Thesis
Long-term population census and nest site characterization of managed alkali bee population in alfalfa seed production in south central Washington state
Washington State University
Master of Science (MS), Washington State University
2018
Handle:
https://hdl.handle.net/2376/103740
Abstract
Alkali bees are the world's only intensively managed soil-nesting bee, and they have been managed for alfalfa seed pollination in Walla Walla County, Washington State, USA for more than 60 years. Surface quadrat counts were used to estimate the population of nesting females in 13 alkali bee beds from 2010 to 2017. From 2010 to 2017, there was no significant change in the average nesting density among the 13 beds. For three of the 13 beds, survey data was obtained for an earlier 7-year period, providing 15 years of observations. Population abundance in all three beds increased significantly over the 15-year period. There has been little study of the ideal properties of alkali bee nesting habitat. Soil cores were taken in 13 bee beds in 2015 and 2016 in conjunction with the alkali bee population survey. Gravimetric soil moisture content, electrical conductivity, and pH were measured at four depth increments and compared to the number of surface nest holes. Soil compaction measurements were taken in conjunction with the population survey in 2017. Soil moisture and pH in the 0-10cm and 10-20cm depth increments had a significant positive relationship to surface nest density. Electrical conductivity had a significant negative correlation with nest density. There was a significant interaction between soil moisture and electrical conductivity. There was a significant positive relationship between soil compaction and nest density at 0cm depth, and a significant negative relationship between soil compaction and nest density at 10cm depth. The presence of a compact layer at 5cm depth appears to impact surface soil moisture. Results of comprehensive soil testing suggest that beds with a higher proportion of divalent cations to monovalent cations have less risk of developing a compact soil layer at 5cm depth.
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Details
- Title
- Long-term population census and nest site characterization of managed alkali bee population in alfalfa seed production in south central Washington state
- Creators
- Emily H. Wine
- Contributors
- Douglas B. Walsh (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Entomology, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525052101842
- Language
- English
- Resource Type
- Thesis