Journal articles: 'Soil variables'

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Zádorová, T., D. Žížala, V. Penížek, and Š. Čejková. "Relating extent of colluvial soils to topographic derivatives and soil variables in a Luvisol sub-catchment, Central Bohemia, Czech Republic." Soil and Water Research 9, No. 2 (April 25, 2014): 47–57. http://dx.doi.org/10.17221/57/2013-swr.

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Colluvial soils, resulting from accelerated soil erosion, represent a significant part of the soil cover pattern in agricultural landscapes. Their specific terrain position makes it possible to map them using geostatistics and digital terrain modelling. A study of the relationship between colluvial soil extent and terrain and soil variables was performed at a morphologically diverse study site in a Luvisol soil region in Central Bohemia. Assessment of the specificity of the colluviation process with regard to profile characteristics of Luvisols was another goal of the study. A detailed field survey, statistical analyses, and detailed digital elevation model processing were the main methods utilized in the study. Statistical analysis showed a strong relationship between the occurrence of colluvial soil, various topographic derivatives, and soil organic carbon content. A multiple range test proved that four topographic derivatives significantly distinguish colluvial soil from other soil units and can be then used for colluvial soil delineation. Topographic wetness index was evaluated as the most appropriate terrain predictor. Soil organic carbon content was significantly correlated with five topographic derivatives, most strongly with topographic wetness index (TWI) and plan curvature. Redistribution of the soil material at the study site is intensive but not as significant as in loess regions covered by Chernozem. Soil mass transport is limited mainly to the A horizon; an argic horizon is truncated only at the steepest parts of the slope.

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Dotto, Andre Carnieletto, Jose A. M. Demattê, Raphael A. Viscarra Rossel, and Rodnei Rizzo. "Soil environment grouping system based on spectral, climate, and terrain data: a quantitative branch of soil series." SOIL 6, no. 1 (May 12, 2020): 163–77. http://dx.doi.org/10.5194/soil-6-163-2020.

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Abstract. Soil classification has traditionally been developed by combining the interpretation of taxonomic rules that are related to soil information with the pedologist's tacit knowledge. Hence, a more quantitative approach is necessary to characterize soils with less subjectivity. The objective of this study was to develop a soil grouping system based on spectral, climate, and terrain variables with the aim of establishing a quantitative way of classifying soils. Spectral data were utilized to obtain information about the soil, and this information was complemented by climate and terrain variables in order to simulate the pedologist knowledge of soil–environment interactions. We used a data set of 2287 soil profiles from five Brazilian regions. The soil classes of World Reference Base (WRB) system were predicted using the three above-mentioned variables, and the results showed that they were able to correctly classify the soils with an overall accuracy of 88 %. To derive the new system, we applied the spectral, climatic, and terrain variables, which – using cluster analysis – defined eight groups; thus, these groups were not generated by the traditional taxonomic method but instead by grouping areas with similar characteristics expressed by the variables indicated. They were denominated as “soil environment groupings” (SEGs). The SEG system facilitated the identification of groups with equivalent characteristics using not only soil but also environmental variables for their distinction. Finally, the conceptual characteristics of the eight SEGs were described. The new system has been designed to incorporate applicable soil data for agricultural management, to require less interference from personal/subjective/empirical knowledge (which is an issue in traditional taxonomic systems), and to provide more reliable automated measurements using sensors.

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Sheng, Daichao, Delwyn G. Fredlund, and Antonio Gens. "A new modelling approach for unsaturated soils using independent stress variables." Canadian Geotechnical Journal 45, no. 4 (April 2008): 511–34. http://dx.doi.org/10.1139/t07-112.

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Although a number of constitutive models for unsaturated soils exist in the literature, some fundamental questions have not been fully answered. There are questions related to (i) the change of the yield stress with soil suction, (ii) modelling slurry soils, and (iii) the smooth transition between saturated and unsaturated soil states. This paper addresses these questions by proposing an alternative modelling approach. The paper first presents a volumetric model for unsaturated soils. This volumetric model is then used to derive the yield surface in the suction – mean stress space. Hysteresis associated with soil-water characteristic curves is then formulated in the same framework of elastoplasticity. It is shown that volume collapse during wetting and plastic shrinkage during initial drying are both direct results of a suction-dependent hardening law. The proposed model seems to be more flexible in modelling different types of unsaturated soils than most models in the literature. The model can be applied to soils that are dried or loaded from initially slurry conditions, for soils that have low to high air-entry values, and for compacted soils as well.

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Sultanov, Karim, Pavel Loginov, Sabida Ismoilova, and Zulfiya Salikhova. "Variable moduli of soil strain." E3S Web of Conferences 97 (2019): 04013. http://dx.doi.org/10.1051/e3sconf/20199704013.

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The experimental diagrams between stress and strain components for soft soils are non-linear. Nonlinear diagrams qualitatively differ for soils of undisturbed and disturbed structures. It is believed that the manifestations of nonlinear properties of soil are associated with micro-destruction of soil structure under compression and, therefore, with changes in its mechanical characteristics under strain. It follows that the modulus of elasticity, Poisson’s ratio, viscosity and other mechanical parameters are the variables in the process of soil strain. Based on this, from the experimental results given in scientific literature, the changes in the modulus of elasticity and plasticity of soil are determined depending on the values of compression strain. In the process of static and dynamic compression of soil it is almost impossible to determine the boundaries of elastic and plastic strains in soft soil. So, the modulus under soil compression is called the strain modulus. From published results of experiments on dynamic and static compression of soil the most informative ones have been selected. Processing the selected compression diagrams of soft soil, the secant moduli of strain for loess soil and clay have been determined. It is established that the moduli of strain of clay and loess soil under static and dynamic strain vary depending on the rate of strain, the state of the structure and the level of compressive load.

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Riwandi and Merakati Handajaningsih. "Relationship between Soil Health Assessment and the Growth of Lettuce." Journal of Tropical Soils 16, no. 1 (July 1, 2013): 25–32. http://dx.doi.org/10.5400/jts.2011.v16i1.25-32.

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Soil health is very important point for plant growth which is measured by several indicators. The purposes of the research were to assess and to classify soil health Padang Betuah area of Bengkulu, and to compare between soil health indicators and lettuce plant performance indicators. Soils, consist of mineral and peat soils, were sampled using a soil random sampling technique. Lettuce plants were grown in polybags using sample soils. Both lettuce performance and soil health were assessed by calculating the percentage of total scores of lettuce plant or soil performance indicators which derived from variables observed. Soil variables for field evaluation included color, moisture content, texture, structure, compaction, land slope, organic matter, pH, amount of earthworm, erosion level, LCC (Legume Cover Crop), and vegetation performance. Soil variables for laboratory evaluation were pH, electrical conductivity (EC), total Carbon and Nitrogen, available-Posphorus, cation exchangeable capacity, basesaturation, and aluminum saturation. While, the variables for lettuce growth performance included plant height, numbers of leaf, degree of leaf greenness, plant fresh weight, and relative percentage of shoot : root ratio. The results of field and laboratory evaluation showed that soil health were categoried as a healthy soil and moderate healthy soil both for mineral and peat soils, respectively. Furthermore, similar categories were also obtained for evaluation of plant performance categories. No correlation was found between the soil performance indicatorcategory and the lettuce performance category.Keywords: Field indicator, laboratory indicator, lettuce growth indicator, soil health

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Valpassos, Maria Alexandra Reis, Kátia Luciene Maltoni, Ana Maria Rodrigues Cassiolato, and Ely Nahas. "Recovery of soil microbiological properties in a degraded area planted with Corymbia citriodora and Leucaena leucocephala." Scientia Agricola 64, no. 1 (February 2007): 68–72. http://dx.doi.org/10.1590/s0103-90162007000100010.

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The influence of reforestation was evaluated during two season periods (February and October) in sites planted with Corymbia citriodora and Leucaena_leucocephala through microorganism counts (bacteria, fungi, actinomycetes, and nitrite oxidizers) and microbial activity (respiratory and urease activities). An Atlantic forest and a bare soil site were used as controls. The general trends of the variables in the different soils were: Atlantic forest or L. leucocephala > C. citriodora > bare soil. The microbial populations in L. leucocephala and C. citriodora soils were significantly higher (P < 0.05) than that found in the bare soil. Similar results were obtained for respiratory and urease activities. The microbiological variables of the soil under L. leucocephala were comparable or even superior to that found under Atlantic forest. An improvement in the microbiological soil variables was observed in the soil under C. citriodora when compared to the soil without vegetation. These results can be attributed to an increasing amount of total organic C of the soils under L. leucocephala and C. citriodora in relation to the soil without vegetation. Although most results obtained in February presented higher values than in October, the sampling period did not have a consistent controlling influence on these variables.

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Börling, Katarina, Erasmus Otabbong, and Elisabetta Barberis. "Soil Variables for Predicting Potential Phosphorus Release in Swedish Noncalcareous Soils." Journal of Environment Quality 33, no. 1 (2004): 99. http://dx.doi.org/10.2134/jeq2004.0099.

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Börling, Katarina, Erasmus Otabbong, and Elisabetta Barberis. "Soil Variables for Predicting Potential Phosphorus Release in Swedish Noncalcareous Soils." Journal of Environmental Quality 33, no. 1 (January 2004): 99–106. http://dx.doi.org/10.2134/jeq2004.9900.

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Gambill, Daniel R., Wade A. Wall, Andrew J. Fulton, and Heidi R. Howard. "Predicting USCS soil classification from soil property variables using Random Forest." Journal of Terramechanics 65 (June 2016): 85–92. http://dx.doi.org/10.1016/j.jterra.2016.03.006.

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Barbosa-Moreno, Finlandia, Ignacio Sánchez Cohen, Gabriel Díaz Padilla, Rafael Alberto Guajardo Panes, and Rafael Rodríguez Hernández. "EQUATIONS BETWEEN CHEMICAL SOIL VARIABLES AND HYDRAULICCONDUCTIVITY AT SATURATION." Revista Chapingo Serie Zonas Áridas XII, no. 2 (December 2013): 77–84. http://dx.doi.org/10.5154/r.rchsza.2012.06.011.

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Kush, John S., Douglas G. Pitt, Phillip J. Craul, and William D. Boyer. "Quantifying Forest Soil Physical Variables Potentially Important for Site Growth Analyses." Southern Journal of Applied Forestry 28, no. 1 (February 1, 2004): 5–11. http://dx.doi.org/10.1093/sjaf/28.1.5.

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Abstract Accurate mean plot values of forest soil factors are required for use as independent variables in site-growth analyses. Adequate accuracy is often difficult to attain because soils are inherently widely variable. Estimates of the variability of appropriate soil factors influencing growth can be used to determine the sampling intensity required to secure accurate mean plot values. A study was conducted to determine the plot means and variation of bulk density, texture, and gross moisture weights within plots associated with the longleaf pine (Pinus palustris Mill.) forest type in south Alabama. Included in the study were three different soil series (Troup, Norfolk, and Esto), at each of three topographic positions (lower, mid, and upper slope). Soil texture was the most variable among the properties studied and gross moisture weights the least variable. Results provide a means of estimating forest soil sampling intensity for use in site growth analyses. South. J. Appl. For. 28(1):5–11.

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Bregt, A. K., H. J. Gesink, and Alkasuma. "Mapping the conditional probability of soil variables." Geoderma 53, no. 1-2 (May 1992): 15–29. http://dx.doi.org/10.1016/0016-7061(92)90018-3.

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13

Zhai, Qian, and Harianto Rahardjo. "Determination of soil–water characteristic curve variables." Computers and Geotechnics 42 (May 2012): 37–43. http://dx.doi.org/10.1016/j.compgeo.2011.11.010.

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GANESHAMURTHY, A. N. "Soil changes following long-term cultivation of pulses." Journal of Agricultural Science 147, no. 6 (June 23, 2009): 699–706. http://dx.doi.org/10.1017/s0021859609990104.

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SUMMARYStudies were conducted on Entisols to understand the effects of continuous pulse cultivation on soil chemical, physical and biological properties by comparing with continuous non-pulse crops and uncultivated soils. Soils of a Typic Ustochrept, developed from the same parent material, from 16-year-old pulse cultivation fields, non-pulse crop fields and uncultivated fallow fields in a location with uniform topography were analysed using a polyphasic approach combining traditional soil physical and chemical analysis, culture-dependent and independent microbiological analysis and enzymatic analysis. Among the soil physical properties, only soil aggregate stability and soil compaction showed significant improvement in soils under pulses than non-pulse crops. Compared to uncultivated fallows, the soil pH after pulse cultivation was about 1 unit lower while non-pulse crop cultivation reduced it by 0·36. The chemical and biological variables that contribute most to the discrimination of the pulses effect and non-pulse crops effect on soil quality are organic carbon (C), microbial biomass C, nitrogen (N) and biomass ninhydrin-N, and secondary variables related to N cycle:nitrate (NO3–N), organic and total soluble N. The enzyme activities were significantly higher in soils after pulse cultivation than after non-pulse crops or uncultivated fallow. The soil quality of pulse cultivation fields seems to be markedly different to that of non-pulse crop fields and uncultivated fallows in terms of all the variables studied.

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Landeta-Escamilla, Ofelia, Oscar Sandoval-Gonzalez, Albino Martínez-Sibaja, José Flores-Cuautle, Rubén Posada-Gómez, and Alejandro Alvarado-Lassman. "Intelligent Spectroscopy System Used for Physicochemical Variables Estimation in Sugar Cane Soils." Sensors 19, no. 2 (January 10, 2019): 240. http://dx.doi.org/10.3390/s19020240.

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The current condition of soils is a major area of interest due to the lack of certainty in their physicochemical properties, which can guarantee the quality and the production of a specific crop. Additionally, methodologies to improve land management must be implemented in order to address the consequences of many environmental issues. To date, many techniques have been implemented to improve the accuracy—and more recently the speed—of analysis, in order to obtain results while in the field. Among those, Near Infrared (NIR) spectroscopy has been widely used to achieve the objectives mentioned above. Nevertheless, it requires particular knowledge, and the cost might be high for farmers who own the fields and crops. Thus, the present work uses a system that implements capacitance spectroscopy plus artificial intelligence algorithms to estimate the physicochemical variables of soil used to grow sugar cane. The device uses the frequency response of the soil to determine its magnitude and phase values, which are used by artificial intelligence algorithms that are capable of estimating the soil properties. The obtained results show errors below 8% in the estimation of the variables compared to the analysis results of the soil in laboratories. Additionally, it is a portable system, with low cost, that is easy to use and could be implemented to test other types of soils after evaluating the necessary algorithms or proposing alternatives to restore soil properties.

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Mróz, Lucyna. "Between-population variation in plant performance traits and elemental composition of Colchicum autumnale L. and its relation to edaphic environments." Acta Societatis Botanicorum Poloniae 77, no. 3 (2011): 229–39. http://dx.doi.org/10.5586/asbp.2008.029.

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Variation in vegetative and reproductive performance and leaf mineral composition among 25 populations of <em>Colchicum autumnale</em> (meadow saffron) from soils derived from six parent materials (limestone, marl, sandstone, greenstone, melaphyre and serpentine) in southwestern Poland has been investigated. The plant size (PS), total le-af area (TLA), leaf shape (LS), number of fruits per plant (NFP), number of seeds per plant (NFP), total weight seed per plant (TWSP) were estimated, and concentrations of seventeen elements (N, P, K, Ca, Mg, Na, S, Fe, Mn, Cu, Zn, Pb, Cd, Ni, Co, Cr, Mo) were analyzed in leaf and soil samples. In soil samples, also soil pH, organic matter content and sand, silt and clay content were determined. All soils (except melaphyre soil) contained elevated levels of Cr. Concentrations of soil Ni and Zn, Pb, Cd in serpentinite soil and polluted marl soils (respectively) were significantly higher than those of other examined soils. Meadow saffron leaves from all sites (except marl sites) contained elevated levels of Cr, Co and Ni. Statistical analysis, carried out with principal component analysis (PCA) revealed that a good correlation exists between the element content in leaves and plant performance traits and soil environment. The leaf Ca content and NFP were correlated and were much higher in populations from metal (except Cr) and nutrient-poor marl soils than in those from metal (except Ni in serpentine soil)and nutrient moderate rich soils derived from melaphyre, greenstones, serpentinite, limestones and sandstones and in those from metal-rich and nutrient-poor polluted marl soils. Meadow saffron plants tended to take up higher amounts of N, P, K, Mn, Cu and Na and lower amounts of S and had much higher TLA in populations from sandstone soils than those in populations from serpentinite, melaphyre, greenstone, marl and limestone soils. The leaf Co, Ni, Cr, Mg concentrations were correlated and were much higher in populations from serpentinite, melaphyre, greenstone, polluted marl and limestone soils than those from marl and sandstone soils. The pattern of variation in NFP and TLA across the different soil types was the opposite of that for leaf N, Cu, Na, Ni, Mg and S concentrations. Redundancy analysis (RDA) enables identification of the soil variables that best explain the variance pattern of plant response. The variation explained by the soil variables (15 soil elements and soil pH) was high (79%). The forward selection of soil variables identified soil Co, Mo, Ni, Ca and Zn concentrations as significantly influencing the ordination plant traits. The variation explained by these selected variables was 55%. Thus the five soil variables appeared to be the main factors determining the pattern variation of vegetative, reproductive and nutrient traits of <em>Colchicum autumnale</em>.

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Qian, H., K. Klinka, and L. M. Lavkulich. "Relationship between color value and nitrogen in forest mineral soils." Canadian Journal of Soil Science 73, no. 1 (February 1, 1993): 61–72. http://dx.doi.org/10.4141/cjss93-006.

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To assess the extent to which moist color value of forest mineral soils supports their differentiation according to concentrations of mineralizable and total N, 239 samples of 0–30-cm mineral-soil layers were examined for the relationship between nitrogen measures and selected categorical climatic and soil variables. The best regression models, using soil color value (SCV), climate, soil moisture and soil texture as categorical variables, explained nearly 70% of the variation in both mineralizable and total N, with climate accounting for most of the variation. The results provided support for the present usage of SCV in estimating mineralizable and total N in forest soils but suggested improvements for the development of a more effective estimation procedure. Key words: Forest soil color, soil nitrogen, climate, soil moisture, soil texture, regression analysis

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Holland, Jonathan, Mark Conyers, Beverley Orchard, and Graeme Poile. "Soil potassium relationships, uptake efficiency and availability for six distinctive soils in central and southern New South Wales, Australia." Soil Research 52, no. 2 (2014): 129. http://dx.doi.org/10.1071/sr13171.

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Most soils in eastern Australian contain abundant soil potassium (K) reserves, and it is often assumed that there are no problems with soil K status. However, soil K deficiency has been reported in selected locations, and for viticulture, there are potential problems with high soil K concentrations due to the application of winery wastewater. This study investigated different soil K variables and plant variables for six soils with distinctive properties from across central and southern New South Wales to determine the presence of soil K deficiency and to understand the effect of adding K on the dynamics of soil K availability. A glasshouse experiment compared the selected soils under three fertiliser K rates with forage kale as the test species. Highly significant differences (P < 0.001) were found for soil and fertiliser K rate effects for three measures of soil K (solution K, soln K; exchangeable K, exch. K; tetraphenyl borate K; TBK). Significant soil and fertiliser rate effects were detected (P < 0.001 and P = 0.04 respectively) for the plant shoot (stem and leaf) biomass and nutrient uptake efficiency (UPE) index, but no plant K deficiency was detected; in fact, luxury K consumption was likely. Quantification of K efficiency indices (UPE and utilisation efficiency, UTE) demonstrated significant differences between the soils in the ease with which K was removed. This was illustrated by the negative correlation between both UPE and UTE with final exch. K. From soil properties potentially related to soil K variables, a significant linear regression relationship (P = 0.05) was found for TBK with illite and clay content. By contrast, a linear regression relationship between exch. K and illite content only was weaker (P = 0.09). These relationships show how soil properties (especially mineralogy) can predict soil K variables. A significant positive log–log relationship was found between exch. K or TBK for 37 Queensland soils and the same soil K measures from this study, consistent with this relationship. This relationship indicates that TBK can be effectively predicted from measuring exch. K for a wide range of soils across eastern Australia, but more research is required to understand the value of TBK to predict soil K availability.

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Rochette, Philippe, Chang Liang, David Pelster, Onil Bergeron, Reynald Lemke, Roland Kroebel, Douglas MacDonald, Weikai Yan, and Corey Flemming. "Soil nitrous oxide emissions from agricultural soils in Canada: Exploring relationships with soil, crop and climatic variables." Agriculture, Ecosystems & Environment 254 (February 2018): 69–81. http://dx.doi.org/10.1016/j.agee.2017.10.021.

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Zolfaghari, Z., M. R. Mosaddeghi, and S. Ayoubi. "Relationships of soil shrinkage parameters and indices with intrinsic soil properties and environmental variables in calcareous soils." Geoderma 277 (September 2016): 23–34. http://dx.doi.org/10.1016/j.geoderma.2016.04.022.

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Baretta, Dilmar, Marie Luise Carolina Bartz, Ivandro Fachini, Rafael Anselmi, Talyta Zortéa, and Carolina Riviera Duarte Maluche Baretta. "Soil fauna and its relation with environmental variables in soil management systems." Revista Ciência Agronômica 45, no. 5spe (2014): 871–79. http://dx.doi.org/10.1590/s1806-66902014000500002.

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Walsh, Stephen J. "RELATIONSHIP OF SELECTED BIOPHYSICAL VARIABLES TO SOIL MOISTURE AND SOIL TEMPERATURE VARIABILITY." Physical Geography 8, no. 3 (July 1987): 287–97. http://dx.doi.org/10.1080/02723646.1987.10642329.

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Vreulink, Jo-Marie, Annerina Esterhuyse, Karin Jacobs, and Alfred Botha. "Soil properties that impact yeast and actinomycete numbers in sandy low nutrient soils." Canadian Journal of Microbiology 53, no. 12 (December 2007): 1369–74. http://dx.doi.org/10.1139/w07-092.

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To explore the beneficial qualities or detrimental consequences of cultureable soil yeasts, it is important to understand which physicochemical soil properties most impact populations of these unicellular fungi in their natural habitat. The goal of this study was to determine which soil properties dictate yeast numbers in pristine sandy, low nutrient soils within a semi-arid region. A correlation matrix of the data obtained for 19 different environmental variables indicated a negative correlation between soil pH and yeast numbers. Using general regression models, it was demonstrated that soil pH and copper concentration were the 2 variables that correlated best with soil yeast counts in these soils. However, soil moisture content was found to be the environmental factor with the most impact on cultureable actinomycetes and heterotrophic microbes. The study also demonstrated that divalent cation availability might impact the size of both yeast and prokaryote populations in these soils.

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Reichenbach, Mario, Peter Fiener, Gina Garland, Marco Griepentrog, Johan Six, and Sebastian Doetterl. "The role of geochemistry in organic carbon stabilization against microbial decomposition in tropical rainforest soils." SOIL 7, no. 2 (August 2, 2021): 453–75. http://dx.doi.org/10.5194/soil-7-453-2021.

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Abstract. Stabilization of soil organic carbon (SOC) against microbial decomposition depends on several soil properties, including the soil weathering stage and the mineralogy of parent material. As such, tropical SOC stabilization mechanisms likely differ from those in temperate soils due to contrasting soil development. To better understand these mechanisms, we investigated SOC dynamics at three soil depths under pristine tropical African mountain forest along a geochemical gradient from mafic to felsic and a topographic gradient covering plateau, slope and valley positions. To do so, we conducted a series of soil C fractionation experiments in combination with an analysis of the geochemical composition of soil and a sequential extraction of pedogenic oxides. Relationships between our target and predicting variables were investigated using a combination of regression analyses and dimension reduction. Here, we show that reactive secondary mineral phases drive SOC properties and stabilization mechanisms together with, and sometimes more strongly than, other mechanisms such as aggregation or C stabilization by clay content. Key mineral stabilization mechanisms for SOC were strongly related to soil geochemistry, differing across the study regions. These findings were independent of topography in the absence of detectable erosion processes. Instead, fluvial dynamics and changes in soil moisture conditions had a secondary control on SOC dynamics in valley positions, leading to higher SOC stocks there than at the non-valley positions. At several sites, we also detected fossil organic carbon (FOC), which is characterized by high C/N ratios and depletion of N. FOC constitutes up to 52.0 ± 13.2 % of total SOC stock in the C-depleted subsoil. Interestingly, total SOC stocks for these soils did not exceed those of sites without FOC. Additionally, FOC decreased strongly towards more shallow soil depths, indicating decomposability of FOC by microbial communities under more fertile conditions. Regression models, considering depth intervals of 0–10, 30–40 and 60–70 cm, showed that variables affiliated with soil weathering, parent material geochemistry and soil fertility, together with soil depth, explained up to 75 % of the variability of SOC stocks and Δ14C. Furthermore, the same variables explain 44 % of the variability in the relative abundance of C associated with microaggregates vs. free-silt- and-clay-associated C fractions. However, geochemical variables gained or retained importance for explaining SOC target variables when controlling for soil depth. We conclude that despite long-lasting weathering, geochemical properties of soil parent material leave a footprint in tropical soils that affects SOC stocks and mineral-related C stabilization mechanisms. While identified stabilization mechanisms and controls are similar to less weathered soils in other climate zones, their relative importance is markedly different in the tropical soils investigated.

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Ghini, Raquel, and Marcelo Augusto Boechat Morandi. "Biotic and abiotic factors associated with soil suppressiveness to Rhizoctonia solani." Scientia Agricola 63, no. 2 (April 2006): 153–60. http://dx.doi.org/10.1590/s0103-90162006000200007.

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Crop management may modify soil characteristics, and as a consequence, alter incidence of diseases caused by soilborne pathogens. This study evaluated the suppressiveness to R. solani in 59 soil samples from a microbasin. Soil sampling areas included undisturbed forest, pasture and fallow ground areas, annual crops, perennial crops, and ploughed soil. The soil samples were characterized according to abiotic variables (pH; electrical conductivity; organic matter content; N total; P; K; Ca; Mg; Al; H; S; Na; Fe; Mn; Cu; Zn; B; cation exchange capacity; sum of bases and base saturation) and biotic variables (total microbial activity evaluated by the CO2 evolution and fluorescein diacetate hydrolysis; culturable bacterial, fungal, actinomycetes, protozoa, fluorescent Pseudomonas and Fusarium spp. communities). The contribution and relationships of these variables to suppression to R. solani were assessed by path analysis. When all samples were analyzed together, only abiotic variables correlated with suppression of R. solani, but the entire set of variables explained only 51% of the total variation. However, when samples were grouped and analyzed by vegetation cover, the set of evaluated variables in all cases accounted for more than 90% of the variation in suppression of the pathogen. In highly suppressive soils of forest and pasture/fallow ground areas, several abiotic variables and fluorescein diacetate hydrolysis correlated with suppression of R. solani and the set of variables explained more than 98% of suppressiveness.

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Pachepsky, Ya A., D. J. Timlin, and W. J. Rawls. "Soil Water Retention as Related to Topographic Variables." Soil Science Society of America Journal 65, no. 6 (November 2001): 1787–95. http://dx.doi.org/10.2136/sssaj2001.1787.

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Lark, R. M. "Modelling complex soil properties as contaminated regionalized variables." Geoderma 106, no. 3-4 (April 2002): 173–90. http://dx.doi.org/10.1016/s0016-7061(01)00123-9.

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Braimoh, Ademola K., Alfred Stein, and Paul L. G. Vlek. "IDENTIFICATION AND MAPPING OF ASSOCIATIONS AMONG SOIL VARIABLES." Soil Science 170, no. 2 (February 2005): 137–48. http://dx.doi.org/10.1097/00010694-200502000-00007.

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Boluwade, Alaba, and Chandra A. Madramootoo. "Geostatistical independent simulation of spatially correlated soil variables." Computers & Geosciences 85 (December 2015): 3–15. http://dx.doi.org/10.1016/j.cageo.2015.09.002.

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Shi, Jingjing, Lin Yang, A.-Xing Zhu, Chengzhi Qin, Peng Liang, Canying Zeng, and Tao Pei. "Machine-Learning Variables at Different Scales vs. Knowledge-based Variables for Mapping Multiple Soil Properties." Soil Science Society of America Journal 82, no. 3 (April 26, 2018): 645–56. http://dx.doi.org/10.2136/sssaj2017.11.0392.

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Tarr, Alison B., Kenneth J. Moore, Donald G. Bullock, Philip M. Dixon, and C. Lee Burras. "Improving Map Accuracy of Soil Variables Using Soil Electrical Conductivity as a Covariate." Precision Agriculture 6, no. 3 (June 2005): 255–70. http://dx.doi.org/10.1007/s11119-005-1385-9.

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Forootan, Elham. "Analysis of trends of hydrologic and climatic variables." Soil and Water Research 14, No. 3 (May 27, 2019): 163–71. http://dx.doi.org/10.17221/154/2018-swr.

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Assessing trends of hydrologic variables related to both hydrologic processes facilitates accurate water resources forecasting, especially in arid and semiarid regions with high evaporation and low rainfall volume. In this study, spatial and temporal trends of six hydrologic and climatic variables, viz. rainfall, evaporation, streamflow discharge, temperature, wind speed and relative humidity and also the ratio of annual potential evaporation to precipitation (E/P) were analysed at a monthly and annual scale. Moreover, the relationship of relative humidity, temperature, rainfall and wind speed trends with evaporation trend was investigated. Results of the study revealed the absence of significant temporal trend in precipitation, temperature and wind velocity for the majority of months, and the presence of upward trends in relative humidity and evaporation values as well as downward trend in streamflow discharge in some months. At an annual scale increasing evaporation and decreasing stream flow discharge trends were observed at most stations, which means that the region will be confronted with more severe drought conditions in future. Also, the result of Spearman’s rank coefficient revealed that the temporal evaporation trend is not related to wind speed, temperature, relative humidity and rainfall trend. Moreover, the spatial trend of climatic and hydrologic variables indicated the similarity of evaporation and relative humidity trend as well as wind speed and rainfall trend.

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Parmele, Victoria N., Donald G. Hodges, A. E. Luloff, and C. Tatersall Smith Jr. "Adoption of innovations by foresters: a case study of forest soils information in New Hampshire." Canadian Journal of Forest Research 23, no. 2 (February 1, 1993): 159–65. http://dx.doi.org/10.1139/x93-023.

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Identifying the factors that influence foresters to adopt management innovations is essential for developing models that accurately forecast the rate at which new technology will be adopted. Models were developed to evaluate the impact of sociodemographic characteristics, attitudes, and structural–external variables on New Hampshire foresters' decisions to adopt three distinct soil information sources. The soil information sources studied were County Soil Surveys, Important Forest Soils Groups, and Leak's Habitat Classification System. Discriminant analytic models were developed and evaluated for each information source. Information on use and other variables were collected by a mail survey with a response rate of approximately 60%. The results reveal that structural variables exerted the greatest influence on adoption decisions, while sociodemographic characteristics were the least important. College and noncollege sources of information about the innovations were the most important variables in the discriminant models. Other significant structural variables included employer, prior use of soils information, and participation in continuing education. All three models correctly classified more than 75% of the respondents, with one model classifying more than 90%. The difference in accuracy may be attributed to differences in information access among the three soils information sources.

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Pickering, C. M., and K. Green. "Vascular plant distribution in relation to topography, soils and micro-climate at five GLORIA sites in the Snowy Mountains, Australia." Australian Journal of Botany 57, no. 3 (2009): 189. http://dx.doi.org/10.1071/bt08133.

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As part of the Global Observation Research Initiative in Alpine Environments program, the relative contribution of abiotic variables in explaining alpine vegetation was determined for five summits on a spur of Mount Clarke in the Snowy Mountains, Australia. The composition of vascular plant species and life-forms, and topography were determined, and soil nutrients and soil temperature were measured on each aspect of each summit by standardised methods. Ordinations were performed on the composition of vascular plant species and life-forms, topography, soil nutrients and soil temperature-derived variables. Abiotic variables were tested against the biotic dissimilarity matrices to determine which were best correlated with current plant composition. Summits differed in plant composition, with a decrease in the cover of shrubs, and an increase in herbs and graminoids with increasing altitude. Altitude was the main determinant of species composition, accounting for more than 80% of the variation among summits. Soil temperature variables accounted for more than 40% of the variation in composition among summits. Soils were not significantly different among summits, although certain soil variables, principally calcium, were important in predicting plant composition. Because temperature is correlated with current vegetation on these five summits, predicted increased temperatures and decreased snow cover are likely to affect future plant composition in this mountain region.

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Le Bissonnais, Y., D. Blavet, G. De Noni, J. Y. Laurent, J. Asseline, and C. Chenu. "Erodibility of Mediterranean vineyard soils: relevant aggregate stability methods and significant soil variables." European Journal of Soil Science 58, no. 1 (February 2007): 188–95. http://dx.doi.org/10.1111/j.1365-2389.2006.00823.x.

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Colvin, D. L., B. J. Brecke, and E. B. Whitty. "Tillage Variables for Peanut Production." Peanut Science 15, no. 2 (July 1, 1988): 94–97. http://dx.doi.org/10.3146/i0095-3679-15-2-13.

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Abstract Effects of minimum tillage (MT) production techniques on peanut (Arachis hypogaea L.) root growth and yield were unknown. Field experiments were therefore conducted during 1984 near Williston and Marianna, FL and during 1985 near Williston and Jay, FL to evaluate effects of surface and subsurface tillage on peanut production. Soil types were a Zuber loamy sand (fine, mixed hyperthermic Ultic Hapludalf) at Williston, a Chipola sandy loam (loamy, siliceous, thermic Arenic Hapludult) at Marianna, and a Red Bay sandy loam (fine, loamy, siliceous, thermic Rhodic Paleudult) at Jay. The Sunrunner peanut cultivar was planted using a modified twin 23 cm row spacing and seeded at a rate of 140 kg/ha. Eight tillage systems that included combinations of conventional tillage, strip-tillage, and no-tillage with and without subsoiling or subsurface slitting were evaluated. Peanuts germinated and grew well except in no-tillage plots that received no subsurface tillage. Without surface or subsurface tillage there was not sufficient soil disturbance to insure proper seed-soil contact or seed cover. Generally, plots that received some degree of conventional tillage yielded better than plots with no surface preparation (4090 vs. 3760 kg/ha avg.). Minimum tillage plots yielded numerically less than conventional plots but in only a few cases were significant differences in yield noted. At most locations, minimum tillage plots that received no subsurface tillage developed a “lazy root syndrome” in which the few roots produced were quite shallow and grew near the soil surface. These treatments yielded less (3680 vs. 4010 kg/ha avg.) than those with conventional seedbed preparation or the minimum tillage treatments receiving subsurface tillage. Root strength and penetration measurements roughly reflect the same trends as peanut yields. The slit-tillage system resulted in peanut yields equal to or better than those obtained with chisel point subsoiling. Slitter wear and breakage problems were encountered but overall, the subsurface slit system appears to be a functional alternative to chisel point subsoiling.

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Harris, Ian W. E. "The response of invertebrate populations in three undisturbed soils in southwestern Ontario, Canada, to variations in local soil properties, seasonal changes, and climate." Canadian Field-Naturalist 127, no. 2 (October 24, 2013): 103. http://dx.doi.org/10.22621/cfn.v127i2.1441.

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Three distinctly different undisturbed mature forested sites at the northern limits of the Carolinian forest system in Lambton County, Ontario, were examined to test the hypothesis that the abundance of each order of soil invertebrates captured is dependent on a unique set of soil properties, seasonal changes, and climate variations. Sixteen independent variables were recorded over five consecutive years. With the exception of rainfall, air temperature, and soil temperature, means of the measured variables differed significantly (P < 0.05) among soils. Twenty-eight taxa of invertebrates were captured, of which Acari, Collembola, and Nematoda were most abundant. Only the mean of total abundance and the mean abundance of Acari, Nematoda, and Haplotaxida differed significantly (P < 0.05) among soils. Haplotaxida was the only taxon in all three soils found to be influenced significantly (P < 0.05) by seasonal variation. The usual mid-summer minimum in the abundance of Haplotaxida was latest and most clearly defined in the clay soil and earliest and least clearly defined in the sand soil. Regression analysis showed that each site is sufficiently separated in the factor space observed that the abundance of each invertebrate taxon is dependent on different combinations of local variables. The hypothesis was rejected.

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Wragg, Joanna, Mark Cave, Elliott Hamilton, and T. Lister. "The Link between Soil Geochemistry in South-West England and Human Exposure to Soil Arsenic." Minerals 8, no. 12 (December 4, 2018): 570. http://dx.doi.org/10.3390/min8120570.

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The aim of this research is to use the whole soil geochemistry and selected bioaccessibility measurements, using the BioAcessibility Research Group of Europe (BARGE) method, on the same soils to identify the geochemical controls on arsenic (As) bioaccessibility and to gain an understanding of its spatial distribution in south-west England. The total element concentrations of 1154 soils were measured with As concentrations ranging from 4.7–1948 mg·kg−1, with the bioaccessible As of 50 selected soils ranging from 0.6–237 mg·kg−1. A Self Modelling Mixture Resolution approach was applied to the total soil element chemistry to identify the intrinsic soil constituents (ISCs). The ISCs were used as predictor variables and As bioaccessibility as the dependant variables in a regression model for the prediction of As bioaccessibility at all soil locations to examine its regional spatial distribution. This study has shown that bioaccessibility measurements can be directly linked to the geochemical properties of soils. In summary, it seems the primary source of bioaccessible As comes from soils developed directly over the mineralised areas surrounding the granite intrusions. Secondary sources of bioaccessible As are derived from As that has been mobilised from the primary mineralised source and then re-absorbed onto clay material, Fe oxides and carbonate coatings. This information can be of direct use for land development, since land contamination can affect the health of people living, working, visiting or otherwise present on a site.

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Martin, M. P., M. Wattenbach, P. Smith, J. Meersmans, C. Jolivet, L. Boulonne, and D. Arrouays. "Spatial distribution of soil organic carbon stocks in France." Biogeosciences Discussions 7, no. 6 (November 18, 2010): 8409–43. http://dx.doi.org/10.5194/bgd-7-8409-2010.

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Abstract. Soil organic carbon plays a major role in the global carbon budget, and can act as a source or a sink of atmospheric carbon, whereby it can influence the course of climate change. Changes in soil organic soil stocks (SOCS) are now taken into account in international negotiations regarding climate change. Consequently, developing sampling schemes and models for estimating the spatial distribution of SOCS is a priority. The French soil monitoring network has been established on a 16 km × 16 km grid and the first sampling campaign has recently been completed, providing circa 2200 measurements of stocks of soil organic carbon, obtained through an in situ composite sampling, uniformly distributed over the French territory. We calibrated a boosted regression tree model on the observed stocks, modelling SOCS as a function of other variables such as climatic parameters, vegetation net primary productivity, soil properties and land use. The calibrated model was evaluated through cross-validation and eventually used for estimating SOCS for the whole of metropolitan France. Two other models were calibrated on forest and agricultural soils separately, in order to assess more precisely the influence of pedo-climatic variables on soil organic carbon for such soils. The boosted regression tree model showed good predictive ability, and enabled quantification of relationships between SOCS and pedo-climatic variables (plus their interactions) over the French territory. These relationship strongly depended on the land use, and more specifically differed between forest soils and cultivated soil. The total estimate of SOCS in France was 3.260 ± 0.872 PgC for the first 30 cm. It was compared to another estimate, based on the previously published European soil organic carbon and bulk density maps, of 5.303 PgC. We demonstrate that the present estimate might better represent the actual SOCS distributions of France, and consequently that the previously published approach at the European level greatly overestimates SOCS.

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40

Barros, Nieves. "Thermodynamics of Soil Microbial Metabolism: Applications and Functions." Applied Sciences 11, no. 11 (May 28, 2021): 4962. http://dx.doi.org/10.3390/app11114962.

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The thermodynamic characterization of soils would help to study and to understand their strategies for survival, as well as defining their evolutionary state. It is still a challenging goal due to difficulties in calculating the thermodynamic state variables (enthalpy, Gibbs energy, and entropy) of the reactions taking place in, and by, soils. Advances in instrumentation and methodologies are bringing options for those calculations, boosting the interest in this subject. The thermodynamic state variables involve considering the soil microbial functions as key channels controlling the interchange of matter and energy between soil and the environment, through the concept of microbial energy use efficiency. The role of microbial diversity using the energy from the soil organic substrates, and, therefore, the who, where, with whom, and why of managing that energy is still unexplored. It could be achieved by unraveling the nature of the soil organic substrates and by monitoring the energy released by the soil microbial metabolism when decomposing and assimilating those substrates. This review shows the state of the art of these concepts and the future impact of thermodynamics on soil science and on soil ecology.

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Li, Wugang, Wenhua Liu, Zhijia Xue, and Xiuli Sun. "A Constitutive Model for Overconsolidated Structured Soils Using Structural Variable." Shock and Vibration 2021 (August 9, 2021): 1–14. http://dx.doi.org/10.1155/2021/5530038.

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Due to the influence of soil structure, structured soils exhibit significantly different mechanical behavior compared to the reconstituted soils having the same material. In this work, a theoretical analysis focusing on the mechanical behavior of structured soils is presented. Based on the mechanical behavior of the structured soil, a newly defined variable structural index was used as a measurement of the integrity of soil structure based on the concept of intrinsic compression line of intact structured soils. Furthermore, a novel correlation for the variation in volume of structured soils is established using effective stress and newly defined structural index as the constitutive variables. The novel correlation provided interpretation about the mechanism of compression behavior of the structured soils. Afterwards, the proposed correlation for the variation in volume was extended to triaxial stress state in the framework of subloading surface to include the effect of overconsolidation. Comparisons between the predictions and experimental results validated the proposed constitutive model for structured soils.

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Tremblay, Sylvie, Rock Ouimet, and Daniel Houle. "Prediction of organic carbon content in upland forest soils of Quebec, Canada." Canadian Journal of Forest Research 32, no. 5 (May 1, 2002): 903–14. http://dx.doi.org/10.1139/x02-023.

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Soil organic carbon (C) is an important component of forest carbon pools and should be taken into account in sustainable forest management. However, there is a need to derive indicators for this attribute, as organic C content (Mg·ha1) in forest soils is generally not available in Quebec survey data. Thus, we developed models to predict organic C accumulation in the forest floor and in mineral soils of upland forest soils (i.e., with forest floor thickness [Formula: see text]30 cm) using soil survey data as input variables. The best-fit model for predicting forest floor organic C content consisted of the explanatory variables forest floor thickness, latitude, and longitude. The model R2 was 0.76, and its CV was 28%. The second best-fit model, excluding geographical coordinates, included forest floor thickness and mean growing season precipitation as explanatory variables (R2 = 0.71, CV = 29.5%). The model for predicting mineral soil organic C content was composed of two submodels: (i) organic C concentration of a mineral horizon as a function of its colour and (ii) bulk density of that horizon as a function of its estimated C concentration (obtained from the former model). The R2 of the model for predicting organic C content in mineral soils was 0.57, and its CV was 29%. The models were used to predict organic C contents in 5547 pedons, dispersed throughout the commercial forest of Quebec and for which basic soil profile description data were available. It was then possible to evaluate and compare mean soil C accumulation in different forest stand types and to construct two maps of soil organic C accumulation in upland forest soils of southern Quebec. The results pointed out that forest floor thickness combined with mineral soil horizon colour, texture class, and pH would be useful sustainable forest management indicators of organic C accumulation in upland forest soils.

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Szabó, Brigitta, Melanie Weynants, and Tobias K. D. Weber. "Updated European hydraulic pedotransfer functions with communicated uncertainties in the predicted variables (euptfv2)." Geoscientific Model Development 14, no. 1 (January 12, 2021): 151–75. http://dx.doi.org/10.5194/gmd-14-151-2021.

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Abstract. Soil hydraulic properties are often derived indirectly, i.e. computed from easily available soil properties with pedotransfer functions (PTFs), when those are needed for catchment, regional or continental scale applications. When predicted soil hydraulic parameters are used for the modelling of the state and flux of water in soils, uncertainty of the computed values can provide more detailed information when drawing conclusions. The aim of this study was to update the previously published European PTFs (Tóth et al., 2015, euptf v1.4.0) by providing prediction uncertainty calculation built into the transfer functions. The new set of algorithms was derived for point predictions of soil water content at saturation (0 cm matric potential head), field capacity (both −100 and −330 cm matric potential head), wilting point (−15 000 cm matric potential head), plant available water, and saturated hydraulic conductivity, as well as the Mualem–van Genuchten model parameters of the moisture retention and hydraulic conductivity curve. The minimum set of input properties for the prediction is soil depth and sand, silt and clay content. The effect of including additional information like soil organic carbon content, bulk density, calcium carbonate content, pH and cation exchange capacity were extensively analysed. The PTFs were derived adopting the random forest method. The advantage of the new PTFs is that they (i) provide information about prediction uncertainty, (ii) are significantly more accurate than the euptfv1, (iii) can be applied for more predictor variable combinations than the euptfv1, 32 instead of 5, and (iv) are now also derived for the prediction of water content at −100 cm matric potential head and plant available water content. A practical guidance on how to use the derived PTFs is provided.

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Cotching, W. E., G. Oliver, M. Downie, R. Corkrey, and R. B. Doyle. "Land use and management influences on surface soil organic carbon in Tasmania." Soil Research 51, no. 8 (2013): 615. http://dx.doi.org/10.1071/sr12251.

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The effects of environmental parameters, land-use history, and management practices on soil organic carbon (SOC) concentrations, nitrogen, and bulk density were determined in agricultural soils of four soil types in Tasmania. The sites sampled were Dermosols, Vertosols, Ferrosols, and a group of texture-contrast soils (Chromosol and Sodosol) each with a 10-year management history ranging from permanent perennial pasture to continuous cropping. Rainfall, Soil Order, and land use were all strong explanatory variables for differences in SOC, soil carbon stock, total nitrogen, and bulk density. Cropping sites had 29–35% less SOC in surface soils (0–0.1 m) than pasture sites as well as greater bulk densities. Clay-rich soils contained the greatest carbon stocks to 0.3 m depth under pasture, with Ferrosols containing a mean of 158 Mg C ha–1, Vertosols 112 Mg C ha–1, and Dermosols 107 Mg C ha–1. Texture-contrast soils with sandier textured topsoils under pasture had a mean of 69 Mg C ha–1. The range of values in soil carbon stocks indicates considerable uncertainty in baseline values for use in soil carbon accounting. Farmers can influence SOC more by their choice of land use than their day-to-day soil management. Although the influence of management is not as great as other inherent site variables, farmers can still select practices for their ability to retain more SOC.

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Hu, Chenxia, Alan Wright, and Gang Lian. "Estimating the Spatial Distribution of Soil Properties Using Environmental Variables at a Catchment Scale in the Loess Hilly Area, China." International Journal of Environmental Research and Public Health 16, no. 3 (February 10, 2019): 491. http://dx.doi.org/10.3390/ijerph16030491.

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A comprehensive understanding of the spatial distribution and dynamic changes of soil properties are the basis for sustainable land management. Topography and land use types are key factors affecting soil property variability. This study analyzed the effects of land use types and landscape locations on soil properties, based on data from 111 points of surface soil (0–20 cm) in the Zhujiagou catchment on the Loess Plateau of Northwest China. Soil properties include clay, silt, bulk density (BD), soil organic matter (SOM), total nitrogen (TN) and total phosphorus (TP). Land use types include slope farmland (SFL), terrace farmland (TFL), check-dam farmland (CDL), woodland (WL), shrub land (SL) and grassland (GL). Landscape locations include crest (CT), upper slope (US), middle slope (MS), lower slope (LS) and flat valley (FV). Topographical attributes were divided into primary and secondary (or compound) attributes. Correlation analyses were carried out between soil properties and terrain attribute, and multiple-linear regression models were established to estimate soil properties using land use types and topographic attributes as independents. Results indicated that significant differences in soil properties existed between six land use types, except for bulk density. Higher values of clay, silt, SOM and TN occurred in soils from check-dam farmland, but lower values in soils from shrub land. Significant differences among landscape positions were observed for clay, BD, SOM and TN. Clay, SOM and TN contents on flat valley (FV) positions were higher than those of other positions. Different correlations were found between soil properties and terrain attributes. The regression models explained 13% to 63% of the variability of the measured soil properties, and the model for Clay had the highest R2 value, followed by TN, silt, BD, SOM and TP. Validation results of the regression models showed that the model was precise for soil bulk density, but the variation was large and a high smoothing effect existed for predicted values of other soil properties. For TP, the predicted result was poor. Further observations suggested that land use was the dominant factor affecting soil chemical properties. But for soil physical properties, especially for BD, topography was the dominant factor.

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Venteris, E. R., G. W. McCarty, J. C. Ritchie, and T. Gish. "INFLUENCE OF MANAGEMENT HISTORY AND LANDSCAPE VARIABLES ON SOIL ORGANIC CARBON AND SOIL REDISTRIBUTION." Soil Science 169, no. 11 (November 2004): 787–95. http://dx.doi.org/10.1097/01.ss.0000148742.75369.55.

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Montalvo, Arlee M., Paul A. McMillan, and Edith B. Allen. "The Relative Importance of Seeding Method, Soil Ripping, and Soil Variables on Seeding Success." Restoration Ecology 10, no. 1 (March 2002): 52–67. http://dx.doi.org/10.1046/j.1526-100x.2002.10106.x.

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PINTO, J. R. R., A. T. OLIVEIRA-FILHO, and J. D. V. HAY. "INFLUENCE OF SOIL AND TOPOGRAPHY ON THE COMPOSITION OF A TREE COMMUNITY IN A CENTRAL BRAZILIAN VALLEY FOREST." Edinburgh Journal of Botany 62, no. 1-2 (March 2005): 69–90. http://dx.doi.org/10.1017/s0960428606000035.

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The purpose of the present study was to investigate the correlations between environmental variables related to the substrate (soil and topography) and the distribution of tree species in a valley forest in the Chapada dos Guimarães National Park, Mato Grosso State, Brazil. The forest lies in the Cerrado Domain of Central Brazil where the dominant vegetation cover is cerrado (woody savanna). A survey of the tree community registered all live individuals with circumference at breast height (cbh)≥15cm found in eighteen 600m2 plots (total area 1.08ha). The substrate variables used in the gradient analyses were obtained from a topographic survey and from analyses of the chemical and physical properties of soil samples. A principal components analysis of soil and topography variables and a canonical correspondence analysis of the species–environment relationships produced similar results, separating both the substrate variables and the tree species abundances, mainly according to the two types of bedrock, sandstone or slate, underlying their soils, and secondly to the three topographic sectors recognized: Streamside, Mid Slope and Upper Slope. The differences in soil fertility and texture (related to the bedrocks) and the soil water regime (related to both soil texture and topography) were probably the chief factors determining the distribution of tree species in the forest.

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Martin, M. P., M. Wattenbach, P. Smith, J. Meersmans, C. Jolivet, L. Boulonne, and D. Arrouays. "Spatial distribution of soil organic carbon stocks in France." Biogeosciences 8, no. 5 (May 4, 2011): 1053–65. http://dx.doi.org/10.5194/bg-8-1053-2011.

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Abstract. Soil organic carbon plays a major role in the global carbon budget, and can act as a source or a sink of atmospheric carbon, thereby possibly influencing the course of climate change. Changes in soil organic carbon (SOC) stocks are now taken into account in international negotiations regarding climate change. Consequently, developing sampling schemes and models for estimating the spatial distribution of SOC stocks is a priority. The French soil monitoring network has been established on a 16 km × 16 km grid and the first sampling campaign has recently been completed, providing around 2200 measurements of stocks of soil organic carbon, obtained through an in situ composite sampling, uniformly distributed over the French territory. We calibrated a boosted regression tree model on the observed stocks, modelling SOC stocks as a function of other variables such as climatic parameters, vegetation net primary productivity, soil properties and land use. The calibrated model was evaluated through cross-validation and eventually used for estimating SOC stocks for mainland France. Two other models were calibrated on forest and agricultural soils separately, in order to assess more precisely the influence of pedo-climatic variables on SOC for such soils. The boosted regression tree model showed good predictive ability, and enabled quantification of relationships between SOC stocks and pedo-climatic variables (plus their interactions) over the French territory. These relationships strongly depended on the land use, and more specifically, differed between forest soils and cultivated soil. The total estimate of SOC stocks in France was 3.260 ± 0.872 PgC for the first 30 cm. It was compared to another estimate, based on the previously published European soil organic carbon and bulk density maps, of 5.303 PgC. We demonstrate that the present estimate might better represent the actual SOC stock distributions of France, and consequently that the previously published approach at the European level greatly overestimates SOC stocks.

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Karahan, Gülay, and Sabit Erşahin. "Relating Macropore Flow to Soil Parametric and Morphological Variables." Soil Science Society of America Journal 81, no. 5 (August 31, 2017): 1014–24. http://dx.doi.org/10.2136/sssaj2016.10.0327.

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Journal articles on the topic 'Soil variables'

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