Category: Theses and Dissertations
Title: Population Ecology of Fendler Ceanothus: Responses to Herbivory and Forest Restoration Treatments
Author: * Huffman, D.W.
Subject: Vegetation studies, Ecological Restoration, Fendler ceanothus
Abstract: To understand responses of Fendler ceanothus to forest restoration treatments and large ungulate herbivory, I focused research on four areas: 1) effects of large ungulate herbivores on Fendler ceanothus stem size, morphology, and flower production, 2) production, fate, and germination of Fendler ceanothus seeds, 3) importance of overstory density, ungulate herbivory, prescribed fire, and drought for Fendler ceanothus growth and regeneration, and 4) simulation of population dynamics under various management scenarios. After two seasons (1999, 2000), plants protected from large ungulate herbivores were larger and produced greater biomass, leaf area, and flowering stems than plants that were not protected. These results showed that large herbivores such as mule deer (Odocoileus hemionus) and Rocky Mountain elk (Cervus elaphus) constrained growth and reproduction of Fendler ceanothus in thinned forest units. Fendler ceanothus stems that were not protected from large herbivores did not produce fruit over the four-year study (1999-2002). Seed production (2000-2001) was affected by stem size and probably drought. Predispersal seed parasites and postdispersal predators were important sources of ovule loss. Seed germination after iii exposure to 90C (10-minute duration) was greater than without heat treatment. These results increase our understanding of Fendler ceanothus seed production and losses. Stand density index (SDI) and browsing by ungulates were negatively related to Fendler ceanothus growth. Prediction of growth from SDI and browsing was poor in years of drought. Plant mortality was positively related to depth of forest floor consumed in experimental burning. Fendler ceanothus seedlings emerged on burned plots but not on unburned plots. These results indicate that overstory tree thinning and prescribed fire can increase growth and reproduction of Fendler ceanothus but responses are constrained by herbivory and drought. Simulation of Fendler ceanothus population dynamics suggested that restoration treatments and herbivory interact to affect long-term persistence and population structure. Populations that did not experience fire were generally dominated by dormant seeds whereas burned populations had relatively even life stage structures at the end of the 25- year simulation. Frequent fire (2-5 yr) stimulated growth of protected populations but negatively affected populations exposed to intense herbivory.
Publisher: Northern Arizona University