Francisco Navarro‑Rosales, Jesús Fernández‑Habas, Lizardo Reyna‑Bowen, José A. Gómez, Pilar Fernández‑Rebollo
Incorporating trees into agricultural systems, including grasslands, increases the soil organic carbon sequestration and contributes to climate change mitigation. Site preparation for tree establishment is a common practice that can involve a variety of techniques and agricultural implements such as subsoiling. This study aimed to evaluate the long-term efects of subsoiling on soil organic carbon (SOC) concentrations and stocks in a Mediterranean grassland aforested with holm oaks 22 years ago and now converted into a Dehesa agroforestry system. The study was conducted in a dehesa farm in Southwest Spain. Soil samples were taken at six depths under 10 tree canopies within and outside the original subsoiling line. Subsoiling signifcantly decreased SOC concentration. Mean SOC concentration in the first 20 cm was 30% lower at the subsoiling line. SOC stocks for the first 60 cm were 2660 g m−2 within the subsoiling line and 4320 g m−2 outside the line. There was a clear reduction in SOC concentration and stock with increasing depth. Root abundance and deeper rooting increased with subsoiling but did not translate into sufcient carbon accumulation in the soil, which is moderate even after 22 years. This study reveals that, in the long term, there is a trade-of in CO2 sequestration between tree planting and soil subsoiling, highlighting the need for further research into the
potential benefts and detriments of subsoiling.
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