Nutrient Concentration Targets to Achieve Periphyton Biomass Objectives Incorporating Uncertainties

Nutrient concentration targets are an important component of managing river eutrophication. Relationships between periphyton biomass and site characteristics for 78 gravel‐bed rivers in New Zealand were represented by regression models. The regression models had large uncertainties but identified broad‐scale drivers of periphyton biomass. The models were used to derive concentration targets for the nutrients, total nitrogen (TN) and dissolved reactive phosphorous (DRP), for 21 river classes to achieve periphyton biomass thresholds of 50, 120, and 200 mg chlorophyll a m^?2. The targets incorporated a temporal exceedance criterion requiring the specified biomass threshold not be exceeded by more than 8% of samples. The targets also incorporated a spatial exceedance criterion requiring the biomass thresholds will not be exceeded at more than a fixed proportion (10%, 20%, or 50%) of locations. The spatial exceedance criterion implies, rather than requiring specific conditions at individual sites, the objective is to restrict biomass to acceptable levels at a majority of locations within a domain of interest. A Monte Carlo analysis was used to derive the uncertainty of the derived nutrient concentration targets for TN and DRP. The uncertainties reduce with increasing size of the spatial domain. Tests indicated the nutrient concentration targets were reasonably consistent with independent periphyton biomass data despite differences in the protocols used to measure biomass at the training and test sites.     

Trace elements in the shoreline and seabed sediments of the southern Caspian Sea: investigation of contamination level,distribution, ecological and human health risks,and elemental partition coefficient

Environmental Science and Pollution Research - This study assesses the occurrence of trace elements (TEs) in sediments of the southern Caspian Sea. A total of 16 shoreline sediment samples and 15...     

Ecological consequences of forest elephant declines for Afrotropical forests

Poaching is rapidly extirpating African forest elephants (Loxodonta cyclotis) from most of their historical range, leaving vast areas of elephant‐free tropical forest. Elephants are ecological engineers that create and maintain forest habitat; thus, their loss will have large consequences for the composition and structure of Afrotropical forests. Through a comprehensive literature review, we evaluated the roles of forest elephants in seed dispersal, nutrient recycling, and herbivory and physical damage to predict the cascading ecological effects of their population declines. Loss of seed dispersal by elephants will favor tree species dispersed abiotically and by smaller dispersal agents, and tree species composition will depend on the downstream effects of changes in elephant nutrient cycling and browsing. Loss of trampling and herbivory of seedlings and saplings will result in high tree density with release from browsing pressures. Diminished seed dispersal by elephants and high stem density are likely to reduce the recruitment of large trees and thus increase homogeneity of forest structure and decrease carbon stocks. The loss of ecological services by forest elephants likely means Central African forests will be more like Neotropical forests, from which megafauna were extirpated thousands of years ago. Without intervention, as much as 96% of Central African forests will have modified species composition and structure as elephants are compressed into remaining protected areas. Stopping elephant poaching is an urgent first step to mitigating these effects, but long‐term conservation will require land‐use planning that incorporates elephant habitat into forested landscapes that are being rapidly transformed by industrial agriculture and logging.     

Incorporating governance influences into social-ecological system models: a case study involving biodiversity conservation

Addressing environmental problems requires sophisticated approaches to complexity and uncertainty. Conceptual models are increasingly used to improve understanding of complex system interactions. However, cursory treatment of governance limits their analytical potential. This study included governance considerations in a social-ecological system model of biodiversity conservation in the Tasmanian Midlands (Australia). Effectiveness of engagement processes and conservation programme longevity were identified as critical governance influences. The conceptual representation of this system enabled exploration of how governance influences interact with social drivers (e.g. landholder engagement in conservation practices) to modify the effect of biophysical drivers (e.g. land use) on biodiversity outcomes. Such a methodology provides essential information for identifying and guiding governance related points of intervention.     

A century of increasing pine density and associated shifts in understory plant strategies

We analyzed one of the longest-term ecological data sets to evaluate how forest overstory structure is related to herbaceous understory plant strategies in a ponderosa pine forest. Eighty-two permanent 1-m2 chart quadrats that were established as early as 1912 were remeasured in 2007. We reconstructed historical forest structure using dendrochronological techniques. Ponderosa pine basal area increased from an average of 4 m2/ha in the early 1900s to 29 m2/ha in 2007. Understory plant foliar cover declined by 21%, species richness declined by two species per square meter, and functional diversity also declined. The relative cover of C4 graminoids decreased by 18% and C3 graminoids increased by 19%. Herbaceous plant species with low leaf and fine root nitrogen concentrations, low specific leaf area, high leaf dry matter content, large seed mass, low specific root length, short maximum height, and early flowering date increased in relative abundance in sites where pine basal area increased the most. Overall, we observed a long-term shift in composition toward more conservative shade- and stress-tolerant herbaceous species. Our analysis of temporal changes in plant strategies provides a general framework for evaluating compositional and functional changes in terrestrial plant communities.     

Limitations of the CLEA model when assessing human health risks from dioxins and furans in soil at an allotments site in Rochdale, NW England

Many allotments in the UK today are situated on urban brownfield areas which creates a potential human health risk from soil borne contamination. This paper looks specifically at the risks to allotment users at a site in Rochdale, UK, from polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-furans (PCDD and PCDF). A contaminated land investigation was undertaken involving the collection and analysis of 24 soil samples from the top 0.0-0.3 m of the soil profile. Homogenised egg samples were also collected and analysed from plots where poultry were kept. The concentration of PCDD and PCDF in soil at the site varied from 0.69 to 13.62 μg kg(-1); two plots out of a total of eight exceeded the soil guideline value (SGV) of 8 μg kg(-1), however all plots fell below the site specific assessment criteria (SSAC) of 15.9 μg kg(-1). Human health risks were assessed using the Environment Agency's contaminated land exposure assessment (CLEA) model. The assessment using CLEA alone did not provide enough evidence to indicate significant possibility of significant harm (SPOSH) across the entire allotment site. However, when the likely exposure from the soil was combined with potential exposure from consumption of site laid eggs, the results indicated that the potential risks could constitute SPOSH. This paper gives evidence to support the bioconcentration of PCDD and PCDF in eggs and highlights the importance of considering pollutant linkages outside the generic CLEA model.     

The re-imagining of a framework for agricultural land use: A pathway for integrating agricultural practices into ecosystem services,planetary boundaries and sustainable development goals: This article belongs to Ambio’s 50th Anniversary Collection. Theme: Agricultural land use

This paper reflects on the legacy of the Ambio papers by Sombroek et al. (1993), Turner et al. (1994), and Brussaard et al. (1997) on the study of agricultural land use and its impacts on global carbon storage and nutrient dynamics. The papers were published at a time of transition in ecology that involved the integration of humans as components of ecosystems, the formulation of the ecosystem services, and emergence of sustainability science. The papers offered new frameworks to studying agricultural land use across multiple scales in a way that captured causality from interacting components of the system. Each paper argued for more comprehensive data sets; foreseeing the power of network-based science, the potential of molecular technologies to assess biodiversity, and advances in remote sensing. The papers have contributed both conceptual framings and methodological approaches to an ongoing movement to identify a pathway to study agricultural land use and environmental change that fit within the concepts of ecosystem services, planetary boundaries and sustainable development goals.     

Mitigation of atrazine, S-metolachlor, and diazinon using common emergent aquatic vegetation

By the year 2050, the population of the United States is expected to reach over 418 million,while the global population will reach 9.6 billion. To provide safe food and fiber, agriculture must balance pesticide usage against impacts on natural resources. Challenges arise when storms cause runoff to be transported to aquatic receiving systems. Vegetated systems such as drainage ditches and constructed wetlands have been proposed as management practices to alleviate pesticide runoff. Twelve experimental mesocosms(1.3 × 0.71 × 0.61 m) were filled with sediment and planted with a monoculture of one of three wetland plant species(Typha latifolia, Leersia oryzoides, and Sparganium americanum).Three mesocosms remained unvegetated to serve as controls. All mesocosms were amended with 9.2 ± 0.8 μg/L, 12 ± 0.4 μg/L, and 3.1 ± 0.2 μg/L of atrazine, metolachlor, and diazinon, respectively, over a 4 hr hydraulic retention time to simulate storm runoff.Following the 4 hr amendment, non-amended water was flushed through mesocosms for an additional 4 hr. Outflow water samples were taken hourly from pre-amendment through8 hr, and again at 12, 24, 48, 72, and 168 hr post-amendment. L. oryzoides and T. latifolia had mean atrazine, metolachlor, and diazinon retentions from 51%–55% for the first 4 hr of the experiment. Aside from S. americanum and atrazine(25% retention), unvegetated controls had the lowest pesticide retention(17%–28%) of all compared mesocosms. While native aquatic vegetation shows promise for mitigation of pesticide runoff, further studies increasing the hydraulic retention time for improved efficiency should be examined.     

Vested Interest theory and disaster preparedness

Three studies were designed to extend a combination of vested interest theory (VI) and the extended parallel process model of fear appeals (EPPM) to provide formative research for creating more effective disaster preparedness social action campaigns. The aim was to develop an effective VI scale for assessing individual awareness and ‘vestedness’ relevant to disaster preparedness. Typical preparedness behaviours are discussed with emphasis on earthquakes and tornados in particular. Brief overviews of VI and the EPPM are offered, and findings are presented from three studies (one dealing with earthquakes, and two with tornados) conducted to determine the factor structure of the key VI components involved, and to develop and test subscales derived from the two theories. The paper finishes with a discussion of future research needs and suggestions on how the new subscales may be applied in the design and execution of more effective disaster preparedness campaigns.