Persistence-related plant traits
During the spring and summer of 2019, we sampled three well-developed
and healthy individual plants per species at each edaphic island (total
sample size = 538; except in a few instances when only two individuals
were available). Trait-data collection and measurement procedures
followed standard protocols (Klimešová et al., 2019; Pérez-Harguindeguy
et al., 2013). We collected seven persistence-related traits linked to
non-acquisitive functions of plants (Table 1). In the field, we scored
maximum plant height and lateral spread (maximum distance between
offspring individuals linked to the parent plant through rhizomes and/or
stolons; for clonal species only). For the other five traits, we
collected plant material in the field to be processed in the laboratory
afterwards. For belowground organ dry matter content (BDMC), a
~2 cm-long portion of either rhizome (for clonal
species) or thick root (for non-clonal species) was cut and put in a
paper bag inside a sealed plastic bag. Fresh weight was recorded, then
the plant material was oven-dried for 72 hours at 60°C, and the dry
weight measured. BDMC was calculated as the ratio between the oven-dry
and fresh mass (similarly to leaf dry matter content [LDMC];
Pérez-Harguindeguy et al., 2013).
Plant anatomical traits – i.e. age, radial growth, storage tissue,
vessel size (Table 1) – were measured for non-clonal species only (346
individuals analyzed overall). In the field, we cut a ~2
cm-long fragment located between the root and stem system from each
sampled individual. This is indeed the oldest plant part present in the
studied growth forms, therefore enables the best estimate of plant age
(Klimešová et al., 2019). These fragments were preserved in 50%
ethanol, and once in the laboratory, sectioned using a sledge
lab–microtome (Gärtner et al., 2015), with thickness between 15 and 40
µm. Cross-sections were then double-stained using a mixture of Astrablue
and Safranin dye, dehydrated (with a series of solutions having
different ethanol concentrations), washed with xylene and fixed on
slides with Canada balsam. These slides were examined at the microscope,
and ImageJ software (Schneider et al., 2012) was used to evaluate the
number of the annual rings (age), mean annual radial growth, percentage
of storage (parenchyma) tissue type, and maximum vessel size in the
cross-section.
TABLE 1 Name (indicating if the trait was collected for clonal,
non-clonal species, or both), definitions (with variable type, units),
relevant functions and key references of the non-acquisitive
persistence-related traits included in this study.