Jay F. Martin

Interaction and spatial distribution of wetland nitrogen processes

A spatially-explicit, two-dimensional model was developed to evaluate the processes which determine the fate and transport of nitrogen (N) in wetland systems. The wetland soil profile was partitioned into floodwater, and aerobic, and anaerobic soil layers, with diffusion and settling accounting for the transport of N between layers. Nitrogen transformations considered in the model were; enzyme hydrolysis, mineralization, nitrification, NH4-N adsorption/desorption, NH3-N volatilization, denitrification, and vegetative assimilation and decay. Most processes were represented with first-order kinetics, except vegetative uptake, which was represented with Michaelis–Menten kinetics. STELLA® iconographic software was used to simulate processes regulating N removal from wetlands. Denitrification, ammonia volatilization, and accretion of organic N were identified as major pathways accounting for N removal. Downward flux of NO3− from floodwater to soil limited N removal through denitrification. Denitrification rates increased from 13 to 88 g N year−1 in response to augmented vertical flux of soluble N, caused by increasing diffusion coefficients two orders of magnitude. Edaphic organic N storage, through the production of inorganic N, negatively impacted N removal. Spatial simulation illustrated the phenomena of diminishing returns in the mass removal rates of N, which were in agreement with documented values.

Methane production in low-cost, unheated, plug-flow digesters treating swine manure and used cooking grease

A co-digestion investigation was conducted using small-scale digesters in Costa Rica to optimize their ability to treat animal wastewater and produce renewable energy. Increases in methane production were quantified when swine manure was co-digested with used cooking grease in plug-flow digesters that operated at ambient temperate without mixing. The co-digestion experiments were conducted on 12 field-scale digesters (250 L each) using three replications of four treatment groups: the control (T0), which contained only swine manure and no waste oil, and T2.5, T5, and T10, which contained 2.5%, 5%, and 10% used cooking grease (by volume) combined with swine manure. The T2.5 treatment had the greatest methane (CH(4)) production (45 L/day), a 124% increase from the control, with a total biogas production of 67.3 L/day and 66.9% CH(4) in the produced biogas. Increasing the grease concentration beyond T2.5 produced biogas with a lower percentage of CH(4), and thus, did not result in any additional benefits. A batch study showed that methane production could be sustained for three months in digesters that co-digested swine manure and used cooking grease without daily inputs. The investigation proved that adding small amounts of grease to the influent is a simple way to double energy production without affecting other digester benefits.

Lacandon Maya ecosystem management: sustainable design for subsistence and environmental restoration

Indigenous groups have designed and managed their ecosystems for generations, resulting in biodiversity protection while producing for their familys needs. Here we describe the agroecosystem of the Lacandon Maya, an indigenous group who live in Chiapas, Mexico. The Lacandon practice a form of swidden agriculture that conserves the surrounding rain forest ecosystem while cycling the majority of their land through five successional stages. These stages include an herbaceous stage, two shrub stages, and two forest stages. A portion of their land is kept in primary forest. This study presents the Lacandon traditional ecological knowledge (TEK) for agroforestry and quantitatively describes the plant community and the associated soil ecology of each successional stage. Also documented is the knowledge of the Lacandon regarding the immediate use of plant species and plant species useful for soil fertility enhancement. Woody plant diversity increases during the successional stages of the Lacandon system, and by the beginning of the first forest stage, the diversity is similar to that of the primary forest. In all stages, Lacandon use 60% of the available plant species for food, medicine, and raw materials. Approximately 45% of the woody plant species present in each fallow stage were thought by the Lacandon to enhance soil fertility. Total soil nitrogen and soil organic matter increased with successional stage and with time from intentional burn. Nutrient and soil nematode dynamics in shrub stages related to the presence of introduced and managed plants, indicating engineered soil enhancement by the Lacandon. The effects on biodiversity and soil ecology coupled with productivity for agricultural subsistence indicate that Lacandon TEK may offer tools for environmental conservation that would provide for a familys basic needs while maintaining a biodiverse rain forest ecosystem. Tools such as these may offer options for regional restoration and conservation efforts such as the Mesoamerican Biological Corridor in Mexico and Central America, where attainment of environmental goals must include methods to provide resources to local inhabitants.

Emergy valuation of diversions of river water to marshes in the Mississippi River Delta

Abstract River diversions within the Mississippi Delta deliver river water and associated sediments and nutrients to interior marshes that were previously isolated from river inputs by elevated levees. When isolated from river inputs, the marshes subside and deteriorate to open water, resulting in ecological and economic losses. River diversions are an ecological engineering method to reverse this trend by restoring controlled flows of river water through modified levees. This study compares the cost of constructing and operating the diversions with potential benefits to determine whether the diversions yield a net public benefit. The Caernarvon and Davis Pond river diversions were evaluated using emergy analysis to provide a common basis to quantify and compare economic and ecological costs and benefits. The analysis quantified high concentrations of natural resources inherent to deltas and demonstrated benefits produced by investing economic resources in river diversions to capture and utilize renewable resources. The diversions resulted in large net emergy yield ratios (33.2 and 9.36) that varied depending on the rate of marsh gain produced by the diversions.

Effects of Typha latifolia transpiration and harvesting on nitrate concentrations in surface water of wetland microcosms.

AbtractThis experiment tested the hypothesis that the movement of water into the soil due to macrophyte transpiration stimulates nitrate removal from wetlands. The short-term impacts of biomass harvesting upon the ability of wetlands to reduce nitrate concentrations were also investigated. Different amounts of biomass were harvested fromTypha latifolia specimens to create three treatments of varying transpiration rates. Harvesting and the resulting different rates of transpiration explained between 10 and 38% of the variation in nitrate reduction during the 10-day experiment and had significant effects upon nitrate concentrations. Greater rates of harvesting and lower rates of transpiration resulted in decreased reductions of nitrate in the surface water of the microcosms. During the first four days of the experiment, 70% and 85% rates of aboveground harvesting reduced transpiration by 63% and 91%, respectively. These changes led to respective decreases in nitrate reduction of 16% and 31% compared to unharvested treatments. Differences in nitrate reduction between the treatments were minimal in the later days of the experiment as nitrate concentrations decreased. Results support the hypothesis that water movement due to plant uptake contributes, to nitrogen removal and offers a partial explanation for increased nitrogen removal in vegetated wetland treatment systems. Decreased reduction of nitrate with greater harvesting demonstrates potential negative impacts on water quality improvement when using wetlands as bio-energy production systems.

Transient Social–Ecological Stability: the Effects of Invasive Species and Ecosystem Restoration on Nutrient Management Compromise in Lake Erie

Together, lake ecosystems and local human activity form complex social-ecological systems (SESs) characterized by feedback loops and discontinuous change. Researchers in diverse fields have suggested that complex systems do not have single stable equilibria in the long term because of inevitable perturbation. During this study, we sought to address the general question of whether or not stable social- ecological equilibria exist in highly stressed and managed lacustrine systems. Using an integrated human- biophysical model, we investigated the impacts of a species invasion and ecosystem restoration on SES equilibrium, defined here as a compromise in phosphorus management among opposing stakeholders, in western Lake Erie. Our integrated model is composed of a calibrated ecological submodel representing Sandusky Bay, and a phosphorus management submodel that reflects the societal benefits and costs of phosphorus regulation. These two submodels together form a dynamic feedback loop that includes freshwater ecology, ecosystem services, and phosphorus management. We found that the invasion of dreissenid mussels decreased ecosystem resistance to eutrophication, necessitating increased phosphorus management to preserve ecosystem services and thus creating the potential for a shift in social-ecological equilibrium. Additionally, our results suggest that net benefits in the region following the invasion of dreissenids may never again reach the pre-invasion level if on-site phosphorus control is the sole management lever. Further demonstrating transient system stability, large-scale wetland restoration shifted points of management compromise to states characterized by less on-site phosphorus management and higher environmental quality, resulting in a significant increase in net benefits in the region. We conclude that lacustrine SESs are open and dynamic, and we recommend that future models of these systems emphasize site-specific perturbation over equilibrium, thereby aiding the development of management plans for building system resistance to undesirable change that are both flexible and sustainable in an unknowable future.

Emergy Evaluation of Lacandon Maya Indigenous Swidden Agroforestry in Chiapas, Mexico

The Lacandon Maya of Chiapas, Mexico practice a system of swidden agroforestry that mimics the surrounding ecosystem and its successional stages. Their fields rotate through grass (milpa), and shrub (acahual) and forest fallow stages that regenerate soil, nutrients, and seed banks. Each successional stage, including the fallow stages, produces over 25 types of crops, raw materials, and medicines. Lacandon traditionally do not use fertilizers, pesticides or herbicides. An emergy evaluation of Lacandon agroforestry was conducted to quantify resource use, productivity, environmental impact, and overall sustainability. Six systems were analyzed. The Emergy Yield Ratios of the systems ranged from 4.5 to 50.7, which indicated a high level of output per purchased investments. The agroforestry systems had minimal environmental impacts as shown by Environmental Loading Ratios between 0.03 and 0.38. The Emergy Sustainability Index (ESI) of the systems ranged from 12 to 1740, indicating a high level of sustainability. The high ESI values were partially due to a large fraction of renewable resources that varied from 0.72 to 0.97. ESI was dependent upon land area devoted to the system for each family, where greater land area resulted in higher values of ESI. Labor invested did not exhibit a direct effect on sustainability.

EFFECT OF A WOODY (SALIX NIGRA) AND AN HERBACEOUS (JUNCUS EFFUSUS) MACROPHYTE SPECIES ON METHANE DYNAMICS AND DENITRIFICATION

Wetlands improve water quality through denitrification, but these ecosystems are also an important source of the greenhouse gas, methane. The objective of this research was to determine the effect of two common macrophyte species (Juncus effusus and Salix nigra) on denitrification and on the methane cycle. The research was conducted in a newly constructed wetland on the Columbus campus of The Ohio State University during two growing seasons. In the wetland, some plots were left unplanted, while others were planted with Salix or Juncus species (i.e., 3 treatments; n = 15 per treatment). For each treatment, we quantified concentrations of methane at two depths (15 and 25 cm) in the sediment, emissions of methane from the sediment and through the plants, and denitrification rates. During most of the second growing season, both species had a limited effect on denitrification and methanogenesis. The effects of the plants became evident by the end of the second growing season and during the third growing season. During the third growing season, Salix species enhanced the release of the greenhouse gas methane to the atmosphere, while Juncus limited the emission of methane. In comparison to the unplanted plots, the long-term removal of nitrate by denitrification was favored in the plots planted with Juncus and was not affected by Salix. Our study provides evidence that certain plants (such as Juncus) can be planted in constructed wetlands to favor denitrification, while buffering methane emission.

Reduction of pathogen indicator organisms in dairy wastewater using an ecological treatment system.

Ecological treatment systems can provide a sustainable, plant-based alternative to traditional wastewater treatment. One factor essential to the success of these systems is ensuring their ability to reduce coliform concentrations in wastewater. Wastewater is the primary source of fecal contamination in aquatic ecosystems, containing total and fecal coliforms on the order of 10(8)-10(10) and 10(7)-10(9) CFU L(-1), respectively. This study assessed the ability of an ecological treatment system to reduce concentrations of total coliforms and Escherichia coli from dairy wastewater. Low strength wastewater was pumped into the system during July of 2005 and high strength in September 2005. Wastewater passes through a series of anaerobic, aerobic, and clarifier reactors and wetland cells before exiting the system. Regardless of wastewater strength, average total coliform and E. coli concentrations were consistently reduced by at least 99% from influent to effluent, with the majority of the reduction (76%) occurring in the first two reactors. Relationships between internal concentrations of solids and coliforms indicated that increased reduction of solids may further reduce coliform concentrations. Although U.S. Environmental Protection Agency discharge requirements for E. coli were not always met, the substantial reductions achieved indicate that ecological treatment systems have the potential to successfully reduce coliforms in wastewater to meet discharge limits. The results from this study will be used to guide design and management of future ecological treatment systems, so that larger and more consistent coliform reductions can be achieved.

Emergy evaluation of food production in urban residential landscapes

To transform cities from heterotrophic into sustainable ecosystems many authors have called for increased food production, including home gardening, in urban areas. We conducted an emergy analysis of four model backyard landscape plots—a conventional ornamental landscape, an intensive organic garden, an edible landscape, and a forest garden—to assess the yield and sustainability of these systems. Data were collected during the 2001 growing season and extrapolated to make a five year projection. In the 2001 season, all plots had low Emergy Yield Ratios (EYR) of between 0.0003 and 0.17 and extremely low Emergy Sustainability Indices (SI). In the five year projection, all plots still had low EYRs of between 0.0008 and 0.33 and very low SIs. These low indices are due primarily to the high levels of economic inputs required for the installation and maintenance of these plots in an urban context. Analyses performed on larger systems (households, neighborhoods and cities) containing productive landscapes such as those studied here may produce different results. Installing food-producing landscapes in urban areas without altering the networks by which such landscapes are supplied, however, may not substantially alter the heterotrophic nature of cities.