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Substrate Quality (substrate + quality)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

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

FEMS MICROBIOLOGY ECOLOGY, Issue 3 2000
Inger Bergman
Abstract 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°C) without added substrate, or at 20°C with added substrate (glucose, or H2/CO2, or starch). Rates of methane production averaged over the season differed significantly (P<0.05, R2=0.76) among the five peat types, the minerotrophic lawn producing the highest rates, and the hummock peat producing the lowest. The seasonal average Q10 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, H2/CO2 or starch at 20°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. [source]

Temperature sensitivity and substrate quality in soil organic matter decomposition: results of an incubation study with three substrates

GLOBAL CHANGE BIOLOGY, Issue 6 2010
J. Å. MARTIN WETTERSTEDT
Abstract Kinetic theory suggests that the temperature sensitivity of decomposition of soil organic matter should increase with increasing recalcitrance. This ,temperature,quality hypothesis' was tested in a laboratory experiment. Microcosms with wheat straw, spruce needle litter and mor humus were initially placed at 5, 15 and 25 °C until the same cumulative amount of CO2 had been respired. Thereafter, microcosms from each single temperature were moved to a final set of incubation temperatures of 5, 15 and 25 °C. Straw decomposed faster than needle litter at 25 and 15 °C, but slower than needle litter at 5 °C, and showed a higher temperature sensitivity (expressed as Q10) than needle litter at low temperatures. When moved to the same temperature, needle litter initially incubated at 5 and 15 °C had significantly higher respiration rates in the final incubation than litters initially placed at 25 °C. Mor humus placed at equal temperatures during the initial and final incubations had higher cumulative respiration during the final incubation than humus experiencing a shift in temperature, both up- and downwards. These results indicate that other factors than substrate quality are needed to fully explain the temperature dependence. In agreement with the hypothesis, Q10 was always higher for the temperature step between 5 and 15 °C than between 15 and 25 °C. Also in agreement with the temperature,quality hypothesis, Q10 significantly increased with increasing degree of decomposition in five out of the six constant temperature treatments with needle litter and mor humus. Q10s for substrates moved between temperatures tended to be higher than for substrates remaining at the initial temperature and an upward shift in temperature increased Q10 more than a downward shift. This study largely supports the temperature,quality hypothesis. However, other factors like acclimation and synthesis of recalcitrant compounds can modify the temperature response. [source]

Effects of glucose, cellulose, and humic acids on soil microbial eco-physiology

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2004
Oliver Dilly
Abstract Microbial eco-physiology in soils is regulated by substrate quality of the organic matter. This regulation was studied for a forest and an agricultural soil by the combination of activity and biomass techniques. Soil respiration was stimulated by the substrate quality in the order, humic acid < cellulose < glucose over 20 days. Concurrently, substrate addition increased the respiratory quotient (RQ), defined as the ratio of mol CO2 evolution per mol O2 uptake. Anabolic processes were mainly induced by glucose addition. Soil preconditioned with glucose showed a decrease in the RQ value during glucose-induced microbial growth in comparison to non-amended control. The decrease in the RQ value induced by preconditioning with cellulose and humic acid was lower. Glucose, cellulose, and humic acid addition modified the microbial biomass as estimated by fumigation-extraction (FE), substrate-induced respiration (SIR), and ATP content. Since each biomass estimate refers to specific microbial components, shifts in microbial eco-physiology and community structure induced by substrate quality were reflected by SIR : FE and SIR : ATP ratios. The active and glucose-responsive biomass in the forest soil which was earlier suggested as being dominated by K-strategists was increased in the order, humic acid < cellulose < glucose. Einfluss von Zugaben von Glucose-, Cellulose und Huminsäuren auf die mikrobielle Ökophysiologie im Boden Die Ökophysiologie der mikrobiellen Gemeinschaften in Böden ist abhängig von der Substratqualität der organischen Substanz. Dies wurde nach Zugabe von Substraten für zwei Böden, einer unter Buchenwald und einer unter Acker, anhand einer Kombination von biochemischen und physiologischen Aktivitäts- und Biomassetechniken analysiert. Die Substratzugabe erhöhte die Bodenatmung über 20 Tage hinweg in der Reihenfolge Huminsäuren < Cellulose < Glucose. Gleichzeitig wurde auch der respiratorische Quotient (RQ), definiert als das Verhältnis von CO2 -Freisetzung zu O2 -Aufnahme, durch die Substratzugabe erhöht und anabolische Prozesse induziert. Das mikrobielle Wachstum wurde in erster Linie durch Glucose stimuliert. Der mit Glucose als Substrat versetzte Boden zeigte eine Abnahme des RQ während eines glucose-induzierten Wachstums im Vergleich zur Kontrolle. Eine solche Abnahme war bei der Huminsäure- und Cellulosebehandlung geringer. Die Zugabe von Glucose, Cellulose und Huminsäuren veränderte schließlich die mikrobielle Biomasse, welche mittels Fumigation-Extraktion, substratinduzierter Atmung und ATP-Gehalt ermittelt wurde. Da jede Technik spezifische mikrobielle Komponenten erfasst, wurden Veränderungen in der mikrobiellen Ökophysiologie und der Struktur der mikrobiellen Gemeinschaften durch die Substrate induziert, die in dem SIR:FE- und SIR:ATP-Verhältnis erkennbar waren. Die aktive und glucoseaktivierbare Biomasse in einem von K-Strategen dominierten Waldboden nahm von Huminsäure-, über Cellulose- und Glucosezugabe hin zu. [source]