Land colonization by plants and their fungal and bacterial symbionts during the Paleozoic was fundamental to the evolution of terrestrial ecosystems, but how these early communities influenced mineral weathering and soil development remains largely unknown. We investigated cryptogamic ground covers (CGCs) in Iceland to identify modern analogous communities and to characterize soil structure and biologically mediated weathering features. Using a novel application of X-ray microcomputed tomography, we show that moss-dominated CGCs and their soils are not adequate analogues of early communities. Comparisons with the 407 Ma Rhynie Chert (Scotland) biota indicate that modern CGCs dominated by lichens, liverworts, and their associated symbionts (fungi, cyanobacteria) are more representative of early soil-forming communities. Liverwort and lichen soils are thin, and their depth and complexity are constrained by the size and growth form of the dominant plants or lichens. They are aggregated and stabilized by cyanobacteria, mycorrhizal and lichenized fungi, rhizoids, and associated exudates. Smectite was associated with liverwort but not with moss CGC soils. Soil grain dissolution features are diverse and attributable to different organisms (e.g., bacteria, fungi) and types of interaction (e.g., symbiosis). We postulate that such features provide a novel indirect means of inferring biotic interactions in paleosols.

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The mechanics of breathing is a fascinating and vital process. The lung has complexities and subtle heterogeneities in structure across length scales that influence mechanics and function. This study establishes an experimental pipeline for capturing alveolar deformations during a respiratory cycle using synchrotron radiation micro-computed tomography (SR-micro-CT). Rodent lungs were mechanically ventilated and imaged at various time points during the respiratory cycle. Pressure-Volume (P-V) characteristics were recorded to capture any changes in overall lung mechanical behaviour during the experiment. A sequence of tomograms was collected from the lungs within the intact thoracic cavity. Digital volume correlation (DVC) was used to compute the three-dimensional strain field at the alveolar level from the time sequence of reconstructed tomograms. Regional differences in ventilation were highlighted during the respiratory cycle, relating the local strains within the lung tissue to the global ventilation measurements. Strains locally reached approximately 150% compared to the averaged regional deformations of approximately 80–100%. Redistribution of air within the lungs was observed during cycling. Regions which were relatively poorly ventilated (low deformations compared to its neighbouring region) were deforming more uniformly at later stages of the experiment (consistent with its neighbouring region). Such heterogenous phenomena are common in everyday breathing. In pathological lungs, some of these non-uniformities in deformation behaviour can become exaggerated, leading to poor function or further damage. The technique presented can help characterize the multiscale biomechanical nature of a given pathology to improve patient management strategies, considering both the local and global lung mechanics.

Specific micro-weathering features and biochemically-derived residues formed by living organisms can be used as biomarkers to infer the presence of biological communities within sedimentary units of ancient ecosystems. We examined basaltic soil minerals from modern cryptogamic ground covers (CGCs) in Iceland and compared these to two lower Palaeozoic fossil systems. Nine biologically-mediated weathering features (BWFs) were identified in modern soils including micron-scale surface trenching and penetrative tunnels, which are attributed to the actions of bacteria, fungi, and exudates. Specific BWFs are associated with Fe residues, and with Fe-rich bio-precipitated nodules. Further, putative comparable features