Changes In Humus Research Articles

Теоретичні і прикладні аспекти прогнозування стану ґрунтового покриву

Goal. To substantiate on the basis of generalization of the available experience theoretical aspects of forecasting changes in the state of soil cover and to develop models of forecasting changes in the basic physical, agrochemical, physicochemical properties of arable soils of Ukraine. Methods. Information-analytical, mathematical-statistical (correlation-regression, pedotransfer modeling). Results. Based on the analysis of literature sources, the relevance is proved of issues related to forecasting changes in the basic properties of arable soils of Ukraine to prevent the development of degradation processes and timely use of soil protection measures that will stabilize their fertility in modern conditions. The main methods of forecasting (expert, extrapolation, interpolation, etc.) are analyzed and the theoretical aspects of forecasting in soil science are substantiated. Using samples from the database «Soil Properties of Ukraine» they developed models for predicting changes in humus, physical, physicochemical, and agrochemical properties of arable soils. The main state priorities for technological measures to protect and stabilize the level of fertility of arable soils are proposed. Conclusions. It is established that with the preservation of the current level of relationships in the agrosphere, which is characterized by the development of degradation processes in conditions of existing deficit of essential nutrients, acidification and contamination of soils with radionuclides and heavy metals, forecasting changes in soil properties and biodiversity will remain negative. The main state priorities for technological measures to protect and stabilize the level of fertility of arable soils are outlined.

Pedogenesis: Humus forms and soils under spruce forest by a morphological approach

Our investigation pointed out, with a detailed classification, a vast variability of forest humus and soil under spruce forests on two different sites with North and South exposition, permitting to identify a pedogenetic trend between different sylvogenetic phases of forest evolution and specific humus forms.We identified the soil indicators that have to be checked for measuring soil changes relating to humus changing. First of all we noted a humus change on soil morphological features. Such features are produced by physical and biochemical pedofauna bioturbations. Pedofauna according to the peculiar microclimate of the soil, depends on the forest development. Biochemical litter environment produces specific humus form.During the growth of a forest there is a policyclic soil evolution with physical-chemical changes that we can observe in time on soil and humus forms. The humus forms are related with the air (biospheric fluxes), with the organic-mineral components (as micro and macroelements cycles) and with pedofauna. We observe physical change (as structure, porosity, horizontation, particle-size, pattern, mineralogy) and chemical change (as for pH, C, N) in soil horizons which is due to humus change.The humus forms have been investigated in relation to the development of vegetation growth, with the aim to identify a representative humus form of a specific sylvogenetic phase. Such research suggests an hypothesis that the humus form is a guide of the environment states to which it belongs. During the open canopy stage (that is the phase before the presence of very young plantations) it is possible to observe many different humus forms: from the acid one as Moder (Hemimoder), that is heredity of the previous use of the land, to the new form of Mull (Oligomull) that is the result of the new forest cycle, more suitable for spruce renovation.

FEATURES OF HUMUS AND NITROGEN ECOLOGICAL STATUS FOR STEPPE ZONE CHERNOZEMS OF THE NORTH CAUCASUS

The purpose of the paper presented is to determine tendency and intensity for quantitative and qualitative changes in humus and nitrogen status of chernozems. The system approach to study natural objects is assumed as the basis for research methodology of humus and nitrogen status of soils. It is established that the depth typical values of chernozem humus horizons in the North Caucasus are 120-180 cm for South European facies of leached chernozems, 100-170 cm for modal chernozems, 70-160 cm for common chernozems, 70-120 cm for southern chernozems; for East European facies of southern chernozems the value is 55-70 cm. A distinctive ecological feature of the soils is thought to be a low humus content in the arable layer, its deep distribution along the profile and slight variability among each subtype. Nitrogen quantity in chernozems of the region variates within a comparatively wide range: 0.20-0.35 % in South European facies of leached, modal and common chernozems, 0.22-0.30 % in East European facies of southern chernozems. Southern chernozems of South European facies contain least of all nitrogen, i.e., 0.18-0.22 %. Total nitrogen composition is mainly presented by non-hydrolysable facies, making 74.2-78.9 %. The research materials are intended to design farming systems on the landscape basis for specialists dealing with the issues of soil preservation, increasing soil fertility as well as environment protection. The results of the research may contribute to making a purposeful impact on decision making to control humus and nitrogen status of soils, thus serving as the basis for preservation of bioecological potential of chernozems.

PECULIARITIES OF HUMUS AND NITROGEN ECOLOGICAL STATE FOR STEPPE ZONE CHERNOZEMS OF THE NORTH CAUCASUS

Purpose of the paper presented is to determine tendency and intensity for quantitative and qualitative changes in humus and nitrogen of chernozems. System approach to study natural objects is assumed as the basis for research methodology of humus and nitrogen state of soils. It is established that the depth typical values of chernozem humus horizons in the North Caucasus are 120–180 cm for South European facies of leached chernozem, 100–170 cm for modal chernozems, 70–160 cm for common chernozems, 70–120 cm for sothern chernozems; for East European facies of southern chernozems it is 55–70 cm. A distinctive ecological feature of soils is a low humus content in an arable layer, its deep distribution along the profile and. slight variability among each subtype. Nitrogen quantity in chernozems of the region variates in comparatively wide ranges: in South European facies of leached, modal and common chernozems 0,20–0,35%, in East european facies of southern chernozems 0,22–0,30%. Southern chernozems of South European facies contain least of all nitrogen 0,18–0,22%. Tota1 nitrogen composition is presented in the main with nonhydrolysed facies – 74,2–78,9%. The research materials are intended to design farming systems on the landscape basis for specialists who are busy with the problem of conservation and increase in soil fertility and environment protection. The results of research allow to realize purposeful impact on decision making to control humus and nitrogen state of soils and this will serve as the basis for conservation of bioecological potential of chernozems.

Mathematical modeling as a tool for determination of tendencies in changes of humus concentration in soil of arable lands

Level of sustainability of agricultural production is characterized by balance of nutrients in soil. Using monitoring data, conducted by the State Institution “Institute of Soil of Ukraine”, nitrogen balance is calculated for two Ukrainian regions – Ternopil and Kirovograd Adding nutrients and removal of them with the harvest was taken into account. Particular attention has been given to nitrogen. Intensity of nitrogen balance in Kirovograd region was 64.5%, which indicates loss of humus – soil organic matter. Intensity of nitrogen balance in agricultural soil of Ternopil region was satisfactory – 108.1%. With the aim of soil humus state evaluation, a prognosis mathematical model was developed in Wolfram Mathematica 9 to estimate humus change in both regions.

Changes in humus properties and collembolan communities following the replanting of beech forests with spruce

Differences of collembolan communities within the organo-mineral A layer were studied in relation to physico-chemical changes in humus at nine sites of beech forests ( Fagus sylvatica L.) and first generation spruce stands ( Picea abies (L.) Karst.), planted on former beech forest 30 years ago (Central Pyrenees, France). Changes in humus form were caused by the spruce plantation and occurred mainly within the fermentation horizon where acidifying litter accumulation increased the horizon depth. The recent replacement of beech by spruce induced a shift from mull towards moder humus forms, which is explained by the decreasing organic matter turnover rate. A significant decrease in the three exchangeable cations and pH under spruce was also observed. Collembolan species diversity within the A horizon was significantly lower under spruce at this early stage of the silvogenetic cycle. Differences between species composition of Collembola between the two forest stands is related to changes in environmental conditions (e.g. nutrient availability, soil porosity, soil moisture). This study shows how forest management practices are susceptible to modify biological activity within the A horizon under exotic conifer plantations.

Effects of prolonged irrigation on the humus of steppe soils in southwest Siberia

Changes in humus resulting from up to 20 years' irrigation with slightly saline water were studied in dry steppe soils in southwest Siberia. The amounts of brown humic acids and of the Pg fraction increased with the period of irrigation, and their maximum amounts occurred at greater depths in the profile. Other fractions of humus and humic acids fluctuated within the limits typical of dry steppe soils. The humus therefore remained essentially stable under irrigation for up to 20 years.

Microbial communities in boreal coniferous forest humus exposed to heavy metals and changes in soil pH—a summary of the use of phospholipid fatty acids, Biolog® and 3H-thymidine incorporation methods in field studies

This paper summarises our recent field studies on the microbial communities of boreal coniferous forest humus exposed to environmental stress, heavy metals and changes in humus pH. The microbial community was measured using the phospholipid fatty acid (PLFA) and Biolog® analyses, and the actual factor in the environment exerting the selective pressure on the bacterial community was estimated with the help of tolerance determinations using the 3H-thymidine incorporation technique. The field experiments showed that the structure of the microbial community inhabiting the boreal coniferous forest humus was influenced by changes in humus pH and heavy metal concentrations at levels where no, or only small, effects on the microbial biomass or carbon mineralization rate were seen. The alterations in the humus PLFA patterns were related to the abundance of the major groups of microorganisms, bacteria and fungi. Changes in the relative proportions of Gram-negative and Gram-positive bacteria, including actinomycetes, were also shown. With the help of the 3H-thymidine incorporation technique, it was demonstrated that forest humus bacterial communities exposed to heavy metals or alterations in humus pH were able to adapt to the environmental disturbance in question. When combining the results from the PLFA and 3H-thymidine analyses, it was revealed that the increased tolerance of the humus bacterial community to heavy metals or to altered pH resulted at least partly from a change in microbial species composition. Coniferous forest humus seemed to contain a bacterial group, consisting mainly of Gram-positive bacteria, which were adapted more easily to the acidifying environment and a group of bacteria, mainly Gram-negative ones, which were more easily adapted to the humus with a higher pH. The Biolog® technique, which determines the community level physiological profile (CLPP) of the bacterial community was less sensitive and less suitable than the PLFA analysis to detect the characteristics of the forest humus microbial community. The 3H-thymidine incorporation technique was the most sensitive of the techniques used in this study to detect the influence of environmental disturbances on the microbial community. In addition, a gradient of coniferous forest stands having naturally different humus pH because of the different site properties was studied to compare these natural microbial communities with the communities subjected to anthropogenic change in humus pH. In order to reveal the similarity of the humus samples with respect to their community structure, the PLFA patterns from all the field studies were subjected to multivariate cluster analysis. The structure of the forest humus microbial community was shown to be strongly influenced by the indigenous fertility of the coniferous forest site type, which was in turn related to humus nutritional status, pH, moisture, tree species and ground vegetation. Thus, a prerequisite for successful determination of the impacts of environmental stress on forest humus microbial community is the homogeneity of the forest site types between the experimental plots.

Linking above‐ground and below‐ground effects in autotrophic microcosms: effects of shading and defoliation on plant and soil properties

Although factors affecting plant growth and plant carbon/nutrient balance – e.g., light availability and defoliation by herbivores – may also propagate changes in below‐ground food webs, few studies have aimed at linking the above‐ground and below‐ground effects. We established a 29‐week laboratory experiment (∼one growing season) using autotrophic microcosms to study the effects of light and defoliation on plant growth, plant carbon/nutrient balance, soil inorganic N content, and microbial activity and biomass in soil. Each microcosm contained three substrate layers – mineral soil, humus and plant litter – and one Nothofagus solandri var. cliffortioides seedling. The experiment constituted of the presence or absence of two treatments in a full factorial design: shading (50% decrease in light) and artificial defoliation (approximately 50% decrease in leaf area in the beginning of the growing season). At the end of the experiment a range of above‐ground and below‐ground properties were measured. The shading treatment reduced root and shoot mass, root/shoot ratio and leaf production of the seedlings, while the defoliation treatment significantly decreased leaf mass only. Leaf C and N content were not affected by either treatment. Shading increased NO 3–N concentration and decreased microbial biomass in humus, while defoliation did not significantly affect inorganic N or microbes in humus. The results show that plant responses to above‐ground treatments have effects which propagate below ground, and that rather straightforward mechanisms may link above‐ground and below‐ground effects. The shading treatment, which reduced overall seedling growth and thus below‐ground N use and C allocation, also led to changes in humus N content and microbial biomass, whereas defoliation, which did not affect overall growth, did not influence these below‐ground properties. The study also shows the carbon/nutrient balance of N. solandri var. cliffortioides seedlings to be highly invariant to both shading and defoliation.

Does short-term heating of forest humus change its properties as a substrate for microbes?

Prescribed burning is known to reduce the size of the microbial biomass in soil, which is not explained by preceding clear-cutting or the effects of ash deposition. Instead, burning induces an instant heat shock in the soil, which may either directly kill soil microbes or indirectly alter the soil organic matter. We heated dry forest humus at temperatures from 45 to 230°C, inoculated them to ensure equal opportunities for microbial proliferation and incubated the heated humus samples at 14°C. After 1, 2, 4 and 6 months we studied the microbial community structure of the samples by determining the phospholipid fatty acid pattern (PLFA), microbial substrate utilization pattern using Biolog Ecoplates and total microbial biomass ( C mic) by substrate-induced respiration (SIR). The chemical structure of humus was scanned by Fourier-transform infrared (FTIR) and 13C NMR spectroscopy. Heating at 230°C caused changes in the chemical structure of the humus as indicated by FTIR spectroscopy, increased the pH of the humus by 1.1 units, reduced C mic by 70% compared with the control and caused changes in substrate utilization patterns and proportions of PLFAs. More interestingly, the heat treatments from 45 to 160°C, which did not increase humus pH, resulted in differences in both microbial community structure and substrate utilization patterns. The severely heated samples (120–160°C) were relatively richer in 16:1 ω7 t, cy19:0 and 18:1 ω7, while the mildly heated samples (45–100°C) showed higher proportions of 16:1 ω5, 16:1 ω9, 10me16:0 and a15:0. The t/ c ratio calculated from trans and cis configurations of 16:1 ω7 increased from 1 to 6 months in the severely heated humus, possibly indicating nutrient deprivation. The control showed a decreasing t/ c ratio and a stable amount of C mic indicating sufficient amount of decomposable organic matter. After incubation for 1 month, similar amounts of C mic had reestablished in 160°C-treated and control samples. However, the C mic in 160°C-treated samples decreased over 5 months. This might have been caused by a heat-induced flush of easily decomposable carbon, which was later exhausted. We conclude that changes in chemical properties of humus during dry heating at 230°C were capable of causing changes in microbial community structure of the humus.

Clear-cutting and prescribed burning in coniferous forest: Comparison of effects on soil fungal and total microbial biomass, respiration activity and nitrification

The effects of clear-cutting (CC) and clear-cutting followed by prescribed burning (CC-B) on humus chemical and microbiological variables and quality were compared in a Norway spruce dominated stand in North-Eastern Finland. The pattern of chemical changes in humus was similar after both treatments but CC-B caused greater changes than CC. Treatments raised the pH, cation exchange capacity and base saturation compared to an untreated standing forest control (Ctr). Total microbial carbon (C mic) measured by substrate-induced respiration (SIR) and fumigation-extraction (FE) methods decreased following treatments. CC caused a 21% reduction of C mic compared to Ctr (10,890 μg g −1 dry wt), as measured by SIR, and a 27% reduction compared to Ctr (7281 μg g −1 dry wt) as measured by FE. CC-B resulted in 53 and 67% lower C mic than Ctr as measured by SIR and FE, respectively. Reasons for this decline in C mic are proposed. Fungal biomass determined as humus ergosterol concentration fell even more steeply than total C mic. Humus quality was analysed by near infrared reflectance spectroscopy (NIR) which revealed differences in humus structure between treatments. The NIR data could be interpreted to explain 75–82% of the variation in C mic-FE, C mic-SIR and ergosterol concentration. CC and CC-B lowered soil basal respiration, but not proportionally with the reduction in C mic since the specific respiration rate (CO 2-C evolved per unit C mic) was clearly higher with CC-B than CC or Ctr. CC and CC-B both resulted in a higher concentration of NH 4 + but only the humus from CC-B showed nitrification during a 6 week laboratory incubation.

The effect of forty years of continuous corn cropping on soil organic matter characteristics

Changes in humus and some of the major extractable components of soil organic matter were examined, following forty years of conventionally tilled continuous corn cropping compared with those of an adjacent untilled native grassland soil. Results indicate that long-term continuous cropping caused a significant reduction in the content of alkali extractable and water soluble carbon, as well as in the phenolic and chloroform extractable compounds, while no differences in volatile acids and n-hexane extractable substances were found. On the basis of organic C, corn cropping led to a relative enrichement of phenolic compounds, volatile acids and substances extractable by Na4P2O7, but it did not affect the substances extractable by water. Except for the humification ratio (HR), the humification parameters, such as humification degree (HD), the extracted humic and fulvic acids, the CHA/CFA ratio and the humification index (HI) revealed a higher degree of humification of the organic matter in native grassland than in the continuous corn cropping system. IR spectra of n-hexane, chloroform, alkaline and water extracts failed to show significant differences between sites under native grassland and sites under continuous corn.

Bioavailability of aluminium in the presence of humic substances at low and moderate pH

Fish kills have been observed in lakes with low pH and high Al content. The monomeric inorganic Al seems to be the most acute toxic fractions. Humic lake waters, situated in acidified areas, often have high values of aluminium. However, the fraction of Al bound to humus is regarded as a relatively nontoxic form of Al. As pH is decreasing, the physical and chemical properties of humus change. The molecular size, electronegativity and colour decrease. An important question in this matter is the potential change in bioavailability of “Al-humus” as Ph decreases. The bioavailability of the Al-humus complex was studied; in relation to surface water acidification and in relation to drinking water and human health. The work is based on the octanol/water partition coefficient (Khow), estimated by measuring the UV absorption at 254 nm. Al concentration is determined in the water phase and in the octanol phase. The results show that the amount of organic material soluble in the octanol phase relative to the amount in the aqueous phase increases with decreasing pH, while no Al is detected in the octanol phase. It is concluded that Al is only weakly bound to humus and consequently Al complexed with humus is of minor concern in bioaccumulation.