DOI: 10.5061/dryad.crjdfn38j
title: Data for: Prescribed fire increases plant-pollinator network robustness to losses of rare native forbs

description: Restoration efforts often focus on changing the composition and structure
 of invaded plant communities, with two implicit assumptions: 1) functional
 interactions with species of other trophic levels, such as pollinators,
 will reassemble automatically when native plant diversity is restored; and
 2) restored communities will be more resilient to future stressors.
 However, the impact of restoration activities on pollinator richness,
 plant-pollinator interaction network structure, and network robustness is
 incompletely understood. Leveraging a restoration chronosequence in
 Pacific Northwest prairies, we examined the effects of restoration-focused
 prescribed fire and native forb replanting on floral resources, pollinator
 visitation, and plant-pollinator network structure. We then simulated the
 effects of plant species loss/removal scenarios on secondary extinction
 cascades in the networks.  Specifically, we explored three
 management-relevant plant loss scenarios (removal of an abundant exotic
 forb, removal of an abundant forb designated a noxious weed, and loss of
 the rarest native forb) and compared them to control scenarios.
 Pyrodiversity, proportion of area recently burned, and cumulative
 replanting effort (plugging and seeding) over the prior 10 years increased
 the abundance and diversity of floral resources, with concomitant
 increases in pollinator visitation and diversity. Pyrodiversity also
 decreased network connectance and nestedness, increased modularity, and
 buffered networks against secondary extinction cascades.  Rare
 forbs contributed disproportionately to network robustness in less
 restored prairies, while removal of typical “problem” plants like exotic
 and noxious species had relatively small impacts on network robustness,
 particularly in prairies with a long history of restoration activities.
 Restoration actions aimed mainly at improving the diversity and abundance
 of pollinator-provisioning plants may also produce plant-pollinator
 networks with increased resilience to plant species losses.
description: We performed floral patch-focused observation at approximately
 the same seasonal time points as the floral density data were collected.
 For each forb species that flowered at a site, we selected an observation
 patch by choosing a random transect number to provide a general location
 in the field, then located the nearest floral patch for the target species
 where the number of observable flowering units exceeded a minimum of 20
 within an estimated area of approximately 2 m<sup>2</sup>. We
 used this threshold to reject very low-density forb species for which
 visual display was unlikely to attract pollinators. Observers performed
 15-minute timed observations when temperatures were between 15º and 30º C,
 humidity was above 20%, and wind speed was less than 3 m/s. Observers
 captured and dispatched all insect visitors that contacted stamens or
 stigmas. Lepidoptera and queen bumble bees were excluded from captures and
 were identified on the flower, due to conservation considerations. Timing
 was paused during specimen handling. Two observations were performed for
 every forb species at a site at each time point, carried out by different
 observers and with different diurnal timing to the greatest degree
 possible. Specimens were later identified to the lowest taxonomic level
 possible by taxonomic experts (e.g., genus or species for most bees and
 flies).
description: Data files can be accessed using Excel.