Kari Foster

 

Kari is a senior biology major from .

The purpose of this study is to compare life history patterns of plant species growing along an elevational gradient on Kentucky Lake that includes several distinct environments.  The littoral zone at the lower end of the gradient is disturbed annually by flooding. Stressful anaerobic soils occur at the upper end of the littoral zone where flooding does not occur, but the soils are permanently water-saturated.  Finally, locations at the upper end of the gradient (floodplain), where neither disturbance nor water-saturated soils are present, vigorous competition occurs.  These environment types are similar to those described by Grime (1977) in his mechanism of plant life history evolution.  He explains that plants growing in these environments (disturbed, stressful and competitive) have evolved distinct resource allocation patterns as a result of the environment.  For example, species adapted to a disturbed environment are usually annuals that allocate most of the available resources to early reproduction and are known as ruderal species (Grime 1977).  Stress-tolerant species (a second life history) allocate a large portion of their resources to maintenance or survival of unfavorable environmental conditions.  Finally, species that have evolved competitive life histories occur in more fertile environments where disturbance and stress levels are minimal and allocate biomass to resource acquiring organs.

        

Since individuals of several species are distributed across the elevational gradient, variation in life history patterns within a single species can be studied.  Both, greenhouse and in the field studies will be used to determine the effect that annual flooding (disturbance),

anaerobic soils (stress), and competition has on the distribution of species across the gradient.  In addition, Grime's (1977) theory of plant life history evolution will be compared to Tilman's (1988) thesis that competition occurs in all habitats.  Soil samples from across the gradient will be collected and be subjected to two different water treatments, representing the moisture gradient along the embayment.  In the greenhouse, soil from half of the samples will be kept moist, while the soil from the other half of the samples will be flooded.

Chlorophyll fluorescence will be used to determine the effects of stress caused by the water-saturated soils in the upper end of the littoral zone.  Finally, various competition experiments will be performed across the gradient in order to determine if individuals growing in the

floodplain have developed a pattern that allows them to capture resources faster than individuals growing elsewhere along the gradient.