Land-use impact on porosity and water retention of soils rich in rock fragments

Sekucia, F.; Dlapa, Pavel; Kollár, Jozef; Cerdà, Artemi; Hrabovský, Andrej; Svobodová, L.

doi:10.1016/j.catena.2020.104807

Cited by 39 publications

(12 citation statements)

References 72 publications

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“…Many studies have shown that soil organic matter has a significant positive effect on total porosity (Jarvis, Forkman, et al, 2017;Johannes et al, 2017;Meurer et al, 2020,b), whereas only a few studies have investigated the effects of SOM on the VSD. However, experiments have found impacts on a wide range of pore diameters, including both smaller matrix pores and larger mesopores (Fukumasu et al, 2022;Kirchmann & Gerzabek, 1999;Sekucia et al, 2020;Zhang et al, 2021), which implies an increase in the heterogeneity of the VSD and, therefore, the KL divergence. The strong relationships observed between the model parameters of the PSD and the small pore region of the bimodal model (Figure 8a,b) do suggest that the latter is dominated by textural pore space.…”

Section: Discussionmentioning

confidence: 99%

Relative entropy as an index of soil structure

Klöffel

Jarvis

Yoon

et al. 2022

European J Soil Science

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Soil structure controls key soil functions in both natural and agro-ecosystems. Thus, numerous attempts have been made to develop methods aiming at its characterization. Here we propose an index of soil structure that uses relative entropy to quantify differences in the porosity and pore(void)-size distribution (VSD) between a structured soil derived from soil water retention data and the same soil without structure (a so-called reference soil) estimated from its particle-size distribution (PSD). The difference between these VSDs, which is the result of soil structure, is quantified using the Kullback-Leibler Divergence (KL divergence). We applied the method to soil data from two Swedish field experiments that investigate the long-term effects of soil management (fallow vs. inorganic fertilizer vs. manure) and land use (afforested land vs. agricultural land dominated by grass/clover ley) on soil properties. The KL divergence was larger for the soil receiving regular addition of manure compared with the soils receiving no organic amendments. Furthermore, soils under afforested land showed significantly larger KL divergences compared to agricultural soils near the soil surface, but smaller KL divergences in deeper soil layers, which closely mirrored the distribution of organic matter in the soil profile. Indeed, a significant positive correlation (r = 0.374, p < 0.001) was found between soil organic carbon concentrations and KL divergences across all sites and treatments.Despite challenges related to modelling the VSD of the reference soil without structure, the proposed index proved useful for evaluating differences in soil structure in response to soil management and land-use change and reflected the expected effects of soil organic matter on soil structure. We conclude that relative entropy shows great potential to serve as an easy-to-use index of soil structure, as it only requires widely available data on soil physical and hydraulic properties. Highlights• A new index of soil structure is proposed based on relative entropy • A method is developed that separates the effects of soil texture and structure on the pore space

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Section: Discussionmentioning

confidence: 99%

Relative entropy as an index of soil structure

Klöffel

Jarvis

Yoon

et al. 2022

European J Soil Science

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“…Care must be taken before generalizing these results to arbitrary conditions, e.g., highly dynamic boundary conditions with sequences of precipitation and higher and lower evaporation rates, which might yield different results due to the occurrence of nonequilibrium water dynamics and hysteresis. For real stony soils, changes in the pore size distribution of the background soil may result from the presence of RFs (Sekucia et al, 2020), with corresponding consequences for the effective SHPs. This influence was reported to be more common in compactible soils with a shrinkage-swelling po-tential (Fiès et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Effective hydraulic properties of 3D virtual stony soils identified by inverse modeling

Naseri

Iden

Durner

2022

SOIL

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Abstract. Stony soils that have a considerable amount of rock fragments (RFs) are widespread around the world. However, experiments to determine the effective soil hydraulic properties (SHPs) of stony soils, i.e., the water retention curve (WRC) and hydraulic conductivity curve (HCC), are challenging. Installation of measurement devices and sensors in these soils is difficult, and the data are less reliable because of their high local heterogeneity. Therefore, effective properties of stony soils especially under unsaturated hydraulic conditions are still not well understood. An alternative approach to evaluate the SHPs of these systems with internal structural heterogeneity is numerical simulation. We used the Hydrus 2D/3D software to create virtual stony soils in 3D and simulate water flow for different volumetric fractions of RFs, f. Stony soils with different values of f from 11 % to 37 % were created by placing impermeable spheres as RFs in a sandy loam soil. Time series of local pressure heads at various depths, mean water contents, and fluxes across the upper boundary were generated in a virtual evaporation experiment. Additionally, a multistep unit-gradient simulation was applied to determine effective values of hydraulic conductivity near saturation up to pF=2. The generated data were evaluated by inverse modeling, assuming a homogeneous system, and the effective hydraulic properties were identified. The effective properties were compared with predictions from available scaling models of SHPs for different values of f. Our results showed that scaling the WRC of the background soil based on only the value of f gives acceptable results in the case of impermeable RFs. However, the reduction in conductivity could not be simply scaled by the value of f. Predictions were highly improved by applying the Novák, Maxwell, and GEM models to scale the HCC. The Maxwell model matched the numerically identified HCC best.

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“…Besides the natural causes mentioned above, management disturbances, such as stone removal, ploughing, and flood irrigation, are also responsible for this phenomenon. (1) Rock fragments could enhance soil moisture (Dai et al, 2022; Lai et al, 2021), which was a critical factor affecting SOC distribution in arid areas (Kosmas et al, 1994; Lai, Zhu, et al, 2022; Sekucia et al, 2020). The farmers removed rock fragments from the soil to reduce wear and tear on cultivation tools in orchards.…”

Section: Discussionmentioning

confidence: 99%

“…RFC is a dominant control of SOC distribution in mountainous areas (Schiedung et al, 2017; Wang, Liu, et al, 2011; Zhang & Shao, 2014). Rock fragments can affect SOC distribution by altering the physical (Dai et al, 2022; Gargiulo et al, 2016; Lai et al, 2021; Sekucia et al, 2020), chemical (Lv et al, 2019), and biological properties of soil (Lai, Zhu, et al, 2022; Tetegan et al, 2015). First, moderate RFC may facilitate SOC accumulation by improving pore distribution and water retention in soil under drought conditions (Lai et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

The difference in soil organic carbon distribution between natural and planted forests: A case study on stony soils mountainous area in the Upper Min River Arid Valley, China

Han

Wang

et al. 2022

Soil Use and Management

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Few studies have been conducted on the factors and distribution of soil organic carbon (SOC) in plantation forests in arid mountainous regions, especially in orchards. We aimed to unravel the SOC distribution among land‐use types and the effects of altitude gradients and rock fragment content (RFC) on SOC accumulation and sequestration in the Upper Min River Arid Valley, China. The differences in SOC distribution among land‐use types were quantified. The correlation analysis of SOC with various factors, such as altitude and RFC, was conducted. The variation percentage in SOC content and stocks was explained by the factors' contribution using mixed‐effects models. SOC distribution was characterized by high content and low stocks in native forests and shrubs, high content and high stocks in eco‐forest, and low content and high stocks in orchards. At the surface (0–30 cm), SOC content and stocks in orchards (cherry, plum, and apple) were significantly lower than those in eco‐forests. There was a significant positive correlation between altitude and SOC content at the surface but not at the subsoil (30–60 cm). With RFC increased, the surface SOC content decreased in native forests, shrubs, and eco‐forests, while it increased in orchards. Our results suggest that land management is the main factor controlling the variation in SOC distribution. Enhancing the surface SOC stability in orchards by land management is a priority for soil carbon pool management in the Arid Valleys.

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Land-use impact on porosity and water retention of soils rich in rock fragments

Cited by 39 publications

References 72 publications

Relative entropy as an index of soil structure

Relative entropy as an index of soil structure

Effective hydraulic properties of 3D virtual stony soils identified by inverse modeling

The difference in soil organic carbon distribution between natural and planted forests: A case study on stony soils mountainous area in the Upper Min River Arid Valley, China

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