Automatic extraction and structuration of soil–environment relationship information from soil survey reports

In addition to soil samples, conventional soil maps, and experienced soil surveyors, text about soils(e.g., soil survey reports) is an important potential data source for extracting soil–environment relationships. Considering that the words describing soil–environment relationships are often mixed with unrelated words, the first step is to extract the needed words and organize them in a structured way. This paper applies natural language processing(NLP) techniques to automatically extract and structure information from soil survey reports regarding soil–environment relationships. The method includes two steps:(1) construction of a knowledge frame and(2) information extraction using either a rule-based method or a statistic-based method for different types of information. For uniformly written text information, the rule-based approach was used to extract information. These types of variables include slope, elevation, accumulated temperature, annual mean temperature, annual precipitation, and frost-free period. For information contained in text written in diverse styles, the statistic-based method was adopted. These types of variables include landform and parent material. The soil species of China soil survey reports were selected as the experimental dataset. Precision(P), recall(R), and F1-measure(F1) were used to evaluate the performances of the method. For the rule-based method, the P values were 1, the R values were above 92%, and the F1 values were above 96% for all the involved variables. For the method based on the conditional random fields(CRFs), the P, R and F1 values for the parent material were, respectively, 84.15, 83.13, and 83.64%; the values for landform were 88.33, 76.81, and 82.17%, respectively. To explore the impact of text types on the performance of the CRFs-based method, CRFs models were trained and validated separately by the descriptive texts of soil types and typical profiles. For parent material, the maximum F1 value for the descriptive text of soil types was 90.7%, while the maximum F1 value for the descriptive text of soil profiles was only 75%. For landform, the maximum F1 value for the descriptive text of soil types was 85.33%, which was similar to that of the descriptive text of soil profiles(i.e., 85.71%). These results suggest that NLP techniques are effective for the extraction and structuration of soil–environment relationship information from a text data source.

Updating conventional soil maps by mining soil–environment relationships from individual soil polygons

Conventional soil maps contain valuable knowledge on soil–environment relationships.Such knowledge can be extracted for use when updating conventional soil maps with improved environmental data.Existing methods take all polygons of the same map unit on a map as a whole to extract the soil–environment relationship.Such approach ignores the difference in the environmental conditions represented by individual soil polygons of the same map unit.This paper proposes a method of mining soil–environment relationships from individual soil polygons to update conventional soil maps.The proposed method consists of three major steps.Firstly,the soil–environment relationships represented by each individual polygon on a conventional soil map are extracted in the form of frequency distribution curves for the involved environmental covariates.Secondly,for each environmental covariate,these frequency distribution curves from individual polygons of the same soil map unit are synthesized to form the overall soil–environment relationship for that soil map unit across the mapped area.And lastly,the extracted soil–environment relationships are applied to updating the conventional soil map with new,improved environmental data by adopting a soil land inference model(SoLIM)framework.This study applied the proposed method to updating a conventional soil map of the Raffelson watershed in La Crosse County,Wisconsin,United States.The result from the proposed method was compared with that from the previous method of taking all polygons within the same soil map unit on a map as a whole.Evaluation results with independent soil samples showed that the proposed method exhibited better performance and produced higher accuracy.

Stress-strain relationship of unsaturated cohesive soil

A moisture-content based constitutive model was proposed based on the hyperbolic model as an attempt to move towards the implementation of unsaturated soil mechanics into routine geotechnical engineering practice. The stress-strain behavior of in-situ soil at a depth of 5 m was investigated by conducting undrained triaxial compression tests using the remolded soil samples. The test results show that the stress-strain relationship of unsaturated cohesive soil is still hyperbolic. The values of parameters a and b given in the model decrease with increasing the confining pressure for soil samples with the same moisture content and increase with increasing the moisture content for soil samples under the same confining pressure. The relationships between parameters a, b and moisture content were studied for confining pressures of 100, 150, 200 and 250 kPa. The comparison between the measured and predicted stress-strain curves for an additional group of soil samples, having a moisture content of 25.4%, shows that the proposed moisture content-dependent hyperbolic model provides a good prediction of stress-strain behavior of unsaturated cohesive soil.

A Flexible Model for Moisture-Suction Relationship for Unsaturated Soils and Its Application

The mathematical equation for the moisture-suction relationship also known as soil water characteristic curve (SWCC) is one of the constitutive relations necessary for the computational modeling of deformation and flow problems of unsaturated soil using the finite element method. In this paper, a new empirical equa-tion for the SWCC is developed that incorporates the actual airentry suction and the maximum possible suction of the soil as input parameters. The capability of the new model is investigated by fitting the experimental data for twelve different soils that includes sands, silts, and clays. The model fits the experimental data well including in high suction range which is one of the difficulties observed in other commonly used models such as the Brooks and Corey, van Genuchten, and Fredlund and Xing models. The numerical stability and the performance of the new model at low and high degrees of saturations in finite element simulation are investigated by simulating the dynamic response of a compacted embankment and the results are compared with similar predictions made using widely used SWCC models.

Multi-scale spatial relationships between soil total nitrogen and influencing factors in a basin landscape based on multivariate empirical mode decomposition

The relationships between soil total nitrogen(STN)and influencing factors are scale-dependent.The objective of this study was to identify the multi-scale spatial relationships of STN with selected environmental factors(elevation,slope and topographic wetness index),intrinsic soil factors(soil bulk density,sand content,silt content,and clay content)and combined environmental factors(including the first two principal components(PC1 and PC2)of the Vis-NIR soil spectra)along three sampling transects located at the upstream,midstream and downstream of Taiyuan Basin on the Chinese Loess Plateau.We separated the multivariate data series of STN and influencing factors at each transect into six intrinsic mode functions(IMFs)and one residue by multivariate empirical mode decomposition(MEMD).Meanwhile,we obtained the predicted equations of STN based on MEMD by stepwise multiple linear regression(SMLR).The results indicated that the dominant scales of explained variance in STN were at scale 995 m for transect 1,at scales 956 and 8852 m for transect 2,and at scales 972,5716 and 12,317 m for transect 3.Multi-scale correlation coefficients between STN and influencing factors were less significant in transect 3 than in transects 1 and 2.The goodness of fit root mean square error(RMSE),normalized root mean square error(NRMSE),and coefficient of determination(R2)indicated that the prediction of STN at the sampling scale by summing all of the predicted IMFs and residue was more accurate than that by SMLR directly.Therefore,the multi-scale method of MEMD has a good potential in characterizing the multi-scale spatial relationships between STN and influencing factors at the basin landscape scale.

Relationships between Cadmium in Tissues of Cacao Trees and Soils in Plantations of Trinidad and Tobago

The primary source of cadmium in cocoa beans has been linked to its direct uptake by the cacao plant from cadmium contaminated soils. This research was conducted to evaluate and interpret significant relationships between cadmium levels in tissues of the cacao plant and soils from cocoa-growing areas in Trinidad and Tobago. Total (HNO3-extractable) concentrations of cadmium in both tissues and soils were determined. The levels of cadmium measured varied in the order: leaves > pods > shells > nibs > soil. Cadmium levels in all the cacao tissues analyzed were significantly (p < 0.05), positively and strongly correlated with each other. Additionally, significant (p < 0.05) positive relationships were also identified between Cd in cacao tissues and corresponding total HNO3-extractable Cd levels in soils. These findings suggest that they can possibly be used as predictive tools for assessing Cd levels in cacao.

Research on the Optimal Vegetation Cover for Remote Sensing Assessment of Soil Erosion Risk Using the Temporal Matching Relationship between Rainfall and Vegetation

Vegetation cover derived from remote sensing image is widely used for soil erosion risk assessment, but there is no clear guideline to select the most appropriate temporal satellite data. It is common practice that satellite data during growing season are randomly selected and used in soil erosion risk assessment. However, the effectiveness of vegetation in protecting the soil is quite different even if it is the same growing season since vegetation covers change as they grow. This article aims to provide a method of choosing optimal vegetation cover for studying soil erosion risk using remote sensing, that is, the vegetation cover in the most appropriate temporal period. Based on the temporal relationship of the two most active impact factors, rainfall and vegetation, an index of RV is developed and used to indicate the relative erosion risk during the year. The results show that annual variation of rainfall is significant, and vegetation is relatively stable, resulting in their matching relationship is different in each year. The correlation coefficient reaches 0.89 between RV and real sediment transport during the period when rainfall can cause soil erosion. In other words, RV is a good indicator of soil erosion. Therefore, there is a good correlation between RV maximum and the optimal vegetation cover, which can help facilitate erosion research in the future, showing good potential for successful application in other places.

Different mechanisms underlie similar species-area relationships in two tropical archipelagoes

Despite much research in the field of island biogeography,mechanisms regulating insular diversity remain elusive.Here,we aim to explore mechanisms underlying plant species-area relationships in two tropical archipelagoes in the South China Sea.We found positive plant species-area relationships for both coral and continental archipelagoes.However,our results showed that different mechanisms contributed to similar plant species-area relationships between the two archipelagoes.For coral islands,soil nutrients and spatial distance among communities played major roles in shaping plant community structure and species diversity.By contrast,the direct effect of island area,and to a lesser extent,soil nutrients determined plant species richness on continental islands.Intriguingly,increasing soil nutrients availability(N,P,K)had opposite effects on plant diversity between the two archipelagoes.In summary,the habitat quality effect and dispersal limitation are important for regulating plant diversity on coral islands,whereas the passive sampling effect,and to a lesser extent,the habitat quality effect are important for regulating plant diversity on continental islands.More generally,our findings indicate that island plant species-area relationships are outcomes of the interplay of both niche and neutral processes,but the driving mechanisms behind these relationships depends on the type of islands.

Review of collapse triggering mechanism of collapsible soils due towetting

Loess soil deposits are widely distributed in arid and semi-arid regions and constitute about 10% of land area of the world.These soils typically have a loose honeycomb-type meta-stable structure that is susceptible to a large reduction in total volume or collapse upon wetting.Collapse characteristics contribute to various problems to infrastructures that are constructed on loess soils.For this reason,collapse triggering mechanism for loess soils has been of significant interest for researchers and practitioners all over the world.This paper aims at providing a state-of-the-art review on collapse mechanism with special reference to loess soil deposits.The collapse mechanism studies are summarized under three different categories,i.e.traditional approaches,microstructure approach,and soil mechanics-based approaches.The traditional and microstructure approaches for interpreting the collapse behavior are comprehensively summarized and critically reviewed based on the experimental results from the literature.The soil mechanics-based approaches proposed based on the experimental results of both compacted soils and natural loess soils are reviewed highlighting their strengths and limitations for estimating the collapse behavior.Simpler soil mechanics-based approaches with less parameters or parameters that are easy-to-determine from conventional tests are suggested for future research to better understand the collapse behavior of natural loess soils.Such studies would be more valuable for use in conventional geotechnical engineering practice applications.

Growth and mineral nutrient analysis of teak (Tectona grandis) grown on acidic soils in south China

Teak （Tectona grandis L.f.） is widely planted in the world due to its high market demand, economic, ecological and social value. Its plantations have mostly been established and expanded into sites that are acidic to severely acidic in southern China. But, there are no available and specific evidence-based nutrient management techniques. To better recognize and understand the relationship between teak tree growth and nutrient content in the foliage and soil and establish nutrient norms are critical to optimally manage these young plantations. We studied the foliar nutrient and soil chemistry in 19 representative teak plantations aged 5-8 years. Regression analysis indicated that the mean annual increment of teak volume was linearly and positively correlated with foliar N, Ca, Fe and B concentrations, with soil base saturation percentage, available P and Zn concentrations, and negatively correlated with soil Al concentration. Only if the Ca and Mg contents in soil were enhanced, could the increase in soil base saturation percentage benefit teak growth. A revised classification of low-and high-yielding stands was established by using a sorting method of principal components over 6 foliar macro and 8 micro elements in a Diagnosis and Recommendation Integrated System （DRIS）. Specific DRIS norms for teak plantations in acid soils were derived. The nutrient balance of N, P, K Ca, Mg, Zn, B with Fe or A1, Ca with Mg, and Fe with AI provided a key to promote the growth of teak in acid soils. Meanwhile, soil Zn was also found as a primary trace element that affected teak growth in this study.

Soil water resources use limit in the loess plateau of China

Soil water is a key factor limiting plant growth in water-limited regions. Without limit of soil water used by plants, soil degradation in the form of soil desiccation is easy to take place in the perennial forestland and grassland with too higher density or productivity. Soil water resources use limit (SWRUL) is the lowest control limit of soil water resources which is used by plants in those regions. It can be defined as soil water storage within the maximum infiltration depth in which all of soil layers belong to dried soil layers. In this paper, after detailed discussion of characteristics of water resources and the relationship between soil water and plant growth in the Loess Plateau, the definition, quantitative method, and practical applications of SWRUL are introduced. Henceforth, we should strengthen the study of SWRUL and have a better understanding of soil water resources. All those are of great importance for designing effective restoration project and sustainable management of soil water resources in water- limited regions in the future.

Analysis of Coupling between Soil and Water Conservation and Economic-social Development

The coupling relation exists in water and soil conser-vation and economic-social development. The article analyses the relation of soil and water conservation and economic-social development stages as well as the coupling analytical method. Then calculates the expecting income by dispersing Markov decision and calculates the correlation coefficient and the re-lationship degree. The article obtains the relationship of soil and water conservation investments and all kinds of incomes. Finally, it analyzes the important meaning in socio-economic development of water and soil conservation.

Experimental investigation on static and dynamic resilient moduli of compacted fine soil

To investigate the static and dynamic resilient modulus of fine soil,and adapting to the new design code and maintenance system of highway subgrade in China,a series of static and dynamic tests were carried out according to the standard laboratory test methods(JTG E40-2007 and JTG D30-2015,respectively).The effects of initial water content,compactness and freeze-thaw cycles on the static and dynamic resilient moduli of fine soil were investigated and analyzed.Experimental test results show that with increasing water content,dry density and freeze-thaw cycles,the static moduli reduces about10.2%~40.0%,14.4%~45.5%,and 24.0%~50.3%,and dynamic moduli reduces about 10.9%~90.8%,2.5%~38.4%,and0.0%~46.0%,respectively.Then,the empirical mathematical relationship between static and dynamic resilient moduli was established under different water content,dry density and freeze-thaw cycles.The investigation results can be used to determine the dynamic modulus of fine soil by widely used static modulus,which could meet the requirement of adopting dynamic modulus index in new specification.

Factor Analysis of the Parameters of Samples of the Steppe Soil and Grass Of Mongolia and Inland Mongolia of China on the Eastern Transsect of the Eurasian Steppe

Regularities of rank distributions and binary relations between nine parameters are given.The most active are the geographical coordinates of 48 test sites.This proves that the geomorphology of the steppes in Mongolia and Inner Mongolia is becoming decisive.Factor analysis showed that the first four places for influencing variables and dependent indicators are the same:in the first place is the northern latitude,the second is the east longitude,the third is the average annual precipitation,and the fourth is the intensity of sheep grazing.The rest of the factors are located in different ways.The density of organic carbon was only in ninth place as an influencing variable,and in seventh place as a dependent indicator.This is based on the fact that organic carbon is an accumulative(cumulative)parameter over many years.The productivity of the biomass of steppe grass as an influencing variable is in sixth place,and as a dependent indicator(criterion)only in ninth place.This parameter is seasonal,therefore,in comparison with organic carbon,it is highly dynamic.The average annual temperature as an influencing variable is in fifth place,but as a dependent indicator only in eighth place.This was influenced by the strong averaging of the parameter(average value for the year).Plants are strongly influenced by the temperature dynamics during the growing season,and even more by the sum of temperatures during the growing season.With the productivity of steppe grass less than 75 g/m^(2),the intensity of sheep grazing is zero.According to the second term of the trend,an optimum of 270 g/m^(2) appears with the maximum intensity of sheep grazing on average 65 pcs/km^(2).The first fluctuation shows that with an increase in grass biomass,there is a loss of stability of the grass cover with an exponential growth of the amplitude.The second oscillation is dangerous in that with an increase in the biomass of the grass,the half-period of the oscillation sharply decreases and this will also lead to the collapse of the steppe grass.From the remnants of the effect of sheep grazing on grass biomass,it can be seen that there are three clusters:(1)from 0 to 30;(2)from 30 to 95;(3)more than 95 pcs/km^(2).In this case,the variability of the productivity of the grass decreases.

Decomposition Temperature of Cold Seep Carbonate and its Relationship with Delta Carbonate

Delta carbonate （Delta C, AC） method is a commonly- used surface geochemical exploration method for petroleum surveys. Delta C holds that light hydrocarbon gases leak into near-surface soils or sediments from underlying petroleum accumulations, then partly oxidized to CO2, resulting in a special carbonate precipitation, which is termed as Delta carbonate （△C）.

Experimental study on dispersive soil in western Jilin

In order to research engineering geological properties of the soil in Zhenlai of western Jilin, especially the dispersivity of soil, the authors carried out the basic physicocbemical test and dispersivity identification test. The results show that the dispersivity of the soil increases with the increase of depth within 0-30 cm （surface soil） ; it decreases as the depth increases within in 30-100 cm. Furthermore, the statistical analysis of the dispersivity indexes and physicochemical propertity indexes show that the DP is positively linear correlated with total soluble salt content, sodium ion content, ESP, pH and organic matter content. Meanwhile, it is negatively linear correlated with clay content, and the linear relationship is better. Through the study of the dispersion mechanism of soil samples, it can be concluded that sodium montmorillonite, higher percentage of exchangeable sodium and high pH are the main reasons for the dispersion of soils in western Jilin.

Physico-Chemical Soil Properties and Their Correlations with Maize and Cassava Production in Ebonyi, Nigeria

This study analyzed relationships between soil properties and food crop production in Ebonyi State of southeast Nigeria. Free survey was conducted after three zones (Agbaja, Akaeze and Ikwo) in the state were purposely selected for representation of the soil sampling. Two types of sampling were conducted;Auger sampling at 0 - 20 and 20 - 40 cm depths and soil profile sampling. Annual crop yield data on maize and cassava for the state from 1988 to 2017 were collected from Agriculture Development Program. Variations in properties among soil horizons were obtained using coefficient of variations while soil parameters were regressed against crop yields to establish their relationships. Results showed that fine sand, total sand, bulk density, total porosity, soil pH, and available phosphorus significantly (p = 0.05) differ from 0 - 20 cm and 20 - 40 cm depths. Also, cassava yield correlated negatively with base saturation, and organic matter at 0.05 probability level;with exchangeable Ca and Na at 0.01 probabilities level but correlated positively with bulk density and available water capacity at 0.01 and 0.05 probability levels, respectively. Similarly, maize yield correlated negatively with available phosphorus and total nitrogen at 0.05 probability level;and with total porosity and exchangeable Ca at 0.01 probability level;and then correlated positively with available water capacity, and bulk density, at 0.01 probability level;with coarse sand at 0.05 probability level. However, soils of Ebonyi State are fertile but some of the chemical properties are still low, therefore, it is paramount to improve the quality of the soil to achieve improved food security in the state.

Influence of topography,soil properties and plant community on the biomass of Abies georgei var.smithii seedlings in Southeast Tibet

Biomass of seedlings at different developing stages of growth is important information for studying the response of species to site conditions.The objectives of this study was to explore the distribution characteristics of AGB(above-ground biomass)and BGB(below-ground biomass)of Abies georgei var.smithii seedlings of different ages,and investigate the effects of topography(slope aspect,altitude),plant community characteristics(crown density,species diversity,etc.),and soil properties(soil physical and chemical properties)on the biomass and its allocation.Seedlings in five age classes(1–2,3–4,5–6,7–8,and 9–10 years old)were collected by full excavation from 6 elevations(3800 m,3900 m,4000 m,4100 m,4200 m,4300 m)on the north and south slopes of Sejila Mountain in Tibet.15seedlings of each age class were investigated at one altitude.The individual effects of seedling age(SA)and the interaction effects of SA,slope aspect(SL),and elevation(EG),namely,SL×EG,SL×SA,EG×SA,and SL×EG×SA,had significant effects on the AGB of the seedlings(p<0.05),whereas BGB was only significantly affected by SA(p<0.001).The AGB and BGB of the seedlings showed a binomial growth trend with the increase in seedling age,and had an allometric relationship at different elevations,α(allometric exponential)varied from 0.913 to 1.046 in the northern slope,and from 1.004 to 1.268 in the southern slope.The biomass of seedlings on the northern slope was remarkably affected by stand factors,with a contribution rate of 47.8%,whereas that on the southern slope was considerably affected by soil factors with a contribution rate of 53.2%.The results showed that age was the most important factor affecting seedling biomass.The allometric pattern of seedling biomass was relatively stable,but in a highaltitude habitat,A.georgei var.smithii seedlings increased the input of BGB.Understanding seedling biomass allocation and its influencing factors is useful for evaluating plants’ability to acquire resources and survival strategies for adaptation to the environment in Tibet Plateau.

水土保持生态建设下的黄土高原典型流域水沙响应

为探讨黄土高原多沙粗沙区流域水沙关系演变特征及其对水土流失治理的响应,以黄河中游无定河流域为研究对象,综合采用水沙关系曲线、数理统计等多种方法,系统分析1956—2019年间无定河流域水沙关系多时间尺度演变特征及其与水土流失治理的协同响应。研究结果表明:1)研究时段内,无定河流域年径流及年输沙量呈锐减趋势(P<0.05),且均在1970年左右发生减少突变;2)流域水沙关系在年际和场次洪水尺度上均发生深刻变化。2010年以后,暴雨频发导致流域内侵蚀物源头供应明显增加,流域河道泥沙输送能力小幅提高;3)水土保持措施实施对流域水沙锐减影响较大。2000年前后在相似降雨条件下,单位降雨量径流量和单位降雨量输沙量较20世纪70年代减少47%和62%。水土保持措施面积增加与流域径流输沙减少呈现较好的一致性,流域水土流失治理在提高黄河多沙粗沙区流域下垫面抗侵蚀能力等方面发挥重要作用。研究结果可为科学认知区域水土流失治理成效及入黄泥沙锐减成因提供参考。

An Influence of Multiple Drying/Rewetting Cycles upon the Respiration of Organic Forest Soil

It is already known that repeating cycles of drying and rewetting decrease the metabolic activity of the soil. The aim of this paper is to explain on the basis of a laboratory experiment how the respiratory processes of organic soil collected from the forest ecosystem typical for a moderate climate are changing during ten consecutive events of watering, and how alters the relationship between changing humidity of the soil and oxygen consumption/carbon dioxide emission. After 10 cycles, the respiration decreases by 2.4 times however amounts of excreted carbon dioxide and consumed oxygen do not differ between cycles 9 and 10. In successive DRW cycles also the relationship between oxygen consumption/carbon dioxide excretion and humidity level changes. This relationship is logarithmic and the analysis of subsequent regressions indicates the direction of those changes. In successive cycles the value of β coefficient (slope) decreases, and both the values of β and coefficient R2 are always higher for oxygen consumption that for carbon dioxide excretion. This indicates that processes involving oxygen consumption are always more sensitive to fluctuations of humidity than processes producing carbon dioxide. The optimum of respiration declines in successive DRW cycles.