Effects of Natural Disturbances and Salvage Logging on Plant Communities: Implications for Ecological Restoration - I am currently funded through a joint venture agreement with the USDA National Forest Service ($223,535) to initiate a long-term experiment examining the effects of tornado damage and salvage logging on plant communities in mature oak-shortleaf forests in north Mississippi (specifically, the Tallahatchie Experimental Forest). This past winter (February 2008), a tornado struck and damaged about half of the long-term vegetation plots I had previously established in the early 2000s. This natural disturbance provides a rare and unique opportunity to examine both the impact of a natural disturbance on plant communities and the impact of post-storm salvage-logging operations. My previous research in the Tallahatchie Experimental Forest has shown that current composition and stand structure is an artifact of prolonged fire suppression in the past (Surrette, Aquilani, and Brewer 2008). I have recommended that the Forest Service take seriously implementing restoration treatments, which would include selective thinning (to open the canopy) combined with prescribed burning. The FS has resisted doing this, perhaps because of the regulatory constraints on logging. The tornado, however, has created conditions comparable to the proposed thinning treatments. Hence, this research will determine whether natural disturbances provide an opportunity to move forward with true restoration. This research will also examine the degree to which such restoration is compromised or negated altogether by salvage logging, with the concern being that the expected positive response of groundcover vegetation and oak regeneration to canopy openings will be eliminated by intense disturbance of the groundcover associated with salvage logging operations.
Effects of Invasive Plants - I am currently funded through a cooperative agreement with the USDA National Forest Service ($60,000) to examine the impact of the non-native grass, Microstegium vimineum, on native plant diversity in floodplain and terrace forests in northern Mississippi. I am currently seeking to expand this research by collaborating with a microbial ecologist, Colin Jackson. Together we have a pending NSF grant proposal in review to examine the impact of Microstegium on native species of concern as well as ecosystem processes such as carbon decomposition and nitrogen and phosphorus mineralization. We are using a combination of structural equation modeling and targeted manipulative field experiments to address these questions. The structural equation modeling component of the research will enable us to tease apart the various confounding variables that could influence native species composition and decomposition. In addition, SEM will enable us to examine indirect effects of Microstegium on decomposition mediated through plant species losses. In this way, our approach provides a more realistic assessment of how plant species losses affect ecosystem processes than random-selection biodiversity experiments.
Ecological Restoration of Open Oak Woodlands in the Loess Plains of North Central Mississippi - I am continuing a long-term experiment I designed at the Strawberry Plains Audubon Center, which was begun in 2003. I am examining how plant communities respond to the combination of selective thinning of off-site trees (i.e., those that invaded during fire suppression) and biennial prescribed burning during the lightning season. This experiment is the focal restoration project associated with the USDA National Needs Fellowship Grant for which I am a Co-PI. Three of the four M.S. fellowships have been awarded. The recipients are Erynn Maynard (my student), Anjel Craig (Dr. Jason Hoeksema’s student), and Jason Ryndock (Dr. Holland’s student). The ultimate goal of the restoration experiment (which includes replicated sites and controls) is determine the impact of the restoration treatments on biodiversity (plants, fungi, arthropods) and ecosystem processes. Preliminary results reveal positive results in terms of increased plant species richness, increased abundance of open woodland indicators, and no increase in weedy disturbance indicators as a group.
Using Competition between Carnivorous Plants and Non-Carnivorous Plants to Test the Relative Importance of Niches and Neutrality in Species Coexistence - I am interested in using competition between pitcher plants and non-carnivorous plants as a model for testing niche theory. Specifically, I am interested in following up on the results of my 2003 paper in Ecology, “Why don’t carnivorous pitcher plants compete with non-carnivorous plants for nutrients?” and testing the hypothesis I proposed in my 2006 paper in Applied Vegetation Science. This hypothesis states that nutrient niche differences between carnivorous plants and non-carnivorous plants are only important for species coexistence during years in which light is not limiting to growth (e.g., immediately after a fire). During years without fire, growth of both pitcher plants and their non-carnivorous neighbors is primarily limited by single resource, light. Shade during this time reduces demand for nutrients (be they from prey or the soil), which in turn results in reduced growth rates and thus reduced rates of competitive displacement. Hence, the hypothesis in effect states that nutrient niche differences are important for species coexistence in years with fire, whereas neutrality and low rates of displacement are important for coexistence during years without fire. I proposed to test this hypothesis using manipulative field experiments.
Assessing long-term changes in freshwater environmental conditions using mussel shell growth records – Dr. Wendell Haag is the lead investigator on this Joint Venture with the Southern Research Station. Dr. Andrew Rypel is beginning a planned 3-year post-doctoral appointment in my lab (August 2008). Dr. Rypel will be reconstructing climate records (water levels) from measuring growth rings in freshwater mussels (from the wild and from museum collections) and bald cypress in the Pascagoula River watershed in southern Mississippi. My contribution will primarily focus on finding old second-growth populations of longleaf pine trees that were used in turpentine production and thus are ideal for documenting fire scars and thus fire frequency. The primary goals of this research are 1) to use growth patterns of mussels to investigate freshwater environmental conditions, and 2) to use growth patterns of mussels, bald cypress, and longleaf pine to examine climatically-driven linkages in environmental conditions between freshwater, wetland, and upland ecosystems in southern Mississippi.
Other Ongoing Research Projects
Long-term effects of repeated clipping and nutrient addition on climax perennial grasses in a wet longleaf pine savanna and associated effects on subordinate plant species.
Post-Katrina recovery of interior dune communities on Mississippi barrier islands
Evolution of fire-stimulated flowering in Pityopsis (independent research as well as the masters project of View-Hune Teoh)
Population viability of an endangered pitcher plant (Jason Chesser’s Ph.D. project)
Allelopathic interactions between Ceratiola ericoides and an invasive grass, Panicum repens, within interior dune communities following Hurricane Katrina (Christine Bertz Ph.D. project).