scholarly journals Spatial-and temporal-patterns of global soil heterotrophic respiration in terrestrial ecosystems

2019 ◽  
Author(s):  
Xiaolu Tang ◽  
Shaohui Fan ◽  
Manyi Du ◽  
Wenjie Zhang ◽  
Sicong Gao ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Temporal Patterns ◽  
Heterotrophic Respiration ◽  
Spatial And Temporal Patterns ◽  
Carbon Loss ◽  
Global Land ◽  
Global Soil ◽  
Soil Heterotrophic Respiration

Abstract. Soil heterotrophic respiration (RH) is one of the largest and most uncertain components of the terrestrial carbon cycle, directly reflecting carbon loss from soil to the atmosphere. However, high variations and uncertainties of RH existing in global carbon cycling models require an urgent development of data-derived RH dataset. To fill this knowledge gap, this study applied Random Forest (RF) algorithm – a machine learning approach, to (1) develop a globally gridded RH dataset and (2) investigate its spatial- and temporal-patterns from 1980 to 2016 at the global scale by linking field observations from the Global Soil Respiration Database and global environmental drivers – temperature, precipitation, soil water content, etc. Finally, a globally gridded RH dataset was developed covering from 1980 to 2016 with a spatial resolution of half degree and a temporal resolution of one year. Globally, the average annual RH was 57.2 ± 0.6 Pg C a−1 from 1980 to 2016, with a significantly increasing trend of 0.036 ± 0.007 Pg C a−2. However, the temporal trend of the carbon loss from RH varied with climate zones that RH showed significant increasing trends in boreal and temperate areas, in contrast, such trend was absent in tropical regions. Temperature driven RH dominated 39 % of global land and was mainly distributed at a high latitude. While the areas dominated by precipitation and soil water content were mainly semi-arid and tropical areas, accounting for 36 % and 25 % of the global land, respectively, suggesting variations in the dominance of environmental controls on the spatial patterns of RH. The developed globally gridded RH dataset will further aid in understanding of the mechanisms of global soil carbon dynamics, serving as a benchmark to constrain global vegetation models. The dataset is publicly available at https://doi.org/10.6084/m9.figshare.8882567 (Tang et al., 2019a).

scholarly journals Spatial and temporal patterns of global soil heterotrophic respiration in terrestrial ecosystems

2020 ◽  
Vol 12 (2) ◽  
pp. 1037-1051 ◽  
Author(s):  
Xiaolu Tang ◽  
Shaohui Fan ◽  
Manyi Du ◽  
Wenjie Zhang ◽  
Sicong Gao ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Heterotrophic Respiration ◽  
Spatial And Temporal Patterns ◽  
Carbon Loss ◽  
Global Land ◽  
Increasing Trend ◽  
Global Soil ◽  
Soil Heterotrophic Respiration

Abstract. Soil heterotrophic respiration (RH) is one of the largest and most uncertain components of the terrestrial carbon cycle, directly reflecting carbon loss from soils to the atmosphere. However, high variations and uncertainties of RH existing in global carbon cycling models require RH estimates from different angles, e.g., a data-driven angle. To fill this knowledge gap, this study applied a Random Forest (RF) algorithm (a machine learning approach) to (1) develop a globally gridded RH dataset and (2) investigate its spatial and temporal patterns from 1980 to 2016 at the global scale by linking field observations from the Global Soil Respiration Database and global environmental drivers (temperature, precipitation, soil water content, etc.). Finally, a globally gridded RH dataset was developed covering from 1980 to 2016 with a spatial resolution of half a degree and a temporal resolution of 1 year. Globally, the average annual RH was 57.2±0.6 Pg C a−1 from 1980 to 2016, with a significantly increasing trend of 0.036±0.007 Pg C a−2. However, the temporal trend of the carbon loss from RH varied in climate zones, and RH showed a significant and increasing trend in boreal and temperate areas. In contrast, such a trend was absent in tropical regions. Temperature-driven RH dominated 39 % of global land and was primarily distributed at high-latitude areas. The areas dominated by precipitation and soil water content were mainly semiarid and tropical areas, accounting for 36 % and 25 % of global land area, respectively, suggesting variations in the dominance of environmental controls on the spatial patterns of RH. The developed globally gridded RH dataset will further aid in the understanding of the mechanisms of global soil carbon dynamics, serving as a benchmark to constrain terrestrial biogeochemical models. The dataset is publicly available at https://doi.org/10.6084/m9.figshare.8882567 (Tang et al., 2019a).

scholarly journals Field spatial and temporal patterns of soil water content and bulk density changes

2006 ◽  
Vol 63 (1) ◽  
pp. 55-64 ◽  
Author(s):  
Luís Carlos Timm ◽  
Luiz Fernando Pires ◽  
Renato Roveratti ◽  
Robson Clayton Jacques Arthur ◽  
Klaus Reichardt ◽  
...  
Keyword(s):  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Surface ◽  
Temporal Patterns ◽  
Temporal Changes ◽  
Spatial And Temporal Patterns ◽  
Wetting And Drying ◽  
Wetting And Drying Cycles

Soil water content (theta) and bulk density (rhos) greatly influence important soil and plant processes, such as water movement, soil compaction, soil aeration, and plant root system development. Spatial and temporal variability of theta and rhos during different periods of the year and different phases of crops are of fundamental interest. This work involves the characterization of spatial and temporal patterns of theta and rhos during different climatic periods of year, aiming to verify whether there are significant temporal changes in rhos at the soil surface layer when submitted to wetting and drying cycles. The field experiment was carried out in a coffee plantation, Rhodic Kandiudalf soil, clayey texture. Using a neutron/gamma surface probe, theta and rhos were measured meter by meter along a 200 m spatial transect, along an interrow contour line. During the wet period there was no difference of spatial patterns of theta while during the dry period differences were observed, and can be associated to precipitation events. It was also observed that there are rhos temporal changes at the soil surface along the studied period as a consequence of the in situ wetting and drying cycles.

Soil heterotrophic respiration is insensitive to changes in soil water content but related to microbial access to organic matter

Geoderma ◽  
2016 ◽  
Vol 274 ◽  
pp. 68-78 ◽  
Author(s):  
Gabriel Y.K. Moinet ◽  
Ellen Cieraad ◽  
John E. Hunt ◽  
Anitra Fraser ◽  
Matthew H. Turnbull ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Heterotrophic Respiration ◽  
Soil Heterotrophic Respiration

The influence of soil structure on heterotrophic respiration response to soil water content

2020 ◽  
Author(s):  
Michael Herbst ◽  
Wolfgang Tappe ◽  
Sirgit Kummer ◽  
Harry Vereecken
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Structure ◽  
Water Saturation ◽  
Textural Properties ◽  
Heterotrophic Respiration ◽  
Soil Heterotrophic Respiration ◽  
Undisturbed Soils ◽  
Soil Water Saturation

<p>Soil respiration causes one of the largest terrestrial carbon fluxes and its accurate prediction is still a matter of on-going research. Understanding the functional link between soil heterotrophic respiration and soil water content is relevant for the estimation of climate change impacts on soil CO<sub>2</sub> emissions. <br>In order to quantify the effect of air-drying and sieving with 2 mm meshes on the soil heterotrophic respiration response to water content we incubated intact cores and sieved samples of two loamy and two sandy agricultural topsoils for six levels of effective soil water saturation. We further measured soil textural properties and the soil water retention characteristics of the soils with the aim to identify potential correlations between soil physical parameters and moisture sensitivity functions of heterotrophic respiration. <br>The incubation of sieved and intact soils showed distinct differences in the response of soil heterotrophic respiration to soil water saturation. The sieved soils exposed threshold-type behaviour, whereas the undisturbed soils exposed a quadratic increase of heterotrophic respiration with increasing effective soil water content. Additionally, we found significant correlations between the moisture response functions of the undisturbed soils and soil textural properties.<br>From the comparison of intact and sieved soil incubations we conclude that the destruction of soil structure by sieving hampers the transferability of measured soil moisture response of heterotrophic respiration to real-world conditions. For modelling purposes we suggest the use of a quadratic function between relative respiration and effective saturation for soils with a clay fraction < 20 %.</p>

scholarly journals Spatial and temporal patterns of soil water content in an agroecological production system

2017 ◽  
Vol 74 (5) ◽  
pp. 383-392 ◽  
Author(s):  
Hugo Hermsdorff das Neves ◽  
Maria Gabriela Ferreira da Mata ◽  
José Guilherme Marinho Guerra ◽  
Daniel Fonseca de Carvalho ◽  
Ole Otto Wendroth ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Production System ◽  
Temporal Patterns ◽  
Spatial And Temporal Patterns

Soil heterotrophic respiration as a function of water content and temperature in a mechanistic pore-scale model

2020 ◽  
Author(s):  
Mehdi Gharasoo ◽  
Linden Fairbairn ◽  
Fereidoun Rezanezhad ◽  
Philippe Van Cappellen
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Case Studies ◽  
Water Saturation ◽  
Empirical Models ◽  
Heterotrophic Respiration ◽  
Scale Model ◽  
Respiration Rates ◽  
Bioavailable Fraction ◽  
Soil Heterotrophic Respiration

<p>Soil heterotrophic respiration has been considered as a key source of CO<sub>2</sub> flux into the atmosphere and thus plays an important role in global warming. Although the relationship between soil heterotrophic respiration and soil water content has been frequently studied both theoretically and experimentally, model development has thus far been empirically based. Empirical models are often limited to the specific condition of their case studies and cannot be used as a general platform for modeling. Moreover, it is difficult to extend the empirical models by theoretically defined affinities to any desired degree of accuracy. As a result, it is of high priority to develop process-based models that are able to describe the mechanisms behind this phenomenon with more deterministic terms.</p><p>Here we present a mechanistic, mathematically-driven model that is based on the common geometry of a pore in porous media. Assuming that the aerobic respiration of bacteria requires oxygen as an electron acceptor and dissolved organic carbon (DOC) as a substrate, the CO<sub>2</sub> fluxes are considered a function of the bioavailable fraction of both DOC and oxygen. In this modeling approach, the availability of oxygen is controlled by its penetration into the aquatic phase through the interface between air and water. DOC on the other hand is only available to a section of the soil that is in contact with water. As the water saturation in the pore changes, it dynamically and kinematically impacts these interfaces through which the mass transfer of nutrients occurs, and therefore the CO<sub>2</sub> fluxes are directly controlled by water content. We showcased the model applicability on several case studies and illustrated the model capability in simulating the observed microbial respiration rates versus the soil water contents. Furthermore, we showed the model potential to accept additional physically-motivated parameters in order to explain respiration rates in frozen soils or at different temperatures.</p>

Response of heterotrophic respiration and oxidation of atmospheric CH4 to changes in soil moisture and temperature in drylands across a global climate and ecosystem gradient

2020 ◽  
Author(s):  
Thomas Hessilt ◽  
Daniel Lyberth Hauptmann ◽  
Jesper Riis Christiansen
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Global Climate ◽  
Heterotrophic Respiration ◽  
Mean Annual Temperature ◽  
Specific Response ◽  
Carbon Turnover ◽  
Site Specific

<p>Soil moisture and temperature collectively regulate the production and consumption of carbon in soils. With expected changes in both the soil thermal and hydrological regimes globally, experimental data on carbon turnover under these changes in contrasting ecosystems are important for constraining predictive models of soil carbon turnover. We investigated the effect of changes in soil water and temperature on heterotrophic respiration (Rh) and net methane uptake (MU) in soils from grassland ecosystems in Arctic, temperate and subtropical climates.<br>The temperature sensitivity of RH increased with decreasing mean annual temperature, but there was no indication of a site-specific response of Rh to changes in soil moisture. All sites displayed MU, primarily controlled by the soil water content with little temperature dependence. Thus, the optimum temperature for MU did not differ between sites despite the differences in the climate. However, the optimal soil water content for the relative maximum MU decreased with increasing mean annual temperature at the sites.<br>These results point to site-specific adaptation of the microbial community that governs the sensitivity of Rh to temperature, but not soil moisture and the dependency of MU to soil moisture alone. We would also like to discuss how this insight can be used to inform ecosystem models.</p>

Point specific measurement and monitoring of soil water content with an emphasis on TDR

1996 ◽  
Vol 76 (3) ◽  
pp. 307-316 ◽  
Author(s):  
G. C. Topp ◽  
H. N. Hayhoe ◽  
M. Watt
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Root Exudation ◽  
Time Domain Reflectometry ◽  
Ease Of Use ◽  
In Situ Monitoring ◽  
Spatial And Temporal Patterns ◽  
Near Surface ◽  
Specific Measurement

During the past decade, a number of developments have improved the possibilities for real-time, in situ monitoring of soil water content, providing potential for much improved testing and validation of soil water models Brief reviews of the principles and procedures are presented for the gravimetric and gamma ray attenuation methods. A summary of the developments of time-domain reflectometry (TDR) demonstrates its high capability for continuous monitoring of soil water content. Portable dielectric probes (PDP) and capacitance instruments also use the high dielectric constant of water as an indicator of soil water content. Commercially available TDR instruments offer a choice of options that allow this method to be fitted to a variety of specific measurement requirements. The ease of use and portability of TDR instruments and the flexibility of design for the TDR probes has made possible the rapid measurement of surface and near surface water contents on a field scale. Multiplexers and data loggers now allow the efficient monitoring of water content to record both spatial and temporal patterns not previously detectable. Fine resolution and analyses within the electric field of a TDR probe has allowed us to measure and record the diurnal patterns of water uptake from, and its release to, relatively dry sod adjacent to growing corn roots Water distribution calculations show that the water measured as moving in and out of roots daily is sufficient to hydrate and stabilize the sheaths of soil that surround the root growing in dry soil. Key words: Soil water content, TDR, root uptake, root exudation, field measurement, water balance

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