Examinando por Autor "De la Cruz, Marcelino"

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A dimmer shade of pale: revealing the faint signature of local assembly processes on the structure of strongly filtered plant communities
(Wiley, 2020-10-08) López-Angulo, Jesús; De la Cruz, Marcelino; Pescador, David S.; Sánchez, Ana M.; Escudero, Adrián
Trait-based ecology suggests that abiotic filtering is the main mechanism structuring the regional species pool in different subsets of habitat-specific species. At more local spatial scales, other ecological processes may add on giving rise to complex patterns of functional diversity (FD). Understanding how assembly processes operating on the habitat-specific species pools produce the locally observed plant assemblages is an ongoing challenge. Here, we evaluated the importance of different processes to community assembly in an alpine fellfield, assessing its effects on local plant trait FD. Using classical randomization tests and linear mixed models, we compared the observed FD with expectations from three null models that hierarchically incorporate additional assembly constraints: stochastic null models (random assembly), independence null models (each species responding individual and independently to abiotic environment), and co-occurrence null models (species responding to environmental variation and to the presence of other species). We sampled species composition in 115 quadrats across 24 locations in the central Pyrenees (Spain) that differed in soil conditions, solar radiation and elevation. Overall, the classical randomization tests were unable to find differences between the observed and expected functional patterns, suggesting that the strong abiotic filters that sort out the flora of extreme regional environments blur any signal of other local processes. However, our approach based on linear mixed models revealed the signature of different ecological processes. In the case of seed mass and leaf thickness, observed FD significantly deviated from the expectations of the stochastic model, suggesting that fine-scale abiotic filtering and facilitation can be behind these patterns. Our study highlights how the hierarchical incorporation of ecological additional constraints may shed light on the dim signal left by local assembly processes in alpine environments.
Dispersal syndrome influences the match between seed rain and soil seed bank of woody species in a Neotropical dry forest
(Wiley, 2020-11) Jara-Guerrero, Andrea; Espinosa, Carlos I.; Méndez, Marcos; De la Cruz, Marcelino; Escudero, Adrián
Aims Plant recruitment may occur immediately after seed dispersal from the mother plant, or be delayed through the formation of soil seed banks. These strategies are known to be mediated by adaptations of seed dispersal and reproductive phenology, which if analyzed together can provide valuable information about the regeneration strategies of species. We explored whether dispersal syndrome and/or seed dispersal phenology control the similarity between standing vegetation, seed rain and soil seed bank in a seasonally dry tropical forest (SDTF) in Southern Ecuador. Location Arenillas Ecological Reserve, Southwestern Ecuador, the biogeographic region of Pacific Coastal Ecuador. Methods We recorded standing vegetation of woody species in a 9-ha permanent plot and sampled soil seed bank from 265 cores of 0.06 m2. Additionally, we sampled seed rain from 265 seed traps of 0.64 m2 for one year. We evaluated similarity in species composition, species richness, and abundance between the three components for all species and for each dispersal syndrome. Results The community we studied showed a high similarity in species composition between components. The similarity was influenced by dispersal syndrome and the seed dispersal phenology. Similarity between seed rain and standing vegetation was high in species that dispersed in the rainy season, such as zoochorous species, while for autochorous species, compared with the other dispersal syndromes it was higher between seed bank and standing vegetation. Conclusions In our SDTF, dispersal phenology seemed to influence whether seeds had direct germination or entered the soil seed bank and influenced the match between seed rain and soil seed bank, suggesting different regeneration strategies related to dispersal ability.
Ecological drivers of fine-scale distribution of arbuscular mycorrhizal fungi in a semiarid Mediterranean scrubland
(Oxford Academic, 2023-06) López-Angulo, Jesús; Matesanz, Silvia; Illuminati, Angela; Sánchez Pescador, David; Sánchez, Ana María; Pías, Beatriz; Chacón-Labella, Julia; De la Cruz, Marcelino; Escudero, Adrián
Background and Aims Arbuscular mycorrhizal (AM) fungi enhance the uptake of water and minerals by the plant hosts, alleviating plant stress. Therefore, AM fungal–plant interactions are particularly important in drylands and other stressful ecosystems. We aimed to determine the combined and independent effects of above- and below-ground plant community attributes (i.e. diversity and composition), soil heterogeneity and spatial covariates on the spatial structure of the AM fungal communities in a semiarid Mediterranean scrubland. Furthermore, we evaluated how the phylogenetic relatedness of both plants and AM fungi shapes these symbiotic relationships. Methods We characterized the composition and diversity of AM fungal and plant communities in a dry Mediterranean scrubland taxonomically and phylogenetically, using DNA metabarcoding and a spatially explicit sampling design at the plant neighbourhood scale. Key Results The above- and below-ground plant community attributes, soil physicochemical properties and spatial variables explained unique fractions of AM fungal diversity and composition. Mainly, variations in plant composition affected the AM fungal composition and diversity. Our results also showed that particular AM fungal taxa tended to be associated with closely related plant species, suggesting the existence of a phylogenetic signal. Although soil texture, fertility and pH affected AM fungal community assembly, spatial factors had a greater influence on AM fungal community composition and diversity than soil physicochemical properties. Conclusions Our results highlight that the more easily accessible above-ground vegetation is a reliable indicator of the linkages between plant roots and AM fungi. We also emphasize the importance of soil physicochemical properties in addition to below-ground plant information, while accounting for the phylogenetic relationships of both plants and fungi, because these factors improve our ability to predict the relationships between AM fungal and plant communities.
Environmental heterogeneity blurs the signature of dispersal syndromes on spatial patterns of woody species in a moist tropical forest
(Public Library of Science, 2018-02) Ramón, Pablo; Velázquez, Eduardo; Escudero, Adrián; De la Cruz, Marcelino
We assessed the relative importance of dispersal limitation, environmental heterogeneity and their joint effects as determinants of the spatial patterns of 229 species in the moist tropical forest of Barro Colorado Island (Panama). We differentiated five types of species according to their dispersal syndrome; autochorous, anemochorous, and zoochorous species with small, medium-size and large fruits. We characterized the spatial patterns of each species and we checked whether they were best fitted by Inhomogeneous Poisson (IPP), Homogeneous Poisson cluster (HPCP) and Inhomogeneous Poisson cluster processes (IPCP) by means of the Akaike Information Criterion. We also assessed the influence of species’ dispersal mode in the average cluster size. We found that 63% of the species were best fitted by IPCP regardless of their dispersal syndrome, although anemochorous species were best described by HPCP. Our results indicate that spatial patterns of tree species in this forest cannot be explained only by dispersal limitation, but by the joint effects of dispersal limitation and environmental heterogeneity. The absence of relationships between dispersal mode and degree of clustering suggests that several processes modify the original spatial pattern generated by seed dispersal. These findings emphasize the importance of fitting point process models with a different biological meaning when studying the main determinants of spatial structure in plant communities.
Estimating belowground plant abundance with DNA metabarcoding
(Wiley, 2019-09) Matesanz, Silvia; Pescador, David S.; Pías, Beatriz; Sánchez, Ana M.; Chacón-Labella, Julia; Illuminati, Angela; De la Cruz, Marcelino; López-Angulo, Jesús; Marí-Mena, Neus; Vizcaíno, Antón; Escudero, Adrián
Most work on plant community ecology has been performed above ground, neglecting the processes that occur in the soil. DNA metabarcoding, in which multiple species are computationally identified in bulk samples, can help to overcome the logistical limitations involved in sampling plant communities belowground. However, a major limitation of this methodology is the quantification of species’ abundances based on the percentage of sequences assigned to each taxon. Using root tissues of five dominant species in a semi-arid Mediterranean shrubland (Bupleurum fruticescens, Helianthemum cinereum, Linum suffruticosum, Stipa pennata and Thymus vulgaris), we built pairwise mixtures of relative abundance (20%, 50% and 80% biomass), and implemented two methods (linear model fits and correction indices) to improve estimates of root biomass. We validated both methods with multispecies mixtures that simulate field-collected samples. For all species, we found a positive and highly significant relationship between the percentage of sequences and biomass in the mixtures (R2 = .44–.66), but the equations for each species (slope and intercept) differed among them, and two species were consistently over- and under-estimated. The correction indices greatly improved the estimates of biomass percentage for all five species in the multispecies mixtures, and reduced the overall error from 17% to 6%. Our results show that, through the use of post-sequencing quantification methods on mock communities, DNA metabarcoding can be effectively used to determine not only species’ presence but also their relative abundance in field samples of root mixtures. Importantly, knowledge of these aspects will allow us to study key, yet poorly understood, belowground processes.
Every little helps: the functional role of individuals in assembling any plant community, from the richest to monospecific ones
(Wiley, 2021-09) Escudero, Adrián; Matesanz, Silvia; Pescador, David S.; De la Cruz, Marcelino; Valladares, Fernando; Cavieres, Lohengrin A.
Plant trait-based ecology is a powerful extension of the attempt of community ecologists to unveil assembly mechanisms. However, the two main expected determinants of community assembly, niche and neutral processes, can be confused under this framework. Here, we propose to move from trait-based to phenotype-based community ecology, accounting for the variation between individuals (phenotypes affected by the abiotic and biotic environment, and vice versa), and explicitly considering their ability to compete with or facilitate its neighbours. This would shift our focus from species’ niche responses to niche specialization of phenotypes, reducing the space for neutrality at the finest scales. The current assembly framework, based mainly on niche complementarity and using species-average functional traits, has been developed exploring mega-diverse communities, but it fails at describing poor plant communities. Under this framework, monospecificity would be interpreted as an arena where functionally similar individuals compete, consequently leading to regular patterns, which are rarely found in nature. Our niche specialization framework could help explaining coexistence in rich plant communities, where the higher fraction of functional variation is found between species, whereas the intraspecific trait variation dominates in poor species and monospecific communities. We propose a guide to conduct massive phenotyping at the community scale based on the use of visible and near-infrared spectroscopy. We also discuss the need to integrate the so-called plant's eye perspective based on the use of spatial pattern statistics in the current community ecology toolbox.
Fencing promotes fast recovery of demographic processes after grazing-driven collapse in Bursera graveolens forests
(Elsevier, 2021-11-01) Patiño, Jorge; Ramón, Pablo; Gusmán-Montalván, Elizabeth; Escudero, Adrián; De la Cruz, Marcelino
Global change pressures are jeopardizing the functioning and structure of most tropical forests and clouding the future for their biodiversity and provided services. Although the impact of direct destruction through deforestation and fragmentation is currently in the research portfolio, overgrazing, which is more diffuse and generalized but chronic, especially in the seasonal dry forests, has been by far less addressed. Overgrazing can lead to a dramatic change in natural regeneration, often triggering the collapse of dominant species. The almost monospecific dry forests of Bursera graveolens, one of the most representative forest of the Tumbesian region, are on the verge of extinction due to both direct destruction and chronic overgrazing and regeneration collapse in forest remnants. Here, we evaluated the impact of a very simple measure, the installation of fences, on the regeneration of ecological processes affecting the dominant species. We mapped and measured all Bursera individuals with a height greater than or equal to 30 cm in six 1-ha plots, 3 within and 3 outside fenced areas. Using spatial point pattern analysis, we inferred the importance of demographic and ecological processes affecting adults and juveniles in fenced and unfenced areas. The spatial structure of adults was similar in fenced and unfenced areas, varying from random to aggregated patterns, showing that fences did not interfere with ecological processes affecting adult trees. On the contrary, we found 2765 juveniles in the three fenced plots but none in free ranging areas. Juveniles showed heterogeneous clustered patterns, and their distribution and growth were negatively influenced both by the presence and the height of adult trees. On average, there was an exclusion zone of 10 m around adult trees were recruitment of juveniles was limited. Competition among juveniles appeared to be negligible. All in all, these results suggest that, in addition to recruitment, two of the main mechanisms that rule tree population dynamics in tropical forests, i.e., dispersal limitation and a Janzen-Connell-like mechanism favoring recruiting far from adult trees have been immediately restored in the fenced area. This shows that fencing is a viable tool for a fast regeneration and conservation of Bursera forests.
Focusing on individual species reveals the specific nature of assembly mechanisms in a tropical dry-forest
(Elsevier, 2018-10) Gusmán-M., Elizabeth; De la Cruz, Marcelino; Espinosa, Carlos I.; Escudero, Adrián
We employed an individual-species approach based on the plant’s eye perspective to disentangle the effects of individual species on community assembly in a dry tropical forest of southern Ecuador. We completely mapped a forest plot of 9 ha, and measured several functional traits (leaf area, specific leaf area, wood density, seed mass and maximum height) for tree and shrub species. To account for stochastic and habitat filtering effects, we fitted spatial point processes for the 23 more abundant species in the plot, which confirmed that all species responded to plot scale habitat filtering and 14 were dispersal-limited. We tested the hypothesis that facilitative interactions would be prevalent in this dry forest. For this, we compared the distribution of taxonomic (TD), functional (FD) and phylogenetic (PD) diversity in the neighborhood of the studied species with the diversity expected under a null model combining habitat filtering and stochastic assembly. We found that in the fine spatial scales where species interactions are expected to occur (i.e., neighborhoods of 1–20 m) eight species did not show any significant pattern for TD, FD or PD. Eleven species showed evidences of facilitation (i.e., accumulated more TD than expected) but in some cases the facilitated neighborhoods had more FD or PD than expected, suggesting the joint effect of facilitation and competition based on niche differences. One species showed less TD than expected, accompanied by lower FD and higher PD, suggesting competition based on fitness differences. Our study shows that in this dry tropical forest, where abiotic stress is prevalent, the assembly of diversity is controlled by environmental heterogeneity and both facilitative and competitive biotic processes, all of them acting simultaneously and at the same scale in the same neighborhoods.
Landscape heterogeneity as a surrogate of biodiversity in mountain systems: What is the most appropriate spatial analytical unit?
(Elsevier, 2018-02) García-Llamas, Paula; Calvo, Leonor; De la Cruz, Marcelino; Suárez-Seoane, Susana
The estimated potential of landscape metrics as a surrogate for biodiversity is strongly dependent on the spatial analytical unit used for evaluation. We assessed the relationship between terrestrial vertebrate species richness (total and taxonomic) and structural landscape heterogeneity, testing the impact of using different spatial analytical units in three mountain systems in Spain. Landscape heterogeneity was quantified through an additive partitioning of the Shannon diversity index of landscape classes. Both landscape heterogeneity and species richness were calculated using two spatial analytical unit approaches: eco-geographic vs. arbitrary (i.e., watersheds vs. square windows of different sizes 20 × 20 km, 50 × 50 km, 100 × 100 km). We predicted species richness on the basis of landscape heterogeneity by fitting separate linear models for each spatial analytical unit approach. The main results obtained showed that landscape heterogeneity influenced terrestrial vertebrate species richness. However, the emerging relationships were dependent on the spatial analytical unit approach. The eco-geographic approach showed significant relationships between landscape heterogeneity and total and taxonomic species richness in almost all cases (except mammals). Considering the arbitrary approach, landscape heterogeneity appeared as a predictor of species richness only for mammals and breeding birds and at the coarsest spatial scales. Our results claim for further consideration of eco-geographical spatial analytical unit approaches in biodiversity studies and show that the methods of this study offer a valuable cost-effective framework for biodiversity management and spatial modeling, with potential to be adapted to national and global applications.
Larger aboveground neighbourhood scales maximise similarity but do not eliminate discrepancies with belowground plant diversity in a Mediterranean shrubland
(Springer, 2021-01-15) Illuminati, Angela; López-Angulo, Jesús; De la Cruz, Marcelino; Chacón-Labella, Julia; Pescador, David S.; Pías, Beatriz; Sánchez, Ana M.; Escudero, Adrián; Matesanz, Silvia
Aims An unresolved question in plant ecology is whether diversity of the aboveground and belowground compartments of a plant community is similar at different neighbourhood scales. We investigated how the similarity between both compartments varies with the aboveground sampling grain and if significant discrepancies exist between aboveground and belowground plant diversity at the maximum similarity scale. Methods We fully mapped the aboveground perennial plant community of a 64 m2 plot in a Mediterranean shrubland and analysed this compartment by assessing diversity in 5 to 50 cm radii circles centred in soil cores. We sampled 2.5 cm radius root cores at two different depths and identified plant species by using DNA metabarcoding to characterise the belowground compartment. We quantified differences in species richness, composition and species’ spatial distribution above- and belowground. Results The differences between aboveground and belowground communities were affected by the size of the aboveground sampling grain and were minimised when considering a circle of 20 cm radius in the aboveground. We found a significant dissimilarity in richness and composition between the two compartments, with larger differences when considering the deeper soil layer only. Conclusions Our results showed that the spatial grain selected to sample a plant community aboveground and belowground is critical to characterise them in a comparable manner. Although their composition is related, species distribution patterns strongly differ, suggesting the simultaneous action of different assembly mechanisms. Our results call for caution when studying community assembly considering only the standing vegetation, since total plant diversity can be underappreciated.
Recruitment facilitation in expanding forests of Mediterranean juniper is sex-biased
(Elsevier, 2022-02-01) Martín-Forés, Irene; Bastías, Cristina C.; Acuña-Míguez, Belén; Magro, Sandra; Valladares, Fernando; De la Cruz, Marcelino
Despite noticeable concern about the deforestation rate worldwide, the forest surface in Europe has considerably expanded over the past centuries as a consequence of the rural exodus and abandonment of agrarian practices. Tree recruitment associated with forest regrowth is a multi-stage process influenced by several biotic and abiotic factors. Yet, it is uncertain whether their influence on recruitment patterns and dynamics varies along a gradient of forest expansion. Similarly, for dioceious species, the influence of tree sex in recruitment is not entirely understood. Here, we aim to elucidate what drives Spanish juniper recruitment in expanding forests. Specifically, we hypothesized that facilitation by conspecifics and heterospecific woody species would occur at the expanding front, where environmental conditions are harsher and that recruitment would be preferably associated to female trees because of the likelihood of mature cones produced by them germinating in the nearby area. The study was conducted in Mediterranean forests of Juniperus thurifera in central Spain. A total of 17 plots were delimited along a gradient of forest expansion including three stages: i) old forests, ii) an intermediate zone and iii) novel forests at the expanding front. Within each plot all J. thurifera individuals (saplings and adults) were mapped. We also recorded bio-volumetric characteristics and tree sex for all adult trees and estimated the percentage of cover of heterospecific woody species within the area of influence of each adult individual. We analysed the spatial pattern of J. thurifera individuals for each stand (plot). Using a novel spatial approach, we evaluated how conspecific (female and male tree sizes) and heterospecific (woody cover) vegetation influenced sapling density along a forest expansion gradient. We also studied the effects of the stage of the forest expansion gradient and the sex of adult trees on the spatial association between adults and saplings. Our results showed that sapling recruitment was negatively influenced by conspecific adult size along the whole gradient, while the effect of heterospecific woody vegetation was always positive. Conspecific facilitation of recruitment in J. thurifera forests occurred at their expanding front where saplings were associated to male adult trees. Despite having been overlooked in conservation policies, recently colonised areas in extreme environments are key targets to implement management measures aimed at achieving forest restoration, which aligns with the Aichi targets and the biodiversity policies of the European Union.
Species richness influences the spatial distribution of trees in European forests
(Wiley, 2020-03) Bastias, Cristina C.; Truchado, Daniel A.; Valladares, Fernando; Benavides, Raquel; Bouriaud, Olivier; Bruelheide, Helge; Coppi, Andrea; Finér, Leena; Gimeno, Teresa E.; Jaroszewicz, Bogdan; Scherer-Lorenzen, Michael; Selvi, Federico; De la Cruz, Marcelino
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.
Tales from the underground: Soil heterogeneity and not only above-ground plant interactions explain fine-scale species patterns in a Mediterranean dwarf-shrubland
(Wiley, 2020-05) Pescador, David S.; De la Cruz, Marcelino; Chacón-Labella, Julia; Pavón-García, Javier; Escudero, Adrián
Questions The current paradigm of plant community assembly relies on a set of processes operating at particular spatial scales. It is assumed that as the spatial scale becomes finer, environmental filtering loses its importance in favor of biotic interactions and neutral processes. Thus, at the very fine spatial scale represented by a rectangular plot of 72.25 m2 in a Mediterranean semiarid dwarf-shrubland, we ask: (a) are the spatial distributions of individuals of the different species explained by neutral models; (b) are these distributions dependent on above-ground plant interactions with the dominant species in the community; and/or (c) are they responding to the spatial variation of different soil variables, in a kind of fine-scale environmental filtering? Location Central Spain. Methods To assess the correlates of fine-scale (i.e., from 0.05–2.00 m) spatial patterns of the species in the community, we fully mapped all perennial individuals inside the rectangular plot. For each species, we fitted one complete spatial randomness (CSR) model that does not assume spatial heterogeneity and three weighted-average inhomogeneous Poisson process (IPP) models using six soil covariates, distribution patterns of the four above-ground dominant plants in the community or both types of covariates. All models were evaluated and compared to select the best-fitting weighted-average model. Results We recorded 7,988 individuals of 22 species. Patterns of all species were appropriately explained by IPP models. For most species the best-fitting weighted-average model included both soil and dominant plants (i.e., 15) or only soil covariates (i.e., 6). The improvement provided by the best-fitting weighted-averaging model in comparison with the CSR model was consistently high (81%). Conclusions Our approach suggests that species in this dwarf-shrubland are mainly structured by soil heterogeneity and modulated in some cases by the interactions established with the dominant species.
The assembly of a plant network in alpine vegetation
(Wiley, 2018-11) Losapio, Gianalberto; De la Cruz, Marcelino; Escudero, Adrián; Schmid, Bernhard; Schöb, Christian
Questions Positive and negative associations among species influence the structure of plant communities. Yet how these plant associations are assembled at the community level is poorly understood. We propose a new approach that combines spatial ecology, network theory and trait-based ecology to examine the assembly of plant–plant associations at the community level. Location Gemmipass, Swiss Alps. Methods We fully mapped an alpine plant community at the individual plant level, recording both plant coordinates and functional traits for each individual. We identified non-random species associations using spatial point-pattern analysis and partialled out the effect of abiotic heterogeneity. We then analysed the plant network structure and used plant traits to predict species associations. Results We identified 36 significant spatial associations between plant species, 34 positive and two negatives. Dominant, stress-tolerant species such as Dryas octopetala, Linaria alpina and Leontodon montanus were highly connected in the network, whereas rare, water- and nutrient-demanding species such as Saxifraga aizoides, Galium anisophyllon and Thymus praecox were less connected compared to random expectation. The plant network was clustered, meaning that species were overall more connected among each other than expected by chance. Conclusions Positive associations among species characterized the studied plant community. Besides the primary effect of associations of the “foundation” species D. octopetala with other species, these “subordinate” plants were also associated with each other. Our study reveals the assembly of plant communities as driven by positive associations among stress-tolerant pioneer species, highlighting their role in supporting the cohesiveness of alpine plant communities.
The effect of plant–plant interactions as a key biotic process mediating the spatial variation of phenotypes in a Pinus sylvestris forest
(Springer, 2022-05-09) Carvalho, Barbara; De la Cruz, Marcelino; Escudero, Adrián; Bastias, Cristina C.; Valladares, Fernando; Benavides, Raquel
Plant interactions are among the fundamental processes shaping the structure and functioning of ecosystems as they modulate competitive dynamics. However, the connection between the response of individual growth to neighbours and to environmental conditions and the mechanisms determining interactions in monospecific stands remain poorly understood. Here, we followed a phenotypic-based approach to disentangle the effect of plant size, neighbourhood interactions and microhabitat effects on Pinus sylvestris growth and traits, as well as their spatial variation of growth. We mapped all adult trees (1002 pines) in a 2 ha stand and measured their height, DBH and crown projection. For each individual, we assessed its growth and a competition index in relation to the closest neighbours. Soil chemical and physical properties and ground cover were also measured in a grid within the stand. We analysed the effects of tree size, neighbour competition and microhabitat variation on tree growth with a linear model. We also used spatial mark-correlation functions to explore the spatial dependence of tree age, secondary growth and phenotypic traits. Our results showed that trees with close neighbours displayed lower growth rates, whilst individuals with larger growths appeared scattered throughout the stand. Moreover, we found that growth depended on competition, tree height and crown area while tree growth poorly correlated with age or microhabitat conditions. Our findings highlight the importance of forest structure, in regulating inter-tree competition and growth in a Mediterranean pure stand and they provide insight into the causes and consequences of intraspecific variation in this system.
The role of root community attributes in predicting soil fungal and bacterial community patterns
(Wiley, 2020-11) López-Angulo, Jesús; De la Cruz, Marcelino; Chacón-Labella, Julia; Illuminati, Angela; Matesanz, Silvia; Pescador, David S.; Pías, Beatriz; Sánchez, Ana M.; Escudero, Adrián
Roots are assumed to play a major role in structuring soil microbial communities, but most studies exploring the relationships between microbes and plants at the community level have only used aboveground plant distribution as a proxy. However, a decoupling between belowground and aboveground plant components may occur due to differential spreading of plant canopies and root systems. Thus, soil microbe–plant links are not completely understood. Using a combination of DNA metabarcoding and spatially explicit sampling at the plant neighbourhood scale, we assessed the influence of the plant root community on soil bacterial and fungal diversity (species richness, composition and β-diversity) in a dry Mediterranean scrubland. We found that root composition and biomass, but not richness, predict unique fractions of variation in microbial richness and composition. Moreover, bacterial β-diversity was related to root β-diversity, while fungal β-diversity was related to aboveground plant β-diversity, suggesting that plants differently influence both microbial groups. Our study highlights the role of plant distribution both belowground and aboveground, soil properties and other spatially structured factors in explaining the heterogeneity in soil microbial diversity. These results also show that incorporating data on both plant community compartments will further our understanding of the relationships between soil microbial and plant communities.