Add-ons to the standardized protocol
In addition to long-term monitoring of plant communities, the MIREN
survey design is well suited for additional projects (‘add-on’ projects)
that test more detailed or region-specific questions about the drivers
of plant species redistributions. For example, soil temperatures have
been recorded with a high temporal resolution for a year or longer in
several MIREN regions to document how disturbance along roadsides
affects microclimate, including consequences for species redistributions
(for the first regional results see Lembrechts et al., 2019). Plant
functional traits have additionally been collected for species in
Tenerife, Canary Islands, to assess contrasting patterns of
intraspecific trait variability of native and non-native species and the
change of community mean traits and functional diversity with elevation
(Kühn et al., 2020). Another add-on project has focused on soil chemical
properties and mycorrhization of native and non-native species in the
mountains of Norway (Clavel et al., 2021), and survey plots have also
been used to assess the distribution of plant pathogens
(Phytophthora species) in Australia (Khaliq, 2019). Once
participants begin contributing data to the MIREN global road survey
database, they can suggest add-on studies to apply across all regions
that go beyond the existing scope of the survey protocol – as long as
it is based on a standardized protocol that is fast, simple and low cost
to implement by collaborators. To maximize participation and to discuss
new proposals, data quality and complementarity, ideas for add-on
projects should be developed together with the MIREN steering committee.