Subsidence rates and carbon loss in peat soils following conversion to pasture in the Waikato Region, New Zealand

Abstract. Drainage of peat soils for agriculture can lead to large carbon losses due to oxidation of peat. We estimated peat subsidence rates and total carbon losses, due to 40 years of dairy farming on a former peat bog, by measuring the thickness of peat and total carbon of farmland and of an adjacent unmodified peat bog above a marker tephra layer that was deposited about 200 AD. Subsidence rates averaged 3.4 cm yr^–1 (95% confidence interval of 3.2 to 3.5 cm yr^–1) and carbon loss averaged 3.7 t ha^–1 yr^–1 (95% confidence interval of 2.5 to 5.0 t ha^–1 yr^–1). On average, 63% of the subsidence was due to consolidation, with the remainder (37%) attributed to losses of organic matter due to peat mineralization.     

Decomposition activity of peat soils in geogenous mires in Sasakami, central Japan

Decomposition rates of peat and cellulose, and oxygen consumption rates were studied in three minerotrophic peat mires in Sasakami, central Japan. These mires had differences in topography, pedology and hydrology. Two dominant vegetation types in each mire, a Sphagnum palustre–S. cuspidatum community and a Rhynchospora fauriei community, were selected as the decomposition study sites. The objective of this study was to examine how the environmental and vegetational differences in mires correlate with the activity of decomposition. Decomposition rates of peat and the rates of cellulolysis were studied in the field for 6 months. Oxygen consumption rates were measured in the field using a closed chamber equipped with an oxygen electrode. In situ peat decomposition rates showed significant differences among the three mires, whereas in situ cellulolysis rates showed significant differences between communities. Peat mass loss rates positively correlated with the nitrogen and carbon concentration of the peat. Cellulolysis rates positively correlated with the range of water table fluctuation. Oxygen consumption rates showed significant negative correlation with the averaged and minimum water table depth, and positive correlation with the range of water table fluctuation. There was a significant positive correlation between cellulolysis rates and oxygen consumption rates. These are useful parameters for evaluating how the decomposition activity in soil depends on the vegetation types and water conditions.     

Effect of nutrient compositions in peat hydrolysate on protein and biomass yields of Candida tropicalis

Summary Research was conducted to study the effect of nutrient compositions, at different levels, added in peat hydrolysates on biomass yields and protein of Candida tropicalis. Samples of Minnesota sphagnum peat were hydrolyzed by boiling at 100°C with 1-1 H₂SO₄ solutions to produce peat hydrolysates which can support the growth of yeast. Peat hydrolysates were adjusted to pH 5.5 and mixed with mineral nutrients (NH₄NO₃, NaH₂PO₄ + Na₂HPO₄, KCl, and MgSO₄) and glucose. Among the single nutrients tested, glucose produced the most significant enhancement of biomass yields, followed by NH₄NO₃, NaH₂PO₄ + Na₂HPO₄, KCl, and MgSO₄. NH₄NO₃ was found to be the most important single nutrient affecting protein accumulation in yeast cells, followed by glucose > NaH₂PO₄ + Na₂HPO₄ > KCl > MgSO₄. However, protein and biomass production was significantly (P 0.05) greater for combined nutrients than for any single-nutrient enrichment. The level of residual reducing sugars in peat hydrolysate was inversely proportional to cell counts and optical densities. Addition of high concentrations of nutrients delayed the time of reaching to stationary phase in optical density, cell counts, and pH of yeast cultures. In general, as nutrients were increased, significant (P 0.05) increases in productivity and cell density were observed. However, specific growth rate decreased with increasing nutrient concentrations. It was concluded that nutrient amendments containing supplementary sources of C/N/P/K/S = 400:36:3.3:3.8:1 are most suitable for biomass production and the biosynthesis of protein by C. tropicalis.     

Influence of water table level and soil properties on emissions of greenhouse gases from cultivated peat soil

A lysimeter method using undisturbed soil columns was used to investigate the effect of water table depth and soil properties on soil organic matter decomposition and greenhouse gas (GHG) emissions from cultivated peat soils. The study was carried out using cultivated organic soils from two locations in Sweden: Örke, a typical cultivated fen peat with low pH and high organic matter content and Majnegården, a more uncommon fen peat type with high pH and low organic matter content. Even though carbon and nitrogen contents differ greatly between the sites, carbon and nitrogen density are quite similar. A drilling method with minimal soil disturbance was used to collect 12 undisturbed soil monoliths (50 cm high, Ø29.5 cm) per site. They were sown with ryegrass (Lolium perenne) after the original vegetation was removed. The lysimeter design allowed the introduction of water at depth so as to maintain a constant water table at either 40 cm or 80 cm below the soil surface. CO₂, CH₄ and N₂O emissions from the lysimeters were measured weekly and complemented with incubation experiments with small undisturbed soil cores subjected to different tensions (5, 40, 80 and 600 cm water column). CO₂ emissions were greater from the treatment with the high water table level (40 cm) compared with the low level (80 cm). N₂O emissions peaked in springtime and CH₄ emissions were very low or negative. Estimated GHG emissions during one year were between 2.70 and 3.55 kg CO₂ equivalents m⁻². The results from the incubation experiment were in agreement with emissions results from the lysimeter experiments. We attribute the observed differences in GHG emissions between the soils to the contrasting dry matter liability and soil physical properties. The properties of the different soil layers will determine the effect of water table regulation. Lowering the water table without exposing new layers with easily decomposable material would have a limited effect on emission rates.     

Short- and long-term effects of nutrient enrichment on microbial exoenzyme activity in mangrove peat

Mangroves receive increasing quantities of nutrients as a result of coastal development, which could lead to significant changes in carbon sequestration and soil subsidence. We hypothesised that mangrove-produced tannins induce a nitrogen (N) limitation on microbial decomposition even when plant growth is limited by phosphorus (P). As a result, increased N influx would lead to a net loss of sequestered carbon negating the ability to compensate for sea level rise in P-limited mangroves. To examine this, we quantified the short- and long-term effects of N and P enrichment on microbial biomass and decomposition-related enzyme activities in a Rhizophora mangle-dominated mangrove, which had been subjected to fertilisation treatments for a period of fifteen years. We compared microbial biomass, elemental stoichiometry and potential enzyme activity in dwarf and fringe-type R. mangle-dominated sites, where primary production is limited by P or N depending on the proximity to open water. Even in P-limited mangroves, microbial activity was N-limited as indicated by stoichiometry and an increase in enzymic activity upon N amendment. Nevertheless, microbial biomass increased upon field additions of P, indicating that the carbon supply played even a larger role. Furthermore, we found that P amendment suppressed phenol oxidase activity, while N amendment did not. The possible differential nutrient limitations of microbial decomposers versus primary producers implies that the direction of the effect of eutrophication on carbon sequestration is nutrient-specific. In addition, this study shows that phenol oxidase activities in this system decrease through P, possibly strengthening the enzymic latch effect of mangrove tannins. Furthermore, it is argued that the often used division between N-harvesting, P-harvesting, and carbon-harvesting exoenzymes needs to be reconsidered.     

Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia

A survey of the density and population size of Bornean orang-utan (Pongo pygmaeus) was carried out in 1995 and 1996 in an area of peat swamp forest in the Sungai (River) Sebangau catchment, Central Kalimantan, Indonesia. Densities were calculated for four forest sub-types by counts of orang-utan sleeping platforms (nests) along line transects. Densities were found to be highest in the tall interior and mixed swamp forest sub-types. Low pole forest supported the lowest density. Habitat disturbance caused by logging was shown to affect orang-utan density within mixed swamp forest. The orang-utan population for a larger peat covered landscape unit (9200 km²), including the Sebangau catchment, was estimated to be between 5671 (±955) and 8951 (±1509) individuals, based upon the area of each forest type, the level of disturbance in each area and corrected to prevent overestimates. This study identifies the presence of a very large, self-sustaining orang-utan population in this region and emphasises the urgent requirement for greater protection of Kalimantan's peat swamp forests in the light of recent and rapid habitat degradation.     

恶唑菌酮土壤降解影响因子研究

探讨了土壤环境中的主要因素:土壤微生物、温度、含水量、pH值以及施用有机肥对恶唑菌酮降解的影响。结果表明:土壤微生物对恶唑菌酮在土壤中的降解起着重要作用,相同条件下灭菌土壤的降解半衰期是非灭菌土壤的27.6倍。环境温度、土壤含水量等对恶唑菌酮降解也有影响,在15℃～40℃的试验条件下,随着温度升高,恶唑菌酮的降解速率加快,特别是15℃～25℃温度范围内降解速率上升较快;过高和过低的土壤含水量都不利于土壤中恶唑菌酮的降解,土壤含水量为50?～100?时适宜恶唑菌酮的降解;此外施用有机肥会加速恶唑菌酮的降解;而土壤pH值对降解的影响不显著。     

Bimembrane diffusion probe for continuous recording of dissolved and entrapped bubble gas concentrations in peat

Peatlands are significant sources of the important greenhouse gas CH₄ and generally known as sinks for atmospheric CO₂ through peat accumulation. Accurate measurements of the subsurface concentrations of these gases are of pivotal importance for experimental studies improving our understanding of the dynamics and controls on the exchanges of these gases between peat soils and the atmosphere. In this paper we first briefly outline examples of different probe-based techniques for the determination of subsurface gas concentrations and thereafter we document the development and testing of two different membrane probe systems. Finally we discuss a few applications of the probes and show some results obtained by testing them in the laboratory.     

Presence and dispersal of infective Frankia in peat and meadow soils in Sweden

Summary Use of the N₂-fixing grey alder, Alnus incana (L.) Moench, as a short-rotation crop for energy production is currently being explored. To evaluate the need for inoculation of alders, the distribution of infective propagules of Frankia in the soil at potential sites for alder plantations was examined. Uninoculated grey alder seedlings were grown in three types of soil. Frequent nodulation was found in a meadow soil which had been free from actinorhizal plants for nearly 60 years, but the alder seedlings failed to nodulate in peat soil from two different bog sites. One of these bogs had been exploited for peat and the surface layer of the peat had been removed, so that the soil samples were taken from deep layers of the peat. At the other site, an area of cultivated peat, there were no infective propagules of Frankia in plots without alders; the infective Frankia was present in plots only where it had been introduced by inoculated alders. There was no detectable air-borne dispersal of Frankia. Instead, water movement might account for the dispersal of Frankia in peat. Although the apparent absence of Frankia in these peat soils necessitates inoculation of alder seedlings before planting out, this makes it possible to introduce and maintain Frankia strains with selected beneficial characteristics, since there is no competition from an indigenous Frankia flora.     

Substrate utilisation profiles of microbial communities in peat are depth dependent and correlate with whole soil FTIR profiles

A multiple substrate induced respiration (SIR) assay, using ¹⁴C-labelled carbon sources, was used to evaluate community level physiological profiles (CLPP) of the microbial community in peat horizons of differing degrees of humification. The separation and grouping of the peat horizons by CLPP was similar to the pattern produced by analysis of the organic carbon chemistry of the peat horizons by Fourier Transform Infrared (FTIR) spectroscopy and therefore reflected the level of decomposition. Partial redundancy analysis showed that a large proportion (68.7%) of the variability in the CLPP data could be attributed to the ratio of polysaccharide to ‘carboxylate’ FTIR bands alone. The multiple substrate SIR technique may, therefore, be a powerful technique to further elucidate the influence of the microbial constituent of peat on the potential activity and patterns of cycling of labile carbon in peatlands.     

Iron and manganese effect on soil chemical properties,yield components,and nutritional status of soybean

In plants, iron (Fe) and manganese (Mn) have many functions, as the transport and electron transference during photosynthesis, and their deficiencies affect the chlorophyll formation, plant growth and grain yield (GY). We carried out two experiments under greenhouse conditions with the aim of determining the influence of Fe and Mn on nutritional status, physiological components, soil chemical properties and yield components of soybean plants. In both experiments, five Fe and Mn rates were used. The GY, shoot dry weight yield (SDWY), the number of grain per pot (NGP), photosynthesis rate (A) and chlorophyll content were influenced by Fe rates, while GY, SDWY, root length and A were influenced by Mn rates. Iron and Mn concentrations in leaves and grains increased with rates of Fe and nutrients. The Mehlich 1 and DTPA-TEA extractants were efficient to determine the Fe and Mn available in the soil.     

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.     

historical deposition rates of Cd,Cu, Pb,and Zn in Norway and Sweden estimated by 210Pb dating and measurement of trace elements in cores of peat bogs

From six ombrotrophic mires located far from distinct local sources in Sweden and Norway, a core was sampled in bog hummocks in 1988 and dated by 210_Pb. Ten slices from each core were analyzed for Cd, Cu, Pb, and Zn. Based on the datings, the accumulation rates of Cd, Cu, Pb, and Zn have been estimated for the last 150 years. A reasonable agreement exists in the comparison between the recent deposition in the peat bog and nearby bulk deposition measurements. Highest deposition has been measured in southern Norway and the western part of Sweden. Generally, deposition has increased during the last 150 years, except at a station on the east coast of Sweden. In a study in Sweden where heavy metals have been measured in mosses every five years time since 1970, significant decreases in the concentrations of heavy metals have been found. Similar decreases have not been measured in the present study, although both methods are expected to reflect atmospheric deposition. Several studies have indicated that peat bogs are not suitable for measuring the historical evolution of trace metals. However, despite the disagreement, the recent literature suggests that it can be done with reasonable accuracy when performed with samples from hummocks in the peat bog.     

Implications of soil substrate and land use for properties of fen soils in North-East Germany Part III: Soil quality for grassland use

Abstract

The aim of the study was to analyse aspects of fen soil quality for grassland use with regard to the different topsoil structure and their status of earthification/moorshification (degradation). Fifty fens of different origin, structural status and land use intensity were sampled, analysed and scored by different methods: Visual Soil Assessment, Peerlkamp test and Muencheberg Soil Quality Rating. Suitable soil structure scores were found at different land use intensities with the exception of stock tracks on pastures. These had lower water and air permeability and lower soil strength. Highest visual scores of macrostructure were found where the water table was deeper; while highest overall soil quality scores occurred where the water table was optimum. The accelerated status of moorshification had no effect on the soil quality scores and on the crop yield. At lower levels of soil development (earthification) the crop yield was slightly lower due to higher proportions of inedible plants. It may be concluded that degraded peat soils will have no loss of soil quality and have relatively high soil quality for grassland use if the water table can be managed in a suitable range and the sward quality is maintained.     

Influence of earthworms on soil properties and grass production in reclaimed cutover peat

The effects of earthworms on grass growth and soil structure in reclaimed peat were studied in a glasshouse bucket experiment. Cumulative grass yields from 13 cuts taken over a period of 20 months were 89% higher in organically fertilized and 19% higher in inorganically fertilized buckets with earthworms than in similarly fertilized buckets without earthworms. When fertilizers were withheld from some buckets after 7 months grass growth during the remainder of the study was significantly greater in the presence of earthworms under both organic (+222%) and inorganic (+114%) regimes. It is considered that grass growth responses were mainly due to enhanced organic matter decomposition and mineralization. Soil subsidence rates, hydraulic conductivity, moisture characteristics, bulk density, porosity, fibrosity, and soil morphology and micromorphology were significantly influenced by earthworm activity. The results show that earthworm activity can significantly accelerate the process of maturation and profile development in reclaimed peat soils. Received: 12 February 1996     

Influences of continuous grazing and livestock exclusion on soil properties in a degraded sandy grassland, Inner Mongolia, northern China

Overgrazing is one of the main causes of desertification in the semiarid Horqin sandy grassland of northern China. Excluding grazing livestock is considered as an alternative to restore vegetation in degraded sandy grassland in this region. However, few data are available concerning the impacts of continuous grazing and livestock exclusion on soil properties. In this paper, characteristics of vegetation and soil properties under continuous grazing and exclusion of livestock for 5 and 10 years were examined in representative degraded sandy grassland. Continuous grazing resulted in a considerable decrease in ground cover, which accelerates soil erosion by wind, leading to a further coarseness in surface soil, loss of soil organic C and N, and a decrease in soil biological properties. The grassland under continuous grazing is in the stage of very strong degradation. Excluding livestock grazing enhances vegetation recovery, litter accumulation, and development of annual and perennial grasses. Soil organic C and total N concentrations, soil biological properties including some enzyme activities and basal soil respiration improved following 10-year exclusion of livestock, suggesting that degradation of the grassland is being reversed. The results suggest that excluding grazing livestock on the desertified sandy grassland in the erosion-prone Horqin region has a great potential to restore soil fertility, sequester soil organic carbon and improve biological activity. Soil restoration is a slow process although the vegetation can recover rapidly after removal of livestock. A viable option for sandy grassland management should be to adopt proper exclosure in a rotation grazing system in the initial stage of grassland degradation.     

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.     

Soil chronosequence and biosequence on old lake sediments of the Burdur Lake in Turkey

The Burdur Lake is located in the southwest of Turkey, and its area has decreased by 40% from 211 km² in 1975 to 126 km² in 2019. In this study, we investigated how the soil has changed in the lacustrine material. Three soil profiles were sampled from the former lakebed (chronosequence profiles: P1, 2007; P2, 1994; and P3, 1975), and three soil profiles under different land use types (biosequence profiles: P4, native forest vegetation; P5, agriculture; and P6, lakebed) were sampled. The chronosequence and biosequence soil profiles represented various distances from the Burdur Lake and showed different stages of lacustrine evolution. Soil electrical conductivity (EC; 18.1 to 0.4 dS m_-1), exchangeable Na⁺ (34.7 to 1.4 cmol kg^-1) and K⁺ (0.61 to 0.56 cmol kg^-1), and water-soluble Cl^- (70.3 to 2.1 cmol L^-1) and SO₄^2- (275.9 to 25.0 cmol L^-1) decreased with increasing distance from the Burdur Lake, whereas the A horizon thickness (10 to 48 cm), structure formation (0 to 48 cm), gleization-oxidation depth (0 to 79 cm), and montmorillonite and organic matter (OM; 25.9 to 46.0 g kg^-1) contents increased in the chronosequence soil profiles. The formation of P3 in the chronosequence and P5 in the biosequence soil profiles increased due to longer exposure to pedogenic processes (time, land use, vegetation, etc.). Changes in EC, exchangeable cation (Na⁺ and K⁺) and water-soluble anion (Cl^- and SO₄^2-) concentrations of the salt-enriched horizon, OM, gleization-oxidation depth, A horizon thickness, and structure formation of the chronosequence and biosequence soil profiles (especially the topsoil horizon) were highly related to the distance from the Burdur Lake, time, and land use.     

Pathways of chemical recovery in acidified,metal-contaminated lakes near Sudbury,Ontario, Canada

This paper describes the recovery pathways of two lakes situated near the Coniston nickel-copper smelter. These lakes were exposed to very intense airborne pollution, including SO₂, H₂SO₄, Ni and Cu, during the 60 year operation of the smelter. After the closure of the Coniston smelter in 1972 and the subsequent improvement in air quality, the water quality in both lakes began to improve. Despite their proximity and exposure to similar inputs, the lakes differed both in the rate and magnitude of recovery. This study demonstrates the capacity of lakes to recover from chemical stresses over a very short period. Changes in Cu and Ni concentration could be predicted, while changes in pH, measured as H⁺, could not. The reasons for this discrepancy as well as the processes and lake parameters that control chemical recovery are discussed.