Development of a Multi-Year Soil Organic Carbon (SOC) Database for the Ecological Park La Joya–La Barreta, Queretaro, Mexico (2023–2025)

The Municipality of Querétaro is one of the 18 municipalities that make up the state of Querétaro, Mexico. The municipality is located in the southwestern part of the state, with extreme coordinates between 20°30' and 20°56' N latitude, and 100°17' and 100°36' W longitude, covering a territorial extension of 690 km². The La Joya-La Barreta Ecological Park is located within the municipality of Querétaro, in central Mexico (between 100°17’ and 100°36’ west longitude and 20°30’ and 20°56’ north latitude), and is part of the municipal Protected Natural Area known as the Western Micro-watershed Zone. The predominant climate is temperate semi-arid. It covers an area of 247.91 hectares. SamplingSampling sites were selected considering the different landcover scenarios as the possible main sources of soil organic carbon (SOC) variation. At each site, four composite soil samples (each one divided into four axes, according to the four cardinal directions) were collected at a depth of 0-30 cm of mineral soil using an auger method. .The determinations of the soil properties were performed in the Soil Science Laboratory of the Institute of Geosciences of the UNAM, following the methodology recommended by the Official Mexican Standard NOM-021-RECNAT-2000 (SEMARNAT, 2002). SOC is estimated as a fracton of organic matter that was determined using the Walkey and Black (1934) method. This method obtains the COS from oxidizable carbón; a correction factor of 1.298 is used, equivalent to assuming a recovery of 77%. Bulk density (BD) was determined using the known-volume cylinder method, the physical standard for assessing soil mass per unit volume under undisturbed field conditions. This procedure involved extracting soil cores using metal cylinders, which were then oven-dried at 105 °C until a constant weight was reached, following the protocols established by Blake and Hartge (1986). Accurate BD measurement is critical for soil health modeling, as it serves as the fundamental conversion parameter for transforming organic carbon concentrations obtained in the laboratory into mass per unit area values, allowing for a realistic quantification of carbon stocks in the evaluated profile. Additionally, the percentage of rock fragments (RF) was quantitatively determined during the sample preparation and sieving phase, separating the mineral fraction with a diameter greater than 2 mm from the fine soil. Estimating the fractional residue (FR) is essential for adjusting volumetric soil calculations, since these coarse particles occupy a significant space in the soil matrix but have little to no capacity for soil organic carbon (SOC) storage (Schoeneberger et al., 2012). Therefore, integrating bulk density (BD) and stoniness allows for a robust estimation of SOC stores, avoiding overestimation bias in stony soils and ensuring the comparability of results under international technical frameworks for land degradation monitoring. Files: barr23-25.csv - The database of three samplig years with a total of 146 records. It contains the coordinates (X, Y), soil organic carbon (C), bulk density (DA), rock fragments (FRAG.ROC), and sampling year (YEAR). For 2023, the database contains 99 records, 16 for 2024, and 31 for 2025. Ecological Park La Joya-La Barreta, Queretaro, Mexico. Read me.txt - Contains the database description and methodology. This files support the study of Torres-Gómez et al., "Development of a Multi-Year Soil Organic Carbon (SOC) Database for the Ecological Park La Joya–La Barreta, Queretaro, Mexico (2023–2025)" submitted in Geoscience Data Journal. March 2026. Authors acknowledge support from UNAM PAPIIT, (Grant / Award Number: 'IV200223'). Authors acknowledge support from the Instituto de Ecología del Municipio de Queretaro. Mariano Torres-Gómez is grateful for the funding of his postdoctoral stay carried out by the Postdoctoral Fellowship Program at the National Autonomous University of Mexico (UNAM-DGAPA).