1. INTRODUCTION
Páramos are a collection of high-mountain ecosystems dominated by grasslands, wetlands and shrublands (Tovar, Arnillas, Cuesta, & Buytaert, 2013). Usually, the characteristic saturated soils originate a variety of peatlands and lakes (J. C. Benavides, 2015). Páramos are located in the northern Andes in South America at elevations above the tree line (3,000–3,500 meters above sea level – m a.s.l.) and below the snow line (4,500–5,000 m a.s.l.) (Podwojewski, Poulenard, Zambrana, & Hofstede, 2002). Their climate is cold with highly variable temperature and rainfall in both time and space (Buytaert et al., 2002; Ochoa-Tocachi et al., 2016). Páramo soils have a friable and crumbly consistency, an open structure (Buytaert, Deckers, & Wyseure, 2006), and high organic matter content that generates a high porosity (Buytaert et al., 2002).
Overall, soil properties, natural vegetation and hydrological conditions equip páramos with a high capacity to store excess water during wet seasons and sustain flows during scarce dry seasons (Buytaert, Célleri, et al., 2006). This capacity to provide a seasonal buffer of water flows is known as hydrological regulation (Minaya, Corzo, Solomatine, & Mynett, 2018) or streamflow buffering (Patiño et al., 2021). Streamflow buffering is considered a crucial hydrological ecosystem service provided by páramos (Buytaert & Beven, 2011), contributing to water availability for over 100 million people in downstream Andean communities (Flores-López, Galaitsi, Escobar, & Purkey, 2016).
On the other hand, páramos have traditionally been inhabited by communities of small farmers (estimated at around 10 million people) whose livelihoods are strongly dependent on the ecosystem biophysical characteristics (Hofstede, 2013). One of the main activities is agriculture, which replaces the native páramo vegetation with seasonal crops leading to changes on their soil hydrophysical properties including structure, porosity, organic matter content and water retention capacity, and thus altering hydrological processes (Avellaneda-Torres, León Sicard, & Torres Rojas, 2018; Buytaert, Célleri, et al., 2006). For example, the generally saturated páramo soils are drained using trenches to allow drier conditions for cultivation (Ochoa-Tocachi et al., 2016). Similarly, soil compaction and structure degradation by tillage and sun exposure reduce its water retention capacity and increase surface runoff (Poulenard, Podwojewski, Janeau, & Collinet, 2001). Likewise, the removal of natural vegetation increases evapotranspiration and affects soil structure and porosity (Cárdenas-Agudelo, 2016) and produce hydrophobicity (Buytaert, Wyseure, De Bièvre, & Deckers, 2005). Consequently, land use and management are key influencers of the hydrological cycle in páramos and of the hydrological ecosystem services that they provide (Buytaert et al., 2002).
Although páramos are regionally important, they are still understudied. Most research has been carried out in the humid páramos of southern Ecuador and western Colombia, whereas dry páramos have been neglected (Correa et al., 2020). In the last two decades, research has addressed the impacts of land use change on: i) the soil hydrophysical properties (Buytaert et al., 2002; Daza-Torres, Hernández, & Triana, 2014; Poulenard, Podwojewski, & Herbillon, 2003); ii) hydrological regulation (Buytaert et al., 2005; Poulenard et al., 2001); and iii) water provision (Buytaert, De Bièvre, Wyseure, & Deckers, 2004; Ochoa-Tocachi et al., 2016). However, the spatial variability of climatic, hydrologic and soil conditions of these ecosystems yield equally variable results. This shows the complexity in the quantification of land use change impacts and the need to undertake specific studies that answer local questions and support local development (Ochoa-Tocachi et al., 2018), particular un sub-represented, understudied ecosystems such as the dry páramos or the Andean punas.
This study analyses the effect of changing natural páramo vegetation to agricultural crops (fallow, spring onion crops and potato crops) on soil hydrophysical properties associated to the hydrological service of streamflow buffering (i.e., soil organic matter, bulk density, pH and electric conductivity). Additionally, we studied the effect of rainfall pattern (i.e., wet season and dry season) over the studied hydrophysical properties. This research was carried out in a dry páramo study site (annual rainfall <1,196 mm) (Rangel, 2000), which is particular among páramos. Dry páramos cover only 6.0% and 1.4% of the páramo areas in Colombia and Ecuador, respectively (Hofstede, 2013), although larger areas of páramos are considered to resemble similar drier conditions than those of humid páramos. To the best of the authors’ knowledge, research carried out in these particular conditions has been scarce. Thus, this paper contributes to an increased understanding of the complexity of Andean páramos and provide crucial information to improve land use management, a key aspect for ensuring the sustainable provision of hydrological services generated by these strategic ecosystems.