The term 'bioturbation' is frequently used to describe how living organisms affect the substratum in which they live. A closer look at the aquatic science literature reveals, however, an inconsistent usage of the term with increasing perplexity in recent years. Faunal disturbance has often been referred to as particle reworking, while water movement (if considered) is re ferred to as bioirrigation in many cases. For consistency, we therefore propose that, for contemporary aquatic scientific disciplines, faunal bioturbation in aquatic environments includes all transport processes carried out by animals that directly or indirectly affect sediment matrices. These pro- cesses include both particle reworking and burrow ventilation. With this definition, bioturbation acts as an 'umbrella' term that covers all transport processes and their physical effects on the sub- stratum. Particle reworking occurs through burrow construction and maintenance, as well as ingestion and defecation, and causes biomixing of the substratum. Organic matter and microor- ganisms are thus displaced vertically and laterally within the sediment matrix. Particle reworking animals can be categorized as biodiffusors, upward conveyors, downward conveyors and regen- erators depending on their behaviour, life style and feeding type. Burrow ventilation occurs when animals flush their open- or blind-ended burrows with overlying water for respiratory and feeding purposes, and it causes advective or diffusive bioirrigation ex change of solutes between the sedi- ment pore water and the overlying water body. Many bioturbating species perform reworking and ventilation simultaneously. We also propose that the effects of bioturbation on other organisms and associated processes (e.g. microbial driven biogeochemical transformations) are considered within the conceptual framework of ecosystem engineering.

https://www.int-res.com/articles/meps_oa/m446p285.pdf

What is bioturbation? The need for a precise definition for fauna in aquatic sciences

Biohydrogen production from biomass and industrial wastes by dark fermentation

Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure, constrain parameters, and prescribe forcing fields.

/pdf/toward-more-realistic-projections-of-soil-carbon-dynamics-by-5aslmg0iur.pdf

Toward more realistic projections of soil carbon dynamics by Earth system models

No-tillage and soil physical environment

https://d2vsp3qmody48p.cloudfront.net/wp-content/uploads/sites/6/2014/07/Van-Driesche-et-al.-2010.pdf

Classical biological control for the protection of natural ecosystems

Winter wheat-summer fallow is the conventional cropping system employed on > 15 million ha within the Columbia Plateau of eastern Washington and northern Oregon Wind erosion contributes to poor air quality in the region, yet little is known concerning the magnitude of soil and PM10 (particulate matter of = 90 per cent of the eroded sediment, indicating that direct suspension may be an important process by which the silt loam eroded The corresponding loss of PM10 for these two events ranged from 5 to 210 kg ha(-1) Loss of PM10 comprised 9-12 per cent of the total soil loss for the six events This study suggests that the relatively small loss of PM10 from eroding agricultural fields maintained in summer fallow can affect air quality in the Columbia Plateau Therefore, alternative tillage practices or cropping systems are needed for minimizing PM10 emissions and improving air quality in the region Copyright (c) 2006 John Wiley & Sons, Ltd

Loss of soil and PM10 from agricultural fields associated with high winds on the Columbia Plateau

Dynamic versus steady-state approaches to evaluate irrigation management of saline waters

Water-repellent soils exhibit a positive water entry pressure head, h p . The effects of imposing differing water pressure head values, by using differing water ponding depths, h o , on infiltration into water-repellent soils was investigated. A sand, with particulate size between 0.05 and 2.0 mm, was treated with two concentrations of octadecylamine to create a sand with h p values of 8.4 and 3.5 cm. The hydraulic conductivity, K, of the water-repellent sands increased with increasing values of h g . The K of the treated sand was equal to K of untreated sand when the ratio h 0 /h p was 3.1 for each treated sand. The infiltration rate increased with increased time for lower h g values, but decreased with increased time for higher h g values. The transition from increasing to decreasing infiltration rates with time occurred when h o /h p was approximately equal to 2.6. The infiltration rate behavior of an aqueous ethanol solution was consistent with theoretical relationships based on liquid surface tension. A positive hydraulic head was created at the interface of an overlying wettable and underlying water-repellent layer that affected the infiltration rate consistent with the effects of h 0 on a nonlayered water-repellent sand. The following mechanism is proposed to explain the increase in infiltration rate with time. In water-repellent materials, positive hydraulic heads can be created within the profile during infiltration, which can increase as the depth to the wetting front increases. The higher hydraulic head induces an increase in hydraulic conductivity, which contributes to increased infiltration rate. Alternatively, if the depth of ponded water is sufficient to cause a hydraulic conductivity equal to that of the wettable material, the infiltration rate behavior is the same as traditionally observed for wettable soils.

Water Ponding Depths Affect Temporal Infiltration Rates in a Water-Repellent Sand

Soil management effects on the nonlimiting water range

Wind erosion from agricultural fields contributes to poor air quality within the Columbia Plateau of the United States. Erosion from fields managed in a conventional winter wheat–summer fallow rotation was monitored during the fallow period near Washtucna, WA, in 2003 and 2004. Loss of soil and PM10 (particulates ≤10 µm in diameter) was measured during six high wind events (sustained wind speed at 3 m height >6·4 m s−1). Soil loss associated with suspension, saltation and creep as well as PM10 emission was used to validate the Wind Erosion Prediction System (WEPS) erosion submodel. Input parameters for WEPS simulations were measured before each high wind event. The erosion submodel produced no erosion for half of the observed events and over-predicted total soil loss by 200–700 kg ha−1 for the remaining events. The model appears to over-predict total soil loss as a result of overestimating creep, saltation and suspension. The model both over-predicted and under-predicted PM10 loss. High values for the index of agreement (d > 0·5) suggest that the performance of the model is acceptable for the conditions of this study. While the performance of the model is acceptable, improvements can be made in modeling efficiency by better specifying the static threshold friction velocity or coefficients that govern emissions, abrasion and breakage of silt loams on the Columbia Plateau. Copyright © 2006 John Wiley & Sons, Ltd.

Guanglong Feng

Papers

Loss of soil and PM10 from agricultural fields associated with high winds on the Columbia Plateau

Dynamic versus steady-state approaches to evaluate irrigation management of saline waters

Water Ponding Depths Affect Temporal Infiltration Rates in a Water-Repellent Sand

Soil management effects on the nonlimiting water range

Validation of WEPS for soil and PM10 loss from agricultural fields within the Columbia Plateau of the United States