Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Wildlife and Fisheries Science

First Advisor

Daniel E. Hubbard


The Conservation Reserve Management Access Program (CRP-MAP) is a joint effort of the Nebraska Game and Parks Commission and Pheasants Forever of Nebraska that seeks to address brood habitat needs of pheasants (Phasianus colchicus) and other grassland birds by light disking and interseeding legumes into portions of aging CRP fields. The program has two specific goals - increasing the total invertebrate availability as a food source for pheasant chicks and increasing the structural complexity of vegetation. This study compares invertebrate biomass and structural complexity of vegetation in treated (disked and interseeded with legumes) and idle portions of CRP-MAP fields to determine the success of the program in meeting these goals. The study was conducted on 10 existing CRP-MAP sites in eastern Nebraska spanning a two-year period. In addition to effects of treatment, this study compared two different covertypes - CP1 (predominantly cool-season introduced grasses) and CP2 (predominantly warm-season native grasses). Invertebrates were sampled by sweepnetting from mid-May through early August. Vegetation characteristics were analyzed using visual obstruction reading and canopy coverage estimates. Percent canopy coverage of legumes and total forbs were greater in interseeded than in control fields during both years as was vegetation species richness. Although no differences were detected in percent grass coverage by treatment, smooth brome (the dominant species in CP1) was significantly lower in interseeded than in control fields. Similar trends were seen in big bluestem and switchgrass (the dominant CP2 species). Total invertebrate biomass results varied by covertype. Total invertebrate biomass was 531.6 mg in control CP2 as compared to 2757.7 mg in interseeded CP2. No differences were detected by treatment in CP1. Mean invertebrate abundance reflected similar trends as differences were detected in CP2 only. Mean invertebrate biomass per individual was higher in interseeded fields than in control fields of both covertypes. These results indicate that, in enrolled fields, the program is increasing vegetation structural complexity and meeting program goals. The program is also meeting its goals in increasing invertebrate biomass for chicks in CP2 covertypes. Invertebrate biomass may be relatively high in CP1 prior to CRP-MAP management practices and the program is not meeting invertebrate goals in this covertype. The benefits to vegetative structure are sufficient to justify continued program enrollment of CP1 as long as enrollment demand remains below program funding. If demand exceeds funding, however, NGPC biologists should focus enrollment efforts on CP2 to better meet both the vegetative and invertebrate enhancement goals of the program.

Library of Congress Subject Headings

Invertebrates -- Nebraska
Habitat conservation -- Nebraska
Grassland ecology -- Nebraska


Includes bibliographical references (page 49-55)



Number of Pages



South Dakota State University


Copyright © 2003 Ronald J. Leathers. All rights reserved.