Soil Units Research Articles

Soil and rhizosphere bacteriobiome of wheat under combined humate and fly ash application

The aim of the study was to exmine the effct of low rate of potassium humate application with and without fly ash (FA) on wheat roots rhizosphere bacteriobiome. Location and time of the study. The microplot field experiment was conducted in three replicates in randomized design in 2022 in Novosibirsk (Russia). Methods. Soil physical and chemical properties were determined by commonly used methods. Bacteriobiome structure and diversity were estimated by 16S rRNA genes (V3-V4 region) by metabarcoding. Results. The study revealed large bacteriobiome diversity: on average 2472 and 2330 operational taxonomic units (OTU) in bulk and rhizosphere soil< respectively. Overall 9120 OTE were found, belonging to 929 genera, 438 families, 416 orders, 104 classes and 37 phyla. A quarter of the total OTUs number belonged to the Proteobacteria phylum; Actinobacteria phylum ranked second in OTUs number (10%), whereas Firmicutes, Bacteroidetes and Acidobacteria each accounted for 8% of the total OTUs number. The Actinobacteria dominated in the relative abundance of the total number of sequence reads (38–41%), with Proteobacteria (25–28%) and Acidobacteria (10–13%) following. The treatment with potassium humate without fly ash did not influence the relative abundance of genera in the bulk soil, but increased twofold the relative abundance of the genus when combined with FA. In the rhizosphere soil bacteriobiome potassium humate without FA increased the Nocardioides relative abundance 1.8 times, whereas in combination with FA increased Sphingomonas and decreased Spartobacteria_gis relative abundance. Conclusions. Potassium humate treatment at a low rate resulted in small, but positive changes in soil and rhizosphere bacteriobiome despite the huge bacterial diversity, inherent for practically any soil, including the one used in this study. The effect of exogenic humate treatment involves a complex of various mechanisms, and detailed physiological and biochemical studies and meta-analysis of the published data are needed to understand the effect of low rate humate application on soil, plans and microorganisms.

Influence of hand trimming and bunch feeding of nutrient on yield and yield attributes of banana cv. Grand Naine

A field experiment was conducted during the year 2018-19 and 2019-20 at Instructional Farm, ACH, and Soil and Water Management Research Unit Navsari Agricultural University, Navsari (Gujarat) to assess the effect of hand trimming and bunch feeding on yield and yield attributes parameters of banana cv. Grand Naine. The investigation comprised of ten treatments and each treatment was repeated thrice in CRD. The treatments viz. Control (T1), KNO3 1% without trimming (T2), KNO3 2% without trimming (T3), SOP 1.5% without trimming (T4), SOP 2.0% without trimming (T5), KNO3 1% with trimming of one apical hand (T6), KNO3 2.0% with trimming of one apical hand (T7), SOP 1.5% with trimming of one apical hand (T8), SOP 2.0% with trimming of one apical hand (T9) and 300g cowdung slurry + 10g SOP +20g ammonium sulphate (T10) were imposed on banana plants of cultivar ‘Grand Naine’. Banana bunch feeding with 300g cow dung slurry + 10g SOP + 20g ammonium sulphate recorded the maximum bunch weight, fruit yield, weight of 3rd hand, finger length, finger girth and finger weight in the pooled study.

亚热带退化森林不同恢复方式对土壤团聚体胶结物质及稳定性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 亚热带退化森林不同恢复方式对土壤团聚体胶结物质及稳定性的影响 DOI: 10.5846/stxb202204211092 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(32001298); 湖北省教育厅重点项目(D20201001); 大学生创新训练项目(S202110512085) Effects of different restoration approaches of subtropical degraded forests on bonding materials and stability of soil aggregate Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:退化森林的恢复一直是林业和生态学研究的热点。良好的森林土壤结构有助于林木生长发育,作为土壤最基本的结构单元,土壤团聚体组成和稳定性是衡量土壤肥力和质量的重要指标,其团聚结构的形成依靠土壤胶结物质。然而,土壤胶结物质与团聚体稳定性之间的关系尚不确定。为探明亚热带退化森林的不同恢复方式对团聚体稳定性的影响及其潜在机制,以自然恢复的次生林为对照(CK),选取了亚热带三种常见的人工林:一代杉木林(P1)、二代杉木林(P2)和黄山松林(P3),测定土壤团聚体稳定性及其胶结物质的含量,并分析了各胶结物质对团聚体稳定性的影响。研究发现:不同森林恢复方式显著影响了土壤pH值、碳氮比、速效磷含量、团聚体的组成和稳定性。所有森林类型中,三种人工林的团聚体稳定性显著高于CK,P2的大团聚体所占比例最大,团聚体稳定性最高。恢复方式显著影响了土壤游离氧化铁含量、菌根密度和易提取球囊霉素相关土壤蛋白(EEG)含量。团聚体稳定性与游离氧化铁含量、菌根密度呈正相关,但与EEG含量呈负相关。研究结果表明,亚热带退化森林的人工恢复比自然恢复更有助于增强土壤团聚体稳定性,土壤游离氧化铁、菌根密度和EEG是显著影响团聚体稳定性的胶结物质。 Abstract:The restoration of degraded forest has been a hot topic in forestry and ecology. As a basic structural unit of soil, soil aggregate composition and stability are important indicators of soil fertility and quality, and the formation of soil aggregate relies on aggregate bonding materials. However, the relationship between aggregate bonding materials and aggregate stability is uncertain. To explore the effects of different restoration approaches of degraded subtropical forests on aggregate stability and its underlying mechanisms, we compared the secondary forest (natural restoration) as a control (CK), with three different common subtropical plantations which were: (1) first-generation Cunninghamia lanceolata (P1), (2) second-generation C. lanceolata (P2), and a Pinus. taiwanensis plantation (P3). We measured the aggregate stability and the contents of different aggregate bonding materials, and then analyzed the influence of these materials on soil aggregate stability. Results showed that forest restoration approach significantly affected soil pH, C/N, available phosphorus, as well as the composition and stability of aggregate. Among all the forests, the aggregate stability was significantly lower in CK than in the other three plantations, and P2 had the greatest proportion of large aggregates and the highest aggregate stability. The forest restoration approach also significantly affected soil free Fe oxide content, mycorrhizal density, and easily extractable glomalin-related soil protein (EEG). Aggregate stability was positively correlated with free Fe oxide content and mycorrhizal density, but negatively correlated with EEG. For subtropical degraded forests, the results indicated that artificial restoration was better than natural restoration to enhance soil aggregate stability, with soil free Fe oxide, mycorrhizal density and EEG being the main bonding materials that significantly affected the aggregate stability. 参考文献 相似文献 引证文献

PENGARUH APLIKASI KOMPOS TEA FLUFF DAN Azotobacter sp. TERHADAP SIFAT FISIK TANAH DAN PERTUMBUHAN BIBIT PADA PERSEMAIAN TEH

The tea plantation industry in West Java is experiencing problems with the degradation of organic matter, which can be seen from the decrease in organic C in the Bandung area and the large amount of factory solid waste produced every day. The provision of solid tea fluff as organic matter by composting can be a solution to improve the physical properties of the soil in tea plantations, and it is necessary to provide indigenous microbes to maximize plant growth in the form of Azotobacter sp. This study used a factorial randomized block design with two factors, namely soil media 100% topsoil + 0% tea fluff (F0), 70% topsoil + 30% tea fluff (F1), 60% topsoil + 40% tea fluff (F2). ), 50% topsoil + 50% tea fluff (F3), 40% topsoil + 60% tea fluff (F4), 30% topsoil + 70% tea fluff (F5) with an additional dose of Azotobacter sp. 0 mL (A0) and 3 mL (A1). The results for the soil unit weight parameter were significantly different (p<0.05), and there was an interaction between the soil media treatments and Azotobacter sp. all treatments experienced a decrease in bulk density, while the porosity parameter was not significantly different. However, for plant parameters, the F0A0 treatment showed better results than other treatments on the initial growth of tea seedlings.

Chronostratigraphy of the Periglacial Loess-Paleosol Sequence in Zaprężyn, SW Poland

Abstract Loess-paleosol sequences (LPS) are an exceptional source of palaeoclimate data constituting an indirect record of changing environmental and climatic conditions that prevailed during loess deposition and early diagenesis. The Zaprężyn LPS (17°11′52″E, 51°14′44″N) is situated in the southern morphological edge of the Trzebnica Hills. This sequence provides an opportunity to reconstruct past climate conditions in this part of SW Poland. In this work, we used two sets of optically stimulated luminescence (OSL) dating from the Gliwice and Bayreuth laboratory to establish a chronological framework for this profile. The results of 14C accelerator mass spectrometry (AMS) dating were also used. The dating results are accompanied by detailed analyses of grain-size distribution and colour. The applied methodology allowed us to distinguish four litho-pedotratigraphic units: modern soil S0, L1LL1 loess unit, L1LL2 loess unit and fossil S1 soil. The OSL dating results indicate an unconformity representing a time interval >30 ka between the L1LL1 and L1LL2 units. This unconformity explains the lack of a L1SS1 soil unit. In Zaprężyn LPS, the presence of the ice wedge pseudomorph in L1LL2 loess unit was recorded. Ice wedge pseudomorph approves the presens the permafrost conditions during the Lower Plenivistulian in Trzebnica Hills.

Growth performance of water spinach Ipomoea aquatica and freshwater prawn Macrobrachium rosenbergii grown in aquaponic and hydroponic units

In the present study, attempts were made to optimise water spinach (Ipomoea aquatica) in combination with freshwater prawns (Macrobrachium rosenbergii) to be grown under aquaponics culture conditions, especially as an indoor set-up suitable for urban dwellings. A comparison of the morphometric parameters such as linear growth and number of leaves of plants and the survival rate under the soil, aquaponics, aquarium and hydroponics units simultaneously per cycle was done to establish the stability of the system. The water spinach grown under the aquaponics set-up showed significant growth compared to the hydroponics set-up but was less than that of the soil units. Significantly higher growth of freshwater prawns was also recorded in the aquaponics unit compared to the aquarium unit. Though further investigations are still needed to find factors that can give optimum produce, the researchers propose that standardised aquaponic units for water spinach and freshwater prawns can be a safe option for urban households as a sustainable farming practice. Keywords: Food security, Hydroculture, Symbiotic growth, Urban farming

Editorial

Wetlands are prevalent in all types of landscapes around the world and constitute landforms, soil units, water features and faunal and floral communities. Wetlands sustain flora and fauna in the surface layer and they are dynamic and changing as such are reffered to as living landforms. Wetlands provide natural solutions for achieving “the Paris Climate Goals, Global Biodiversity Framework, and Sustainable Development Goals”. Unfortunately wetlands have not received due attention by geologists even though geology and geological processes are at the baseline for their evolution and development. The main reason is a poor understanding of wetland landforms. Wetlands can develop only in regions where water accumulates, and the underlying surface/bed rock is impervious. They constitute unusual landforms developed by biogenic materials (solid materials, biological or organic mostly peat, gas and water) predominantly formed by biological processes.

Tree and stand growth differ among soil classes in semi-natural forests in central Europe

We determined the size of differences in stand and tree growth in semi-natural forests with respect to 16 reference soil groups. The forest area of Slovenia (11.8 thousand km2) was used as the study area, and reference soil units were derived from the national soil map at a 1:25,000 scale consisting of 10,781 polygons with an average size of 117.95 ha. Stand growth was defined as periodic stand basal area increment, while the growth of Norway spruce, silver fir, Scots pine, European beech and sessile oak trees was estimated by the periodic diameter increment of 238,349 dominant trees on 67,061 permanent sampling plots. A linear fixed-effects model and linear mixed-effect models were used for studying stand and tree growth in different site, stand and tree conditions. The soil unit was the dummy variable with Dystric Cambisols set as the reference category. Soil contributed 4.3 % to the explained variability of basal area increment and 4–27 % to the explained variability of the diameter increment of the five tree species. Soil was a stronger driver of stand and tree growth than climate or topography. Stand and tree species production rate on soil units was in the interval of −28 % to +5 % and −47 % to +14 % of that on the reference soil unit, respectively. Stand growth was the highest on Eutric Gleysols and the lowest on Histosols, and tree species generally exhibited the highest and the lowest growth rates on different soil units. We suggest that soil should be considered in growth models and studied interrelatedly with climatic, site and stand variables.

Characterization and Classification of Toposequence Soils Units in The Zakhikha Region, West of Ramadi- Western Iraq

Depending on the geomorphological map and digital elevations of the Zakhikha area, five sites that differ in topography and geomorphology and represent the soil units present in the area were selected.Their locations are geographically defined and locally represented pedons are excavated,disturbed soil samples representing each diagnosed horizon were obtained from them, and transferred to the laboratory for the purpose of conducting some physical measurements and chemical analyzes on them. The soils were classified according to the American classification for the year 2014 for the family level. So that we completed the classification to the level of the series according to the Al-Agidi proposal of 1976 and 1981 for sedimentary and developed soils respectively. To study the effect of the geomorphological site on soil characteristics in the topographical sequence.The results showed a significant effect of the geomorphological location on the morphological characteristics of the soil, the class of texture, and some soil chemical characteristics. Classically, the Entisols order was formed most of the soils of the region, with the TW415 (12.79%) and DE31(18.19) series which diagnosed within the foot slope and Toe slope units. As for the Aridisols order it constituted a smaller percentage of the total area of the study area, with a person under two sub order there are Calcids (14.82%) and Gypsids (21.76%), with a person under three sub great soil groups there are Typic Calcigypsids, Typic Haplocalcids and Typic Argigypsids.

The state of agrocenosises and hayfield meadows in farm units of Prialeisk soil and climate zone (Altai Krai)

The state of agrocenosises and hayfield meadows in farm units of Prialeisk soil and climate zone (Altai Krai)

Improved analytical solution of lateral soil restraint for pipes buried in dry sand considering arching effects

Abrupt transverse ground movements induced by landslide, strike-slip offset, and excavation can exert excessive soil restraints on buried pipes and threaten the pipe safety. The determination of lateral soil restraint is, therefore, a key factor for the evaluation of buried pipes in such areas. However, effective analysis solutions to assess the area of failure zone of surrounding soils and to estimate the soil resistance on pipes are still limited. In this work, an improved implicit limit equilibrium model is proposed to calculate the ultimate lateral soil restraint of buried pipes in dry sand, in which the effect of active soil wedge is considered, and the heights of equal settlement plane in both passive and active wedges can be estimated. Comparisons are made between collected physical modeling results and calculations from different methods. Results show that the proposed method yields a better approximation to the measured data. Parametric studies are subsequently conducted, which illustrate that the ultimate soil lateral restraint is influenced by the pipe diameter, internal friction angle, and constrained modulus of soil. The influence of effective soil unit weight is minimal. The proposed method is beneficial for safety evaluation of buried pipes subject to lateral dragging.

Calibration of the capacitance probe for soil moisture monitoring

To obtain efficient use of water applied in irrigation, it is necessary to understand the dynamics of water in the soil, which is an important factor in agriculture. The aim of this study was to determine models for calibration and to evaluate thelysimetry methodwith undisturbed samples,using a capacitance probe for monitoring the moisture content of a TypicHapluderts soil under laboratory conditions. The predominant soil in the study area is from the TypicHapluderts soil unit. The soil samples were collected with undisturbed samples, in layers of 0 - 10 cm and 10 - 20 cm depth from the surface, using PVC pipes with a diameter of 315 mm and 600 mm height. The determination of the variation in soil moisture was carried out by weight difference (weighing lysimetry method). The measurements with a Frequency Domain Reflectometry (FDR) were made on a daily frequency and 6 repetitions per measurement. Analyzed calibration models (linear, potential and quadratic), was performed the Shapiro-Wilk normality test. The methodology used provided satisfactory results, with multiple repetitions being performed on the same sample. The model that showed greater precision and better fit for the two profiles under study was the quadratic model.

The Shadow Values of Soil Hydrological Properties in the Production Potential of Climatic Regionalization of the Czech Republic

The Czech Republic uses a dual system of agricultural land prices, namely the formal/official price—for tax purposes—and the market price in the case of a standard sale or purchase of farmland. This paper focuses on the construction of an econometric model to quantify the influence of soil hydrological characteristics on the production potential in a given climatic region. It also focuses on the use of this model for the determination of the official price of agricultural land, which is expressed on the basis of the code of the evaluated soil-ecological unit (ESEU) and based on defined soil characteristics. The pricing itself is based on the production potential of the land, which in practice is very important for spatial planning, as it determines the classes of agricultural land protection with regard to the possibility of setting aside agricultural land for non-productive purposes or for drawing subsidies for less favourable areas. In this context, the non-productive functions of agricultural land are also frequently discussed, especially its retention, which plays a very important role in the currently changing climatic conditions. There are a number of studies on soil retention, and numerous approaches to measuring it, but none of them address its impact on production potential and thus on the price of land. For this reason, this paper focuses on defining the influence of the retention of the main soil units (defined for the conditions of the Czech Republic) on production potential. For this definition, SUR models are used, where the endogenous variable is expressed as production potential and the exogenous variables include the basic soil characteristics such as grain size, porosity, hydrological component of the soil, and retention. The obtained outputs show both the high explanatory power of the model and the adequate parametric significance of most variables, which provides sufficient support for the use of the results in practice. In addition, the estimated models across all climatic regions are consistent with substantively logical assumptions about the link between production potential and soil hydrological properties, which secondarily demonstrates their applicability in practice, especially for state administration, but also for local government in the sense of municipalities, cities, and other organizational units.

Influence of arable land location incorporating its roughness on blue-sky albedo variation

This paper quantifies the albedo variation in global bare, arable land, as one of the components of the Earth's land surface, that occurs over relatively short periods of the year but over a large total area. The study focused on the impact of the location of the land's dominant soil units, incorporating their roughness in their diurnal albedo (α) variation on the shortest (SDOY) and longest (LDOY) days of the year, and on their mean diurnal albedo (αd) values throughout the year under clear-sky conditions. Specialized software was used to generate the aforementioned soil albedo values on the basis of soil reflectance spectra stored in a soil database. It was assumed that the air-dried soil surfaces being tested would present extremely different roughness states: very high, corresponding to those shaped by a plow (Pd), and very low, corresponding to a smoothing harrow (Hs). It was found that the farther the surfaces were from the equator, the higher the minimum α values would be on the SDOY, and the lower they would be on the LDOY. It was determined that the relative difference (AVαd) between the highest and lowest values of αd for the studied surfaces located within the latitude range of ±15° would be close to 0%. For latitudes within ±20°–±30°, the AVαd values would be 6 and 5% for surfaces shaped by Pd and Hs, respectively. For those at about 65°, AVαd values would even reach 63% and 54%, respectively. The α values of soil surfaces generated from many thousands of reflectance spectra collected in soil databases around the world, and taking into account their roughness, may be used in the future to model Earth's climate changes.

A Machine Learning Architecture Replacing Heavy Instrumented Laboratory Tests: In Application to the Pullout Capacity of Geosynthetic Reinforced Soils.

For economical and sustainable benefits, conventional retaining walls are being replaced by geosynthetic reinforced soil (GRS). However, for safety and quality assurance purposes, prior tests of pullout capacities of these materials need to be performed. Conventionally, these tests are conducted in a laboratory with heavy instruments. These tests are time-consuming, require hard labor, are prone to error, and are expensive as a special pullout machine is required to perform the tests and acquire the data by using a lot of sensors and data loggers. This paper proposes a data-driven machine learning architecture (MLA) to predict the pullout capacity of GRS in a diverse environment. The results from MLA are compared with actual laboratory pullout capacity tests. Various input variables are considered for training and testing the neural network. These input parameters include the soil physical conditions based on water content and external loading applied. The soil used is a locally available weathered granite soil. The input data included normal stress, soil saturation, displacement, and soil unit weight whereas the output data contains information about the pullout strength. The data used was obtained from an actual pullout capacity test performed in the laboratory. The laboratory test is performed according to American Society for Testing and Materials (ASTM) standard D 6706-01 with little modification. This research shows that by using machine learning, the same pullout resistance of a geosynthetic reinforced soil can be achieved as in laboratory testing, thus saving a lot of time, effort, and money. Feedforward backpropagation neural networks with a different number of neurons, algorithms, and hidden layers have been examined. The comparison of the Bayesian regularization learning algorithm with two hidden layers and 12 neurons each showed the minimum mean square error (MSE) of 3.02 × 10-5 for both training and testing. The maximum coefficient of regression (R) for the testing set is 0.999 and the training set is 0.999 for the prediction interval of 99%.

Spectrophotometric properties of materials from the Mars Science Laboratory at Gale crater: 1. Bradbury Landing to Cooperstown

During the first 443 martian days (sols) of the Mars Science Laboratory (MSL) Curiosity rover mission, visible/near-infrared (445–1012 nm) multispectral observations were acquired at different times of sol by the Mast Camera (Mastcam) and Navigation Camera (Navcam) at five locations along the traverse. Measurements of soil, dust, and rock units spanned sufficient incidence, emission, and phase angles to enable radiative transfer models to constrain the surface scattering functions, single-scattering albedo ( w ), and microphysical properties of the units at each site. Although the model results were mainly consistent with previous results from other landing sites, there were some notable exceptions. For example, the less dusty “Blue rocks” units were modeled as more backscattering compared to ostensibly dustier “Red rocks” units, which was opposite to results from other landed missions. Relations between the peak phase angle of phase curve ratios, w values, and macroscopic roughness ( θ ¯ ) suggested that unlike most of the materials observed by the Spirit and Opportunity rovers, the effects of particle-scale roughness and internal scattering were a greater influence on MSL units than surface scattering. Also noteworthy were unique photometric signatures modeled from data acquired at the landing site on Sol 20 as part of the first in situ spectrophotometric analyses of materials subjected to erosion and/or surface dust removal from spacecraft descent engines. Modeled w spectra were relatively flat and dark for the Sol 20 Blue rocks unit and were positively correlated with average θ ¯ values, similar to some laboratory studies of coarse-grained and/or glassy mafic materials. While low w values and backscattering behaviors were modeled for the Sol 20 “Regolith” unit, the more heavily scoured, lighter-toned regions included soils with extremely forward scattering behaviors, large w values, and that lacked ferric absorption features. The absence of phase reddening effects in all the Sol 20 units likely also was caused by surface disruptions during the landing. Future analyses of additional spectrophotometric data sets from both Curiosity and the Mars 2020 Perseverance rover will continue to yield important comparisons among the variable scattering properties of martian geologic units. • Five sites imaged by MSL Mastcam/Navcam at multiple times-of-sol during Sols 20- 443. • Less dusty rocks modeled as more backscattering compared to redder, dustier rocks. • Small-scale roughness, internal scattering stronger influence than surface scattering. • Unique photometric signatures at landing site due to effects of lander descent plumes.

Kesesuaian Lahan Sawah Pasang Surut dan Faktor Pembatas Utama Tanaman Padi di Kecamatan Sinaboi, Kabupaten Rokan Hilir

The paddy production is decreasing due to land characteristics that are not suitable for its crop requirements. This study aims to identify the inhibiting factors of growth and production and evaluate land suitability based on the factors that inhibit growth and production of tidal paddy fields. The research method used is a soil survey. Soil sampling points were determined based on the overlay results of the current paddy field map and the map of land and soil units. The suitability assessment of paddy fields is carried out using a matching system in actual and potential conditions. The actual land suitability of all SLH is not current suitable (N1) with a very high Fe inhibiting factor. Limiting factors of Fe content can be overcome by making one-way drainage channels, adding organic matter, liming, fertilizing and or using tolerant varieties. The potential land suitability of all SLH is marginally suitable (S3).

Temperature Sensitivity of Topsoil Organic Matter Decomposition Does Not Depend on Vegetation Types in Mountains.

Rising air temperatures caused by global warming affects microbial decomposition rate of soil organic matter (SOM). The temperature sensitivity of SOM decomposition (Q10) may depend on SOM quality determined by vegetation type. In this study, we selected a long transect (3.6 km) across the five ecosystems and short transects (0.1 km) from grazed and ungrazed meadows to forests in the Northwest Caucasus to consider different patterns in Q10 changes at shift of the vegetation belts. It is hypothesized that Q10 will increase along altitudinal gradient in line with recalcitrance of SOM according to kinetics-based theory. The indicators of SOM quality (BR:C, respiration per unit of soil C; MBC:C, ratio of microbial biomass carbon to soil carbon; soil C:N ratio) were used for checking the hypothesis. It was shown that Q10 did not differ across vegetation types within long and short transects, regardless differences in projective cover (14–99%) and vegetation species richness (6–12 units per plot). However, Q10 value differed between the long and short transects by almost two times (on average 2.4 vs. 1.4). Such a difference was explained by environmental characteristics linked with terrain position (slope steepness, microclimate, and land forms). The Q10 changes across studied slopes were driven by BR:C for meadows (R2 = 0.64; negative relationship) and pH value for forests (R2 = 0.80; positive relationship). Thus, proxy of SOM quality explained Q10 variability only across mountain meadows, whereas for forests, soil acidity was the main driver of microbial activity.

Effect of spatial variability on stability and failure mechanisms of 3D slope using random limit equilibrium method

It is well known that soils are prone to spatial non-uniformity, which affects evaluations of slope stability and failure mechanisms. This paper presents a probabilistic slope stability evaluation, considering the 3D spatial variation in the soil properties, by the random limit equilibrium method (RLEM). Specifically, 3D random fields of cohesion c, friction angle ϕ, and soil unit weight γ are generated using a fast Fourier transform. The RLEM is applied to evaluate the effects of the 3D spatial variability of the soil properties on slope stability and failure mechanisms. A Monte Carlo simulation is used to interpret the slope reliability and variation in slope failure dimension. Based on the critical slip surface passing different portions of a slope (slope base, inclined face, and crest), four main failure mechanisms (two base failures and two face failures), and one additional failure mechanism (toe failure), are identified for spatially variable slopes, and the corresponding distributions of the stability number (Ns) and sliding volume (V) are investigated in detail. The results show that the large variation in the soil properties induces changes in the failure mechanisms, and a threshold of c-ϕ values is found for a shift from base failure to toe failure. Lastly, associated sensitivity studies are performed to explore the effects of the uncertainties of the input parameters on the uncertainty of the output. The results estimated by partial Spearman correlation coefficients show that cohesion has the greatest influence on the stability number, and that a positive influence of the unit weight, contributing to slope stability, is found for a base failure mechanism.

Performance Testing Of Sand And Lime As Subgrade Stabilizing Materials For Roads

Soil stabilization is a method used to increase the carrying capacity of a layer of soil, by giving special treatment to that layer of soil. Soil is one of the factors that can affect the structure of road construction. The CBR value is one of the parameters to determine soil carrying capacity, if the CBR value is high then the soil carrying capacity is good, whereas if the CBR value is low then the soil needs to be stabilized. The purpose of this study was to determine the characteristics and classification of soil, determine the results of the grain gradation test, sieve analysis and hydrometer analysis, consistency limits (Atterberg limits) before and after stabilization, compaction results (Proctor) before and after stabilization, determine the CBR value of the soil before and after stabilization. This research included water content test, wet soil unit weight test, specific gravity test, sieving analysis, hydrometer analysis, Atterberg limit test, compaction test (Modification), and immersion CBR test and CBR without immersion. In this test, variations in the addition of 20% sand and lime content were 5%, 10% and 15% of the dry weight of the soil. From the test results, the original soil samples showed soil classification A-7-6 according to AASHTO with maximum dry density (MDD) values of 1.70 gr/cm3 1 day curing, 1.64 gr/cm3 7 days curing and 1.77 gr/cm3 for 14 days curing, there was an increase in the value of the maximum dry density (MDD) in the original soil stabilized with 20% sand and 5% lime, a value of 1.78 gr/cm3 was obtained for 1 day curing, 1.86 gr/cm3 cm3 7 days curing and 1.82 gr/cm3 14 days curing. From the test results, the original soil samples showed soil classification A-7-6 according to AASHTO with CBR values of soaked 3.15% 1 day curing, 3.68% 7 days curing and 4.21% 14 days curing, there was an increase Soaked CBR values on native soil stabilized with 20% sand and 5% lime obtained CBR values of 37.19% at 1 day curing, 42.10% 7 days curing and 30.29% 14 days curing.