Comparison of static and dynamic closed chambers for measurement of soil respiration under field conditions

1992 ◽  
Vol 72 (4) ◽  
pp. 605-609 ◽  
Author(s):  
P. Rochette ◽  
E. G. Gregorich ◽  
R. L. Desjardins
Keyword(s):  
Soil Respiration ◽  
Sandy Loam ◽  
Flux Measurement ◽  
Organic Soil ◽  
Exponential Model ◽  
Field Conditions ◽  
Parameter Estimates ◽  
Static Chamber ◽  
The Difference ◽  
Negative Exponential

The objective of this study was to compare the dynamic closed and static chamber techniques for the measurement of soil respiration under field conditions. The static chamber method consistently produced lower soil respiration values than did the dynamic closed system and the difference was larger at higher CO2 fluxes. A negative exponential model describes the relation between CO2 fluxes measured by both techniques. A good fit was obtained for measurements on a sandy loam soil (R2 = 0.61) and an organic soil (R2 = 0.74) but parameter estimates were different for each soil. Key words: Carbon dioxide, enclosure, gas flux measurement

Effects of fenvalerate and permethrin on soil arthropods and on residues in and decomposition of barley straw

1994 ◽  
Vol 3 (2) ◽  
pp. 213-223 ◽  
Author(s):  
Erja Huusela-Veistola ◽  
Sirpa Kurppa ◽  
Juha-Matti Pihlava
Keyword(s):  
Sandy Soil ◽  
Decomposition Rate ◽  
Field Experiments ◽  
Sandy Loam ◽  
Organic Soil ◽  
Barley Straw ◽  
Soil Arthropods ◽  
Soil Animals ◽  
The Difference ◽  
And Control

The effects of two pyrethroids, fenvalerate and permethrin, were studied in field experiments on two soil types: organic soil and sandy loam. The objectives were to determine 1) the persistence of fenvalerate and permethrin in straw, 2) the effects of the pyrethroids on epigeal Arachnida and Collembola, and other soil animals and 3) the effects of the pyrethroids on the decomposition rate of straw. The residues of fenvalerate and permethrin in straw approximately 2 months after application varied between 0.1 to above 5 mg/kg straw in 1986, 1988 and 1989, but was less than 0.5 mg/kg straw at harvest in 1991. No pesticide residues were found in straw samples taken in the following summer in the 1991 experiment. The decomposition rate of straw did not differ between permethrin and fenvalerate- treated plots and control plots. The rate of decomposition was slightly higher in sandy soil than in organic soil, but the same on tilled and non-tilled plots. Fenvalerate and permethrin affected the numbers of epigeal Arachnida and Collembola in the field. Araneae were more numerous in pitfall samples taken from control plots than in insecticide-treated plots immediately after treatment. In organic soil the difference was marginally significant after harvest. The abundance of Acarina in pitfalls was significantly lower in insecticide-treated plots than in control plots. In the sandy soil experiment, less Collembola occurred in pitfalls of fenvalerate plots than in permethrin or control plots. There were no differences in any of the groups of soil animals in soil cores extracted with dry funnels between the treatments.

Wolbachia and Cytoplasmic Incompatibility in the CaliforniaCulex pipiensMosquito Species Complex: Parameter Estimates and Infection Dynamics in Natural Populations

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 2029-2038 ◽  
Author(s):  
Jason L Rasgon ◽  
Thomas W Scott
Keyword(s):  
Species Complex ◽  
Cytoplasmic Incompatibility ◽  
Natural Populations ◽  
Wolbachia Infection ◽  
Field Conditions ◽  
Parameter Estimates ◽  
Infection Prevalence ◽  
Infection Frequency ◽  
Specific Pcr ◽  
Vector Borne

AbstractBefore maternally inherited bacterial symbionts like Wolbachia, which cause cytoplasmic incompatibility (CI; reduced hatch rate) when infected males mate with uninfected females, can be used in a program to control vector-borne diseases it is essential to understand their dynamics of infection in natural arthropod vector populations. Our study had four goals: (1) quantify the number of Wolbachia strains circulating in the California Culex pipiens species complex, (2) investigate Wolbachia infection frequencies and distribution in natural California populations, (3) estimate the parameters that govern Wolbachia spread among Cx. pipiens under laboratory and field conditions, and (4) use these values to estimate equilibrium levels and compare predicted infection prevalence levels to those observed in nature. Strain-specific PCR, wsp gene sequencing, and crossing experiments indicated that a single Wolbachia strain infects Californian Cx. pipiens. Infection frequency was near or at fixation in all populations sampled for 2 years along a >1000-km north-south transect. The combined statewide infection frequency was 99.4%. Incompatible crosses were 100% sterile under laboratory and field conditions. Sterility decreased negligibly with male age in the laboratory. Infection had no significant effect on female fecundity under laboratory or field conditions. Vertical transmission was >99% in the laboratory and ∼98.6% in the field. Using field data, models predicted that Wolbachia will spread to fixation if infection exceeds an unstable equilibrium point above 1.4%. Our estimates accurately predicted infection frequencies in natural populations. If certain technical hurdles can be overcome, our data indicate that Wolbachia can invade vector populations as part of an applied transgenic strategy for vector-borne disease reduction.

Longitudinal changes in the kinetic response to heavy-intensity exercise in children

2004 ◽  
Vol 97 (2) ◽  
pp. 460-466 ◽  
Author(s):  
Samantha G. Fawkner ◽  
Neil Armstrong
Keyword(s):  
Slow Component ◽  
Phase 1 ◽  
Exponential Model ◽  
Cycle Ergometer ◽  
Primary Component ◽  
Total Change ◽  
Exercise Tests ◽  
Longitudinal Changes ◽  
Dependent Change ◽  
The Difference

The purpose of this study was to investigate longitudinal changes with age in the kinetic response to cycling at heavy-intensity exercise in boys and girls. Twenty-two prepubertal children (13 male, 9 female) carried out a series of exercise tests on two test occasions with a 2-yr interval. On each test occasion, the subject completed multiple transitions from baseline to 40% of the difference between their previously determined V-slope and peak O2 uptake (V̇o2) for 9 min on an electronically braked cycle ergometer. Each subject's breath-by-breath responses were interpolated to 1-s intervals, time aligned, and averaged. The data after phase 1 were fit with 1) a double exponential model and 2) a single exponential model within a fitting window that was previously identified to exclude the slow component. There were no significant differences in the parameters of the primary component between each model. Subsequent analysis was carried out using model 2. The V̇o2 slow component was computed as the difference between the amplitude of the primary component and the end-exercise V̇o2 and was expressed as the percent contribution to the total change in V̇o2. Over the 2-yr period, the primary time constant (boys 16.8 ± 5.3 and 21.7 ± 5.3 s, girls 21.1 ± 8.1 and 26.4 ± 8.4 s, first and second occasion, respectively) and the relative amplitude of the slow component (boys 9.4 ± 4.6 and 13.8 ± 5.3%, girls 10.3 ± 2.4 and 15.5 ± 2.8%, first and second occasion, respectively) significantly increased with no sex differences. The data demonstrate that children do display a slow-component response to exercise and are consistent with an age-dependent change in the muscles' potential for O2 utilization.

Applicability of an extant batch respirometric assay in describing dynamics of ammonia and nitrite oxidation in a nitrifying bioreactor

2005 ◽  
Vol 52 (10-11) ◽  
pp. 503-508 ◽  
Author(s):  
K. Chandran ◽  
Z. Hu ◽  
B.F. Smets
Keyword(s):  
Kinetic Parameter ◽  
Sensitivity Analyses ◽  
Continuous Reactor ◽  
Parameter Estimates ◽  
Additional Parameter ◽  
Reactor Performance ◽  
Estimation Techniques ◽  
The Difference ◽  
The Impact ◽  
Best Fit

Several techniques have been proposed for biokinetic estimation of nitrification. Recently, an extant respirometric assay has been presented that yields kinetic parameters for both nitrification steps with minimal physiological change to the microorganisms during the assay. Herein, the ability of biokinetic parameter estimates from the extant respirometric assay to adequately describe concurrently obtained NH4+-N and NO2−-N substrate depletion profiles is evaluated. Based on our results, in general, the substrate depletion profiles resulted in a higher estimate of the maximum specific growth rate coefficient, μmax for both NH4+-N to NO2−-N oxidation and NO2−-N to NO3−-N oxidation compared to estimates from the extant respirograms. The trends in the kinetic parameter estimates from the different biokinetic estimation techniques are paralleled in the nature of substrate depletion profiles obtained from best-fit parameters. Based on a visual inspection, in general, best-fit parameters from optimally designed complete respirograms provided a better description of the substrate depletion profiles than estimates from isolated respirograms. Nevertheless, the sum of the squared errors for the best-fit respirometry based parameters was outside the 95% joint confidence interval computed for the best-fit substrate depletion based parameters. Notwithstanding the difference in kinetic parameter estimates determined in this study, the different biokinetic estimation techniques still are close to estimates reported in literature. Additional parameter identifiability and sensitivity analysis of parameters from substrate depletion assays revealed high precision of parameters and high parameter correlation. Although biokinetic estimation via automated extant respirometry is far more facile than via manual substrate depletion measurements, additional sensitivity analyses are needed to test the impact of differences in the resulting parameter values on continuous reactor performance.

scholarly journals Modelling of Soil Respiration in Hungary

2006 ◽  
Vol 55 (1) ◽  
pp. 59-68 ◽  
Author(s):  
Ferenc Ács ◽  
H. Breuer
Keyword(s):  
Soil Respiration ◽  
Water Balance ◽  
Air Temperature ◽  
Sandy Loam ◽  
Growing Season ◽  
Biogeochemical Model ◽  
Clay Loam ◽  
Water Balance Components ◽  
Linear Relationships ◽  
Time Periods

The climatology of soil respiration in Hungary is presented. Soil respiration is estimated by a Thornthwaite-based biogeochemical model using soil hydrophysical data and climatological fields of precipitation and air temperature. Soil respiration fields are analyzed for different soil textures (sand, sandy loam, loam, clay loam and clay) and time periods (year, growing season and months).  Strong linear relationships were found between soil respiration and the actual evapotranspiration for annual and growing season time periods. In winter months soil respiration is well correlated with air temperature, while in summer months there is a quite variable relationship with water balance components. The strength of linear relationship between soil respiration and climatic variables is much better for coarser than for finer soil texture.

scholarly journals Time since death and decay rate constants of Norway spruce and European larch deadwood in subalpine forests determined using dendrochronology and radiocarbon dating

2015 ◽  
Vol 12 (17) ◽  
pp. 14797-14832 ◽  
Author(s):  
M. Petrillo ◽  
P. Cherubini ◽  
G. Fravolini ◽  
J. Ascher ◽  
M. Schärer ◽  
...  
Keyword(s):  
Decay Rate ◽  
Tree Rings ◽  
Rate Constants ◽  
Radiocarbon Dating ◽  
Woody Debris ◽  
Visual Assessment ◽  
Exponential Model ◽  
Alpine Valley ◽  
Species Specific ◽  
Negative Exponential

Abstract. Due to the large size and highly heterogeneous spatial distribution of deadwood, the time scales involved in the coarse woody debris (CWD) decay of Picea abies (L.) Karst. and Larix decidua Mill. in Alpine forests have been poorly investigated and are largely unknown. We investigated the CWD decay dynamics in an Alpine valley in Italy using the five-decay class system commonly employed for forest surveys, based on a macromorphological and visual assessment. For the decay classes 1 to 3, most of the dendrochronological samples were cross-dated to assess the time that had elapsed since tree death, but for decay classes 4 and 5 (poorly preserved tree rings) and some others not having enough tree rings, radiocarbon dating was used. In addition, density, cellulose and lignin data were measured for the dated CWD. The decay rate constants for spruce and larch were estimated on the basis of the density loss using a single negative exponential model. In the decay classes 1 to 3, the ages of the CWD were similar varying between 1 and 54 years for spruce and 3 and 40 years for larch with no significant differences between the classes; classes 1–3 are therefore not indicative for deadwood age. We found, however, distinct tree species-specific differences in decay classes 4 and 5, with larch CWD reaching an average age of 210 years in class 5 and spruce only 77 years. The mean CWD rate constants were 0.012 to 0.018 yr−1 for spruce and 0.005 to 0.012 yr−1 for larch. Cellulose and lignin time trends half-lives (using a multiple-exponential model) could be derived on the basis of the ages of the CWD. The half-lives for cellulose were 21 yr for spruce and 50 yr for larch. The half-life of lignin is considerably higher and may be more than 100 years in larch CWD.

Estimating a model of sportfishing trip expenditures using a quasi-maximum likelihood approach

2016 ◽  
Vol 23 (2) ◽  
pp. 448-459 ◽  
Author(s):  
Richard T. Melstrom
Keyword(s):  
Maximum Likelihood ◽  
Exponential Model ◽  
Parameter Estimates ◽  
Maximum Likelihood Approach ◽  
Likelihood Approach ◽  
Quasi Maximum Likelihood ◽  
Species Preferences ◽  
The Impact ◽  
Consistent Parameter

This article presents an exponential model of tourist expenditures estimated by a quasi-maximum likelihood (QML) technique. The advantage of this approach is that, unlike conventional OLS and Tobit estimators, it produces consistent parameter estimates under conditions of a corner solution at zero and heteroscedasticity. An application to sportfishing evaluates the role of socioeconomic demographics and species preferences on trip spending. The bias from an inappropriate estimator is illustrated by comparing the results from QML and OLS estimation, which shows that OLS significantly overstates the impact of trip duration on trip expenditures compared with the QML estimator. Both sets of estimates imply that trout and bass anglers spend significantly more on their fishing trips compared with other anglers.

Methodological errors in radioisotope flux measurements

1988 ◽  
Vol 255 (5) ◽  
pp. G696-G699
Author(s):  
R. W. Egnor ◽  
S. G. Vaccarezza ◽  
A. N. Charney
Keyword(s):  
Specific Activity ◽  
Flux Measurement ◽  
Sampling Interval ◽  
Flux Chamber ◽  
Sources Of Error ◽  
Counting Time ◽  
Flux Measurements ◽  
The Absolute ◽  
The Difference ◽  
Serial Samples

We examined several sources of error in isotopic flux measurements in a commonly used experimental model: the study of 22Na and 36Cl fluxes across rat ileal tissue mounted in the Ussing flux chamber. The experiment revealed three important sources of error: the absolute counts per minute, the difference in counts per minute between serial samples, and averaging of serial samples. By computer manipulation, we then applied hypothetical changes in the experimental protocol to generalize these findings and assess the effect and interaction of the absolute counts per minute, the sampling interval, and the counting time on the magnitude of the error. We found that the error of a flux measurement will vary inversely with the counting time and the difference between the consecutive sample counts per minute used in the flux calculations and will vary directly with the absolute counts per minute of each sample. Alteration of the "hot" side specific activity, the surface area of the tissue across which flux is measured and the sample volume have a smaller impact on measurement error. Experimental protocols should be designed with these methodological considerations in mind to minimize the error inherent in measuring isotope flux.

scholarly journals Forest Soil Respirations are More Sensitive to Nighttime Temperature Change in Eastern China

2018 ◽  
Vol 47 (1) ◽  
pp. 249-254
Author(s):  
Zhaoyong SHI ◽  
Ke LI ◽  
Yongming WANG ◽  
Bede S. MICKAN ◽  
Weikang YUAN ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Soil Temperature ◽  
Temperature Change ◽  
Global Climate ◽  
Eastern China ◽  
Growing Season ◽  
Mean Value ◽  
Apparent Temperature ◽  
Effect Of Temperature ◽  
The Difference

Soil respiration is one of the main fluxes in the global carbon cycle. The effect of temperature on soil respiration is well understood. The response of soil respiration to temperature warming is called apparent temperature sensitivity (Q10) of soil respiration, which is an important parameter in modeling soil CO2 effluxes under global climate warming. The difference of Q10 between daytime and nighttime was hardly reported although attentions are attracted by the differences of temperature change and its effects on vegetation productivity. In this study, we investigated the Q10 of soil respiration in daytime and nighttime by modeling empirical functions based on the in situ measurement of soil respiration and temperature in temperate and subtropical forests of eastern China. Our results showed that the Q10 of soil respiration is higher in nighttime with the mean value of 2.74 and 2.35 than daytime with the average of 2.49 and 2.18 in all measured months and growing season, respectively. Moreover, the explanatory rate of soil temperature to soil respiration in nighttime is also higher than in daytime in each site in both all measured and growing seasons. The Q10 and explanatory rate of soil temperature to soil respiration in nighttime is 1.08 and 1.15 times in daytime in growing season. These findings indicate that soil respiration has a bigger sensitivity to temperature in nighttime than daytime. The change of soil temperature explains more variation of soil respiration in nighttime than daytime.

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