Seed production, size and competition in bluebunch wheatgrass Pseudoroegneria spicata.
Abstract
Predicting the effects of climate change on dominant plant species is a pressing challenge for the management and restoration of ecosystems. Knowing how a population has responded historically to climate variability may be a valuable indicator of responses to future climate change. A historical data set showing changes in plant community composition and structure provides a unique opportunity to examine the link between climate and demography for several plant species. When compared with climate records from that region, we can examine the relationship between climate variability and recruitment, growth, and survival. The Adler Lab Group uses this information to fit integral projection modes (IPMs). However, because the historical data sets do not contain information on seed production, the current models assume a linear relationship between plant size and seed production. This project was designed to improve upon the IPMs currently used by the Adler Lab Group by directly observing the relationship between individual size and reproductive output, in the presence and absence of competition. This project focused on bluebunch wheatgrass (Pseudoroegneria spicata), an abundant, perennial grass species. In the field, 60 plants of various sizes were randomly selected and competition was removed around 30 individuals; growth and seed production were monitored for two years following. The resulting data was analyzed using regression models to describe the relationship between seeds, size, and competition. Large plants are more likely to flower than plants in the small or medium size classes, but any plant that flowers, regardless of size class, will produce a comparable number of seeds. Plants were less likely to flower in the absence of competition, possibly as result of non-resource environmental effects. As result of this study, the IPMs used by the Adler Lab Group will include important demographic information for the species bluebunch wheatgrass.
Seed production, size and competition in bluebunch wheatgrass Pseudoroegneria spicata.
Predicting the effects of climate change on dominant plant species is a pressing challenge for the management and restoration of ecosystems. Knowing how a population has responded historically to climate variability may be a valuable indicator of responses to future climate change. A historical data set showing changes in plant community composition and structure provides a unique opportunity to examine the link between climate and demography for several plant species. When compared with climate records from that region, we can examine the relationship between climate variability and recruitment, growth, and survival. The Adler Lab Group uses this information to fit integral projection modes (IPMs). However, because the historical data sets do not contain information on seed production, the current models assume a linear relationship between plant size and seed production. This project was designed to improve upon the IPMs currently used by the Adler Lab Group by directly observing the relationship between individual size and reproductive output, in the presence and absence of competition. This project focused on bluebunch wheatgrass (Pseudoroegneria spicata), an abundant, perennial grass species. In the field, 60 plants of various sizes were randomly selected and competition was removed around 30 individuals; growth and seed production were monitored for two years following. The resulting data was analyzed using regression models to describe the relationship between seeds, size, and competition. Large plants are more likely to flower than plants in the small or medium size classes, but any plant that flowers, regardless of size class, will produce a comparable number of seeds. Plants were less likely to flower in the absence of competition, possibly as result of non-resource environmental effects. As result of this study, the IPMs used by the Adler Lab Group will include important demographic information for the species bluebunch wheatgrass.