Dissertations and Theses @ UNI

Availability

Open Access Thesis

Keywords

Grasses--Seeds--Mortality--Iowa; Grasses--Iowa--Seedlings--Growth; Prairie restoration--Iowa;

Abstract

The large cost of seed and low seedling establishment rates make restoring native tallgrass prairies expensive and difficult. Tallgrass prairie restorations typically achieve seedling emergence rates of only 10%. This begs the question of what happens to the remaining 90% of seeds that do not emerge as seedlings. This thesis sought to assess or quantify the importance of seed predators and death by microorganisms or to senescence on seed survival and seedling establishment within a newly planted native tallgrass prairie restoration under typical restoration conditions. I hypothesized that small vertebrate seed predators would play be detrimental to overall seedling emergence and would shift species composition in favor of smaller seeded species in newly restored areas. A second hypothesis was that the recovery rate of seeds within the soil seed bank and the viability of recovered seeds would decrease over time due to natural decay and death. To explain these questions I used an above- and below-ground approach. The above-ground approach used sham and closed exclosures to measure the amount of seedling emergence and loss to small vertebrate granivores at three sites. The below-ground seed fates approach attempted to measure the loss of seeds and viability of four prairie species over three sampling dates. The above-ground approach found that small vertebrate predators had a significant effect on overall seedling establishment but did not affect species composition regardless of response variable: percent emergence, seedlings emerged/g planted, and the difference in seedling emergence between the sham and closed exclosure. The below- ground approach found that, while each species varied, the overall percent recovery declined and the viability of the recovered seeds decreased over time. Though the fate of many seeds was unknown, my results suggest that granivores significantly reduce seedling emergence. By excluding small vertebrate granivores, my study was able to increase overall seedling emergence by four percent or 17 seedlings/m2 which could result in fewer seeds planted and hundreds of dollars saved in future restorations. Further studies should test methods to reduce predation by small vertebrate granivores, focusing on methods that are feasible for practitioners. It is also important to investigate the causes of as yet unknown seed losses. This thesis has demonstrated that there is still more work that needs to be done and questions to be answered about seed loss to above- and below-ground sources in tallgrass prairie restorations.

Year of Submission

2014

Degree Name

Master of Science

Department

Department of Biology

Department

Tallgrass Prairie Center

First Advisor

Laura L. Jackson

Date Original

2014

Object Description

1 PDF file (ix, 69 pages)

Language

en

File Format

application/pdf

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