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Ecosystems Restoration and Sustainability: Ecosystem Modeling

Researchers require an understanding of how specific ecological mechanisms regulate their structure and function in order to develop ecosystem management plans for restoring and protecting natural resources. Resource managers need decision-support tools that model community dynamics and responses to both natural processes and anthropogenic practices.

USGS scientists develop conceptual ecological models to help understand the natural environment and how human activities and natural events threaten these environments. Models use predictive relationships to estimate broad ecosystem responses to events. The models enable more informed management decisions and are used to increase the efficacy of results.

Research

 

Couvillion, B.R., Steyer, G.D., Wang, H., Beck, H.J., and Rybczyk, J.M., 2013, Forecasting the effects of coastal protection and restoration projects on wetland morphology in coastal Louisiana under multiple environmental uncertainty scenarios: Journal of Coastal Research, Special Issue 67 - Louisiana′s 2012 Coastal Master Plan Technical Analysis, p. 29-50, http://dx.doi.org/10.2112/SI_67_3

Few landscape scale models have assessed the effects of coastal protection and restoration projects on wetland morphology while taking into account important uncertainties in environmental factors such as sea-level rise (SLR) and subsidence. In support of Louisiana's 2012 Coastal Master Plan, we developed a spatially explicit wetland morphology model and coupled it with other predictive models. The model is capable of predicting effects of protection and restoration projects on wetland area, landscape configuration, surface elevation, and soil organic carbon (SOC) storage under multiple environmental uncertainty scenarios.

 

Glick, P., Clough, J., Polaczyk, A., Couvillion, B., and Nunley, B., 2013, Potential effects of sea-level rise on coastal wetlands in southeastern Louisiana: Journal of Coastal Research, Special Issue No. 63 - Understanding and Predicting Change in the Coastal Ecosystems of the Northern Gulf of Mexico, p. 211-233, http://dx.doi.org/10.2112/SI63-017.1

Coastal Louisiana wetlands contain about 37% of the estuarine herbaceous marshes in the conterminous United States. The long-term stability of coastal wetlands is often a function of a wetland's ability to maintain elevation equilibrium with mean sea level through processes such as primary production and sediment accretion. This study investigates the potential impact of current and accelerating sea-level rise rates on key coastal wetland habitats in southeastern Louisiana using the Sea Level Affecting Marshes Model (SLAMM).

 

Rivera-Monroy, V.H., Branoff, B., Meselhe, E., McCorquodale, A., Dortch, M., Steyer, G.D., Visser, J., and Wang, H., 2013, Landscape-level estimation of nitrogen removal in coastal Louisiana wetlands: potential sinks under different restoration scenarios: Journal of Coastal Research, Special Issue 67 - Louisiana′s 2012 Coastal Master Plan Technical Analysis, p. 75-87, http://dx.doi.org/10.2112/SI_67_6

Coastal eutrophication in the northern Gulf of Mexico is the primary anthropogenic contributor to the largest zone of hypoxic bottom waters in North America. Although biologically mediated processes such as denitrification are known to act as sinks for inorganic nitrogen, it is unknown what contribution denitrification makes to landscape-scale nitrogen budgets along the coast. As the State of Louisiana plans the implementation of a 2012 Coastal Master Plan to help restore its wetlands and protect its coast, it is critical to understand what effect potential restoration projects may have in altering nutrient budgets.

 

Visser, J.M., Duke-Sylvester, S.M., Carter, J., and Broussard, W.P., III, 2013, A computer model to forecast wetland vegetation changes resulting from restoration and protection in coastal Louisiana: Journal of Coastal Research, Special Issue 67 - Louisiana′s 2012 Coastal Master Plan Technical Analysis, p. 51-59, http://dx.doi.org/10.2112/SI_67_4

The coastal wetlands of Louisiana are a unique ecosystem that supports a diversity of wildlife as well as a diverse community of commercial interests of both local and national importance. The state of Louisiana has established a 5-year cycle of scientific investigation to provide up-to-date information to guide future legislation and regulation aimed at preserving this critical ecosystem. Here we report on a model that projects changes in plant community distribution and composition in response to environmental conditions.

 

Palta, M.M., Doyle, T.W., Jackson, C.R., Meyer, J.L., and Sharitz, R.R., 2012, Changes in diameter growth of Taxodium distichum in response to flow alterations in the Savannah River: Wetlands, v. 32, n. 1, p. 59-71, http://dx.doi.org/10.1007/s13157-011-0245-9

Efforts to maximize or restore ecological function on floodplains impacted by dam construction have increasingly focused on river flow management. Few studies, however, consider floodplain hydrogeomorphic position and annual climatic variation in dam impact assessment. The Savannah River, a large river ecosystem in the Southeastern United States, was impounded in the 1950’s. Our study objectives were: (1) Characterize hydrology in floodplain areas containing Taxodium distichum, and determine how it has been affected by dam operations; (2) Identify basal area increment (BAI) response of Taxodium to annual flooding and climate (dry, average, wet) conditions; (3) Assess BAI response to dam-induced hydrologic changes.

 

Steyer, G.D., Couvillion, B., Wang, H., Sleavin, B., Rybczyk, J., Trahan, N., Beck, H., Fischenich, C., Boustany, R., and Allen, Y., 2012, Appendix D2 – Wetland morphology model technical report, IN, Louisiana’s Comprehensive Master Plan for a Sustainable Coast: Coastal Protection and Restoration Authority, Baton Rouge, Louisiana.

This report describes the Wetland Morphology model which is comprised of landscape change and relative elevation sub‐models. The sub‐models described herein are built upon landscape change desktop models that were used to predict the effects of restoration alternatives for the Louisiana Coastal Area and Coastal Protection and Restoration Authority master plan efforts.

 

Ackleh, A.S., Carter, J., Cole, L., Nguyen, T., Monte, J., and Pettit, C., 2010, Measuring and modeling the seasonal changes of an urban Green Treefrog (Hyla cinerea) population: Ecological Modelling, v. 221, n. 2, p. 281-289, http://dx.doi.org/10.1016/j.ecolmodel.2009.10.012

Green Treefrogs (Hyla cinerea) were captured, marked, measured and released at an urban study site in Lafayette, Louisiana, during the 2004 and 2005 breeding seasons. A statistical method based on a generalization of the hypergeometric distribution was used to derive weekly time-series estimates of the population sizes. To describe the population dynamics, a stage structured mathematical model was developed and compared to time-series obtained from the weekly population estimates study using a least-squares approach.

 

Waddle, J.H., Dorazio, R.M., Walls, S.C., Rice, K.G., Beauchamp, J., Schuman, M.J., and Mazzotti, F.J., 2010, A new parameterization for estimating co-occurrence of interacting species: Ecological Applications, v. 20, no. 5, p. 1467-1475, http://dx.doi.org/10.1890/09-0850.1

Models currently used to estimate patterns of species co-occurrence while accounting for errors in detection of species can be difficult to fit when the effects of covariates on species occurrence probabilities are included. The source of the estimation problems is the particular parameterization used to specify species co-occurrence probability. We develop a new parameterization for estimating patterns of co-occurrence of interacting species that allows the effects of covariates to be specified quite naturally without estimation problems.

 

Ackleh, A.S., Allen, L.J.S., and Carter, J., 2007, Establishing a beachhead: A stochastic population model with an Allee effect applied to species invasion: Theoretical Population Biology, v. 71, n. 3, p. 290-300, http://dx.doi.org/10.1016/j.tpb.2006.12.006

We formulated a spatially explicit stochastic population model with an Allee effect in order to explore how invasive species may become established. In our model, we varied the degree of migration between local populations and used an Allee effect with variable birth and death rates. Because of the stochastic component, population sizes below the Allee effect threshold may still have a positive probability for successful invasion.

 

Gutzwiller, K.J., and Barrow, W.C. Jr., 2001, Bird–landscape relations in the Chihuahuan Desert: Coping with uncertainties about predictive models: Ecological Applications, v. 11, n. 5, p. 1517-1532, http://dx.doi.org/10.1890/1051-0761(2001)011[1517:BLRITC]2.0.CO;2

During the springs of 1995 and 1997, we studied birds and landscapes in the Chihuahuan Desert along part of the Texas-Mexico border. Our objectives were to assess bird-landscape relations and their interannual consistency and to identify ways to cope with associated uncertainties that undermine confidence in using such relations in conservation decision processes. Bird distributions were often significantly associated with landscape features, and many bird-landscape models were valid and useful for predictive purposes.

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