Dissertation
Demography and individual growth of two introduced Bromus species
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2010
DOI:
https://doi.org/10.7273/000006007
Abstract
Comparative studies of congeners have been identified as valuable tools to understand why some introduced species become invasive and others do not. I compared individual and population growth characteristics of two annual grasses, invasive Bromus tectorum and naturalized B. briziformis, in greenhouse and field experiments. Smaller pot size, lower water availability and lower rates of nutrient addition all reduced maximum plant size, decreased growth rates, and delayed the period of most rapid plant growth of both species in greenhouse studies. Ontogenetically controlled analyses of biomass allocation revealed that plants had higher root to shoot ratios in less favorable growing conditions (limited soil volume or low nutrient addition), compared to more favorable growing conditions. B. tectorum biomass allocation was more root-heavy compared to B. briziformis biomass allocation in all treatments. Neither species adjusted its allocation to roots in response to water availability but greater root allocation by B. tectorum compared to B. briziformis throughout development may increase the drought tolerance of that species. I used logistic and linear regression analysis of matrix population-model parameters to examine the response of B. tectorum and B. briziformis population growth rates to individual plant nitrogen and water status at two sites. B. tectorum population growth rates were 2 to 3.5 times greater than B. briziformis growth rates across water and nutrient treatments, and across study sites. B. tectorum plants were larger than B. briziformis plants, had lower leaf nitrogen content and produced nearly three times as many seeds as B. briziformis plants. Fertilized plants were larger and produced more seeds than unfertilized plants, but only at one site. Watered plants were more depleted in 13C than unwatered plants only at one site. However, fertilizer and water treatment effects on plant size, seed production, or [delta]13C did not translate into differences in population growth rates. Population growth rates differed only by species and sites.
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Details
- Title
- Demography and individual growth of two introduced Bromus species
- Creators
- Paul A. Rabie
- Contributors
- Raymond W. Lee (Chair)Raymond W. Lee (Committee Member)J R Alldredge (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Biological Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 139
- Identifiers
- 99901055025301842
- Language
- English
- Resource Type
- Dissertation