Marjorie M. Holland

The Sustainable Biosphere Initiative: An Ecological Research Agenda: A Report from the Ecological Society of America

In this document, the Ecological Society of America proposes the Sustainable Biosphere Initiative (SBI), an initiative that focuses on the necessary role of ecological science in the wise management of Earths resources and the maintenance of Earths life support systems. This document is intended as a call to arms for all ecologists, but it will also serve as a means to communicate with individuals in other disciplines with whom ecologists must join forces to address a common predicament. This document focuses primarily on the acquisition of ecological knowledge. It identifies the ecological research programs of highest priority and recommends steps required to pursue research objectives. The document also lays the groundwork for improving the communication and application of ecological knowledge. The SBI proposes three research priorities: global change; biological diversity; and sustainable ecological systems.

Ecotones--The Role of Landscape Boundaries in the Management and Restoration of Changing Environments.

1. Introduction: The role of landscape boundaries in the management and restoration of changing environments.- 2. Fundamental ecological characteristics of landscape boundaries.- 3. Climatic constraints and issues of scale controlling regional biomes.- 4. Potential responses of landscape boundaries to global environmental change.- 5. Simulation of the scale-dependent effects of landscape boundaries on species persistence and dispersal.- 6. Human impact on the functioning of landscape boundaries.- 7. Restoration of human impacted land-water ecotones.- 8. Summary: Landscape boundaries in the management and restoration of changing environments.

Agricultural Drainage Ditches Mitigate Phosphorus Loads as a Function of Hydrological Variability

Phosphorus (P) loading from nonpoint sources, such as agricultural landscapes, contributes to downstream aquatic ecosystem degradation. Specifically, within the Mississippi watershed, enriched runoff contributions have far-reaching consequences for coastal water eutrophication and Gulf of Mexico hypoxia. Through storm events, the P mitigation capacity of agricultural drainage ditches under no-till cotton was determined for natural and variable rainfall conditions in north Mississippi. Over 2 yr, two experimental ditches were sampled monthly for total inorganic P concentrations in baseflow and on an event-driven basis for stormflows. Phosphorus concentrations, Mannings equations with a range of roughness coefficients for changes in vegetative densities within the ditches, and discharge volumes from Natural Resources Conservation Service dimensionless hydrographs combined to determine ranges in maximum and outflow storm P loads from the farms. Baseflow regressions and percentage reductions with P concentrations illustrated that the ditches alternated between being a sink and source for dissolved inorganic P and particulate P concentrations throughout the year. Storm event loads resulted in 5.5% of the annual applied fertilizer to be transported into the drainage ditches. The ditches annually reduced 43.92 +/- 3.12% of the maximum inorganic effluent P load before receiving waters. Agricultural drainage ditches exhibited a fair potential for P mitigation and thus warrant future work on controlled drainage to improve mitigation capacity.

The Influence of Vegetation on Microbial Enzyme Activity and Bacterial Community Structure in Freshwater Constructed Wetland Sediments

Microorganisms play important roles in wetland ecosystems, but little is known about the influence of wetland plants on microbial community structure and activity. A greenhouse experiment was conducted to study the short-term influence of wetland vegetation on the sediment microbial community. Mesocosms were either planted with Juncus effusus, Carex lurida, or Dichanthelium acuminatum var. acuminatum or remained unvegetated. After eight weeks, sediment samples were taken and assayed for the activity of five microbial extracellular enzymes associated with carbon, nitrogen, and phosphorus cycling. β-1,4-glucosidase, phosphatase, and N-acetylglucosaminidase exhibited similar activity for all vegetation treatments, while the activity of the phenolic-degrading enzymes phenol oxidase and peroxidase was higher in sediments with no vegetation. Denaturing gradient gel electrophoresis and sequencing of partial 16S rRNA genes indicate differences in the sediment bacterial community associated with each plant regime. Acidobacteria, Firmicutes and Proteobacteria were the dominant phyla, although unvegetated sediments contained proportionally fewer Firmicutes and Alphaproteobacteria. This study provides insights into the structure of wetland bacterial communities and suggests that vegetation can influence both bacterial community structure and specific enzyme activity in wetland sediments. Moreover, these influences can occur over a relatively short time and could occur within just a few months of vegetation changes.

Resilience of forested wetlands located in the southeastern United States: Demonstration of a soil perturbation index

This study examined the usefulness of soil organic matter (SOM), total organic carbon (TOC), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) as indicators of resilience in forested wetlands located within southeast Virginia, USA. These data were also examined as standards for reference wetlands before and after timber harvesting and for comparisons of mature and early successional stages. Results indicate that the wetland soils in this study seem to be relatively resilient to perturbation. Soil total phosphorus was significantly greater in the 0- and 0.5-year stages than the 5-, 8-, and 14-year stages (p<0.05). Although there were no significant differences in SOM, TOC, and TKN levels before and after timber harvest or between early and mature successional stages, there were consistent trends that may prove beneficial in determining reference standards. A Soil Perturbation Index was developed by combining all four parameters for soils collected in the Chowan River watershed to determine extent of deviation from the biogeochemical reference. Using the model developed in this study, biogeochemical functions decrease after harvesting, with the low point reached at approximately 8 to 9 years after human alteration. This index predicts that it would take 16–17 years for SOM, TOC, TKN, and TP to return to pre-harvest conditions. Perturbation indices could be used for assessment of human impacts, restoration projects, and mitigation of wetlands. We maintain that a Soil Perturbation Index can be one useful component of an index of biotic integrity for wetland ecosystems.

Phosphorus Release due to Decomposition of Wetland Plants

Agricultural activities are major sources of non-point pollutants causing eutrophication. Vegetated constructed wetlands are used as a best management practice for sequestration of nutrients from agricultural runoff. However, plants release nutrients back into the system as they decompose after senescence, affecting the nutrient removal efficiency of a constructed wetland. This information is important for a focused selection of plants and for improving the effectiveness of a constructed wetland. A greenhouse experiment was conducted to study the release of phosphorus by common freshwater macrophytes - Juncus effusus, Carex lurida and Dichanthelium acuminatum var. acuminatum during plant decomposition. Microcosms with the mixed culture of these three species showed higher phosphorus retention rates compared to monoculture microcosms. Results indicate that plant species differ in their nutrient removal efficiencies when grown in the mixed culture compared to monoculture treatments, indicating that nutrient removal efficiencies vary with plant species composition. Thus, plant species may play an important role in determining the phosphorus removal rates of vegetated constructed wetlands.

Management of land / inland water ecotones: needs for regional approaches to achieve sustainable ecological systems

Evidence suggests that the boundaries between rivers, floodplain wetlands, and adjacent upland communities are among the most important components of landscapes. In a landscape context, floodplain wetlands and their ecotones are important transition zones between uplands and aquatic ecosystems. Management of wetland patches and ecotones to achieve sustainable ecosystems requires action on a broad scale, giving consideration to all factors affecting wetlands and the drainage basins of which they are a part. In northeastern United States, a struggle to identify new sources of water has focussed attention on the sustainability of aquatic ecosystems.

A Floristic Survey and Comparison of Marsh Vegetation Ranging From Non-Tidal Freshwater To Ocean Salinities Along the Elbe (Germany) and Connecticut (Northeastern USA) Rivers

Abstract Relationships between the flora and vegetation of northern Europe and the northeastern United States have been long noted but little studied. Here, quantitative sampling of high, low, and mid-marsh zones was carried out in 20 marshes along a gradient from non-tidal freshwater via tidal freshwater and brackish to salt marshes in each of two large river systems, the Elbe in Europe (Germany) and the Connecticut in North America (southern New England, USA). The composition of each zone of each marsh type in the two river systems is described. The marsh floras are compared, and possible reasons for differences in vegetation composition, non-native species occurrences, species richness patterns, and the origin of marsh floras are discussed. Twenty-two species occurred in both river systems, nearly 10% of the total marsh flora. Shared species were found in all four marsh types and occasionally in more than one marsh type. Introduced taxa are not prominent in either river system except for Spartina anglica C. E. Hubb. in the salt marshes and Acorus calamus L. in the non-tidal freshwater marshes of the Elbe and Typha angustifolia L. and Phragmites australis (Cav.) Trin. ex Steud. in the brackish marshes along the Connecticut. Asteraceae and Poaceae were the largest (most species rich) families in the marshes of both rivers. These descriptions and comparisons of the marsh flora and vegetation of a European and an American river should serve as benchmarks for future comparisons and assessments of changes in times of rapid environmental and associated ecological change.

Vegetation Changes in Temperate Forested Island Communities in Lake Winnipesaukee, New Hampshire, USA

Abstract We documented changes in overstory species composition and foliar cover during a 23-year sampling period, compared woody species on three small islands in Lake Winnipesaukee, New Hampshire, and determined changes in dominant plant species over time. Floristic surveys had begun on these islands in 1901, and provided valuable information about earlier vascular plant composition. Three Mile Island, Hawks Nest Island, and Blueberry Island were first sampled quantitatively in 1978, again in 1991, and most recently in 2001. The data compiled here are for woody vascular plant species found in long-term monitoring plots on the islands owned and/or managed by the Appalachian Mountain Club. Pinus resinosa, P. strobus, and Tsuga canadensis were the three most dominant species on Hawks Nest throughout the study period. On Blueberry Island, Acer rubrum, Betula populifolia, and T. canadensis were the three most dominant woody species when sampling began. However, by 2001 Ilex verticillata, Myrica gale, and Vaccinium corymbosum were the three most dominant species. On Three Mile Island, P. strobus and Quercus rubra were the two most dominant species in 1978, but by 2001 A. pensylvanicum and Hamamelis virginiana were the dominants. Overall species richness within the permanent plots increased on Three Mile and Blueberry Islands, while the total number of species remained relatively constant on Hawks Nest Island.

Study of Understory Vegetation at The University of Mississippi Field Station in North Mississippi

Abstract The University of Mississippi Field Station is a 300-hectare area located in the Eocene Hills of the interior coastal plain of the southeastern US. Twenty long-term monitoring plots were established in 1996 following a major ice storm. Plots were sampled for understory (vegetation less than 1.5 m height) vegetation from 1996 to 2008 to study the changes in vegetation due to natural disturbance and to study the spread of invasive species. Species richness, total percent foliar cover, total percent open space and importance values (based on frequency and cover) were determined. Results indicate that there are 345 vascular plant species belonging to 90 families at the University of Mississippi Field Station (UMFS). Poaceae was the most abundant family followed by Asteraceae and Fabaceae. Understory species richness increased from 73 in 1996 to 195 in 2008. Mean percent foliar cover decreased from 58% in 1996 to 32% in 2008. Importance values for the invasive species Microstegium vimineum and Lonicera japonica decreased in 2008. Native species such as Andropogon virginicus and Vitis rotundifolia became dominant in 2008. Thus, there was a shift in vegetation with native species becoming more prevalent and displacing invasive species.