Nick A. Cutler

Digital Elevation Models (DEMs) are essential in estimating soil erosion, yet the influence of DEM spatial resolution on model outputs remains uncertain, particularly at the scale of individual fields. This study investigates how raster cell size affects soil erosion estimates using a physical‐statistical soil erosion model (PSSEM) on a 2.8‐km ² agricultural area in Northern England. High‐resolution LiDAR‐derived DEMs (1 m) were resampled to 5‐, 10‐ and 30‐m resolutions to compare their influence on key topographic and erosion‐related metrics. The results show that as raster cell size increases, generally slopes become smoother, ephemeral stream lengths increase and active sediment formation zones shorten. The average soil loss estimates ranged from 0.99 t ha ⁻¹ year ⁻¹ (30 m) to 2.81 t ha ⁻¹ year ⁻¹ (5 m), demonstrating variations of nearly threefold across resolutions. Flow concentration coefficients and erosion distribution patterns were also affected, with finer resolutions better capturing local extremes of erosion and deposition. Statistical comparison of PSSEM runs using mean absolute deviation (MAD) and Euclidean distance (ED) showed, for example, that the MAD between 1‐ and 5‐m models reached 3.35 t ha ⁻¹ year ⁻¹ , indicating prominent changes, while further coarsening led to a general smoothing of results. Despite this, low‐resolution DEMs (e.g., 30 m) may provide a generalized basis for preliminary erosion risk assessment over larger areas but should be interpreted with caution. However, for detailed farm‐scale planning and the identification of erosion‐prone microzones, higher resolution models (≤ 5 m) are necessary. The findings indicate that DEM resolution should be chosen according to the objectives of erosion modelling: Coarser grids can be applied for preliminary evaluations, whereas high‐resolution data (≤ 5 m) are required to capture fine‐scale spatial variability and to support detailed planning of erosion control measures.

Sedimentary ancient DNA in well‐dated contexts ( sed aDNA) has great potential as a palaeoecological proxy. A few studies have attempted palaeoecological reconstructions using sed aDNA from soil; these studies have been mainly restricted to cold and/or dry soils. The study of soils from wet, temperate locations has been limited due to uncertainties surrounding the longevity and mobility of DNA in these environments. We addressed this knowledge gap with a novel field experiment that (i) tracked the movement and longevity of ‘exotic’ DNA applied to a wet, temperate soil and (ii) compared extant plant community structure with recent (decades old) environmental DNA (eDNA) data extracted from shallow (sed aDNA would be suitable as a palaeo‐proxy for vegetation in similar settings, albeit restricted to the most abundant taxa. Further work in more taxonomically and structurally diverse settings, preferably with different soil types, would be required to establish the broader use of soil sed aDNA as a palaeoecological proxy in wet, temperate soils.

Soil degradation driven by accelerated water erosion threatens global food security. Quantitative estimates of soil erosion losses allow at‐risk areas to be identified and the success of soil management plans to be monitored. However, estimating soil erosion losses under changing climatic conditions is challenging, particularly at the scales relevant to soil conservation schemes. We addressed this problem by studying soil erosion in Ukraine. The study was conducted at two spatial scales: (1) a large (regional) scale—to reveal the overall impact of climate change on soil erosion and (2) and a small (catchment) scale—to highlight spatial variability in soil losses. Our large‐scale study assessed the intensity of water erosion in Steppe and Forest‐Steppe zones (Chernozem zone) of Ukraine by calculating climate‐based hydrometeorological factors during modern (1991–2020) and baseline (1946–1990) periods. We assessed small‐scale variation soil losses using a mathematical model. Our results indicated minor (3%–5%) increases in soil loss due to climate changes, as increased erosion attributed to intense rainfall events was largely offset by reduced losses from snowmelt in Spring. In the small‐scale study, the upland location modelled soil loss was an average of 22.6 t ha ⁻¹ year ⁻¹ of soil, whilst the figure for the lowland location was 2.42 t ha ⁻¹ year ⁻¹ . Both sites included large areas vulnerable to soil degradation (57.8% and 38.6%, respectively). The comparatively small impact of climate change on soil erosion losses does not diminish the severity of the water erosion problem in Ukraine, as a significant portion of the territory may still be at high erosion risk.

Aridity alters soil carbon (C), nitrogen (N) and phosphorus (P) stoichiometry, yet the implications of these processes for soil microbial functional traits and potentials at the genomic level remain poorly synthesized. Here we combine measurements of soil C, N and P pools and ratios with shotgun metagenomes from 200 natural ecosystems spanning major biomes worldwide. Across sites, increased aridity is associated with lower soil C:N and N:P (and C:P) ratios and with a coordinated shift in microbial functional potential. Genes linked to catabolic resource acquisition—including carbohydrate-active enzymes and pathways for degradation of plant litter and organophosphorus compounds—are declined as C becomes relatively scarce. In contrast, genes supporting anabolic investment in growth and drought resistance, such as RNA transcription, protein synthesis and intracellular transport, are increased. These patterns indicate that aridity-related change in soil elemental ratios is coupled to a broad shift from catabolic to anabolic strategies in soil microbiomes. By linking soil elemental ratios to microbial functional traits across biomes, our study provides a framework for anticipating how climate-driven drying may reorganize microbial metabolism with consequences for carbon and nutrient cycling.

Microbes, as the planet's most abundant and diverse organisms, drive soil functions globally and are vulnerable to environmental stressors triggered by global change. Yet, knowledge regarding the impacts of multiple environmental stressors on their functional profiles as well as the consequences for soil functionality largely remains unknown. Here, we analyze two global-scale datasets including information on soil metagenomics and multiple environmental stressors. We find that across terrestrial ecosystems worldwide, up to 60% of all functional genes significantly shift when soil microbes experience the high-level of concurrent stressors. In this regard, the relative abundances of genes involved in microbial growth are negatively linked to the increasing number of stressors. Conversely, those genes linked to stress resistance and energy production exhibit positive responses. Taken together, our findings highlight a significant restructuring of global soil functional microbiomes in response to multiple environmental stressors. Consequently, such restructuring drives community-level shifts in matter and energy reallocations, thereby impacting the maintenance of soil functionality under the projected global change.

Soil erosion has been a persistent problem in high‐latitude regions and may worsen as climate change unfolds and encourages increased anthropogenic exploitation. We propose that soil moisture is likely to shape future erosion trends, as moisture stress reduces the capacity of vegetation cover to retard erosive processes. However, the spatial variability of soil moisture in high‐latitude soils—and the ways in which this variability drives the spatial distribution of erosion features—is poorly understood. We addressed this knowledge gap with a study of andosol erosion in southern Iceland. Our study used a combination of high‐resolution (10 m from eroded terrain. We found lower moisture availability close to existing erosion features: mean volumetric soil moisture content varied from 17% (proximal to erosion patch) to 36% (distal to erosion patch). We also found that variability in soil moisture decreased with distance from eroded areas: the coefficient of variation (CV) in soil moisture varied from 0.33 (proximal to erosion patch) to 0.13 (distal to erosion). Our findings indicate that the margins of erosion patches have a stressful soil environment due to exposure to the atmosphere. The vegetation in these locations grows less vigorously, and the exposed soil becomes more vulnerable to erosion, leading to erosion patch expansion and coalescence. If these conditions hold more generally, they may represent a feedback mechanism that facilitates the lateral propagation of soil erosion in high‐latitude regions.

Tephra layers are often used to reconstruct past eruptions. However, accurate interpretation of tephra layers depends on their degree of preservation. We asked: how much volcanological information do terrestrial tephra layers typically retain? We addressed this question with a study of the tephra layer produced by the May 1980 eruption of Mount St Helens, comparing historical records of deposit thickness and grain size distribution with measurements made four decades after the eruption. Using published isopach maps as a guide, we looked for the tephra layer in locations 15 – 600 km from Mount St Helens, selecting sample locations we judged to have high preservation potential. We found that preservation of the 1980 tephra deposit was often extremely good: observed thickness, mass loading and grain size distributions were similar to equivalent measurements made in 1980. However, we also observed high variability in preservation on small spatial scales, and our results indicate that landscape-scale volcanological reconstruction is sensitive to sample number and location, even when many sites display excellent preservation. Tephra preservation is clearly a complex and contingent process influenced by climate, biology, topography, parent material (i.e., grain size, morphology and geochemistry) and time. The relative importance of these factors will vary from place to place. We propose that the only way to tease apart these factors – and to fully understand the information content of tephra layers - is through direct observation of tephra deposits (whether natural or experimental) over extended time periods.

We explore the effect small‐scale surface features have on influencing the morphology and grain‐size distribution (GSD) of tephra layers within the Quaternary stratigraphy of sub‐polar landscapes. Icelandic thúfur, small cryogenic earth mounds, are used to assess how and why the morphology and GSD of tephra layers vary over such formations. Through measurement of tephra layer thickness and GSD, Hekla 1947 and Grímsvötn 2011 tephra layers are analysed. Results indicate that such microtopographic features do indeed alter the form of tephra deposits and therefore the tephra layer that is preserved in the stratigraphy. Tephra thickness is significantly greater in hollows than on the thúfur crests. There is greater variation in tephra thickness measurements from thúfur in comparison to control measurements from a surface where thúfur are absent. Thúfur crests contain larger grain sizes than hollows, for both H1947 and G2011 tephras; however this was only statistically significant for the G2011 tephra. Such morphological patterns are thought to arise from an interplay of tephra characteristics, altered topography from the thúfur formations and earth surface processes operating at the sites. This study provides insight into the potential of tephra layer morphology and internal structures as indicators of Quaternary landforms and processes. Additionally, it provides important context for the appropriate sampling of tephra layers to infer volcanological processes, as the characteristics of preserved layers do not necessarily reflect those of the original fall‐out.

Volcanologists frequently use grain size distributions (GSDs) in tephra layers to infer eruption parameters. However, for long-past eruptions, the accuracy of the reconstruction depends upon the correspondence between the initial tephra deposit and preserved tephra layer on which inferences are based. We ask: how closely does the GSD of a decades-old tephra layer resemble the deposit from which it originated? We addressed this question with a study of the tephra layer produced by the eruption of Mount St Helens, USA, in May 1980. We compared grain size distributions from the fresh, undisturbed tephra with grain size measurements from the surviving tephra layer. We found that the overall grain size characteristics of the tephra layer were similar to the original deposit, and that distinctive features identified by earlier authors had been preserved. However, detailed analysis of our samples showed qualitative differences, specifically a loss of fine material (which we attributed to ‘winnowing’). Understanding how tephra deposits are transformed over time is critical to efforts to reconstruct past eruptions, but inherently difficult to study. We propose long-term, tephra application experiments as a potential way forward.