Humus Characteristics Research Articles

Characterization of humic acids from soil of Delhi regions and their impact on plant growth

Humus materials are considered complex organic substances generated through a chain of chemical reactions and responsible for many processes in soil that ultimately govern soil health. The structural and functional characteristics of humus depend upon the location, quality, and microbial abundance of the soils. However, the differential characteristics of soil organic matter, seasonal changes, parent rock, plant cover, microbial abundance, and anthropogenic activities majorly affect it. The present study has aimed toward the extraction of humus from five different locations in the Delhi region of India and their characteristics were investigated through elemental analysis, Fourier Transform infrared (FT-IR) spectroscopy, and UV spectroscopy. The results showed that there was a higher degree of unsaturation detected in the Forest soil sample. The results of FT-IR showed the presence of characteristic peaks of humus in the samples however the intensity of bands was weak in sample disposable site soil sample and clayey soil sample due to the variation in soil physicochemical properties. The study also aimed to assess the growth of Oryza sativa (rice) plants observed in the hydroponics system. The significant finding was observed with the forest soil sample in 1000 mgL-1 and treatment in which the growth was minimum in clayey soil of 1500 mgL-1. Our investigation infers the diverse nature of humus in different soils and its implications for plant growth, highlighting the importance of understanding soil organic matter for sustainable agriculture and soil health management

Effects of different types of vegetation cover on soil microorganisms and humus characteristics of soda-saline land in the Songnen Plain.

In the soda-saline grasslands of the Songnen Plain, Jilin Province, China, the prohibition of grazing has led to significant changes in plant communities and soil properties. However, the intricate interplay between soil physical and chemical attributes, the soil microbial community, and their combined influence on soil humus composition remains poorly understood. Our study aimed to evaluate the impact of natural vegetation restoration on soil properties, microbial community diversity, and composition in the soda-saline soil region of the Songnen Plain. We conducted assessments of soil physical and chemical properties, analyzed community diversity, and composition at a soil depth range of 0-20 cm. The study covered soils with dominant soda-saline vegetation species, including Suaeda glauca Bunge, Puccinellia chinampoensis Ohwi, Chloris virgata Swarta, Phragmites australis (Clay.), Leymus chinensis (Trin.), and Tzvelev. We compared these vegetated soils to bare land devoid of any plants. We found that soil organic content (SOC) in vegetation restoration areas was higher than in bare land, with SOC content varying between 3.64 and 11.15 g/kg in different vegetated areas. Notably, soil pH emerged as a pivotal factor, explaining 11.4% and 12.2% of the variance in soil bacteria and fungi, respectively. There were correlations between SOC content and the relative abundance of specific microbial groups, with Acidobacteria and Mortierella showing a positive correlation, while Actinobacteria, Gemmatimonadetes, and Ascomycota exhibited significant negative correlations with SOC. The disparities in SOC composition and content among the soda-saline vegetation types were primarily attributed to variations in pH. Consequently, reducing soil pH is identified as a critical step in the process of vegetation restoration in soda-saline land. Prohibiting grazing has the potential to increase soda-saline SOC content and enhance microbial diversity, with Leymus chinensis and Phragmites australis showing particularly promising results in terms of higher SOC carbon content and microbial diversity.

Effect of humus on photodegradation of quinclorac under different fertilization modes.

Humus is a specific kind of organic matter widely distributed in soils. The characteristics of humus have significant impacts on the fate of pollutants in the environment. In this study, we examined the effects of fertilization modes from rice rotation systems on the contents, spectral properties, photochemical activity, and photosensitization of quinclorac (QNC) of humic (HA) and fulvic acids (FA). The results showed that under the rice-vegetable rotation system, organic fertilizer treatment decreased the humification degree and molecular weight of HA, but increased the number of oxygen-containing functional groups and the abilities of photoproducing hydroxyl radical (HO·), singlet oxygen (1O2) and photosensitizing QNC, compared with chemical fertilizer treatment. Under organic fertilization mode, the molecular weight of FA was increased, but the number of redox functional groups and the abilities of photoinducing HO· and 1O2 and photosensitizing QNC were decreased. Under rice-shrimp cultivation system, organic-inorganic fertilizer treatment increased the humification degree, molecular weight, number of redox functional groups and oxygen-containing functional groups, and 1O2 photogeneration of HA, but decreased the abilities of photoproducing HO· and photosensitizing QNC, as compared with chemical fertilizer treatment. The humification degree and molecular weight of FA under organic-inorganic fertilization mode were increased, while the abilities of photoproducing HO· and 1O2 and photosensitizing QNC were decreased. In conclusion, organic fertilization could enhance the photochemical activity and photosensitizing efficiency of humus, and further promote the photodegradation of QNC in the environment.

Tracing the variation of dissolved organic matter in the two-stage anoxic/aerobic process treating swine wastewater using fluorescence excitation-emission matrix with parallel factor analysis

Swine wastewater has become one of the main agricultural pollution sources. Quantitative characterization of dissolved organic matter (DOM) is often used in various water bodies, but there are few studies on DOM analysis of swine wastewater. In this study, swine wastewater was treated by a step-feed two-stage anoxic/aerobic (SF-A/O/A/O) process. By using parallel factor (PARAFAC) analysis of fluorescence excitation-emission matrix (EEM), the main components of swine wastewater were aromatic protein-like substances (C1), tryptophan-like substances (C2), fulvic acid-like/humic-like substances (C3) and humic-like substances (C4). Protein-like substances were degraded significantly, while humic-like substances were difficult to be utilized by microorganisms. Fluorescence spectral indexes showed that the characteristics of endogenous input and humus were enhanced. Moreover, several significant correlations between DOM components, fluorescence spectral indexes and water quality indexes were observed. These findings help to understand the biochemical role and the impact of DOM in water quality monitoring and control of swine wastewater.

Comparison of Dissolved Organic Matter Composition and Microbial Distribution between Distributed-Inflow Biological Reactor and Two-Stage Anoxic/Aerobic for Piggery Wastewater Treatment

Piggery wastewater contains high amounts of feces, carbon, nitrogen, phosphorus, and other contaminants, introducing serious pollution into water, soil, and the atmosphere. Biological treatment technology is widely used in large-scale pig farms because of its high efficiency and economical advantages. In this study, two typical biological treatment systems—a distributed-inflow biological reactor (DBR) and a two-stage anoxic/aerobic (A/O/A/O)—were adopted to treat piggery wastewater to compare the treatment performance, the dissolved organic matter (DOM) composition, and the microbial distribution characteristics. The results show that the A/O/A/O system had better removal performance in terms of chemical oxygen demand (COD) compared to the DBR system, and similarly effective at removing and ammonia nitrogen (NH4+-N) and total nitrogen (TN). Using parallel factor analysis of the fluorescence excitation–emission matrix, four DOM components—namely fulvic acid-like/humic-like substances (C1), tyrosine-like substances (C2), humic-like substances (C3), and tryptophan-like substances (C4)—were tracked in piggery wastewater. Protein-like substances were significantly degraded, while humic-like substances were difficult for microorganisms to utilize. The endogenous input and humus characteristics of effluents were enhanced. Bacteroidetes (43.9% and 37.5% ) and Proteobacteria (43.1% and 56.7%) are the dominant bacteria in DBR and A/O/A/O systems. The microbial metabolites in DBR and A/O/A/O systems are mainly composed of amino acids, sugars, alcohols, and other small molecules, while those in the municipal sewage treatment plant system is mainly composed of ketones, amines, acids, lipids, and other small molecules. The results of microbial communities and metabolites can help to trace the process of biological systems treating piggery wastewater.

Effect of aeration on water quality and sediment humus in rural black-odorous water

Black-odorous water, which exists widely in rural areas of China, affects the living environments of residents and causes a loss of ecosystem functions, and improper treatment may even cause secondary pollution. Moreover, the transformation relationships among the components of humus in the sediments of black-odorous water are largely unknown. Therefore, it is necessary to select appropriate methods for treating black-odorous water in rural areas and to understand the characteristics of humus in sediment during the treatment process. In this study, the use of aeration in treating black-odorous water and interstitial water in rural areas was studied and the effects of different treatment methods on the contents and spectral characteristics of humus components in sediments were explored. It was found that the quality of the treated water improved from severe black-odorous to nonblack-odorous, the colour of the sediment changed from black to greyish-brown to turquoise, and the odour changed from strong to weak. The removal rates of ammonia nitrogen, total nitrogen, total phosphorus, and chemical oxygen demand in the sediment aeration group reached more than 50% in the upper water, and more than 70% in the interstitial water. After treatment, the content of fulvic acid, the main black substance in sediment, decreased by 0.36–1.58 g/kg, and the molecular structure of the humus was simplified.

Humus status of chernozem soils formed under deep hydrogen release and different humidification conditions

Purpose of the study: to reveal changes in some humus characteristics in chernozems under the influence of of two factors, specifically, humidification and the flow of endogenous hydrogen. Place and time of the study. Soil sampling and hydromenty were carried out on the territory of the Gryazinsky district of the Lipetsk region (Krivoborgsko-Saltykovsky trough, the territory with leached chernozems) and on the territory of the Oktyabrsky district of the Voronezh region (Khopersky deep fault, the territory with ordinary chernozems) in June 2017. Methods. The molecular hydrogen content was measured directly in the field with a portable hydrogen gas analyzer VG-3B. The total soil organic carbon (SOM) content was determined by the Tyurin method, and pH was measured potentiometrically. To assess the SOM composition, an alkaline pyrophosphate extraction was used. The luminance values of soil samples were determined using the CIELAB international chromaticity system and the LRV system on the Nix Color Sensor spectrocolorimeter. Results. The study showed that under the influence of hydrogen flow in different humidification regions, the effect of these two factors was different. Tthe establishment of the reductive regime, signs of podzolization and gleing in the morphological profile, acidification of the soil bulk and brightening of the upper humus horizon were found to be common features between the soils of these regions. However, the effect of such active reducing agent as hydrogen on the SOM and qualitative composition in these regions varied greatly. In the drier region with ordinary chernozems, SOM accumulated in hydrogen relief depressions (from 2.4 to 5.4%), and due to their sharp predominance (three times, sometimes four times) in SOM composition and predominance in the soil profiles, fulvic acids determined a sharp increase in soil acidity. The leached chernozems, on the contrary, manifested a significant SOM loss (from 3.9 to 2.2%), with humic acids predominating in SOM composition. This effect was most likely associated with the removal of more mobile SOM components outside the soil profile in the more humic climate of the Lipetsk region.

Human-Altered Soils at an Archeological Site of the Bronze Age: The Tyater-Araslanovo-II Settlement, Southern Cis-Ural Region, Russia

This paper presents the results of studying the soils at the archeological site of the Tyater-Araslanovo-II settlement located in the Republic of Bashkortostan, eastern European Russia. The settlement functioned in the 15th–12th centuries BCE (the Late Bronze Age). We compared the soil properties at four sites in the study area: archeological (1), buried (2), affected by long pyrogenic exposure (3), and background site (4). In soil samples, the total carbon content, the fractional composition of humus and organic matter characteristics, alkaline hydrolyzable nitrogen, total phosphorus, mobile phosphorus, potassium, absorbed calcium and magnesium, pH, particle size distribution, basal soil respiration, and optical density were estimated. The study results showed the anthropogenic impact on the archeological site’s soils. The newly formed AU horizon at the archeological site (1), affected by the cattle summer camp, was richer in soil nutrients and agrochemical properties, namely, the content of exchangeable and gross forms of phosphorus, alkaline hydrolyzable nitrogen, and exchange cations of the soil absorbing complex compared to the reference soil (4). For the pyrogenic layer (AU[hh]pyr) from the ancient furnace (fireplace) (3), the mobile and total forms of phosphorus were several times higher than those in the reference soil (4) but inferior regarding other agrochemical parameters. Thus, the activities of ancient people (especially cattle breeding) greatly influenced the properties of the soil.

CALCIUM IN SOIL HUMUS OF WEST-SIBERIAN TRANSECT

The paper analyzes the behavior of one of the main components of humus (humic acids - calcium system) depending on the participation of calcium in the biological cycle of substances. The role of calcium in the formation of ecological stability of humic systems is shown, which largely determines the environmentally sustainable agriculture. It is shown that the changeable calcium amounts to no more than a half of its total content in humus horizon of automorphic zonal soils. Within the limits of the transect, the participation of calcium in binding of humic and fulvic acids is distributed according to their content in humus composition. Additional assessment of exchangeable calcium content to be determined by nontraditional method showed the same geographic regularity of its distribution in the soils of the transect as in the case of distribution of the main characteristics of humus.

Effects of exogenous selenium levels on humus characteristics in selenium-enriched soil and lead accumulation in Brassica juncea

Many selenium (Se)-enriched soils suffer from severe lead (Pb) contamination. Many studies indicated that soil humus can effectively absorb heavy metal ions, and Se can alleviate Pb accumulation in plants. However, few studies explored the effects of exogenous Se levels on humus composition in Se-enriched soil and Pb enrichment in Brassica juncea (B. juncea). We conducted a pot experiment. First, the Se-enriched soil sample was mixed with 200 mg·kg−1 level of Pb and maintained in a stable equilibrium for 2 months. Second, the soil was treated in different ways. Six treatments were performed as follows: one control treatment (CK) was included, and five different doses of Na2SeO3 (S1, S2, S3, S4, and S5) were applied to the pots. Each treatment was prepared in triplicate. Then, the B. juncea seeds were sown in each pot. Finally, on the 40th day, B. juncea plants in each pot were harvested and soil was sampled for subsequent experimental analysis. The different levels of selenite decreased the Pb content in roots, stems, and leaves of B. juncea by 5.43–48.70%, 5.13–39.86%, and 6.62–31.91%, respectively, and significantly increased the Se contents by 7.22–24.21, 5.91–34.11, and 12.49–57.06 folds compared with control treatment, respectively. The total Pb in the soil was reduced by 1.06–13.68% and soil pH was increased by approximately 0.06–0.21 units in all treatments. Exogenous Se also reduced diethylenetriaminepentaacetic acid (DTPA)-extracted Pb and exchangeable and iron-manganese oxide-bound Pb but increased the content of carbonate-bound and residual Pb. The composition of humus followed this order as follows: humic acids (HA) < fulvic acids (FA) << humin (HM); the adsorption isotherms of HA and FA for Pb2+ were well described by the Langmuir adsorption model, and the adsorption process were positively correlated with the Pb2+ concentration (P < 0.05). The Se levels, contents of humus components, and Pb concentration in soil were negatively correlated with each other. The addition of low Se levels can effectively antagonize Pb in Se-enriched soil and contribute to the adsorption of Pb by soil humus components, inhibiting the migration of Pb in soil-B. juncea systems to reduce the Pb accumulation in B. juncea.

Spatiotemporal variations of spectral characteristics of dissolved organic matter in river flowing into a key drinking water source in China

The characteristics of dissolved organic matter (DOM) in inflowing river, flowing into drinking water, have profound influences on the quality and safety of water. Here, ultraviolet–visible (UV–vis) spectroscopy and three-dimensional fluorescence (EEM) spectroscopy were combined to investigate the spatiotemporal variations of DOM in Nanfei River flowing into Chaohu Lake in China. 24 water samples and 24 surface sediments samples (including dry-to-wet transition season and wet season in 2018) were collected from different types of outlets. Parallel factor analysis (PARAFAC) model and correlation analysis were conducted to identify the primary sources of DOM. Two humic-like components (C1 235–250 nm/385–430 nm and C3 255–270 nm/455–510 nm) and one tryptophan-like component (C2 270–290 nm/320–350 nm) were effectively identified by PARAFAC model. The results showed DOM concentration presented significant spatiotemporal variations. The concentration was much lower in water than in surface sediments in dry-to-wet transition season, but higher in the wet season. Fluorescence index (FI), biological index (BIX) and humification index (HIX) were used to judge characteristic of DOM origination. These indexes indicated that, DOM in Nanfei River had both the characteristics of humus and autogenous, but neogene autogenic feature was stronger, which was largely due to mixture of water, resuspension and desorption of DOM in sediments and photochemical degradation. In addition, the characteristic parameter of molecular mass of DOM (the values of M) had an obvious linear relationship with the fluorescence intensity ratio of fulvic acid-like to humic acid-like (C1/C3), indicating that macromolecular substances could be removed by adding or improving membrane treatment. These provided technical support for improving quality and comprehensive treatment of drinking water sources.

Aluminum distribution heterogeneity and relationship with nitrogen, phosphorus and humic acid content in the eutrophic lake sediment

Increasing amount of aluminum (Al) gets into aquatic ecosystem through anthropogenic activity, but the knowledge about Al migration and relationships with sediments possessing different physico-chemical properties in eutrophic lakes is limited. Here, the Al migration rule and relationships with sediment nutritions in the Hangzhou West Lake, China was investigated, where a certain amount of residual Al-salts can enter because of the pre-treatment of the Qiantang River diversion project every day. Results revealed the obvious spatial distribution heterogeneity of Al in sediment vertical direction and horizontal direction following water flow. The Al content in sediment ranged 0.463–1.154 g kg−1 in Maojiabu Lake, and ranged 9.862–40.442 g kg−1 in Xiaonanhu Lake. Higher Al content distributed in upper layer sediment in lake with more disturbance. Total nitrogen (TN) contents were higher 0.917–3.387 mg g−1 and 0.627–0.786 mg g−1 in upper layer sediment than that in lower layer in Maojiabu Lake and Xiaonanhu Lake, respectively. Total phosphorus (TP) content ranged 0.779–2.580 mg g−1, in which IP and Fe/Al-P contributed 24.9–80.8% and 17.0–51.6%, respectively. Correlations between Al content with nutrition, humic acid (HA) etc. of sediment regionally varied in Maojiabu and Xiaonanhu Lake. Spatial distribution of Al-salt in eutrophic lakes closely related with the physico-chemical characteristics of nutrients, humus, human disturbance and water division parameters. Results provides new insight into Al-salts migration and references for Al-risk evaluating in eutrophic lakes.

Community Structure Characteristics of nirS Denitrifying Bacteria of Spring Typical Parkland Waterbodies in Shijiazhuang City

Four typical park water bodies located in the main urban area of Shijiazhuang city were selected to study the relationships between water quality and the community structure and diversity of nirS denitrifying bacteria. The results showed that the nitrogen concentration ranged from 4.43 to 13.83 mg·L-1 in four park water bodies, which exhibited notable nitrogen pollution characteristics. Based on the characteristic index analysis of three-dimensional fluorescence spectra, the four park water bodies all exhibited strong autochthonous components and low humus characteristics. The results of Illumina high-throughput sequencing indicated that most of the nirS denitrifying bacteria showed significant differences in dominant genus. The unclassified_Bacteria (53.52%), Pseudomonas (60.48%), and Rhodobacter (46.94%) were the dominant bacteria in Yuxi park, Shuishang park, and Chang'an park, respectively. In comparison, unclassified_Bacteria (36.19%) and unclassified_Proteobacteria (23.44%) were the dominant bacteria in Shiji park. Redundancy analysis showed that denitrification bacteria in Yuxi park were mainly affected by nitrate, total nitrogen, and dissolved oxygen; denitrification bacteria in Shuishang park were greatly affected by total phosphorus; denitrification bacteria in Chang 'an park were mainly affected by ammonia and nitrous nitrogen; and denitrification in Shiji park were mainly affected by total phosphorus, nitrite, and ammonia. Overall, the water quality and the community structure of nirS denitrification bacteria exhibited significant differences in park water bodies. Further research could contribute to the understanding of water quality characteristics and the denitrifying community structure of urban water systems, and develop efficient denitrifying bacterial agents.

Features of Transformation of Humic Substances in Soddy-Podzolic Soil Disturbed by Main Pipeline Construction

The effect and aftereffect of main pipeline construction on the characteristics of humus and features of its distribution over the particle-size fractions of soddy-podzolic soil are studied. The features of technogenic degradation of humus and the degree of their manifestation compared to the control soil in different observation periods are characterized with respect to the specifics of the ecological situation.

Changes in the chemical properties and characteristics of humus in soddy-podzolic soil due to main pipeline construction

The multiyear dynamics of the acid–base parameters and humus characteristics of soddy-podzolic soil affected by main pipeline (MP) construction was studied. Distinctions between the properties of technogenically disturbed soil and soil unaffected by MP construction observed 1, 10, 15, and 30 years after construction have been characterized. The deterioration of physical and chemical properties and clearly displayed features of technogenic degradation of humus have been identified throughout the entire observation period.

Comportamiento poblacional de Eisenia foetida y calidad fisicoquímica del humus en diferentes sustratos del trópico húmedo

Se evaluó el comportamiento poblacional de la lombriz Eisenia foetida (Adultas- huevos) así como la calidad fisicoquímica del humus, proveniente de tres sustratos (ovino, bovino, cachaza) y sus combinaciones, con el objetivo de determinar el sustrato con mayor calidad fisicoquímica de acuerdo con la norma NMX-FF-109-SCFI-2008. La mayor dinámica poblacional se encontró en el tratamiento combinado de ovino+bovino+cachaza. El pH con rango aceptable (8.4 y 8.3) se observó en ovino y bovino, las demás tratamientos mostraron rangos altos de alcalinidad, reflejados en la conductividad eléctrica. La Materia Orgánica de todos los tratamientos se localizó en un nivel admisible (29 a 33%). El nitrógeno se mantuvo en niveles críticos (1.15 a 1.41%), mientras que el fosforo, el hierro, el magnesio y el zinc se conservaron en niveles superiores. La concentración de potasio fue satisfactoria en los tratamientos de bovino, ovino+cachaza, bovino+cachaza, ovino+bovino+cachaza. Por el contrario, el cobre estuvo en niveles tóxicos en todos los tratamientos, con concentraciones mayores de 20 mg kg-1. El manganeso solo se encontró en niveles aceptables en los tratamientos de ovino, ovino+cachaza, ovino+bovino+cachaza; ubicándose en un rango toxico en los demás tratamientos. Se consideró que el mejor sustrato de acuerdo con sus características fisicoquímicas fue ovino+bovino+cachaza. Se considera pertinente investigar en el desarrollo de las plantas.

Moisture effect on soil humus characteristics in a laboratory incubation experiment

Li C., Gao S., Zhang J., Zhao L., Wang L. (2016): Moisture effect on soil humus characteristics in a laboratory incuba tion experiment. Soil & Water Res., 11: 37–43. A 180-day laboratory incubation experiment (30°C) was conducted to investigate the quantitative and qualitative characteristics of humic fractions in a Mollisol at different moisture conditions. The soil moisture contents were 30, 60, and 250% field water-holding capacity (WHC), which represented the low, middle, and high moisture levels, respectively. The results showed that the carbon contents of the total soil and corresponding humic fractions gener ally decreased with increasing soil moisture. A significant difference was observed between the 250% WHC and the two other moisture levels. By contrast, the carbon content of the water soluble fraction significantly increased with increasing soil moisture levels. The solid-state 13 C nuclear magnetic resonance (NMR) spectra showed that the alkyl C/O-alkyl C, aliphatic C/aromatic C, and hydrophobic C/hydrophilic C ratios were in the order of 250% WHC > 30% WHC ≈ 60% WHC, 30% WHC ≈ 60% WHC > 250% WHC and 250% WHC > 60% WHC ≈ 30% WHC for humic acid, and 250% WHC > 30% WHC ≈ 60% WHC, 60% WHC ≈ 250 % WHC > 30% WHC and 30% WHC ≈ 250% WHC > 60% WHC for humin, respectively. These results indicated that a high moisture level was unfavourable for the carbon accumulation of the total soil and humic fractions, whereas it was favourable for the accumulation of water soluble carbon. Although soil moisture levels had a distinct effect on the chemical composition of humic acid and humin, the decomposition degree of the two humic substances components, as indicated by the alkyl C/ O-alkyl C ratio, were both higher at a high moisture level than at a low moisture level. Therefore, the lower soil organic carbon content at a high moisture level than at a low moisture level can be ascribed to the higher water soluble carbon content and larger decomposition degree of humic acid and humin in the former. Our results are important for understanding the behaviour and mechanisms of humic substances at specific soil moisture conditions.

From humic substances to soil organic matter–microbial contributions. In honour of Konrad Haider and James P. Martin for their outstanding research contribution to soil science

Many decades of research have shown that humic compounds as part of the soil organic matter (SOM) are essential for the stability and ecosystem services of soils. James P. Martin and Konrad Haider based on several pioneers in humus research improved the basis for the current knowledge of key processes in the soil environment, in particular structure and formation of humus triggered mainly by soil fungi. Other major contributions are briefly described but not in the focus of this article, such as their innovative tracer experiments with isotope-labelled xenobiotic chemicals and natural litter to study their fate. Both scientists inspired generations of younger researchers to advance their approaches and laid the cornerstone of the current understanding of soil organic matter formation. This article values the key experiments of Martin and Haider in this field and the related follow-up research finally resulting in the current view on formation mechanisms of SOM and non-extractable residues (NER) of xenobiotics. The improved understanding of these processes considering necromass with tissue residues of plants, microbes and animals challenges the traditional views of humic matter as macromolecular organic matrix, which according to the research of the last years represents only a variable part of the total organic matter besides associates of low molecular weight molecules. We discuss views on soil organic matter and humic substances that are nowadays considered not to differ in molecular diversity. We will start by demonstrating the understanding of humus characteristics and humus formation three decades ago closely related to the findings of Martin and Haider. Methodological approaches to characterize relevant structural and mechanistic pictures of SOM such as the priming effect, clay mineral catalysed reactions and the various mechanisms by which natural and xenobiotic chemicals are protected in soil are briefly illustrated by examples. Fungal activities in producing secondary metabolites like polyketides and their probably minor contributions to SOM formation are presented. Open research questions stimulated by these two soil scientists are sketched which are nowadays possible to address by new sophisticated high-resolution techniques.

The Physical and Biochemical Peculiarities of Representative Soils in Giurgeu Mountains

Abstract The analyses for the description of physic-chemical and humus fractional characteristics have been determined for two soil subtypes, respectively four soil profiles, that are representative for the lower altitudes area of Giurgeu Mountains. The analysis has been based on: one Andi-Eutric Cambisols (EC an- 920 m alt.) and three Cambic Andosols (AN ca) situated at different altitudes: 1120-1140 m, 1197 m and 1310 m. The purpose of the research is to indentify some quantitative and qualitative differences in regards to some organic and inorganic components from the soil. Have come into prominence the sum of exchangeable bases, the total acidity exchange, the degree of base saturation and other aspects related to organic accumulation (the highest in Cambic Andosols: 1120-1140 m alt.), degree of humification (higher for the same Andosol and variable for the one from 1310 m alt.), the distribution curve on the profile of chemical and biochemical humic components. In terms of quality, there are differences in regard to the humification degree of organic matter, the dynamic on the profile of the main humus fractions (humic acids, fulvic acids, non-extractable material) forming the horizons of accumulation for some of the fractions.

Humus characteristics and seasonal changes of soil arthropod communities in a natural sessile oak (Quercus petraea L.) stand and adjacent Austrian pine (Pinus nigra Arnold) plantation

In order to assess the effects of conversion of natural stands into plantations, soil invertebrate micro- and macroarthropod communities were evaluated for their abundance and richness in a sessile oak (SO; Quercus petraea L.) stand and adjacent Austrian pine (AP; Pinus nigra Arnold) plantation. Sites were sampled four times a year in 3-month intervals from May 2009 to February 2010. Humus characteristics such as total mass; carbon, lignin, and cellulose contents; and C/N ratio were significantly different between SO and AP. Statistically significant differences were detected on soil pH, carbon and nitrogen contents, and electrical conductivity between the two sites. The number of microarthropods was higher in AP than in the SO site. The annual mean abundance values of microarthropods in a square meter were 67,763 in AP and 50,542 in SO, and the annual mean abundance values of macroarthropods were 921 m(-2) in AP and 427 m(-2) in SO. Among the soil microarthropods, Acari and Collembola were the dominant groups. Shannon's diversity index was more affected by evenness than species number despite the species diversity (H') of soil arthropods being generally higher in the SO stand. The abundance of microarthropods showed clear seasonal trends depending upon the humidity of the soil.