Soil moisture as determinant of the seasonal soil co2 emission: evidence from central siberia

Background The soils of the boreal zone contain significant reserves of carbon, therefore, their response to current climate changes will significantly affect the sustainability of forest ecosystems and the future concentration of CO 2 in the atmosphere. When modeling soil emission, it is necessary to focus on the main soil environment factors. In this paper, a simple exponential model of the soil CO 2 emissions growth was modified by introducing an additional parameter - the threshold soil moisture in different types of ecosystems based on the direct measurements. Results The developed model adequately reflects the dynamic changes in soil emission for different types of ecosystems. This result was achieved by including moisture as a second environmental factor besides temperature, describing changes in soil CO 2 emissions during the summer period. The error of direct measurements for all measuring seasons was about 20% of the values of direct measurements of the CO 2 flux. Note that such a high error was observed once per season in early and mid-June, reaching 60-80% on some days. Our models demonstrate in the season with the highest amount of precipitation the smallest differences in modeled fluxes about 15-20%, which indirectly indicates that the emission flux is not inhibited by insufficient moisture in this season. Conclusions The final model application depends on the characteristics of the microclimatic conditions of a particular ecosystem, namely, a factor that has a limiting effect on the biological processes. When studying the functional role of boreal forest ecosystems the moisture conditions consideration is crucial to explain the atmospheric CO 2 emission processes.

Soil Carbon Dioxide Emission in Extreme Environment of the Center of Moscow Megapolis

<p>Moscow is the largest megapolis in Europe. The area of sealed areas in the center of Moscow is more than 50% (without hydrological objects). Anti-icing mixtures, car traffic, aerosols, dust, trampling - all this leads to the maximum stress of ecosystems in an urban environment Soil emission is the largest component of Gross Respiration in terrestrial ecosystems, including cities. Field measurements of emission allow estimating and comparing the state of both the underground tier and the entire ecosystem in different functional zones of a city with different types of vegetation. Soil emission is the easiest to measure, as compared to other fluxes of С-exchange. In 2019, field measurements of carbon dioxide emissions were carried out at 15 key sites (15 times, 1 per 2 weeks), which showed that in the historic center, not only the temperature at different depths of the soil, soil moisture, carbon content, particle size distribution, but also the diversity of factors combined into a group of "land use", namely: human tillage, irrigation, lawn mowing, garbage removal, sprinkling peat-compost mixture, trampling, bringing anti-icing reagents, etc., have a contrasting effect on carbon dioxide emissions from urban soils. In some cases, the emission is below the conditional background values (urban forest), in other cases, it is higher up to several times, which allows a new assessment of soils of unsealed (open) areas of the center of a megapolis as an important component of the (micro-) regional C-cycle. The data obtained allow comparing the current state of the upper part of the underground tier of urban ecosystems under the maximum anthropogenic load in the territory of a modern large city, where the share of open surfaces is minimal. The territories, where the ground layer is represented by cultivated lawn, are characterized by the maximum values of soil carbon dioxide emission.</p><p><em>T</em><em>he study was supported by the Russian Research Foundation #19-77-30012 (field measurements in the periphery of Moscow) and the Russian Foundation for Basic Research #18-35-20052 (field measurements in the historic center of Moscow).</em></p>

BVOC emission simulation for the Vienna region during an extreme heat event.

<p>Biogenic volatile organic compounds (BVOC) are emitted by trees. In the presence of NOx they can help to produce tropospheric ozone. During heat waves this can cause a critical additional stress for human wellbeing, especially in areas exhibiting high NOx concentrations. Heat wave intensity and frequency is expected to increase.</p><p>To estimate the potential threat, we simulate BVOC emissions over the Vienna region during an extreme heat wave using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) (Guenther et al. 2012) in its latest version 3.  We adapted the model to directly ingest the files used and produced by the land surface model SURFEX8.1 (Surface Externalisée, in French) (Boone et al. 2017) and its preprocessors. In this poster we present our methodology and first results showing the spatial distribution and time series of selected BVOCs.</p><p>The chosen heat wave covers 5 days during August 2015, with an average daily 2 m air temperature of 36.3 °C, and represents a significant event with a 15 year return period (of the period 1988-2017).</p><p>The LAI and soil parameters field capacity and wilting point are taken from the physiographic fields derived from ECOCLIMAP,  soil moisture and temperature from the prognostic SURFEX output fields calculated for urban and non-urban areas, the 2m air temperature from the diagnostic output fields of SURFEX.</p><p>The meteorological forcing is used to create daily meteorology parameters and together with LAI maps run the canopy meteorology module. Further we use the soil emission activity module to calculate a soil temperature and soil moisture dependent isoprene soil emission activity factor. Using these datasets the emission activity factors are calculated. Finally, the emission activity factors are converted from 20 to 201 species and lumped according to the RACM2 mechanism. </p><p>First results, show the strong dependence of isoprene emissions on incoming photosynthetically active radiation and LAI. In the course of the<br>heat wave isoprene emissions decline, which correlates with the decline in soil water availability and consqequent decreased stomatal opening. </p><p> </p><p>Boone, A., Samuelsson, P., Gollvik, S., Napoly, A., Jarlan, L., Brun, E., & Decharme, B. (2017). The interactions between soil–biosphere–atmosphere land surface model with a multi-energy balance (ISBA-MEB) option in SURFEXv8 – Part 1: Model description. <em>Geoscientific Model Development</em>, <em>10</em>(2), 843–872. </p><p>Guenther, A. B., Jiang, X., Heald, C. L., Sakulyanontvittaya, T., Duhl, T., Emmons, L. K., & Wang, X. (2012). The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): an extended and updated framework for modeling biogenic emissions. <em>Geoscientific Model Development</em>, <em>5</em>(6), 1471–1492. </p>

Carbon Dioxide Emissions in Agricultural Systems in the Brazilian Savanna

The objectives of this work were to evaluate the CO2 emission potential of an Oxisol under integrated crop-livestock and no-tillage systems in the Brasilian Savanna; and to analyze the impact of soil temperature and soil moisture as factors that regulate the seasonality and the emission of C-CO2 in these systems. Field-scale study was carried out at Fazenda Brejinho, in Pedro Afonso-TO, under Oxisol. The production systems studied were integrated crop-livestock and no-tillage under cropped with soybean and corn. The amount of carbon (C) released from the soil in the form of CO2 (C-CO2) was evaluated using cylindrical chambers installed in the field with a vial containing sodium hydroxide to collect CO2 released from the soil (soil emission) in an interval of 15 hours. Five evaluations were conducted over crops growing season, started in 01/26 through 06/16/2015. Data were tested to analysis of variance and the means were compared with Duncan test at 5%. The emission of C-CO2 differed between treatments in all evaluation periods. On average, the temperature ranged from 26.5 to 27.7 °C, the soil moisture ranged from 12.2 to 15.7% and the C-CO2 emission ranged from 87.4 to 119.9 mg m-2 h-1. Temperature, soil moisture and the production systems contributed to the emission and seasonality of carbon dioxide emissions. The integrated crop-livestock cropped with soybean/corn rotation was the system that had the lowest carbon dioxide emission.

Use of the Radiocarbon Activity Deficit in Vegetation as a Sensor of CO2 Soil Degassing: Example from La Solfatara (Naples, Southern Italy)

Soil CO2 flux measurement is a key method that can be used to monitor the hazards in an active volcanic area. In order to determine accurately the variations of the CO2 soil emission we propose an approach based on the radiocarbon (14C) deficiency recorded in the plants grown in and around the Solfatara (Naples, Italy). We twice sampled selected poaceae plants in 17 defined sites around the Solfatara volcano. 14C measurements by liquid scintillation counting (LSC) were achieved on the grass samples. The 14C deficiency determined in the sampled plants, compared to the atmosphere 14C activity, ranged from 6.6 to 51.6%. We then compared the proportion of magmatic CO2 inferred to the instantaneous measurements of CO2 fluxes from soil performed by the accumulation chamber CO2 degassing measurement at the moment of the sampling at each site. The results show a clear correlation (r=0.88) between soil CO2 fluxes and 14C activity. The determination of the plants 14C deficiency provides an estimate of the CO2 rate within a few square meters, integrating CO2 soil degassing variations and meteorological incidences over a few months. It can therefore become an efficient bio-sensor and can be used as a proxy to cartography of the soil CO2 and to determine its variations through time