Relationships between denitrification rate and determinant soil properties under barley

1993 ◽  
Vol 73 (4) ◽  
pp. 567-578 ◽  
Author(s):  
D. W. Bergstrom ◽  
E. G. Beauchamp
Keyword(s):  
Enzyme Activity ◽  
Moisture Content ◽  
Soil Properties ◽  
Respiration Rate ◽  
Denitrification Rate ◽  
Bulk Soil ◽  
Small Scale ◽  
Mean Values ◽  
Acetylene Blockage ◽  
A Site

To better understand environmental regulation of denitrification, we examined relationships between denitrification rate and six determinant soil properties: moisture content, air-filled porosity, NO3− content, respiration rate, mineralizable-C concentration and denitrifying enzyme activity (DEA). Soil cores were collected on 27 sampling dates over a growing season at a site seeded to barley (Hordeum vulgare). Denitrification rate was measured using a static core technique and acetylene blockage. Moisture content and air-filled porosity and, to a lesser extent, mineralizable-C concentration and respiration rate were more strongly related to denitrification rate than was DEA. Denitrification rate was unrelated to NO3− content. On most sampling dates, mean denitrification rate increased substantially only below an air-filled porosity of 0.3. Moreover, the distribution of individual measurements of denitrification rate was less skewed at lower air-filled porosities. Approximately 60% of variation in mean values of denitrification rate for each sampling date could be accounted for by measurements of bulk soil properties, of which moisture content and air-filled porosity were most important. Measurements of bulk soil properties did not account for nil values of denitrification rate at low air-filled porosities or for small-scale spatial variability. Such measurements were better indicators of temporal variation — that is, when denitrification occurred — than of actual rates. Key words: Denitrification, air-filled porosity, denitrifying enzyme activity

scholarly journals Hot or not? connecting rhizosphere hotspots to total soil respiration

2021 ◽  
Author(s):  
Joscha N. Becker ◽  
Maire Holz
Keyword(s):  
Enzyme Activity ◽  
Soil Respiration ◽  
Root Biomass ◽  
Root Exudation ◽  
Bulk Soil ◽  
Small Scale ◽  
Individual Plant ◽  
Imaging Data ◽  
Total Soil ◽  
Total Soil Respiration

Abstract Aims Soil organic carbon (C) efflux is tightly linked to the rhizosphere, where soil microorganisms rapidly decompose organic compounds released from roots. Recently, imaging approaches have greatly improved our understanding of small-scale C-turnover heterogeneity and promoted the term ‘rhizosphere hotspots’ for highly active areas. However, despite often assumed, the effect of these hotspots on total soil C balances is still unknown. We aim to bridge this gap by correlating rhizosphere imaging data to soil respiration on individual plant scale. Methods We grew 17 maize (Zea mays L.) plants in rhizoboxes filled with sandy arable soil. After four weeks, the plants were labelled with 14CO2 and root exudation was visualized and quantified by 14C-imaging one day after labeling. The evolved CO2 was trapped in NaOH and 14CO2 as well as total CO2 was quantified before and after labelling. Enzyme activity (β-glucosidase) was quantified by soil zymography. Results Bulk soil β-glucosidase activitiy negatively correlated to total CO2 efflux, and was the most important predictor (R2 = 0.55). Total and rhizosphere specific 14C-activity were solely correlated to 14CO2 efflux (r = 0.51, r = 0.58). A combination of bulk soil β-glucosidase activity, rhizosphere-14C activity and root biomass, explained about 75% of variance in CO2 efflux. Conclusions This indicates that root exudation and enzyme-activity hotspots are suitable predictors for total soil respiration, particularly when combined with root biomass to account for three-dimensional variation, and that hotspots on the rhizosphere scale are directly linked to larger scale C balances.

Applying the Method of Lagrange Multipliers to Derive an Estimator for Unsampled Soil Properties

2014 ◽  
Vol 11 (1) ◽  
pp. 15
Author(s):  
Set Foong Ng ◽  
Pei Eng Ch’ng ◽  
Yee Ming Chew ◽  
Kok Shien Ng
Keyword(s):  
Soil Properties ◽  
Lagrange Multipliers ◽  
Unbiased Estimator ◽  
Soil Property ◽  
Minimum Variance ◽  
Distance Method ◽  
True Value ◽  
A Site ◽  
Method Of Lagrange Multipliers ◽  
Inverse Distance

Soil properties are very crucial for civil engineers to differentiate one type of soil from another and to predict its mechanical behavior. However, it is not practical to measure soil properties at all the locations at a site. In this paper, an estimator is derived to estimate the unknown values for soil properties from locations where soil samples were not collected. The estimator is obtained by combining the concept of the ‘Inverse Distance Method’ into the technique of ‘Kriging’. The method of Lagrange Multipliers is applied in this paper. It is shown that the estimator derived in this paper is an unbiased estimator. The partiality of the estimator with respect to the true value is zero. Hence, the estimated value will be equal to the true value of the soil property. It is also shown that the variance between the estimator and the soil property is minimised. Hence, the distribution of this unbiased estimator with minimum variance spreads the least from the true value. With this characteristic of minimum variance unbiased estimator, a high accuracy estimation of soil property could be obtained.

Type of Slope Failure Identified from Pore Water Pressure and Moisture Content Measurements

2015 ◽  
Vol 744-746 ◽  
pp. 690-694
Author(s):  
Muhammad Rehan Hakro ◽  
Indra Sati Hamonangan Harahap
Keyword(s):  
Moisture Content ◽  
Pore Pressure ◽  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Failure Process ◽  
Small Scale ◽  
Content Increase ◽  
Sudden Increase ◽  
Model Slope

Rainfall-induced landslides occur in many parts of the world and causing a lot of the damages. For effective prediction of rainfall-induced landslides the comprehensive understanding of the failure process is necessary. Under different soil and hydrological conditions experiments were conducted to investigate and clarify the mechanism of slope failure. The failure in model slope was induced by sprinkling the rainfall on slope composed of sandy soil in small flume. Series of tests were conducted in small scale flume to better understand the failure process in sandy slopes. The moisture content was measured with advanced Imko TDR (Time Domain Reflectrometry) moisture sensors in addition to measurements of pore pressure with piezometers. The moisture content increase rapidly to reach the maximum possible water content in case of higher intensity of rainfall, and higher intensity of the rainfall causes higher erosion as compared to smaller intensity of the rainfall. The controlling factor for rainfall-induced flowslides was density of the slope, rather than intensity of the rainfall and during the flowslide the sudden increase in pore pressure was observed. Higher pore pressure was observed at the toe of the slope as compared to upper part of the slope.

Vegetation alters how soil properties and climate influence microbial activity and functional diversity in rhizosphere and bulk soil along an elevation gradient

2021 ◽  
pp. 108485
Author(s):  
Daniel Hernández-Cáceres ◽  
Alexia Stokes ◽  
Guillermo Angeles-Alvarez ◽  
Josiane Abadie ◽  
Fabien Anthelme ◽  
...  
Keyword(s):  
Soil Properties ◽  
Microbial Activity ◽  
Functional Diversity ◽  
Elevation Gradient ◽  
Bulk Soil

scholarly journals The climatic mass balance of Svalbard glaciers: a 10-year simulation with a coupled atmosphere–glacier mass balance model

2016 ◽  
Vol 10 (3) ◽  
pp. 1089-1104 ◽  
Author(s):  
Kjetil S. Aas ◽  
Thorben Dunse ◽  
Emily Collier ◽  
Thomas V. Schuler ◽  
Terje K. Berntsen ◽  
...  
Keyword(s):  
Mass Balance ◽  
Detailed Comparison ◽  
Balance Model ◽  
Climate Projections ◽  
Glacier Mass Balance ◽  
Grid Spacing ◽  
Satellite Measurements ◽  
Mean Values ◽  
Ice Cap ◽  
A Site

Abstract. In this study we simulate the climatic mass balance of Svalbard glaciers with a coupled atmosphere–glacier model with 3 km grid spacing, from September 2003 to September 2013. We find a mean specific net mass balance of −257 mm w.e. yr−1, corresponding to a mean annual mass loss of about 8.7 Gt, with large interannual variability. Our results are compared with a comprehensive set of mass balance, meteorological, and satellite measurements. Model temperature biases of 0.19 and −1.9 °C are found at two glacier automatic weather station sites. Simulated climatic mass balance is mostly within about 100 mm w.e. yr−1 of stake measurements, and simulated winter accumulation at the Austfonna ice cap shows mean absolute errors of 47 and 67 mm w.e. yr−1 when compared to radar-derived values for the selected years 2004 and 2006. Comparison of modeled surface height changes from 2003 to 2008, and satellite altimetry reveals good agreement in both mean values and regional differences. The largest deviations from observations are found for winter accumulation at Hansbreen (up to around 1000 mm w.e. yr−1), a site where sub-grid topography and wind redistribution of snow are important factors. Comparison with simulations using 9 km grid spacing reveal considerable differences on regional and local scales. In addition, 3 km grid spacing allows for a much more detailed comparison with observations than what is possible with 9 km grid spacing. Further decreasing the grid spacing to 1 km appears to be less significant, although in general precipitation amounts increase with resolution. Altogether, the model compares well with observations and offers possibilities for studying glacier climatic mass balance on Svalbard both historically as well as based on climate projections.

The infestibility of stored paddy by Sitophilus sasakii (Tak.) and Rhyzopertha dominica (F.).

1960 ◽  
Vol 51 (3) ◽  
pp. 599-630 ◽  
Author(s):  
Michael H. Breese
Keyword(s):  
Moisture Content ◽  
Rhyzopertha Dominica ◽  
Small Scale ◽  
British Guiana ◽  
Rapid Multiplication

Indications of the type of paddy grain most commonly infested by Sitophilus sasakii (Tak.) and Rhyzopertha dominica (F.) have been obtained from the examination of infested samples of paddy grown in Trinidad, W.I., and in British Guiana.Small-scale experiments with sound mature paddy have shown that S.sasakii is unable to feed and breed in a grain with an intact husk, even when the moisture content is high. It is also probable that R. dominica finds it extremely difficult to attack and infest such grains.The rapid multiplication of S. sasakii in paddy is dependent on there being a high proportion of grains with badly damaged husks. Infestation can occur in grains with a slight separation of the lemma and palea, or with slightly split husks, but the adult that develops is often unable to emerge from such grains.

Variation in small-scale spatial heterogeneity of soil properties and vegetation with different land use in semiarid grassland ecosystem

2008 ◽  
Vol 310 (1-2) ◽  
pp. 103-112 ◽  
Author(s):  
Zhiyong Zhou ◽  
Osbert Jianxin Sun ◽  
Zhongkui Luo ◽  
Hongmei Jin ◽  
Quansheng Chen ◽  
...  
Keyword(s):  
Land Use ◽  
Spatial Heterogeneity ◽  
Soil Properties ◽  
Small Scale ◽  
Grassland Ecosystem ◽  
Semiarid Grassland

scholarly journals Ant nests as a microbial hot spots in a long-term heavy metal-contaminated soils

2021 ◽  
Author(s):  
Beata Klimek ◽  
Hanna Poliwka-Modliborek ◽  
Irena M. Grześ
Keyword(s):  
Microbial Biomass ◽  
Microbial Activity ◽  
Respiration Rate ◽  
Metal Content ◽  
Soil Microbial Activity ◽  
Bulk Soil ◽  
Lasius Niger ◽  
Soil Microbial ◽  
Ant Nests

AbstractInteractions between soil fauna and soil microorganisms are not fully recognized, especially in extreme environments, such as long-term metal-polluted soils. The purpose of the study was to assess how the presence of Lasius niger ants affected soil microbial characteristics in a long-term metal-polluted area (Upper Silesia in Poland). Paired soil samples were taken from bulk soil and from ant nests and analysed for a range of soil physicochemical properties, including metal content (zinc, cadmium, and lead). Microbial analysis included soil microbial activity (soil respiration rate), microbial biomass (substrate-induced respiration rate), and bacteria catabolic properties (Biolog® ECO plates). Soil collected from ant nests was drier and was characterized by a lower content of organic matter, carbon and nitrogen contents, and also lower metal content than bulk soil. Soil microbial respiration rate was positively related to soil pH (p = 0.01) and negatively to water-soluble metal content, integrated into TIws index (p = 0.01). Soil microbial biomass was negatively related to TIws index (p = 0.04). Neither soil microbial activity and biomass nor bacteria catabolic activity and diversity indices differed between bulk soil and ant nests. Taken together, ant activity reduced soil contamination by metals in a microscale which support microbial community activity and biomass but did not affect Biolog® culturable bacteria.

scholarly journals Produksi Enzim Selulase olehAspergillus niger pada Ampas Sagu

2015 ◽  
Vol 16 (1) ◽  
pp. 1 ◽  
Author(s):  
Nora Idiawati ◽  
Elliska Murni Harfinda ◽  
Lucy Arianie
Keyword(s):  
Enzyme Activity ◽  
Aspergillus Niger ◽  
Moisture Content ◽  
Cellulase Enzymes ◽  
Fermentation Time ◽  
Cellulase Enzyme ◽  
Sago Waste ◽  
Solid Fermentation

Production of cellulase by Aspergillus niger was carried out by growing the cultureson sago waste. Sago waste containscellulose that has not been used optimally. Cellulose is a polysaccharide consisting of glucose monomers linked by β-1,4-glycosides bonds. Glycoside bonds in cellulose can be enzymatically hydrolyzed into glucose with cellulase enzymes. Solid fermentation used to produce cellulase on sago waste as substrate was influenced by pH (3 to 6), moisture content(40% to 85%), and fermentation time (4 to 10 days). Products of the cellulase enzyme activity was measured by phenolsulfuricacid method. The results showed that the highest cellulase enzyme activity was 0.172 U/mL obtained at 85%moisture content, pH 5, and 8 days of fermentation time.

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