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1. Erodibility of Claypan Soils in Southeastern Kansas

   Mathis, Mark; Kulesza, Stacey; Sassenrath, Gretchen (November 2017, Kansas Governor's Water Conference)

   The objective of this research is to determine the fundamental mechanisms that cause loss of topsoil. Claypan soils cover approximately 10 million acres in the United States and are characterized by a highly impermeable layer below the topsoil. This impermeable layer acts as a barrier for infiltrating water which may be increasing the erosion rate and sediment transport of upper soil layers. This increasing topsoil depletion ultimately limits the productive capacity of agronomic fields. This study focuses on the undermining of the topsoil due to the impermeable claypan layer in Southeastern Kansas where the topsoil depth is limited and, in places, the claypan layer is exposed at the surface. Using LiDAR-derived digital elevation maps, the potential areas of critical soil loss and hydrologic flow patterns is determined. Surface soil apparent electrical conductivity (EC) measurements highlight the soil variability throughout the field. Electrical Resistivity Tomography (ERT) surveys is also performed to determine the depth to the claypan layer in low and high crop yield areas. The results indicate that the areas of high EC correlated with high clay content and low crop yield, while areas of low EC correlated with high crop yield. The results also indicate that the claypan layer in the low crop yield area is 1.0 m thick and significantly thins once reaching the high crop yield area. The next phase of this ongoing research is to measure the soil properties between the low and high crop yield areas, measure the movement of water at the claypan interface, and measure sediment transport at the claypan interface. 

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2. Comparison of basin-scale in situ and meteoric ¹⁰Be erosion and denudation rates in felsic lithologies across an elevation gradient at the George River, northeast Tasmania, Australia

   https://doi.org/10.5194/gchron-4-153-2022  

   VanLandingham, Leah A.; Portenga, Eric W.; Lefroy, Edward C.; Schmidt, Amanda H.; Bierman, Paul R.; Hidy, Alan J. (January 2022, Geochronology)

   Abstract. Long-term erosion rates in Tasmania, at the southern end of Australia's Great Dividing Range, are poorly known; yet, this knowledge is critical for making informed land-use decisions and improving the ecological health of coastal ecosystems. Here, we present quantitative, geologically relevant estimates of erosion rates for the George River basin, in northeast Tasmania, based on in situ-produced 10Be (10Bei) measured from stream sand at two trunk channel sites and seven tributaries (mean: 24.1±1.4 Mgkm-2yr-1; 1σ). These new10Bei-based erosion rates are strongly related to elevation, which appears to control mean annual precipitation and temperature,suggesting that elevation-dependent surface processes influence rates of erosion in northeast Tasmania. Erosion rates are not correlated with slopein contrast to erosion rates along the mainland portions of Australia's Great Dividing Range. We also extracted and measured meteoric 10Be(10Bem) from grain coatings of sand-sized stream sediment at each site, which we normalize to measured concentrations of reactive 9Beand use to estimate 10Bem-based denudation rates for the George River. 10Bem/9Bereac denudation ratesreplicate 10Bei erosion rates within a factor of 3 but are highly sensitive to the value of 9Be that is found in bedrock(9Beparent), which was unmeasured in this study. 10Bem/9Bereac denudation rates seem sensitive to recentmining, forestry, and agricultural land use, all of which resulted in widespread topsoil disturbance. Our findings suggest that10Bem/9Bereac denudation metrics will be most useful in drainage basins that are geologically homogeneous, where recentdisturbances to topsoil profiles are minimal, and where 9Beparent is well constrained. 

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3. A Continental‐Scale Estimate of Soil Organic Carbon Change at NEON Sites and Their Environmental and Edaphic Controls

   https://doi.org/10.1029/2022JG006981  

   Hu, Jie; Hartemink, Alfred E.; Desai, Ankur R.; Townsend, Philip A.; Abramoff, Rose Z.; Zhu, Zhe; Sihi, Debjani; Huang, Jingyi (May 2023, Journal of Geophysical Research: Biogeosciences)

   Key Points The NEON sites were estimated to have large soil organic carbon (SOC) loss in both topsoil and subsoil during 1984–2014 The carbon sequestration potential is limited in well‐developed and near carbon‐saturated soils in managed ecosystems Runoff/erosion and leaching, vertical translocation, and mineral sorption are dominant factors affecting SOC variation at National Ecological Observatory Network sites 

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4. Reduced Erosion Augments Soil Carbon Storage Under Cover Crops

   https://doi.org/10.1111/gcb.70133  

   Huang, Wenjuan; Jiang, Lifen; Zhou, Jian; Kim, Hyung‐Sub; Xiao, Jingfeng; Luo, Yiqi (March 2025, Global Change Biology)

   ABSTRACT Cover crops, a promising strategy to increase soil organic carbon (SOC) storage in croplands and mitigate climate change, have typically been shown to benefit soil carbon (C) storage from increased plant C inputs. However, input‐driven C benefits may be augmented by the reduction of C outputs induced by cover crops, a process that has been tested by individual studies but has not yet been synthesized. Here we quantified the impact of cover crops on organic C loss via soil erosion (SOC erosion) and revealed the geographical variability at the global scale. We analyzed the field data from 152 paired control and cover crop treatments from 57 published studies worldwide using meta‐analysis and machine learning. The meta‐analysis results showed that cover crops widely reduced SOC erosion by an average of 68% on an annual basis, while they increased SOC stock by 14% (0–15 cm). The absolute SOC erosion reduction ranged from 0 to 18.0 Mg C⁻¹ ha⁻¹ year⁻¹and showed no correlation with the SOC stock change that varied from −8.07 to 22.6 Mg C⁻¹ ha⁻¹ year⁻¹at 0–15 cm depth, indicating the latter more likely related to plant C inputs. The magnitude of SOC erosion reduction was dominantly determined by topographic slope. The global map generated by machine learning showed the relative effectiveness of SOC erosion reduction mainly occurred in temperate regions, including central Europe, central‐east China, and Southern South America. Our results highlight that cover crop‐induced erosion reduction can augment SOC stock to provide additive C benefits, especially in sloping and temperate croplands, for mitigating climate change. 

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5. Deeper topsoils enhance ecosystem productivity and climate resilience in arid regions, but not in humid regions

   https://doi.org/10.1111/gcb.16944  

   Zhang, Yakun; Desai, Ankur_R; Xiao, Jingfeng; Hartemink, Alfred_E (September 2023, Global Change Biology)

   Abstract Understanding the controlling mechanisms of soil properties on ecosystem productivity is essential for sustaining productivity and increasing resilience under a changing climate. Here we investigate the control of topsoil depth (e.g., A horizons) on long‐term ecosystem productivity. We used nationwide observations (n = 2401) of topsoil depth and multiple scaled datasets of gross primary productivity (GPP) for five ecosystems (cropland, forest, grassland, pasture, shrubland) over 36 years (1986–2021) across the conterminous USA. The relationship between topsoil depth and GPP is primarily associated with water availability, which is particularly significant in arid regions under grassland, shrubland, and cropland (r = .37, .32, .15, respectively,p < .0001). For every 10 cm increase in topsoil depth, the GPP increased by 114 to 128 g C m⁻² year⁻¹in arid regions (r = .33 and .45,p < .0001). Paired comparison of relatively shallow and deep topsoils while holding other variables (climate, vegetation, parent material, soil type) constant showed that the positive control of topsoil depth on GPP occurred primarily in cropland (0.73, confidence interval of 0.57–0.84) and shrubland (0.75, confidence interval of 0.40–0.94). The GPP difference between deep and shallow topsoils was small and not statistically significant. Despite the positive control of topsoil depth on productivity in arid regions, its contribution (coefficients: .09–.33) was similar to that of heat (coefficients: .06–.39) but less than that of water (coefficients: .07–.87). The resilience of ecosystem productivity to climate extremes varied in different ecosystems and climatic regions. Deeper topsoils increased stability and decreased the variability of GPP under climate extremes in most ecosystems, especially in shrubland and grassland. The conservation of topsoil in arid regions and improvements of soil depth representation and moisture‐retention mechanisms are critical for carbon‐sequestration ecosystem services under a changing climate. These findings and relationships should also be included in Earth system models. 

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