Belowground Species Richness Research Articles

Metabarcoding inventory of an arctic tundra soil ecosystem reveals highly heterogeneous communities at a small scale

Biodiversity surveys of Arctic soil ecosystems are limited. Here, we provide a sequence-based inventory of soil fauna from an Arctic tundra ecosystem near the Canadian High Arctic Research Station in Cambridge Bay, Nunavut. Invertebrate communities were extracted at a vegetated and non-vegetated site in three replicates and inventoried using 18S metabarcode sequencing. A total of 361 amplicon sequence variants (ASV) were identified and assigned to the closest matching taxonomic orders, most of which belonged to the Nematoda and Arthropoda. Vegetated soils showed no significantly higher ASV richness relative to non-vegetated soils although they contained a significantly higher diversity of arthropod taxa including insects, mites, and springtails. Most taxa were found only at a single location and even samples from the same site displayed distinct communities, suggesting that belowground species richness in Arctic tundra habitats is highly heterogeneous. Preserving soil biodiversity in a changing Arctic is essential for Inuit communities who rely on intact tundra ecosystems for their health and wellbeing.

Above- and below-ground species richness of bryophytes in Estonian mires: diversity and differences

ABSTRACT Introduction. In temperate zones, the main peat-forming plants are bryophytes, and the restoration capacity of disturbed peatland depends largely on the availability of suitable bryophyte diaspores. We investigated the species richness of bryophytes in the above-ground flora and diaspore bank of three types of mire common in Estonia and northern Europe: ombrotrophic bogs, poor fen and rich fen. Methods. The above-ground flora was recorded and diaspore bank samples were collected from study sites in eastern Estonia representing bog, poor fen and rich fen (three sites per mire type). For each mire type, the diaspore bank samples from the study sites were blended and placed in a growth chamber for 6 months, and the bryophytes that subsequently emerged were identified. Key results. In total, 54 bryophyte species were found, including six liverworts. Of the three mire types, rich fen had the most species both above and below ground. The number of species in the diaspore bank was lowest in bog (8) and highest in rich fen (27). Three species with conservation value were found: Hamatocaulis vernicosus (in the above-ground flora only) and Meesia longiseta and Splachnum ampullaceum (in the diaspore bank only). The species richness of the bryophyte diaspore bank was similar and significantly related to that of the above-ground bryophyte flora. Conclusion. In temperate-zone mires, the diaspore bank can be a depository of species that have disappeared from the above-ground flora. The local diaspore bank could a valuable source of species richness for the restoration of disturbed mire communities.

Earthworms modulate the effects of climate warming on the taxon richness of soil meso- and macrofauna in an agricultural system

Anthropogenic climate change is altering the functioning of terrestrial ecosystems. Agricultural systems are particularly vulnerable to climate change as they are frequently disturbed by intensified management practices. This also threatens belowground organisms that are responsible for providing crucial ecosystem functions and services, such as nutrient cycling and plant disease suppression. Amongst these organisms, earthworms are of particular importance as they can modulate the effects of climate change on soil organisms by modifying the biotic and abiotic soil conditions. However, they are also known to decline under intensified management, justifying their use as key biotic indicators of intensified agriculture. Yet, our knowledge of the responses of belowground species to the interacting effects of warming and land-use intensification (simulated by earthworm reduction in the experimental setup) remains limited. Here, we tested the interactive effects of soil warming and reduced earthworm densities on soil protists, nematodes, meso- and macrofauna, and their diversity in a common barley system in the Hohenheim Climate Change Experiment. We found that belowground species richness was lowest at elevated temperature and reduced earthworm densities, indicating that earthworms can buffer warming effects on belowground biodiversity. Furthermore, warming increased the densities of plant-feeding nematodes, and herbivorous macrofauna benefitted from reduced earthworm densities. Our results indicate that warming and reduced earthworm densities may simultaneously modify the functioning and service provisioning of soils via shifts in diversity and density of soil biota that would likely lead to simplified belowground food webs. These findings thus highlight the importance of maintaining greater densities of ecosystem engineers like earthworms that may help buffering the detrimental effects of climate warming in agricultural systems.

A high-throughput belowground plant diversity assay using next-generation sequencing of the trnL intron

We refine and test a next-generation sequencing assay for the molecular identification and quantification of plant roots from mixed-species samples. We modified primers targeting the trnL intron to provide greater taxonomic resolution and developed an improved bioinformatics pipeline that can identify roots based on global, site-, and plot-specific taxon lists. We tested our primers and pipeline on mock plant communities of known composition and mixed-species samples of roots collected from temperate grassland and high Arctic tundra communities. We retrieved a high correlation (0.72) between observed and expected community dissimilarities. We found positive linear relationships between aboveground and belowground species richness in the grassland community, with higher correlations for plot-specific reference databases (R = 0.70) than a global reference database (R = 0.48). This highlights the importance of local reference databases within the bioinformatics pipeline. Lower root than aboveground richness suggests that typical root lateral spread in this grassland is less than 25 cm. We observed lateral rooting extents of up to 40 cm and rooting depths of up to 30 cm for six high Arctic species. Testing on mock community, grassland, and tundra samples demonstrated that next-generation sequencing using our improved trnL primers and pipeline can successfully recover plant root community structure.