Current Research Projects
Mechanisms of Ridge and Slough Patterned Landscape Maintenance and Degradation (US Army Corps of Engineers): This 5 year project (started August 2010) focuses on the mechanisms of pattern formation in the ridge slough landscape. Flow-oriented ridges and sloughs create a complex microtopographic mosaic that is integral to landscape and hydraulic conenctivity and habitat heterogeneity. The pattern is apparently autogenic since the underlying bedrock is not corrugated in the same way as the peat surface; vertical corrugation is on the order of ca. 30 cm and creates a strongly bi-modal distribution of soil elevations under the best conserved hydrologic conditions. Our conceptual model is that there are, at the core, two ecological configurations that achieve the same net carbon balance over time. The first, ridges, are high production and therefore have greater peat accretion potential, but they occur at higher elevation (ca. 30 cm or more) and are thus exposed more frequently and for a longer duration which leads to greater respiration. The other ecosystem "state" are sloughs that are far less productive, but also almost never dry out at least under pre-development hydrologic conditions. As such, they achieve the same long term average net carbon accretion. This hypothesis is widely asserted, but has surprisingly little empirical support. In addition to testing the mechanisms for patch stability, we are also examining the manner in which that peat accretion equilibrium changes with hydrologic modification.
While this peat accretion process can help explain the bi-modality of land surface and the long term persistence of a patch type at a particular location, the spatial pattern of patches (roughly equally prevalent, elongated markedly in the direction of historical flow) is not as clear. The prevailing hypothesis is that sediment redistribution from the sloughs onto the ridge edges creates the characteristic pattern, but several observations run counter to that mechanism, or at leat suggest that other mechanisms may also be operating. In this work, we are using a variety of simulation methods to explore orientation effects on hydraulics. The "self-organizing canal hypothesis", outlined in one of our recent papers, posits that patch connectivity and elongation may occur in response to the hydraulic effects of patch geometry alone.
Finally, we are investigating in this work a variety of mechanisms that might explain marked enrichment of P on ridge centers vis-a-vis sloughs, a process that may confer an additional feedback on the carbon balance.
Landscape Pattern Degradation in the Central Everglades (US Army Corps of Engineers): This 4 year project (started August 2008) focuses on the same suite of questions as the project above, but takes a more observational approach. In particular, we are analyzing soil elevation and plant composition data from intensive synoptic surveys across 80 2 x 4 km blocks distributed throughout the Everglades. Florida International University is the lead institution on this project (PIs: Dr. Jim Heffernan and Dr. Mike Ross). Among other things, we are exploring in detail how hydrologic modification induces pattern loss by evaluating the statistical and geostatistical properties of soil elevation. Among the predictions that we're testing is that patterned and unpatterned states are alternative stable landscape configurations. In addition, the integration of tree island surveys and detailed spatial mapping of vegetation makes it possible for us to investigate how changes in the properties of microtopography change, and how other metrics of landscape change (e.g., in the vegetation, the prevalence of different patches, the spectral properties of the vegetation) covary; the intent is to identify early warning indicators of incipient state changes. This provides important information for Everglades restoration, and also extends the theory of incipient regime shifts in ecosystems to a more spatially explicit setting.
Shovel Logging Best Management Practices for Bottomland Logging (US EPA): This 3 year project (started January 2008) focuses on comparing the consequences of different logging techniques on cypress and other wetland tree taxa regeneration. The Florida Division of Forestry publishes best management practices, and a recent addition to the BMP manual pertains to a new technique for extracting logs from wetland sites with poorly consolidated soils. The practice, which involves constructing a skid trail from felled logs that are subsequently removed when logging is complete, is thought to minimize site damage, and therefore accelerate site regeneration vis-a-vis the conventional techniques that use double-tired skidders. Our work tests the efficacy of this BMP.
Pending Research Projects
Fine-scale water partitioning between canopy, soil and runoff; feedbacks between fire and water quantity/quality; BMPs for forest fertilization; wetland harvesting effects on hydrology, soil quality and ecosystem recovery.
Completed Research Projects
Environmental accounting of ecosystem services from forests and watersheds; public perception of and willingness to pay for water quality; decision support for water supply planning; hydrologic implications of large scale biofuel initiatives
