Multi-element analysis of an english peat bog soil

Nineteen elements were quantitatively determined by atomic emission spectroscopy with inductively coupled plasma in peat profiles in Ringinglow Bog, Derbyshire, England. For the elements Ba, Ca, Cd, Co, Cr, Fe, La, Mn, Ni, Ti, and Zn an enrichment in the upper 5 cm of the peat bogs was found probably caused by anthropogenic influences. The elements Al, Be, Cu, and Pb showed a different distribution pattern with maximum concentration in the 5 to 15 cm layer. The elements Mg, Na, and Sr showed no enrichment in the upper 55 cm of the peat reflecting the constant input of these elements from the sea during the last few centuries. Upper parts (leaves and stems) of the plants investigated (Calluna vulgaris and Eriophorum vaginatum) only represent higher values of Pb compared with the normal element content in other plants. Compared with the results of peat profiles in a Norwegian bog, the concentrations of the comparable elements (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) are much higher in the English peat. Ringinglow Bog seem to be very suitable for further investigations within the scope of a global monitoring programme.     

Shifts of archaeal community structure in soil along an elevation gradient in a reservoir water level fluctuation zone

Purpose

Although archaea play an important role in nutrients cycling, the archaeal community in a reservoir water-level fluctuation zone (WLFZ) remains unclear. An elucidation of archaeal community responding to the environmental variables is essential to understand the nutrients dynamics in WLFZ. This study focused on the response of the archaeal community structure and abundance to the periodic water flooding along an elevation gradient in the WLFZ of the Three Gorges Reservoir.

Materials and methods

Along the elevation gradient (152–175 m) of the study area, soil samples in the beginning and late stages of water flooding were collected to investigate the influence of water flooding on the archaeal community in soil, using quantitative PCR and Illumina high-throughput sequencing approaches.

Results and discussion

An increase of archaeal abundance from 3.8?×?10⁸ to 3.8?×?10⁹ copies (g d.w.s)^?1 on average was observed after water flooding. The archaeal abundance was positively correlated with the contents of ammonium, organic matter, and moisture in soil and with the accumulated flooding time. Higher diversity was observed in dry samples (non-flooded soil samples) rather than wet samples (flooded soil samples). The Thaumarchaeota were predominant in most of the dry samples. Interestingly, high proportions of Candidatus Nitrososphaera were observed in the transition zone, while euryarchaeotal methanogens dominated the wet samples. The proportion of methanogens decreased dramatically in the dry samples at higher elevations, which was associated with the decrease of the moisture content and the probably increase of available oxygen in soil.

Conclusions

Archaeal abundance, diversity, and community composition shifted along an elevation gradient and were influenced by water flooding. The increased archaea abundance after water flooding and elevation related community composition and diversity indicated that water flooding was a key dynamic environmental variable in the WLFZ.

     

Natural and anthropogenic enrichments of As,Cu, Pb,Sb, and Zn in ombrotrophic versus minerotrophic peat bog profiles,Jura Mountains,Switzerland

Peat cores were taken from two contrasting Sphagnum bogs in the Jura Mountains of Switzerland. At Etang de la Gruyere (EGr), 6.5 m of peat has accumulated during the past 10,000 years. In the first 100 cm of this profile there are several distinct peaks in ash content, but the values are well within the range for typical ombrotrophic Sphagnum bogs. There is also considerable variation in the concentrations of major and trace lithogenic metals (Al, Ti, Sc, Ca, Mg, Rb, and Sr), but most of this is simply a reflection of the natural variations in the amount of mineral matter in the peats. The Ca/Mg molar ratios in the peats at EGr are comparable to or lower than the average rainwater composition in this area, showing that this section of the peat core is ombrotrophic (i.e. rainwater-fed). In other words, the inorganic constituents in the surface peats at EGr were supplied exclusively by atmospheric deposition. This peat core, therefore, is suitable for studying the historical record of atmospheric metal deposition. Arsenic, Cu, Pb, Sb, and Zn are all more abundant in surface and near surface peat layers compared to deeper parts of the profile. Enrichment factors (EFs) for the profile were calculated conservatively by normalizing the metal/Sc ratios of individual peat samples to the average of the five lowest metal/Sc ratios in this part of the core (69–84 cm); these are tentatively assumed to represent pre-Industrial background values. The maximum EFs are approximately 5 times for Cu, 15 times for As, and 30 to 50 times for Pb, Sb, and Zn. At La Tourbière des Genevez (TGe), 1.5 m of peat represents 4,800 years of peat formation. At this site, the ash contents are higher and increase progressively with depth to values which are characteristic of minerotrophic fen peats. The concentration profiles of Al, Ti, Sc, Ca, Mg, Rb, Sr show the same general trend. The Ca/Mg molar ratios of these peats are generally twice the rainwater average, showing that this bog is essentially minerotrophic (ie groundwater-fed). Thus, the inorganic cccstituents in these peats were provided by both atmospheric and hydrospheric processes. Despite this, the Cu, Pb, Sb, and Zn concentrations are generally very similar to those at EGr, especially in the uppermost part of the profile, indicating that recent atmospheric inputs also dominate the supply of these metals to this bog. However, the minimum Pb and Sb concentrations in this profile are approximately five times higher than the corresponding values at EGr. The minerotrophic profile at TGT, therefore, could not by itself be used to calculate rates of atmospheric Pb and Sb deposition because it is impossible to distinguish between atmospheric and hydrospheric metal inputs. At TGe, As concentrations increase continuously with depth, reaching concentrations in the deeper, older peats which are more than 50 times higher than the ‘background’ As values at EGr. At this site the natural supply of As by mineral soil water completely masks the recent, elevated inputs contributed by atmospheric deposition. Thus, the peat core from TGe is also unsuitable for studying atmospheric As deposition.     

Functioning of microbial complexes in aerated layers of a highmoor peat bog

Monitoring was carried out using the luminescent-microscopic method of the abundance parameters of different groups of microorganisms in a monolith and in the mixed layers of a highmoor peat bog (oligotrophic residual-eutrophic peat soil) in a year-long model experiment. The increase of the aeration as a result of mixing of the layers enhanced the activity of the soil fungi. This was attested to by the following changes: the increase of the fungal mycelium length by 6 times and of the fungal biomass by 4 times and the double decrease of the fraction of spores in the fungal complex. The response of the fungal complex to mixing was different in the different layers of the peat bog. The maximal effect was observed in the T1 layer and the minimal one in the T2 layer. The emission of CO₂ in the mixed samples was 1.5–2 times higher than that from the undisturbed peat samples. In contrast with the fungi, the bacteria and actinomycetes were not affected by the aeration of the highmoor layers.     

Differences in the activity and bacterial community structure of drained grassland and forest peat soils

The microbial activity and bacterial community structure were investigated in two types of peat soil in a temperate marsh. The first, a drained grassland fen soil, has a neutral pH with partially degraded peat in the upper oxic soil horizons (16% soil organic carbon). The second, a bog soil, was sampled in a swampy forest and has a very high soil organic carbon content (45%), a low pH (4.5), and has occasional anoxic conditions in the upper soil horizons due to the high water table level. The microbial activity in the two soils was measured as the basal and substrate-induced respiration (SIR). Unexpectedly, the SIR (μl CO₂ g⁻¹ dry soil) was higher in the bog than in the fen soil, but lower when CO₂ production was expressed per volume of soil. This may be explained by the notable difference in the bulk densities of the two soils. The bacterial communities were assessed by terminal restriction fragment length polymorphism (T-RFLP) profiling of 16S rRNA genes and indicated differences between the two soils. The differences were determined by the soil characteristics rather than the season in which the soil was sampled. The 16S rRNA gene libraries, constructed from the two soils, revealed high proportions of sequences assigned to the Acidobacteria phylum. Each library contained a distinct set of phylogenetic subgroups of this important group of bacteria.     

Migration of oil and its components along the profile of high-moor peat soil under model experimental conditions

It was found in a model experiment that high-moor peat has a high sorption capacity for oil, as well as for its most migration-capable components (aromatic hydrocarbons and their derivatives). Benzene was more involved in migration with water than phenol, which can be related to the formation of molecular complexes with fulvic acids. The results obtained agree with the low contamination of surface waters near oil spills in high-moor peatlands.     

Role of cation exchange in preventing the decay of anoxic deep bog peat

The major bog systems in northern areas are dominated by Sphagnum species, the partially decomposed remains of which form the bulk of deep peat. By adding mono- and di-valent cations to deep peat cores (2.0-2.5 m) and measuring CH₄ and CO₂ concentrations in the manipulated peat cores using quadrupole mass spectrometry (QMS) we demonstrate that the lack of availability to microorganisms of essential cations is limiting decay in deep peat. The cations with the highest binding strength displaced the most cations and stimulated decay. Decay in deep peat cores was also stimulated by a C source (acetate), but not by NH₄⁺. The addition of cations and acetate resulted in a less than additive stimulation of decay. The stimulatory effect of acetate and copper decreased in the presence of ammonium. The addition of EDTA to surface bog peat (where cations are conserved) decreased decay rates in surface peat (0.0-0.5 m) to that of the untreated deep peat (2.0-2.5 m). Deep peat was unaffected by treatment with EDTA. The effect of adding Cu²⁺differed with the depth from which the peat was collected. Cu²⁺ did not stimulate decay in surface bog peat (0.0-1.5 m) but stimulated decay in peat from 1.5-3.5 m. Below 3.5 m to the bottom of the profile (5.0 m) no positive effect was observed. By comparing deep peat with surface peat we have shown that cation limitation because of high cation exchange capacity is specific to the main mass of deep bog peat and may explain differences in decay rates between anoxic surface peat and deep peat.     

Humic-rich peat extracts inhibit sulfate reduction, methanogenesis, and anaerobic respiration but not acetogenesis in peat soils of a temperate bog

To understand why anaerobic ombrotrophic peats can be very low in methane after drainage related afforestation, we analyzed the competition of sulfate reducing, humus reducing, and methanogenic microorganisms by incubating ombrotrophic peats of the Mer Bleue bog, Ontario. Sulfate, sulfide, and sulfate containing peat dissolved organic matter (DOM) from an afforested site were added in reduced and oxidized redox state. Sulfate and acetate concentrations were analyzed, bacterial sulfate reduction (BSR) and CO₂ and CH₄ production quantified, and results analyzed by ANOVA. DOM was characterized by Fourier transformed infrared and fluorescence spectroscopy and analyzed for trace elements. CH₄ production (116 nmol cm⁻³ d⁻¹) and BSR rate (102 nmol cm⁻³ d⁻¹) were similar in ‘controls’. BSR in treatments ‘sulfate’ (73 nmol cm⁻³ d⁻¹) and ‘sulfide’ (118 nmol cm⁻³ d⁻¹) did not significantly differ from ‘controls’ but addition of DOM significantly diminished BSR down to 0.4 nmol cm⁻³ d⁻¹ (Kruskal Wallis test, p < 0.05). CH₄ production decreased with sulfate (16%, not significant) and sulfide addition (40%, p < 0.05) and CO₂ production increased (treatment ‘sulfate’, p < 0.05). Addition of all DOM extracts (67 mg L⁻¹) almost completely suppressed methanogenesis and CO₂ production (p < 0.05), but acetate accumulated compared to the control (p < 0.05). The DOM applied contained carboxylic, aromatic and phenolic moieties and metal contents typical for peat humic substances. We conclude that a toxic effect of the intensely humified DOM occurred on both methanogenic and sulfate reducing bacteria (SRB) but not on fermenting microorganisms. As yet it is not clear what might cause such a toxic effect of DOM on SRB and archaea.     

Controls on latent heat flux and energy partitioning at a peat bog in eastern Canada

Surface and atmospheric controls on latent heat flux (Q_E) and energy partitioning were assessed during three growing seasons at the Mer Bleue peat bog. The surface consisted of a sparse canopy (maximum leaf area index 1.3) of low, mostly evergreen shrubs over moss-covered hummocks and hollows. Available energy was partitioned mostly to Q_E (Bowen ratio often less than 0.5) throughout the growing seasons over an extensive range of water table fluctuation (as much as 50 cm). Q_E was often at or below the equilibrium rate due to surface (low moss water content, strong vascular stomatal control) and/or atmospheric (low vapour pressure deficit (D_a)) factors. Turbulent energy fluxes varied with net radiation and the magnitude of the fluctuations were affected by D_a and moss water content. It is suggested that a change in source partitioning for Q_E led to a change in Q_E − D_a dynamics. Early in the growing season the moss was wet and the vascular canopy was replacing leaves, thus Q_E increased as D_a increased because moss, which reacts passively to D_a, contributed strongly to Q_E. Later in the growing season as water table declined and the evaporation load reduced moss and fibric peat water contents, moss contributed less strongly to Q_E and vascular contribution became more important. Also, stomatal control became more influential in reducing bulk surface conductance for water vapour and Q_E in response to increasing D_a.     

Strong negative geochemical anomaly of raised bog peat in the middle taiga zone, Middle Priobye

Peat samples from bogs of the middle taiga zone (Middle Priobye region) represent a strong negative geochemical anomaly of a number of chemical elements compared to peat samples from bogs of the southern taiga of the Middle and Upper Priobye regions. The proximity of mountain systems (the Altai Mountains, the Salair Ridge, and Kuznetskii Alatau) presumably affects peat composition in the southern taiga zone by air transportation of mineral dust. The latter fact enriches peat of raised bogs in certain metals, whilst not reaching the outlying Middle Priobye region.     

Changes in metabolic and structural diversity of a soil bacterial community in response to cadmium toxicity

Cadmium toxicity reduces the species diversity of soil microbial communities and their ability to metabolize different carbon substrates. However, it is not yet clear whether there is a relationship between loss of species diversity and the metabolic rates at which different substrates are used. In this research, the ability of a soil microbial community to metabolize 31 C substrates was examined using Biolog Ecoplates amended with Cd over a range of concentrations (0, 5, 10, 20, 50 g ml^–1). After 48 h growth, the bacterial communities that were produced on ten of the substrates were characterized in relation to their 16S rDNA profiles by PCR denaturing-gradient gel electrophoresis. Results showed that both the microbial growth rates and the numbers of substrates that were used were reduced with increasing Cd concentration. When examined across all substrates, approximately 30% of the 16S rDNA bands representing different bacterial species were eliminated by 5 g Cd ml^–1. However, there was considerable variation in the bacterial community responses with different C substrates. Both cluster analysis and discriminant analysis indicated that the bacterial community structures could be grouped into sensitive, moderately sensitive, and Cd-resistant communities.     

Two- and three-domain bacterial laccase-like genes are present in drained peat soils

Laccases of fungal origin have been intensively studied due to their importance in various biotechnological applications. There is a constant demand for new laccases with improved properties such as stability at higher temperatures or at an alkaline pH. Growing molecular evidence suggests that laccases may also be widespread in bacteria. While only a handful of bacterial laccases have been purified and characterized, several novel traits have already been discovered (e.g. pH-stability and 2-domain organization of the enzyme as opposed to the usual 3-domain structure of fungal laccases). The aim of this study was to examine the diversity of bacterial laccase-like genes in two types of high-organic peat soil using a cloning and sequencing approach. Gene libraries prepared of small fragments (150 base pairs) revealed an amazing diversity of bacterial laccases. The fragments clustered in 11 major lineages, and one third of the 241 sequences resembled laccase-like genes of Acidobacteria. Additionally, a new primer was used to retrieve several larger fragments of the putative bacterial laccase genes that spanned all four copper-binding sites. Both “conventional” 3-domain laccases and the recently described 2-domain small laccases have been obtained using this approach, demonstrating the potential of the primer. The present study thus contributes to the understanding of the diversity of bacterial laccases and provides a new tool for finding laccase-like sequences in bacterial strains and soil samples.     

Temporal changes in abundance and composition of ammonia-oxidizing bacterial and archaeal communities in a drained peat soil in relation to N<Subscript>2</Subscript>O emissions

Purpose  

Boreal peat soils comprise about 3% of the terrestrial environments, and when drained, they become sources of the greenhouse gas nitrous oxide (N₂O). Ammonia oxidation can result in N₂O emissions, either directly or by fuelling denitrification, but we know little about the ecology of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in peat soils. Our aim was to determine temporal alterations in abundance and composition of these communities in a drained and forested peat soil in relation to N₂O emissions and ammonia oxidation activity.     

Saturation of raised bog peat exchange sites by Pb and Al stimulates CH4 production

We examined the effect of cation treatments on methanogenic activity and nutrient release from exchange sites in raised bog and fen peats. Treatments consisted of cation chloride solutions (MgCl₂, AlCl₃ and PbCl₂) applied individually. In raised bog peat Al³⁺ and Pb²⁺ increased CH₄ production. A correlation was found between CH₄ production and the amount of micro- and macronutrient cations released by the treatments. In calcareous fen peat, such a stimulation was also found, but there was no correlation between CH₄ production and micro and macronutrient release. Direct nutrient and pH effects could not account for these observations. Thus the results support the hypothesis that the methanogenic community in the raised bog is limited by the availability of mineral nutrients and/or inactivity of exo-enzymes, both of which are bound onto exchange sites.     

Changes in Carbon following Forest Soil Transplants along an Altitudinal Gradient

Using a simple case study approach, this research tested the hypothesis that soil organic carbon (C) concentrations would decline when mineral soils from cool, nitrogen (N)–rich, high‐elevation (>1400 m) forests were transplanted to warmer, N‐poor, low‐elevation (～545 m) forests. Two short‐term (<5 year) experiments were performed in the Great Smoky Mountains National Park (Tenn./N.C.) in the southern Appalachian Mountains. In the first experiment, C concentrations in whole soils, particulate organic matter (POM), and mineral‐associated organic matter (MOM) declined significantly (P 0.001) when soils from a high elevation site (1H) were transplanted to a low‐elevation site (1L). In the second experiment, there was a significant (P  0.05) decline in POM C concentrations when high elevation soils (2H) were moved to a lower elevation (2L) as well as declines in whole soil C concentrations that were significant at P  0.10. In both cases, reciprocal transplants of low elevation soils to high elevations resulted in no detectable change in soil C concentrations. Warming of higher quality soil organic matter (whole soil C‐to‐N ratio <20) resulted in greater soil C loss. Consistent with prior predictions, the results suggest that a future warmer and drier climate may cause losses of forest soil C at high elevations in the southern Appalachian Mountains.     

The influence of the bog water level on the transformation of sphagnum mosses in peat soils of oligotrophic bogs

Quantitative estimates of the rate of transformation of moss residues of two species (Sphagnum angustifolium and Sphagnum fuscum) in the peat soils (Histosols) were obtained for two oligotrophic bogs with different hydrological conditions in the southern taiga of Western Siberia. The coefficients of decomposition rate (k) significantly differed for the studied species; the decomposition of Sphagnum fuscum proceeded much slower. The most intense decomposition was observed in the first year of transformation (k = 0.06 and 0.16–0.66 for Sph. fuscum and Sph. angustifolium, respectively); then, the rate of moss decomposition decreased. Despite the great amount of fungal mass in the moss residues (exceeding the bacterial biomass by 3–10 times), the rate of the initial decomposition was very low. The hydrological conditions affected the intensity of this process—in the peat of the Kirsanovskoe bog with the low level of bog water, losses of the mass of sphagnum moss were 1.1–1.6 times greater as compared to those in the Bakcharskoe bog. For Sph. angustifolium, the level of bog water was more important than for Sphagnum fuscum, whereas for Sphagnum fuscum, the composition of organic matter played a decisive role in the rate of decomposition of moss residues. The activity of the microflora also depended on the level of bog water, which was manifested in a greater abundance of bacteria in the peat of the Kirsanovskoe bog.     

Changes in soil profile characteristics through cultivation of an upland Vertisol in Zambia

Abstract. Crops grown on virgin upland Vertisols of Zambia, are reported to perform rather poorly. However, subsoiling followed by repeated cultivation over two years apparently improves crop growth. Highest yields were recorded under long-term cultivation (12 years). To evaluate the reasons for these differences in crop response to Vertisol management, physical and hydrodynamic characteristics of soil profiles were studied in three soil management systems. The management systems were: uncultivated or virgin land; land cultivated for two years; and land cultivated for 12 years. The mean soil aggregate size decreased with increased time of cultivation, mostly due to the decrease of the largest sized aggregates. The surface horizon dried more slowly on the long-term cultivation plot. A comparison of the hydraulic conductivities indicated that water intake in the deeper layers improved with increased period in cultivation. Oxygen diffusion measurements showed good aeration at field capacity, to a depth of 0.32m on the long-term cultivation plots, but only to 0.17 m and 0.25 m for 2 years cultivation and virgin plots respectively. Repeated cultivation was beneficial in improving surface soil tilth and in improving subsurface drainage, thus removing the problem of a perched water table which occurred close to the soil surface under natural conditions.     

Avian assemblages along a gradient of urbanization in a highly fragmented landscape

Our goal was to evaluate how avian assemblages varied along a gradient of urbanization in the highly fragmented landscape of coastal southern California. We measured species richness and abundance of birds within continuous blocks of habitat, within urban habitat fragments that varied in landscape and local habitat variables, and within the urban matrix at different distances from the wildland interface. These comparisons allowed us to characterize patterns of avifaunal response to a gradient of urban fragmentation. At the fragment scale, we found that fragment area was a strong, positive predictor of the total number of breeding species detected per fragment; total bird abundance per point count also increased with fragment size. Tree cover was higher in small fragments, as was the abundance of birds that typically occupy wooded habitats. Comparisons between core, fragment, and urban transects revealed differing patterns of response of individual bird species to urbanization. In unfragmented habitat, we recorded a relatively high diversity of urbanization-sensitive birds. In urban transects, these species were rare, and a relatively few species of non-native and anthropophilic birds were common. These urbanization-enhanced birds were also recorded in previous urban gradient studies in northern California and Ohio. Bird communities along the urban gradient reached their highest richness and abundance in fragments. The marked difference in vegetation structure between urban and natural landscapes in this arid shrubland system likely contributed to this pattern; the presence of native shrubs and exotic trees in fragments enabled both shrub and arboreal nesters to co-occur. As is characteristic of biotic homogenization, urban fragmentation in coastal southern California may increase local diversity but decrease overall regional avifaunal diversity.