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.