Exploring the Effects of Shrubification on the Community-level Flowering Phenology and Reproductive Success of Alpine Plants

Seaver, Micaela

Graduate Thesis Or Dissertation

Exploring the Effects of Shrubification on the Community-level Flowering Phenology and Reproductive Success of Alpine Plants Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/6h440t77s

Abstract

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. The second part of my thesis 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. Future research can expand on the foundation this thesis lays, conducting studies over a longer period of time and looking at different aspects of shrubification.

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