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AimsPlants can influence the level of herbivory experienced by neighboring plants. The importance of such belowground associational effects are poorly understood. In this study we examine whether Jacobaea vulgaris provides associational resistance against nematodes to neighboring plants.MethodsThirteen species (6 forbs, 3 grasses and 4 legumes) were each grown in mixtures with J. vulgaris and in monocultures. A nematode community was introduced to half of the pots. After 12 weeks, plant dry mass was assessed for each individual plant in each pot, and the number of nematodes in the soil and roots were identified. We then examined for each plant species its performance in mixtures and in monocultures, in presence and absence of nematodes and analyzed the abundance and composition of nematodes.ResultsForbs produced more, grasses similar, and legumes less biomass in mixtures with J. vulgaris than in monocultures. Nematode addition did not influence biomass. There were fewer root-feeding nematodes in the soil in mixtures than in monocultures, but this was only true for plants that were good hosts for nematodes. The community composition of soil nematodes was different in monocultures and mixtures. Densities of migratory endoparasitic nematodes in the roots of neighboring plants were lower in mixtures than in monocultures. Moreover, the presence of nematodes changed the outcome of plant-plant interactions, often in favor of J. vulgaris.ConclusionsJacobaea vulgaris provides belowground associational resistance to other plants against migratory endoparasitic nematodes, and the presence of nematodes can change the outcome of plant-plant interactions.

Background and aims – Understanding the spatial patterns and associations of tree species with their conspecific and heterospecific neighbours is critical for sustainable management of their stands. This study assessed the intra- and interspecific spatial structure of six life stages in Afzelia africana, a keystone multipurpose and endangered tree species in a tropical savanna of Benin.Material and methods – Three plots of 4 ha each were demarcated on three sites along a conservation gradient (hunting zone – core conservation zone). Individuals of A. africana (irrespective of their diameter at breast height) and heterospecific trees (dbh ≥ 5 cm) were mapped. Tree spatial patterns and associations were determined using univariate and bivariate pair correlation functions. The distance to the nearest neighbour was further used to assess tree-to-tree distance.Key results – We found variable spatial patterns across sites. In the core zone where wildlife density is high, most life stages had a random distribution. In contrast, in the hunting zone where wildlife density is low, the species spatial distribution changed from a predominantly aggregative pattern during early stages to a less aggregative or random spatial pattern for very large adults. Most pairs of life stages showed neutral associations, except for small and large adults, which had positive association between themselves on two sites. We also found that A. africana tree spatial distribution was unrelated to heterospecific trees.Conclusion – We suggest that bush fire, seed dispersion, predation, and local environment would have contributed to the observed patterns.

Mixed-species forests are promoted as a forest management strategy for climate change mitigation and adaptation because they are more productive and can be more resistant and resilient than monospecific forests under drought stress. However, the trait-based mechanisms driving these properties remain elusive, making it difficult to predict which functional identities of species best improve tree growth and decrease tree physiological water stress under drought.We investigated tree growth and physiological stress responses (i.e. increase in wood carbon isotopic ratio; δ13C) to changes in climate-induced water availability (wet-to-dry years) along gradients in neighbourhood tree species richness and drought-tolerance traits. Using tree cores from a large-scale biodiversity experiment, we tested the overarching hypothesis that neighbourhood species richness increases growth and decreases δ13C. We further hypothesized that the abiotic (i.e. climatic conditions) and the biotic context modulate these biodiversity-ecosystem functioning relationships. We characterized the biotic context using drought-tolerance traits of focal trees and their neighbours. These traits are related to cavitation resistance vs. resource acquisition and stomatal control.We found that tree growth increased with neighbourhood species richness. However, we did not observe a universal relief of water stress in species-rich neighbourhoods, nor an increase in the strength of the relationship between richness and growth and between richness and δ13C from wet-to-dry years. Instead, these relationships depended on both the traits of the focal trees and their neighbours. At either end of each drought-tolerance gradient, species responded in opposing directions during drought and non-drought years.Synthesis. We report that the biotic context can determine the strength and nature of biodiversity-ecosystem functioning relationships in experimental tree communities. We derive two key conclusions: (1) drought-tolerance traits of focal trees and their neighbours can explain divergent tree responses to drought and diversity, and (2) contrasting, trait-driven responses of tree species to wetvsdry climatic conditions can promote forest community stability. Mixing tree species with a range of drought-tolerance traits may therefore increase forest productivity and stability.

The analysis of the spatial phylogenetic and phenotypic structure of plant communities can provide insight into the underlying processes and interactions governing their assembly, and how these may change during plant ontogeny. We used point pattern analysis to find out if saplings and adult plants are surrounded by phylogenetically and phenotypically more similar or more dissimilar neighbours than expected by chance, and whether these associations change from the sapling to the adult stage. To this end, we combined information on the phylogenetic structure and eight phenotypic traits of 15 woody plant species in two Mediterranean mixed forests of southeastern Spain. At the community level, we found that the sapling bank at both sites did not show phylogenetic or phenotypic spatial patterns, but adults showed phylogenetic clustering (i.e. heterospecific neighbours were more similar than expected). At the species level, we found frequently repulsive patterns in the sapling bank of less abundant species (i.e. heterospecific sapling or adult neighbours were more dissimilar than expected) in both, phylogenetic and phenotypic analyses. For the adult stage, we found phylogenetic attraction (i.e. more similar neighbours) in just one species and phenotypic clustering in four species. The processes driving the assembly of the communities of saplings and adults leave detectable signals in the spatial phylogenetic and phenotypic structure of our two forest communities. Our findings reinforce the existence of ontogenetic shifts in the mechanisms involved in plant community assembly. Facilitation between phylogenetically distant and phenotypically divergent species favours the recruitment of less abundant species. However, processes acting later in the ontogeny ameliorate the competition between close relatives and determine the spatial structure of adult plants. Nevertheless, the role of phenotype in shaping the interactions between adult plants was context- and trait-dependent. The use of spatial point pattern analysis allowed a nuanced interpretation of the phylogenetic and phenotypic structures of plant communities., The study was conducted under the projects REPNETS (PGC2018-100966-B-100) and COEXMED II (CGL2015-69118-C2-1-P), funded by MCIN/ AEI/10.13039/501100011033, and FEDER funds ‘Una manera de hacer Europa’. AJP was supported by a FPI grant from the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU/BES2016-463077688) associated to COEXMED II project.

Plant recruitment interactions (i.e., what recruits under what) shape the composition, diversity, and structure of plant communities. Despite the huge body of knowledge on the mechanisms underlying recruitment interactions among species, we still know little about the structure of the recruitment networks emerging in ecological communities. Modeling and analyzing the community-level structure of plant recruitment interactions as a complex network can provide relevant information on ecological and evolutionary processes acting both at the species and ecosystem levels. We report a data set containing 143 plant recruitment networks in 23 countries across five continents, including temperate and tropical ecosystems. Each network identifies the species under which another species recruits. All networks report the number of recruits (i.e., individuals) per species. The data set includes >850,000 recruiting individuals involved in 118,411 paired interactions among 3318 vascular plant species across the globe. The cover of canopy species and open ground is also provided. Three sampling protocols were used: (1) The Recruitment Network (RN) protocol (106 networks) focuses on interactions among established plants (“canopy species”) and plants in their early stages of recruitment (“recruit species”). A series of plots was delimited within a locality, and all the individuals recruiting and their canopy species were identified; (2) The paired Canopy-Open (pCO) protocol (26 networks) consists in locating a potential canopy plant and identifying recruiting individuals under the canopy and in a nearby open space of the same area; (3) The Georeferenced plot (GP) protocol (11 networks) consists in using information from georeferenced individual plants in large plots to infer canopy-recruit interactions. Some networks incorporate data for both herbs and woody species, whereas others focus exclusively on woody species. The location of each study site, geographical coordinates, country, locality, responsible author, sampling dates, sampling method, and life habits of both canopy and recruit species are provided. This database will allow researchers to test ecological, biogeographical, and evolutionary hypotheses related to plant recruitment interactions. There are no copyright restrictions on the data set; please cite this data paper when using these data in publications., Fondo Europeo de Desarrollo Regional, Grant/Award Number, ICTS-2017-08-CSIC-4; SUMHAL, Grant/Award Numbers: 418RT0555, 501100011033, LIFEWATCH-2019-09-CSIC-13, MCIN/ AEI/10.13039, PGC2018-100966-B-100, PID2020-113157GB-I00, POPE 2014-2020

Translocation of metabolites between different plant species provides important hints in understanding the fate of bioactive root exudates. In the present study, targeted and untargeted mass spectrometry-based metabolomics was applied to elucidate the transfer of bioactive compounds between rye and several crops and weed species. Our results demonstrated that benzoxazinoids (BXs) synthesized by rye were taken up by roots of neighbouring plant species and translocated into their shoots. Furthermore, we showed that roots of rye plants took up compounds originating from neighbouring plants. Among the compounds taken up by rye roots, wogonin was detected in the rye shoot, which indicated a root-to-shoot translocation of this compound. Elucidating the transfer of bioactive compounds between plants is essential for understanding plant–plant interactions, developing natural pesticides and understanding their modes of action.

International audience; The intensification of biological processes coping with salt stress became a major issue to mitigate land degradation. The Sine-Saloum Delta in Senegal is characterized by salt-affected soils with vegetation dominated by salt-tolerant grass Sporobolus robustus and shrubs like Prosopis juliflora. Plant experiments in controlled conditions suggested that arbuscular mycorrhizal (AM) fungi might be the key actors of facilitation process observed between S. robustus and P. juliflora, but the AM fungal community determinants are largely unknown. The current field-based study aimed at (1) characterizing the environmental drivers (rhizosphere physico-chemical properties, plant type and season) of the AM fungal community along an environmental gradient and (2) identifying the AM fungal taxa that might explain the S. robustus-mediated benefits to P. juliflora. Glomeraceae predominated in the two plants, but a higher richness was observed for S. robustus. The pH and salinity were the main drivers of AM fungal community associated with the two plants, negatively impacting richness and diversity. However, while a negative impact was also observed on mycorrhizal colonization for S. robustus, P. juliflora showed opposite colonization patterns. Furthermore, no change was observed in terms of AM fungal community dissimilarity between the two plants along the environmental gradient as would be expected according to the stress-gradient and complementary hypotheses when a facilitation process occurs. However, changes in intraspecific diversity of shared AM fungal community between the two plants were observed, highlighting 23 AM fungal OTUs associated with both plants and the highest salinity levels. Consequently, the increase of their abundance and frequency along the environmental gradient might suggest their potential role in the facilitation process that can take place between the two plants. Their use in ecological engineering could also represent promising avenues for improving vegetation restoration in saline Senegalese's lands.

Despite their low contribution to forest carbon stocks, lianas (woody vines) play an important role in the carbon dynamics of tropical forests. As structural parasites, they hinder tree survival, growth and fecundity; hence, they negatively impact net ecosystem productivity and long‐term carbon sequestration.Competition (for water and light) drives various forest processes and depends on the local abundance of resources over time. However, evaluating the relative role of resource availability on the interactions between lianas and trees from empirical observations is particularly challenging. Previous approaches have used labour‐intensive and ecosystem‐scale manipulation experiments, which are infeasible in most situations.We propose to circumvent this challenge by evaluating the uncertainty of water and light capture processes of a process‐based vegetation model (ED2) including the liana growth form. We further developed the liana plant functional type in ED2 to mechanistically simulate water uptake and transport from roots to leaves, and start the model from prescribed initial conditions. We then used the PEcAn bioinformatics platform to constrain liana parameters and run uncertainty analyses.Baseline runs successfully reproduced ecosystem gas exchange fluxes (gross primary productivity and latent heat) and forest structural features (leaf area index, aboveground biomass) in two sites (Barro Colorado Island, Panama and Paracou, French Guiana) characterized by different rainfall regimes and levels of liana abundance.Model uncertainty analyses revealed that water limitation was the factor driving the competition between trees and lianas at the drier site (BCI), and during the relatively short dry season of the wetter site (Paracou). In young patches, light competition dominated in Paracou but alternated with water competition between the wet and the dry season on BCI according to the model simulations.The modelling workflow also identified key liana traits (photosynthetic quantum efficiency, stomatal regulation parameters, allometric relationships) and processes (water use, respiration, climbing) driving the model uncertainty. They should be considered as priorities for future data acquisition and model development to improve predictions of the carbon dynamics of liana‐infested forests. Synthesis. Competition for water plays a larger role in the interaction between lianas and trees than previously hypothesized, as demonstrated by simulations from a process‐based vegetation model., Competition for water plays a larger role in the interaction between lianas and trees than previously hypothesized, as demonstrated by simulations from a process‐based vegetation model.

When foraging and competing for below-ground resources, plants have to coordinate the behaviour of thousands of root tips in a manner similar to that of eusocial animal colonies. While well described in animals, we know little about the spatial behaviour of plants, particularly at the level of individual roots. Here, we employed statistical methods previously used to describe animal ranging behaviour to examine root system overlap and the efficiency of root positioning in eight grassland species grown in monocultures and mixtures along a gradient of neighbour densities. Species varied widely in their ability to distribute roots efficiently, with the majority of species showing significant root aggregation at very fine spatial scales. Extensive root system overlap was observed in species mixtures, indicating a lack of territoriality at the level of whole root systems. However, with increasing density of competitors, several species withdrew roots from the periphery of foraging ranges and increased intraplant root aggregation in the remaining area, which may indicate consolidation of foraging areas under competitive pressure. Several species exhibited responses consistent with resource contest in species mixtures where encounters with competitors’ roots triggered increased root aggregation at the expense of foraging efficiency. Such responses only occurred in mixtures of species with comparable competitive abilities but were absent in asymmetric species combinations. Synthesis. Combining fine-scale measurement of plant root distributions with spatial statistics yields new insights into plant behavioural strategies with significant potential to impact resource foraging efficiency and productivity.

At the early stage of primary succession, there are deficient nutrient resources as well as competition stress among neighboring plants. Our aims were to elucidate the flexibility of tree seedlings' stoichiometric relationships and their effects on soil microbial communities, and to determine the driving forces of species turnover during primary succession through the evaluation of carbon (C) : nitrogen (N) : phosphorus (P) stoichiometric relationships. We conducted an experiment testing N addition effect on two species from the early stage of primary succession, under intra- and interspecific competition conditions. Our results showed that higher values of delta N-15-NO(3)(-)and delta C-13 were observed inPopulus purdomiiindividuals than inSalix rehderianaafter N application, which indicated a more efficient N uptake and water-use efficiency inP. purdomiiplants. Furthermore, under N addition, the intraspecific competition ofP. purdomiipresented a higher urease activity, microbial biomass C (MBC), microbial N:P ratio (MBN:MBP), and phylogenetic diversity compared to the intraspecific competition ofS. rehderiana. The results showed thatP. purdomiiseedlings influenced soil properties in a way that led to a positive feedback on their performance with an increasing N availability. In contrast,S. rehderianaseedlings influenced soil properties in a way that caused a negative feedback on their performance with increasing N. Such events can promote species turnover fromSalixtoPopulusduring succession. Additionally, DNA sequencing of soil bacterial communities showed differences in the composition of microbial communities in response to N fertilization and different competition patterns. Altogether, our results showed that plant, soil, and microbial community responses to N fertilization in a subalpine glacier forefield differed among tree species and competition patterns. This study brings new insight into mechanisms that drive species replacement and biogeochemical cycling during primary succession.

Recognition of plant pathogens or herbivores activate a broad-spectrum plant defense priming in distal leaves against potential future attacks, leading to systemic acquired resistance (SAR). Additionally, attacked plants can release aerial or below-ground signals that trigger defense responses, such as SAR, in neighboring plants lacking initial exposure to pathogen or pest elicitors. However, the molecular mechanisms involved in interplant defense signal generation in sender plants and decoding in neighboring plants are not fully understood. We previously reported that Pieris brassicae eggs induce intraplant SAR against the foliar pathogen Pseudomonas syringae in Arabidopsis thaliana. Here we extend this effect to neighboring plants by discovering an egg-induced interplant SAR via mobile root-derived signal(s). The generation of an egg-induced interplant SAR signal requires pipecolic acid (Pip) pathway genes ALD1 and FMO1 but occurs independently of salicylic acid (SA) accumulation in sender plants. Furthermore, reception of the signal leads to accumulation of SA in the recipient plants. In response to insect eggs, plants may induce interplant SAR to prepare for potential pathogen invasion following feeding-induced wounding or to keep neighboring plants healthy for hatching larvae. Our results highlight a previously uncharacterized below-ground plant-to-plant signaling mechanism and reveals genetic components required for its generation.

Long‐term grassland biodiversity experiments have shown that diversity effects on productivity tend to strengthen through time, as complementarity among coexisting species increases. But it remains less clear whether this pattern also holds for other ecosystems such as forests, and if so why.Here we explore whether diversity effects on tree growth change predictably during stand development in Finland's boreal forests. Using tree ring records from mature forests, we tested whether diameter growth trajectories of dominant tree species growing in mixture differed from those in monoculture. We then compared these results with data from the world's longest running tree diversity experiment, where the same combinations of species sampled in mature forests were planted in 1999.We found that diversity effects on tree growth strengthened progressively through time, only becoming significantly positive around 20 years after seedling establishment. This shift coincided with the period in which canopy closure occurs in these forests, at which time trees begin to interact and compete above‐ground. These temporal trends were remarkably consistent across different tree species sampled in mature forests, and broadly matched growth responses observed in the much younger experimental plots.Synthesis. Our results mirror those from grassland ecosystems and suggest that canopy closure is a key phase for promoting niche complementarity in diverse tree communities. They also provide a series of testable hypotheses for the growing number of tree diversity experiments that have been established in recent years.

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.

Intercropping is both a well-established and yet novel agricultural practice, depending on one’s perspective. Such perspectives are principally governed by geographic location and whether monocultural practices predominate. Given the negative environmental effects of monoculture agriculture (loss of biodiversity, reliance on non-renewable inputs, soil degradation, etc.), there has been a renewed interest in cropping systems that can reduce the impact of modern agriculture while maintaining (or even increasing) yields. Intercropping is one of the most promising practices in this regard, yet faces a multitude of challenges if it is to compete with and ultimately replace the prevailing monocultural norm. These challenges include the necessity for more complex agricultural designs in space and time, bespoke machinery, and adapted crop cultivars. Plant breeding for monocultures has focused on maximizing yield in single-species stands, leading to highly productive yet specialized genotypes. However, indications suggest that these genotypes are not the best adapted to intercropping systems. Re-designing breeding programs to accommodate inter-specific interactions and compatibilities, with potentially multiple different intercropping partners, is certainly challenging, but recent technological advances offer novel solutions. We identify a number of such technology-driven directions, either ideotype-driven (i.e., “trait-based” breeding) or quantitative genetics-driven (i.e., “product-based” breeding). For ideotype breeding, plant growth modeling can help predict plant traits that affect both inter- and intraspecific interactions and their influence on crop performance. Quantitative breeding approaches, on the other hand, estimate breeding values of component crops without necessarily understanding the underlying mechanisms. We argue that a combined approach, for example, integrating plant growth modeling with genomic-assisted selection and indirect genetic effects, may offer the best chance to bridge the gap between current monoculture breeding programs and the more integrated and diverse breeding programs of the future.

While antagonistic interactions between plants have been a major topic of eco-evolutionary research, little evidence exists on the evolution of positive plant interactions (i.e., plant facilitation). Here, we first summarize the existing empirical evidence on the role of facilitation as a selection pressure on plants. Then, we develop a theoretical eco-evolutionary framework based on fitness-trait functions and interaction effectiveness that provides predictions for how facilitation-related traits may evolve. As evolution may act at levels beyond the individual (such as groups or species), we discuss the subject of the units of evolutionary selection through facilitation. Finally, we use the proposed formal evolutionary framework for facilitation to identify areas of future research based on the knowledge gaps detected., This work was supported by CYTED (Red 418RT0555) and the Swiss National Science Foundation (PP00P3_170645). This is a contribution to the Research Unit Modeling Nature, funded by the Consejería de Economía, Conocimiento, Empresas y Universidad, and European Regional Development Fund (ERDF), reference SOMM17/6109/UGR.

Climate warming can induce the encroachment of shrubs and may trigger treeline dynamics. However, the responses of shrubs and trees to climate change may be modulated by other environmental drivers such as land-use change and biological interactions. The European Alps are one of the three areas experiencing the most intense warming globally in the twentieth century. We analyse, through a multidisciplinary approach, the shrub and tree encroachment at the Stelvio Pass (Italian Alps) focusing on three target species (Rhododendron ferrugineum, Larix decidua, Pinus mugo) to reconstruct their dynamics and assess which drivers (climate change, land-use change, biological interactions provided by shrub facilitation) promoted their ingression. Shrub colonization started in 1867, in coincidence with the end of the Little Ice Age. Tree recruitment started since 1960 for P. mugo and 1972 for L. decidua and correlated strongly with air warming and shortening of the snow cover duration. Climate (air temperature, snow cover) exhibited the highest correlation with shrub and tree dynamics both during the period of recruitment and in the following and preceding 5-year period. Air warming appeared to be crucial for tree ingression and persistence. Land-use change was not related to shrub encroachment, and only weakly to tree recruitment. Both the correlation analysis as well as the patterns of recruitment highlighted that shrubs were characterized by different ecological requirements from trees. There was not a “nurse effect” of shrubs on trees, and this biotic interaction changed with the developmental stage of the involved species, being lowest for seedlings and highest for adults, requiring further investigations. Future scenarios of climate change indicate a further and intense warming, and our data show that it is likely that shrub and tree encroachment will proceed, with relevant consequences on the extremely vulnerable high-elevation alpine ecosystems.

Understanding the relationships among species is central to ecological research; however, many knowledge gaps remain regarding how desert plant species interact. In the present study, we assessed the effect of rainfall on the belowground interactions and root morphology of two desert shrubs, Reaumuria soongorica (Tamaricaceae) and Salsola passerina (Chenopodiaceae), from three communities with similar landforms and soil environments. The roots of both R. soongorica and S. passerina were deeper when grown together than grown singly. Interestingly, the belowground biomass of R. soongorica was higher, but the belowground biomass of S. passerina was lower when grown together than when grown alone. This suggests that S. passerina benefitted from the association with R. soongorica. When grown together under conditions of low rainfall, the roots of R. soongorica were deeper than those of S. passerina, which suggests that R. soongorica is more robust than S. passerina when subjected to periods of decreased rainfall. We concluded that the symbiotic relationship between these two shrub species can lead to deeper roots and that the plants are affected by rainfall availability. Combined with the output results of climate change models, we speculated that the distribution area of these two species will expand to the west, which has important implications on how the interactions of other desert species may change in response to climate variability., The interspecific relationship of desert plants also has a significant impact on their morphological characteristics. Here, we found a novel interaction between two desert shrubs and proved that the effect will change with the environmental gradient.

Allelopathic potential of Thymus pulegioides L. chemical polymorphism was investigated under natural and laboratory conditions. A field analysis of 127 natural habitats hosting chemotypes of T. pulegioides with different ratios of phenolics, geraniol, and ɑ-terpinyl acetate was conducted. Effects of chemotypes, and their main compounds on seed germination and radicle growth of Trifolium pratense L. and Poa pratensis L. were conducted under laboratory conditions. Field analysis showed that Poa species were more plentiful in comparison with Trifolium species, independent of the chemotypical composition of T. pulegioides habitats. Laboratory tests with plant-acceptors showed a stronger inhibitory effect of essential oils on the germination and radicle growth of P. pratensis but in some instances germination was stimulated. Dissimilar effects were observed for the same allelochemical through air and water on the same plant-acceptor. Significantly, different effects of essential oils on radicle growth occurred in T. pratense and P. pratensis: with sensitivity to the phenolic chemotype via air and the ɑ-terpinyl acetate chemotype through water. This demonstrates that chemical polymorphism can expand communication opportunities of T. pulegioides with associated plant species. Combining investigations in natural habitats with laboratory experiments can help understand the effect of chemical polymorphism on plant-plant ecological interactions.

Volatile organic compounds (VOCs) emitted by plant roots can influence the germination and growth of neighbouring plants. However, little is known about the effects of root VOCs on plant–herbivore interactions of neighbouring plants. The spotted knapweed (Centaurea stoebe) constitutively releases high amounts of sesquiterpenes into the rhizosphere. Here, we examine the impact of C. stoebe root VOCs on the primary and secondary metabolites of sympatric Taraxacum officinale plants and the resulting plant‐mediated effects on a generalist root herbivore, the white grub Melolontha melolontha. We show that exposure of T. officinale to C.stoebe root VOCs does not affect the accumulation of defensive secondary metabolites but modulates carbohydrate and total protein levels in T. officinale roots. Furthermore, VOC exposure increases M. melolontha growth on T. officinale plants. Exposure of T. officinale to a major C. stoebe root VOC, the sesquiterpene (E)‐β‐caryophyllene, partially mimics the effect of the full root VOC blend on M. melolontha growth. Thus, releasing root VOCs can modify plant–herbivore interactions of neighbouring plants. The release of VOCs to increase the susceptibility of other plants may be a form of plant offense., Root volatiles released by Centaurea stoebe modulate root growth and primary metabolism of Taraxacum officinale. These changes are associated with increased root herbivore growth on T. officinale, thus demonstrating that root volatiles can modify plant‐herbivore interactions in neighboring plants

The findings that some plants alter their competitive phenotype in response to genetic relatedness of its conspecific neighbour (and presumed competitor) has spurred an increasing interest in plant kin-interactions. This phenotypic response suggests the ability to assess the genetic relatedness of conspecific competitors, proposing kin selection as a process that can influence plant competitive interactions. Kin selection can favour restrained competitive growth towards kin, if the fitness loss from reducing own growth is compensated by increased fitness in the related neighbour. This may lead to positive frequency dependency among related conspecifics with important ecological consequences for species assemblage and coexistence. However, kin selection in plants is still controversial. First, many studies documenting a plastic response to neighbour relatedness do not estimate fitness consequences of the individual that responds, and when estimated, fitness of individuals grown in competition with kin did not necessarily exceed that of individuals grown in non-kin groups. Although higher fitness in kin groups could be consistent with kin selection, this could also arise from mechanisms like asymmetric competition in the non-kin groups. Here we outline the main challenges for studying kin selection in plants taking genetic variation for competitive ability into account. We emphasize the need to measure inclusive fitness in order to assess whether kin selection occurs, and show under which circumstances kin selected responses can be expected. We also illustrate why direct fitness estimates of a focal plant, and group fitness estimates are not suitable for documenting kin selection. Importantly, natural selection occurs at the individual level and it is the inclusive fitness of an individual plant – not the mean fitness of the group – that can capture if a differential response to neighbour relatedness is favoured by kin selection.

Tree crown morphology is a key driver of forest dynamics, determining not only the competitiveness of an individual but also the competitive effect exerted on neighbouring trees. Multiple ecological theories, including metabolic scaling theory (MST), predict crown morphology from first principles, but typically lack consideration of competition. The accurate quantification of crown morphology to test theoretical predictions, and the canopy interactions that could alter them, has historically been limited by the simplicity and associated error of traditional crown measurements. In this study, we calculate high‐resolution two‐ and three‐dimensional crown metrics from Terrestrial Laser Scanning data for 1,441 Pinus sylvestris, P. nigra, Quercus faginea and Q. ilex trees from a water‐limited forest community in central Spain and test height‐crown metric scaling relationships. We demonstrate new TLS methods to define symmetric and asymmetric neighbourhood metrics based on tree height, crown size and neighbour projected crown area, and test the importance of neighbourhood genus diversity on crown morphology by separating competition from congeneric and heterogeneric neighbours. Competition negatively impacted all crown metrics except crown depth where only P. nigra showed sensitivity. Asymmetric competition was the strongest driver of pine crown morphology, but oaks were more sensitive to symmetric competition, in line with shade tolerance expectations. Congeneric competition reduced Q. faginea crown size and changed its shape, but we found no significant effects of heterogeneric neighbours. Most species and crown dimensions had height‐crown scaling exponents below those predicted by MST, which may be due to water limitation effects. Pines and oaks showed large differences in crown depth to height scaling, with the former shallower and the latter deeper, in contrast to theoretical predictions. Synthesis. Our study is the first to demonstrate the ability of TLS to characterise crown morphology from leaf‐wood separated clouds and competitive neighbour effects in a water‐limited forest community, and to use TLS metrics to test ecological crown scaling theory. Most crown metrics scaled below theoretical predictions. Pines were more sensitive to competition by larger neighbours and oaks to crowding from all neighbours, with competition from neighbours of the same genus having a consistent negative effect.

Ants benefit myrmecophytic plants by two main activities defending them from herbivores and offering nutrients. Ants’ territorial defence behaviour also benefits their myrmecophytic plants; in the case of trees, this behaviour includes eliminating structural parasites (epiphytes and lianas). These benefits could also occur with myrmecophytic epiphytes by decreasing the abundance of competing epiphytes. In two subunits of a tropical dry forest in the centre of Mexico, we (i) recorded the diversity of ants associated with the myrmecophyte Tillandsia caput-medusae, and experimentally tested: (ii) the effect of the ants associated with the myrmecophyte in the removal of its seeds and the seeds of other sympatric non-myrmecophyte species of Tillandsia; and (iii) if seed remotion by ants corresponds with epiphyte load in the preferred (Bursera copallifera) and limiting phorophyte species (B. fagaroides, Ipomoea pauciflora and Sapium macrocarpum). In five trees per species, we tied seed batches of T. caput-medusae, T. hubertiana, T. schiedeana and T. recurvata. One seed batch was close, and the other far away from a T. caput-medusae with active ants. Between forest subunits, ant richness was similar, but diversity and evenness differed. Ants diminish seed establishment of all the Tillandsia species; this effect is stronger in the forest subunit with a large ant diversity, maybe because of ant competition. Seed remotion by ants is independent of phorophyte species identity. Although ants can provide benefits to T. caput-medusae, they also could be lowering their abundance., Ants provide several benefits to their myrmecophytic plants. In a tropical dry forest of Mexico, we experimentally found that ants associated with the myrmecophyte Tillandsia caput-medusae lower the density of seeds of all the Tillandsia species, including those of the myrmecophyte. This ant activity is harmful to the myrmecophyte and is more intense where ant diversity is higher, probably because competition between ants increases.

Questions: Woody shrub encroachment affects community structure and composition. However, most studies focus on their effects on understorey plant communities, and the relative importance of shrubs in affecting plants vs. soil biota communities is poorly known. Location: Inner Mongolian Steppe, China. Methods: We examined the effect of shrubs on multiple community attributes, including plants, soil biota (bacteria, fungi and nematodes), and soil fertility, and quantified how these effects changed from semi‐arid to hyper‐arid conditions (from 281 to 110 mm of mean annual precipitation). In addition, we assessed whether the effects of shrubs on plant communities were directly mediated by biotic filtering in seed germination and establishment, or indirectly mediated by plant biomass or soil fertility in the case of soil organisms. Results: The effect of shrubs on soil biota was generally more positive than on plants, and it increased with aridity. We found that a larger proportion of belowground taxa depended on shrub presence (36%) than plants (20%). Soil nematodes and soil bacteria were directly influenced by shrub presence whereas soil fungi were indirectly influenced by enhanced soil fertility. Shrubs also increased plant biomass under all conditions but only increased plant species richness in the most arid conditions. Despite the generally positive effect of shrubs, and the fact that they weakened the filtering effects of aridity on seed germination, aridity was a stronger predictor of changes in species composition than shrub presence was, particularly for plants. Conclusions: Our results illustrate the variety of positive effects of shrubs and show that they are particularly important in supporting biodiversity in the most arid conditions. These strong and positive effects could partially buffer the impacts of increasing aridity on dryland soil biodiversity, but our study suggests that facilitative interactions may not be able to completely mitigate the impacts of increasing aridity on drylands. This research was funded by National Natural Science Foundation of China [31901140, 31570453] and China Scholarship Council. SS was supported by the Spanish Government under a Ramón y Cajal contract (RYC-2016- 20604).

While antagonistic interactions between plants have been a major topic of eco-evolutionary research, little evidence exists on the evolution of positive plant interactions (i.e., plant facilitation). Here, we first summarize the existing empirical evidence on the role of facilitation as a selection pressure on plants. Then, we develop a theoretical eco-evolutionary framework based on fitness-trait functions and interaction effectiveness that provides predictions for how facilitation-related traits may evolve. As evolution may act at levels beyond the individual (such as groups or species), we discuss the subject of the units of evolutionary selection through facilitation. Finally, we use the proposed formal evolutionary framework for facilitation to identify areas of future research based on the knowledge gaps detected. This work was supported by CYTED (Red 418RT0555) and the Swiss National Science Foundation (PP00P3_170645). This is a contribution to the Research Unit Modeling Nature, funded by the Consejería de Economía, Conocimiento, Empresas y Universidad, and European Regional Development Fund (ERDF), reference SOMM17/6109/UGR.

A method to identify anticancer compounds in plants was proposed based on the hypothesis that these compounds are primarily present in plants to provide them with an ecological advantage over neighboring plants and other competitors. According to this view, identifying plants that contain compounds that inhibit or interfere with the development of other plant species may facilitate the discovery of novel anticancer agents. The method was developed and tested using Magnolia grandiflora, Gynoxys verrucosa, Picradeniopsis oppositifolia, and Hedyosmum racemosum, which are plant species known to possess compounds with cytotoxic activities. Plant extracts were screened for growth inhibitory activity, and then a thin-layer chromatography bioautography assay was conducted. This located the major antileukemic compounds 1, 2, 4, and 5 in the extracts. Once the active compounds were located, they were extracted and purified, and their structures were determined. The growth inhibitory activity of the purified compounds showed a significant correlation with their antileukemic activity. The proposed approach is rapid, inexpensive, and can easily be implemented in areas of the world with high biodiversity but with less access to advanced facilities and biological assays.

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.

Predictions of plant responses to global warming frequently ignore biotic interactions and intraspecific variation across geographical ranges. Benefactor species play an important role in plant communities by protecting other taxa from harsh environments, but the combined effects of warming and beneficiary species on their performance have been largely unexamined. We analyzed the joint effects of elevated temperature and neighbor removal on the benefactor plant Silene acaulis, in factorial experiments near its low- and high-latitude range limits in Europe. We recorded growth, probability of reproduction and fruit set during 3 years. The effects of enhanced temperature were positive near the northern limit and negative in the south for some performance measures. This pattern was stronger in the presence of neighbors, possibly due to differential thermal tolerances between S. acaulis and beneficiary species in each location. Neighbors generally had a negative or null impact on S. acaulis, in agreement with previous reviews of overall effects of plant–plant interactions on benefactors. However, small S. acaulis individuals in the north showed higher growth when surrounded by neighbors. Finally, the local habitat within each location influenced some effects of experimental treatments. Overall, we show that plant responses to rising temperatures may strongly depend on their position within the geographic range, and on species interactions. Our results also highlight the need to consider features of the interacting taxa, such as whether they are benefactor species, as well as local-scale environmental variation, to predict the joint effects of global warming and biotic interactions on species and communities., This project was funded by the Swedish Research Council to W. F. Morris (Ref: 2012-42619-94710-26) and by the Spanish Ministry of Economy, Industry and Competitiveness to M. B. García (CGL2017-90040-R).

Trait intraspecific variability determines community dynamics and species coexistence. In response to competition, plants can display intraspecific variability to enhance their competitive ability or stabilise their niche differences with competitors. This response is multidimensional because it involves changes along different functional axes and inevitable trade‐offs between traits. Here, we transposed the recent concept of the multidimensional trait space to the analysis of intraspecific plant response to competition. We specifically tested the following: (a) in the absence of competitors, the plant multidimensional trait space will be packed towards strategies promoting plant colonisation; and (b) with competitors, the plant multidimensional trait space will be directed towards competition with its size and shaping characteristics dependent on competitor species richness. We studied trait intraspecific variability of two clonal species, Brachypodium pinnatum (L.) P. Beauv. and Elytrigia repens (L.) Gould, in response to competition. We analysed plant response in the absence of competitors and in competition. Competition treatments included intraspecific and interspecific experimental mixtures with increasing species richness. For each target species and each treatment, we built an hypervolume based on six traits involved in the three‐dimensional competition (i.e., ramet and connection traits). We measured these hypervolumes for their size, similarity and the contribution of traits in their shaping. In the absence of competitors and for both species, we demonstrated a multidimensional trait space packing towards a colonisation strategy. Under competition, the multidimensional trait spaces of the two target species were the widest at the extremes of the richness gradient, that is, intraspecific and interspecific high richness competition treatments. High intraspecific variability either promoted niche differentiation from individuals of similar species or reflected the large range of competitive responses deployed when plants were faced with many different competitor identities. The multidimensional response process was based on fine adjustments of various traits depending on the surrounding neighbourhood composition and more specifically, on the competitor functional similarity with the target species. This study emphasises the multidimensionality of species competitive response, and also underlines the so far neglected importance of competitor species richness for trait intraspecific variability and subsequently community assembly. A plain language summary is available for this article.

Local tree species diversity is maintained in part by conspecific negative density dependence (CNDD). This pervasive mechanism occurs in a variety of forms and ecosystems, but research to date has been heavily skewed toward tree seedling survival in tropical forests. To evaluate CNDD more broadly, we investigated how sapling growth rates were affected by conspecific adult neighbors in a fully mapped 25.6 ha temperate deciduous forest. We examined growth rates as a function of the local adult tree neighborhood (via spatial autoregressive modeling) and compared the spatial positioning of faster‐growing and slower‐growing saplings with respect to adult conspecific and heterospecific trees (via bivariate point pattern analysis). In addition, to determine whether CNDD‐driven variation in growth rates leaves a corresponding spatial signal, we extended our point pattern analysis to a static, growth‐independent comparison of saplings and the next larger size class. We found that negative conspecific effects on sapling growth were most prevalent. Five of the nine species that were sufficiently abundant for analysis exhibited CNDD, while only one species showed evidence of a positive conspecific effect, and one or two species, depending on the analysis, displayed heterospecific effects. There was general agreement between the autoregressive models and the point pattern analyses based on sapling growth rates, but point pattern analyses based on single‐point‐in‐time size classes yielded results that differed markedly from the other two approaches. Our work adds to the growing body of evidence that CNDD is an important force in temperate forests, and demonstrates that this process extends to sapling growth rates. Further, our findings indicate that point pattern analyses based solely on size classes may fail to detect the process of interest (e.g., neighborhood‐driven variation in growth rates), in part due to the confounding of tree size and age.

Background and aims – Exploring the role of mammalian carnivores as seed dispersers in Mediterranean environments is crucial for understanding biotic interactions and preserving mutualistic networks in areas with high biodiversity. We examine the potential role of the Sardinian fox ( Vulpes vulpes subsp. ichnusae ) as a seed-disperser of two juniper species ( Juniperus phoenicea subsp. turbinata and J. oxycedrus subsp. macrocarpa ) in Mediterranean coastal environments.Methods – Observational and manipulative experiments were conducted in five coastal sites in north-western Sardinia (Italy) between 2010 and 2013.Key results – We found that Sardinian fox actively disperses seeds of J. phoenicea subsp. turbinata, whereas no evidence was obtained for the fox dispersing seeds of J. oxycedrus subsp. macrocarpa. Fox scat contained, on average, 73–86 J. phoenicea subsp. turbinata seeds, accounting 16.3–17.8 % of the average dung weight. The role of Sardinian fox as a primary disperser of J. phoenicea subsp. turbinata is by directly dispersing juniper seeds (via defecation) to a specific microhabitat (i.e. 80–90 % of dung was released on dwarf plants, mainly Helichrysum italicum subsp. microphyllum ), which positively affected the survival of emerged seedlings). We quantified that fox dispersed 30 to 100 seeds per day per hectare (3 500–10 500 seeds per hectare in one winter season).Conclusions – We reported that Sardinian fox is a direct disperser of J. phoenicea subsp. turbinata, thus playing a major role in secondary successional dynamics in Mediterranean coastal environments. Evolutionary implications are discussed, in that the positive interaction between Sardinian fox and J. phoenicea subsp. turbinata could be recent, following the introduction of fox to the Tyrrhenian islands during the 7 th –6 th millennium BC.

1. As global climate changes and the world population increases, agriculture faces an enormous challenge to increase food production in an equitable and sustainable manner. Principles and concepts derived directly from plant ecological research can help meet this challenge.2. This series of 10 mini-reviews considers some of the key ways that plant ecologists can help inform and contribute to meeting this challenge.3. The papers are grouped into three main themes of plant ecology, namely plant community diversity and structure, plant population dynamics and plant interactions, and plant-soil (belowground) interactions.4. Synthesis: We identify a number of important knowledge gaps in areas where plant ecological research can contribute towards improving yield, nutrition, ecosystem services, and environmental resilience of agricultural systems. However, the adoption of plant ecological principles in sustainable agriculture will require practical approaches to their implementation along with improved understanding of social and economic barriers.

International audience; 1. Plant neighbours can strongly influence the interactions between herbivores and focal plants, for instance by providing food of different quality (consumptive effects) or by changing the behaviour and metabolism of the herbivore and the focal plant without being consumed (non-consumptive effects). Determining the species-specific contributions of consumptive and non-consumptive effects is important to understand the ecophysiological mechanisms which underlie neighbourhood effects. 2. We quantified the impact of nine different grassland plant species on the interaction between Taraxacum officinale and the root-feeding insect Melolontha melolontha. We investigated the contribution of consumptive and non-consumptive effects to the observed patterns, and evaluated the impact of neighbouring plants on the growth and physiology of T.officinale upon M.melolontha attack. 3. Melolontha melolontha growth was strongly affected by the presence of different neighbouring species. The three grass species increased larval growth when growing with T.officinale, with Poa pratensis having a synergistic effect in the mixture compared to both monocultures. The forb Centaurea stoebe reduced larval growth when growing with T.officinale or alone. The other five species had no measurable impact on larval performance. Based on these results, P.pratensis and C.stoebe were selected for further experiments. 4. Diet-mixing experiments showed that P.pratensis increased M.melolontha growth when offered together with T.officinale, while C.stoebe suppressed it. When feeding was restricted to artificial diet, larval growth was not changed by the presence of P.pratensis or C.stoebe. However, when feeding was restricted to T.officinale, larval growth was increased by both heterospecific neighbours. Biomass and primary metabolism of T.officinale under attack by M.melolontha was also altered by the presence of C.stoebe and P.pratensis. Together, these results show that consumptive and non-consumptive effects can explain the positive effect of P.pratensis. In contrast, the negative effect of C.stoebe is likely driven exclusively by intoxication. 5. Synthesis. The performed experiments suggest that different combinations of consumptive and non-consumptive effects are likely to contribute to the diversity of neighbourhood effects in nature. Furthermore, they show that neighbourhood effects are important factors in below-ground plant-insect interactions.

Despite a large consensus on increasing facilitation among plants with increasing stress in alpine regions, a number of different outcomes of interaction have been observed, which impedes the generalisation of the 'stress-gradient hypothesis' (SGH). With the aim to reconcile the different viewpoints on the stress-interaction relationship in alpine environments we hypothesized that fine nurse variations within a single life form (cushion) may explain this pattern variability. To test this hypothesis, we compared the magnitude of the stress-interaction relationship in a single study area with that observed in existing studies involving cushions, worldwide. We characterized the nurse effects of cushions on the whole plant community at inter-specific, intra-specific and intra-individual levels along a stress gradient in the dry, alpine tropics of Bolivia (4400 m, 4700 m and 4900 m a.s.l). Using a relative index of interaction (RII) we included our data in a meta-analysis on the nurse effects of cushions along alpine gradients, worldwide. At inter-specific level, the loose cushion Pycnophyllum was a better nurse than the compact Azorella compacta. However, at intra-individual level facilitation was higher at the periphery than at the centre of cushions, exceeding in magnitude the variation observed at inter-specific level. This pattern was associated with higher minimum temperature and lower mortality at the periphery of cushions. The net effects of cushions on plant communities became more positive at higher elevation, corroborating the SGH. Within our single site in Bolivia, fine morphological nurse variations captured a similar variability in the stress-interaction relationship as that observed in a subset of studies on cushions on a worldwide scale. This suggests that fine variations in nurse traits, in general those not considered in protocols dealing with facilitation or in restoration/conservation management plans, explain in part the current discrepancies among SGH studies in alpine regions.

The functioning of plant communities is strongly influenced by the number of species in the community and their spatial arrangement. This is because plants interact with their nearest neighbors and this interaction is expected to be stronger when the interacting individuals are ecologically similar in terms of resource use. Recent evidence shows that species richness alters the balance of intra- versus interspecific competition, but the effect of species richness, and phylogenetic and functional diversity on the spatial pattern of the plant communities remain less studied. Even far, how forest stand structure derived from past management practices can influence the relationship between species richness and spatial pattern is still unknown. Here, we evaluate the spatial distribution of woody individuals (DBH >7.5 cm) in 209 forest stands (i.e. plots) with an increasing level of species richness (from 1 up to 10 species) in six forest types along a latitudinal gradient in Europe. We used completely mapped plots to investigate the spatial pattern in each forest stand with point pattern techniques. We fitted linear models to analyze the effect of species richness (positively correlated with phylogenetic diversity) and functional diversity on tree spatial arrangements. We also controled this relationship by forest type and stand structure as a proxy of the management legacy. Our results showed a generalized positive effect of species richness and functional diversity on the degree of spatial clustering of trees, and on the spatial independence of tree sizes regardless of the forest type. Moreover, current tree spatial arrangements were still conditioned by its history of management; however its effect was independent of the number of species in the community. Our study showed that species richness and functional diversity are relevant attributes of forests influencing the spatial pattern of plant communities, and consequently forest functioning., CCB is beneficiary of a FPU grant funded by the Spanish Government (AP2010-5600). This research was supported by the FunDivEUROPE project, receiving funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no.265171, the Spanish-funded project REMEDINAL TE-CM S2018/EMT-4338 and COMEDIAS FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación/_Proyecto CGL2017-83170-R. RB was funded by a Marie Skłodowska-Curie Intra-European fellowship (grant agreement no. 302445).

Plants usually interact with other plants, and the outcome of such interaction ranges from facilitation to competition depending on the identity of the plants, including their sexual expression. Arbuscular mycorrhizal (AM) fungi have been shown to modify competitive interactions in plants. However, few studies have evaluated how AM fungi influence plant intraspecific and interspecific interactions in dioecious species. The competitive abilities of female and male plants of Antennaria dioica were examined in a greenhouse experiment. Females and males were grown in the following competitive settings: (i) without competition, (ii) with intrasexual competition, (iii) with intersexual competition, and (iv) with interspecific competition by Hieracium pilosella – a plant with similar characteristics to A. dioica. Half of the pots were grown with Claroideoglomus claroideum, an AM fungus isolated from the same habitat as the plant material. We evaluated plant survival, growth, flowering phenology, and production of AM fungal structures. Plant survival was unaffected by competition or AM fungi. Competition and the presence of AM fungi reduced plant biomass. However, the sexes responded differently to the interaction between fungal and competition treatments. Both intra- and interspecific competition results were sex-specific, and in general, female performance was reduced by AM colonization. Plant competition or sex did not affect the intraradical structures, extraradical hyphae, or spore production of the AM fungus. These findings suggest that plant sexual differences affect fundamental processes such as competitive ability and symbiotic relationships with AM fungi.

Interactions between plants can be both positive and negative, denoting facilitation and competition. Although facilitative effects of having legume neighbours (focus on yield productivity) are well studied, a better mechanistic understanding of how legumes interact with non-legumes in terms of root distribution is needed. We tested the effects of neighbour identity, its spatial location, as well as the effects of plant order of arrival on above and belowground traits and root distribution. We performed a rhizotron experiment (4 weeks duration) in which we grew maize alone, with only a legume, only another grass, or with both species and tracked roots of the plant species using green and red fluorescent markers. Maize grew differently when it had a neighbour, with reduced development when growing with wheat compared to alone. Growing with a legume generally equated to the same outcome as not having a neighbour. Roots grew towards the legume species and away from the wheat. Order of arrival affected aboveground traits to a certain extent, but its effects on maize roots were dependent on spatial location. Our study provides evidence of facilitation, showing the importance of the identity of the neighbours, together with their spatial location, and how order of arrival can modulate the outcome of these initial interactions.

In facilitative interactions, facilitated plants gain a benefit from growing associated to a nurse plant, without damaging the nurse. The persistence of these positive interactions or their shift to competition might depend on whether the nurse shrub also gains some benefit from the association. We hypothesized that nurse shrubs can receive water stored in the parenchyma of their facilitated Neobuxbaumia tetetzo once the cactus becomes an adult. We injected deuterium-enriched water into the water storage tissues of N. tetetzo adults, and sampled the xylem water of the nurse Mimosa luisana plant in the shared vegetation patch before and after the injection of the tracer. We also sampled spatial-control individuals of M luisana outside the vegetation patch. We found a significant enrichment in deuterium concentration in the xylem water of the associated M. luisana but not in individuals outside the patch. This suggests that in semiarid environments, nurse plants can benefit from growing associated to succulent columnar cacti by gaining water transferred from their storage tissues during dry periods, potentially enhancing persistence of facilitative interactions., This work was supported by Ministerio de Economía y Competitividad [FPDI-2013-16266, IJCI-2015-23498]; British Ecological Society [Early Career Project Grant 3975-4849] and Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica, Dirección General de Asuntos del Personal Académico [IN-213414-3].

Ecological network studies are providing important advances about the organization, stability and dynamics of ecological systems. However, the ecological networks approach is being integrated very slowly in plant community ecology, even though the first studies on plant facilitation networks (FNs) were published more than a decade ago. The study of interaction networks between established plants and plants recruiting beneath them, which we call Recruitment Networks (RNs), can provide new insights on mechanisms driving plant community structure and dynamics. RNs basically describe which plants recruit under which others, so they can be seen as a generalisation of the classic FNs since they do not imply any particular effect (positive, negative or neutral) of the established plants on recruiting ones. RNs summarise information on the structure of sapling banks. More importantly, the information included in RNs can be incorporated into models of replacement dynamics to evaluate how different aspects of network structure, or different mechanisms of network assembly, may affect plant community stability and species coexistence. To allow an efficient development of the study of FNs and RNs, here we unify concepts, synthesise current knowledge, clarify some conceptual issues, and propose basic methodological guidelines to standardise sampling methods that could make future studies of these networks directly comparable., Red CYTED (P417RT0228), Project COEXMED II and PIROPHENO (CGL2015‐69118‐C2‐1‐P; CGL2017‐89751‐R; Spanish Ministerio de Economía y Competitividad and FEDER funds from the EU) funded this project.

The diversity of pathways through which mycorrhizal fungi alter plant coexistence hinders the understanding of their effects on plant‐plant interactions. The outcome of plant facilitative interactions can be indirectly affected by mycorrhizal symbiosis, ultimately shaping biodiversity patterns. We tested whether mycorrhizal symbiosis enhances plant facilitative interactions and whether its effect is consistent across different methodological approaches and biological scenarios. We conducted a meta‐analysis of 215 cases (involving 21 nurse and 29 facilitated species), in which the performance of a facilitated plant species is measured in the presence or absence of mycorrhizal fungi. We show that mycorrhizal fungi significantly enhance plant facilitative interactions mainly through an increment in plant biomass (aboveground) and nutrient content, although their effects differ across biological contexts. In semiarid environments mycorrhizal symbiosis enhances plant facilitation, while its effect is non‐significant in temperate ecosystems. In addition, arbuscular but not ecto‐mycorrhizal (EMF) fungi significantly enhance plant facilitation, particularly increasing the P content of the plants more than EMF. Some knowledge gaps regarding the importance of this phenomenon have been detected in this meta‐analysis. The effect of mycorrhizal symbiosis on plant facilitation has rarely been assessed in other ecosystems different from semiarid and temperate forests, and rarely considering other fungal benefits provided to plants besides nutrients. Finally, we are still far from understanding the effects of the whole fungal community on plant‐plant interactions, and on plant species coexistence., AMN was supported by a postdoctoral contract from the Spanish Ministry of Economy and Competitiveness (FPDI‐2013‐16266; IJCI‐2015‐23498) and an Early Career Project Grant from the BES (3975‐4849). Financial support was also provided by PAPIIT‐DGAPA‐UNAM (IN‐213414‐3), the Spanish Ministry of Economy and Competitiveness (CGL2014‐58333‐P), the regional government Generalitat Valenciana (PROMETEO/2016/021, GV/2016/187) and Ecometas excellence network (CGL2016‐81706‐REDT).

Plant provenance, plant facilitation and the characteristics of restoration sites are critical determinants of revegetation success. Surprisingly, however, very little is known about how these key factors interact, both with each other and to complex patterns of recruitment in target plant species. We investigated, for the first time, the potential of combining seed provenance, plant facilitation and restoration site characteristics to guide revegetation efforts. As a model system, we used the Iberian pear (Pyrus bourgaeana) and three potential nurse shrub species. To this end, we completed a comprehensive reciprocal transplant experiment in five P. bourgaeana populations within a fragmented landscape at the Doñana Biosphere Reserve (SW Spain). There were marked differences among provenances for seedling emergence and growth, as well as for recruitment, but no evidence of local adaptation was found. Shrubs generally had a positive or neutral effect on P. bourgaeana seedling performance with, for example survival underneath shrubs being, on average, twice as high as in open microhabitats. Interestingly, however, the magnitude and even the sign of such plant–plant interactions changed with both sowing locality and seed provenance. For instance, shrubs enhanced seedling survival and recruitment at the end of the study in four of the five sowing localities, whereas it decreased it in the remaining locality. Also, although nurse shrubs lessened seedling size of two provenances, it did not have a significant effect on the other three. Synthesis and applications. We show how revegetation success can be maximized, not only by selecting the most appropriate plant material, taking advantage of plant facilitative interactions and selecting the right restoration site, but also by using these factors in an integrated fashion. We propose local managers efficiently undertake future revegetation campaigns by mixing seeds from several genetically adequate source populations in numbers weighted according to previously estimated provenance-specific recruitment successes. Our novel approach can help to guide revegetation of many tree and plant species living in stressful conditions, such as arid, semi-arid and high mountain habitats., This research was financed by the Spanish Ministry of Education and Science (CGL2007‐63488/BOS). A.R.C., P.J.G. and J.M.F. were funded by Portuguese Foundation for Science and Technology (grants SFRH/BD/130527/2017, SFRH/BPD/115781/2016, IF/00728/2013 respectively).

1. The effects of plants on soil vary greatly between plant species and in mixed plant communities this can lead to spatial variation in plant-soil feedback (PSF) effects. Such spatial effects are thought to influence plant species coexistence, but the empirical evidence for this hypothesis is limited. 2. Here, we investigate how spatial heterogeneity in PSFs influences plant growth and competition. The experiment was carried out with high and low nutrient soils to examine how these effects depend on soil fertility. We collected soil from field plots planted for three years with monocultures of Anthoxanthum odoratum and Centaurea jacea and tested the performance of the two species in a greenhouse experiment in heterogeneous soils consisting of patches of “own” and “foreign” soils and in soils where the “own” and “foreign” soils were mixed homogeneously. In the test phase, plants were grown in monocultures and in 1:1 mixtures in live or sterilized soils. 3. Overall, A. odoratum in monocultures produced less aboveground biomass in heterogeneous soils than in homogeneous soils. Centaurea jacea produced less belowground biomass in live heterogeneous soils than in live homogeneous soils, but there was no difference between sterile heterogeneous and homogeneous soils. The belowground biomass per patch varied more in pots with live heterogeneous soils than in pots with live homogeneous soils for both plant species, but there was no difference between pots with sterile heterogeneous and homogeneous soils. In pots with plant mixtures, the difference in aboveground biomass between the two competing species tended to be smaller in heterogeneous than in homogeneous soils. In pots with heterogeneous soils, both plant species grown in mixtures produced more aboveground biomass in “foreign” soil patches than in “own” soil patches. The responses of plants to heterogeneous PSFs were not different between low and high nutrient soils. 4. Our results show that spatially heterogeneous PSFs can influence plant performance and competition via reducing the growth inequality between the two competing species by allowing selective growth in foreign soil patches, independent of initial soil nutrient availability. Such effect may slow down exclusion processes and thus promote the coexistence of competing species at the local scale in mixed plant communities.

Studies on positive plant–plant relations have traditionally focused on pair-wise interactions. Conversely, the interaction with other co-occurring species has scarcely been addressed, despite the fact that the entire community may affect plant performance. We used woody vegetation patches as models to evaluate community facilitation in semi-arid steppes. We characterized biotic and physical attributes of 53 woody patches (patch size, litter accumulation, canopy density, vegetation cover, species number and identity, and phylogenetic distance), and soil fertility (organic C and total N), and evaluated their relative importance for the performance of seedlings of Pistacia lentiscus, a keystone woody species in western Mediterranean steppes. Seedlings were planted underneath the patches, and on their northern and southern edges. Woody patches positively affected seedling survival but not seedling growth. Soil fertility was higher underneath the patches than elsewhere. Physical and biotic attributes of woody patches affected seedling survival, but these effects depended on microsite conditions. The composition of the community of small shrubs and perennial grasses growing underneath the patches controlled seedling performance. An increase in Stipa tenacissima and a decrease in Brachypodium retusum increased the probability of survival. The cover of these species and other small shrubs, litter depth and community phylogenetic distance, were also related to seedling survival. Seedlings planted on the northern edge of the patches were mostly affected by attributes of the biotic community. These traits were of lesser importance in seedlings planted underneath and in the southern edge of patches, suggesting that constraints to seedling establishment differed within the patches. Our study highlights the importance of taking into consideration community attributes over pair-wise interactions when evaluating the outcome of ecological interactions in multi-specific communities, as they have profound implications in the composition, function and management of semi-arid steppes. This research has been funded by project UNCROACH (Spanish Ministry of Science and Innovation; CGL2011-30581-C02-01), projects RECUVES and ESTRES (Spanish Ministry of the Environment, Rural and Marine Areas; 077/RN08/04.1and 063/SGTB/2007/7.1), project GRACCIE (Spanish Ministry of Science and Innovation, Consolider-Ingenio 2010 Program;CSD2007-00067) and Generalitat Valenciana (Programa G. Forteza;FPA/2009/029).

Biotic interactions are vital to ecosystem functioning. Interactions among individuals lie at the core of population and community dynamics, and therefore play a central role in the existence and persistence of species. Plants form the food base of most terrestrial ecosystems and are therefore not surprisingly involved in a substantial portion of biotic interactions. Plants, animals, and microbes face great challenges to survival in the desert environment, and these interactions play a critical role in the survival of many species. Fil: Marazzi, Brigitte. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina Fil: Bronstein, Judith L.. Fil: Sommers, Pacifica N.. Fil: López, Blanca R.. Fil: Bustamante Ortega, Enriquena. Fil: Búrquez, Alberto. Fil: Medellín, Rodrigo A.. Fil: Aslan, Clare. Fil: Franklin, Kim.

Background and aims – Contradictory evidence exists regarding the influence of bark peeling on the distribution of epiphytes among phorophyte species and vertical tree strata. However, there is little experimental evidence. The objectives of this study were to test whether bark-peeling rates differ between vertical strata and between phorophyte species, and whether the peeling rate correlates with epiphyte load among species of phorophytes.Materials and methods – In a tropical dry forest of central Mexico, bark exfoliation rates were measured over a period of 310–322 days in six woody species previously reported with different epiphyte distribution, including Bursera copallifera, B. glabrifolia (phoropytes with high epiphyte load), B. fagaroides, Conzattia multiflora, Ipomoea pauciflora and Sapium macrocarpum (phorophytes with low epiphyte load). In three strata (trunk, inner branches and outer branches) of five individuals of each phorophyte, three areas per individual were marked with paint and with a determined number of small plastic tubes stuck to the bark, in order to easily monitor the speed and quantity of any loss of this marked bark over time. These treatments were replicated on an adjacent pinewood board in order to quantify any loss of painted area or plastic tubes that occurred as a result of deterioration of the marking materials rather than peeling of the marked bark.Key results – The methods used for measuring bark peeling were strongly different. Plastic tubes gave an overestimation of bark peeling in the bark and in the pinewood boards; while paint remained in the pinewood boards, suggesting that paint loss on the bark was caused by peeling. Bark peeling rates differed slightly among the tree species and strata, regardless of whether or not the bark had peeling appearance. No pattern was found between bark peeling rate and the epiphyte load on each host.Conclusions – Our results support previous research which estimated that bark peeling with paint method provides a better estimate of peeling rate. In general, the bark peeling rate was the highest reported in literature for trees in a forest, suggesting that the epiphytes of this forest are adapted to colonize trees with high bark peeling rates. However, this attribute may be less important than others for determining host quality for epiphytes.

We assessed whether Guapira opposita, a common shrub in coastal sand dunes in southern Brazil, was involved in ecological succession and which factors influenced its positive effects (facilitation) on other plant species. Woody plants and bromeliad abundance and richness were higher under the canopy of G. opposita than in open areas. Facilitation was mainly determined by the height of G. opposita individuals, and was not influenced by shrub area, distance to freshwater bodies, to the sea or to forest patches. Our data evidence that facilitator species play a key role in restinga regeneration and their presence is critical to maintain ecosystem diversity., Positive interactions in plant communities are under-reported in subtropical systems most likely because they are not identified as stressful environments. However, environmental factors or disturbance can limit plant growth in any system and lead to stressful conditions. For instance, salinity and low nutrient and water availability generate a gradient of stressful conditions in coastal systems depending on distance to shore. In a tropical coastal system in SE Brazil, we aimed to assess whether Guapira opposita, a shrub common in restinga environments, acted as nurse involved in ecological succession and which factors influenced its facilitation process. We sampled perennial species above 10 cm in height under the canopy of 35 G. opposita individuals and in neighbouring open areas. Shrub height, canopy area and distance to freshwater bodies were measured in the field, and distance to the ocean was obtained from aerial images. In addition, we measured the distance to the closest forest patch as a potential source of seeds. Plant abundance and species richness were higher under the canopy of G. opposita than in open areas. Facilitation by G. opposita was mainly determined by shrub height, which had a positive relationship with woody and bromeliads abundance and species richness while there was no relationship with the other factors. Overall, our data evidence that tropical environments may be highly stressful for plants and that nurse species play a key role in the regeneration of restinga environments, where their presence is critical to maintain ecosystem diversity and function.

Journal of Vegetation Science 2016 Colonization in Mediterranean old-fields: The role of dispersal and plant-plant interactions ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) ) García-Cervigón, A.I.ab , Velázquez, E.cd , Wiegand, T.de , Escudero, A.f , Olano, J.M.a a iuFOR - Department of Agroforestry Sciences Universidad de Valladolid ES-42004 Soria Spain b Department of Natural Sciences Universidad Técnica Particular de Loja 110107 Loja Ecuador c Centro Universitario de Coyhaique Universidad de Magallanes José Miguel Carrera 485 Coyhaique 5951380 Chile View additional affiliations Abstract Questions: How do the dominant species in a Mediterranean community (Juniperus sabina, Juniperus communis and Pinus sylvestris) colonize abandoned fields? At what rates? Does dispersal limitation shape species colonization patterns? Does J. sabina act as nurse plant for the other two species? If so, in which stages of development: seedlings and saplings or older individuals? Location: Abandoned crop fields in the Alto Tajo Natural Park, central-eastern Spain. Methods: We mapped all individuals of the three species in three 4-14-ha plots, and aged them using dendrochronology. Spatial patterns in 2000, 1980 and 1960 were reconstructed according to estimated ages in 2014. We used a battery of spatial point-pattern analyses to evaluate dispersal in junipers, dispersal in pines, and the role of J. sabina as nurse plant for the other two species. Results: Both junipers colonized earlier than pines, probably due to their more effective endozoochorous dispersal. Late-coming pines, once established, expanded faster due to their higher seed productivity. Recent recruits of J. communis and P. sylvestris showed a random relationship with J. sabina canopies, whereas spatial patterns of older individuals in relation to J. sabina canopies ranged from attraction (plot 2 and marginally plot 1), suggesting facilitation, to repulsion in plot 3. These differences in spatial patterns between plots could be related to a shift in dominant herbivores, from sheep (plots 1 and 2) to red deer (plot 3). Conclusions: Dispersal and plant-plant interactions drove colonization in Mediterranean old fields. The inclusion of a temporal perspective in the analysis of spatial patterns allowed the detection of shifting interactions between J. sabina and the other two species, depending on their life stage. This is a clear advance compared with the usual static analyses, as it provides additional clues to interpret the mechanisms and processes underlying their origin. © 2016 International Association for Vegetation Science.

As a general rule, facilitation prevails over competition in stressful environments, but stress levels shift over time. Ideally, time should be included in plant-plant interactions studies by monitoring plants throughout their entire life-cycles, but this would require long study periods prior to reach any conclusive result. In this paper I present different ways to include time on the study of plant-plant interactions using dendrochronological techniques. By introducing different study cases I show how to include the information provided by plant age-related to ontogeny and age structure of the population- and ring width-related to secondary growth-in studies at the community, population and individual level. I highlight the potential for ecological studies to include the analysis of growth rings existing in shrubs and perennial herbs. To conclude, I introduce several variables registered in growth rings such as carbon stable isotope content or variables related to quantitative wood anatomy, which could be included as a complement in studies on plant-plant interactions. © 2016 Los Autores.

Plants often compete with closely related individuals due to limited dispersal, leading to two commonly invoked predictions on competitive outcomes. Kin selection, from evolutionary theory, predicts that competition between relatives will likely be weaker. The niche partitioning hypothesis, from ecological theory, predicts that competition between close relatives will likely be stronger. We tested for evidence consistent with either of these predictions by growing an annual legume in kin and nonkin groups in the greenhouse. We grew plant groups in treatments of symbiotic nitrogen fixing bacteria differing in strain identity and composition to determine if differences in the microbial environment can facilitate or obscure plant competition patterns consistent with kin selection or niche partitioning. Nonkin groups had lower fitness than expected, based on fitness estimates of the same genotypes grown among kin. Higher fitness among kin groups was observed in mixtures of N-fixing bacteria strains compared to single inoculations of bacteria strains present in the soil, which increased fitness differences between kin and nonkin groups. Lower fitness in nonkin groups was likely caused by increased competitive asymmetry in nonkin groups due to genetic differences in plant size combined with saturating relationships with plant size and fitness- i.e. Jensen's inequality. Our study suggests that microbial soil symbionts alter competitive dynamics among kin and nonkin. Our study also suggests that kin groups can have higher fitness, as predicted by kin selection theory, through a commonly heritable trait (plant size), without requiring kin recognition mechanisms.

Summary: Mixed-species forests generally sequester and store more carbon in above-ground woody biomass compared to species-poor systems. However, the mechanisms driving the positive relationship between diversity and above-ground wood production (AWP) remain unclear. We investigate the role of competition for light and water as possible sources of complementarity among Iberian pine and oak species. Using tree core data from permanent plots, we test the hypotheses that (i) contrasting abilities of pines and oaks to tolerate shade will promote AWP in mixtures, while (ii) drought stress results in less room for complementarity. We found that pine species receive more light, develop larger crowns and grow 138-155% faster when in mixture with oaks. However, this positive effect of species mixing on growth was severely reduced under drought conditions due to increased competition for water with neighbouring oaks. In contrast to pines, oak trees were less responsive to mixing, primarily as a result of their ability to tolerate shade and water shortage. Mixed pine-oak forests produce an average 48% more above-ground woody biomass compared to monocultures each year. However, the magnitude of the diversity effect on AWP fluctuates with time, decreasing noticeably in strength during drought years. Synthesis. Complementary light use strategies among neighbouring trees are critical in explaining why above-ground wood production (AWP) increases in mixed-species stands. In contrast, drought causes trees in mixture to compete more fiercely for below-ground resources, leaving less room for complementarity and causing positive diversity effects to lessen in strength. Together, these two mechanisms provide much needed context for AWP-diversity relationships in Mediterranean forests. Whether or not managing for mixed pine-oak forests proves to be beneficial for AWP is likely to depend on how climate changes in the Iberian Peninsula. © 2014 British Ecological Society., The research leading to these results received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 265171.

Although extensive research has been conducted on the temporal dynamics of plant-plant interactions, little is known about the effect of phosphorus (P) availability. In this study, Abies fabri and Picea brachytyla seedlings were collected from the late-stage Hailuogou glacier retreat area and grown under different P regimes (control and P fertilization) from year 2015 to 2016 in a common garden experiment to investigate whether plant-plant interactions are modulated by P availability. We found that P fertilization affected the relative competition intensity (RCI). Under control conditions in 2015, the growth of A. fabri was facilitated by the presence of P. brachytyla. Under P fertilization, the facilitative effect was more intensive: the leaf, stem and total biomass of A. fabri significantly increased under interspecific interaction compared with intraspecific interaction, but no effect was found in P. brachytyla. RCI showed similar tendencies both in 2015 and 2016. In addition, plant-plant interactions and P fertilization caused temporal variation in C, N, P and non-structural carbohydrate (NSC) contents. The growth of A. fabri greatly benefited from the presence of P. brachytyla when exposed to P fertilization and showed higher biomass, and C, N, P and NSC accumulations. Our results demonstrated interactive effects between environmental conditions (i.e. P availability) and plant-plant interactions that are closely related to resource accumulation.