Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 2000 Floristic analysis of central Iowa woodlands, and comparison of reproduction and regeneration in common and restricted herbaceous species Catherine Mary Mabry Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Ecology and Evolutionary Biology Commons, and the Environmental Sciences Commons Recommended Citation Mabry, Catherine Mary, "Floristic analysis of central Iowa woodlands, and comparison of reproduction and regeneration in common and restricted herbaceous species " (2000). Retrospective Theses and Dissertations. 12350. https://lib.dr.iastate.edu/rtd/12350 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. 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Farrar Iowa State University Ames, Iowa 2000 Copyright © Catherine Mary Mabry, 2000. All rights reserved. UMI Number 9990476 UMI^ UMI Microfomi9990476 Copyright 2001 by Bell & Howell Infomiation and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. Bell & Howell Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Artxir, Ml 48106-1346 ii Graduate College Iowa State University This is to certify that the Doctoral dissertation of Catherine Mary Mabry has met the dissertation requirements of Iowa State University Signature was redacted for privacy. Major Professor Signature was redacted for privacy. For^ Signature was redacted for privacy. For ^ Gradibte College iii My dissertation is dedicated to my mom, Mary Catherine Mabry, 1930-1999. She was faithful in her support of my long education, and shared her love for the beauty of nature with me. iv TABLE OF CONTENTS ACKNOWLEDGMENTS v ABSTRACT vi CHAPTER 1. GENERAL INTRODUCTION 1 CHAPTER 2. ENVIRONMENTAL GRADIENTS AND HUMAN 9 DISTURBANCE IN CENTRAL IOWA WOODLANDS CHAPTER 3. EFFECT OF CATTLE GRAZING ON WOODLANDS IN 54 CENTRAL IOWA CHAPTER 4. PLANT TRAITS IN RELATION TO 82 ENVIRONMENMENTAL FACTORS AND HUMAN DISTURBANCE IN A TEMPERATE WOODLAND CHAPTER 5: REPRODUCTIVE OUTPUT AND ALLOCATION OF 127 COMMON VERSUS RESTRICTED WOODLAND HERBACEOUS SPECIES IN CENTRAL IOWA, U.S.A. CHAPTER 6. SEED VL\BILITY AND EMERGENCE IN 145 WOODLAND HERBACEOUS SPECIES IN CENTRAL IOWA, U.S.A. CHAPTER 7. GENERAL CONCLUSIONS 163 V ACKNOWLEDGMENTS My research for this dissertation was funded primarily by the Leopold Center for Sustainable Agriculture at Iowa State University, with additional assistance from The Iowa Department of Natural Resources (State Preserves Advisory Board), The Iowa chapter of The Nature Conservancy and Trees Forever. Without their generous support this research would not have been possible. Support from the graduate college (Leopold Brown Trust Fellowship) and the program in Ecology and Evolutionary Biology (Scholarly Excellence Fellowship) provided me with valuable time to write my dissertation. I would like to thank Brad Atchison, Joe Dixon and Becky Mack for their help in sampling plots, Becky Mack and Michelle Ritchey for help with weighing and counting seeds, and Michelle Ritchey for tirelessly pushing plastic straws into the ground. I appreciate Bill Norris and Eddie Watkins for their illuminating and sometimes entertaining discussions. My committee members, Diane Debinski (Animal Ecology), Philip Dixon (Statistics), Tom Jurik (Botany) and Kirk Moloney (Botany) were generous in their comments and made many helpful improvements to the manuscripts. The staff of the ISU Botany Office (Joanne Nystrom, Joyce Hanson, Sharon East and Christina Gallop) was always kind, even when I exasperated them. I especially thank Larissa Mottl for sharing her enthusiasm and interest in forests and restoration ecology. Her excitement and appreciation for the beauty of the woods have been an inspiration to me. I am very grateful for Don Farrar, my major professor. I came to ISU looking for a mentor, £md I found a great one in Don. I admire his breadth of knowledge, opermess to new ideas, and kindness towards me and other students. Finally, I thank my husband, Clark McMulIen, for his love and patience. vi ABSTRACT I studied the distribution and abundance of the plant species of forests in central Iowa, with particular emphasis on the differences in species composition between sites currently or recently grazed by cattle verstis those that had not been grazed for over 50 years. In order examine some of the potential mechanisms underlying the distribution and abundance of species, 1 scored each species for 29 categories of fimctional and morphological traits. I then used these traits to identify groups of species that potentially flmction in a similar marmer (irrespective of taxa), to examine the distribution of traits along the major environmental gradients, and to address whether species' fi^uency was correlated with any of the traits. Finally, in order to imderstand in more detail the difference between species that were common compared to those relatively less common (restricted species), I examined whether the two groups of species differed in reproductive output and allocation, seed viability, and seedling emergence. Understory species and canopy trees were generally distributed along the same environmental gradients; landform, soil phosphorous and nitrogen content, and disturbance and woodland size. The understory vegetation of small woodlands indicated that they were high quality remnants, while weedier and more common understory species were associated with grazed sites. The trees that are canopy dominants appeared to have a homogeneous distribution. Species of oak were not regenerating well. The matched pairs study identified a distinct group of understory species associated with ungrazed and grazed sites. Ungrazed woods had no exotic species and had more species of perennial herbs, herbs with extensive rhizomes, and species characteristic of moist forests with closed canopies, habitats lacking human disturbance, and with ranges restricted to the eastem United States, hi contrast, 30 percent of species associated with grazed woods were exotic, and the species associated with these sites were more likely to be annuals, have little or no vegetative spread, to occur in a wide variety of habitats, and to have a cosmopolitan distribution. The strongest effect of grazing on tree species was the reduction in number of seedlings found in grazed woods. Most of the variation in the ordination of plots by traits was found on axis 1, which separated woods based on grazing history and size. The traits associated with ungrazed and smaller woods included preference for undisturbed, moist and low light habitats, very low stature, flowering in the earliest part of spring, presence of root storage and ant dispersal. Traits associated with a lighter canopy and grazing were largely those that define annuals and shrubs and included a preference for high or low moisture and light, tolerance of human disturbance, small seed size, relatively seed production, low frequency of occurrence and non-natives. Linkages between traits and environment were identified, but the data suggested that the groups identified by TWINSPAN are not acting the functional groups in this community. Although other groupings of species acting as functional likely occur, particularly in relation to strong gradients, e.g. different grazing history, there are a number of reasons to be cautious before concluding that a small number of key characters define functional