Distribution analysis of organic carbon and CO2 fluxes along soil profile to explore alternative methodologies for soil respiration measurements

This work is a part of PRIN project “New Digital Technologies for full carbon accounting of forests and woody crops” aiming to investigate technological innovations for real time monitoring the 3-D structure of trees, leaves developments, diameter growth and soil GHG exchanges, in order to develop a new Forest and Woody crops Digital Twins, which could become standards for carbon and GHG accounting. In this context, forest ecosystems and fruit tree orchards will be studied, that play a fundamental role as carbon sinks. Understanding the carbon distribution and respiratory flows along profile is part of an overall carbon accounting picture that is currently fundamental to determine the contribution of terrestrial ecosystems to carbon sequestration, according with all the carbon farming measures and mitigation measures implemented in the Farm to Fork Strategy. In this study, we defined the distribution of organic carbon and CO2 fluxes along soil profile in an olive grove of Central Italy (VT), under organic farming for the last nine years (no irrigation, fertilization or soil tillage), in order to explore alternative methodologies of soil respiration measurements based on CO2 gradient technology rather than closed accumulation chambers. Data from this study were preliminary to the phase of future insertion of CO2 sensors along soil profile. In the top soil layer, high values of respiration and microbial carbon were found, whereas the deep soil layers (10-40 cm) had a reduced microbial carbon and activity (about by 73% and 90%), and a lower organic C content (about by 80%) compared to top layer. The striking thing of these preliminary results is that, also in organically managed soil for several years, biological activity and organic C are relegated to the most superficial layer, and CO2 fluxes from deep soil remains low even when stimulated by ideal conditions of humidity and temperature.