长白山哈泥泥炭地两种生境苔藓与维管植物种间联结

采用2×2列联表,通过方差分析、χ²检验、Spearman秩相关和Jaccard指数对哈泥泥炭地20种优势苔藓和维管植物种间联结进行定量分析。研究结果表明,1)在开阔地,中位泥炭藓、锈色泥炭藓和桧叶金发藓3种苔藓与小叶杜鹃、鹿药、狭叶杜香的种间联结具有一致性,林缘中尖叶泥炭藓和喙叶泥炭藓与维管植物主要呈负关联;2)林缘生境物种总体呈显著正关联,开阔地中呈不显著正关联;3)2种生境下种间关联对比发现,郁闭度是影响泥炭地植被分布的重要环境因子,在同种生境下重要值大的物种之间通常出现正联系,在2种生境重要值差异大的物种之间一般表现为负联系。     

Bacterial diversity and community structure along different peat soils in boreal forest

Bacteria in peat forest soil play important role in global carbon cycling. The distribution of bacteria population in different peat soils as a whole and how forest management practices alter the bacterial populations are still poorly known. Using pyrosequencing analysis of 16S rRNA gene, we quantified the diversity and community structure of bacteria in eight peat forest soils (pristine and drained) and two mineral forest soils from Lakkasuo, Finland with either spruce-dominant or pine-dominant tree species. In total, 191,229 sequences which ranged from 15,710 to 22,730 per sample were obtained and affiliated to 13 phyla, 30 classes and 155 genera. The peat forest soils showed high bacterial diversity and species richness. The tree species seems to have more strong impact on the bacterial diversity than the type of peat soil, which drives the changes in bacterial community structure. The dominant taxonomic groups across all soils (>1% of all sequences) were Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Planctomycetes and Verrucomicrobia. The relative abundance of bacteria phylum and genus differed between soil types and between vegetation. Significant differences in relative abundance of bacteria phyla were only found for Gemmatimonadetes and Cyanobacteria between the pristine and the drained peat forest soils. At genus level, the relative abundance of several genera differed significantly between the peat soils with same or different tree species, including Burkholderia, Caulobacter, Opitutus, Mucilanginibacter, Acidocella, Mycobacterium, Bradyrhizobium, Dyella and Rhodanobacter.     

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.     

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.     

Peat–water interrelationships in a tropical peatland ecosystem in Southeast Asia

Interrelationships between peat and water were studied using a hydropedological modelling approach for adjacent relatively intact and degraded peatland in Central Kalimantan, Indonesia. The easy to observe degree of peat humification provided good guidance for the assignment of more difficult to measure saturated hydraulic conductivities to the acrotelm–catotelm hydrological system. Ideally, to prevent subsidence and fire, groundwater levels should be maintained between 40 cm below and 100 cm above the peat surface. Calculated groundwater levels for different years and for different months within a single year showed that these levels can drop deeper than the critical threshold of 40 cm below the peat surface whilst flooding of more than 100 cm above the surface was also observed. In July 1997, a dry El Niño year, areas for which deep groundwater levels were calculated coincided with areas that were on fire as detected from radar images. The relatively intact peatland showed resilience towards disturbance of its hydrological integrity whereas the degraded peatland was susceptible to fire. Hydropedological modelling identified areas with good restoration potential based on predicted flooding depth and duration. Groundwater level prediction maps can be used in fire hazard warning systems as well as in land utilization and restoration planning. These maps are also attractive tools to move from the dominant uni-sectoral approach in peatland resource management toward a much more promising multi-sectoral approach involving various forestry, agriculture and environment agencies. It is demonstrated that the combination of hydrology and pedology is essential for wise use of valuable but threatened tropical peatland ecosystems.     

Variation in the amount and quality of litterfall in a Pinus sylvestris L. stand growing on a bog

The amount and nutrient content of the above-ground litterfall was followed for 9 years in an unfertilized, PKMgB and NPKMgB fertilized Scots pine stand growing on a drained ombrotrophic bog in eastern Finland. The annual litterfall on unfertilized plots was 1995 kg ha⁻¹, of which needles accounted for 74%. The effective temperature sum (threshold value + 5°C) explained 99% of the annual variation in the amount of needle litterfall when the data from one atypical year were excluded from the analysis. Nutrient concentrations were, except for Fe, higher in needle litter than in the other litterfall fractions. Nitrogen, P and K concentrations were low in autumn, and those of Ca and Mn high, possibly owing to variation in the mobility of elements during senescence. The annual litterfall input of N to the soil was 12.4 kg ha⁻¹, and the corresponding values for P and K were 0.08 kg ha⁻¹ and 1.81 kg ha⁻¹, respectively. Fertilization reduced needle litterfall in the first year after treatment, but had no effect thereafter. The amount of other litterfall fractions was not affected by fertilization in any of the 9 years of the study. Nitrogen, P, K and B concentrations increased in the needle litter after both fertilization treatments. The results indicate long-term cycling of fertilizer nutrients on the site.     

若尔盖高寒泥炭地土壤有机碳储量估算的误差分析

以样品采集和质量控制模式(SAX)为指导,通过合理的采样设计和数据分析方法,估算若尔盖泥炭地土壤表层有机碳储量的估计值及其置信区间,并使用Robust方差分析进行定量化的误差分析,计算4类误差来源(样地间差异、采样深度、样地内差异和样品测定)的误差贡献率。结果表明,若尔盖泥炭地表层土壤有机碳储量估计值为43.21 kt/km²,其99%置信区间为40.08～46.33 kt/km²;误差分析结果表明,误差大部分来自样地间差异(贡献率为61.63%),远大于其他3类来源(采样深度：24.82%;样地内：10.85%;测定误差：2.70%);温度是最主要的样地间误差来源(贡献率为24.13%),降水和人为干扰也是重要的样地间误差来源(贡献率分别为21.02%和17.08%)。     

Impact of experimental drought and rewetting on redox transformations and methanogenesis in mesocosms of a northern fen soil

The impact of climate change on the greenhouse gas balance of peatlands is debated as they function both as sinks of carbon and significant sources of methane. To study redox transformations influencing methane production, we incubated two intact soil monoliths from a northern temperate fen and compared a permanently wet treatment to a treatment undergoing an experimentally induced drought for 50 days. Net turnover of dissolved inorganic carbon (DIC), methane (CH₄) and electron acceptors in the saturated zone was calculated using a mass balance approach, and sulfate gross reduction rates were determined using a ³⁵S radiotracer. Thermodynamic energy yield of different electron accepting processes was calculated and related to the observed respiration patterns. Permanently wet conditions lead to a depletion of electron acceptors within 50 days and onset of methanogenic conditions. During drought, electron acceptors were renewed and methanogenesis was temporarily suppressed in most of the peat for another 20-50 days after rewetting. Methanogenesis began, however, apparently locally before electron acceptors were fully depleted in the remainder of the peat, and iron and sulfate reduction occurred simultaneously. Anaerobic production of DIC could mostly but not fully be explained by reduction of nitrate, sulfate and ferric iron. Sulfate gross reduction rates of up to ∼450 nmol cm⁻³ d⁻¹ determined with ³⁵S-SO₄ and potentially explained the surplus of 50-60 mmol m⁻² of DIC production in one treatment; however, the sulfate pools were too small to sustain such rates beyond some hours to days. Furthermore, anaerobic DIC production proceeded at constant rates after depletion of dissolved inorganic electron acceptors, although not being balanced by methane production. An unknown electron acceptor was thus consumed, and sulfate and potentially other electron acceptors recycled, either by humic substances, by aerenchymatic oxygen transport, or by oxygen in the capillary fringe at low levels of air filled porosity.     

Effects of sulfate deposition on pore water dissolved organic carbon,nutrients, and microbial enzyme activities in a northern peatland

Export of dissolved organic carbon from lakes and streams has increased throughout Europe and North America over the past several decades. One possible cause is altered deposition chemistry; specifically, decreasing sulfate inputs leading to changes in ionic strength and dissolved organic carbon solubility. To further investigate the relationship between deposition chemistry and dissolved organic carbon export in peatlands, a field experiment was conducted to compare the pore water chemistry and peat microbial enzyme activity of mesocosms receiving sulfate amendments to mesocosms receiving no additions. To consider how peatlands respond during recovery from increased inputs of sulfate, samples were also analyzed from an area of the same peatland that was previously amended with sulfate. Current additions of sulfate decreased dissolved organic carbon concentration and increased dissolved organic carbon aromaticity. Total dissolved phosphorus decreased in response to current sulfate amendments but was elevated in the area of the peatland recovering from sulfate amendment. The total dissolved phosphorus increase, which was reflected in microbial enzyme activity, may have shifted the system from P limitation to N limitation. This shift could have important consequences for ecosystem processes related to plant and microbial communities. It also suggests that the recovery from previous sulfate amendments may take longer than may be expected.