Land use change dynamics in two contrasting andalusian mediterranean watersheds (1977 2022) and their effect on SOC stocks.

Abstract

Mediterranean region, according to the latest IPCC report, is particularly vulnerable to the impacts of climate change. This vulnerability is exacerbated by intense human activity and frequent changes in land use, leading to a notable increase in erosion and degradation processes. As a direct consequence, there is a decline in soil health and, within it, the capacity to retain organic carbon is reduced. In this context, this study aims to: (i) analyze changes in land use over the past decades (1977-2022); (ii) estimate which land uses have a higher soil of organic carbon (SOC) stocks through the collection and analysis of a total of 145 soil samples; (iii) assess the link between current SOC stocks and land use dynamics in recent years; (iv) evaluate the importance of climatic characteristics in SOC stock; (v) generate detailed SOC stocks mapping using Random Forest. For this purpose, two small Andalusian Mediterranean watersheds with contrasting climatic conditions have been selected: on one hand, a watershed (C1, Arroyo de la Pindolita – Valle del Río Genal) characterized by a subhumid Mediterranean climate (±700 mm of annual rainfall); on the other hand, a watershed (C2, Rambla del Serrón – Campo de Tabernas) with arid conditions (±150 mm of annual rainfall). The results show how the contrasting dynamics in land use changes and climatic conditions, especially rainfall, determine a highly differential behavior between the two watersheds. C1, mainly occupied by agricultural land and with a high dynamism in land use changes, has higher SOC stocks, a fact clearly conditioned by climatic characteristics favoring a biostasis situation. Meanwhile, C2 has seen a significant increase in built-up areas and land dedicated to irrigation crops, especially in recent years, identifying generally low SOC stocks.