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The distribution of rare earth elements (REEs) was investigated in topsoils, soil profiles, bedrocks, and stream sediments collected from different geological environments in southern Konya to understand how natural and anthropogenic factors affect the geochemical behavior of REEs and the dynamics of pedogenic processes. The highest REE concentrations were observed in volcanic rocks and the lowest REE concentrations were observed in sedimentary rocks. The soils derived from volcanic rocks show the highest average REE content, followed by soils derived from sedimentary rocks and then soils derived from ophiolitic rocks. REE contents in soils derived from different geological units decrease in the following order: volcanic > sedimentary > ophiolitic. The average REE concentrations of soils in the study area are in decreasing order: Ce > La > Nd > Pr > Sm > Gd > Dy > Er > Yb > Eu > Tb > Ho > Tm > Lu. (La/Yb)_N ranged from 1.19 to 1.86 with an average value of 1.5 indicating considerable enrichment of LREEs in topsoil. The highest LREE/HREE fractionation was determined in the soils over sedimentary rocks. The soils have slightly negative Ce anomaly (Ce/Ce*= 0.98 to 0.99) and positive Eu anomaly (Eu/Eu* = 1.02 to 1.12). REEs in the soil profile developed on sedimentary rocks (Profile-I; HPPR) were higher than those developed on ophiolitic rocks (Profile-II; KHPR). The soil profile samples show slightly negative Ce anomalies (Profile I=0.93, Profile II=0.93) and positive Eu anomalies (Profile I=1.08, Profile II=1.39) similar to topsoils. The spatial distribution of REEs normalized to the Upper crust and Earth crust showed that parental materials control the prevalence of REEs in soils of southern Konya. The distribution of REEs with Eu and Ce anomalies in the soils is similar to REEs with Eu and Ce anomalies in the parental rocks. The spatial distribution of REEs in soils appears to be controlled by the lithology of the study area as well as mineral composition, weathering process, and pH. Enrichment factors (EF) and geoaccumulation index (Igeo) commonly indicating non-enriched soils correspond to natural materials.

Alpine meadow degradation results in an imbalance of soil nutrient supply, with soil microorganisms playing a pivotal role as regulators of soil nutrient cycling. However, the metabolic limitations of soil microorganisms during the process of alpine meadow degradation have not been adequately elucidated. The objective of this study was to uncover the characteristics and driving factors underlying the metabolic limitations imposed on soil microorganisms during alpine meadow degradation. Here, we assessed the levels of total and available nutrients in soil, as well as microbial biomass and extracellular enzyme activities (including cellobiosidase [CBH], β-1,4-glucosidase [BG], β-1,4-N-acetylglucosaminidase [NAG], L-leucine aminopeptidase [LAP], and alkaline phosphatase [AP]) in degraded alpine meadows located on the northeastern Tibetan Plateau. The results demonstrated that alpine meadow degradation led to a reduction in soil C, N, and P contents, as well as available nutrients, microbial biomass, and soil extracellular enzyme activities. Analysis using the vector-threshold element ratio (VT) model revealed an increasing trend in microbial C limitation with the progression of alpine meadow degradation. In the 0–20 cm soil layer, microbial N limitation gradually weakened and shifted towards P limitation; however, an opposite pattern was observed in the 20–40 cm soil layer with worsening alpine meadow degradation. Additionally, alpine meadow degradation enhanced the microbial carbon use efficiency (CUE), which was negatively correlated with microbial C limitation but was positively correlated with N & P limitations. Moreover, there was a weakening of soil microbial homeostasis associated with increased alpine meadow degradation levels, where available nutrients played a crucial role in driving nutrient limitations for soil microbes in degraded alpine meadows. The findings of this study contribute to enhancing the understanding of the key factors governing soil microbial nutrient limitation in degraded alpine meadows, thereby providing valuable theoretical support for improving soil quality and health in such alpine meadow ecosystems on the Qinghai-Tibetan Plateau.

Identifying crop-specific sediment sources is important, and conventional fingerprinting methods do not do so sufficiently, which limits their usefulness. The application of compound-specific stable isotopes (CSSIs) enables crop-specific sediment sources to be identified. To this end, this study applied the CSSI method to the intensively farmed loess soil Geesgraben catchment (75 km²), in Central Germany. We used this catchment because the importance of different surface and subsurface sediment sources is unknown in temperate loess soil areas. The study also compared radionuclide and spectral fingerprinting methods, as well as spatiotemporal contribution of sediment sources. Specifically, the CSSI method, based on measuring δ¹³C signatures of fatty acids, was applied to distinguish C3 and C4 plants, and riverbank sediment sources, which were identified using a multivariate mixing model. At the midstream site, the riverbanks contributed a mean of 12 % of the sediment, while the C3 and C4 plants each contributed 44 %. At the downstream site, according to the CSSI method, the riverbanks contributed 28 %, while the C3 and C4 plants contributed 9 % and 63 %, respectively. In comparison, according to the radionuclide and spectral methods, the downstream riverbanks contributed 41 % and 10 %, respectively; generally, this shows relatively lower contribution to the surface sediment contribution. The riverbanks contribution increased with catchment size, due to downstream changes caused by the deposition of surface sediments. Thus, results showed that CSSIs of δ¹³C of fatty acids can distinguish C3 vs. C4 plants and surface vs. riverbank sources at the catchment scale. However, radionuclides remain useful in heterogeneous catchments because they are not influenced by soil type or lithology. This information is crucial for implementing agricultural practices that can decrease sediment loads to river ecosystems.

Soil inorganic carbon (SIC) accounts for more than one-third of the total soil carbon pool, but the effect of agricultural management on carbonates dynamics in Mediterranean semi-arid calcareous soils has largely been ignored and remains unclear. However, SIC plays a key role in physical, chemical and, biological properties of soils, which in turn can affect plant growth and productivity. Based on a 7-year field experiment in a paired irrigated and non-irrigated trial, with two different crops (maize and wheat), we investigated the effects of the land use change (from non-irrigated wheat to irrigated maize) on the SIC dynamics in the topsoil (0–30 cm) of a carbonate-rich soil in Navarre, northern Spain. The results obtained using the accepted equation for determining carbonate type showed that during the 7-year study period, irrigation application and the crop change modified the carbonate typology (lithogenic and pedogenic) in a very short period, without affecting the total SIC content. The main drivers of pedogenic carbonate formation in this case appear to be the water volume and the type of organic matter entering the soil (from C3 plants or C4 plants). However, the equation seems to be strongly dependent on the type of soil organic carbon, which can introduce uncertainties when used to determine the proportion of pedogenic carbonates in soils experiencing a crop change from C3 to C4 plants.

Agricultural fields are a known contributor of sediment to streams and rivers, but determining specific sources of sediment in agricultural watersheds characterized primarily by C3 plants has proven difficult with traditional sediment fingerprinting methods. This study aimed to use compound-specific stable isotopes of long-chain fatty acids (LCFAs) to determine the sediment contribution from multiple sources – cropped, grazed, forage, riparian zones, banks, and forested soils – to Murray Creek, a tributary to the Nechako River in British Columbia, Canada. Source and sediment samples were collected in 2019 and analysed for LCFA concentrations and δ¹³C FA values (C20:0-C30:0, C32:0). Statistical analyses were undertaken to determine the discrimination capabilities of the LCFAs. Results showed that discrimination was poor across the agricultural land uses, though forested samples were clearly identified. For mixing in Murray Creek, just three sources – agriculture (including riparian areas), forested, and banks – were used. The results found agriculture and banks to be the primary sources of sediment. This is important because Murray Creek delivers sediment to important fish spawning habitat, which has been identified as one of multiple causes of fish population declines. The difficulty in discriminating between the agricultural land use types reflects multiple confounding factors including the multi-use nature of agricultural land in Murray Creek (i.e., land can be used as harvested forage and unmanaged grazing in the same year), the similarities in isotopic signatures across C3 plants, and the temporal insensitivity of the analysis, which may pick up the vegetation signatures of previous years. While the LCFAs were not able to identify specific fields of importance in the timeframe of this study, this technique would be valuable if the sources were more unique, if more samples of each source were taken for better characterization, and if previous land use in the agricultural fields was incorporated.

The severe non-point pollution threatens to karst aquifers, which supply freshwater resources for approximately 25 % of the global population. The unique natural landscape of diverse rock outcroppings on karst slopes significantly influences hydrological processes and alters the solute transport characteristics. However, there is still insufficient understanding of the impact of bedrock outcroppings on solute transport. This study aimed to investigate the spatial patterns of dissolved nitrogen and phosphorus transport in karst slopes, considering the effects of bedrock morphology, bedrock patterns, and rainfall type. The findings indicated that sub-surface runoff production was associated with higher concentrations of dissolved total nitrogen (TN) (7.72 mg·L^-1–30.88 mg·L^-1) and that the soil–bedrock interface became the primary pathway for TN migration, particularly during moderate rainfall (10–25 mm·d^-1), achieving efficiencies of 51.54 % to 91.92 % depending on bedrock distribution patterns. Conversely, surface runoff had 1.05–2.61 times more dissolved phosphorus (TP) concentration than sub-surface runoff, soil-rock runoff, and underground pore fissure runoff, with surface pathway losses being the main TP loss channel. The TN and TP positively correlation with rainfall, with correlation coefficients exceeding 0.85 across different bedrock pattern treatments. Power function analysis revealed exponents of 3.58 and 3.34 for TN and TP loss fluxes, indicating higher vulnerability of dissolved TN to runoff losses. Moreover, surface dissolved TN and TP losses were greater in the bedrock morphologies 1:2 aspect ratio than 1:1 aspect ratio and were aggregated distribution > uniform distribution > centered distribution in various bedrock distribution patterns. The findings suggest that minimizing the scattered distribution of bedrock on karst slopes has potential for decreasing influxes of dissolved substances into underground aquatic ecosystems.

Vegetation is sensitive to climate changes. Many studies have been done on the boundary transition of vegetation types in response to climate changes along elevation gradient in mountain areas, but less on the boundary transition of zonal vegetation types in vast plain areas. The forest, meadow steppe, typical steppe, desert steppe, and desert vegetation are successively distributed on the 2400 km long transect with climate aridity increasing from the northeast to the southwest in Inner Mongolia. While the climate change impacts on vegetation functions have been assessed, no information is available on if these vegetation types migrate under climate changes. Based on MODIS and Landsat remote sensing data and vegetation type partition data, we first used the random forest classification method to derive the spatiotemporal distribution of these five vegetation types in Inner Mongolia for the period from 2001 to 2020. Then we explored the boundary transitions between the successively distributed vegetation types, and elucidated the causes of the boundary transitions using partial correlation and Spearman’s rank correlation analyses between the NDVI and climate data (temperature and precipitation). We found a general and gradual migration of steppe vegetation towards drier area along climatic gradient. Notably, meadow steppe shifted approximately 11,396 km² into the original typical steppe areas, and desert steppe shifted approximately 22,548 km² into the original desert areas. This boundary shift phenomenon was primarily influenced by the increase in growing season precipitation over the 20-year period. Our study provides the evidence for the migration of vegetation types along climate gradients in response to climate changes, and provides a method for analyzing vegetation transitions under environmental changes.

Forest fires cause serious damage to mountain landforms and trigger frequent post-fire debris flows. Although post-fire debris flow exhibits time evolution, the key factors controlling its evolution remain unclear. A detailed field investigation, rainfall data collection and remote sensing analysis were conducted to study the debris flow events following the “3.08” forest fire in Xiangjiao gully. The destructive effect of forest fires, the control factors and inherent evolution mechanism of post-fire debris flow were explored. The results highlight that the great disturbance of forest fires to the hydrological response and material source supply conditions promote the outbreak of debris flows. In the rapid response stage of fire, the internal driving force of debris flow evolution is the self-healing of hydrological response characteristics of the basin, including material depletion, particle coarsening and vegetation restoration. In the long-term impact stage, the evolution of debris flows is mainly controlled by factors such as a decrease in root-soil strength caused by root rot, multi-stage gully bank landslide activity, and blockage of woody debris. A conceptual model for the evolution of post-fire debris flows is proposed based on the above evolution characteristic analysis. In particularly, this study emphasizes the catastrophic effect of woody debris during the evolution of post-fire debris flows. The research results provide scientific basis for long-term debris flow risk assessment and mitigation design in recently burnt areas.

Desertification due to wind erosion poses a major threat to global ecosystems, especially in the drying lakes and deserts, where the occurrence of drought events has led to a dramatic increase in crusted surface dust emissions in the region. Soil crusts are a widely occurring surface feature that play a critical role in dust emission when subjected to sand grain impacts. However, existing research lacks a comprehensive model rooted in physical mechanisms, potentially hindering accurate global dust cycle simulations. This paper presents a physical model for analyzing dust emissions from soil crust surfaces under saltation bombardment, and establishes an analytical expression between the rate of wind erosion of crust surfaces and the physicomechanical properties of impacted particles and crusts. This study demonstrated a unique linear relationship between sand particle mass flux and surface crust wind erosion rate, which was verified by field and wind tunnel tests. A sensitivity analysis reveals that the wind erosion rate increases and then decreases with increasing particle size of the impacting particles and crust thickness, with peak erosion occurring, and in addition, crusts with high stiffness and low strength are more likely to be destroyed, with higher surface dust release capacity. The work in this paper fills a gap in the wind erosion parameterization scheme and helps to improve the accuracy of dust release simulation in large and mesoscale models.

Biocrusts perform important ecological functions such as stabilizing the soil surface, resisting erosion, regulating soil water partitioning, storing soil fertility, and promoting biological community diversity. The mechanical stability of biocrusts is the physical basis for many of their ecological functions, while their high mechanical stability is often thought to be related to the extracellular polymeric substances (EPS) produced by microbes. Here, we collected bare soil and three types of biocrusts (cyano crusts, cyano and moss mixed crusts, and moss crusts) in the northern Loess Plateau of China. We investigated the EPS properties and microbial communities of biocrusts and explored how microbial communities influence the biocrust mechanical stability through secreting EPS. Our results showed that all the three types of biocrusts were more stable than bare soil, with moss crusts having the highest mechanical stability. Furthermore, the bacterial communities of the biocrusts were dominated by Cyanobacteria, Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroidetes, whilst their fungal communities were dominated by Ascomycota and Basidiomycota. Moreover, the moss crusts exhibited higher contents of EPS-polysaccharide, EPS-protein, uronic acid, and hydrophobic monosaccharides (rhamnose and arabinose) than mixed and cyano crusts. Also, the thickness, roughness, and viscosity of EPS from moss crusts were the highest in all habitats. In addition, the indirect effect of bacterial community on biocrust mechanical stability through changing EPS components accounted for 69.0% of the total effect, suggesting a partially mediated role of EPS. In contrast, the indirect effect of fungal community on biocrust mechanical stability through modifying EPS morphology accounted for 93.0% of the total effect, indicating a fully mediated effect of EPS. In conclusion, the EPS associated with bacterial and fungal communities demonstrated their high ability to confer biocrust mechanical stability, thus maintaining their critical functions in drylands, especially in stabilizing soil surface and protecting it from water and wind erosion.