Seed mass predicts migration lag of European trees

International audienceAbstractKey messageWe reanalysed a dataset of tree distribution ranges in Europe to identify which plant traits best explain migration potential in woody species. Contrary to our intuition that tree longevity would best explain the ability of trees to migrate, we found that seed biomass was the only good descriptor of migration potential: trees with heavier seeds lag more.ContextTo cope with global warming, the majority of plants have either to migrate polewards or risk extinction. This is why conservationists value predictive models that can flag plant species that may not keep pace with global warming.AimsTo identify which plant traits best explain migration potential in woody species by reanalysing a dataset of tree distribution ranges in Europe.MethodsWe used two statistical approaches to quantify migration lag. A direct approach compared frequency of large trees in the two latitudinal extremes and a modelling approach in which we first corrected data for the influence of temperature and then assessed the influence of latitude over the entire distribution of the tree species.ResultsContrary to our intuition that tree longevity would best explain the ability of trees to migrate, we found that seed mass was the only good descriptor of migration potential: trees with heavier seeds lag more.ConclusionWe interpret our results in terms of the well-established trade-off between seed mass and seed production in spermatophytes and discuss the possible functional implications that will result from selectively losing large-seeded trees. In summary, we provide an empirical study on how woody communities will respond to global warming over the next years

Extinction risk of soil biota

No species lives on earth forever. Knowing when and why species go extinct is crucial for a complete understanding of the consequences of anthropogenic activity, and its impact on ecosystem functioning. Even though soil biota play a key role in maintaining the functioning of ecosystems, the vast majority of existing studies focus on aboveground organisms. Many questions about the fate of belowground organisms remain open, so the combined effort of theorists and applied ecologists is needed in the ongoing development of soil extinction ecology

Arbuscular mycorrhizal root colonization depends on the spatial distribution of the host plants

Despite their ubiquity in terrestrial ecosystems, arbuscular mycorrhizal fungi (AMF) experience dispersion constraints and thus depend on the spatial distribution of the plant hosts. Our understanding of fungal-plant interactions with respect to their spatial distributions and implications for the functioning of the symbiosis remain limited. We here manipulated the location of habitat patches of Medicago lupulina in two experiments to explore the responses of AMF root colonization and extraradical hyphae. We tested the specific hypothesis that AMF-plant habitats high in connectance would stimulate root colonization and induce denser functional root colonization (colonization rate of arbuscules plus coils) because of higher propagule availability between nearby host plant patches (experiment 1). In experiment 2, we anticipated similar responses in mixed habitats of different soil fertility, namely phosphorus-fertilized or unfertilized soil, and anticipated a higher density of extraradical hyphae in the soil connecting the habitats with increased functional root colonization. In agreement with our hypothesis, we found the highest total and functional root colonization in unfragmented micro-landscapes, describing landscapes that occur within a spatial scale of a few centimeters with the AMF-plant habitats positioned adjacent to each other. In the second experiment, overdispersed micro-landscapes promoted functional root colonization. This study provides experimental evidence that the spatial distribution of habitats can determine AMF abundance at the microscale

Soil biodiversity enhances the persistence of legumes under climate change

Summary: Global environmental change poses threats to plant and soil biodiversity. Yet, whether soil biodiversity loss can further influence plant community’s response to global change is still poorly understood. We created a gradient of soil biodiversity using the dilution‐to‐extinction approach, and investigated the effects of soil biodiversity loss on plant communities during and following manipulations simulating global change disturbances in experimental grassland microcosms. Grass and herb biomass was decreased by drought and promoted by nitrogen deposition, and a fast recovery was observed following disturbances, independently of soil biodiversity loss. Warming promoted herb biomass during and following disturbance only when soil biodiversity was not reduced. However, legumes biomass was suppressed by these disturbances, and there were more detrimental effects with reduced soil biodiversity. Moreover, soil biodiversity loss suppressed the recovery of legumes following these disturbances. Similar patterns were found for the response of plant diversity. The changes in legumes might be partly attributed to the loss of mycorrhizal soil mutualists. Our study shows that soil biodiversity is crucial for legume persistence and plant diversity maintenance when faced with environmental change, highlighting the importance of soil biodiversity as a potential buffering mechanism for plant diversity and community composition in grasslands

Neighbours of arbuscular‐mycorrhiza associating trees are colonized more extensively by arbuscular mycorrhizal fungi than their conspecifics in ectomycorrhiza dominated stands

Arbuscular mycorrhiza represents a ubiquitous nutritional symbiosis between the roots of most terrestrial plant species and fungi of the subphylum Glomeromycotina (Spatafora et al., 2016). Terrestrial habitats are unlikely to be limited in propagules of arbuscular mycorrhizal fungi (AMF), because AMF propagule densities build up fast in vegetated soil (e.g. Gould et al., 1996). We start to appreciate, however, that shortages in AMF propagules are common in some habitats, such as agricultural fields subject to intensive farming (Schnoor et al., 2011; Manoharan et al., 2017). Forest habitats in the temperate region might also be occasionally AMF propagule limited (Veresoglou et al., 2017), but to the best of our understanding this has not been shown with empirical data

Excluding arbuscular mycorrhiza lowers variability in soil respiration but slows down recovery from perturbations

The role of mutualisms in mediating temporal stability in an ecosystem has been debated extensively. Here, we focus on how a ubiquitous mutualism, arbuscular mycorrhiza, influences temporal stability of a key ecosystem process, ecosystem respiration. We discriminated between two forms of temporal stability, temporal variability and resilience, and hypothesized that excluding arbuscular mycorrhiza would be detrimental for both of them. We analyzed a set of 10 parallel manipulation experiments to assess how excluding arbuscular mycorrhiza modulates temporal stability compared to other common experimental factors. We quantified the temporal variability of ecosystem respiration and the resilience to experimental perturbations (i.e., pulses, stresses, and a disturbance) following manipulations of mycorrhizal state. We observed lower temporal variability in the absence of arbuscular mycorrhiza in discord to our main hypothesis. Manipulating arbuscular mycorrhiza had a stronger impact on temporal variability than the pulse (application of urea), the stress (addition of salt), and a disturbance (experimental defoliation) but weaker than excluding primary producers or comparing across different plant species. Resilience to experimental perturbations declined in non‐mycorrhizal microcosms. We present an empirical study on how mutualisms impact temporal stability. Arbuscular mycorrhiza differentially alters temporal variability and resilience, highlighting that generalizing across different forms of temporal stability could be misleading

Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity

Elevated tropospheric ozone concentrations induce adverse effects in plants. We reviewed how ozone affects (i) the composition and diversity of plant communities by affecting key physiological traits; (ii) foliar chemistry and the emission of volatiles, thereby affecting plant-plant competition, plant-insect interactions, and the composition of insect communities; and (iii) plant-soil-microbe interactions and the composition of soil communities by disrupting plant litterfall and altering root exudation, soil enzymatic activities, decomposition, and nutrient cycling. The community composition of soil microbes is consequently changed, and alpha diversity is often reduced. The effects depend on the environment and vary across space and time. We suggest that Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan have high endemic richness at high ozone risk by 2100