Seasonal variation in rates of methane production from peat of various botanical origins: effects of temperature and substrate quality

The methane produced in peat soils can vary over the growing season due to variations in the supply of available substrate, the activity of the microbial community or changes in temperature. Our aim was to study how these factors regulate the methane production over the season from five different peat types of different botanical origin. Peat samples were collected on seven occasions between June and September. After each sampling, the peat soils were incubated at five different temperatures (7, 10, 15, 20 and 25 degrees C) without added substrate, or at 20 degrees C with added substrate (glucose, or H(2)/CO(2), or starch). Rates of methane production averaged over the season differed significantly (P<0.05, R(2)=0.76) among the five peat types, the minerotrophic lawn producing the highest rates, and the hummock peat producing the lowest. The seasonal average Q(10) values for each plant community varied between 4.6 and 9.2, the highest value being associated with the ombrotrophic lawn and the lowest value with the mud-bottom plant community. For the unamended peat samples, the rates of methane production from each plant community varied significantly (P<0.05) over the season. This implies that the quality of organic matter, in combination with changes in temperature, explains the seasonal variation in methane production. However, addition of saturating amounts of glucose, H(2)/CO(2) or starch at 20 degrees C significantly reduced the seasonal variation (P<0.05) in methane production in peat from the minerotrophic lawn, wet carpet and mud-bottom plant communities. This suggests that substrate supply (e.g. root exudates) for the micro-organisms also varied over the season at these sites. Seasonal variation in methane production rates was apparent in peat from the hummock and ombrotrophic lawn plant communities even after addition of substrates, suggesting that the active biomass of the anaerobic microbial populations at these sites was regulated by other factors than the ones studied.     

Sulfate deposition and temperature controls on methane emission and sulfur forms in peat

Natural wetlands are the single most important contributors of methane (CH₄) to the atmosphere. Recent research has shown that the deposition of sulfate (SO ₄ ^2– ) can substantially reduce the emission of this radiatively important gas from wetlands. However, the influence of temperature in regulating the extent of this effect is unclear. Peatlands also constitute an important store of sulfur (S), so understanding the effect of S deposition on S dynamics within this store is important if we are to understand the interaction. The effect of enhanced SO ₄ ^2– deposition on CH₄ fluxes and S pools were investigated in peatland monoliths under controlled environment conditions. This enabled a close examination of effects at the onset of experimentally enhanced SO ₄ ^2– deposition while examining temperature effects on the interaction. Experimentally enhanced S deposition at rates as small as 15 kg SO ₄ ^2– -S ha^–1 year^–1 suppressed CH₄ emissions by 30%. There was no increased suppression at larger deposition rates of simulated acid rain. Temperature affected the suppressive effect of the simulated acid rain. At low temperatures (down to 5 °C), there was a greater proportional suppression than at higher temperatures (up to 20 °C). Evidence suggests that populations of SO ₄ ^2– -reducing bacteria do not respond, as previously thought, to enhanced SO ₄ ^2– supply with a boom followed by a bust and less recalcitrant S pools (SO ₄ ^2– and S°) were depleted in the SO ₄ ^2– -treated peat, indicating enhanced S turnover. A significant proportion of the SO ₄ ^2– from the treatment was taken up and stored as SO ₄ ^2– in vascular plants, placing this mechanism as a potentially important seasonal regulator of peatland SO ₄ ^2– availability.     

Direct mass spectrometric measurement of gases in peat cores

Abstract Dissolved gas concentrations (O₂, CH₄, CO₂) in peat cores were monitored simultaneously using a fine (1.56 mm diameter) membrane inlet probe connected to a quadrupole mass spectrometer. This technique allows direct measurements at specific locations within the sample with minimal disturbance. Detailed gas profiles in completely waterlogged peat samples (hollows) and samples in which the water table was several cm below the vegetation surface (hummocks) were compared. The depth of the water table played a central role in the distribution of gases. In a hollow, oxygen was present (90 μM) at the surface but was not detectable (<0.5 μM) at depths greater than 2 cm. Concentrations of CH₄ and CO₂ increased from 6 and 300 μM respectively at the surface to maxima of 450 and 3900 μM at 13 cm depth. At a hummock, O₂ and CO₂ were present above the water table but CH₄ was not detectable. CH₄ was measurable 2 cm below the water table. Both CH₄ and CO₂ concentrations increased with depth but maxima were not attained in the sampled cores.     

Nutrient limitation in species‐rich Calthion grasslands in relation to opportunities for restoration in a peat meadow landscape

Questions: Which nutrient(s) limit(s) vegetation productivity in Calthion grasslands? Is phosphorus release a bottleneck for restoration of species‐rich Calthion grasslands on rewetted dairy meadows? Location: Three species‐rich Calthion grasslands in the Western Peat District in the Netherlands. Methods: We conducted a field fertilization experiment with nitrogen (N), phosphorus (P) and potassium (K) in three existing Calthion grasslands to evaluate the potential for restoration on rewetted dairy meadows. Responses of above‐ground biomass, tissue nutrient concentrations and nutrient ratios were determined after 2 yr of fertilization. Results: Biomass increased with fertilization with N‐only and K‐only but did not react to P‐only additions. Comparisons of tissue nutrient concentrations and nutrient ratios also gave indications of N and K limitation. Conclusions: The strong P release expected after rewetting should not necessarily interfere with restoration of Calthion communities on rewetted dairy meadows. It is concluded that for successful restoration management measures should focus on reducing N and/or K availability. Potassium might be an overlooked bottleneck in the restoration of species‐rich grasslands.     

水位提升和泥炭藓繁殖体移植对泥炭地植被恢复的影响

泥炭藓繁殖体移植是影响泥炭地植被恢复的重要因素之一,不同移植方式的效果往往缺乏比较研究。选取长白山区白江河退化泥炭地为研究地,以自然生境的丘间种喙叶泥炭藓(Sphagnum flexuosum)和藓丘种中位泥炭藓(S.magellanicum)(后者耐旱能力较强)为实验材料,通过野外移植实验,研究水位提升与不同泥炭藓繁殖体移植方式对退化泥炭地植被恢复的影响。数据分析显示:水位条件显著影响了喙叶泥炭藓和中位泥炭藓的建植,随着水位上升,地表湿度增加,两种泥炭藓的盖度均呈明显的上升趋势;移植方式的变化短期内对泥炭藓的建植作用并不明显,但在移植2个月后,移植方式对喙叶泥炭藓表现出显著影响,即耐旱能力较强的中位泥炭藓置于上层时,喙叶泥炭藓盖度最高;水位和移植方式不存在交互作用,即在低水位条件下,中位泥炭藓置于上层的移植方式也未能提升泥炭藓的建植盖度。研究表明,水位提升是泥炭地植被恢复的十分有效的手段,因物种间存在对水分保持的差异,采用合理植物繁殖体移植方式,将会明显提升植被恢复的成效。     

Methane oxidation potential and preliminary analysis of methanotrophs in blanket bog peat using molecular ecology techniques

Abstract: The potential for methane oxidation was measured, and methanotroph gene sequences studied, in a peat core from the Moorhouse Nature Reserve, UK. Methane oxidation potential was observed in all depths of the peat core (down to 30 cm), and was inhibited by addition of acetylene, indicating the involvement of methane-oxidising bacteria. A peak of activity was shown in the 10–12 cm horizon, below which activity decreased with depth. Above this horizon, methane oxidation was relatively high and showed little change with depth. 16S rDNA libraries from several sections of the peat core were screened with methanotroph 16S rDNA probes designed to detect the genera Methylomonas, Methylococcus, Methylobacter and Methylosinus . Two clones, MHP14 and MHP17, hybridised strongly with the Methylosinus probe and upon complete sequencing and phylogenetic analysis were shown to group closely to the Methylosinus/Methylocystis genera of methanotrophs. However, the clones do form a distinct branch of their own, supported by BOOTSTRAP values, and may represent a novel group of acidophilic methanotrophs which have yet to be cultured.