In this communication, a wide overview of historical Long-Term Experimental Platforms (LTEP) regarding changes in soil organic matter is presented for the purpose of networking, data sharing, experience sharing and the coordinated design of experiments in the area of Earth system science. This serves to introduce a specific platform of experiments regarding biochar application to soil (LTEP-BIOCHAR) and its use for agronomic and environmental purposes (e.g., carbon sequestration, soil erosion, soil biodiversity) in real conditions and over a significative timeframe for pedosphere dynamics. The methodological framework, including the goals, geographical scope and eligibility rules of such a new platform, is discussed. Currently, the LTEP-BIOCHAR is the first of its kind, a community-driven resource dedicated to biochar, and displays around 20 long-term experiments from Europe, the Middle East and Africa. The selected field experiments take place under dynamically, meteorologically and biologically different conditions. The purposes of the platform are (1) listing the field experiments that are currently active, (2) uncovering methodological gaps in the current experiments and allowing specific metadata analysis, (3) suggesting the testing of new hypotheses without unnecessary duplications while establishing a minimum standard of analysis and methods to make experiments comparable, (4) creating a network of expert researchers working on the agronomical and environmental effects of biochar, (5) supporting the design of coordinated experiments and (6) promoting the platform at a wider international level.
<p>The last decade has seen an increase of innovative soil carbon models that takes explicitly into account the microbial community interaction with the soil organic matter, and various state of protection of the soil organic matter itself. This proliferation is fuelled by (a) the recognition that microbial ecology is the main determinant of soil organic carbon mineralization, and (b) that soil organic matter can be protected from microbial degradation in various ways. Of particular interest is the interaction of the organic matter with the mineral fraction of the soil, which can lead to mineral adsorbtion and the formation of soil aggregates. However, the uncertainties about soil microbial ecology and organic matter &#8211; mineral fraction have led to the formulation of various soil microbial models, each one modelling some of the aspects of the complex net of interacting processes, but not other. These models often use different assumptions, model structures, and pool definitions. The lack of comparability among models, and the low comparability of models with measurable data, makes it hard to discriminate among them and to use them to assess the driving processes relevant for soil carbon dynamics depending on climatic, soil and vegetation conditions.</p> <p>A first attempt to compare some of these models has been presented in Sulman et al. (2018); however, the lack of a harmonization framework for the models, and the use of lumped model pools/flows such as soil respiration and bulk soil organic carbon, have led to the conclusion that the uncertainties are too elevated to discriminate among the models.</p> <p>Here, we propose a framework to harmonize five different soil microbial models among them (MEND, CORPSE, MIMIC, DEMENT, RESOM), and harmonize them with measurable soil organic matter fraction widely recognized as related to processes of interaction with the soil mineral fraction (aggregates, mineral associated organic matter, dissolve organic matter, and particulate organic matter). We reformulated the five models based on this framework, and analysed them on the same parameter space to understand in which regions of said space the models gave results that were substantially different.</p> <p>The results show that: (a) the model can be clearly distinguished in most regions of the parameters space, (b) it is possible to calculate an index of robustness of the models. This information can help in design specific experiments to test the models and, this way, get insights about the driving processes in certain conditions (different climates, soils, vegetations); moreover, the robustness index can give indication about their applicability to different conditions, which is of utmost importance if they are to inform Earth System Models.</p>
<div> <p><span data-contrast="auto">After a long debate spanning 20 years, biochar has emerged as a promising land management technique for addressing climate change and improving soil fertility. Biochar is an effective long-term carbon store due to its resistance to decomposition compared to fresh organic matter or compost, and it has the potential to stabilize soil organic matter when added to the soil.</span><span data-ccp-props="{&quot;201341983&quot;:0,&quot;335551550&quot;:1,&quot;335551620&quot;:1,&quot;335559738&quot;:0,&quot;335559739&quot;:160,&quot;335559740&quot;:259}">&#160;</span></p> </div> <div> <p><span data-contrast="auto">However, there is a lack of long-term data and knowledge about Soil Organic Carbon (SOC) stocks due to a lack of historical databases. Studies have shown that few experiments have lasted over 3 and focused on estimating SOC increase from biochar application. Additionally, few of these studies have measured biochar decay rate.&#160;</span><span data-ccp-props="{&quot;201341983&quot;:0,&quot;335551550&quot;:1,&quot;335551620&quot;:1,&quot;335559738&quot;:0,&quot;335559739&quot;:160,&quot;335559740&quot;:259}">&#160;</span></p> </div> <div> <p><span data-contrast="none">In line with the lack of a consistent number of historical databases</span><span data-contrast="auto"> we developed the LTEP-BIOCHAR (</span><span data-contrast="none">https://site.unibo.it/environmental-management-research-group/en/activities/long-term-platform</span><span data-contrast="auto">): a specific platform for experimenting with biochar application to soil with the agronomic and environmental purposes such as carbon sequestration, soil erosion, and soil biodiversity in real conditions and over a significant timeframe. The LTEP-BIOCHAR is community-driven resource dedicated to biochar and includes around 22 long-term experiments from Europe, the Middle East, and Africa. The platform aims to list active field experiments, identify methodological gaps in current experiments, suggest new hypotheses, establish a minimum standard of analysis, create a network of expert researchers, support the design of coordinated experiments, and promote the platform at a wider international level.</span><span data-ccp-props="{&quot;201341983&quot;:0,&quot;335551550&quot;:1,&quot;335551620&quot;:1,&quot;335559738&quot;:0,&quot;335559739&quot;:160,&quot;335559740&quot;:259}">&#160;</span></p> </div> <div> <p><span data-contrast="auto">Next steps in research will include collaboration with experts in the domain of pyrogenic carbon from vegetation fires and finding agreement among practitioners on the mean residence time of C-biochar and related measurements (e.g. isotopic signature, loss of ignition, near-infrared spectroscopy). </span>&#160;</p> </div>
<p>Biochar is considered one of the most promising tools to increase soil organic carbon (SOC) sequestration to achieve IPCC climate change targets. Research on the effect of biochar on soil carbon dynamics and its indirect effect on soil moisture through models that need to be extended, tested and validated with long term experiments.</p> <p>Our work aimed at providing a starting point through the integration of two models: Criteria 1D and RothC to account the indirect effect of biochar on SOC due to changes in soil hydrological properties.&#160;</p> <p>In order to account the indirect effect of biochar on soil moisture, we modified the RothC-Biochar (Pulcher et al 2022), a modified version of RothC that account the biochar priming effect and biochar recalcitrance properties, modifying the calculation of Total Soil Moisture Deficit (TSMD), a parameter related to soil moisture in RothC, through the relation between TSMD and &#952; (soil water content) suggested in Farina et al 2013.</p> <p>Thus, we ran the CRITERIA 1D agrometeorological model to estimate the Van Genuchten water retention curve parameter from a multi-year field experiment (2017-2022) in a vineyard in Tebano (Ravenna, Italy),<em> </em>to estimate<em> </em>&#952; from field<em>.</em></p> <p>Since 2017 in Tebano we applied biochar produced from vine clippings and pruning residues. We installed sensors for weather and soil moisture between plots in 2019, with 5TE probes we monitored soil moisture, temperature and conductivity and with MPS1 probes soil matrix potential.</p> <p>We applied a correction on the parameters that regulate the Van Genuchthen water retention curve function in CRITERIA 1D to account the effect of biochar on soil hydraulic properties. Then we compared the data obtained from the field probes with Criteria outputs to verify that the applied correction was accurate; finally, we use the Criteria results as input for RothC-Biochar.</p> <p>The simulation with the modified RothC-Biochar models suggests that applying biochar on agricultural field would result in an increase of 2 tC ha<sup>-1</sup><sub> </sub>of native SOC after 4 years compared to a bare soil due to indirect effect of biochar on soil moisture.</p> <p>&#160;</p>
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