Silicon (Si) is recognized as a beneficial element for plant growth and plays an increasingly important role in agricultural sustainability and environmental preservation. The Pampean Plain region, characterized by its high fertility and intensive agricultural use, is increasingly affected by pressures that alter soil-plant-environment interactions. This study provides the first field-based data on the dynamics of silicophytoliths and silicon in undisturbed Mollisols of the southeastern Pampean Plain, assessing their influence on soil chemical and mineralochemical properties. Silicophytoliths were characterized by optical microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). Contents of silicon, macronutrients, micronutrients, and potentially toxic elements were analyzed in soil solution using spectrophotometry and inductively coupled plasma optical emission spectroscopy (ICP-OES). Microscopic analyses revealed various elements associated with silicophytoliths, confirming their role as dynamic sources and sinks of elements in the soil solution. Furthermore, nanospherical internal structures inside silicophytoliths were characterized for the first time in surface soil horizons, revealing preferential element retention at internanosphere microsites. Overall, element contents decreased with depth within the studied horizons (A and BA, 0-23 cm). Positive correlations were observed between silicon and most nutrients and potentially toxic elements in both analyzed horizons, whereas phosphorus exhibited an opposite trend. These results establish the first geochemical baseline for silicon dynamics in undisturbed Mollisols and provide a reference framework for evaluating how agricultural intensification, grassland conversion and other land-use changes may alter silicon and silicophytolith biogeochemical dynamics under field conditions in temperate grassland soils.
Accurate cropland change detection from high-resolution remote sensing images is essential for agricultural resource monitoring, land management, and food security. Existing methods struggle with two primary challenges: (1) severe pseudo-change noise and false alarms, caused by sole reliance on simple spatial or temporal difference enhancement, and (2) inadequate fine-grained cropland change detection, resulting from boundary detail degradation during fixed interpolation decoding. To address these issues, we propose a SpatioTemporal Difference-Enhancement Network (STDENet) with semantic flow alignment for effective cropland change detection from high-resolution remote sensing images. Built on a pyramid vision transformer V2 (PVT-V2) encoder, STDENet integrates three key innovations: a spatiotemporal dual-branch difference enhancement (STDDE) module that jointly captures temporal variations and spatial discrepancies to suppress irrelevant responses from unchanged or spectrally similar regions; an adaptive boundary-aware (ABA) module that dynamically extracts four-directional texture cues to enhance boundary representations; and a semantic flow-aligned decoding (SFAD) module that predicts semantic flow fields to warp high-level difference features and align them with low-level spatial details for fine-grained structure recovery. We evaluate the STDENet on one self-constructed dataset, DYCD, and two public benchmark datasets, CLCD and Hi-CNA. Comparative experiments confirm that STDENet consistently outperforms existing state-of-the-art methods on all three datasets, improving IoU by 3.41 %, 4.90 %, and 1.98 % over the second-best methods on DYCD, CLCD, and Hi-CNA, respectively. By enhancing global structural information through the spatial branch and local change responses through the temporal branch, the spatiotemporal interaction design improves the feature separability of cropland changes. Semantic flow alignment helps restore fine-grained details by producing a more stable decoding process for local contours in cropland change patches. STDENet also demonstrates stronger resistance to interference and better adaptability to phenological variations among crop growth, pre-sowing, and post-harvest periods. Large-scale applications further indicate its generalization ability across heterogeneous cropland structures.
Soil aggregate stability (AS) is a critical indicator of soil physical quality, yet its long-term drivers in vulnerable silty soils remain inadequately quantified. This study analyzed the determinants of AS over 25 years (1999–2023) in a long-term field experiment on a temperate silty Luvisol, comparing four cropping systems: conventional (CON), low-input (LI), organic (ORG), and conservation agriculture (CA). Aggregate stability was assessed biennially using Le Bissonnais tests targeting distinct disaggregation mechanisms, alongside soil organic carbon (SOC), quantitative management indicators (intensity of crop sequence, grass-to-legume ratio, crop diversity and carbon biomass, and nitrogen inputs), and climatic variables. Mean AS remained low in frequently tilled systems (CON, ORG), reflecting the legacy of mechanical disturbance. In contrast, CA achieved a stable, high-AS state after approximately six years, which persisted. Intermittent tillage in LI prevented long-term recovery, underscoring a non-linear response to disturbance frequency. While SOC accumulation was associated with improved aggregate stability, it was insufficient to explain AS dynamics on its own. Long-term aggregate stability was primarily associated with cumulative indicators of crop diversity and below-ground biomass, whereas short-term variations responded more strongly to recent management factors such as crop sequence composition, nitrogen inputs, and rooting continuity. Precipitation exhibited dual effects, with recent rainfall promoting aggregate disruption, particularly in the Slaking test, whereas antecedent moisture conditions were generally associated with increased aggregate stability. Among the tests evaluated, Micro-cracking proved particularly sensitive to management and environmental drivers. The study demonstrates that sustained reduction of mechanical disturbance is the primary prerequisite for restoring aggregate stability in silty agroecosystems. Complementary management practices become effective determinants of soil structure only once mechanical constraints are alleviated. These findings provide a hierarchical framework for prioritizing soil management strategies to enhance the physical health and resilience of cultivated silty soils.
How surface uplift is coupled to crustal shortening and thickening remains a central question in orogenic systems research. Existing stable-isotope records in the southern Central Andes show increasing δ18O and δD values during Miocene retroarc shortening, inconsistent with expected enhanced orographic distillation. However, the role of changing climate and moisture source is underexplored in this region, where Pacific- and Atlantic-derived precipitation regimes meet. We pair pedogenic carbonate δ18O/δ13C and volcanic glass δD from the Manantiales foreland basin ( ∼ 32∘S) with constraints from regional sedimentology to assess topographic and climatic evolution. Carbonate δ18O and δ13C values are high between ∼ 37 and 18.6 Ma (δ18O means −8.5 and −7.9 ‰), across a 33–21 Ma depositional hiatus, recording low paleoelevation in an arid foredeep. These values then decrease by ∼ 4.5 ‰ between 18.6 and 18.3 Ma, interpreted to reflect surface uplift as the basin entered the wedge-top depozone. Glass δD values are consistently low after 17.9 Ma (−95.3 to −104.9 ‰), whereas carbonate δ18O values increase by ∼ 1.7 ‰ after ∼ 16.5 Ma. We interpret this to record increased monsoonal moisture delivery during the Miocene Climatic Optimum and/or enhanced dry-season evaporation. Using isotope–elevation models accounting for ancient temperature and moisture-source changes, we calculate 1,886 m (68% CI: 1,446–2,255 m) of syndepositional surface uplift from carbonate δ18O, directionally consistent with glass δD. Surface uplift coincided with rapid crustal shortening and thickening, indicating coupled orogenic growth. These findings support model predictions that Andean mountain building alters isotopic signals by enhancing orographic distillation and shifting moisture-source regime.
This work aims to develop bio-based oxygenated fuel additives through the acetalization of furfural with two polyols - ethylene glycol and glycerol - using an ionic liquid (IL), 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate [C(4)SO(3)Hmim][HSO4], as a homogeneous acid catalyst, as well as two series of heterogeneous catalysts prepared by supporting this IL on silica gel 60 and SBA-15 mesoporous silica at variable loadings (10-50 wt%). All catalysts showed good activity in the formation of the target cyclic ether products: 2-(furan-2-yl)-1,3-dioxolane (I), cis/trans-(2-(furan-2-yl)-1,3-dioxolan-4-yl)methanol (II), and cis/trans-2-(furan-2-yl)-1,3-dioxan-5-ol (III). The supported catalysts outperformed the unsupported IL: the best-performing catalyst, SBAIL30, achieved a cyclic acetal yield of 51%, compared to 40% obtained with the free IL under the same conditions. This sample is characterized by its elevated number of strong acid sites, derived from sulfonic groups within the IL structure, as confirmed by XPS analysis. Furthermore, heterogeneous catalysts significantly altered the stereochemical outcome of the reaction: while the 6-membered ring product (III) predominates in the uncatalyzed reaction, the SILx and SBAILx catalysts favored formation of the 5-membered ring isomer (II), with isomer ratios of up to 64:36 (II:III) for SBAIL30 and > 70% selectivity toward II for SBAIL40.
