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1.
脉冲式降水对不同类型草地土壤微生物呼吸碳释放量的影响 总被引:1,自引:0,他引:1
降水事件引起土壤短时间内释放大量CO2的现象常称为降水脉冲效应。降水事件发生后,由于水分和养分可获得性快速提升使土壤微生物呼吸速率快速升高至正常水分状况的数倍,从而导致土壤CO2大量释放并一定程度上影响着生态系统碳循环过程和土壤碳平衡,尤其在干旱或半干旱地区。利用自主研发的能快速测定土壤微生物呼吸速率的装置,对内蒙古三类典型草原(草甸草原、典型草原和荒漠草原)土壤分别开展土壤复湿实验(60%饱和含水量),并采用高频测定(48 h测定288次)。在土壤复湿后在所有温带草地类型中均发生了明显的脉冲效应,降水脉冲过程中单位有机质(土壤有机碳,SOC)最大呼吸速率(RSOC-max)整体表现为荒漠草原(1.59 mg C g-1 SOC h-1)>草甸草原(0.73 mg C g-1 SOC h-1)>典型草原(0.50 mg C g-1 SOC h-1);而脉冲效应的持续时间(Dura... 相似文献
2.
为了解华南人工林的碳固存机制,对广东鹤山的尾叶桉(Eucalyptus urophylla)纯林、30种树种混交林、10种树种混交林、红椎(Castanopsis hystrix)纯林、厚荚相思(Acacia crassicarpa)纯林5种人工林(林龄2–5 a)的土壤总呼吸(Rs)和自养呼吸(Ra)的季节变化进行了研究。结果表明,从2007年到2012年,5种人工林的Rs为81.3~103.9 mg C m–2h–1,Ra为11.2~22.3 mg C m–2h–1,自养呼吸贡献率(RC)为12.4%~26.9%,且5种人工林间的Rs、Ra及RC差异不显著。5种人工林湿季的Rs均显著大于干季的,平均高出311.4%;Ra、RC的季节性差异不显著。湿季土壤温度与Rs具有显著相关性,土壤温度解释了90.2%的变异,而两者关系在干季不显著。人工林间的微环境和土壤条件差异不明显,可能是由于造林时间短,土壤还处于干扰的恢复过程中,导致人工林间土壤呼吸差异不显著。 相似文献
3.
Summary Physical characteristics, namely floc density function, floc size distribution, and relative floc strength, of a number of flocculent yeast types were measured. A straight-line relationship was found to exist between log values of size and density for the yeasts examined. Each yeast type had coefficients from this relationship which could be used to interpret settling behaviour. Indices of relative floc strength were also obtained and together with the floc density function allowed fuller interpretation of yeast settling than with simpler theories.Symbols
a
constant (g·cm-3)
-
B
2/B
1
floc binding strength of floc2 relative to floc1
-
d
f
floc diameter (cm)
-
d
i
image diameter on print (cm)
-
d
max
maximum floc diameter (cm)
-
f
d
Ploc effective density (g·cm-3)
-
g
gravitational constant (981 cm·s-1)
-
K
p
constant (-)
-
R
l
rate of enlargement on film
-
R
2
rate of enlargement on print
-
S
s
density of suspending liquid phase (g·cm-3)
-
S
f
density of solid (floc) phase (g·cm-3)
-
U
t
terminal settling velocity (cm·s-1)
-
u
liquid viscosity (g·cm-3·-1) 相似文献
4.
Key components of swimming metabolism: standard metabolism (Rs), active metabolism (Ra) and absolute aerobic scope for activity (Ra–Rs) were determined for small age 0 year Atlantic cod Gadus morhua. Gadus morhua juveniles grew from 0·50 to 2·89 g wet body mass (MWB) over the experimental period of 100 days, and growth rates (G) ranged from 1·4 to 2·9% day?1, which decreased with increasing size. Metabolic rates were recorded by measuring changes in oxygen consumption over time at different activity levels using modified Brett‐type respirometers designed to accommodate the small size and short swimming endurance of small fishes. Power performance relationships were established between oxygen consumption and swimming speed measurements were repeated for individual fish as each fish grew. Mass‐specific standard metabolic rates () were calculated from the power performance relationships by extrapolating to zero swimming speed and decreased from 7·00 to 5·77 μmol O2 g?1 h?1, mass‐specific active metabolic rates () were calculated from extrapolation to maximum swimming speed (Umax) and decreased from 26·18 to 14·35 μmol O2 g?1 h?1 and mass‐specific absolute scope for activity was calculated as the difference between active and standard metabolism () and decreased from 26·18 to 14·35 μmol O2 g?1 h?1 as MWB increased. Small fish with low Rs had bigger aerobic scopes but, as expected, Rs was higher in smaller fish than larger fish. The measurements and results from this study are unique as Rs, Ra and absolute aerobic scopes have not been previously determined for small age 0 year G. morhua. 相似文献
5.
A. S. Afschar H. Biebl K. Schaller K. Schügerl 《Applied microbiology and biotechnology》1985,22(6):394-398
Summary To increase the solvent productivity of the acetone-butanol fermentation, a continuous culture of Clostridium acetobytylicum with cell recycling was used. At a dry cell mass concentration of 8 g l-1 and a dilution rate of D=0.64 h-1, a solvent productivity of 5.4 g l-1 h-1 was attained. To prevent degeneration of the culture, which occurs with high concentrations of solvents (acetone, butanol and ethanol), different reactor cascades were used. A two-stage cascade with cell recycling and turbidostatic cell concentration control turned out to be the best solution, the first stage of which was kept at relatively low cell and product concentrations. A solvent productivity of 3 and 2.3 g l-1 h-1, respectively, was achieved at solvent concentrations of 12 and 15 g l-1.Symbols
D
Dilution rate (h-1)
-
r
p
solvent productivity (g l-1 h-1)
-
s
residual glucose concentration (g l-1)
-
V
R
reactor volume (l)
-
V
O
overall volume (l)
-
x
(dry) cell mass concentration (g l-1)
-
Y
P/S
solvent yield (g g-1) 相似文献
6.
《Journal of bryology》2013,35(2):101-103
AbstractPhotosynthetic responses to light intensity were studied under laboratory conditions in seven bryophyte species from evergreen laurel forest, a threatened habitat, on Terceira island in the Azores. Four mosses (Andoa berthelotiana, Echinodium prolixum, Fissidens serrulatus, Myurium hochstetteri) and three liverworts (Bazzania azorica, Frullania tamarisci, Lepidozia cupressina) were selected to encompass a range of potential responses to variations in the forest light environment. Carbon dioxide exchange measurements were made, using an infra-red gas-analyser, at photosynthetic photon flux densities (PPFD) of 0-900 µmol m-2 s-1 and a mean temperature of 21°C in fully hydrated shoots. Most species achieved light saturation of photosynthesis below 30 µmol m-2 s-1, the lowest value being for A. berthelotiana (20 µmol m-2 s-1) and the highest for M. hochstetteri (68 µmol m-2 s-1). The liverwort F. tamarisci had the highest maximum photosynthetic rate (Pmax, 23 µmol CO2 g-1 h-1) whereas Pmax was lowest in the mosses E. prolixum and M. hochstetteri (10 µmol CO2 g-1 h-1). Dark respiration rate, a critical factor in toleration of shade by forest floor plants, was highest in the species with the highest values for Pmax. Compensation point was extremely low (7 µmol photons m-2 s-1) in Fissidens serrulatus, a species found in the deep shade of forest ravines and caves, and highest in M. hochstetteri a moss restricted to better illuminated habitats within and outside the forest. No photoinhibition was detected during the relatively short exposures to high irradiances. Comparison of these responses with data on the forest light environment indicates that, despite the possession of considerable shade adaptations, during winter in the evergreen laurel forest, low light levels may often limit photosynthetic rates of the bryophytes. 相似文献
7.
We studied water loss in eight insular populations of the lizard Anolis cristatellus wileyae and in one population of A. ernestwilliamsi in the British Virgin Islands. We found a strong negative correlation between habitat aridity and total and cutaneous water loss rate (ranging from 1.5–10.3 mg g?1 h?l) and a strong positive correlation between habitat aridity and integument resistance to water loss (28.5?199.0 s cm?1). Water loss and integumentary resistance of A. ernestwilliamsi were similar to what would be predicted for A. cristatellus living in the same habitat. The Guana Island population of A. cristatellus was significantly different from all other populations. We believe two processes are responsible; phenotypic plasticity explains most of the observed variability, but genetic differentiation may be responsible for the distinction of lizards from Guana. 相似文献
8.
The growth of Hansenula polymorpha and Kloeckera sp. 2201 with a mixture of glucose and methanol (38.8%/61.2%, w/w) and the regulation of the methanol dissimilating enzymes alcohol oxidase, catalase, formaldehyde dehydrogenase and formate dehydrogenase were studied in chemostat culture, as a function of the dilution rate. Both organisms utilized and assimilated glucose and methanol simultaneously up to dilution rates of 0.30 h-1 (H. polymorpha) and 0.26h-1, respectively (Kloeckera sp. 2201) which significantly exceeded max found for the two yeasts with methanol as the only source of carbon. At higher dilution rates methanol utilisation ceased and only glucose was assimilated. Over the whole range of mixed-substrate growth both carbon sources were assimilated with the same efficiency as during growth with glucose or methanol alone.In cultures of H. polymorpha, however, the growth yield for glucose was lowered by the unmetabolized methanol at high dilution rates. During growth on both carbon sources the repression of the synthesis of all catabolic methanol enzymes which is normally caused by glucose was overcome by the inductive effect of the simultaneously fed methanol. In both organisms the synthesis of alcohol oxidase was found to be regulated differently as compared to catalase, formaldehyde and formate dehydrogenase. Whereas increasing repression of the synthesis of alcohol oxidase was found with increasing dilution rates as indicated by gradually decreasing specific activities of this enzyme in cell-free extracts, the specific activities of this enzyme in cell-free extracts, the specific activities of catalase and the dehydrogenases increased with increasing growth rates until repression started. The results indicate similar patterns of the regulation of the synthesis of methanol dissimilating enzymes in different methylotrophic yeasts.Abbreviations and Terms C1
Methanol
- C6
glucose; D dilution rate (h-1)
-
D
c
critical dilution rate (h-1)
-
q
s
specific, rate of substrate consumption (g substrate [g cell dry weight]-1 h-1)
-
q
CO2 and q
O2
are the specific rates of carbon dioxide release and oxygen consumption (mmol [g cell dry weight]-1 h-1)
- RQ
respiration quotient (q
CO2
q
O2
1
)
-
s
0(C1) and s
0(C6)
are the concentrations of methanol and glucose in the inflowing medium (g l-1)
-
s
residual substrate concentration in the culture liquid (g l-1)
- Sp. A.
enzyme specific activity
- x
cell dry weight concentration (gl-1)
-
Y
X/C6
growth yield on glucose (g cell dry weight [g substrate]-1 相似文献
9.
M. L. F. Giuseppin 《Applied microbiology and biotechnology》1984,20(3):161-165
Summary The influence of the concentration of oxygen on lipase production by the fungus Rhizopus delemar was studied in different fermenters. The effect of oxygen limitation ( 47 mol/l) on lipase production by R. delemar is large as could be demonstrated in pellet and filamentous cultures. A model is proposed to describe the extent of oxygen limitation in pellet cultures. Model estimates indicate that oxygen is the limiting substrate in shake flask cultures and that an optimal inoculum size for oxygen-dependent processes can occur.Low oxygen concentrations greatly negatively affect the metabolism of R. delemar, which could be shown by cultivation in continuous cultures in filamentous growth form (Doptimal=0.086 h-1). Continuous cultivations of R. delemar at constant, low-oxygen concentrations are a useful tool to scale down fermentation processes in cases where a transient or local oxygen limitation occurs.Symbols and Abbreviations CO
Oxygen concentration in the gas phase at time = 0 (kg·m-3)
- CO
2i
Oxygen concentration at the pellet liquid interface (kg·m-3)
- CO
2i
Oxygen concentration in the bulk (kg·m-3)
-
D
Dilution rate (h-1)
- IDO
2
Diffusion coefficient for oxygen (m2·s-1)
-
dw
Dry weight of biomass (kg)
-
f
Conversion factor (rs
O
2 to oxygen consumption rate per m3) (-)
-
k
Radial growth rate (m·s-1)
-
K
Constant
-
kla
Volumetric mass transfer coefficient (s-1)
-
klA
Oxygen transfer rate (m-3·s-1)
-
kl
Mass transfer coefficient (m·s-1)
-
K
O
2
Affinity constant for oxygen (mol·m-3)
-
K
w
Cotton plug resistance (m-3·s-1)
-
M
Henry coefficient (-)
-
NV
Number of pellets per volume (m-3)
-
R
Radius (m)
-
RO
Radius of oxygen-deficient core (m)
-
RQ
Respiration quotient (mol CO2/mol O2)
-
rs
O
2
Specific oxygen consumption rate per dry weight biomass (kg O2·s-1[kg dw]-1)
-
rX
Biomass production rate (kg·m-3·s-1)
-
SG
Soytone glucose medium (for shake flask experiments)
-
SG
4
Soytone glucose medium (for tower fermenter and continuous culture experiments)
-
V
Volume of medium (m-3)
-
X
Biomass (dry weight) concentration (kg·m-3)
-
XR
o
Biomass concentration within RO for a given X (kg·m-3)
-
Y
O
2
Biomass yield calculated on oxygen (kg dw/kg O2)
-
Thiele modulus
-
Efficiency factor =1-(RO/R)3 (-)
-
Growth rate (m-1·s-1·kg1/3)
-
Dry weight per volume of pellet (kg·m-3) 相似文献
10.
Seasonal changes in the contribution of root respiration to total soil respiration in a cool-temperate deciduous forest 总被引:32,自引:0,他引:32
A trenching method was used to determine the contribution of root respiration to soil respiration. Soil respiration rates in a trenched plot (R
trench) and in a control plot (R
control) were measured from May 2000 to September 2001 by using an open-flow gas exchange system with an infrared gas analyser. The decomposition rate of dead roots (R
D) was estimated by using a root-bag method to correct the soil respiration measured from the trenched plots for the additional decaying root biomass. The soil respiration rates in the control plot increased from May (240–320 mg CO2 m–2 h–1) to August (840–1150 mg CO2 m–2 h–1) and then decreased during autumn (200–650 mg CO2 m–2 h–1). The soil respiration rates in the trenched plot showed a similar pattern of seasonal change, but the rates were lower than in the control plot except during the 2 months following the trenching. Root respiration rate (R
r) and heterotrophic respiration rate (R
h) were estimated from R
control, R
trench, and R
D. We estimated that the contribution of R
r to total soil respiration in the growing season ranged from 27 to 71%. There was a significant relationship between R
h and soil temperature, whereas R
r had no significant correlation with soil temperature. The results suggest that the factors controlling the seasonal change of respiration differ between the two components of soil respiration, R
r and R
h. 相似文献
11.
A O Ejiofor Y Chisti M Moo-Young 《Journal of industrial microbiology & biotechnology》1996,16(2):102-109
A fermentation medium based on millet (Pennisetum typhoides) flour hydrolysate and a four-phase feeding strategy for fed-batch production of baker's yeast,Saccharomyces cerevisiae, are presented. Millet flour was prepared by dry-milling and sieving of whole grain. A 25% (w/v) flour mash was liquefied with a thermostable 1,4--d-glucanohydrolase (EC 3.2.1.1) in the presence of 100 ppm Ca2+, at 80°C, pH 6.1–6.3, for 1 h. The liquefied mash was saccharified with 1,4--d-glucan glucohydrolase (EC 3.2.1.3) at 55°C, pH 5.5, for 2 h. An average of 75% of the flour was hydrolysed and about 82% of the hydrolysate was glucose. The feeding profile, which was based on a model with desired specific growth rate range of 0.18–0.23 h–1, biomass yield coefficient of 0.5 g g–1 and feed substrate concentration of 200 g L–1, was implemented manually using the millet flour hydrolysate in test experiments and glucose feed in control experiments. The fermentation off-gas was analyzed on-line by mass spectrometry for the calculation of carbon dioxide production rate, oxygen up-take rate and the respiratory quotient. Off-line determination of biomass, ethanol and glucose were done, respectively, by dry weight, gas chromatography and spectrophotometry. Cell mass concentrations of 49.9–51.9 g L–1 were achieved in all experiments within 27 h of which the last 15 h were in the fedbatch mode. The average biomass yields for the millet flour and glucose media were 0.48 and 0.49 g g–1, respectively. No significant differences were observed between the dough-leavening activities of the products of the test and the control media and a commercial preparation of instant active dry yeast. Millet flour hydrolysate was established to be a satisfactory low cost replacement for glucose in the production of baking quality yeast.Nomenclature
C
ox
Dissolved oxygen concentration (mg L–1)
-
CPR
Carbon dioxide production rate (mmol h–1)
-
C
s0
Glucose concentration in the feed (g L–1)
-
C
s
Substrate concentration in the fermenter (g L–1)
-
C
s.crit
Critical substrate concentration (g L–1)
-
E
Ethanol concentration (g L–1)
-
F
s
Substrate flow rate (g h–1)
-
i
Sample number (–)
-
K
e
Constant in Equation 6 (g L–1)
-
K
o
Constant in Equation 7 (mg L–1)
-
K
s
Constant in Equation 5 (g L–1)
-
m
Specific maintenance term (h–1)
-
OUR
Oxygen up-take rate (mmol h–1)
-
q
ox
Specific oxygen up-take rate (h–1)
-
q
ox.max
Maximum specific oxygen up-take rate (h–1)
-
q
p
Specific product formation rate (h–1)
-
q
s
Specific substrate up-take rate (g g–1 h–1)
-
q
s.max
Maximum specific substrate up-take rate (g g–1 h–1)
-
RQ
Respiratory quotient (–)
-
S
Total substrate in the fermenter at timet (g)
-
S
0
Substrate mass fraction in the feed (g g–1)
-
t
Fermentation time (h)
-
V
Instantaneous volume of the broth in the fermenter (L)
-
V
0
Starting volume in the fermenter (L)
-
V
si
Volume of samplei (L)
-
x
Biomass concentration in the fermenter (g L–1)
-
X
0
Total amount of initial biomass (g)
-
X
t
Total amount of biomass at timet (g)
-
Y
p/s
Product yield coefficient on substrate (–)
-
Y
x/e
Biomass yield coefficient on ethanol (–)
-
Y
x/s
Biomass yield coefficient on substrate (–)
Greek letters
Moles of carbon per mole of yeast (–)
-
Moles of hydrogen atom per mole of yeast (–)
-
Moles of oxygen atom per mole of yeast (–)
-
Moles of nitrogen atom per mole of yeast (–)
-
Specific growth rate (h–1)
- crit
Critical specific growth rate (h–1)
-
E
Specific ethanol up-take rate (h–1)
- max.E
Maximum specific ethanol up-take rate (h–1) 相似文献
12.
Metabolic scope and its utilization in relation to feeding and activity were measured in individual and grouped zebrafish (weight range, 430–551 mg) at 24° C by respirometry. Mean maximum metabolic rate, induced by swimming to exhaustion, Rmax(i), was 1223 (s.d. , 157) mg O2, kg?1 h?1 for individuals. Standard metabolic rate, Rs. was 364 mg O2 kg?1 h?1, as estimated by extrapolating to zero activity from measurements of unfed, spontaneously active individuals. Mean routine metabolic rate, Rrout, of individuals was 421 (s.d. , 58) mg O2, kg-1 h-1. The mean voluntary maximum metabolic rate, Rmax(v), following transfer of minimally exercised fish to the respirometer, was 1110 (s.d. , 83) mg O2 kg ?1 h?1 for groups of six fish, and was not significantly different from the value measured for individuals, 1066 (s.d. , 122) mg O2, kg?1 h?1. Grouped fish acclimated to the respirometer more slowly than individual fish and exhibited significantly higher Rrout, apparently a result of greater social interaction and activity in groups. Mean Rrout for groups was 560 (s.d. , 78) mg O2, kg?1 h?1. While groups of zebrafish fed a ration of 5% wet body weight day?1 exhibited consistently higher metabolic rates than fish fed rations of 2.5% wet body weight day?1 the high ration group still used only a maximum of 77% of the metabolic scope. Zebrafish of the size studied do not appear to demonstrate a high degree of conflict in utilization of metabolic scope by different respiratory components. The metabolic rates measured for zebrafish are among the highest yet measured for fish of similar size and at similar temperatures. 相似文献
13.
We examined a 6‐year record of automated chamber‐based soil CO2 efflux (Fs) and the underlying processes in relation to climate and canopy gas exchange at an AmeriFlux site in a seasonally drought‐stressed pine forest. Interannual variability of Fs was large (CV=17%) with a range of 427 g C m?2 yr?1 around a mean annual Fs of 811 g C m?2 yr?1. On average, 76% of the variation of daily mean Fs could be quantified using an empirical model with year‐specific basal respiration rate that was a linear function of tree basal area increment (BAI) and modulated by a common response to soil temperature and moisture. Interannual variability in Fs could be attributed almost equally to interannual variability in BAI (a proxy for above‐ground productivity) and interannual variability in soil climate. Seasonal total Fs was twice as sensitive to soil moisture variability during the summer months compared with temperature variability during the same period and almost insensitive to the natural range of interannual variability in spring temperatures. A strong seasonality in both root respiration (Rr) and heterotrophic respiration (Rh) was observed with the fraction attributed to Rr steadily increasing from 18% in mid‐March to 50% in early June through early July before dropping rapidly to 10% of Fs by mid‐August. The seasonal pattern in Rr (10‐day averages) was strongly linearly correlated with tree transpiration (r2=0.90, P<0.01) as measured using sap flux techniques and gross ecosystem productivity (GEP, r2=0.83, P<0.01) measured by the eddy‐covariance approach. Rr increased by 0.43 g C m?2 day?1 for every 1 g C m?2 day?1 increase in GEP. The strong linear correlation of Rr to seasonal changes in GEP and transpiration combined with longer‐term interannual variability in the base rate of Fs, as a linear function of BAI (r2=0.64, P=0.06), provides compelling justification for including canopy processes in future models of Fs. 相似文献
14.
Photosynthetic response of two shrubs to rainfall pulses in desert regions of northwestern China 总被引:1,自引:0,他引:1
Pulses of rainfall are particularly pivotal in controlling plant physiological processes in ecosystems controlled by limited
water, and the response of desert plants to rainfall is a key to understanding the responses of desert ecosystems to global
climatic change. We used a portable photosynthesis system to measure the responses of the diurnal course of photosynthesis,
light-response curves, and CO2-response curves of two desert shrubs (Nitraria sphaerocarpa Maxim. and Calligonum mongolicum Turcz) to a rainfall pulse in a desert-oasis ecotone in northwestern China. The photosynthetic parameters, light- and CO2-response curves differed significantly before and after the rainfall pulse. Their maximum net photosynthetic rate (P
N) values were 23.27 and 32.92 μmol(CO2) m−2 s−1 for N. sphaerocarpa and C. mongolicum, respectively, with corresponding maximum stomatal conductance (g
s) values of 0.47 and 0.39 mol(H2O) m−2 s−1. The P
N of N. sphaerocarpa after the rainfall was 1.65 to 1.75 times the value before rainfall, whereas those of C. mongolicum increased to approximately 2 times the prerainfall value, demonstrating the importance of the desert plants response by improving
their assimilation rate to precipitation patterns under a future climate. 相似文献
15.
Bead-bead collisions have been characterized using the velocity of the smallest turbulent eddies to calculate a turbulent collision severity (defined as the energy of collisions times their frequency), but a shear-based collision mechanism with a different dependence on the system variables is also applicable. This shearbased mechanism and the ratio of smallest eddy size to microcarrier diameter can explain the beneficial effects of both smaller diameter microcarriers and higher viscosity of the medium on the growth rate of bovine embryonic kidney cells. Death rates of these cells have also been measured at several levels of agitation. The decrease in apparent growth rate from increasing agitation is caused both by a higher rate of cell death as well as a lower intrinsic growth rate.List of Symbols
B
unspecified biological variable
-
d cm
bead diameter
-
d
i
cm
impeller diameter
-
e
error in estimate of power number
-
F
n
, F
s
(g·cm)/s2
normal and shear forces on a cell
- Fr
Froude number
-
g 980cm/s2
acceleration of gravity
-
k k–1
first order death rate constant
-
m g
mass of a bead
-
n s–1
impeller rotational rate
-
n
b
number of impeller blades
-
N
p
impeller power number
-
R
i
cm
impeller leading edge radius
-
TCS (g·cm2)/s3
turbulent collision severity
-
V cm3
reactor volume
-
v
br
cm/s rms
relative velocity between beads
-
v
e
cm/s
velocity in smallest eddies
-
X number of cells/cm3
cell population
Greek Symbols
volume fraction microcarriers
-
s–1
shear rate
-
cm2/s3
turbulent power dissipation rate
-
cm
size of smallest eddies
-
g/(cm·s)
dynamic viscosity
-
h–1
apparent growth rate of cells
-
0 h–1
intrinsic growth rate of cells in absence of death
-
v cm2/s
kinematic viscosity
-
b
g/cm3
bead density
-
f
g/cm3
fluid density
-
g/(cm·s2)
shear stress 相似文献
16.
J. Lucas A. Schouman L. Lyphout X. Cousin C. Lefrancois 《Journal of fish biology》2014,84(4):1171-1178
The relationship between body mass (M) and metabolic rate was investigated through the assessment of active (RA) and standard (RS) metabolic rate at different life stages in zebrafish Danio rerio (5 day‐old larvae, 2 month‐old juveniles and 6 month‐old adults). Scaling exponents and constants were assessed for standard (RS = 0·273M0·965 in mgO2 g?1 h?1) and active metabolic rate (RA = 0·799M0·926 in mgO2 g?1 h?1). These data provide the basis for further experiments regarding the effects of environmental factors on aerobic metabolism throughout the life cycle of this species. 相似文献
17.
An integrated field and laboratory study was conducted to quantify the effect of environmental determinants on the activity of sulfate reducers in a freshwater aquifer contaminated with petroleum hydrocarbons (PHC). Within the contaminated zone, PHC-supported in␣situ sulfate reduction rates varied from 11.58±3.12 to 636±53 nmol cm−3 d−1 and a linear increase (R
2=0.98) in reduction rate was observed with increasing in situ sulfate concentrations suggesting sulfate limitation. Half-saturation concentration (K
s) for sulfate reduction coupled to PHC mineralization was determined for the first time. At two different sites within the␣aquifer, maximum sulfate reduction rate under␣non-limiting conditions (R
max) was 5,000 nmol cm−3 d−1, whereas the retrieved K
s values were 3.5 and 7.5 mM, respectively. The K
s values are the highest ever reported from a natural environment. Furthermore, the K
s values were significantly higher than in situ sulfate concentrations confirming sulfate limited growth. On addition of lactate and formate, sulfate reduction rate increased indicating that reactivity and bioavailability of organic substrate may also have played a role in rate inhibition in certain parts of the aquifer. Experiments with sulfide amendments show statistically minor decrease in sulfate reduction rates on addition of sulfide and analogous increase in sulfide toxicity with increasing sulfide concentrations (0.5–10 mM) was not apparent. 相似文献
18.
Tropical forests are the largest contributors to global emissions of carbon dioxide (CO2) to the atmosphere via soil respiration (Rs). As such, identifying the main controls on Rs in tropical forests is essential for accurately projecting the consequences of ongoing and future global environmental changes to the global C cycle. We measured hourly Rs in a secondary tropical moist forest in Puerto Rico over a 3‐year period to (a) quantify the magnitude of Rs and (b) identify the role of climatic, substrate, and nutrient controls on the seasonality of Rs. Across 3 years of measurements, mean Rs was 7.16 ± 0.02 μmol CO2 m‐2 s‐1 (or 2,710 g C m‐2 year‐1) and showed significant seasonal variation. Despite small month‐to‐month variation in temperature (~4°C), we found significant positive relationships between daily and monthly Rs with both air and soil temperature, highlighting the importance of temperature as a driver of Rs even in warm ecosystems, such as tropical forests. We also found a significant parabolic relationship between mean daily volumetric soil moisture and mean daily Rs, with an optimal moisture value of 0.34 m3 m‐3. Given the relatively consistent climate at this site, the large range in mean monthly Rs (~7 μmol CO2 m‐2 s‐1) was surprising and suggests that even small changes in climate can have large implications for ecosystem respiration. The strong positive relationship of Rs with temperature at monthly timescales particularly stands out, as moisture is usually considered a stronger control of Rs in tropical forests that already experience warm temperatures year‐round. Moreover, our results revealed the strong seasonality of Rs in tropical moist forests, which given its high magnitude, can represent a significant contribution to the seasonal patterns of atmospheric (CO2) globally. 相似文献
19.
Fanny Houlbrèque Eric Tambutté Christine Ferrier-Pagès 《Journal of experimental marine biology and ecology》2003,296(2):145-166
This work investigated the effect of light and feeding on tissue composition as well as on rates of photosynthesis and calcification in the zooxanthellae (zoox) scleractinian coral, Stylophora pistillata. Microcolonies were maintained at three different light levels (80, 200, 300 μmol m−2 s−1) and subjected to two feeding regimes (starved and fed) over 9 weeks. Corals were fed both natural plankton and Artemia salina nauplii four times a weeks and samplings were made after 2, 5, and 9 weeks. Results confirmed that feeding enhances coral growth rate and increases both the dark and light calcification rates. These rates were 50-75% higher in fed corals (FC; 60±20 and 200±40 nmol Ca2+ cm−2 h−1 for dark and light calcification, respectively) compared to control corals (CC; 30±9 and 124±23 nmol Ca2+ cm−2 h−1). The dark calcification rates, however, were four times lower than the rates of light calcification (independent of trophic status). After 5 weeks, chlorophyll a (chl-a) concentrations were four to seven times higher in fed corals (7-21 μg cm−2) than in control corals (2-5 μg cm−2). The amount of protein was also significantly higher in fed corals (2.11-2.50 mg cm−2) than in control corals (1.08-1.52 mg cm−2). Rates of photosynthesis in fed corals were 2-10 times higher (1.24±0.75 μmol O2 h−1 cm−2) than those measured in control corals (0.20±0.08 μmol O2 h−1 cm−2). 相似文献
20.
Summary Comparisons of net CO2 assimilation, dark respiration, leaf resistance, and leaf water potential were made between diploid and polyploid races of Viola adunca from the Cypress Hills, Alberta, Canada. The mean maximum net CO2 assimilation rate, at 20 C and 500 E m-2 s-1 (phAR) was 26 mg CO2 g-1 h-1 (12 mg CO2 dm-2 h-1) for polyploids, and 23 mg CO2 g-1 h-1 (11 mg dm-2 h-1) for diploids. The difference is not statistically significant. Net CO2 assimilation rates at low (0° C) and high (40° C) temperatures were virtually the same for diploids and polyploids. There were no statistically significant differences between the chromosome races in light compensation or light saturation over the 0° to 40° C temperature range studied. Average dark respiration of the polyploid race at 20 C was 2.2 mg CO2 g-1 h-1 (1.0 mg CO2 dm-2 h-1) compared with 2.0 mg CO2 g-1 h-1 (0.95 mg CO2 dm-2 h-1) for the diploid race. The mean maximum leaf water potential of well watered plants was-7.9 bars for both ploidy levels. Minimum leaf resistance was ca. 3.6 s cm-1 for both ploidy levels. Maximum net CO2 assimilation rates in both ploidy levels occurred at-9 bars leaf water potential. Based upon the plant responses studied, there are no differences between chromosome races collected from the same general area, and the polyploids do not respond more favorably to extremes of temperature and water potential. Ploidy per se does not affect the response of Viola adunca to its environment in this particular case. 相似文献