Monitoring tree secies diversity over large spatial and temporal scalesThis article is part of a larger document. View the larger document here.
The prospect of decline in biological diversity has become a central concern in the life sciences, both around the world and across the United States. Anthropogenic disturbance has been identified as a major factor affecting species diversity trends. An increase in the harvesting of naturally diverse timber stands in the South has become an important issue. The ultimate impact of this high, and increasing, level of disturbance on tree species diversity in forests of the Southern United States is uncertain. We offer a brief review of literature related to major points in the development of species diversity concepts over the last 100 years. This is followed by a case study that makes use of periodic U.S. Department of Agriculture Forest Service, Forest Inventory and Analysis (FIA) data from Mississippi. Our interest, for southern forests, is whether tree species richness has declined, increased, or remained essentially stable over the last 35 years. We find that tree species richness has declined by 11 percent across Mississippi since 1977. However, in FIA plots that had no evidence of harvesting, tree species richness increased by 44 percent since 1967. It is difficult to determine what constitutes a healthy level of tree species richness for particular sample designs and large-scale State surveys. Additional analytical complexity comes from the lack of documentation and knowledge concerning various levels of richness dynamics for large spatial and temporal scale studies.