Masters Theses

Amy E. Arnold

Date of Award

12-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Ecology and Evolutionary Biology

Major Professor

J. Frank McCormick

Committee Members

Carol Harden, Frank Harris, Stephen Nodvin

Abstract

Three tropical herbaceous species, Dieffenbachia seguine, Ichnanthus pallens, and Pilea inaequalis, were investigated in the Bisley Experimental Watersheds of Luquillo Experimental Forest, Puerto Rico. Objectives were:

  1. To characterize microenvironments of the three species in terms of light and soil physical and chemical properties.
  2. To examine relationships between microenvironment and plant growth and other estimators of plant performance.
  3. To describe the ecological life cycles of the three species in terms of recruitment, mortality, growth, and clonal behavior and their role in forest recovery following canopy disturbance.
  4. To determine nutrient contents and rates of decomposition of the three species in order to understand their role in nutrient dynamics.
Results supported the following conclusions:
  1. Study species habitats were related to microenvironmental differences in soil moisture and nutrients. Soil moisture varied significantly with topographic position, and soil moisture was subsequently correlated with number of soil chemical properties. Light environments were highly variable.
  2. Growth of all three species was related to soil properties and/or light differences.
  3. Biomass and several measures of plant size were significantly related to soil properties and/or light.
  4. Biomass of these herbs was accurately estimated using nondestructive measurements of plant size.
  5. All three study species were determined to be r-strategists; however, Dieffenbachia exhibited a more conservative life history strategy. Clonal reproduction by means of rhizome fragmentation (Dieffenbachia) or rooting at nodes with subsequent fragmentation (Ichnanthus, Pilea) appeared to be extensively used by study species.
  6. Dieffenbachia, Ichnanthus, and Pilea were well-adapted to canopy disturbance, specifically to hurricane disturbance.
  7. Dieffenbachia, Ichnanthus, and Pilea concentrated nutrients above substrate levels, and all three species exhibited rapid decomposition rates.

Based on several lines of evidence, Dieffenbachia, Ichnanthus, and especially Pilea populations were found to play an important role in nutrient dynamics, and thereby ecosystem resiliency, following canopy disturbance in the Bisley Experimental Watersheds.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS