Impact of PAH on biological health parameters of soils of an Indian refinery and adjoining agricultural area—a case study

The present study is aimed at analysing and comparing different soil enzymes in soil samples of native contaminated sites of a Mathura refinery and adjoining agricultural land. Enzyme activities are considered as indicators of soil quality and changes in biogeochemical function due to management or perturbations. Soil samples were collected from the premises and nearby area of Mathura refinery, India. Biological health parameters (dehydrogenase, aryl esterase, aryl sulphatase, \upbeta \upbeta -glucosidase, alkaline phosphatase, acid phosphatase, lipase, laccase and catalase activity) were estimated in the soil samples. Among all the samples, sewage sludge soil showed maximum activity of enzymes, microbial biomass carbon and most probable number of polycyclic aromatic hydrocarbon (PAH) degraders in soils spiked with three- to four-ring PAHs at 50 ppm. Available phosphorus, potassium and nitrogen was also exceptionally high in this sample, indicating maximum microbial bioconversion due to presence of nutrients stimulating potent PAH-degrading microorganisms.     

The interactions between tree-herb layer diversity and soil properties in the oriental beech (<Emphasis Type="Italic">Fagus orientalis</Emphasis> Lipsky) stands in Hyrcanian forest

This study investigated the interactions between tree-herb layer diversity and some physico-chemical and eco-physiological characteristics of soil in natural oriental beech stand in western Guilan, Iran. The data were collected from nine research sites (50 m?×?50 m) which were described as a gradient from pure oriental beech (Fagus orientalis Lipsky) stands to mixed stands with up to nine deciduous tree species (n =?27) in Hyrcanian forest. Herbaceous plants were sampled within ten 1 m?×?1 m sub-plots in two plots of 400 m² which were installed randomly in each research site. Composite soil samples were taken at five positions in each research site. We found that the increase in tree diversity in mature oriental beech stands brought about an increase in microbial biomass carbon, soil carbon content, and the ratio of microbial biomass carbon to the organic carbon (C_mic/C_org). Increased soil organic carbon raised microbial biomass carbon through creating suitable environment for microorganisms. The findings also indicated that the ratio of microbial biomass carbon to the organic carbon (C_mic/C_org) increased as a quantitative indicator of soil carbon dynamics that finally benefits soil fertility of mixed oriental beech stands compared to pure oriental beech stands. The results showed that humus layer and litter thickness were negatively correlated with tree layer richness. Generally, it can be stated that maintaining a mixture of tree layer species in natural oriental beech stands results in an increase in richness and diversity values of herb plants as well as carbon content and microbial biomass carbon of soil.     

Comparing the natural variation of oribatid mite communities with their changes associated with anthropogenic disturbance

Several organism communities serve as ecological and environmental indicators to detect changes in human-impacted habitats. However, the composition of indicator communities may vary because of natural variation in addition to the changes associated with human disturbances. This meta-analysis compared the natural variation of oribatid mite assemblages, a good indicator model group in soil ecosystems, with their deviations associated with disturbance using diversity and dissimilarity indices and three human disturbance types. Literature data were collected about oribatid mite assemblages from natural and disturbed habitats. Human disturbances consisted of agriculture, heavy metal pollution and forest management. Biodiversity indices (Shannon and Berger-Parker) and dissimilarity indices (Jaccard and Bray-Curtis) were calculated among natural habitats and between disturbed and control habitats at the species and genus level. We considered oribatid mite assemblages as effective community-level indicators when the methods separated the differences of assemblages between disturbed and control habitats from their varieties among natural habitats. In addition, the study analysed the correlation between these indices and environmental variables of the study sites. Oribatid mite assemblages performed high indication strength with Bray-Curtis index for agricultural disturbances since dissimilarity values between disturbed and control habitats were as high as between different natural habitats and higher than among the same types of natural habitats. Genus-level values showed similar results to the species level. This approach may be useful to test the effectiveness of other indicator groups and methods.     

An assessment of microbial communities associated with surface mining-disturbed overburden

To assess the microbiological changes that occur during the maturation of overburden that has been disturbed by surface mining of coal, a surface mining-disturbed overburden unit in southeastern Ohio, USA was characterized. Overburden from the same unit that had been disturbed for 37 and 16 years were compared to undisturbed soil from the same region. Overburden and soil samples were collected as shallow subsurface cores from each subregion of the mined area (i.e., land 16 years and 37 years post-mining, and unmined land). Chemical and mineralogical characteristics of overburden samples were determined, as were microbial respiration rates. The composition of microbial communities associated with overburden and soil were determined using culture-independent, nucleic acid-based approaches. Chemical and mineralogical evaluation of overburden suggested that weathering of disturbed overburden gave rise to a setting with lower pH and more oxidized chemical constituents. Overburden-associated microbial biomass and respiration rates increased with time after overburden disturbance. Evaluation of 16S rRNA gene libraries that were produced by “next-generation” sequencing technology revealed that recently disturbed overburden contained an abundance of phylotypes attributable to sulfur-oxidizing Limnobacter spp., but with increasing time post-disturbance, overburden-associated microbial communities developed a structure similar to that of undisturbed soil, but retained characteristics of more recently disturbed overburden. Our results indicate that over time, the biogeochemical weathering of disturbed overburden leads to the development of geochemical conditions and microbial communities that approximate those of undisturbed soil, but that this transition is incomplete after 37 years of overburden maturation.     

Assessment of soil nitrogen and related enzymes as influenced by the incorporation time of field pea cultivated as a catch crop in Alfisol

The effect of the time of catch crop (field pea) incorporation [catch crop incorporated in the autumn (A) or in the spring (B) versus plots without a catch crop (C)] on the soil enzymes related to N transformation (urease – UR, protease – PRO, nitrate reductase – NR, arginine ammonification rate – AAR), the total N and mineral N as well as microbial biomass N (MBN) contents were investigated in a 3-year experiment. The catch crop was sown at the beginning of August and plowed in the autumn in 2008, 2009 and 2010 or left as mulch during the winter. Soil samples for microbial activity were taken from spring barley plots that were grown in 2009, 2010 and 2011 before sowing (March), during the tillering phase (May), shooting (June) and after the harvesting of spring barley (August). The use of catch crop significantly increased the soil mineral and MBN contents as well as the activities of PRO and NR as compared to the control soil. The spring incorporation of the field pea significantly increased the MBN content in contrast to the autumn application, while the activity of N-cycle enzymes were clearly unaffected (UR and AAR) regardless of the time of the incorporation of field pea or else the results were inconsistent (PRO and NR). When the catch crop was incorporated in the spring, a significantly higher content of mineral N as compared to autumn incorporation was noted on only two of the four sampling dates. The enzymatic activity (PRO and AAR) was about 1.3-2.8 times higher in May and June as compared with March and August. Both spring or autumn incorporation of catch crop can be a useful management practice to increase the soil mineral N content and enhance the soil biological activity.     

Impact of degradation on nitrogen transformation in a forest ecosystem of India

A study was performed selecting one protected forest and an adjacent degraded forest ecosystem to quantify the impact of forest degradation on soil inorganic nitrogen, fine root production, nitrification, N-mineralization and microbial biomass N. There were marked seasonal variations of all the parameters in the upper 0–10 and lower 10–20 cm depths. The seasonal trend of net nitrification and net N-mineralization was reverse of that for inorganic nitrogen and microbial biomass N. Net nitrification, net N-mineralization and fine root biomass values were highest in both forests during rainy season. On contrary, inorganic nitrogen and microbial biomass N were highest during summer season. There was a marked impact of forest degradation on inorganic nitrogen, fine root production nitrification, N-mineralization and microbial biomass observed. Soil properties also varied with soil depth. Fine root biomass, nitrification, N-mineralization and microbial biomass N decreased significantly in higher soil depth. Degradation causes decline in mean seasonal fine root biomass in upper layer and in lower depth by 37% and 27%, respectively. The mean seasonal net nitrification and N-mineralization in upper depth decreased by 42% and 37%, respectively and in lower depth by 42.21% and 39% respectively. Similarly microbial biomass N also decreased by 31.16% in upper layer 33.19% in lower layer.     

Changes in soil microbial biomass and aggregate stability under different land uses in the northeastern Turkey

The characteristics of three neighboring soils from the NE of Turkey were evaluated in order to elucidate the effect of different land-use management on the soil aggregate stability and microbial biomass in Galyan-Atasu dam watershed. Three experimental sites corresponding to three land uses were selected. The first site is a hazelnut orchard (agriculture), the second site is a forest dominated by mature coniferous trees, and the third site is grassland. Soil aggregate stability values for the 1–2-mm aggregates increased from forest (lowest) to agriculture (highest) in the current study. The percentage of clay was highest in agriculture soils with 33.57 %, and overall stability values increased according to soil clay content. The lower aggregate stability in the forest soils probably reflects the highly silty texture soils with 11.95 % compared to agriculture and grassland. However, in our study, there were no significant correlations between aggregate stability and organic C concentrations either in cultivated or forested soils. Aggregate stability depended more on the organic matter content when the organic matter content was greater than 50 or 60 mg g^?1. Below that threshold, aggregate stability may be mainly related to clay content. Furthermore, the results confirmed that higher percentages of Cmic/Corg in agricultural soils are the result of more labile organic substrates maintained in the soil, allowing a higher microbial biomass C per unit of soil organic C. This work gives a better understanding of the relationships between land-use type and soil aggregation and allows to know the soil response to different types of management in humid environments.     

Response of soil invertebrates to disturbance across three resource regions in North Carolina

We evaluated the potential of soil microarthropods and enchytraeid worms to be useful as bioindicators of soil condition in forest, wetland, and agricultural ecosystems over a range of ecoregions. Selected mesofauna and soil characteristics in soil and litter in relatively undisturbed and disturbed examples of each of three ecosystems within each of three land resource regions were monitored over two years. Optimal times of year to sample these organisms as indicators of disturbance were April, May, July and September. No single measure reflected disturbance across all three ecosystems. Among forest sites, Simpson's diversity index, evenness, abundance of ants, and proportion of enchytraeids in the mesofauna differed between soils of different disturbance levels. Among agricultural sites, richness, evenness, abundance of mites, and proportions of collembolans and of enchytraeids in the mesofauna differed between disturbance levels. Among wetland sites, Shannon's and Simpson's diversity indices, richness based on the total mesofauna, and abundances of mites, diplurans, ants, and isotomid and onychiurid collembolans differed between disturbance levels. Covariates most frequently associated with abundance and diversity of the measured mesofauna were soil electrical conductivity, available N, organic matter, and pH. Canonical correspondence analysis provided information somewhat different to bivariate analysis. Using both approaches to examine soil and litter taxa that have distinctive responses to disturbance may help to identify candidate groups applicable for use in large-scale environmental monitoring programs.     

Effects of wetland recovery on soil labile carbon and nitrogen in the Sanjiang Plain

Soil management significantly affects the soil labile organic factors. Understanding carbon and nitrogen dynamics is extremely helpful in conducting research on active carbon and nitrogen components for different kinds of soil management. In this paper, we examined the changes in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) to assess the effect and mechanisms of land types, organic input, soil respiration, microbial species, and vegetation recovery under Deyeuxia angustifolia freshwater marshes (DAMs) and recovered freshwater marsh (RFM) in the Sanjiang Plain, Northeast China. Identifying the relationship among the dynamics of labile carbon, nitrogen, and soil qualification mechanism using different land management practices is therefore important. Cultivation and land use affect intensely the DOC, DON, MBC, and MBN in the soil. After DAM soil tillage, the DOC, DON, MBC, and MBN at the surface of the agricultural soil layer declined significantly. In contrast, their recovery was significant in the RFM surface soil. A long time was needed for the concentration of cultivated soil total organic carbon and total nitrogen to be restored to the wetland level. The labile carbon and nitrogen fractions can reach a level similar to that of the wetland within a short time. Typical wetland ecosystem signs, such as vegetation, microbes, and animals, can be recovered by soil labile carbon and nitrogen fraction restoration. In this paper, the D. angustifolia biomass attained natural wetland level after 8 years, indicating that wetland soil labile fractions can support wetland eco-function in a short period of time (4 to 8 years) for reconstructed wetland under suitable environmental conditions.     

Restoration of areas degraded by alluvial sand mining: use of soil microbiological activity and plant biomass growth to assess evolution of restored riparian vegetation

River or alluvial sand mining is causing a variety of environmental problems in the Itajaí-açú river basin in Santa Catarina State (south of Brazil). When this type of commercial activity degrades areas around rivers, environmental restoration programs need to be executed. In this context, the aim of this study was to assess the evolution of a restored riparian forest based on data on the soil microbial activity and plant biomass growth. A reference site and three sites with soil degradation were studied over a 3-year period. Five campaigns were performed to determine the hydrolysis of the soil enzyme fluorescein diacetate (FDA), and the biomass productivity was determined at the end of the studied period. The variation in the enzyme activity for the different campaigns at each site was low, but this parameter did differ significantly according to the site. Well-managed sites showed the highest biomass productivity, and this, in turn, showed a strong positive correlation with soil enzyme activity. In conclusion, soil enzyme activity could form the basis for monitoring and the early prediction of the success of vegetal restoration programs, since responses at the higher level of biological organization take longer, inhibiting the assessment of the project within an acceptable time frame.     

Ground vegetation monitoring in Swiss forests: comparison of survey methods and implications for trend assessments

At Swiss long-term forest ecosystem research sites, ground vegetation was assessed during the period 1994-2003/2008 following two approaches: (1) visual assessment of the cover of species occurring in sixteen 1 m(2) quadrats, distributed over a 43 × 43 m area, and (2) phytosociological relevés in concentric circular plots of 30, 200, and 500 m(2). We first compared the two approaches with respect to diversity assessment. The number of species recorded in the 16 quadrats was in general higher than in the 30 m(2) plot and it represented 42% to 108% of the number of species recorded in the 500 m(2) plot. In a second step, we tested whether any temporal trends were apparent. In a few cases, a decrease or increase in Landolt's mean indicator values for light, nitrogen availability, soil pH, soil moisture, or temperature was found to be significant. However, these changes were usually restricted to one approach or one area. The only clear trend was detected in an unmanaged former coppice beech stand, for which all survey approaches indicated canopy closure. At another site, vegetation reacted to the local opening of the canopy following windthrow. In a third step, we compared the leaf area index (LAI), measured with an LAI-2000 instrument (Licor, Inc.) over each quadrat, with the indicator value of the vegetation for light (L). Within a site, there was no clear relationship between LAI and L values per quadrat. In contrast, across all sites, the relationship between LAI and L, averaged per site for all available years, was highly significant.     

Regional impact analysis of climate change on natural and managed forests in the Federal State of Brandenburg, Germany

A methodology for regional application of forest simulation models has been developed as part of an assessment of possible climate change impacts in the Federal state of Brandenburg (Germany). Here we report on the application of a forest gap model to analyse the impacts of climate change on species composition and productivity of natural and managed forests in Brandenburg using a statistical method for the development of climate scenarios. The forest model was linked to a GIS that includes soil and groundwater table maps, as well as gridded climate data with a resolution of 10 × 10 km and simulated a steady-state species composition which was classified into forest types based on the biomass distribution between species. Different climate scenarios were used to assess the sensitivity of species composition to climate change. The simulated forest distribution patterns for current climate were compared with a map of Potential Natural Vegetation (PNV) of Brandenburg.In order to analyse the possible consequences of climate change on forest management, we used forest inventory data to initialize the model with representative forest stands. Simulation experiments with two different management strategies indicated how forest management could respond to the projected impacts of climate change. The combination of regional analysis of natural forest dynamics under climate change with simulation experiments for managed forests outlines possible trends for the forest resources. The implications of the results are discussed, emphasizing the regional differences in environmental risks and the adaptation potentials of forestry in Brandenburg.     

Assessing the soil quality of alpine grasslands in the Qinghai-Tibetan Plateau using a modified soil quality index

Soil degradation has caused various problems on the planet. Human disturbance and land use changes always negatively affect soil quality. In this study, we used a modified soil quality index (SQI) to assess soil quality under differing degrees of human disturbance and land use. The alpine grasslands were studied at different levels of degradation [i.e., severely degraded grassland, heavily degraded grassland, moderately degraded grassland, and non-degraded grassland (NDG)] in a case study conducted in Qinghai-Tibetan Plateau (QTP) to test the feasibility of using the SQI. Fifteen chemical, physical, and biological soil parameters were measured in each type of grassland. Significant variations in SQI were found across the different types of grasslands according to severity of human disturbance and changes in land use. Urease, the ratio of microbial biomass nitrogen to total nitrogen, proteinase, and soil organic carbon were found to be the most important indicators for assessing soil quality. NDG had a higher SQI than the other three types of grasslands. It was concluded that SQI is effective for assessing the soil quality of alpine grasslands in the QTP. The intensity of human disturbance had a negative effect on soil quality in the QTP.     

铅锌矿区土壤微生物区系及酶活性调查

通过对四川省汉源县富泉乡万顺铅锌矿区土壤微生物区系及微生物活性的调查,结果表明,铅锌矿区土壤几种重金属含量明显高于临近非矿区土壤。该矿区土壤微生物区系组成和微生物活性显著不同于临近非矿区土壤,随着重金属含量的增加,土壤微生物数量、微生物多样性指数、微生物生物量碳以及纤维素分解强度均显著降低,但土壤基础呼吸却明显升高;土壤脲酶、碱性磷酸酶、多酚氧化酶对铅锌矿较为敏感,而蔗糖酶和过氧化氢酶受到的抑制作用不明显。     

Effects of decaying wood on eluviation,podzolization, acidification,and nutrition in soils with different moisture regimes

One possible impact of large accumulations of decaying wood on forest sites is an increase in (1) eluviation, podzolization and acidification of, and (2) leaching and loss of nutrients from, the soil directly under decaying wood. As an exploratory investigation, we sampled soils beneath forest floors with and without large accumulations of decaying wood (lignic and algnic forest floors respectively) on three soil moisture regimes. Nine sites were located, three in each of central British Columbia, east Vancouver Island, and east of Vancouver. Among the moist sites, there were no differences in Ae horizon thickness between the alignic and lignic forest floors. However, the Ae horizon was thicker beneath the lignic forest floors (mean 4.2 cm) compared to the alignic forest floors (mean 0.7 cm) in slightly dry and fresh sites. Lignic and alignic forest floors differed (p<0.01) in pH, total C, total N, mineralizable N, available S, available P, extractable Mg, K and Ca, lipids, C in fraction B (soluble polysaccharide fraction), C in humic acid, C in fulvic acid, and polyphenol C in fulvic acid for all soil moisture regimes. There were no significant differences in the measures of nutrients or indicators of podzolization as measured by organically complexed Fe and Al, the total non-crystalline Fe and Al, and the poorly crystalline Fe and Al, in the underlying 10 cm of the Bf horizon between the two substrates regardless of the soil moisture regime. Further investigations are needed to establish the relationships between soil productivity and the observed soil chemical measures.     

Metabolic and bacterial diversity in soils historically contaminated by heavy metals and hydrocarbons

The aim of this study was to characterize soils contaminated by different levels of heavy metals and hydrocarbons (Madonna Dell'Acqua, Pisa, Italy). The soils were chemically and biochemically analysed by measuring the standard chemical properties and some enzyme activities related to microbial activity (dehydrogenase activity) and the soil carbon cycle (total and extracellular beta-glucosidase activities). The metabolic capacities of soil microorganisms to degrade hydrocarbons through catechol 2,3-dioxygenase were also described. The microbial diversity of contaminated and uncontaminated soils was estimated by denaturing gradient gel electrophoresis (DGGE) of amplified 16S rDNA sequences. The PCR/single-strand conformation polymorphism (PCR/SSCP) method was used to estimate the genetic diversity of PAH-degrading genes in both contaminated and uncontaminated soils. A greater bacterial diversity and lower catechol 2,3-dioxygenase activity was detected in unpolluted soils. The complexity of the microbial community (Shannon and Simpson indices) as well as the dehydrogenase soil activity negatively correlated with contamination levels. The greatest PAH-degrading gene diversity and the most intense catechol 2,3-dioxygenase activity were found in the soils with the highest levels of hydrocarbons. Heavy metals and hydrocarbon pollution has caused a genetic and metabolic alteration in microbial communities, corresponding to a reduction in microbial activity. A multi-technique approach combining traditional biochemical methods with molecular-based techniques, along with some methodological improvements, may represent an important tool to expand our knowledge of the role of microbial diversity in contaminated soil.     

Sampling The Soil In Long-Term Forest Plots: The Implications Of Spatial Variation

Long-term monitoring of forest soils as part of a pan-European network to detect environmental change depends on an accurate determination of the mean of the soil properties at each monitoring event. Forest soil is known to be very variable spatially, however. A study was undertaken to explore and quantify this variability at three forest monitoring plots in Britain. Detailed soil sampling was carried out, and the data from the chemical analyses were analysed by classical statistics and geostatistics. An analysis of variance showed that there were no consistent effects from the sample sites in relation to the position of the trees. The variogram analysis showed that there was spatial dependence at each site for several variables and some varied in an apparently periodic way. An optimal sampling analysis based on the multivariate variogram for each site suggested that a bulked sample from 36 cores would reduce error to an acceptable level. Future sampling should be designed so that it neither targets nor avoids trees and disturbed ground. This can be achieved best by using a stratified random sampling design.     

Effect of vegetation change from native broadleaf forest to coniferous plantation on selected soil properties

The objective of this study was to examine the effects of vegetation change from a native broadleaf forest to a coniferous plantation on selected soil properties, including soil texture, pH, organic matter, total nitrogen (N), total phosphorus (P), exchangeable cations (Ca²⁺, K⁺, Na⁺), and cation exchange capacity (CEC). Results showed that the amount of clay particles, Ca²⁺, and K⁺ values significantly increased, whereas Na⁺, total N, and organic matter and soil pH values decreased on the treatment plot after vegetation change. Soil acidity also increased and soil textural group changed from moderately fine-textured soils (clay loam) to medium-textured soils (loam) under both control and treatment plots. Organic matter, total N, and Na⁺ values increased, whereas Ca²⁺ concentration decreased through time on the control plot. Soil pH, total P, K⁺, and CEC did not show significant changes through time on the control plot.     

Dynamics of Organic Carbon and Microbial Biomass in Alluvial Soil With Tillage and Amendments in Rice-wheat Systems

Rice-wheat cropping systems of the Indo-Gangetic plains (IGP) occupying 12 million ha of productive land are important for the food security of South Asia. There are, however, concerns that yield and factor productivity trends in these systems are declining/stagnating in recent years. Decrease in soil organic carbon is often suggested as a reason for such trends. A field experiment was conducted to study the soil organic carbon (SOC) and soil microbial biomass carbon (MBC) dynamics in the rice-wheat systems. Use of organic amendments and puddling of soil before rice transplanting increased SOC and MBC contents. Microbial biomass carbon showed a seasonal pattern. It was low initially, reached its peak during the flowering stages in both rice and wheat and declined thereafter. Microbial biomass carbon was linearly related to SOC in both rice and wheat indicating that SOC could be used as a proxy for MBC.     

Multiscale satellite and spatial information and analysis framework in support of a large-area forest monitoring and inventory update

Many countries undertake a national forest inventory to enable statistically valid monitoring in support of national and international reporting of forest conditions and change. Canada’s National Forest Inventory (NFI) program is designed to operate on a 10-year remeasurement cycle, with an interim report produced at the 5-year mid-point. The NFI is a sample-based inventory, with approximately 18,850 2 ×2-km photo plots across the country, distributed on a 20×20-km grid of sample points; these photo plots are the primary data source for the NFI. Capacity to provide annual monitoring information is required to keep policy and decision makers apprised of current forest conditions. In this study, we implemented a multistage monitoring framework and used a Moderate Resolution Imaging Spectroradiometer (MODIS) change product to successfully identify 78% of the changes in forest cover area that were captured with a Landsat change detection approach. Of the NFI photo plots that were identified by both the Landsat and MODIS approaches as having changes in forest cover, the proportion of change area within the plots was similar (R ²?=?0.78). Approximately 70% of the Landsat-derived change events occupied less than 40% of a single MODIS pixel, and more than 90% of the change events of this size were successfully detected with the MODIS product. Finally, MODIS estimates of the proportion of forest cover change at the NFI photo plot level were comparable to change estimates for the ecoregions as a whole (R ²?=?0.95). High-temporal, low-spatial resolution imagery such as MODIS, in combination with other remotely sensed data sources, can provide information on disturbance events within a national forest inventory remeasurement cycle, thereby satisfying the interim information needs of policy and decision makers as well as the requirements of national and international reporting commitments.