Interacting water, nutrients, and shrub age control steppe grass-on-shrub competition: Implications for restoration

Understanding the factors that control grass–shrub interactions and coexistence is critical to the design of dryland management and restoration strategies. Using Stipa tenacissima tussocks as adult neighbor and Olea europaea var. sylvestris as target woody species, we performed a 5-year-long, large-scale manipulative experiment to investigate the independent and combined effects of water and nutrient availability, and the modulating effects of O. europaea ontogeny on the net outcome of grass–shrub interaction. At two contrasting dryland sites, we conducted experimental plantings of Olea seedlings on two microsites: contiguous to a Stipa tussock (Stipa microsite) and on the intertussock bare-soil areas (Open microsite), and manipulated resource availability by combining nutrient and water addition. The experiment followed a full factorial design, with all treatment combinations applied at each site. We monitored survival, height, and stem basal diameter of Olea individuals over a study period of 5 years. All across the wide range of conditions considered, negative effects of Stipa on Olea largely prevailed during the first 2 years after the plantation. We found that competition was stronger in the drier steppe, where extra inputs of water favored neutral interactions. Conversely, nutrient addition increased competition strength, particularly when combined with water inputs, pointing to the contrasting role of different resources and the importance of interactions between them in the control of plant–plant interaction outcome. The competition effects of Stipa faded with time and gradually shifted to neutral interaction as Olea individuals aged. Our results are particularly relevant to guide restoration efforts in formerly wooded xeric grasslands and rangelands.This research received financial support from the projects ESTRES (063/SGTB/2007/7.1), funded by the Spanish Ministry of Environment, and DRYEX (CGL2014-59074-R) and DRYEX2 (CGL2017-89804-R), funded by the Spanish Ministry of Science and Innovation, MICINN. Luna Morcillo is supported by the Spanish MICINN (PTA2019-018094). CEAM Foundation is funded by Generalitat Valenciana

Drone-based assessment of microsite-scale hydrological processes promoted by restoration actions in early post-mining ecological restoration stages

A successful choice of post-mining restoration activities in dry climates may depend on relevant features related to topographic characteristics, hydrological processes and vegetation development, which will determine functional recovery in these ecosystems. The combination of different restoration techniques to reestablish vegetation, such as sowing and plantation, implies the interspersion of bare-soil areas with vegetated areas in early plant development stages, which may result in an associated mosaic of hydrologic functioning. In this study, we conducted a drone-based assessment to disentangle the role played by microsite-scale hydrological processes (i.e., planting hole slope, sink volume capacity, individual catchment area, Flow Length Index) promoted by restoration actions in soil protection and vegetation development on the hillside scale. Based on two contrasting restoration scenarios (Steep hillside and Smooth hillside), the different applied restoration treatments conditioned the microtopographic processes on the planting hole scale and, therefore, resource redistribution. The main results showed higher planting hole functionality on the smooth hillsides than on steep hillside, which resulted in greater water availability and bigger vegetation patches. By addressing the role of hydrological processes on the microsite scale, our study contributes substantially to prior knowledge on the relevant factors for ecosystem development and post-mining restoration success. It also demonstrates that high-resolution drone images can be a very useful tool for monitoring restoration actions, especially in large, inaccessible and unstable restored areas.The study was funded by the LIFE TECMINE Project (LIFE16 ENV/ES/000159) from the European Programme for the Environment and Climate Action (2014–2020)*. L.M. was supported by the Spanish MICINN (PTA2019-018094). The CEAM foundation is funded by the Generalitat Valenciana

Sensitivity of quinoa cv. ‘Titicaca’ to low salinity conditions

Quinoa (Chenopodium quinoa Will.) is an annual herbaceous Andean plant. In recent years there is a growing interest on it due to its high quality as food, its wide adaptation to agroecological conditions and resistance to different abiotic stresses. In this work, we evaluate the growth pattern of quinoa plants cv. ‘Titicaca’, subjected to different levels of salinity, focusing on leaf production and nutrient content. In this sense, the results have shown that a high concentration of salinity negatively affects the growth of quinoa plants. In fact, plants grown with 200 mM NaCl reduced the photosynthetic rate and levels of chlorophylls and carotenoids in comparison with the rest of the treatments. Likewise, it has been proven how the progressive increase in salinity has negative effects on transpiration, stomatal conductance and photosynthetic rate, with significant subsequent reductions in shoot biomass, leaf area and nutrient adquisition, but without a decline in leaf dry weight (DW) production. However, the treatment of 200 mM NaCl demonstrated the best results regarding the water-use efficiency, as well as the number of saline glands. According to our results, the quinoa plant cv. ‘Titicaca’ seems to be tolerant to moderate concentrations of salinity (50–100 mM NaCl). This study could serve as a reference on this little known and cultivated species in the Mediterranean region, since it could become an alternative crop in areas with moderate salinity problems.Luna Morcillo was supported by the Spanish MICINN (PTA2019-018094). CEAM Foundation was funded by the Generalitat Valenciana

Innovative Techniques for Landscape Recovery after Clay Mining under Mediterranean Conditions

Open-pit mining results in profound modifications at different environmental scales that may persist for very long time periods, or even indefinitely. Considerable research efforts in mine reclamation strategies have been made, although reclamation failures are still common. In dry climates, such as in the Mediterranean Basin, successful actions may depend on features related to proper species selection and restoration techniques, which may substantially contribute to provide substrate stability and facilitate the regeneration of the main ecological processes. In this context, we developed the TECMINE case-study aimed to evaluate the feasibility and suitability of innovative restoration practices applied to clay-mine reclamation under Mediterranean conditions. The restoration strategy was designed at the landscape level with two main approaches: the recovery of natural geomorphology shapes and ecological restoration, including vegetation recovery and soil quality, based on proper reference ecosystems. After the geomorphological land remodeling, a combination of several innovative restoration techniques was implemented to reclaim plant communities and ecosystem functioning. These techniques involved: (i) accurate species selection according to microhabitat characteristics; (ii) high-quality plant production; (iii) surface remodeling to improve substrate stabilization; and (iv) implementing rainfall collection to enhance resources availability, soil fertility improvement and the amelioration of abiotic conditions for seedlings. Finally, we developed a monitoring program to assess the success of the implemented restoration techniques over time. The application of these innovative techniques has reported interesting results and represents a step forward in the improvement of mine restoration under Mediterranean climate.The study was funded by the LIFE TECMINE Project (LIFE16 ENV/ES/000159) from the European Programme for the Environment and Climate Action (2014–2020)*. L.M. was supported by the Spanish MICINN (PTA2019-018094). The CEAM foundation is funded by the Generalitat Valenciana

Forest Decline Triggered by Phloem Parasitism-Related Biotic Factors in Aleppo Pine (Pinus halepensis)

Climate models predict increasing mean temperatures and reduced precipitation for Mediterranean ecosystems already subjected to major hydrological fluctuations. Forest decline phenomena relate extreme droughts or heat waves with other organisms, e.g., insects or microorganisms acting as pests, but their role needs to be elucidated. A biotic factor responsible for forest diseases is Candidatus Phytoplasma pini which is a phloem-parasitism that negatively affects Spanish pine forests in drought-prone areas. In several healthy and declining Aleppo pine stands, we monitored pine infection by PCR (Polimerase Chain Reation), determined the tree phloem tissue terpene composition, carbohydrate content, measured several relevant morpho-physiological variables and examined trees affected by bark beetles. PCR confirmed C. P. pini infection was widespread in all stands, regardless of to the presence of symptomatically affected trees. However, visible symptomatic decline only occurred in trees living under more stressful conditions. The terpene composition of pines in declining stands differed from those in healthy ones, and could be related with bark beetle attacks when pines were previously weakened by the phytoplasma disease. Our results indicate that biotic factors, such as C. P. pini, affecting phloem tissue may be triggering factors for drought-mediated forest decline and suggest that phloem diseases can play a key role in forest declining processes during extreme drought.This research was funded by Sección de Defensa Fitosanitaria (Conservación del Medio Natural, Consejeria de Medio Ambiente, Comunidad de Madrid) and the Survive-2 project (CGL2015-69773-C2-2-P MINECO/FEDER) from the Spanish Government. The CEAM Foundation is supported by Generalitat Valenciana

Functional similarity and competitive symmetry control productivity in mixtures of Mediterranean perennial grasses

Competition is a major factor structuring plant communities and controlling their productivity. The functional similarity between the interacting species and the context resource availability are assumed to be most critical factors that modulate the strength, sign, and outcome of plant competition, yet their roles and interactions are subjected to debate. In a glasshouse experiment, we constructed monocultures and bi-specific cultures of three common perennial grasses of Mediterranean drylands, the short grass Brachypodium retusum and the tussock grasses Stipa tenacissima and Lygeum spartum, and investigated how the functional similarity between these species modulate their interactions and culture productivity under contrasting levels of water availability. Regardless the degree of functional similarity between the interacting species, B. retusum consistently exhibited a greater competitive ability than the other two species, followed by L. spartum, and with S. tenacissima behaving as the weakest competitor. Bi-specific cultures of B. retusum and either L. spartum or S. tenacissima produced higher biomass than the average biomass of the respective monocultures (i.e. overyielding), whereas the combination of the most similar species, L. spartum—S. tenacissima, which exhibited the highest competition symmetry (i.e., the more similar mutual impact), did not show any significant overyielding. Higher water availability increased productivity and promoted transgressive overyielding for the most dissimilar species, B. retusum and L. spartum, which however exhibited intermediate competition asymmetry. This study calls attention to the thin line between differences in functional traits and competition asymmetry that could eventually lead to either competitive exclusion or resource partitioning and coexistence.This study was financially supported by the Spanish Ministry of Science, Innovation and Universities (http://www.ciencia.gob.es/) through the projects DRYEX (CGL2014-59074-R) and DRYEX2 (CGL2017-89804-R). The CEAM foundation is supported by Generalitat Valenciana

Distinctive Traits for Drought and Salt Stress Tolerance in Melon (Cucumis melo L.)

Melon (Cucumis melo L.) is a crop with important agronomic interest worldwide. Because of the increase of drought and salinity in many cultivation areas as a result of anthropogenic global warming, the obtention of varieties tolerant to these conditions is a major objective for agronomical improvement. The identification of the limiting factors for stress tolerance could help to define the objectives and the traits which could be improved by classical breeding or other techniques. With this objective, we have characterized, at the physiological and biochemical levels, two different cultivars (sensitive or tolerant) of two different melon varieties (Galia and Piel de Sapo) under controlled drought or salt stress. We have performed physiological measurements, a complete amino acid profile and we have determined the sodium, potassium and hormone concentrations. This has allowed us to determine that the distinctive general trait for salt tolerance in melon are the levels of phenylalanine, histidine, proline and the Na+/K+ ratio, while the distinctive traits for drought tolerance are the hydric potential, isoleucine, glycine, phenylalanine, tryptophan, serine, and asparagine. These could be useful markers for breeding strategies or to predict which varieties are likely perform better under drought or salt stress. Our study has also allowed us to identify which metabolites and physiological traits are differentially regulated upon salt and drought stress between different varieties.SC was a recipient of grant FPU19/01977 from the Spanish Ministerio de Universidades. LM and AV activities were funded by the Prometeu program (IMAGINA project, PROMETEU/2019/110). LM was also supported by the Spanish MICINN (PTA2019-018094). The CEAM foundation was funded by the Generalitat Valenciana

Plant-plant interactions: biotic and abiotic control factors, impacts on productivity, and applications to conservation and restauration

Los trabajos recogidos en la presente memoria de tesis doctoral abordan las interacciones planta-planta a través de una ruta de aprendizaje y conocimiento que busca contribuir a la demanda de nuevos enfoques en los estudios sobre interacciones y diversidad. Específicamente, partiendo del estado del arte reciente sobre el tema y de forma incremental, se aborda el papel de las combinaciones de varios factores y especies en el control del resultado de las interacciones planta-planta, sus efectos en el ensamblaje de comunidades, la biodiversidad y función del ecosistema, así como en sus aplicaciones en el manejo y conservación de ecosistemas vulnerables. La investigación doctoral se estructura en los siguientes estudios científicos: - El efecto combinado de la disponibilidad de nutrientes y agua, la edad y el estrés individual como moduladores de las interacciones arbusto-herbácea en estepas semiáridas. Se basa en un experimento manipulativo a largo plazo realizado en zonas semiáridas de Alicante. El objetivo específico de este estudio es investigar el efecto de varias combinaciones de disponibilidad de agua y nutrientes en el balance neto de la interacción entre plantones de Olea europaea var. sylvestris y macollas de Stipa tenacissima L., así como el efecto modulador de la edad y la variación en el estrés individual de los plantones en el resultado de dicha interacción. - El efecto relativo de la proximidad filogenética y funcional en las interacciones entre especies herbáceas semiáridas. Es un estudio bajo condiciones controladas en invernadero (en los módulos invernaderos de la Universidad de Alicante), consistente en un ensayo de cultivos mono y bi-específicos de tres especies de gramíneas comunes en ecosistemas semiáridos (Lygeum spartum L., Brachypodium retusum L. y Stipa tenacissima L.), bajo condiciones contrastadas de disponibilidad hídrica. El objetivo principal del ensayo es la comparación de la intensidad de la interacción entre individuos de la misma especie e individuos de dos especies diferentes en función de sus diferencias funcionales y su distancia filogenética y el impacto de esta interacción en la productividad de los cultivos. - La diversidad genética como modificador de las relaciones diversidad-productividad y como facilitadora de especies raras. A través de experimentos manipulativos en invernadero, usando comunidades vegetales con diferentes niveles de diversidad genotípica de cebada (Hordeum vulgare) y de diversidad específica de “malas hierbas”, se evalúan los efectos independientes y combinados de ambos tipos de diversidad y el papel relativo en las relaciones diversidad-productividad del efecto de muestreo y el efecto de complementariedad, así como el potencial de la diversidad de cultivos para influir en el éxito de “malas hierbas”

The Role of Population and Half-Sib Family on Driving Suitable Functional Traits for Quercus suber L. Forest Restoration

Research Highlights: Seedlings of different Quercus suber L. populations and half-sib families differ in their response to multiple stressors, which may have consequences on the future distribution of this Mediterranean species. Background and Objectives: Global change will likely increase the frequency and severity of drought in drylands. Plant species’ distributions will largely depend on their ability to respond to the combined effect of drought and other environmental stressors. Genetic diversity in morpho-functional traits are key components of this response. Yet, information on the response to multiple stresses is scarce for many iconic species. The present study assessed the variability in the response of populations and half-sib families of a Mediterranean acidophilous tree, cork oak, to drought and changes in soil conditions. Materials and Methods: We sampled acorns of half-sib families from two cork oak populations genetically introgressed with the alkaline-tolerant species Quercus ilex L., and from a non-introgressed cork oak population located in its core habitat. We germinated the acorns and subjected seedlings to contrasted levels of water availability and additions of calcium and magnesium carbonate, and assessed their morpho-physiological response. Results: Response to drought and soil chemistry composition differed between populations and families. For some traits, introgressed populations responded similarly to drought than the non-introgressed population. Conversely, the response to soil chemistry was not clearly related to introgression. When considering half-sib families within populations, the population effect diminished, which revealed the importance of intra-population variation. However, relevant traits for water scarcity adaptations, such as specific leaf area and root:shoot ratio, remained significantly different at the population level, which highlights the relevance of these traits for management. Conclusions: Our study shows that the adaptive management and restoration of cork oak forests should consider not only geographic provenances, but also half-sib lines within populations.This research has been supported by the European CREOAK Project (QLRT-2001-01594) and the IMAGINA-PROMETEO Project (PROMETEU/2019/110) funded by the Generalitat Valenciana. JC acknowledges the support from Ministerio de Ciencia, Innovación y Universidades, project Cost-effectiveness analysis of restoration actions (COSTERA; RTI2018-095954-B-I00). The CEAM Foundation is supported by the Generalitat Valenciana

Moderate pine cover maximizes 10-year survival and growth in late-successional species of contrasting functional strategies

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