scholarly journals Improvement of predicting ecosystem productivity by modifying carbon–water–nitrogen coupling processes in a temperate grassland

2020 ◽  
Vol 14 (1) ◽  
pp. 10-21
Author(s):  
Kaili Cheng ◽  
Zhongmin Hu ◽  
Shenggong Li ◽  
Qun Guo ◽  
Yanbin Hao ◽  
...  
Keyword(s):  
Surface Layer ◽  
Nitrogen Availability ◽  
Climatic Variability ◽  
Field Capacity ◽  
Temperate Grassland ◽  
Arid Ecosystems ◽  
Global Change Ecology ◽  
Model Community ◽  
Nitrogen Coupling ◽  
Core Mission

Abstract Aims Prediction of changes in ecosystem gross primary productivity (GPP) in response to climatic variability is a core mission in the field of global change ecology. However, it remains a big challenge for the model community to reproduce the interannual variation (IAV) of GPP in arid ecosystems. Accurate estimates of soil water content (SWC) and GPP sensitivity to SWC are the two most critical aspects for predicting the IAV of GPP in arid ecosystems. Methods We took a widely used model Biome-BGC as an example, to improve the model performances in a temperate grassland ecosystem. Firstly, we updated the estimation of SWC by modifying modules of evapotranspiration, SWC vertical profile and field capacity. Secondly, we modified the function of controlling water–nitrogen relation, which regulates the GPP–SWC sensitivity. Important Findings The original Biome-BGC overestimated the SWC and underestimated the IAV of GPP sensitivity, resulting in lower IAV of GPP than the observations, e.g. it largely underestimated the reduction of GPP in drought years. In comparison, the modified model accurately reproduced the observed seasonal and IAVs in SWC, especially in the surface layer. Simulated GPP–SWC sensitivity was also enhanced and became closer to the observations by optimizing parameter controlling nitrogen mineralization. Consequently, the model’s capability of reproducing IAV of GPP has been largely improved by the modifications. Our results demonstrate that SWC in the surface layer and the consequent effects on nitrogen availability should be among the first considerations for accurate modeling IAV of GPP in arid ecosystems.

scholarly journals Vegetation Growth Models Improve Surface Layer Flux Simulations of a Temperate Grassland

2017 ◽  
Vol 16 (13) ◽  
pp. 1-19 ◽  
Author(s):  
Christian Klein ◽  
Christian Biernath ◽  
Florian Heinlein ◽  
Christoph Thieme ◽  
Anna Katarina Gilgen ◽  
...  
Keyword(s):  
Surface Layer ◽  
Growth Models ◽  
Temperate Grassland ◽  
Vegetation Growth

scholarly journals Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils

2016 ◽  
Author(s):  
Julie N. Weitzman ◽  
Jason P. Kaye
Keyword(s):  
Climatic Variability ◽  
Free Water ◽  
Field Capacity ◽  
Soil Columns ◽  
Retention Capacity ◽  
Nitrate Retention ◽  
Before And After ◽  
Flow Through ◽  
Legacy Sediment ◽  
Stream Waters

Abstract. While eutrophication is often attributed to contemporary nutrient pollution, there is growing evidence that past practices, like the accumulation of legacy sediment behind historic milldams, are also important. Given their prevalence, there is a critical need to understand how N flows through, and is retained in, legacy sediments to improve predictions and management of N transport from uplands to streams in the context of climatic variability and land-use change. Our goal was to determine how nitrate (NO3-) is cycled through the soil of a legacy sediment strewn stream before and after soil drying. We extracted 10.16 cm radius intact soil columns that extended 30 cm into each of the three significant soil horizons at Big Spring Run (BSR) in Lancaster, Pennsylvania: surface legacy sediment characterized by a newly developing mineral A horizon soil, mid-layer legacy sediment consisting of mineral B horizon soil, and a dark, organic-rich, buried relict A horizon soil. Columns were first pre-incubated at field capacity, and then isotopically labeled nitrate (15NO3-) was added and allowed to drain to estimate retention. The columns were then air-dried and subsequently rewet with N-free water and allowed to drain to quantify the drought-induced loss of 15NO3- from the different horizons. We found the highest initial 15N retention in the mid-layer legacy sediment (17 ± 4 %) and buried relict A soil (14 ± 3 %) horizons, with significantly lower retention in the surface legacy sediment (6 ± 1 %) horizon. As expected, rewetting dry soil resulted in 15N losses in all horizons, with the greatest losses in the buried relict A horizon soil, followed by the mid-layer legacy sediment and surface legacy sediment horizons, respectively. The 15N remaining in the soil following the post-drought leaching was highest in the mid-layer legacy sediment, intermediate in the surface legacy sediment, and lowest in the buried relict A horizon soil. Fluctuations in the water table at BSR which affect saturation of the buried relict A horizon soil could lead to great loses of NO3- from the soil, while vertical flow through the legacy sediment-rich soil profile that originates in the surface has the potential to retain more NO3-. Restoration that seeks to reconnect the groundwater and surface water, which will decrease the number of drying-rewetting events imposed on the relict A horizon soils, could initially lead to increased losses of NO3- to nearby stream waters.

Biological soil crusts modulate nitrogen availability in semi-arid ecosystems: insights from a Mediterranean grassland

2010 ◽  
Vol 333 (1-2) ◽  
pp. 21-34 ◽  
Author(s):  
Andrea P. Castillo-Monroy ◽  
Fernando T. Maestre ◽  
Manuel Delgado-Baquerizo ◽  
Antonio Gallardo
Keyword(s):  
Nitrogen Availability ◽  
Biological Soil Crusts ◽  
Arid Ecosystems ◽  
Soil Crusts ◽  
Semi Arid

scholarly journals Nitrate retention capacity of milldam-impacted legacy sediments and relict A horizon soils

SOIL ◽  
2017 ◽  
Vol 3 (2) ◽  
pp. 95-112 ◽  
Author(s):  
Julie N. Weitzman ◽  
Jason P. Kaye
Keyword(s):  
Climatic Variability ◽  
Free Water ◽  
Field Capacity ◽  
Soil Columns ◽  
Retention Capacity ◽  
Nitrate Retention ◽  
Before And After ◽  
Flow Through ◽  
Legacy Sediment ◽  
Stream Waters

Abstract. While eutrophication is often attributed to contemporary nutrient pollution, there is growing evidence that past practices, like the accumulation of legacy sediment behind historic milldams, are also important. Given their prevalence, there is a critical need to understand how N flows through, and is retained in, legacy sediments to improve predictions and management of N transport from uplands to streams in the context of climatic variability and land-use change. Our goal was to determine how nitrate (NO3−) is cycled through the soil of a legacy-sediment-strewn stream before and after soil drying. We extracted 10.16 cm radius intact soil columns that extended 30 cm into each of the three significant soil horizons at Big Spring Run (BSR) in Lancaster, Pennsylvania: surface legacy sediment characterized by a newly developing mineral A horizon soil, mid-layer legacy sediment consisting of mineral B horizon soil and a dark, organic-rich, buried relict A horizon soil. Columns were first preincubated at field capacity and then isotopically labeled nitrate (15NO3−) was added and allowed to drain to estimate retention. The columns were then air-dried and subsequently rewet with N-free water and allowed to drain to quantify the drought-induced loss of 15NO3− from the different horizons. We found the highest initial 15N retention in the mid-layer legacy sediment (17 ± 4 %) and buried relict A soil (14 ± 3 %) horizons, with significantly lower retention in the surface legacy sediment (6 ± 1 %) horizon. As expected, rewetting dry soil resulted in 15N losses in all horizons, with the greatest losses in the buried relict A horizon soil, followed by the mid-layer legacy sediment and surface legacy sediment horizons. The 15N remaining in the soil following the post-drought leaching was highest in the mid-layer legacy sediment, intermediate in the surface legacy sediment, and lowest in the buried relict A horizon soil. Fluctuations in the water table at BSR which affect saturation of the buried relict A horizon soil could lead to great loses of NO3− from the soil, while vertical flow through the legacy-sediment-rich soil profile that originates in the surface has the potential to retain more NO3−. Restoration that seeks to reconnect the groundwater and surface water, which will decrease the number of drying–rewetting events imposed on the relict A horizon soils, could initially lead to increased losses of NO3− to nearby stream waters.

The redistribution of a surface layer of solute during the drainage of a soil profile to field capacity

1984 ◽  
Vol 103 (1) ◽  
pp. 229-238
Author(s):  
G. D. Towner
Keyword(s):  
Surface Layer ◽  
Soil Profile ◽  
Field Capacity ◽  
Solute Concentration ◽  
Concentration Profiles ◽  
Flow Conditions ◽  
Water Flows ◽  
Agricultural Application ◽  
Water Redistribution ◽  
Initial Deposition

SummaryAn approximate analytical method derived by Wilson & Gelhar (1981) is a powerful and flexible one for calculating solute distribution profiles developing under steady state and transient water flow conditions. Solute concentration profiles developing from an initial deposition in the surface layer, as the soil profile returns to field capacity, have been calculated using the method for idealized representations of the two principal forms of water redistribution.The profiles depend very strongly on the mode of redistribution of the water. However, the small spread of the final profiles (at field capacity) across the range of water redistribution types examined suggest that, for agricultural application, it might be accurate enough to use a simplified representation of the actual redistribution rather than the correct, and inevitably more complicated, water flows and distribution.

scholarly journals Available water capacity of the surface layer of various soils from the arid and semiarid region of Puerto Rico

1969 ◽  
Vol 36 (2) ◽  
pp. 134-140
Author(s):  
M. A. Lugo López
Keyword(s):  
Surface Layer ◽  
Puerto Rico ◽  
Sandy Loam ◽  
Field Capacity ◽  
Semiarid Region ◽  
Water Capacity ◽  
Semiarid Regions ◽  
Available Water ◽  
Available Water Capacity ◽  
Arid And Semiarid

The available water of soils is considered to be in the moisture range from field capacity to permanent wilting percentage. The customary procedures for determining these two soil constants are quite inconvenient. Although data are presented that show good agreement between moisture equivalents and field-capacity values in selected soils, it was not possible to obtain a reliable regression with soils from the arid and semiarid regions of Puerto Rico. The regression of permanent wilting percentages by the plant method to 15-atmosphere percentages is expressed by the equation, Y = 2.37 + 0.76 X, in which Y is the permanent wilting percentage and X is the 15- atmosphere percentage. Data on the available water capacity of the surface layer of sons from the arid and semiarid regions of Puerto Rico are presented. The range of available water is adequate in most soils, fluctuating from about 18 to 25, except in sands where it is lower. It is about the same in heavy soils such as clays and clay loams as in lighter ones such as sandy loam and sandy clay loams.

The oxidation of Inconel alloy MA754 at low oxidation potential

1983 ◽  
Vol 41 ◽  
pp. 218-219
Author(s):  
D. N. Braski ◽  
P. D. Goodell ◽  
J. V. Cathcart ◽  
R. H. Kane
Keyword(s):  
Surface Layer ◽  
Oxidation Potential ◽  
Metal Interface ◽  
Elevated Temperature Strength ◽  
Surface Conditions ◽  
Inconel Alloy ◽  
Inco Alloy ◽  
Resistance To Oxidation ◽  
Oxide Particles ◽  
Cold Worked

It has been known for some time that the addition of small oxide particles to an 80 Ni—20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid enhances the oxidation resistance is being studied collaboratively by ORNL and INCO Alloy Products Company.Initial experiments were performed using INCONEL alloy MA754, which is nominally: 78 Ni, 20 Cr, 0.05 C, 0.3 Al, 0.5 Ti, 1.0 Fe, and 0.6 Y2O3 (wt %).Small disks (3 mm diam × 0.38 mm thick) were cut from MA754 plate stock and prepared with two different surface conditions. The first was prepared by mechanically polishing one side of a disk through 0.5 μm diamond on a syntron polisher while the second used an additional sulfuric acid-methanol electropolishing treatment to remove the cold-worked surface layer. Disks having both surface treatments were oxidized in a radiantly heated furnace for 30 s at 1000°C. Three different environments were investigated: hydrogen with nominal dew points of 0°C, —25°C, and —55°C. The oxide particles and films were examined in TEM by using extraction replicas (carbon) and by backpolishing to the oxide/metal interface. The particles were analyzed by EDS and SAD.

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 738-739
Author(s):  
W. H. Wu ◽  
R. M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Structural Analysis ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Surface Layer Protein ◽  
Morphological Unit ◽  
Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

Electron-Mirror Microscopic Aspects of Ferroelectric Domains of BaTiO3 And Ca2Sr (C2H5CO2)6

1970 ◽  
Vol 28 ◽  
pp. 478-479
Author(s):  
Teruo Someya ◽  
Jinzo Kobayashi
Keyword(s):  
Surface Layer ◽  
Electric Fields ◽  
Quantitative Study ◽  
Recent Progress ◽  
Ferroelectric Domain ◽  
Resolving Power ◽  
Surface Pattern ◽  
Crystal Surfaces ◽  
One Dimensional ◽  
Ferroelectric Domains

Recent progress in the electron-mirror microscopy (EMM), e.g., an improvement of its resolving power together with an increase of the magnification makes it useful for investigating the ferroelectric domain physics. English has recently observed the domain texture in the surface layer of BaTiO3. The present authors ) have developed a theory by which one can evaluate small one-dimensional electric fields and/or topographic step heights in the crystal surfaces from their EMM pictures. This theory was applied to a quantitative study of the surface pattern of BaTiO3).

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