Influence of microenvironment on growth and nutrient dynamics of three herbaceous species in the Bisley Experimental Watersheds of Luquillo Experimental Forest, Puerto Rico

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.

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.