Danielle Watts

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Axiom Propeller tests in the Emerson Cavitation Tunnel

An ecological mechanism to create regular patterns of surface dissolution in a low-relief carbonate landscape

OOS 9-6: Variance as an indicator of biogeomorphic regime shifts in wetland ecosystems

The 94th ESA Annual Meeting, Aug 4, 2009

Biogeoscience opportunities to address agricultural supply chain risk: observations, methods, and applications

Connecting Landscape Processes and the Sedimentary Record II Posters

Ecosystem CO2 fluxes and landscape dynamics in response to hydrologic modification in the Everglades ridge-slough mosaic

The ridge-slough mosaic in the central Everglades, which comprised large areas of the pre-drainag... more The ridge-slough mosaic in the central Everglades, which comprised large areas of the pre-drainage landscape, is a patterned peatland with elongated ridge patches embedded in a matrix of hydraulically interconnected sloughs. Hydrologic modification over the last century has led to widespread loss of this historic patterning, as evinced by changes in both the corrugated topography of the peat surface as well as broad changes in vegetation type and prevalence. As a peat accreting wetland, carbon dynamics play a pivotal role in ...

Variance as an indicator of biogeomorphic regime shifts in wetland ecosystems

Background/Question/Methods Recent theoretical models and some empirical observations suggest tha... more Background/Question/Methods Recent theoretical models and some empirical observations suggest that rising variance may provide an early warning of incipient regime shifts, but studies to date overwhelmingly emphasize lentic ecosystems undergoing transitions between oligotrophic and eutrophic conditions. Here we evaluate the utility of variance as an indicator of impending regime shift in two distinct wetland ecosystems where state transitions are governed by biogeomorphic feedbacks. In aridland streams, channel stabilization by dense vegetation allows persistence of wetlands during massive flash floods. Data from a two year field study of these systems are re-analyzed to determine whether systems with greater spatial variance of vegetation biomass are more susceptible to catastrophic erosion. In the peatlands of the Florida Everglades, interactions among hydrologic regime, plant community structure, and carbon balance maintain distinct soil elevation modes with associated vegetation...

Ecohydrologic feedbacks and topographic pattern in Everglades peatlands: a model of the self-organizing canal hypothesis

Background/Question/Methods Regular, self-organized patterning has been observed in a wide range ... more Background/Question/Methods Regular, self-organized patterning has been observed in a wide range of ecosystems and is attributed to the interaction of positive local and negative distal feedbacks. One such system is the Florida Everglades, which were historically dominated by a mosaic of high elevation ridges supporting productive emergent communities and lower elevation sloughs inhabited by floating and submerged plants. Interactions among hydroperiod, plant community composition (and therefore productivity), and respiration have long been hypothesized to produce and maintain the local elevation differences via their effects on peat accreation; however, mechanisms capable of producing the elongated, flow-oriented patterning of the ridge-slough mosaic habitats are less clear. In this study we evaluate a simple model in which peat accretion is coupled to hydrologic conditions, and in which hydrologic conditions in one patch are coupled to adjacent patches via their reciprocal effects...

Watts et al. 2014

Hydrologic control on ecosystem metabolism: Local processes and landscape dynamics in the Everglades ridge-slough

Reciprocal Vegetation-Flow Feedbacks Driving Early-Stage Landscape Evolution in a Restored Wet Meadow

Landform elevation suggests ecohydrologic footprints in subsurface geomorphology

Hidden Flows: Advection Between Topographic Highs and Lows in a Patterned Wetland Driven By Instantaneous Water Level Equilibration

Evidence of biogeomorphic patterning in a low-relief karst landscape

Earth Surface Processes and Landforms, 2014

Patterned landscapes are often evidence of biotic control on geomorphic processes, emerging in re... more Patterned landscapes are often evidence of biotic control on geomorphic processes, emerging in response to coupled ecosystem processes acting at different spatial scales. Self-reinforcing processes at local scales expand patches, while self-inhibiting processes, operating at a distance, impose limits to expansion. In Big Cypress National Preserve (BICY) in southwest Florida, isolated forested wetland depressions (cypress domes) appear to be evenly distributed within a mosaic of short-hydroperiod marshes and pine uplands. To test the hypothesis that the apparent patterning is regular, we characterized frequency distributions and spatial patterns of vegetation communities, surface and bedrock elevation, and soil properties (thickness and phosphorus content). Nearest neighbor distances indicate strongly significant wetland spatial overdispersion, and bedrock elevations exhibited periodic spatial autocorrelation; both observations are consistent with regular patterning. Bedrock elevations and soil P were clearly bimodal, suggesting strong positive feedbacks on wetland patch development. Soil-surface elevations exhibited weaker bimodality, indicating smoothing of surface morphology by some combination of sediment transport, mineral reprecipitation, and organic matter production. Significant negative autocorrelation of bedrock elevations at scales similar to wetland spacing suggest the presence of distal negative feedbacks on patch expansion. These findings support the inference of regular patterning, and are consistent with the presence of local positive feedbacks among hydroperiod, vegetation productivity and bedrock dissolution. These processes are ultimately constrained by distal negative feedbacks, potentially induced by landscape scale limitations on the water volume required to enable this biogeomorphic mechanism.

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Discharge Competence and Pattern Formation in Peatlands: A Meta-Ecosystem Model of the Everglades Ridge-Slough Landscape

PLoS ONE, 2013

Regular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrop... more Regular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrophic loss in response to changing landscape drivers. The central Everglades (Florida, USA) historically exhibited regular, linear, flow-parallel orientation of high-elevation sawgrass ridges and low-elevation sloughs that has degraded due to hydrologic modification. In this study, we use a meta-ecosystem approach to model a mechanism for the establishment, persistence, and loss of this landscape. The discharge competence (or self-organizing canal) hypothesis assumes non-linear relationships between peat accretion and water depth, and describes flow-dependent feedbacks of microtopography on water depth. Closed-form model solutions demonstrate that 1) this mechanism can produce spontaneous divergence of local elevation; 2) divergent and homogenous states can exhibit global bi-stability; and 3) feedbacks that produce divergence act anisotropically. Thus, discharge competence and non-linear peat accretion dynamics may explain the establishment, persistence, and loss of landscape pattern, even in the absence of other spatial feedbacks. Our model provides specific, testable predictions that may allow discrimination between the self-organizing canal hypotheses and competing explanations. The potential for global bi-stability suggested by our model suggests that hydrologic restoration may not re-initiate spontaneous pattern establishment, particularly where distinct soil elevation modes have been lost. As a result, we recommend that management efforts should prioritize maintenance of historic hydroperiods in areas of conserved pattern over restoration of hydrologic regimes in degraded regions. This study illustrates the value of simple meta-ecosystem models for investigation of spatial processes.

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Hydrologic Modification and the Loss of Self-organized Patterning in the Ridge–Slough Mosaic of the Everglades

Ecosystems, 2010

The ridge-slough landscape of the Everglades (Florida, USA), is characterized by elevated ridges ... more The ridge-slough landscape of the Everglades (Florida, USA), is characterized by elevated ridges dominated by sawgrass (Cladium jamaicense) interspersed among deeper sloughs dominated by floating, submerged and emergent macrophytes and calcareous periphyton. Interactions among hydrologic conditions (water depth, hydroperiod), plant composition and production, and respiration are hypothesized to create alternative peat accretion equilibria at the point scale, while spatial interactions among patches create regular pattern at the landscape scale. Despite significant research on these interactions, few studies have examined the hypothesis that the ridge-slough landscape consists of spatially coupled alternative stable patch states, and none has used diagnostic indicators thereof to assess landscape resilience to hydrologic change. Dense random sampling of water depths (a proxy for soil elevation) along a gradient of hydrologic impairment of drained to relatively natural to impounded conditions was used to evaluate four predictions related to this hypothesis: (1) bimodal soil elevation distributions show strong fidelity to community type; (2) positive autocorrelation at short distances with negative values at longer distances; (3) strong anisotropy (diagnostic of flow orientation), and spatial structure (diagnostic of the strength of landscape self-organization); and (4) loss of these features with hydrologic modification. Our results support the hypothesis that soil elevations are strongly bimodal and anisotropic in areas with minimal hydrologic impact, and spatial autocorrelation patterns indicate the operation of scale-dependent feedbacks. These metrics change markedly with hydrologic modification, although with differences between drainage and impoundment. Moreover, changes in landform precede associated changes in vegetation, suggesting their utility as diagnostic indicators of landscape degradation and recovery.

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Reciprocal Biotic Control on Hydrology, Nutrient Gradients, and Landform in the Greater Everglades

Critical Reviews in Environmental Science and Technology, 2011

modification of local site conditions via mechanisms of peat accretion (including via effects of ... more modification of local site conditions via mechanisms of peat accretion (including via effects of landscape P redistribution on primary production) or limestone dissolution. Coupling these local positive feedbacks, which drive patch expansion, with inhibitory or negative feedbacks on site suitability at distance, which serve to constrain patch expansion, provide the mechanistic basis for landscape pattern formation. The spatial attributes (range and isotropy) of the distal negative feedback, in particular, control pattern geometry; elucidating the mechanisms and properties of these distal feedbacks is critical to restoration planning.

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Group-Advantaged Training of Research (GATOR): A Metamorphosis of Mentorship

BioScience, 2011

We describe Group-Advantaged Training of Research (GATOR), a yearlong structured program at the U... more We describe Group-Advantaged Training of Research (GATOR), a yearlong structured program at the University of Florida that guided graduate student mentors and their undergraduate mentees through the mentored research process. Using the national Survey of Undergraduate Research Experiences for an academic year we found that outcomes for our mentees were similar to those for other programs. We also used an internal survey, combined with qualitative observations, to develop a road map of the mentoring process, which we call the "Metamorphosis of Mentorship." This model provides tangible steps on the road to becoming a scientist, incorporates reasons mentees stall in research, and suggests ways to overcome mentoring challenges and prevent attrition. The structure and outcomes of this program will be useful to researchers and administrators working to engage undergraduates in scientific research, particularly at large universities where undergraduates are often mentored by graduate students.

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Ecosystem CO 2 fluxes and landscape dynamics in response to hydrologic modification in the Everglades ridge-slough mosaic

Alternative stable states and self-organized patterning: Everglades Ridge and Slough Mosaic

Alternative stable states have been described for numerous ecosystems in the recent literature (S... more Alternative stable states have been described for numerous ecosystems in the recent literature (Scheffer and Carpenter, 2003; Suding et al., 2004; Schrøder et al., 2005). These ecosystems exhibit resistance to changes over some range of an ecosystem driver via homeostatic feedbacks; however, thresholds at the edge of that range lead to catastrophic regime shifts to some new self-reinforcing ecosystem state (Scheffer et al., 2001). A key component of these shifts is hysteresis (path dependency) wherein the threshold at which ...

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