Topsoil composite samples were collected in the study area at a
depth of 0–10 cm, with foreign objects removed. At each point, three
composite samples were obtained. Topsoils were kept in plastic bags,
and once in the laboratory they were oven-dried at 40 °C for 24 h. All
samples were sieved to b2 mm (using a polyethylene sieve) and stored
in darkness until analytical procedures were carried out (Bäckström
et al., 2004).
Plant sampling was performed at the end of summer season when
plants were flowering. Approximately 10 exemplars of each of the
most abundant herbaceous species at each site (including the roots,
stems, leaves) were collected and identified by their scientific names
at the Botanical Museum of IMBiV, CONICET (registration codes from
365854 to 365864).
Samples were divided in two pieces in the field, roots were kept in
plastic bags while shoots (stems and leaves) were kept in paper bags.
Once in the laboratory, they were washed with ultrapure water and then oven-dried at 40 °C to dry weight (DW). For each test site, species,
and plant organ, three composite samples were made with three exemplars
each, and then these were triturated and stored in darkness until
carrying out analytical procedure. The tenth exemplar was registered
in the Botanical Museum herbarium