Long-term Research on Productivity and Biodiversity

Research Team: Dr. Robert J. Mitchell (Scientist), Dr. L. Katherine Kirkman ( Associate Scientist), Dr. Lindsay R. Boring (Director), Dr. L. Michael Conner (Associate Scientist), Stephen D. Pecot (Research Technician IV), Kimberly L. Coffey (Research Technician IV), R. Scott Taylor (Research Technician III), and Jim Bradley (Field Instrumentation Technician)

Some of the first research projects investigating the longleaf pine ecosystem at Ichauway focused on how patterns of vegetation and productivity were influenced by water and nutrient availability. An ecological site classification of Ichauway that classified ecosystems based upon their landform, soils, and vegetation was first developed. Using this landscape classification scheme, an interdisciplinary project was conducted at the Jones Center to examine ecological processes of the longleaf pine ecosystem across the entire environmental gradient found at Ichauway. The study areas ranged from very dry sandhill sites where forty percent of the productivity was oak, to the edges of depressional wetlands where there were almost no oaks and productivity was ninety percent greater than the dry sites. We assessed resource availability, i.e. water and nutrients, and examined how this impacted above and belowground productivity and biodiversity of species. We found that soil water availability was a large driver of productivity and species richness across the sites in this ecosystem, even though these forests are among the lowest in nitrogen fertility reported in the scientific literature.

A more thorough understanding of how soil water and nutrient resources are interrelated in their influence on vegetation composition and long-term productivity of these woodlands requires experimental manipulation. Our next phase of new research includes three major experiments:

controlled water and nutrient applications in the forest over a period of several years to span exceptionally dry and wet periods;
fire exclusion across the natural gradient from dry to wet; and
a small scale plot study of soil nitrogen using legume plantings and prescribed fire.

In the first study, we are increasing the amount of water and nitrogen that limit productivity in dry years on plots located across the range of soil types at Ichauway for at least ten years. This is a large scale undertaking that has required implementation of irrigation wells, pipeline construction, treatment of water, and a lot of teamwork. For the second part, we are comparing biological diversity of species, productivity, and nutrient cycling processes in plots with, and without, fire over the same time period. Finally, with the last experiment we are planting a group of legume species to determine their interaction with fire in maintaining nutrients and productivity in the ecosystem. These experimental studies will provide further information as to how longleaf pine ecosystems function through time across periods of varied percipitation, and provide insights for their management and conservation. The research will influence emerging policy issues such as the use of prescribed fire in the southeastern USA, comparative water use of longleaf pine forests versus other more water intensive regional land uses, the response of regional forests to potential climate changes, and baseline carbon storage. The information from this long-term work will also provide guidance for restoration efforts of these biologically diverse ecosystems throughout the southeast coastal plain where ninety-five percent of their acreage has been lost.

Research in progress, publications forthcoming.

Funded by: The Joseph W. Jones Ecological Research Center