AIMS: We postulated that soil productivity shifts associated with the development of facilitation-driven plant patches in abiotically stressful ecosystems can be faster than currently assumed. This ...might be due to the effect of the nurse plant by promoting resource accumulation both directly and indirectly through facilitating a plant community underneath its canopy. METHODS: We analysed a 40 year-ontogenetic gradient of Ononis tridentata, a colonizer shrub of barren gypsum soils in drylands. Soil fertility (chemical variables) and microbial productivity (microbial biomass, respiration and enzymatic activities) were measured along the gradient. The contribution of the nurse plant and the facilitated community to the soil fertility and microbial productivity shifts were separated and quantified by regression commonality analysis. RESULTS: Soil chemical fertility and microbial productivity rapidly increased during the first 20 years, with total organic carbon and microbial parameters rising six-fold along the Ononis ontogenetic gradient. This fast development of soil fertility was mostly explained by the unique effect of Ononis age (37.5 %) with an important contribution of the abundance of facilitated species (15.6 %). CONCLUSIONS: Facilitative interactions counterbalance the negative effect of harsh abiotic stress on the time rate and intensity at which plant and soil development occur in drylands.
Plants and soil microbes show parallel patterns of species-level diversity. Diverse plant communities release a wider range of organics that are consumed by more microbial species. We speculated, ...however, that diversity metrics accounting for the evolutionary distance across community members would reveal opposing patterns between plant and soil bacterial phylogenetic diversity. Plant phylogenetic diversity enhances plant productivity and thus expectedly soil fertility. This, in turn, might reduce bacterial phylogenetic diversity by favouring one (or a few) competitive bacterial clade. We collected topsoils in 15 semi-arid plant patches and adjacent low-cover areas configuring a plant phylodiversity gradient, pyrosequenced the 16S rRNA gene to identify bacterial taxa and analysed soil fertility parameters. Structural equation modelling showed positive effects of both plant richness and phylogenetic diversity on soil fertility. Fertility increased bacterial richness but reduced bacterial phylogenetic diversity. This might be attributed to the competitive dominance of a lineage based on its high relative fitness. This suggests biotic interactions as determinants of the soil bacterial community assembly, while emphasizing the need to use phylogeny-informed metrics to tease apart the processes underlying the patterns of diversity.
Phenotypic structure of plant facilitation networks Navarro‐Cano, Jose Antonio; Goberna, Marta; Valiente‐Banuet, Alfonso ...
Ecology letters,
March 2021, 2021-Mar, 2021-03-00, 20210301, Letnik:
24, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Identifying the plant traits that determine the outcome of facilitation interactions is essential to understand how communities are assembled and can be restored. Plant facilitation networks are ...phylogenetically structured but which traits are behind such a pattern is unknown. We sampled plant interactions in stressful ecosystems from south‐eastern Spain to build seedling and adult facilitation networks. We collected 20 morphological and ecophysiological traits for 151 species involved in interactions between 879 nurse individuals benefiting 24 584 seedlings and adults. We detected a significant phenotypic signal in the seedling facilitation network that was maintained in the adult network, whereby functionally similar nurses tended to facilitate functionally similar species whose traits differ from those of their nurses. We provide empirical evidence to support a long‐lasting theoretical postulate stating that facilitation networks are phenotypically structured. Trait matching through which nurse and facilitated species avoid phenotypic overlap, and consequently competition, is the main linkage rule shaping plant facilitation networks.
Plant facilitation networks are phenotypically structured. Functionally similar nurses tend to facilitate functionally similar species whose traits differ from those of their nurses.
While biodiversity is expected to enhance multiple ecosystem functions (EFs), the different roles of multiple biodiversity dimensions remain difficult to disentangle without carefully designed ...experiments. We sowed plant communities with independent levels of functional (FD) and phylogenetic diversities (PD), combined with different levels of fertilization, to investigate their direct and indirect roles on multiple EFs, including plant‐related EFs (plant biomass productivity, litter decomposability), soil fertility (organic carbon and nutrient pool variables), soil microbial activity (respiration and nutrient cycling), and an overall multifunctionality. We expected an increase in most EFs in communities with higher values of FD and/or PD via complementarity effects, but also the dominant plant types (using community weighted mean, CWM, independent of FD and PD) via selection effects on several EFs. The results showed strong direct effects of different dimensions of plant functional structure parameters on plant‐related EFs, through either CWM or FD, with weak effects of PD. Fertilization had significant effects on one soil microbial activity and indirect effects on the other variables via changes in soil abiotic properties. Dominant plant types and FD showed only indirect effects on soil microbial activity, through litter decomposition and soil abiotic properties, highlighting the importance of cascading effects. This study shows the relevance of complementary dimensions of biodiversity for assessing both direct and cascading effects on multiple EFs.
Co‐occurrence network analysis based on amplicon sequences is increasingly used to study microbial communities. Patterns of co‐existence or mutual exclusion between pairs of taxa are often ...interpreted as reflecting positive or negative biological interactions. However, other assembly processes can underlie these patterns, including species failure to reach distant areas (dispersal limitation) and tolerate local environmental conditions (habitat filtering). We provide a tool to quantify the relative contribution of community assembly processes to microbial co‐occurrence patterns, which we applied to explore soil bacterial communities in two dry ecosystems. First, we sequenced a bacterial phylogenetic marker in soils collected across multiple plots. Second, we inferred co‐occurrence networks to identify pairs of significantly associated taxa, either co‐existing more (aggregated) or less often (segregated) than expected at random. Third, we assigned assembly processes to each pair: patterns explained based on spatial or environmental distance were ascribed to dispersal limitation (2%–4%) or habitat filtering (55%–77%), and the remaining to biological interactions. Finally, we calculated the phylogenetic distance between taxon pairs to test theoretical expectations on the linkages between phylogenetic patterns and assembly processes. Aggregated pairs were more closely related than segregated pairs. Furthermore, habitat‐filtered aggregated pairs were closer relatives than those assigned to positive interactions, consistent with phylogenetic niche conservatism and cooperativism among distantly related taxa. Negative interactions resulted in equivocal phylogenetic signatures, probably because different competitive processes leave opposing signals. We show that microbial co‐occurrence networks mainly reflect environmental tolerances and propose that incorporating measures of phylogenetic relatedness to networks might help elucidate ecologically meaningful patterns.
Plants and soil microbes show parallel patterns of species-level diversity. Diverse plant communities release a wider range of organics that are consumed by more microbial species. We speculated, ...however, that diversity metrics accounting for the evolutionary distance across community members would reveal opposing patterns between plant and soil bacterial phylogenetic diversity. Plant phylogenetic diversity enhances plant productivity and thus expectedly soil fertility. This, in turn, might reduce bacterial phylogenetic diversity by favouring one (or a few) competitive bacterial clade. We collected topsoils in 15 semi-arid plant patches and adjacent low-cover areas configuring a plant phylodiversity gradient, pyrosequenced the 16S rRNA gene to identify bacterial taxa and analysed soil fertility parameters. Structural equation modelling showed positive effects of both plant richness and phylogenetic diversity on soil fertility. Fertility increased bacterial richness but reduced bacterial phylogenetic diversity. This might be attributed to the competitive dominance of a lineage based on its high relative fitness. This suggests biotic interactions as determinants of the soil bacterial community assembly, while emphasizing the need to use phylogeny-informed metrics to tease apart the processes underlying the patterns of diversity.
High‐throughput sequencing (HTS) is increasingly being used for the characterization and monitoring of biodiversity. If applied in a structured way, across broad geographical scales, it offers the ...potential for a much deeper understanding of global biodiversity through the integration of massive quantities of molecular inventory data generated independently at local, regional and global scales. The universality, reliability and efficiency of HTS data can potentially facilitate the seamless linking of data among species assemblages from different sites, at different hierarchical levels of diversity, for any taxonomic group and regardless of prior taxonomic knowledge. However, collective international efforts are required to optimally exploit the potential of site‐based HTS data for global integration and synthesis, efforts that at present are limited to the microbial domain. To contribute to the development of an analogous strategy for the nonmicrobial terrestrial domain, an international symposium entitled “Next Generation Biodiversity Monitoring” was held in November 2019 in Nicosia (Cyprus). The symposium brought together evolutionary geneticists, ecologists and biodiversity scientists involved in diverse regional and global initiatives using HTS as a core tool for biodiversity assessment. In this review, we summarize the consensus that emerged from the 3‐day symposium. We converged on the opinion that an effective terrestrial Genomic Observatories network for global biodiversity integration and synthesis should be spatially led and strategically united under the umbrella of the metabarcoding approach. Subsequently, we outline an HTS‐based strategy to collectively build an integrative framework for site‐based biodiversity data generation.
The plantation of exotic species has been a common practice in (semi-) arid areas worldwide aiming to restore highly degraded habitats. The effects of these plantations on plant cover or soil erosion ...have been widely studied, while little attention has been paid to the consequences on soil quality and belowground biological communities. This study evaluates the long-term (>60 years) effects of the exotic species Acacia cyclops and Pinus halepensis revegetation on soil properties, including microbiome, in an arid island. Soils under exotic plantation were compared to both degraded soils with a very low cover of native species and soils with well-preserved native plant communities. Seven scenarios were selected in a small area (~25 ha) with similar soil type but differing in the plant cover. Topsoils (0–15 cm) were analyzed for physical, chemical and biochemical properties, and amplicon sequencing of bacterial and fungal communities. Microbial diversity was similar among soils with exotic plants and native vegetation (Shannon's index = 5.26 and 5.34, respectively), while the most eroded soils exhibited significantly lower diversity levels (Shannon's index = 4.72). Bacterial and fungal communities' composition in degraded soils greatly differed from those in vegetated soils (Canberra index = 0.85 and 0.92, respectively) likely due to high soil sodicity, fine textures and compaction. Microbial communities' composition also differed in soils covered with exotic and native species, to a greater extent for fungi than for bacteria (Canberra index = 0.94 and 0.89, respectively), due to higher levels of nutrients, microbial biomass and activity in soils with native species. Results suggest that reforestation succeeded in avoiding further soil degradation but still leading to relevant changes in soil microbial community that may have negative effects on ecosystem stability. Information gained in this research could be useful for environmental agencies and decision makers about the controversial replacement of exotic plants in insular territories.
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•Plantations with exotic species led to similar soil microbial diversity compared to native vegetation.•Soil microbial communities' composition differed between exotic plantations and preserved native vegetation.•Microbial activities were higher under native species and denote a higher conservation status.
The classical relationship between biodiversity and ecosystem functioning can be better understood when the phylogenetic component of biodiversity is considered. We linked plant phylodiversity and ...ecosystem functioning in a water-limited gypsum ecosystem driven by plant facilitation. We tested whether (1) plant facilitation relaxes the abiotic filter imposed by gypsum, allowing the establishment of non-gypsophyte plant species, and consequently increasing plant phylodiversity, and (2) plant phylodiversity influences soil microbial productivity. Our data revealed that the gypsophyte Ononis tridentata spatially determines a macrophytic mosaic, ameliorates the microenvironment, and maximizes plant richness and phylodiversity through facilitating non-gypsophyte species. Beyond the direct effect of the nurse plant on soil microbial biomass, activity, and respiration, the analyses suggest a direct effect of plant phylodiversity (MPD) on these general indicators of soil microbial productivity. Plant diversity (Shannon index) neither correlated with the mentioned parameters nor with specific indicators of C, N and P cycling. This is the first report of a relationship between producer phylodiversity and decomposer productivity, which supports phylogenetic diversity as a relevant player of the ecosystem functioning.
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