Individual and community flowering phenology, seed counts and pollinator visitation rates in shrub and open plots across Niwot Ridge, 2019 - 2021.

Climate-change induced alterations in environmental conditions in the
alpine tundra has led to the expansion of woody shrubs, known as
“shrubification.” Shrubification is thought to change microclimatic
conditions, potentially leading to changes in plant community
composition. Shrubification has been taking place at Niwot Ridge, a
Long Term Ecological Research site nestled in the mountains of
Colorado, for the past 40 years. Thus far, Niwot Ridge has seen some
change in alpine plant communities due to shrubification, and changes
in plant reproductive capacity and success could lead to future
alterations of community composition. One important aspect in plant reproductive success is the timing of
flowering, known as flowering phenology. Flowering phenology is
controlled partially by environmental conditions, and thus is somewhat
plastic for many species. In the first part of my thesis, I explore
how shrubification may be causing changes in flowering phenology for
21 different plant species in the alpine tundra community at Niwot
Ridge. I conducted an observational study over three years, monitoring
the number of flowers present in 54 pairs of shrub-influenced and open
plots, totaling 108 plots. I found that there is no difference in the
flowering phenology between open and shrub-influenced plots. There is
a measurable difference in the number of flowers produced between
shrub and open plots, with open plots having more flowers on average,
This difference is likely due to there being fewer plants in
shrub-influenced plots. A second aspect explores shrub effects on the reproductive success of
five different alpine species. In the field season of 2021, I took
seeds from these five species from 12 pairs of shrub and open plots,
totaling 24 plots. I counted and weighed the seeds to determine
reproductive success; there was no difference in reproductive success
between shrub and open plots.