Study area
The Tandilia Mountains extend along a 350 km long diagonal in the
Province of Buenos Aires (Argentina), covering the districts of Azul,
Balcarce, Benito Juárez, General Pueyrredón, Lobería, Necochea,
Olavarría and Tandil (figure 1). The maximum width is in its central
part and reaches an extension of 63 km, and the maximum height is 525 m
(Cerro la Juanita, Benito Juárez district). The whole region occupies an
area of approximately 1.231.400 ha, including scattered hills separated
by valleys and plains (Herrera et al., 2019). The agricultural expansion
and other anthropogenic activities (such as mining), added to the lack
of natural protected areas (Nanni et al., 2020), produce changes in
grassland species richness, composition, and abundance, and the increase
of exotic species (Filloy & Bellocq, 2007). Of a total of 505 plant
species that have been found in the Highland grassland of the Pampa, 139
are exotic (27%) (Sánchez & Núñez, 2004; D’Alfonso et al., 2014).
Despite the significant impact, the Tandilia Mountains continue to be
considered one of the last refuges of Pampa grassland and one of the
most biodiverse sites in the Province of Buenos Aires (Chebez, 2005;
Pedrana et al., 2008).
Due to the fragmentation of this habitat, the Pampa grassland has been
relegated to remnants of different sizes, mainly on hills where the
presence of rock and shallow soils makes it impossible to use plows to
cultivate annual crops (Herrera & Laterra, 2007). However, other
activities, such as quarrying and forestry, remain as important threats.