Terrestrial surface stabilisation by modern analogues of the earliest land plants: A multi‐dimensional imaging study

• Main Authors: Mitchell, Ria L, Kenrick, Paul, Pressel, Silvia, Duckett, Jeff, Strullu‐Derrien, Christine, Davies, Neil, McMahon, William J, Summerfield, Rebecca
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: ORIGINAL ARTICLE; ORIGINAL ARTICLES; bryophytes; cryptogamic ground covers; Palaeoenvironments; plant evolution; sediment stabilisation; soil; X‐ray computed tomography; Anchorage; New Zealand; Iceland
• Online Access: https://www.repository.cam.ac.uk/handle/1810/346433; https://doi.org/10.17863/CAM.93854

Funder: Natural History Museum Origins and Evolution Initiative <jats:title>Abstract</jats:title><jats:p>The evolution of the first plant‐based terrestrial ecosystems in the early Palaeozoic had a profound effect on the development of soils, the architecture of sedimentary systems, and shifts in global biogeochemical cycles. In part, this was due to the evolution of complex below‐ground (root‐like) anchorage systems in plants, which expanded and promoted plant–mineral interactions, weathering, and resulting surface sediment stabilisation. However, little is understood about how these micro‐scale processes occurred, because of a lack of in situ plant fossils in sedimentary rocks/palaeosols that exhibit these interactions. Some modern plants (e.g., liverworts, mosses, lycophytes) share key features with the earliest land plants; these include uni‐ or multicellular rhizoid‐like anchorage systems or simple roots, and the ability to develop below‐ground networks through prostrate axes, and intimate associations with fungi, making them suitable analogues. Here, we investigated cryptogamic ground covers in Iceland and New Zealand to better understand these interactions, and how they initiate the sediment stabilisation process. We employed multi‐dimensional and multi‐scale imaging, including scanning electron microscopy (SEM) and X‐ray Computed Tomography (μCT) of non‐vascular liverworts (Haplomitriopsida and complex thalloids) and mosses, with additional imaging of vascular lycopods. We find that plants interact with their substrate in multiple ways, including: (1) through the development of extensive surface coverings as mats; (2) entrapment of sediment grains within and between networks of rhizoids; (3) grain entwining and adherence by rhizoids, through mucilage secretions, biofilm‐like envelopment of thalli on surface grains; and (4) through grain entrapment within upright ‘leafy’ structures. Significantly, μCT imaging allows us to ascertain that rhizoids are the main method for entrapment and ...