Wednesday, August 9, 2017: 8:00 AM-11:30 AM
Portland Blrm 257, Oregon Convention Center
E. Louise Loudermilk, USDA Forest Service
Joseph J. O'Brien, USDA Forest Service
Brooke A. Cassell, Portland State University
This session disseminates findings from a multidisciplinary five year project, the main goal of which was to identify ecological mechanisms that drive extraordinarily high levels of plant and insect diversity in longleaf pine (Pinus palustris
Mill.) ecosystems. Further, we aimed to link these mechanisms to forest structure in order to evaluate ecological theory, and derive a modeling framework for testing the outcomes of various management actions on biological diversity. We tested ecological theory by examining the gradient between species competition and pure stochasticity as driven by varying fire frequency and fire intensity driven by tree canopy density. Our study areas were located in the longleaf pine sandhills and flatwoods of Eglin Air Force Base, NW FL, USA, where one of the few remaining substantial tracts of old-growth longleaf pine remain intact. We present findings on methods for capturing multiple aspects of biodiversity, such as interaction diversity and examine mechanisms driving changes of diversity in time and space. We examined how plant and arthropod communities colonized and assembled post-fire. Analyses presented include structural equation modeling, ordination, spatially explicit modeling, and other non-linear statistical techniques. We discuss how fire is measured spatially using thermal imagery, and why this is important for understanding individual and community level plant mortality and recruitment patterns. We present how these fire effects are explained by the arrangement of fuels which are in turn linked to both tree canopy structure and fire frequency. Tree canopy height models, developed from Light Detection and Ranging, coupled with plot level fuel measurements and models of episodic cone production were used to determine landscape level fuels over space and time. We also present on a novel 3D graphic design technique for simulating three-dimensional models of fuelbeds and relationships with fuel attributes, such as volume, surface area and biomass. This cross scale analysis is key to understanding the mechanisms that drive high plant diversity and patterns of interaction diversity at multiple trophic levels. Although this session focuses on longleaf pine forests of the southeastern U.S., the theme is relevant to many other frequently burned conifer or pine dominated ecosystems. These communities are often similar in structure and function, where fuels and fire frequency determine fire effects, in particular fire effects on patterns and processes of biological diversity.