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<jats:title>Abstract</jats:title><jats:p>Karst hillslopes are generally characterized by different land uses. Land use and slope position impact soil erosion seriously, which in turn impacts the process of soil development and the patterns of soil properties. However, the impact of land use on soil physicochemical properties and the spatial variations and correlations between them are not fully understood on karst hillslopes. Therefore, nine sites had similar soil types, slope gradients, elevations, slope aspects and previous tillage practices were selected to conduct further research. This study was conducted to quantify the spatial distribution, variability and correlation of soil physical and chemical properties and stoichiometries as impacted by different land uses on a karst hillslope in Southwest China. Soil physical properties were significantly affected by slope position and soil depth. The soil bulk density and clay content increased with soil depth, while the opposite was true for the sand content. For the three land uses, the soil bulk density varied the most at the lower slope position, while clay and sand particles varied the most at the middle slope position. The mean spatial coefficient of variation (CV) of soil physical properties was ranked as sand (11.08%) &gt; clay (7.77%) &gt; bulk density (6.85%) &gt; silt (3.81%). The mean spatial CV of soil chemical properties was ranked as available K (44.49%) &gt; total P (16.77%) &gt; total C (16.31%) &gt; total N (13.09%) &gt; available P (8.45%) &gt; total K (7.51%). Overall, soil physicochemical properties exhibited significant spatial differences with slope location and land use on karst hillslopes. Soil chemical properties had greater spatial variation than physical properties, moreover, there were significant correlations between them. The results not only contribute to a deeper understanding of the impact of land use on the erosion process and mechanism on karst hillslopes but also provide a scientific understanding of the sustainable restoration of karst ecosystems.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Geophysical and morphosedimentary investigations were conducted at Strathcona Lake, a High Arctic proglacial lake and its catchment connected to the Taggart Lake Glacier, northwest corner of the Prince of Wales Icefield in Ellesmere Island (eastern Canadian Arctic Archipelago). The mapping of glaciomarine landforms and units provides, together with updated radiocarbon information, a framework for catchment evolution and sediment delivery to the lake during deglaciation and glacio‐isostatically induced relative sea level fall. A staircase of deltas with descending altitudes provide evidence for a spatially diachronous timing of ice retreat from the catchments around Strathcona Lake. Swath bathymetric mapping coupled with acoustic sediment stratigraphy show draped infills with a transition from marine to rhythmically bedded lacustrine sediments produced by hyperpycnal flows. Multiproxy investigations on a set of sediment cores highlight proglacial varves interrupted by rhythmites resulting from the erosion of fluvially incised glaciomarine sediments stored in the catchment. Pluricentimetric proglacial varves formed during the last century in response to periods of intense glacial melt, notably since the 21st century. The sedimentary record suggests the varved sediments from Strathcona Lake can be used to reconstruct the melting history of the Prince of Wales Icefield. This work provides a geomorphological, sedimentological, and geochemical framework that should guide future varve‐based reconstructions of glacial and climatic variability in Ellesmere Island.</jats:p>

<jats:title>Abstract</jats:title><jats:p>This work studies the multiple sources of impacts and disturbances in the Laja River (Central Chile) and evaluates the changes in water and sediment flows and planimetric geomorphic changes.</jats:p><jats:p>The disturbances sources correspond to hydroelectric plants, water withdrawals for irrigation and the sustained decrease trend in rainfall in the basin. The changes in the plan‐view shape of the river reach were quantified using remote sensing techniques, through a supervised classification of Landsat 5 TM and 8 OLI satellite images, identified Water (W), Islands and Riverine Vegetation (IRV) and Bars and Banks Without Vegetation (BBWV), obtained a Kappa index&gt;0,83 for a period of 15 years (2006–2021).</jats:p><jats:p>Compared with historical records, the period of analysis shows a decrease in annual rainfall by 17.5%. In addition, water withdrawals for irrigation have contributed to a 64% decrease in monthly stream discharge during the dry season. As a consequence of the decrease in annual rainfall and water withdrawals for irrigation, the sediment transport capacity has also decreased by 10.5%.</jats:p><jats:p>The changes in morphological driving variables (stream flows and sediment transport regimes) have manifested themselves in morphological changes, where it was possible to establish that a change in the channel form occurred in the last 15 years, going from a river with a single channel to a braided one. An important vegetation establishment has accompanied this morphological change on both riverbanks and the central bars. The colonizing vegetation corresponds to fast‐growing non‐native species (<jats:italic>Salix</jats:italic> spp., <jats:italic>Populus</jats:italic> spp. and <jats:italic>Alnus spp</jats:italic>). A stabilization of the channel form is expected, consolidating itself as a braided section with alternating vegetated bars.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The high primary porosity and permeability of eogenetic karst aquifers permit water recharged through secondary dissolution features to be temporarily stored in aquifer matrix porosity. The recharged water contains elevated dissolved organic carbon (DOC) concentrations that, when oxidized, enhance limestone dissolution and impact carbon cycling. We evaluate the relationship between DOC oxidation and limestone dissolution using observations at a stream sink‐rise system and reversing spring in the Floridan aquifer, north‐central Florida, USA, where subsurface residence times of recharged water are days and months, respectively. We estimate water chemical compositions during surface water‐groundwater interactions at these two systems with mixing models of surface water and groundwater compositions and compare them with measured DOC, dissolved inorganic carbon (DIC), Ca<jats:sup>2+</jats:sup> and dissolved organic nitrogen (DON) concentrations. Differences between measured and modelled concentrations represent net changes that can be attributed to calcite dissolution and redox reactions, including DOC oxidation. DOC losses and Ca<jats:sup>2+</jats:sup> gains exhibit significant (p &lt; 0.01) inverse linear correlations at both the reversing spring (slope = −0.9, r<jats:sup>2</jats:sup> = 0.99) and the sink‐rise system (slope = −0.4, r<jats:sup>2</jats:sup> = 0.72). DOC oxidation in both systems was associated with decreases in the molar C:N ratio (DOC:DON). Significant (p &lt; 0.01) positive linear correlations between increases in Ca<jats:sup>2+</jats:sup> and DIC concentrations after correcting for DIC derived from calcite dissolution occurred at both the reversing spring (slope = 1.3, r<jats:sup>2</jats:sup> = 0.99) and the sink‐rise system (slope = 1.61, r<jats:sup>2</jats:sup> = 0.75). Greater deviations from the expected slope of −1 or +1 at the sink‐rise system than at the reversing spring indicate DOC oxidation contributes less dissolution at the sink‐rise system than at the reversing spring, likely from shorter storage in the subsurface. A portion of the deviation from expected slope values can be explained by the dissolution of Mg‐rich carbonate or dolomite rather than pure calcite dissolution. Despite this, slope values reflect kinetic effects controlling incomplete consumption of carbonic acid during dissolution reactions.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The dimensionless critical shear stress (<jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub>) needed for the onset of sediment motion is important for a range of studies from river restoration projects to landscape evolution calculations. Many studies simply assume a <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> value within the large range of scatter observed in gravel‐bedded rivers because direct field estimates are difficult to obtain. Informed choices of reach‐scale <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> values could instead be obtained from force balance calculations that include particle‐scale bed structure and flow conditions. Particle‐scale bed structure is also difficult to measure, precluding wide adoption of such force‐balance <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> values. Recent studies have demonstrated that bed grain size distributions (GSD) can be determined from detailed point clouds (e.g. using G3Point open‐source software). We build on these point cloud methods to introduce Pro+, software that estimates particle‐scale protrusion distributions and <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> for each grain size and for the entire bed using a force‐balance model. We validated G3Point and Pro+ using two laboratory flume experiments with different grain size distributions and bed topographies. Commonly used definitions of protrusion may not produce representative <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> distributions, and Pro+ includes new protrusion definitions to better include flow and bed structure influences on particle mobility. The combined G3Point/Pro+ provided accurate grain size, protrusion and <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> distributions with simple GSD calibration. The largest source of error in protrusion and <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> distributions were from incorrect grain boundaries and grain locations in G3Point, and calibration of grain software beyond comparing GSD is likely needed. Pro+ can be coupled with grain identifying software and relatively easily obtainable data to provide informed estimates of <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub>. These could replace arbitrary choices of <jats:italic>τ</jats:italic>*<jats:sub>c</jats:sub> and potentially improve channel stability and sediment transport estimates.</jats:p>