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1.
《Applied soil ecology》2011,47(3):413-421
Substrate input as well as climatic factors affect C and N cycling and microbial properties in forest soils. We used a microcosm approach to investigate the response of CO2 efflux, net N mineralization, and microbial community-level physiological profile (CLPP) to temperature (5 vs. 15 °C) and substrate (with and without sucrose addition) addition in surface mineral soils collected from 4-, 6-, 13-, and 15-year old (ages in 2007) hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) stands in northern Alberta. In the early stage of incubation (0–2 h), CO2 efflux was higher at 5 °C than at 15 °C with little effect from substrate addition, while 24 h after the addition of substrate, CO2 efflux became higher under the 15 °C incubation. After 72 h incubation, temperature and substrate addition effects on CO2 efflux subsided and CO2 efflux rates tended to converge among the treatments. Net N mineralization was significantly affected by substrate addition and stand age, while rates of net ammonification were higher at 5 °C than at 15 °C. Net N mineralization occurred without sucrose addition while net immobilization occurred with sucrose addition. The soil from the youngest stand had the lowest N mineralization rate among the stands for each corresponding substrate-incubation temperature treatment. We used Ecoplates from Biolog™ to study sole-carbon-source-utilization profiles of microbial communities at the end of the incubation. Principal component analysis of C utilization data separated microbial communities with respect to substrate addition, incubation temperature and stand age. Our data showed that organic matter mineralization and microbial substrate utilization were affected by incubation temperature, substrate availability and stand age, indicating that the responses of microbial communities in the studied hybrid poplar plantations to temperature changes were strongly mediated by labile C availability and stand development. 相似文献
2.
It has been suggested by others that the size of the flush of mineralization caused by CHC13 fumigation can be used to estimate the amount of microbial biomass in soils. Calculation of biomass from the flush requires that the proportion of CHCl3-killed cell C mineralized be known. To determine this proportion, 15 species of [14C]labelled fungi and 12 species of [14C]labelled bacteria were added to four types of soil and these were fumigated for 24 h with CHC13, reinoculated with unfumigated soil, and incubated at 22°C for 10 days. The average percentage mineralization of the fungi was 43.7 ± 5.3, while the average for the bacteria was 33.3 ± 9.9. Using a 1:3 ratio for distribution of total biomass between the bacterial and fungal populations, respectively, it was calculated that the average mineralization of both types of cells was 41.1%. In experiments conducted to determine if CHC13 vapour alters stabilized microbial metabolites or dead microbial cells in a manner which makes them more susceptible to degradation, it was found that both fumigated and unfumigated dead fungal materials mineralized to the same extent in soil during 10 days of incubation. 相似文献
3.
We show that both temperature and priming act differently on distinct C pools in a temperate grassland soil. We used SOM which was 14C-labelled in four different ways: by labelling soil with 14C-glucose, by adding leaf litter from plants pre-labelled with 14CO2, and by labelling in situ with 14CO2 applied to the ryegrass canopy either 6 or 18 months earlier. Samples of each type of 14C labelled soil were incubated at either 4, 10, 15, or 20 °C and the exponential loss of 14CO2 used to characterise treatment effects. 14C allocation to microbial fractions was greater, and so overall mineralization by microbes was greater, as temperature rose, but turnover of the microbial labile pool was temperature-insensitive, and the turnover of microbial structural material was reduced as temperature rose. The ability of the microbial population to degrade just one fraction of plant litter was increased greatly by temperature. A pool of SOM with a half-life of about 70 d was degraded faster at higher temperatures. Less tractable but abundant pools of SOM were not accessed more readily at higher temperatures by the microbial population. Priming with glucose or amino-acids only speeded the mineralization of recent SOM (probably from the living microbial biomass), and was not altered by temperature. These results have implications for the impacts of climate change on soil C cycling. 相似文献
4.
Effect of temperature on the mineralization of C and N of fresh and mature compost in sandy material
Information about the mineralization rate of compost at various temperatures is a precondition to optimize mineral N fertilization and to minimize N losses in compost‐amended soils. Objectives were to quantify the influence of the temperature on the mineralization rate and leaching of dissolved organic carbon (DOC) and nitrogen (DON), NO3—, and NH4+ from a fresh (C : N = 15.4) and a mature (C : N = 9.2) organic household waste compost. Compost samples were mixed with quartz sand to ensure aerobic conditions, incubated at 5, 10, 15, 20, and 25°C and irrigated weekly for 112 days. For the fresh compost, cumulative CO2 evolution after 112 days ranged from 36% of the initial C content at 5°C to 54% at 25°C. The CO2 evolution was only small in the experiments with mature compost (1 to 6% of the initial C content). The data were described satisfactorily by a combined first‐order (fresh compost) or a first‐order kinetic model (mature compost). For the fresh compost, cumulative DOC production was negatively related to the temperature, probably due to leaching of some of the partly metabolized easily degradable fractions at lower temperatures. The production ratios of DOC : CO2‐C decreased with increasing temperature from 0.094 at 5°C to 0.038 at 25°C for the fresh and from 1.55 at 5°C to 0.26 at 25°C for the mature compost. In the experiments with fresh compost, net release of NO3— occurred after a time lag which depended on the temperature. Cumulative net release of NO3— after 112 days ranged from 1.8% of the initial N content at 5°C to 14.3% at 25°C. Approximately 10% of the initial N content of the mature compost was released as NO3— after 14 days at all temperatures. The DOC : DON ratios in the experiments using fresh compost ranged from 11.5 to 15.7 and no temperature dependency was observed. For the mature compost, DOC : DON ratios were slightly smaller (7.4 to 8.9). The DON : (NH4+ + NO3—) ratio decreased with increasing temperature from 0.91 at 5°C to 0.19 at 25°C for the fresh compost and from 0.21 at 5°C to 0.12 at 25°C for the mature compost. The results of the dynamics of C and N mineralization of fresh and mature compost can be used to assess the appropriate application (timing and amount) of compost to soils. 相似文献
5.
The time-course of 14CO2 formation in chernozem soil samples enriched with 1- or 2-14C-2, 4-dichlorophenoxyacetic acid (50 μg g g?1 air-dry soil) was determined during incubation at 28°C. Except for the initial phase of decomposition, when the conversion of carboxyl carbon to 14CO2 predominated over that of carbon in position 2, the rates of mineralization of the two carbon atoms of the side chain of the herbicide molecule exhibited no significant difference. The exponential phase of 14CO2 evolution lasted from the 3rd to the 21st day of incubation; a semilogarithmic plot of its time dependence was strictly linear. The mineralization activity doubling time in this phase was 89.1 ± 3.6 h with 1-14CO-2, 4-D and 85.4 ± 5. l h with 2-14CO-2,4-D. An exponential decrease in mineralization activity was observed after 21 days, probably due to substrate exhaustion. The total proportion of radioactive carbon introduced into the soil in the form of 1- or 2-14CO-2,4-D and converted into 14CO2 during 31 days of incubation was about 33%. Plate counts of bacteria increased during 35 days of incubation from 2.14 × 108 to 2.8 × 108 g?1. The proportion of bacteria capable of producing 14CO2 from the labelled herbicide increased in this period from 4.1 to 86.1%. This increase is probably directly responsible for the immediate onset of mineralization of the herbicide in soil treated previously with it or in soil inoculated with a suspension prepared from a sample previously incubated with the herbicide. 相似文献
6.
《Soil biology & biochemistry》2001,33(7-8):1049-1057
The long-term effects of temperature on soil C mineralisation were investigated in two experiments using 14C labelled wheat straw incubated in organic soils from five coniferous forests located in different climate zones of Western Europe. In the first experiment, samples were incubated in the laboratory at 4, 10, 16, 23 or 30°C, with constant moisture, and the loss of 14C was monitored for 550 days. Double negative exponential functions fitted to the 14C loss data at different temperatures were used to define the relative proportions of labile and recalcitrant components in the original straw. The estimated proportions of these constituents were related to incubation temperatures with the amount of C reflecting the labile fraction increasing with increasing temperature. In the second experiment samples mixed with the labelled straw were incubated at 4, 16 or 30°C until the same percentage of 14C loss was reached. The samples were then incubated again at a common temperature for 30 days and CO2 production was measured to assess the lability of the remaining material. For all the soils, the amount of readily decomposed material was higher in samples conditioned at 4° than at 30°C. It was concluded that in addition to temperature controlling rates of C mineralisation in soil it also affects the processes of decomposition so that material produced at higher temperatures was more recalcitrant than at lower temperatures. 相似文献
7.
Five microbial species (Aspergillus flavus, Trichoderma viride, Streptomyces sp., Arthrobacter sp., Achromobacter liquefaciens) were cultivated in liquid media containing 14C-labelled glucose. The decomposition of these microorganisms was recorded in four different soils after chloroform fumigation by a technique related to that proposed by Jenkinson and Powlson, to determine the mineralization rate of microbial organic matter (Kc coefficient). Three treatments were used: untreated soil, fumigated soil alone and fumigated soil supplied with 14C-labelled cells. Total evolved CO2 and 14CO2 were measured after 7 and 14 days at 28°C.The labelled microorganisms enabled the calculation of mineralization rate Kc (Kc = mineralized microbial carbon/supplied microbial carbon). The extent of mineralization of labelled microbial carbon depended on the type of soil and on the microbial species. Statistical analysis of results at 7 days showed that 58% of the variance is taken in account by the soil effect and 32% by the microorganism effect. Between 35 and 49% of the supplied microbial C was mineralized in 7 days according to the soil type and the species of microorganism. Our results confirmed that the average value for Kc = 0.41 is acceptable, but Kc variability according to soil type must be considered.The priming effect on organic C and native microbial biomass mineralization, due to microbial carbon addition was obtained by comparison between the amount of non-labelled CO2-C produced by fumigated soils with or without added labelled microorganisms: this priming effect was generally negligible.These results indicate that the major portion of the error of microbial biomass measurement comes from the Kc estimation. 相似文献
8.
Glucose or starch labelled with 14C was mixed thoroughly into slurried soils. Aggregates of different sizes were obtained from the soils as they dried. The labelled substrates were considered to be distributed in both micro- and macropores in the aggregates. Control samples (labelled substrates in macropores only) were prepared by adding the labelled carbohydrates after the formation of the aggregates. The various samples were sterilized by γ-irradiation and stored at ?15°C.Samples were wetted to about ?20kPa, inoculated with soil organisms, and incubated for 4 weeks at 28°C in closed systems, which enabled regular measurement of 14CO2 released.Based on the 14CO2 released, it was concluded that starch was protected from microbial attack when present in micropores in aggregates made from fine sandy loam.After incubation samples were dried and rewetted. The flush of 14CO2 released was twice as big for samples containing labelled starch compared with glucose, showing that disruption of aggregates, containing residual starch, and rearrangements of soil components are as important as chemical and biological factors in causing the flush of CO2 resulting from wetting a soil. Mechanical disruption of the aggregates resulted in a similar flush of 14CO2. 相似文献
9.
Temperature effects on N mineralization: changes in soil solution composition and determination of temperature coefficients by TDR 总被引：3，自引：0，他引：3
We studied the changes in composition of the soil solution following mineralization of N at different temperatures, with a view to using TDR to calculate temperature coefficients for the mineralization of N. Mineralization from soil organic nitrogen was measured during aerobic incubation under controlled conditions at six temperatures ranging from 5.5 to 30°C, and at constant water content in a loamy sand soil. We also monitored during the incubation the concentrations of SO42–, Cl–, HCO3–, Ca2+, K+, Mg2+ and Na+, and the pH and the electrical conductivity in 1:2 soil:water extracts. Zero‐order N mineralization rates ranged between 0.164 at 5.5°C and 0.865 mg N kg?1 soil day?1 at 30°C. There was a significant decrease in soil pH during incubation, of up to 0.6 pH units at the end of the incubation at 30°C. The electrical conductivity of the soil extracts increased significantly at all temperatures (the increase between the start and the end of the incubation was 4‐fold at 30°C) and was strongly correlated with N mineralization. The ratio of bivalent to monovalent cations increased markedly during mineralization (from 2.2 to 5.9 at 30°C), and this increase influenced the evolution of the electrical conductivity of the soil solution through the differences in molar‐limiting ion conductivity between mainly Ca2+ and K+. Zero‐order mineralization rate constants, k, for NO3– concentrations calculated from TDR varied between 0.070 (at 5.5°C) and 0.734 mg N kg?1 soil day?1 (at 30°C), which were slightly smaller, but in the same range, as the measured rates. Underestimation of the measured N mineralization rates was due, at least in part, to differences in cation composition of the soil solution between calibration and mineralization experiments. A temperature‐dependence model for N mineralization from soil organic matter was fitted to both the measured and the TDR‐calculated mineralization rates, k and kTDR, respectively. There were no significant differences between the model parameters from the two. Our results are promising for further use of TDR to monitor soil organic N mineralization. However, the influence of changing cation ratios will also have to be taken into account when trying to predict N mineralization from measured electrical conductivities. 相似文献
10.
Effect of Temperature on Bio-Kinetic Coefficients in UASB Treatment of Municipal Wastewater 总被引：1，自引：0，他引：1
Upflow anaerobic sludge blanket (UASB)reactors were used to treat municipal wastewater attemperatures of 6, 11, 15, 20 and 32 °C and athydraulic retention times (HRTs) ranging from 48 to 3 h overan operational period of approximately 860 days. The Monodmodel was used to evaluate substrate utilization. TheArrhenius model was used to calculate the activationenergies from which temperature coefficients weredetermined. It was found that the maximum specific substrateutilization rate constant (k) decreased from 0.387 d-1(at 32 °C) to 0.041 d-1 (at 6 °C). Thedecay rate constant (kd), yield coefficient (Yg),half velocity constant (Ks) and maximum specific growthrate (μm ) were also impacted by temperature in theUASB treatment of municipal wastewater. 相似文献
11.
Kasaina Sitraka Andrianarisoa Lydie Dufour Séverine Bienaimé Bernhard Zeller Caroline Choma Christian Dupraz 《European Journal of Soil Science》2023,74(4):e13390
Studies about nitrogen (N) mineralization and nitrification in deep soil layers are rare because N processes are considered to occur mainly in topsoil that hosts active and diverse microbial communities. This study aimed to measure the soil potential net N mineralization (PNM) and nitrification (PNN) down to 4 m depth and to discuss factors controlling their variability. Twenty-one soil cores were collected at the Restinclières agroforestry experimental site, where 14-year-old hybrid walnut trees were intercropped with durum wheat. Soil cores were incubated in the dark in the laboratory at both 6 and 25°C. The soil was a deep calcic fluvisol with a fluctuating water table. It featured a black layer that was very rich in organic matter and permanently water saturated at depths between 3.0 and 4.0 m. The mean soil mineral N content was 3 mg N kg−1 soil in the upper 0.0–0.2 m layer, decreasing until a depth of 2 m and increasing to the maximum value of 25.8 mg N kg−1 soil in the black layer. While nitrate (NO3−) was the dominant form of mineral N (89%) in the upper 0.0–0.2 m layer, its proportion progressively decreased with depth until ammonium (NH4+) became almost the only form of mineral N (97%) in the saturated black layer. Laboratory soil incubation revealed that PNM and PNN occurred at all depths, although the latter remained low at 6°C. The soil nitrate content in the black layer was multiplied by 48 times after 51 days of incubation at 25°C, whereas it was almost inexistent at the sampling date. While the soil total N, the pH and the incubation temperature explained 84% of the variation in PNM, only 29% of the percent nitrification variance was explained by the incubation temperature (Tinc) and the soil C-to-N ratio. These results point out the necessity to consider soil potential net N mineralization and nitrification of deep soil layers to improve model predictions. 相似文献
12.
Blue grama (Bouteloua gracilis (H.B.K.) Lag.) was grown at day (14 h) and night temperatures of 25° and 15°C, respectively, in a 14CO2-atmosphere during the last 31 of the 55 days from germination to seed set (period 1). An air-tight seal separated the shoot and root spheres. This period was followed by 21 days of a 14°C day (10 h) and 38°C night regime, and 29 days of continuous ?5°C (period 2), and 26 days of the original temperature and light conditions (period 3). Distribution of the assimilated 14C at the end of period 1 was: roots 33%; root-derived organic matter in the soil 23%; and 22% was released as CO2. The washed root mass to root-derived soil organic matter ratio of the labelled 14C was 60 to 40. A root mass decrease of 45% over the cool and frost period changed this ratio to 23 to 77. Polysaccharides and 0.1 n NaOH-extractable organic matter decreased while potential dehydrogenase activity and total organic P increased during this same period, thereby confirming field related observations. Measured dehydrogenase activity overwinter may have two different origins. As total C content of the soil did not increase under the conditions of the experiment, it was postulated that a portion of the observed increase in total C in the field overwinter was of inorganic rather than organic origin. 相似文献
13.
The microbial population of a Brown Chernozemic soil was labelled in situ by adding 14C-glucose and 15NH415NO3 to the plow layer. The loss of 14C, nitrogen immobilization-mineralization reactions, bacterial numbers (plate count, direct count) and fungal hyphal lengths were determined periodically throughout the growing period in amended and unamended microplots and in the surrounding field soil. After 5 days, 90 per cent of the labelled N occurred in the organic form with little subsequent mineralization. Of the labelled C added, 63, 56 and 39 per cent, remained in the soil after 3, 14 and 104 days, respectively.The ratio of fungal C to bacterial C increased as soil moisture decreased. Viable (plate count) and total numbers of bacteria in samples from unamended plots and field soil were significantly correlated with each other and with soil moisture. Fungal hyphal lengths from amended soil were also significantly related to moisture but the rate of loss of 14C and mineralization of 15N were not. The synthesized microbial material (tissue and metabolites) exhibited a high degree of stability throughout the study. The half-life of labelled C remaining in the soil after 30 days was calculated to be 6 months compared to only 4 days for the added glucose C. The amount of energy used for maintenance by the soil population under field conditions was calculated from measurements of biomass C, respired labelled C and respired soil C. 相似文献
14.
《Communications in Soil Science and Plant Analysis》2012,43(21):2734-2753
Laboratory experiments were conducted to (i) study the influence of chemical composition of organic substrates (green manure, rice straw, wheat straw, and farmyard manure) and temperature on carbon (C) mineralization under flooded and nonflooded moisture conditions, (ii) study the relationship between C mineralization and chemical composition of organic materials, and (iii) model C mineralization kinetics under different temperature and moisture conditions. The proportion of added C mineralized under nonflooded conditions ranged between 45 and 66% at 35 °C compared to 18 to 42% at 15 °C. Flooding the soil reduced the proportion of added C mineralized, which ranged between 25 to 47% at 35 °C and 6 to 20% at 15 °C. Water-soluble components, cellulose, lignin, and nitrogen content of the organic source significantly influenced C mineralization. Temperature sensitivity of decomposition depended on the quality of the organic substrate with relatively less decomposable farmyard manure (FYM) being more sensitive (Q10 ?3.0) than the easily decomposable green manure (Q10 ?2.5). A first-order monocomponent model that is based on relative rate of mineralization and includes a parameter for speed of aging best described C mineralization under both the temperature and moisture conditions. It was concluded that FYM with preponderance of recalcitrant components and low decomposability provides greater C sequestration potential than green manure and crop residues. 相似文献
15.
Y. Prabhakara Rao V. Uma Devi D. G. V. Prasada Rao 《Water, air, and soil pollution》1988,37(3-4):365-374
The effect of temperature on Cu accumulation and depuration in the tissues of Cerithidea cingulata was studied at 18 °C, 28 °C, and 38 °C. The LC50 value for 5 days was observed to be high at ambient temperature (28 °C) that at the high temperature (38 °C). The LC50 for 10 days at the low temperature (18 °C) was higher than at the ambient (28 °C). When exposed to sublethal concentrations for 48 hr, the tissue accumulation of Cu was found to be more at the high temperature than at the ambient and low temperature. The depuration process was faster at high temperatures, and the animals returned to normal condition after 36 hr. At the ambient and low temperature, Cu accumulation was slow and prolonged, and the animals resumed to normal condition after 48 and 72 hr, respectively. The gonad-digestive gland (GDG) complex was found to show greater changes in accumulation and depuration process when compared to foot and viscera. 相似文献
16.
Talaat El Sebaï Marion Devers-Lamrani Bernard Lagacherie Nadine Rouard Guy Soulas Fabrice Martin-Laurent 《Biology and Fertility of Soils》2011,47(4):427-435
The impact of soil moisture content and temperature on isoproturon (3-(4-isopropylphenyl)-1,1-dimethyl-urea [IPU]) mineralization
activity was assessed on an agricultural soil regularly exposed to this herbicide. Mineralization of 14C-IPU was monitored on soil microcosms incubated at different temperatures (10°C, 20°C, 28°C) and soil moisture contents (9%,
12%, 15, 18%, 21%, 24%). An increase in temperature and/or soil moisture significantly enhanced the maximum rate and percentage
of IPU mineralization while it decreased the lag time before mineralization. The maximum rate and percentage of IPU mineralization
respectively ranged from 0.18% day−1 and 9% for the lowest temperature and soil moisture content pair (10°C–9%) to 1.51% day−1 and 27.1% for the highest pair (28°C–24%). Statistics revealed a cross interaction of temperature and soil moisture content
on the maximum rate of IPU mineralization. The optimum conditions for IPU mineralization, estimated from the double Gaussian
model, were 25.8°C and 24% soil moisture content. The influence of fluctuations in soil moisture content on IPU-mineralization
was investigated by subjecting the soil microcosms to drought stress. When IPU was added at the end of the drought stress,
it had no statistical effect on IPU mineralization. However, when it was added before the drought stress, two mineralization
phases were observed: (1) one corresponding to the drought stress for which mineralization was low and (2) another one observed
after restoration of soil moisture content characterized by higher mineralization rate. It can be concluded that climatic
fluctuations affect the activity of IPU mineralizing microbial community, and may lead to an increase in IPU persistence. 相似文献
17.
Effects of storage time and straw content of cattle slurry on the mineralization of nitrogen and carbon in soil 总被引：2，自引：0，他引：2
P. Sørensen 《Biology and Fertility of Soils》1998,27(1):85-91
Animal slurries are stored for a variable period of time before application in the field. The effect of cattle slurry storage
time and temperature on the subsequent mineralization of C and N in soil was studied under laboratory conditions. Urine and
faeces from a dairy cow were sampled separately and mixed to a slurry. After 4 weeks of storage under anaerobic conditions
at 15 °C, the NH4
+ N content exceeded the original urinary N content of the slurry; the NH4
+ content increased only slightly during the following 16 weeks of storage. After 4 weeks of storage, the proportion of slurry
C in volatile fatty acids (VFA) amounted to 10% and increased to 15% after 20 weeks. Straw addition to the slurry caused an
increase of VFA-C in stored slurry, but had a negligible influence on the proportion of slurry N in the form of NH4
+. Slurries subjected to different storage conditions were added to a sandy and a sandy loam soil. After 1 week, the preceding
storage period (0–20 weeks) and temperature (5 °C or 15 °C) had no significant effect on the net release of inorganic N
from the slurry in soil. Thus, the increased NH4
+ content in the slurry after storage was followed by increased net N immobilization in soil. Additional straw in the slurry
caused increased net N immobilization only in the sandy loam soil. Following anaerobic storage, 8–14% of slurry C was released
in gaseous form, and the net mineralization of slurry C after 12 weeks in soil amounted to 54–63%. The extra net mineralization
of C in soil due to straw in slurry was equivalent to 76% of straw C, suggesting that the straw accelerated the mineralization
of C derived from faeces, urine and/or soil.
Received: 25 August 1997 相似文献
18.
J.‐M. Séquaris M. Herbst L. Weihermüller J. Bauer H. Vereecken 《European Journal of Soil Science》2010,61(6):940-949
14C‐labelled fresh organic matter (FOM) was homogeneously incorporated into an agricultural topsoil of small total organic carbon (TOC) content in order to perform decomposition batch experiments at temperatures (T) ranging from 5 to 45°C and soil gravimetric water contents (w) ranging from 7 to 35%. After 4–6‐month incubation (tend), the residual 14C (Dend) was measured in bulk soil (0–2000 µm) and soil particle size fractions of 0–53, 53–200 and 200–2000 µm by chemical dispersion and sieving. The 14C‐FOM decomposition kinetics from soil were fitted either by a single first‐order reaction (rate constant, k0–2000) assuming only a one‐pool model in the bulk soil or by consecutive first‐order reactions (rate constants, k0–53 and k53–2000) assuming a two‐pool model in the bulk soil aggregate structure. In the latter case, a two‐step reaction mechanism involving a FOM particle‐size decrease along the soil fractions was considered where k0–53 was assumed to be a limiting rate constant. The 14C‐FOM decomposition kinetics was described for the experimental temperature and water ranges by Arrhenius and Michaelis‐Menten relationships, respectively. Additionally, the results obtained by the adapted Arrhenius physicochemical relationship were compared with the function proposed by Kirschbaum (1995) . Scaling functions Tm and wm were established and can be used to simulate FOM decomposition rates under different temperature and moisture level conditions. Modelling based on consecutive first‐order reactions supported the hypothesis that the circulation (inflow and outflow) of C into the soil particle small‐size fractions (<53 µm) controls the total C mineralization. 相似文献
19.
R.J.K. Myers 《Soil biology & biochemistry》1975,7(2):83-86
Ammonification of soil organic N and nitrification of ammonium-N was studied in Tindall clay loam over a range of temperatures from 20–60 C. Nitrification rates at each temperature were constant throughout the 28 day incubation, whereas most of the ammonification occurred in the first 7 days. The optimum for nitrification was close to 35 C. exhibiting a sharp peak at this temperature at which the potential rate was 4.8 μg N/g day?1, compared with 0.5 μg N/g day?1 at 20°C and 0.25 μg N/g day?1 at 60°C. The optimum temperature for ammonification was approximately 50°C at which the rate was 2.8 μg N/g day?1 in the first 7 days but only 0.5 μg N/g day?1 between 14 and 28 days.The temperature responses could be described mathematically with functions of the type logoN = k × 1/T.The results are discussed in relation to daily patterns of N mineralization in the field where temperatures show diurnal fluctuation. 相似文献
20.
Oat straw, hay, and alfalfa litter, differing in microbial colonization and recalcitrance, were added to organic matter–free quartz sand (5 mg C [g material]–1) and incubated in the laboratory at 5°C, 10°C, 15°C, 20°C, and 25°C. Different incubation periods were chosen so that theoretically the same amounts of CO2 would be produced and the same amounts of O2 would be consumed for each litter type. It was investigated whether Q10 values (change in respiration rate between two temperatures) increase with decreasing temperature and how much these Q10 values and also the respiratory quotient (RQ: mol CO2/mol O2) depend on the litter type. The sums of CO2‐C evolved and O2 consumed, but also the contents of microbial biomass C and microbial biomass N showed a nearly 7‐fold increase in the order oat straw < hay < alfalfa litter. In contrast, the ratio of the fungal cell‐membrane component ergosterol to microbial biomass C was highest in the oat straw (4.1‰) and lowest in the alfalfa litter (0.2‰). This ratio reached a similar level between 5°C and 15°C (1.9‰), significantly higher (p = 0.01) than the level at 20°C (0.9‰). Respiration was similar between 20°C and 25°C, with a mean Q10 value of 1.9. The use of temperature rate‐modifying factors suggested by the carbon‐turnover model ROTHC revealed that the incubation period for similar respiration rates was underestimated at 5°C and overestimated at 25°C. The lignin‐poor and protein‐rich alfalfa litter showed the highest Q10 values of the three litter types in the medium temperature range of 10°C to 20°C. In contrast, the lignin‐rich and protein‐poor oat straw showed significantly highest Q10 values at 5°C and 25°C in comparison with the other two litter types. The RQ was significantly highest in the hay litter (1.05) and in comparison with alfalfa litter (0.97) and oat straw (0.92). Strong temperature‐dependent variations in Q10 values and respiratory quotients suggest interactions between litter quality, microbial colonization of litter, and temperature, which warrants further investigation. 相似文献