Assembly history modulates vertical root distribution in a grassland experiment

Abstract

The order of arrival of plant species during assembly can affect the structure and functioning of grassland communities. These so-called priority effects have been extensively studied aboveground, but we still do not know how they affect the vertical distribution of roots in the soil and the rooting depth of plant communities. To test this hypothesis, we manipulated the order of arrival of three plant functional groups (forbs, grasses and legumes) in a rhizobox experiment. Priority effects were created by sowing one functional group 10 days before the other two. Rhizoboxes in which all functional groups were sown simultaneously were used as controls. During the experiment, the mean rooting depth of plant communities was monitored using image analysis and a new methodological approach using deep learning (RootPainter) for root segmentation. At harvest, we measured aboveground (community and species level) and belowground (community level) biomass, and assessed the vertical distribution of the root biomass in different soil layers. At the community level, all scenarios where one functional group was sown before the other two had similar shoot and root productivity. At the species level, two forbs (Achillea millefolium and Centaurea jacea) benefited from arriving early, and one legume (Trifolium pratense) had a disadvantage when it was sown after the grasses. Priority effect treatments also affected the vertical distribution of roots. When grasses were sown first, plant communities rooted more shallowly than when forbs or legumes were sown first,. In addition, roots moved down the soil profile 24% more slowly in grasses-first communities. Our results highlight that plant functional group order of arrival in grassland communities can affect the vertical distribution of roots in the soil and this may have implications for species coexistence.

Assembly history modulates vertical root distribution in a grassland experiment

“…no difference in productivity or total visible root length) are represented by dashed black lines. Effect sizes and compatibility intervals can be found in the HTML version of our R markdown file on Zenodo (Alonso‐Crespo et al 2021). Sync1, all PFGs sown at the same time at the first sowing event; F‐first, forbs sown 10 days before grasses and legumes; G‐first, grasses sown 10 days before forbs and legumes; L‐first, legumes sown 10 days before forbs and grasses; Sync2, all PFGs sown at the same time at the second sowing event.…”

“…Data are available from the Zenodo Digital Repository: <https://doi.org/10.5281/zenodo.5713397> (Alonso‐Crespo et al 2021).…”

Special Issue: Root traits and functioning: from individual plants to ecosystems

“…Reference in this Special Issue Temperate Alonso-Crespo et al 2023, Klimešová and Herben 2023, Mafa-Attoye et al 2023, Mao et al 2023, Schuster et al 2023, Slette et al 2023, Yang et al 2023(Sub)Tropical Dallstream et al 2023, Dai et al 2023,Gagliardi et al 2023, Guo et al 2023, Leroy et al 2023, Kotowska et al 2023 a large variety of fine-root systems coexist in hyper-diverse tropical plant communities. Besides adding information from underexplored biomes, this Special Issue further highlights the importance of incorporating additional traits covering all belowground trait categories (McCormack et al 2017) -albeit to different extents -in the context of a RES (Table 1).…”

High frequency root dynamics: sampling and interpretation using replicated robotic minirhizotrons

“…A manual approach will inevitably not annotate images as fast as collection. Recently, convolutional neural networks (CNNs) show promising results to identify roots in a variety of settings ( Rahmanzadeh and Shojaedini, 2016 ; Vincent et al , 2017 ; Huo and Cheng, 2019 ; Alonso-Crespo et al , 2022 ; Bauer et al , 2022 ). In particular, field soil minirhizotron imagery has been analysed several times ( Wang et al , 2019 ; Gillert et al , 2021 ; Han et al , 2021 ; Bauer et al , 2022 ; Peters et al , 2022 , Preprint; Smith et al , 2022 ), but transferability between sites and out of agricultural soils is difficult to assess without widespread adoption in new settings.…”