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1.
N. D. Ananyeva E. A. Susyan I. M. Ryzhova E. O. Bocharnikova E. V. Stolnikova 《Eurasian Soil Science》2009,42(9):1029-1037
In two layers of the humus horizons in soddy-podzolic soils of different biogeocenoses (Kostroma oblast) representing a succession
series, the carbon content in the microbial biomass (Cmic) was determined using the method of substrate-induced respiration and the rate of microbial CO2 production (basal respiration, BR). The Cmic content was from 110 to 755 μg/g soil, and the BR was from 0.40 to 2.52 μg CO2-C/g/h. A gradual increase in the Cmic content and BR was found in the following sequence: cropland—fallow (7-year-old)—young (20- and 45-year-old) forests—secondary
and native (primary) forests (90- and 450-year-old, respectively). In the litter, the Cmic content was higher in the 45-year-old forest than in the secondary and native forests: 10423, 6459, and 4258 μg C/g of substrate,
respectively. The portion of Cmic in the soil organic carbon content in the upper layer of the soils studied varied from 1.3 to 5.4%; its highest value was
in the soils under the secondary and native forests. The pool of microbial biomass carbon and the microbial CO2 production in the upper 25-cm layer of the soils were calculated. 相似文献
2.
Influence of soil phosphorus status and nitrogen addition on carbon mineralization from 14C-labelled glucose in pasture soils 总被引:2,自引:0,他引:2
This study examines the effect of soil P status and N addition on the decomposition of 14C-labelled glucose to assess the consequences of reduced fertilizer inputs on the functioning of pastoral systems. A contrast
in soil P fertility was obtained by selecting two hill pasture soils with different fertilizer history. At the two selected
sites, representing low (LF) and high (HF) fertility status, total P concentrations were 640 and 820 mg kg–1 and annual pasture production was 4,868 and 14,120 kg DM ha–1 respectively. Soils were amended with 14C-labelled glucose (2,076 mg C kg–1 soil), with and without the addition of N (207 mg kg–1 soil), and incubated for 168 days. During incubation, the amounts of 14CO2 respired, microbial biomass C and 14C, microbial biomass P, extractable inorganic P (Pi) and net N mineralization were determined periodically. Carbon turnover was greatly influenced by nutrient P availability.
The amount of glucose-derived 14CO2 production was high (72%) in the HF and low (67%) in the LF soil, as were microbial biomass C and P concentrations. The 14C that remained in the microbial biomass at the end of the 6-month incubation was higher in the LF soil (15%) than in the
HF soil (11%). Fluctuations in Pi in the LF soil during incubation were small compared with those in HF soil, suggesting that P was cycling through microbial
biomass. The concentrations of Pi were significantly greater in the HF samples throughout the incubation than in the LF samples. Net N mineralization and nitrification
rates were also low in the LF soils, indicating a slow turnover of microorganisms under limited nutrient supply. Addition
of N had little effect on biomass 14C and glucose utilization. This suggests that, at limiting P fertility, C turnover is retarded because microbial biomass becomes
less efficient in the utilization of substrates.
Received: 18 October 1999 相似文献
3.
The effect of soil aeration status on carbon partitioning of a labelled organic substrate (14C-[U]-glucose) into CO2, microbial biomass, and extra-cellular metabolites is described. The soil was incubated in a continuous flow incubation apparatus under four different aeration conditions: (1) permanently aerobic, (2) permanently anaerobic, (3) shifted from anaerobic to aerobic, and (4) shifted from aerobic to anaerobic. The soil was pre-incubated for 10 days either under aerobic or under anaerobic conditions. Afterwards, glucose was added (315 g C g–1) and the soils were incubated for 72 h according to four treatments: aerobic or anaerobic conditions maintained, aerobic conditions shifted to anaerobic conditions and anaerobic conditions shifted to aerobic conditions. Carbon partitioning was measured 0, 8, 16, 24, 48 and 72 h after the glucose addition. In permanently aerobic conditions, the largest part of the consumed glucose was built into microbial biomass (72%), much less was mineralised to CO2 (27%), and only a negligible portion was transformed to soluble extra-cellular metabolites. Microbial metabolism was strongly inhibited when aeration conditions were changed from aerobic to anaerobic, with only about 35% of the added glucose consumed during the incubation. The consumed glucose was transformed proportionally to microbial biomass and CO2. In permanently anaerobic conditions, 42% of the consumed glucose was transformed into microbial biomass, 30% to CO2, and 28% to extra-cellular metabolites. After a shift of anaerobic to aerobic conditions, microbial metabolism was not suppressed and the consumed glucose was transformed mainly to microbial biomass (75%) and CO2 (23%). Concomitant mineralisation of soil organic carbon was always lower in anaerobic than in aerobic conditions. 相似文献
4.
The response of the microbial community to changes in aeration status, from oxic to anoxic and from anoxic to oxic, was determined
in arable soil incubated in a continuous flow incubation apparatus. Soil incubated in permanently oxic (air) and/or anoxic
(O2-free N2) conditions was used as the control. Before experiments soil was preincubated for 6 days, then aeration status was changed
and glucose added. Glucose concentration, extractable C, CO2 production, microbial biomass, pH and redox potential were determined 0, 4, 8, 12, 16, 24, 36 and 48 h after change of aeration
status. If oxic conditions were changed to anoxic, the amount of glucose consumed was reduced by about 60%, and CO2 production was 10 times lower at the end of incubation compared to the control (permanently oxic conditions). Microbial biomass
increased by 114% in glucose-amended soil but did not change in unamended soil. C immobilization prevailed over C mineralization.
Redox potential decreased from +627 mV to –306 mV. If anoxic conditions were changed to oxic, consumption of glucose and CO2 evolution significantly increased, compared to permanently anoxic conditions. Microbial biomass did not change in glucose-amended
soil, but decreased by 78% in unamended soil. C mineralization was accelerated. Redox potential increased from +238 to +541 mV.
The rate of glucose consumption was low in anoxic conditions if soil was incubated in pure N2 but increased significantly when incubation was carried out in a CO2/N2 mixture.
Received: 6 January 1999 相似文献
5.
Giancarlo Renella Amar M. Chaudri Céline M. Falloon Loretta Landi Paolo Nannipieri Philip C. Brookes 《Biology and Fertility of Soils》2007,43(6):751-758
We investigated Cd, Zn, and Cd + Zn toxicity to soil microbial biomass and activity, and indigenous Rhizobium leguminosarum biovar trifolii, in two near neutral pH clay loam soils, under long-term arable and grassland management, in a 6-month laboratory incubation,
with a view to determining the causative metal. Both soils were amended with Cd- or Zn-enriched sewage sludge, to produce
soils with total Cd concentrations at four times (12 mg Cd g−1 soil), and total Zn concentrations (300 mg Zn kg−1 soil) at the EU upper permitted limit. The additive effects of Cd plus Zn at these soil concentrations were also investigated.
There were no significant differences in microbial biomass C (B
C), biomass ninhydrin N (B
N), ATP, or microbial respiration between the different treatments. Microbial metabolic quotient (defined as qCO2 = units of CO2–C evolved unit−1 biomass C unit−1 time) also did not differ significantly between treatments. However, the microbial maintenance energy (in this study defined
as qCO2-to-μ ratio value, where μ is the growth rate) indicated that more energy was required for microbial synthesis in metal-rich sludge-treated soils (especially
Zn) than in control sludge-treated soils. Indigenous R.
leguminosarum bv. trifolii numbers were not significantly different between untreated and sludge-treated grassland soils after 24 weeks regardless of
metal or metal concentrations. However, rhizobial numbers in the arable soils treated with metal-contaminated sludges decreased
significantly (P < 0.05) compared to the untreated control and uncontaminated sludge-treated soils after 24 weeks. The order of decreasing
toxicity to rhizobia in the arable soils was Zn > Cd > Cd + Zn. 相似文献
6.
Soil-released carbon dioxide from microbial biomass carbon in the cultivated soils of karst areas of southwest China 总被引:1,自引:0,他引:1
Soil microbial biomass and the emission of CO2 from the soil surface were measured in yellow soils (Ultisols) of the karst areas of southwest China. The soils are relatively
weathered, leached and impoverished, and have a low input of plant residues. The measurements were made for a 1-year period
and show a reciprocal relationship between microbial biomass and surface CO2 efflux. The highest (42.6±2.8 mg CO2-C m–2 h–1) and lowest (15.6±0.6 mg CO2-C m–2 h–1) CO2 effluxes are found in the summer and winter, respectively. The cumulative CO2 efflux is 0.24 kg CO2-C m–2 year–1. There is also a marked seasonal variation in the amount of soil microbial biomass carbon, but with the highest (644±71 μg
C g–1 soil) and lowest (270±24 μg C g–1 soil) values occurring in the winter and summer, respectively. The cumulative loss of soil microbial biomass carbon in the
top 10 cm of the soil was 608 μg C g–1 year–1 soil over 17 sampling times. The mean residence time of microbial biomass is estimated at 105 days, suggesting that the carbon
in soil microbial biomass may act as a source of the CO2 released from soils.
Received: 13 July 1999 相似文献
7.
Successional changes in microbial biomass,respiration and nutrient status during litter decomposition in an aspen and pine forest 总被引:5,自引:0,他引:5
Microbial biomass, microbial respiration, metabolic quotient (qCO2), Cmic/Corg ratio and nutrient status of the microflora was investigated in different layers of an aspen (Populus tremuloides Michx.) and pine forest (Pinus contorta Loud.) in southwest Alberta, Canada. Changes in these parameters with soil depth were assumed to reflect successional changes in aging litter materials. The microbial nutrient status was investigated by analysing the respiratory response of glucose and nutrient (N and P) supplemented microorganisms. A strong decline in qCO2 with soil depth indicated a more efficient C use by microorganisms in later stages of decay in both forests. Cmic/Corg ratio also declined in the aspen forest with soil depth but in the pine forest it was at a maximum in the mineral soil layer. Microbial nutrient status in aspen leaf litter and pine needle litter indicated N limitation or high N demand, but changes in microbial nutrient status with soil depth differed strongly between both forests. In the aspen forest N deficiency appeared to decline in later stages of decay whereas P deficiency increased. In contrast, in the pine forest microbial growth was restricted mainly by N availability in each of the layers. Analysis of the respiratory response of CNP-supplemented microorganisms indicated that growth ability of microorganisms is related to the fungal-bacterial ratio. 相似文献
8.
This study examines the effects of atrazine on both microbial biomass C and C mineralization dynamics in two contrasting agricultural
soils (organic C, texture, and atrazine application history) located at Galicia (NW Spain). Atrazine was added to soils, a
Humic Cambisol (H) and a Gleyic Cambisol (G), at a recommended agronomic dose and C mineralization (CO2 evolved), and microbial biomass measurements were made in non-treated and atrazine-treated samples at different time intervals
during a 12-week aerobic incubation. The cumulative curves of CO2–C evolved over time fit the simple first-order kinetic model [Ct = Co (1 − e
−kt
)], whose kinetic parameters were quantified. Differences in these parameters were observed between the two soils studied;
the G soil, with a higher content in organic matter and microbial biomass C and lower atrazine application history, exhibited
higher values of the total C mineralization and the potentially mineralizable labile C pool than those for the H soil. The
addition of atrazine modified the kinetic parameters and increased notably the C mineralized; by the end of the incubation
the cumulative CO2–C values were 33–41% higher than those in the corresponding non-added soils. In contrast, a variable effect or even no effect
was observed on the soil microbial biomass following atrazine addition. The data clearly showed that atrazine application
at normal agricultural rates may have important implications in the C cycling of these two contrasting acid soils. 相似文献
9.
Addition of soluble organic substrates to soil has been shown to either increase or restrict the rate of microbial CO2–C evolution. This has been attributed to a priming effect resulting from accelerated or decreased turnover of the soil organic
matter including the soil microflora. We investigated microbial responses to small glucose-C additions (10–50 μg C g1 soil) in arable soils either amended or not with cellulose. An immediate CO2–C release between 0 and 69 h (equivalent to 59% of glucose-C applied) was measured. However, only half of the CO2–C respired could be attributed to the utilisation of glucose-C substrate, based on the percentage of 14C–CO2 evolved after the addition of a 14C-labelled glucose tracer. Thus, although no evidence of an immediate release of ‘extra’ C above the rate applied as glucose-C
was observed, the pattern of decomposition for 14C-glucose suggested utilisation of an alternate C source. Based on this, a positive priming effect (1.5 to 4.3 times the amount
CO2–C evolved that was attributed to glucose-C decomposition) was observed for at least 170 h in non-cellulose-amended soil and
612 h in cellulose-amended soil. Two further phases of microbial activity in cellulose-amended soils were attributed to either
activation of different microbial populations or end-product inhibition of cellulase activity after glucose addition. During
these subsequent phases, a negative priming effect of between 0.1 and 1.5 times was observed. Findings indicate that the response
of the microbial community to small additions of soluble organic C substrate is not consistent and support the premise that
microbial response varies in a yet to be predicted manner between soil type and ecosystems. We hypothesise that this is due
to differences in the microbial community structure activated by the addition of organic C and the timing of soluble organic
substrate addition with respect to the current dissolved organic C status of the soil. 相似文献
10.
E. A. Susyan N. D. Ananyeva E. G. Gavrilenko O. V. Chernova M. V. Bobrovskii 《Eurasian Soil Science》2009,42(10):1148-1155
In the mineral horizons of the soils under different southern taiga forests (oak, archangel spruce, and aspen in the Kaluzhskie
Zaseki Reserve of Kaluga region and the green moss spruce and spruce-broadleaved forests of the Zvenigorod Biological Station
of Moscow State University in Moscow region), the carbon content in the microbial biomass (Cmic), the rate of the basal respiration (BR), and the specific microbial respiration (qCO2= BR/Cmic) were determined. The Cmic content was measured using the method of substrate-induced respiration (SIR). In the upper humus horizons of the soils, the
Cmic content amounted to 762–2545 μg/g and the BR ranged from 1.59 to 7.55 μg CO2-C/g per h. The values of these parameters essentially decreased down the soil profiles. The portion of Cmic in the organic carbon of the humus horizons of the forest soils was 4.4 to 13.2%. The qCO2values increased with the depth in the soils of the Biological Station and did not change in the soils of the Reserve. The
pool of Cmic and Corg and the microbial production of CO2 (BR) within the forest soil profiles are presented. 相似文献
11.
An arable soil with organic matter formed from C3-vegetation was amended initially with maize cellulose (C4-cellulose) and sugarcane sucrose (C4-sucrose) in a 67-day laboratory incubation experiment with microcosms at 25 °C. The amount and isotopic composition (13C/12C) of soil organic C, CO2 evolved, microbial biomass C, and microbial residue C were determined to prove whether the formation of microbial residues depends on the quality of the added C source adjusted with NH4NO3 to the same C/N ratio of 15. In a subsequent step, C3-cellulose (3 mg C g−1 soil) was added without N to soil to determine whether the microbial residues formed initially from C4-substrate are preferentially decomposed to maintain the N-demand of the soil microbial community. At the end of the experiment, 23% of the two C4-substrates added was left in the soil, while 3% and 4% of the added C4-cellulose and C4-sucrose, respectively, were found in the microbial biomass. The addition of the two C4-substrates caused a significant 100% increase in C3-derived CO2 evolution during the 5-33 day incubation period. The addition of C3-cellulose caused a significant 50% increase in C4-derived CO2 evolution during the 38-67 day incubation period. The decrease in microbial biomass C4-C accounted for roughly 60% of this increase. Cellulose addition promoted microorganisms strongly able to recycle N immediately from their own tissue by “cryptic growth” instead of incorporating NO3− from the soil solution. The differences in quality of the microbial residues produced by C4-cellulose and C4-sucrose decomposing microorganisms are also reflected by the difference in the rates of CO2 evolution, but not in the rates of net N mineralization. 相似文献
12.
Haiyan Chu Jianguo Zhu Xiangui Lin Rui Yin Zubin Xie Zhihong Cao Takeshi Fujii 《Biology and Fertility of Soils》2007,43(6):811-814
In this study, we investigated the effects of lanthanum (La), one of the rare earth elements (REEs), on microbial biomass
C as well as the decomposition of 14C-labelled glucose in a fluvo-aquic soil in 28 days. The soil was collected from the field plots under maize/wheat rotation
in Fengqiu Ecological Experimental Station of Chinese Academy of Sciences, Henan Province, China. Application of La decreased
soil microbial biomass C during the experimental period, and there was a negative correlation (P < 0.01) between microbial biomass and application rate of La. La increased microbial biomass 14C after 14C glucose addition, and the increase was significant (P < 0.05) at the rates of more than 160 mg kg−1 soil. La slightly increased 14CO2 evolution at lower rates of application but decreased it at higher rates 1 day after 14C glucose addition, while there was no significant effect from days 2 to 28. For the cumulative 14CO2 evolution during the incubation of 28 days, La slightly increased it at the rates of less than 120 mg kg−1 soil, while significantly decreased (P < 0.05) it at the rate of 200 mg kg−1 soil. The results indicated that agricultural use of REEs such as La in soil could decrease the amount of soil microbial
biomass and change the pattern of microbial utilization on glucose C source in a short period. 相似文献
13.
Effects of increasing periods under intensive arable vegetable production on biological, chemical and physical indices of soil quality 总被引:6,自引:0,他引:6
The effects on soil condition of increasing periods under intensive cultivation for vegetable production on a Typic Haplohumult
were compared with those of pastoral management using soil biological, physical and chemical indices of soil quality. The
majority of the soils studied had reasonably high pH, exchangeable cation and extractable P levels reflecting the high fertilizer
rates applied to dairy pasture and more particularly vegetable-producing soils. Soil organic C (Corg) content under long-term pasture (>60 years) was in the range of 55 g C kg–1 to 65 g C kg–1. With increasing periods under vegetable production soil organic matter declined until a new equilibrium level was attained
at about 15–20 g C kg–1 after 60–80 years. The loss of soil organic matter resulted in a linear decline in microbial biomass C (Cmic) and basal respiratory rate. The microbial quotient (Cmic/Corg) decreased from 2.3% to 1.1% as soil organic matter content declined from 65 g C kg–1 to 15 g C kg–1 but the microbial metabolic quotient (basal respiration/Cmic ratio) remained unaffected. With decreasing soil organic matter content, the decline in arginine ammonification rate, fluorescein
diacetate hydrolytic activity, earthworm numbers, soil aggregate stability and total clod porosity was curvilinear and little
affected until soil organic C content fell below about 45 g C kg–1. Soils with an organic C content above 45 g C kg–1 had been under pasture for at least 30 years. At the same Corg content, soil biological activity and soil physical conditions were markedly improved when soils were under grass rather
than vegetables. It was concluded that for soils under continuous vegetable production, practices that add organic residues
to the soil should be promoted and that extending routine soil testing procedures to include key physical and biological properties
will be an important future step in promoting sustainable management practices in the area.
Received: 18 November 1997 相似文献
14.
Immobilization and mineralization of nitrogen in a saline and alkaline soil during microbial use of sugarcane filter cake amended with glucose 总被引:1,自引:0,他引:1
Ghulam Rasul Ahtsham A. Khan Khalid S. Khan Rainer Georg Joergensen 《Biology and Fertility of Soils》2009,45(3):289-296
A 42-day incubation was conducted to study the effect of glucose and ammonium addition adjusted to a C/N ratio of 12.5 on
sugarcane filter cake decomposition and on the release of inorganic N from microbial residues formed initially. The CO2 evolved increased in comparison with the non-amended control from 35% of the added C with pure +5 mg g−1 soil filter cake amendment to 41% with +5 mg g−1 soil filter cake +2.5 mg g−1 soil glucose amendment to 48% with 5 mg g−1 soil filter cake +5 mg g−1 soil glucose amendment. The different amendments increased microbial biomass C and microbial biomass N within 6 h and such
an increase persisted. The fungal cell-membrane component ergosterol initially showed a disproportionate increase in relation
to microbial biomass C, which completely disappeared by the end of the incubation. The cellulase activity showed a 5-fold
increase after filter cake addition, which was not further increased by the additional glucose amendment. The cellulase activity
showed an exponential decline to values around 4% of the initial value in all treatments. The amount of inorganic N immobilized
from day 0 to day 14 increased with increasing amount of C added, in contrast to the control treatment. After day 14, the
immobilized N was re-mineralized at rates between 1.3 and 1.5 μg N g−1 soil d−1 in the treatments being more than twice as high as in the control treatment. This means that the re-mineralization rate is
independent of the actual size of the microbial residues pool and also independent of the size of the soil microbial biomass. 相似文献
15.
Estimating the active and total soil microbial biomass by kinetic respiration analysis 总被引:1,自引:0,他引:1
A model describing the respiration curves of glucose-amended soils was applied to the characterization of microbial biomass.
Both lag and exponential growth phases were simulated. Fitted parameters were used for the determination of the growing and
sustaining fractions of the microbial biomass as well as its specific growth rate (μ
max). These microbial biomass characteristics were measured periodically in a loamy silt and a sandy loam soil incubated under
laboratory conditions. Less than 1% of the biomass oxidizing glucose was able to grow immediately due to the chronic starvation
of the microbial populations in situ. Glucose applied at a rate of 0.5 mg C g–1 increased that portion to 4–10%. Both soils showed similar dynamics with a peak in the growing biomass at day 3 after initial
glucose amendment, while the total (sustaining plus growing) biomass was maximum at day 7. The microorganisms in the loamy
silt soil showed a larger growth potential, with the growing biomass increasing 16-fold after glucose application compared
to a sevenfold increase in the sandy loam soil. The results gained by the applied kinetic approach were compared to those
obtained by the substrate-induced respiration (SIR) technique for soil microbial biomass estimation, and with results from
a simple exponential model used to describe the growth response. SIR proved to be only suitable for soils that contain a sustaining
microbial biomass and no growing microbial biomass. The exponential model was unsuitable for situations where a growing microbial
biomass was associated with a sustaining biomass. The kinetic model tested in this study (Panikov and Sizova 1996) proved
to describe all situations in a meaningful, quantitative and statistically reliable way.
Received: 19 July 1999 相似文献
16.
Maize straw and pea straw were added to five Pakistani soils from a gradient in salinity to test the following hypotheses: Increasing salinity at high pH decreases proportionally (1) the decomposition of added straw and (2) the resulting net increase in microbial biomass. In the non-amended control soils, salinity had depressive effects on microbial biomass C, biomass N, but not on biomass P and ergosterol. The ratios microbial biomass C-to-N and biomass C-to-P decreased consistently with increasing salinity. In contrast, the ergosterol-to-microbial biomass C ratio was constant in the four soils at pH>8.9, but nearly doubled in the most saline, but least alkaline, soil (pH 8.2). The addition of the maize and pea straw always increased the contents of microbial biomass C, biomass N, biomass P and ergosterol, but without clear effects of salinity. Highest mean contents of microbial biomass C and biomass N were measured at day 0, immediately after the straw was added. Straw amendments increased the CO2 evolution rates of all five soils without any effect of salinity. The same was true for total C and total N in the two fractions of particulate organic matter (POM) 63–400 μm and >400 μm. Lowest percentage of straw-derived CO2-C and highest recoveries of POM-C and POM-N were observed in the maize straw treatment and the reverse in the pea straw treatment. Yield coefficients were calculated for maize and pea straw based on the assumption that the balance gap between CO2 and the amount of POM can be fully assigned to microbial products. 相似文献
17.
Decomposition rates of the [2-14C]-glucose and [2-14C]-glycine in four different soils of the long-term field trial of Moscow were investigated in a 3-months laboratory experiment in which 14CO2 respiration was measured. A model with three decomposition components and two distribution parameters was developed and validated with the data of the experiment. The decay rate constants of free [2-14C]-glucose (4–32 day-1) were slower than those of [2-14C]-glycine (16–44 day-1). The calculated use efficiency for microbial biosynthesis of the second carbon atom was 47% for glucose and 31% for glycine. The potential half-life of labelled carbon in the microbial soil biomass ranged from 0.6 to 4.4 days, depending on the soil type and the initial amount of added substrate. The calculated total utilisation of carbon by the soil biomass from glycine was about 2–5 times lower than that of glucose.The modelled 14C incorporation into the microbial soil biomass reached its maximum on the first day of the incubation experiment and did not exceed 22% of the 14C input. Both of the investigated substances decomposed most rapidly in the soil samples from sites that have not being fertilised with organic or mineral fertilisers during an 81-years period. 相似文献
18.
The critical S concentration and S requirement of the soil microbial biomass of a granitic regosol was examined. S was applied
at the rate of 0, 5, 10, 20, 30 and 50 μg S as MgSO4·7H2O, together with either 3000 μg glucose-C or 3333 μg cellulose-C, 400 μg N, and 200 μg P g –1 soil and 200 μg K g–1 soil. Microbial biomass, inorganic SO4
2–-S, and CO2 emission were monitored over 30 days during incubation at 25 °C. Both glucose and cellulose decomposition rates responded
positively to the S made available for microbial cell synthesis. The amounts of microbial biomass C and S increased with the
level of applied S up to 10 μg S g–1 soil and 30 μg S g–1 soil in the glucose- and cellulose-amended soil, respectively, and then declined. Incorporated S was found to be concentrated
within the microbial biomass or partially transformed into soil organic matter. The concentration of S in the microbial biomass
was higher in the cellulose- (4.8–14.2 mg g–1) than in the glucose-amended soil (3.7–10.9 mg g–1). The microbial biomass C:S ratio was higher in the glucose- (46–142 : 1) than in the cellulose-amended soil (36–115 : 1).
The critical S concentration in the microbial biomass (defined as that required to achieve 80% of the maximum synthesis of
microbial biomass C) was estimated to be 5.1 mg g–1 in the glucose- and 10.9 mg g–1 in the cellulose-amended soil. The minimum requirement of SO4
2–-S for microbial biomass formation was estimated to be 11 μg S g–1 soil and 21 μg S g–1 soil for glucose- and cellulose-amended soil, respectively. The highest levels of activity of the microbial biomass were
observed at the SO4
2–-S concentrations of 14 μg S g–1 soil and 17 μg S g–1 soil, for the glucose and cellulose amendments, respectively, and were approximately 31–54% higher during glucose than cellulose
decomposition.
Received: 20 October 1999 相似文献
19.
M. A. Sánchez-Monedero C. Mondini M. L. Cayuela A. Roig M. Contin M. De Nobili 《Biology and Fertility of Soils》2008,44(6):885-890
The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential
microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of
soil microflora, measured by the microbial biomass C (B
C) and CO2 evolution, respectively. Three different composting mixtures at different phases of the composting process were added to
a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately
increased B
C and both measures of microbial activity (FDA and CO2 evolution). Highly significant correlations were found between FDA hydrolysis and B
C for soil amended with the three composting mixtures (r = 0.81–0.96; P < 0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely
to CO2 evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect
different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass
in freshly amended soils, despite the disturbance caused by the exogenous organic matter. 相似文献
20.
C. Mondini M. L. Cayuela M. A. Sanchez-Monedero A. Roig P. C. Brookes 《Biology and Fertility of Soils》2006,42(6):542-549
The soil microbial biomass survives as a largely dormant population for long periods without fresh substrates, depending for growth upon a rapid uptake of substrates when they become available. Currently, little investigation has been made into the mechanisms involved in the transition from dormancy to activity. We found that additions of trace amounts of different simple and complex substrates (glutamic acid, amino acids mixture, glucose, protein hydrolysates, carbohydrates, compost extract), even at very low application rates (5-μg C g−1 soil), caused an immediate and significant activation (measured as increased CO2-C evolved) of the soil microbial biomass. The different substrates caused different intensities of respiration response, which were related to the substrates’ composition, complexity, and degradability. The difference between the CO2-C evolved from the amended soil minus that evolved from a similarly incubated but non-amended soil ranged from 80 to 160% of the humified carbon C added as substrate, with most of the substrates causing a positive priming effect, in agreement with previous findings. The activation ended after 5–70 h, depending on the substrate, but the microbial biomass could be reactivated with further additions. It seems that the microbial biomass first responds to traces of substrate by increasing its metabolic activity in anticipation of a larger ‘food event’. Overall, these results indicate that soil micro-organisms have evolved metabolic and physiological strategies that allow them to survive and growth in the generally poor-substrate soil environment.Contribution presented at the Exploratory Workshop: ‘Non-molecular manipulation of soil microbial communities’, held at the University of Udine, Udine, Italy from 17 to 20 October, 2004. The workshop was funded by the European Science Foundation and the University of Udine. 相似文献