Roelof Boumans

Modular Ecosystem Modeling

The Library of Hydro-Ecological Modules (LHEM, http://giee.uvm.edu/LHEM) was designed to create flexible landscape model structures that can be easily modified and extended to suit the requirements of a variety of goals and case studies. The LHEM includes modules that simulate hydrologic processes, nutrient cycling, vegetation growth, decomposition, and other processes, both locally and spatially. Where possible the modules are formulated as STELLA models, which adds to transparency and helps reuse. Spatial transport processes are presented as C++ code. The modular approach takes advantage of the spatial modeling environment (http://giee.uvm.edu/SME3) that allows integration of various STELLA models and C++ user code, and embeds local simulation models into a spatial context. Using the LHEM/SME the Patuxent landscape model (PLM) was built to simulate fundamental ecological processes in the watershed scale driven by temporal (nutrient loadings, climatic conditions) and spatial (land use patterns) forcings. Local ecosystem dynamics were replicated across a grid of cells that compose the rasterized landscape. Different habitats and land use types translate into different modules and parameter sets. Spatial hydrologic modules link the cells together. These are also part of the LHEM and define horizontal fluxes of material and information. This approach provides additional flexibility in scaling up and down over a range of spatial resolutions. Model results show good agreement with data for several components of the model at several scales. Other applications include several subwatersheds of the Patuxent, the Gwynns Falls watershed in Baltimore, and others.  2003 Elsevier Ltd. All rights reserved.

Changes in saltmarsh surface elevation due to variability in evapotranspiration and tidal flooding

We examine the potential for diurnal variation in elevation of saltmarsh surfaces as a source of error in long-term experiments; errors particularly critical in high precision studies that employ the surface elevation table (SET) as a means to monitor elevations. The field study was carried out along the New Brunswick coast of the Bay of Fundy in high and low zones at three marshes with different tidal ranges. We used a total of 16 benchmark pipes and controlled for daily variability in evapotranspiration (ET), as well as timing of tidal flooding, two factors that affect soil water storage, and consequently soil volumes. In six of nine trials we detected significant elevation change over periods as short as 5 d. Marsh-wide averages ranged from 1.2 to 3.0 mm, greater than the yearly increase in relative sea level in many regions. Wood Point marsh had the highest tidal range, but lowest soil organic matter content, giving its soils the lowest compressibility and little sensitivity to ET during two of three trials; the average change in elevation in Wood Point high marsh stations was 4.0 mm during the last trial. Greater differences later in the growing season (while temperature changes were minor) at Wood Point and another site suggest that plant transpiration drove changes in water storage at those sites. Significantly greater differences in elevation with lower plant cover in the third marsh suggests that evaporation drove changes in water storage there. Surface elevation change due to ET should be of greatest concern to SET users in temperate regions where there are large changes in plant biomass and variable temperatures. Variation due to plant transpiration could be reduced if yearly monitoring is scheduled before the start of the growing season.

Non - spatial calibrations of a general unit model for ecosystem simulations

General Unit Models simulate system interactions aggregated within one spatial unit of resolution. For unit models to be applicable to spatial computer simulations, they must be formulated generally enough to simulate all habitat elements within the landscape. We present the development and testing of a unit model for the Patuxent River landscape in the state of Maryland, USA. The Patuxent Landscape Model (PLM) is designed to simulate the interactions among physical and biological dynamics in the context of regional socioeconomic behavior. The PLM is a tool for evaluating landscape change within the Patuxent watershed through simulation of ecological systems. A companion economic model estimates land development patterns and effects on human decisions from site characteristics, ecosystem properties, and regulatory paradigms. Landscape elements that are linked within the PLM are forest, agriculture and open water systems, and three levels of urban development. Urban developments are low and medium density residential areas (14.07% of the total watershed), and commercial, industrial and institutional area (5.7%). Forests are mixed populations of deciduous and evergreen species (45.11%). Agricultural areas (28.02%) are simulated through rotating crops of corn, winter wheat and soybeans within a cycle of two years. Open water (6.84%) represents the ecosystems within the rivers and streams where phytoplankton are the primary producers. In this paper we illustrate, how we gathered and formalized working models used within the Patuxent watershed for forests, agriculture urban settings and wetlands. Further, we show how we tested and merged the variety of models employed by scientific disciplines and created a general unit model to be used in the Patuxent Landscape Model (Pat – GEM). The Patuxent Landscape Model is built under the Spatial Modeling Environment.

Applying the Patuxent Landscape Unit Model to human dominated ecosystems: the case of agriculture

Non-spatial dynamics are core to landscape simulations. Unit models simulate system interactions aggregated within one space unit of resolution used within a spatial model. For unit models to be applicable to spatial simulations they have to be formulated in a general enough way to simulate all habitat elements within the landscape. Within the Patuxent River watershed, human dominated land uses, such as agriculture and urban land, are already 50% of the current land use, while urban land is replacing forests, agriculture and wetlands at a rapid rate. The Patuxent Landscape Model (PLM) with the Patuxent General Unit Model as core (Pat-GEM) was developed as a predictive policy tool to estimate environmental impacts of such land use changes. The Pat-GEM is based on the General Ecosystem Model (GEM) developed by [Ecol. Modelling 88 1996 263]. Previous calibrations of the Pat-GEM for anthropogenic land uses have not been satisfactory due to the scarcity of appropriate data. This paper shows Pat-GEM simulations of biomass growth and nutrient uptake for crops typical within the Patuxent watershed. The Pat-GEM was expanded to include processes and fluxes that characterize agricultural land use. The most important extension was to include crop rotation into the model. Additionally, we refined the processes for planting, harvesting and fertilization by introducing specific growth parameters. Our revised Pat-GEM was calibrated against the results from Erosion Productivity Impact Calculator (EPIC) a widely used and calibrated agricultural model. We achieved high correlation between results generated with Pat-GEM and EPIC. The correlation coefficients (r 2 ) varied between 0.87 and 0.98, with the simulation results for winter wheat showing the lowest correlation coefficients. Intercalibration using EPIC is a powerful method for calibrating the Pat-GEM model for agricultural land use. EPIC was able (a) to provide about 30% of the input data required for running the Pat-GEM model; and (b) to provide time series output data (with a daily time step) to calibrate the output variables biomass production and nutrient uptake. # 2002 Elsevier Science B.V. All rights reserved.

Participatory Modeling as a Tool for Community Development Planning: Tourism in the Northern Forest

Tourism development planning is challenging for rural communities transitioning from dependence on resource extraction to a diversified economy including tourism. This research examines how participatory modeling can help communities improve their understanding of diverse perspectives and identify intrinsically linked components of tourism. Using a participatory process in six communities in the Northern Forest region of the northeastern United States, a dynamic computer model was developed illustrating complex relationships associated with recreation and tourism development. A user-friendly interface and step-by-step manual were distributed to facilitate application of the model by community planners. Evaluation of the model indicated that barriers limited widespread adoption of the model as a decision-making aid for planners. However, evaluation of the modeling process revealed positive impacts on community capacity including fostering dialogue, increasing understanding of different perspectives, and helping to build consensus.

The threats to the value of ecosystem goods and services of the Mississipi delta

The Mississippi delta, North America’s largest river delta, is also one of the continent’s most important coastal ecosystems, both in ecological and economic value. Over the past half century, however, the delta has deteriorated dramatically losing about 1.2 million acres (1900 km2) or about 25 % of the coastal wetlands that existed in the early twentieth century. Much of this loss is due to how the Mississippi River was transformed and managed in the twentieth century. Major dams, primarily on the Missouri River, trapped sediments and reduced sediment delivery to the Gulf by about 50 %. Flood control levees eliminated almost all riverine input to the deltaic plain. In addition, there was pervasive hydrologic alteration of the deltaic plain including oil and navigation canals, induced subsidence, and impoundment. We carried out an analysis of the valuation of ecosystem goods and services of the delta, including three scenarios for continued degradation, stabilization, and rebuilding of the delta. The goods and ecosystem services valued in this study include hurricane and flood protection, water supply, water quality, recreation and fisheries. Presently, the Mississippi River Delta ecosystems provide at least

Quality of life: An approach integrating opportunities, human needs, and subjective well-being

12–47 billion in benefits annually. If this natural capital were treated as an economic asset, the delta’s minimum capital asset value would be

An Integrative Approach to Quality of Life Measurement, Research, and Policy

330 billion to

Vegetation death and rapid loss of surface elevation in two contrasting Mississippi delta salt marshes: The role of sedimentation, autocompaction and sea-level rise

1.3 trillion (3.5 % discount rate). We examined three restoration scenarios. Scenario 1 is a “business as usual” scenario where the delta continues to deteriorate. Estimated losses associated with this option are an additional

Integrated ecological economic modeling of the Patuxent River watershed

41 billion not including estimates of damage from major future hurricanes (which could top