosion is one of the most severe processes of land degradation in the Mediterranean region, especially in badland areas. Badlands are usually defined as “intensely dissected natural landscapes where vegetation is sparse or absent and which are useless for agriculture”. Although badlands occupy a relatively small fraction of the Mediterranean area, their erosion rates are significant. Several studies dealt with the influence of vegetation on erosion. This study, however, contributes to the recently growing interest in the reverse impact of erosion on vegetation development. Most research on badland dynamics was mainly conducted in the more abundant semi-arid badland environments. Here, water availability constitutes the main limiting factor for vegetation development. As a consequence, south-facing slopes are less vegetated due to a very large water stress. However, these findings do not necessary apply to sub-humid badland environments. Therefore the main objectives of this study are (i) to assess spatial patterns of vegetation cover and composition in a sub-humid badland environment in the Central Spanish Pyrenees, (ii) to determine topographic thresholds for plant colonization, and (iii) to contrast these findings to those obtained in semi-arid badlands. 179 representative plots (2mx2m) all having different aspect and gradient on sub-humid badland slopes in the Inner Depression (Central Spanish Pyrenees) were selected. For each plot, vegetation cover and number of plant species were determined. These data allow an evaluation of the relationship between slope gradient and vegetation cover as well as vegetation composition, for each slope aspect. The results show that vegetation cover decreases when slopes become steeper and no vegetation is observed above a critical slope gradient. The highest vegetation cover and the largest critical slope gradient are observed for south-facing slopes, contrasting to the results from semi-arid badlands. As slope steepness increases, vegetation development is hampered because of the struggle for equilibrium between gravitational and cohesion forces. However, this inhibitive effect of slope gradient on plant colonization capacity appears to vary with slope orientation. Which underlying processes can explain this orientation-influenced discrepancy? In contrast to semi-arid environments, water availability is not a limiting factor for vegetation growth since sub-humid badlands receive over 800 mm of annual precipitation. A more plausible explanation is the frequent occurrence of freezing and thawing processes on north-facing slopes and the related high intensity of geomorphic processes. A deeper understanding of the processes that limit vegetation establishment in sub-humid badlands might guide future initiatives aimed at reducing sediment yield in these environments.

En el presente trabajo, proponemos profundizar en el conocimiento sobre los procesos que limitan la colonización vegetal de laderas erosionadas en ambientes semiáridos, y más específicamente sobre la penetración de raíces en suelos compactados. Para ello, hemos desarrollado una metodología para el estudio de la capacidad de las raíces para penetrar sustratos y detectar grietas en un rango amplio de compactaciones. Hemos analizado además el efecto de la morfología de las raíces, del nivel de resistencia a la penetración y del espesor del nivel más superficial del sustrato en la penetración de las raíces y en la detección de grietas por las raíces. Esta metodología se basa en el uso de discos de cera cuyo nivel de resistencia a la penetración depende de las proporciones de mezcla de parafina y vaselina en condiciones controladas de laboratorio. Para el estudio se utilizó un diseño factorial cruzado 2 x 2 x 5, con dos especies de distinta morfología radicular (pivotante vs. fasciculada), dos espesores de sustrato (3 y 7 mm) y cinco niveles de resistencia a la penetración comprendidos entre 60 y 1500 kPa. Los resultados indican que el nivel de resistencia a la penetración y el espesor del sustrato influyen sobre la tasa (número de raíces por semilla que penetran el sustrato) y velocidad (número de días para que se produzca la primera penetración) de penetración de las raíces para las dos morfologías de raíces estudiadas. Al contrario, no se aprecia ningún efecto del tipo de raíz en la velocidad para penetrar el sustrato. Por otro lado, se ha puesto de manifiesto el papel importante del nivel de resistencia a la penetración y de la morfología de las raíces en la detección de grietas superficiales por las raíces. A partir de los resultados obtenidos, se discuten las distintas estrategias posibles que podrían explicar el éxito de las especies colonizadoras de taludes de carreteras. Asimismo, una estrategia mixta, que contempla la penetración del suelo o la detección de grietas superficiales por las raíces, podría tener éxito en los terraplenes, mientras que en los desmontes con valores limitantes de resistencia a la penetración por las raíces en las capas superficiales del sustrato geológico, la capacidad de las raíces para detectar grietas con un microambiente más favorable podría ser una estrategia de éxito para las plantas., Este trabajo ha sido realizado con la financiación del Ministerio de Ciencia y Tecnología (Proyecto REN 2001-2313 y Programa Ramón y Cajal co-financiado por el Fondo Social Europeo).

Poster presentado en la European Geosciences Union General Assembly celebrada en Viena del 19 al 24 de abril de 2009, In severely eroded areas, plant colonisation on steep slopes is limited by the action of strong erosive forces that interact with plants at early stages of plant establishment. The objective of this study was to understand the mechanism that controls spontaneous plant colonisation on highly eroded slopes in a semiarid badland area of East Spain by (i) determining topographic thresholds for plant colonisation, (ii) identifying the soil properties limiting to plant establishment and (iii) assessing whether colonising species have specific plant traits to cope with those limitations. We used slope angle and aspect as surrogates of erosion rate and water availability respectively. Since soil erosion and water availability can limit plant establishment and both interact in the landscape, we analysed variations in colonisation success with slope angle, as a function of slope aspect. Vegetation success was measured in terms of total vegetation cover and number of species in 156 different slopes. After determining slope angle thresholds, soil was sampled near the threshold values for soil analysis (nitrogen, phosphorous and CaCO3 contents and water holding capacity). Plant traits related to plant colonising capacity were analysed both in the pool of species colonising the steep slopes just below the threshold values and in the pool of species inhabiting the gentler slopes and absent from the steeper slopes just below the threshold. The identified slope angle threshold values for plant colonisation clearly decreased from North to South. No differences existed in soil properties neither among slope aspects at the slope angle threshold values nor between slope positions (just below and above the threshold) within slope aspect classes. This suggests that variations in the slope angle threshold between slope aspect classes result from differences in the colonising capacity of plants controlled by water availability. Long-distance dispersal, mucilage production and specific leaf area proved to be preferably associated with the pool of colonising species. These results may be useful in the perspective a more efficient ecological restoration of severely eroded semiarid ecosystems.

Ponencia presentada en el IX Congreso Nacional de la Asociación Española de Ecología Terrestre celebrado en Jaén del 18 al 22 de octubre de 2009

Ponencia presentada en la European Geosciences Union General Assembly celebrada en Viena del 13 al 18 de abril de 2008, Scientific awareness about roadslope ecosystems adjacent to roads, motorways, railways,. . . is gaining in importance. These emergent ecosystems are socio-economically relevant as they influence roadslope stability and soil erosion risk in the surroundings of communication routes. Roadslope restoration usually aims at regenerating as fast as possible a dense vegetal cover. However, in Mediterranean areas with unpredictable long droughts and short intense rain events, the traditional techniques used in Northern-Europe are usually unsuccessful. In this study, we present the most conclusive results in terms of roadslope protection against erosion of several studies carried out on semiarid roadslopes of East Spain since 2000. We aim at improving our understanding about the factors and processes that control soil erosion and plant colonisation on semiarid roadslopes, by determining the influence of the slope type, angle and aspect, and of the use of topsoil on soil erosion and vegetal cover. We also aim at developing a method of native species selection based on the plant ability to germinate under water-stress conditions, to penetrate compacted soils and to resist runoff, that could minimise erosion risks and improve the efficiency of future restoration plans.

Ponencia presentada en el 11th European Ecological Congress celebrado en Leipzig (Alemania) del 15 al 19 septiembre de 2008, We analyzed the consequences of climate change and the increase in soil erosion, as well as their interaction on plant and soil properties in semi-arid Mediterranean shrublands in Eastern Spain. Current models on drivers of biodiversity change predict an additive or synergistic interaction between drivers that will increase the negative effects of each one. We used a climatic gradient that reproduces the predicted climate changes in temperature and precipitation for the next 40 years of the wettest and coldest end of the gradient and also we compared flat areas with 20º steep hillslopes. We found that plant species richness and plant cover are nega tively affected by climate change and soil erosion which in tu rn negatively affects soil resistance to erosion, nutrient content and water holding capacity. We also found that plant species diversity correlates weakly w ith plant cover but strongly wi th soil properties related to fertility, water holding capacity and resist ance to erosion. Conversely these soil properties correlate weaker w ith plant species cover. The joint effect of climate change and soil erosion on plant species richness and soil characteristics is antagonistic. That is, the absolute magnitude of change is smaller than the sum of both effects. However, ther e is not interaction between climate change and soil erosion on plant cover and their effect s fit the additive model. The differences in the interaction model between plant cover and species richness supports the view that several soil properties are more linked to the effect that pa rticular plant species have on soil processes than to the quantity and qual ity of the plant cover and biomass they support.

7 páginas, 2 figuras, 2 tablas., We tested the hypothesis that seed availability is a limiting factor for plant colonization of road embankments under Mediterranean climate conditions. Experimental sowing on 10 road embankments was carried out to compare the colonization success of plants that Successfully colonize the road embankment and species that appear only occasionally in the road embankments. After sowing, we measured plant establishment, biomass production, and reproductive capacity of the species. The species that appear only occasionally in the road embankments had lower emergence rates (1.1 +/- 0.3%) than species that were successful colonizers (18.8 +/- 2.9%). None of the species of the former group survived or reproduced. The results did not support the hypothesis that seed availability was the main factor limiting plant colonization in the road embankments. We concluded that the arrival of seeds to road embankments under Mediterranean climate conditions was not enough to ensure colonization success of plants. Other factors, like hydric stress, appeared to affect seedling establishment and plant growth. Reclamation measures such as species selection should be taken in account to ensure revegetation success of road embankments., We thank the Spanish "Plan Nacional I+D+I del Mnisterio de Ciencia y Tecnología" (project REN2001-2313), "Consejo Superior de Investigaciones Científicas" and "Fundación Bancaja" for their funding. We also thank José Antonio Bellido for his assistance in sowing, plot weeding and seed collecting; Maite Pardo for her assistance in sowing; the staff of the laboratories of the CIDE for soil analyses; Miguel Verdú and David Conesa for their help with statistical analyses; and two anonymous referees for their considerable help in improving the manuscript.