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The ecological study of root systems lags behind the understanding of the aboveground components of plant communities, mainly due to methodological challenges. As ecological root theory develops complexity, root investigation methods are required to meet higher standards of quantitative and detailed data. Spatial root density distribution of plants represents one of the main features pursued in ecological studies, as it provides insight into root foraging behavior and belowground competition. To study root density, ecologists should preferably use and develop methods with the potential to provide the most comprehensive information: Individual Root Density Distribution (IRDD), i.e. individual-level and spatially-explicit root density maps. Here, we review the existing methods to detect roots in the field (detection methods), and to infer the identity of these roots (identification methods). We discuss potential combinations of Detection and Identification (DI) methods, and the data quality that these combinations yield in respect to IRDD. We anticipate that root field ecologists progressively may want to adopt DI methods showing the highest potential to provide high-quality IRDD. These methods are (i) ground-penetrating radar or acoustic tomography in combination with tracking the roots to the individual plant (i.e. skeleton method sensu lato), (ii) soil sampling in combination with in situ root staining (for physiological individuals), or (iii) soil sampling in combination with DNA microsatellites or single nucleotide polymorphism sequencing (for genetic individuals).

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. 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. 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. 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.

The dataset presented here was collected by the GenTree project (EU-Horizon 2020), which aims to improve the use of forest genetic resources across Europe by better understanding how trees adapt to their local environment. This dataset of individual tree-core characteristics including ring-width series and whole-core wood density was collected for seven ecologically and economically important European tree species: silver birch (Betula pendula), European beech (Fagus sylvatica), Norway spruce (Picea abies), European black poplar (Populus nigra), maritime pine (Pinus pinaster), Scots pine (Pinus sylvestris), and sessile oak (Quercus petraea). Tree-ring width measurements were obtained from 3600 trees in 142 populations and whole-core wood density was measured for 3098 trees in 125 populations. This dataset covers most of the geographical and climatic range occupied by the selected species. The potential use of it will be highly valuable for assessing ecological and evolutionary responses to environmental conditions as well as for model development and parameterization, to predict adaptability under climate change scenarios., Measurement(s)growth ring • wood densityTechnology Type(s)measuring table • calculationFactor Type(s)tree speciesSample Characteristic - OrganismBetula pendula • Fagus sylvatica • Picea abies • Populus nigra • Pinus pinaster • Pinus sylvestris • Quercus petraeaSample Characteristic - LocationEurope Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.11294993

The amount of quantitative genetic variation within an invasive species influences its ability to adapt to conditions in the new range and its long-term persistence. Consequently, this aspect of genetic diversity (or evolutionary potential) can be a key factor in the success of species invasions. Previous studies have compared the evolutionary potential of populations in introduced versus native ranges of invasive species, but to date no study has examined differences among introduced-range populations of such species in levels of quantitative genetic variation expressed in ecologically relevant environments. We assessed quantitative variation of fitness, life-history, and functional traits in six geographically separate introduced-range populations of the invasive annual Polygonum cespitosum, by comparing norms of reaction for a large sample of genotypes (16–19 per population) expressed in response to two glasshouse environments simulating contrasting habitats in this new range. Patterns of reaction norm diversity varied considerably among the 6 populations studied. Two populations showed very little quantitative genetic variation in both environments. In contrast, two other populations contained significant genetic variation for fitness and life-history traits in the form of genotypes with low performance in both habitats. Finally, two populations showed significant norm of reaction diversity in the form of cross-over interaction: genotypes that performed relatively well in one environment did poorly in the other. Differences among populations in potential selective response are likely to affect the dynamics and future spread of P. cespitosum, since specific populations will likely contribute differently to the invasion process. More generally, our results suggest that the evolutionary component of long-term invasion success may depend on population rather than on species-level processes.

Background and aims Plant-soil interactions are a crucial component of ecosystem functioning. However, most global change studies focus on plant communities, with information on soil properties and performance being scarce. Our goal was to assess the individual and joint effect of habitat heterogeneity and three global change drivers (fragmentation, loss of habitat quality and climate change) on nutrient availability and soil microbial activity in Mediterranean gypsum soils.