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High C/N Ratio (high + c_ratio)
Selected AbstractsHolocene peat growth and decay dynamics in sub-arctic peat plateaus, west-central CanadaBOREAS, Issue 1 2009A. BRITTA K. SANNEL Peat and net carbon accumulation rates in two sub-arctic peat plateaus of west-central Canada have been studied through geochemical analyses and accelerator mass spectrometry (AMS) radiocarbon dating. The peatland sites started to develop around 6600,5900 cal. yr BP and the peat plateau stages are characterized by Sphagnum fuscum peat alternating with rootlet layers. The long-term peat and net carbon accumulation rates for both profiles are 0.30,0.31 mm/yr and 12.5,12.7 gC/m2yr, respectively. These values reflect very slow peat accumulation (0.04,0.09 mm/yr) and net carbon accumulation (3.7,5.2 gC/m2yr) in the top rootlet layers. Extensive AMS radiocarbon dating of one profile shows that accumulation rates are variable depending on peat plateau stage. Peat accumulation rates are up to six times higher and net carbon accumulation rates up to four times higher in S. fuscum than in rootlet stages. Local fires represented by charcoal remains in some of the rootlet layers result in very low accumulation rates. High C/N ratios throughout most of the peat profiles suggest low degrees of decomposition due to stable permafrost conditions. Hence, original peat accretion has remained largely unaltered, except in the initial stages of peatland development when permafrost was not yet present. [source] What do dung beetles eat?ECOLOGICAL ENTOMOLOGY, Issue 6 2007PETER HOLTER Abstract 1.,Most adult coprophagous beetles feed on fresh dung of mammalian herbivores, confining ingestion to small particles with measured maximum diameters from 2,5 to 130 ,m, according to body size and kind of beetle. This study explores benefits and costs of selective feeding in a ,typical' dung beetle with a maximum diameter of ingested particles (MDIP) of 20 ,m. 2.,Examined dung types (from Danish domestic sheep, cattle and horse, and African wild buffalo, white rhino and elephant) contained 76,89% water. Costs of a 20 ,m MDIP were often low, since 69,87% of the total nitrogen in bulk dung other than that of elephant and rhino (40,58%) was available to selective feeders. 3.,Nitrogen concentrations were high , and C/N ratios low , in most types of bulk dung compared with the average food of terrestrial detritivores or herbivores. Exceptions were elephant and rhino dung with low nitrogen concentrations and high C/N ratios. 4.,Estimated C/N ratios of 13,39 in bulk dung (sheep,elephant) were decreased by selective feeding to 7.3,12.6 in the ingested material. In assimilated food, ratios are probably only 5,7, as most assimilable nitrogen and carbon may be of microbial origin. If so, the assimilable food contains a surplus of nitrogen relative to carbon. 5.,The primary advantage of selective feeding, particularly in dung with a high C/N ratio, may be to concentrate assimilable carbon in the ingested food. Effects of changing the MDIP within 20,106 ,m are modest, especially in dung with a low C/N ratio. [source] Nitrogen-regulated effects of free-air CO2 enrichment on methane emissions from paddy rice fieldsGLOBAL CHANGE BIOLOGY, Issue 9 2006XUNHUA ZHENG Abstract Using the free-air CO2 enrichment (FACE) techniques, we carried out a 3-year mono-factorial experiment in temperate paddy rice fields of Japan (1998,2000) and a 3-year multifactorial experiment in subtropical paddy rice fields in the Yangtze River delta in China (2001,2003), to investigate the methane (CH4) emissions in response to an elevated atmospheric CO2 concentration (200±40 mmol mol,1 higher than that in the ambient atmosphere). No significant effect of the elevated CO2 upon seasonal accumulative CH4 emissions was observed in the first rice season, but significant stimulatory effects (CH4 increase ranging from 38% to 188%, with a mean of 88%) were observed in the second and third rice seasons in the fields with or without organic matter addition. The stimulatory effects of the elevated CO2 upon seasonal accumulative CH4 emissions were negatively correlated with the addition rates of decomposable organic carbon (P<0.05), but positively with the rates of nitrogen fertilizers applied in either the current rice season (P<0.05) or the whole year (P<0.01). Six mechanisms were proposed to explain collectively the observations. Soil nitrogen availability was identified as an important regulator. The effect of soil nitrogen availability on the observed relation between elevated CO2 and CH4 emission can be explained by (a) modifying the C/N ratio of the plant residues formed in the previous growing season(s); (b) changing the inhibitory effect of high C/N ratio on plant residue decomposition in the current growing season; and (c) altering the stimulatory effects of CO2 enrichment upon plant growth, as well as nitrogen uptake in the current growing season. This study implies that the concurrent enrichment of reactive nitrogen in the global ecosystems may accelerate the increase of atmospheric methane by initiating a stimulatory effect of the ongoing dramatic atmospheric CO2 enrichment upon methane emissions from nitrogen-poor paddy rice ecosystems and further amplifying the existing stimulatory effect in nitrogen-rich paddy rice ecosystems. [source] Effects of organic matter and initial carbon,nitrogen ratio on the bioconversion of volatile fatty acids from sewage sludgeJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2008Xiaoling Liu Abstract BACKGROUND: The biodegradable organic matter and the initial carbon,nitrogen ratio can be substantially different in different batches of sewage sludge, which results in a difference in the acidification efficiency of sludge. Using sewage sludge from three different sources, batch tests were performed to analyze the relationship between volatile fatty acids (VFAs) and consumed organic matter, and to investigate the effects of initial carbon,nitrogen (C/N) ratio on the acidification efficiency of sludge. RESULTS: Maximum yields of 152.1 ± 3.5 mg total VFAs-COD per gram volatile solid (VS) added and 22.4 ± 1.2 mg butyric acid-COD g,1 VS added were obtained from the sludge with the highest initial C/N ratio. Statistical analysis indicated that protein was the major substrate for the produced VFAs. The sludge with the least initial C/N ratio (5.01) had the least yield, and only acetic acid, which was also mainly related to protein, was detected. CONCLUSION: The initial carbon,nitrogen ratio was one of the most important factors influencing the distribution patterns of VFAs and the yield of total VFAs produced from sewage sludge. A high C/N ratio could not only improve the yield of total VFAs but also enhance the yield of butyric acid. Copyright © 2008 Society of Chemical Industry [source] What do dung beetles eat?ECOLOGICAL ENTOMOLOGY, Issue 6 2007PETER HOLTER Abstract 1.,Most adult coprophagous beetles feed on fresh dung of mammalian herbivores, confining ingestion to small particles with measured maximum diameters from 2,5 to 130 ,m, according to body size and kind of beetle. This study explores benefits and costs of selective feeding in a ,typical' dung beetle with a maximum diameter of ingested particles (MDIP) of 20 ,m. 2.,Examined dung types (from Danish domestic sheep, cattle and horse, and African wild buffalo, white rhino and elephant) contained 76,89% water. Costs of a 20 ,m MDIP were often low, since 69,87% of the total nitrogen in bulk dung other than that of elephant and rhino (40,58%) was available to selective feeders. 3.,Nitrogen concentrations were high , and C/N ratios low , in most types of bulk dung compared with the average food of terrestrial detritivores or herbivores. Exceptions were elephant and rhino dung with low nitrogen concentrations and high C/N ratios. 4.,Estimated C/N ratios of 13,39 in bulk dung (sheep,elephant) were decreased by selective feeding to 7.3,12.6 in the ingested material. In assimilated food, ratios are probably only 5,7, as most assimilable nitrogen and carbon may be of microbial origin. If so, the assimilable food contains a surplus of nitrogen relative to carbon. 5.,The primary advantage of selective feeding, particularly in dung with a high C/N ratio, may be to concentrate assimilable carbon in the ingested food. Effects of changing the MDIP within 20,106 ,m are modest, especially in dung with a low C/N ratio. [source] | ||||||||||