Showing papers by "Martin Zobel published in 2021"

Temperature and pH define the realised niche space of arbuscular mycorrhizal fungi

Abstract: The arbuscular mycorrhizal (AM) fungi are a globally distributed group of soil organisms that play critical roles in ecosystem function. However, the ecological niches of individual AM fungal taxa are poorly understood. We collected > 300 soil samples from natural ecosystems worldwide and modelled the realised niches of AM fungal virtual taxa (VT; approximately species‐level phylogroups). We found that environmental and spatial variables jointly explained VT distribution worldwide, with temperature and pH being the most important abiotic drivers, and spatial effects generally occurring at local to regional scales. While dispersal limitation could explain some variation in VT distribution, VT relative abundance was almost exclusively driven by environmental variables. Several environmental and spatial effects on VT distribution and relative abundance were correlated with phylogeny, indicating that closely related VT exhibit similar niche optima and widths. Major clades within the Glomeraceae exhibited distinct niche optima, Acaulosporaceae generally had niche optima in low pH and low temperature conditions, and Gigasporaceae generally had niche optima in high precipitation conditions. Identification of the realised niche space occupied by individual and phylogenetic groups of soil microbial taxa provides a basis for building detailed hypotheses about how soil communities respond to gradients and manipulation in ecosystems worldwide.

Fine-root traits in the global spectrum of plant form and function.

Abstract: Plant traits determine how individual plants cope with heterogeneous environments. Despite large variability in individual traits, trait coordination and trade-offs1,2 result in some trait combinations being much more widespread than others, as revealed in the global spectrum of plant form and function (GSPFF3) and the root economics space (RES4) for aboveground and fine-root traits, respectively. Here we combine the traits that define both functional spaces. Our analysis confirms the major trends of the GSPFF and shows that the RES captures additional information. The four dimensions needed to explain the non-redundant information in the dataset can be summarized in an aboveground and a fine-root plane, corresponding to the GSPFF and the RES, respectively. Both planes display high levels of species aggregation, but the differentiation among growth forms, families and biomes is lower on the fine-root plane, which does not include any size-related trait, than on the aboveground plane. As a result, many species with similar fine-root syndromes display contrasting aboveground traits. This highlights the importance of including belowground organs to the GSPFF when exploring the interplay between different natural selection pressures and whole-plant trait integration. The authors analyse the coordination and trade-off of the aboveground and fine-root traits of vascular plants using global trait databases.

sPlotOpen – An environmentally balanced, open-access, global dataset of vegetation plots

Abstract: Motivation. Assessing biodiversity status and trends in plant communities is critical for understanding, quantifying and predicting the effects of global change on ecosystems. Vegetation plots record the occurrence or abundance of all plant species co-occurring within delimited local areas. This allows species absences to be inferred, information seldom provided by existing global plant datasets. Although many vegetation plots have been recorded, most are not available to the global research community. A recent initiative, called ‘sPlot’, compiled the first global vegetation plot database, and continues to grow and curate it. The sPlot database, however, is extremely unbalanced spatially and environmentally, and is not open-access. Here, we address both these issues by (a) resampling the vegetation plots using several environmental variables as sampling strata and (b) securing permission from data holders of 105 local-to-regional datasets to openly release data. We thus present sPlotOpen, the largest open-access dataset of vegetation plots ever released. sPlotOpen can be used to explore global diversity at the plant community level, as ground truth data in remote sensing applications, or as a baseline for biodiversity monitoring. Main types of variable contained. Vegetation plots (n = 95,104) recording cover or abundance of naturally co-occurring vascular plant species within delimited areas. sPlotOpen contains three partially overlapping resampled datasets (c. 50,000 plots each), to be used as replicates in global analyses. Besides geographical location, date, plot size, biome, elevation, slope, aspect, vegetation type, naturalness, coverage of various vegetation layers, and source dataset, plot-level data also include community-weighted means and variances of 18 plant functional traits from the TRY Plant Trait Database. Spatial location and grain. Global, 0.01–40,000 m². Time period and grain. 1888–2015, recording dates. Major taxa and level of measurement. 42,677 vascular plant taxa, plot-level records. Software format. Three main matrices (.csv), relationally linked.

Global macroecology of nitrogen‐fixing plants

Abstract: AIM: Plants that host root‐symbiotic nitrogen‐fixing bacteria have an important role in driving terrestrial ecosystem processes, but N‐fixing ability is unequally distributed among plant taxa and ecosystems. Here we explore the large‐scale distribution of N‐fixing plant species worldwide. LOCATION: Global. TIME PERIOD: Present. MAJOR TAXA STUDIED: Vascular plants. METHODS: We estimated root‐symbiotic N‐fixing plant species diversity (as Shannon entropy) and relative richness (log‐ratio of N‐fixing to non‐fixing plant species) for c. 7,800 km² hexagonal grid cells using the NodDB and Global Biodiversity Information Facility (GBIF) databases. Additionally, we explored the distributions of plant species associated with rhizobia, actinobacteria or cyanobacteria (relative to other plant species), and the relative richness of N‐fixing trees (log‐ratio of N‐fixing to non‐fixing trees). We related N‐fixing plant species distribution to environmental (climate, soil) and biogeographical (biome, realm) variables using multiple linear regression. RESULTS: N‐fixing plant diversity and relative richness showed unimodal relationships with latitude. Diversity of N‐fixing plants was highest in warm and wet climates, but in dry biomes and in Australasia. The relative richness of N‐fixing plants was highest in warm and dry climates, in tropical and temperate grasslands and in Eurasia. Plants associated with cyanobacteria were more widely distributed near the equator, while those associated with rhizobia were more prevalent at the edge of the tropics, and those associated with actinobacteria at higher latitudes (especially in boreal forests). The relative richness of N‐fixing tree species was highest in cold and dry areas and in boreal forests, with contrasting peaks in the Northern and Southern Hemispheres. MAIN CONCLUSIONS: The distribution of N‐fixing plant species exhibits regional hotspots and coldspots related to both environmental conditions and biogeographical history. Global N‐fixing plant distributions are different for the key root‐symbiotic bacterial groups. Information about N‐fixing plant distribution can improve global models of ecosystem functions and contribute to understanding how plants respond to global change.

Light availability and light demand of plants shape the arbuscular mycorrhizal fungal communities in their roots

Abstract: Plants involved in the arbuscular mycorrhizal (AM) symbiosis trade photosynthetically derived carbon for fungal-provided soil nutrients. However, little is known about how plant light demand and ambient light conditions influence root-associating AM fungal communities. We conducted a manipulative field experiment to test whether plants' shade-tolerance influences their root AM fungal communities in open and shaded grassland sites. We found similar light-dependent shifts in AM fungal community structure for experimental bait plant roots and the surrounding soil. Yet, deviation from the surrounding soil towards lower AM fungal beta-diversity in the roots of shade-intolerant plants in shade suggested preferential carbon allocation to specific AM fungi in conditions where plant-assimilated carbon available to fungi was limited. We conclude that favourable environmental conditions widen the plant biotic niche, as demonstrated here with optimal light availability reducing plants' selectivity for specific AM fungi, and promote compatibility with a larger number of AM fungal taxa.

Woody encroachment in grassland elicits complex changes in the functional structure of above- and belowground biota

Abstract: This research was supported by the University of Tartu (PLTOM20903) and the European Regional Development Fund (Centre of Excellence EcolChange).

Arbuscular Mycorrhizal Fungal Communities in the Soils of Desert Habitats.

Abstract: Deserts cover a significant proportion of the Earth’s surface and continue to expand as a consequence of climate change. Mutualistic arbuscular mycorrhizal (AM) fungi are functionally important plant root symbionts, and may be particularly important in drought stressed systems such as deserts. Here we provide a first molecular characterization of the AM fungi occurring in several desert ecosystems worldwide. We sequenced AM fungal DNA from soil samples collected from deserts in six different regions of the globe using the primer pair WANDA-AML2 with Illumina MiSeq. We recorded altogether 50 AM fungal phylotypes. Glomeraceae was the most common family, while Claroideoglomeraceae, Diversisporaceae and Acaulosporaceae were represented with lower frequency and abundance. The most diverse site, with 35 virtual taxa (VT), was in the Israeli Negev desert. Sites representing harsh conditions yielded relatively few reads and low richness estimates, for example, a Saudi Arabian desert site where only three Diversispora VT were recorded. The AM fungal taxa recorded in the desert soils are mostly geographically and ecologically widespread. However, in four sites out of six, communities comprised more desert-affiliated taxa (according to the MaarjAM database) than expected at random. AM fungal VT present in samples were phylogenetically clustered compared with the global taxon pool, suggesting that nonrandom assembly processes, notably habitat filtering, may have shaped desert fungal assemblages.

Distribution of plant mycorrhizal traits along an elevational gradient does not fully mirror the latitudinal gradient

Abstract: The influence of mycorrhizal symbiosis on ecosystem processes depends on the mycorrhizal type and status of plants. Early research hypothesized that the proportion of arbuscular mycorrhizal (AM) species decreases and of ectomycorrhizal (ECM) and ericoid mycorrhizal (ERM) species increases along increasing elevations and latitudes. However, there is very scarce information about this pattern along elevation gradients. We aimed to test this hypothesis and to describe the trends in plant mycorrhizal status by examining the Pyrenean mountain range (from 400 to 3400 m asl). The distribution of plant mycorrhizal types: AM, ECM, ERM, and non-mycorrhizal (NM) and status (obligately, OM, or facultatively, FM mycorrhizal plants, FM) were identified based on the Pyrenean Floristic Atlas and analyzed for climatic and edaphic drivers. The proportion of AM plants decreased slightly with elevation, while ECM species peaked at 1000 m asl. The proportion of ERM and NM plant species rose with increasing elevation. The proportion of FM species increased, and OM species decreased with increasing elevation. The change of AM and ECM species, and OM and FM species, along the elevational gradient, corresponds broadly to changes along the latitudinal gradient, driven by a combination of climatic and edaphic factors. Differently, the elevational occurrence of NM plant species is mainly driven only by climatic factors (low temperature) and that of ERM species by only edaphic factors (low pH). Large-scale macroecological studies (≥ 50 km grid cell) well reflect the effects of climate on the distribution of plant mycorrhizal traits, but local data (≤ 1 km grid cell) are needed to understand the effects of soil conditions and land use.

Diversity of arbuscular mycorrhizal fungi and its chemical drivers across dryland habitats

Abstract: Qatar is largely characterized by a hyper-arid climate and low soil fertility which create a stressful soil environment for arbuscular mycorrhizal (AM) fungi. In a study of AM fungal communities and their relationship with soil chemical characteristics, we used a high-throughput sequencing technique to explore AM fungal diversity and community composition in different habitats across Qatar. We identified a total of 79 AM fungal taxa, over 77% of which were species from the Glomeraceae family. The lowest AM fungal diversity was observed in saltmarsh and in one rawdha site, while the highest richness, effective number of species, and diversity were observed in rawdha and sabkha communities. NMDS and multiple regression analyses showed that AM fungi were negatively correlated with soil pH and TC, but positively correlated with K and NO3-. AM fungi also were positively correlated with Cd, with the latter suggesting that very low levels of heavy metals may not always be harmful to AM fungi. These findings provide baseline information on AM fungal assemblages and the chemical drivers of diversity across communities in Qatar. This work partly compensates for the current lack of broad-scale studies in the Arabian Peninsula by providing understanding of overall patterns of AM fungi and their drivers in the region.

The role of genetic diversity and arbuscular mycorrhizal fungal diversity in population recovery of the semi-natural grassland plant species Succisa pratensis.

Abstract: Background Ecosystem restoration is as a critical tool to counteract the decline of biodiversity and recover vital ecosystem services. Restoration efforts, however, often fall short of meeting their goals. Although functionally important levels of biodiversity can significantly contribute to the outcome of ecosystem restoration, they are often overlooked. One such important facet of biodiversity is within-species genetic diversity, which is fundamental to population fitness and adaptation to environmental change. Also the diversity of arbuscular mycorrhizal fungi (AMF), obligate root symbionts that regulate nutrient and carbon cycles, potentially plays a vital role in mediating ecosystem restoration outcome. In this study, we investigated the relative contribution of intraspecific population genetic diversity, AMF diversity, and their interaction, to population recovery of Succisa pratensis, a key species of nutrient poor semi natural grasslands. We genotyped 180 individuals from 12 populations of S. pratensis and characterized AMF composition in their roots, using microsatellite markers and next generation amplicon sequencing, respectively. We also investigated whether the genetic makeup of the host plant species can structure the composition of root-inhabiting AMF communities. Results Our analysis revealed that population allelic richness was strongly positively correlated to relative population growth, whereas AMF richness and its interaction with population genetic diversity did not significantly contribute. The variation partitioning analysis showed that, after accounting for soil and spatial variables, the plant genetic makeup explained a small but significant part of the unique variation in AMF communities. Conclusions Our results confirm that population genetic diversity can contribute to population recovery, highlighting the importance of within-species genetic diversity for the success of restoration. We could not find evidence, however, that population recovery benefits from the presence of more diverse AMF communities. Our analysis also showed that the genetic makeup of the host plant structured root-inhabiting AMF communities, suggesting that the plant genetic makeup may be linked to genes that control symbiosis development.

LOTVS: a global collection of permanent vegetation plots

Abstract: Analysing temporal patterns in plant communities is extremely important to quantify the extent and the consequences of ecological changes, especially considering the current biodiversity crisis. Long-term data collected through the regular sampling of permanent plots represent the most accurate resource to study ecological succession, analyse the stability of a community over time and understand the mechanisms driving vegetation change. We hereby present the LOng-Term Vegetation Sampling (LOTVS) initiative, a global collection of vegetation time-series derived from the regular monitoring of vascular plants in permanent plots. With 79 datasets from five continents and 7789 vegetation time-series monitored for at least six years and mostly on an annual basis, LOTVS possibly represents the largest collection of temporally fine-grained vegetation time-series derived from permanent plots and made accessible to the research community. As such, it has an outstanding potential to support innovative research in the fields of vegetation science, plant ecology and temporal ecology.

Arbuscular mycorrhizal fungi promote small-scale vegetation recovery in the forest understorey.

Abstract: Root-associating arbuscular mycorrhizal (AM) fungi foster vegetation recovery in degraded habitats. AM fungi increase nutrient availability for host plants; therefore, their importance is expected to be higher when nutrient availability is low. However, little is known about how small-scale variation in nutrient availability influences plant and AM fungal communities in a stable ecosystem. We conducted a 2-year field study in the understorey of a boreonemoral forest where we examined plant and AM fungal communities at microsites (15 cm diameter) with intact vegetation cover and at disturbed microsites where vegetation was cleared away and soil was sterilized to remove soil biota. We manipulated soil nutrient content (increased with fertilizer, unchanged, or decreased with sucrose addition) and fungal activity (natural or suppressed by fungicide addition) at these microsites. After two vegetation seasons, manipulations with nutrient content resulted in significant, although moderate, differences in the content of soil nutrients (e.g. in soil phosphorus). Suppression of fungal activity resulted in lower richness, abundance and phylogenetic diversity of AM fungal community, independently of microsite type and soil fertility level. Plant species richness and diversity decreased when fungal activity was suppressed at disturbed but not in intact microsites. The correlation between plant and AM fungal communities was not influenced by microsite type or soil fertility. We conclude that small-scale variation in soil fertility and habitat integrity does not influence the interactions between plants and AM fungi. The richness, but not composition, of AM fungal communities recovered fast after small-scale disturbance and supported the recovery of species-rich vegetation.