Master's Theses

Document Type

Thesis - campus only access

Date of Award

Fall 2004

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Karen Hickman

Abstract

Old World Bluestems (OWBs), Bothriochloa ischaemum (L.) Keng and Bothriochloabladhii (Retz.) S.T. Blake, are a group of non-native grasses that have been released and promoted in the central and southern Great Plains. Since the 1920s, millions of hectares or OWBs have been planted for livestock forage, roadside-rights of way, and Conservation Reserve Program fields. OWBs are considered invasive by some authors, but no published research has examined claims that OWBs are superior to natives, somewhat weedy, and invasive. The objectives of Chapter 1 of my thesis were to 1) assess if OWBs spread beyond planted OWB monocultures. 2) estimate rate of OWB spread, and 3) identify any factors related to the presence or absence of spread and factors related to rate of spread. Of the 19 OWB monocultures surveyed, OWB spread was observed beyond the planted boundaries of 18 OWB monocultures. Results suggested a significant relationship between the presence or absence of OWB spread and the land-cover type adjacent to the OWB monoculture. Presence of OWB spread was most common in native rangeland. Mean rate of spread of OWB was estimated at 1.9% of increase per year and 4.4 m per year, but no significant relationships were detected between the variables studied. Because the results from the ground surveys suggested that rangeland adjacent to OWB monocultures were susceptible to invasion at a local spatial scale by OWBs, in Chapter 2, I explored the use of Landsat imagery to distinguish among OWB monocultures, rangeland, and other land-cover types at a landscape scale. Supervised, maximum likelihood classifications were conducted on raw bands for 5 scenes (i.e. May, June, July, August, October) yielding classifications that were better than random. At a 95% probability threshold, the October classification had the highest accuracies followed by June. Together the results of my thesis confirm that OWB can invade native rangeland adjacent to OWB monocultures and suggest that Landsat satellite imagery could provide a means to identify rangeland that is susceptible to invasion by OWBs.

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© 2004 Rachel A. Knight

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