Laboratory experiments on drought and runoff in blanket peat

Global warming might change the hydrology of upland blanket peats in Britain. We have therefore studied in laboratory experiments the impact of drought on peat from the North Pennines of the UK. Runoff was dominated by surface and near‐surface flow; flow decreased rapidly with depth and differed from one type of cover to another. Infiltration depended on the intensity of rain, and runoff responded rapidly to rain, with around 50% of rainwater emerging as overland flow. Drought changed the structure of the peat and the subsequent behaviour of the peat in response to rain. Surface runoff was reduced, infiltration increased and flow increased within the deeper peat layers. Old and new water produced from the peat during simulated storms was identified by bromide tracing; the amount of old mobile water flushed out of the top few centimetres was small and there was less from deeper peat layers. No significant difference in the old and new water mixing processes could be identified between the control plots and the drought treatment plots. Lissamine staining showed preferential bypass flow through macropores in the peat, though only in the top 5 cm. Following drought, however, macroporosity increased within the upper peat layers, and preferential flow extended deeper than in controls. Peat structure recovered somewhat after drought, but the effects of the drought were long‐lasting. If these effects extend to the field during drier summers then we can expect changes to the hydrology and associated chemistry of blanket peat catchments in the British uplands.     

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.     

The effect of blanket bog drainage on habitat condition and on sheep grazing, evidence from a Welsh upland bog

There has been increasing interest in potential benefits to be gained by restoring damaged peatlands, with the majority of funding currently being driven by the recovery of protected habitats. However, few data are available linking vegetation community declines with peatland drainage, and so the potential for recovery remains difficult to predict. Surprisingly, there is a similar paucity of research demonstrating the extent of drainage impacts on grazing conditions for livestock, despite this being a priority amongst land managers. We attempt to address these two knowledge gaps, first by investigating whether ditches in blanket bog habitat have improved or increased grazing for sheep, and second by assessing the impact of ditches on the condition of vegetation communities. At an extensively drained upland blanket bog in Wales, currently undergoing ditch blocking restoration, we collected vegetation and sheep occurrence data across five catchments and over 2 years. We present evidence that drained areas had remained relatively wet and were less preferred by sheep. Furthermore, our results show that while sheep preferred graminoid-rich areas, drainage did not increase the abundance of this species group. Drainage at the site has, however, resulted in some degradation in blanket bog vegetation adjacent to ditches; although at the landscape scale, historic high grazing levels appear to explain much of the current poor ecological condition of the site. We conclude that drain-blocking restoration should not reduce sheep grazing conditions beyond their current relatively poor state, and thus in this respect may not represent a threat to hill farming productivity.     

Temporal variation in the surface-water chemistry of a blanket bog on Dartmoor, southwest England: analysis of 5 years' data

Blanket‐bog peats, mapped as the Winter Hill and Crowdy associations by the Soil Survey of England and Wales, are an oceanic manifestation of the ombrotrophic ‘raised‐bog’ (Hochmoor) peats that cover large tracts in the boreal zone of the northern hemisphere. This paper examines monthly analyses from 1992 to 1997 of major ions and other variables from an upland blanket bog in southwest England in relation to seasonality, rainfall, and the chemical composition of rainwater. Average ionic composition of surface water (and peat) integrates variable atmospheric solute inputs over the years. The dominant ions in the surface water, Na⁺ and Cl^–, showed only weak seasonality, but divalent cations a stronger seasonal pattern with a summer maximum. Mean pH ranged from c. 4.4 in February to c. 4.2 in August. Changes in concentration of different cations were closely interlinked by cation exchange. The anion deficit, accounted for by anionic groups on the dissolved organic matter, was strongly seasonal with a summer maximum, as was optical absorbance at 320 nm. Nitrate and NH₄⁺ were both at much smaller concentrations than in rain. Nitrate exceeded 1 μmol l^?1 only during cold periods in winter, mainly following drought in the summer of 1995; NH₄⁺ reached a few μmol l^?1 only in summer. There was evidence of net retention of S by the peat in wet sites and during wet periods, and of net release of SO₄^2– (and acidity) under dry conditions. The 1995 summer drought and ensuing dry year in 1996 had marked and persistent effects on pH, apparent ion deficit (DEF), SO₄^2–, the divalent cations and Fe.     

Rapid beetle community convergence following experimental habitat restoration in a mined peat bog

The rate of recovery of invertebrate communities following habitat restoration has received little attention, despite the importance of invertebrates in ecosystem dynamics. In experimental trials in a mined peat bog in New Zealand, we compared the short-term rate of beetle community re-assembly at sites restored using management techniques varying in cost and effort to implement, and subsequently examined the long-term rate of beetle community convergence towards the ‘target’ community structure of an undisturbed peat bog. There was a direct relationship between the rate of beetle community re-assembly and the cost and effort applied to plant community restoration treatments (processed peat with no seed, processed peat with seed, and direct habitat translocation). To test the longer term rate of beetle community convergence following habitat restoration, we monitored beetle assemblages on a chronosequence of experimental habitat islands in which restoration was initiated 1, 13, 24, 25, 42 and 72 months previously. With increasing age, the plant community became more diverse and structurally complex, and beetle community composition converged rapidly on the target community structure of an undisturbed peat bog. Using a simple linear regression analysis on ordination axis scores, we obtained the quantitative prediction that the beetle community on restored islands would converge on the average community composition of an undisturbed peat bog within just 7-8.5 years. Our results clearly show that rapid invertebrate community re-assembly can occur in direct response to management techniques focused on establishing vegetation structure. Even the use of a low-cost restoration technique (processed peat with seed added) was effective in initiating remarkably rapid invertebrate community re-assembly in cutover peat bogs within 10 years.     

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.     

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.     

Changes in bacterial and archaeal community assemblages along an ombrotrophic peat bog profile

Biology and Fertility of Soils - Peatlands are archives of extreme importance for the assessment of past ecological, environmental and climatic changes. The importance as natural archives is even...     

Nutrient fluxes in runoff on reseeded blanket bog, limed and fertilized with urea, phosphorus and potassium

Abstract. Studies have been made of the effects of 15 g N/m² as urea in two dressings during April and June on annual nutrient fluxes in runoff from reseeded blanket bog also receiving annually 6 g P/m² as granular superphosphate and 6 kg K/m² as potassium chloride. Urea applications increased significantly ( P < 0.05) the mean annual ammonium-N flux from 17 mg/m² for the P + K plots to 245 mg/m² for the N + P + K plots. Annual fluxes of total P, K and Ca were also increased ( P < 0.05) by the addition of urea. This was attributed to the effects of increased acidity around grass roots following N uptake as ammonium-N. In contrast, nitrate-N was removed from rainwater throughout the year and concentrations in runoff were at the limit of detection (< 0.01 mg/1) on many occasions. Concentrations of organic-N in runoff exceeded those of ammonium-N, but were not significantly changed by fertilization.     

Spatial patterns of top soil carbon sensitivity to climate variables in northern Chinese grasslands

Abstract

Estimation of the sensitivity for soil organic carbon to climate change is critical for evaluating the potential response of the terrestrial biosphere to global change. In this study, we integrated CENTURY 4.5 model with GIS to assess the soil organic carbon sensitivity to climate variable shifting and atmospheric carbon dioxide enrichment in northern Chinese grasslands. The response of top soil (0–20 cm) organic carbon to climate change depended on the relative sensitivity of net primary productivity and soil respiration. A 4°C increase in soil temperature led to a loss of 4.7% of soil organic carbon in the Alpine Meadow region, but the same temperature increase led to a maximum loss of only 2.3% of soil organic carbon in the Temperate Steppe region. The effects of precipitation changes on soil organic carbon were varied depending on the moisture level of the local grassland system. The direct effect of carbon dioxide enrichment was to reduce carbon loss throughout northern Chinese grasslands, especially in droughty regions. Alpine Meadow was the most sensitive region under climate change, and it will become the biggest potential carbon source in Chinese grasslands as climate warming continues to occur. Increased atmospheric carbon dioxide concentrations led to net carbon sequestration in all grasslands and tended to diminish the carbon loss driven by precipitation and temperature changes.     

The effects of lead shot deposition on soils and crops at a clay pigeon shooting site in northern England

Abstract. The impact of lead shot on soils and crops was examined at a clay pigeon shooting site in northern England. Topsoil cores were collected along a 300 m transect from the shooting range, and the numbers of lead shot pellets per soil core, total and 'plant-available'(0.5 m acetic acid extractable) lead concentrations, organic matter content, pH and cation exchange capacity were determined. The number of oilseed rape plants and their stem diameters were recorded in 1 m² quadrats placed at the soil sampling locations. Total and 'plant-available' lead concentrations in the soil were most but plant numbers per m² and mean stem diameters were least in the area of greatest lead shot deposition. Total lead concentrations in the soil commonly exceeded 5000 mg/kg; these are considerably greater than threshold 'trigger' concentrations proposed by the Department of the Environment, above which soils are considered to be contaminated and warrant further investigation. Concentrations of lead in the oilseed rape plants themselves were also largest in the area of most intense lead shot deposition; in root samples the lead concentration exceeded 400 mg/kg. The management and remediation of contaminated soils at the clay pigeon shooting site are discussed.     

A comparison of peat properties in intact,afforested and restored raised and blanket bogs

Recognition of peatlands as a key natural store of terrestrial carbon has led to new initiatives to protect and restore them. Some afforested bogs are being clear-felled and restored (forest-to-bog restoration) to recover pre-afforestation ecosystem function. However, little is known about differences in the peat properties between intact, afforested and restored bogs. A stratified random sampling procedure was used to take 122 peat cores from three separate microforms associated with intact (hollows; hummocks; lawns), afforested and restored bogs (furrows; original surface; ridges) at two raised and two blanket bog locations in Scotland. Common physical and chemical peat properties at eight depths were measured in the laboratory. Differences in bulk density, moisture and carbon content between the afforested (mean = 0.103 g cm⁻³, 87.8% and 50.9%, respectively), intact (mean = 0.091 g cm⁻³, 90.3% and 51.3%, respectively) and restored bogs (mean = 0.095 g cm⁻³, 89.7% and 51.1%, respectively) were small despite their statistical significance. The pH was significantly lower in the afforested (mean = 4.26) and restored bogs (mean = 4.29) than the intact bogs (mean = 4.39), whereas electrical conductivity was significantly higher (mean: afforested = 34.2, restored = 38.0, intact = 25.3 μS cm⁻¹). While significant differences were found between treatments, effect sizes were mainly small, and greater differences in pH, electrical conductivity, specific yield and hydraulic conductivity existed between the different intact bogs. Therefore, interactions between geographic location and land management need to be considered when interpreting the impacts of land-use change on peatland properties and functioning.     

Changes of the content of oil products in the oil-polluted peat soil of a high-moor bog in a field experiment with application of lime and fertilizers

A field model experiment on stimulating the activity of native oil microorganisms–decomposers was performed on an oil-polluted area in a high-moor bog under its total flooding in the northern taiga (Western Siberia). For two summer months, the doses of lime and nitrogen, phosphorus, and potassium fertilizers applied have caused a decrease in the oil products (OP) content by 54% relative to their initial amount. The decrease of the OP content in the soil profiles was nonuniform, and at the depth of 30–50 cm it was accompanied by the acidification of peat. The stimulation of the activity of aboriginal microorganisms by applying lime and mineral fertilizers led to the development of migration processes with the participation of oil and products of its transformation. These processes differed from those in the soil without application of lime and fertilizers. An original technology of applying lime and fertilizers providing minimal disturbances the upper 50-cm peat layer is suggested.     

Geochemistry and geochemical differentiation on major elements in selected peat bog profiles (south-east of Poland)

Abstract

The geochemical differentiation of major elements in various peat bog profiles from Bieszczady Mountains Region (south-east of Poland) was compared to its botanical origin. Peat cores were taken from ombrotrophic, mesotrophic, and oligotrophic peatlands, which were developed in the stream valley of the River San. Twenty-four various peat samples were analysed for peat genus, degree of peat decomposition, ash content, total nitrogen, and total carbon content of hydrolytic matter as well as content of major elements: Na, K, Mg, Ca. The results show that the botanical composition of peat deposits is no reliable indication of their trophic status. The common feature of investigated Holocene peatlands is their valley localisation on the flood terrace. The specific character of local geommorpho8ogicml and hydrological condition caused that the bottom layer of all investigated bog profiles was made of wood peats (Piceaeti, Pineti, Alneti, and Saliceti peat). The geochemical investigations of stratigraphical profiles confirm that the presented peat bogs showed specific morphological separateness comparing to other raised bogs situated in mountains or lowlands     

Carbon stocks and carbon fluxes from a 10‐year prescribed burning chronosequence on a UK blanket peat

Prescribed burning is a common land management technique in many areas of the UK uplands. However, concern has been expressed at the impact of this management practice on carbon stocks and fluxes found in the carbon‐rich peat soils that underlie many of these areas. This study measured both carbon stocks and carbon fluxes from a chronosequence of prescribed burn sites in northern England. A range of carbon parameters were measured including above ground biomass and carbon stocks; net ecosystem exchange (NEE), net ecosystem respiration (R_eco) and photosynthesis (P_g) from closed chamber methods; and particulate organic carbon (POC). Analysis of the CO₂ data showed that burning was a significant factor in measured CO₂ readings but that other factors such as month of sampling explained a greater proportion of the variation in the data. Carbon budget results showed that whereas all the plots were net sources of carbon, the most recent burn scars were smaller sources of carbon compared with the older burn scars, suggesting that burning of Calluna‐dominated landscapes leads to an ‘avoided loss’ of carbon. However, this management intervention did not lead to a transition to a carbon sink and that for carbon purposes, active peat‐forming conditions are desirable.     

Chemical and spectroscopic investigation of porewater and aqueous extracts of corresponding peat samples throughout a bog core (Jura Mountains, Switzerland)

Background, aim, and scope  

Fluorescence and UV-visible spectroscopies are simple but useful methods to characterize organic matter in the aqueous phase according to its aromatic nature and humification degree. Although there are several studies about porewater and water-extractable organic matter (WEOM) from peat, at present, no comparative investigations are available in the literature. Thus, the aim of the present study was to identify and compare chemical and spectroscopic features of porewaters and corresponding WEOM samples along a 105-cm undisturbed peat profile.     

Aeolian deposition and soil parent materials in northern Nigeria

The introduction considers the nature of the problem of “drift” soils in northern Nigeria. The physical environment of the survey area is described briefly and the percentages of silt, very fine sand and fine sand occurring in the soils are mapped. Textural belts are identified and the profile distribution frequencies within the belts are tabulated. Parent material origins are discussed and attempts are made to reconcile the apparently aeolian nature of the soil materials, in terms of the particle-size distribution pattern, with the various soil profile morphologies of today.     

Predicting pesticide emissions and downwind concentrations using correlations with estimated vapor pressures

Pesticide emissions to air have been shown to correlate with compound vapor pressure values taken from the published literature. In the present study, emissions correlations based on vapor pressures derived from chemical property estimation methods are formulated and compared with correlations based on the literature data. Comparison was made by using the two types of correlations to estimate emission rates for five herbicides, a fungicide, and an insecticide, for which field-measured emission rates from treated soil, foliage, and water were available. In addition, downwind concentrations were estimated for two herbicides, three fungicides, four insecticides, and two fumigants, for which concentration measurements had been made near treated sources. The comparison results demonstrated that correlations based on vapor pressures derived from chemical property estimation methods were essentially equivalent to correlations based on literature data. The estimation approach for vapor pressures is a viable alternative to the inherently more subjective process of selecting literature values.     

Different distribution of polycyclic aromatic hydrocarbons (PAHs) between Sphagnum and Ledum peat from an ombrotrophic bog in Northeast China

Journal of Soils and Sediments - The aims of this study are to investigate historical PAH deposition through the analysis of PAHs in bulk peat cores and reveal the different distribution of PAHs in...     

Simulating nitrate concentrations in water draining from a small arable catchment in England

Abstract. The catchment simulated comprises 57 hectares of heavy clay soil managed as six arable fields. Mole and pipe drains carry surplus water into two ditches, one feeding into the other. Their combined flow was passed through a flume with an automatic water sampler, samples from which were analysed for nitrate. Measurements of nitrate concentration made during periods of water flow from 1990 to 1993 were simulated using a model comprising sub-models for leaching, mineralization, nitrogen uptake by crops and subsoil denitrification. The simulations were plotted against the measurements. For statistical evaluation, the correlation coefficient was used to assess the degree of association between the measurements and the simulations and the mean difference to assess the agreement. The correlation between the simulations and the measurements was significant in two of the three seasons, but the mean difference was significant in all three. However, taking all three seasons together gave a very highly significant correlation and a non-significant mean difference.