Presentation Title

Influence of water availability on native wildflower phenology and pollinator attractiveness

Abstract

In 2017 and 2018, we performed a field study screening 23 garden-friendly, native Willamette Valley wildflowers (and four exotic comparators) for their attractiveness to pollinators. Flower phenology and pollinator visitation differed between the two seasons. There was a marked difference in both flowering timing and duration. The 2017 peak bloom began an average of 17.7 days later than 2018, and ceased 27.7 days later. Thus, the length of 2018 peak bloom was 10 days shorter on average, and ended a month earlier. We hypothesize that these differences are due to water availability. In 2017, we irrigated to ensure perennial establishment, while in 2018 we did not irrigate. Furthermore, in 2017 the region received 2.83 inches of rain across May-August, whereas in 2018 there was only 0.87 inches of rain in May-August. This may have accelerated flowering and attenuated its length. These phenological differences may have implications for the abundance and species-richness of attracted pollinators. In 2018, flowers opened earlier and for a shorter duration on average. However, across our timed pollinator counts we observed more native bee visitors per observation. When considering native bees, Gilia capitata, Madia elegans, Aster subspicatus, Eschscholzia californica, and Solidago canadensis attracted the greatest bee abundance in 2017. In 2018, Eschscholzia californica, Aster subspicatus, Phacelia heterophylla, Solidago canadensis, and Clarkia amoena were the most attractive to native bees. During our 2019 field season we will irrigate half the plots, to address both temporal variation and the impact of irrigation on bloom phenology and attractiveness.

Subjects

Habitat restoration, Plant ecology, Wildlife biology

This document is currently not available here.

Share

COinS
 

Influence of water availability on native wildflower phenology and pollinator attractiveness

In 2017 and 2018, we performed a field study screening 23 garden-friendly, native Willamette Valley wildflowers (and four exotic comparators) for their attractiveness to pollinators. Flower phenology and pollinator visitation differed between the two seasons. There was a marked difference in both flowering timing and duration. The 2017 peak bloom began an average of 17.7 days later than 2018, and ceased 27.7 days later. Thus, the length of 2018 peak bloom was 10 days shorter on average, and ended a month earlier. We hypothesize that these differences are due to water availability. In 2017, we irrigated to ensure perennial establishment, while in 2018 we did not irrigate. Furthermore, in 2017 the region received 2.83 inches of rain across May-August, whereas in 2018 there was only 0.87 inches of rain in May-August. This may have accelerated flowering and attenuated its length. These phenological differences may have implications for the abundance and species-richness of attracted pollinators. In 2018, flowers opened earlier and for a shorter duration on average. However, across our timed pollinator counts we observed more native bee visitors per observation. When considering native bees, Gilia capitata, Madia elegans, Aster subspicatus, Eschscholzia californica, and Solidago canadensis attracted the greatest bee abundance in 2017. In 2018, Eschscholzia californica, Aster subspicatus, Phacelia heterophylla, Solidago canadensis, and Clarkia amoena were the most attractive to native bees. During our 2019 field season we will irrigate half the plots, to address both temporal variation and the impact of irrigation on bloom phenology and attractiveness.