Quantifying and Evaluating Ecosystem Health: A Case Study from Moreton Bay, Australia

As part of the program monitoring the ecosystem health of Moreton Bay, Queensland, Australia, we developed a means for assessing ecosystem health that allows quantitative evaluation and spatial representations of the assessments. The management objectives for achieving ecosystem health were grouped into ecosystem objectives, water quality objectives, and human health objectives. For the first two groups, aspects of the ecosystem (e.g., trophic status) were identified, and an indicator was chosen for each aspect. Reference values for each indicator were derived from management objectives and compared with the mapped survey values. Subregions for which the indicator statistic was equal to or better than the assigned reference value are referred to as “compliant zones.” High-resolution surface maps were created from spatial predictions on a fine hexagonal grid for each of the indicators. Eight reporting subregions were established based on the depth and predicted residence times of the water. Within each reporting subregion, the proportion that was compliant was calculated. These results then were averaged to create an integrated ecosystem health index. The ratings by a team of ecosystem experts and the calculated ecosystem health indices had good correspondence, providing assurance that the approach was internally consistent, and that the management objectives covered the relevant biologic issues for the region. This method of calculating and mapping ecosystem health, relating it directly to management objectives, may have widespread applicability for ecosystem assessment.     

A Quantitative Tool for Assessing the Integrity of Southern Coastal California Streams

We developed a benthic macroinvertebrate index of biological integrity (B-IBI) for the semiarid and populous southern California coastal region. Potential reference sites were screened from a pool of 275 sites, first with quantitative GIS landscape analysis at several spatial scales and then with local condition assessments (in-stream and riparian) that quantified stressors acting on study reaches. We screened 61 candidate metrics for inclusion in the B-IBI based on three criteria: sufficient range for scoring, responsiveness to watershed and reach-scale disturbance gradients, and minimal correlation with other responsive metrics. Final metrics included: percent collector-gatherer + collector-filterer individuals, percent noninsect taxa, percent tolerant taxa, Coleoptera richness, predator richness, percent intolerant individuals, and EPT richness. Three metrics had lower scores in chaparral reference sites than in mountain reference sites and were scored on separate scales in the B-IBI. Metrics were scored and assembled into a composite B-IBI, which was then divided into five roughly equal condition categories. PCA analysis was used to demonstrate that the B-IBI was sensitive to composite stressor gradients; we also confirmed that the B-IBI scores were not correlated with elevation, season, or watershed area. Application of the B-IBI to an independent validation dataset (69 sites) produced results congruent with the development dataset and a separate repeatability study at four sites in the region confirmed that the B-IBI scoring is precise. The SoCal B-IBI is an effective tool with strong performance characteristics and provides a practical means of evaluating biotic condition of streams in southern coastal California.     

Hot Spots of Perforated Forest in the Eastern United States

National assessments of forest fragmentation satisfy international biodiversity conventions, but they do not identify specific places where ecological impacts are likely. In this article, we identify geographic concentrations (hot spots) of forest located near holes in otherwise intact forest canopies (perforated forest) in the eastern United States, and we describe the proximate causes in terms of the nonforest land-cover types contained in those hot spots. Perforated forest, defined as a 0.09-ha unit of forest that is located at the center of a 7.29-ha neighborhood containing 60–99% forest with relatively low connectivity, was mapped over the eastern United States by using land-cover maps with roads superimposed. Statistically significant (P < 0.001) hot spots of high perforation rate (perforated area per unit area of forest) were then located by using a spatial scan statistic. Hot spots were widely distributed and covered 20.4% of the total area of the 10 ecological provinces examined, but 50.1% of the total hot-spot area was concentrated in only two provinces. In the central part of the study area, more than 90% of the forest edge in hot spots was attributed to anthropogenic land-cover types, whereas in the northern and southern parts it was more often associated with seminatural land cover such as herbaceous wetlands.     

In situ ground water denitrification in stratified, permeable soils underlying riparian wetlands

The ground water denitrification capacity of riparian zones in deep soils, where substantial ground water can flow through low-gradient stratified sediments, may affect watershed nitrogen export. We hypothesized that the vertical pattern of ground water denitrification in riparian hydric soils varies with geomorphic setting and follows expected subsurface carbon distribution (i.e., abrupt decline with depth in glacial outwash vs. negligible decline with depth in alluvium). We measured in situ ground water denitrification rates at three depths (65, 150, and 300 cm) within hydric soils at four riparian sites (two per setting) using a 15N-enriched nitrate "push-pull" method. No significant difference was found in the pattern and magnitude of denitrification when grouping sites by setting. At three sites there was no significant difference in denitrification among depths. Correlations of site characteristics with denitrification varied with depth. At 65 cm, ground water denitrification correlated with variables associated with the surface ecosystem (temperature, dissolved organic carbon). At deeper depths, rates were significantly higher closer to the stream where the subsoil often contains organically enriched deposits that indicate fluvial geomorphic processes. Mean rates ranged from 30 to 120 microg N kg(-1) d(-1) within 10 m versus <1 to 40 microg N kg(-1) d(-1) at >30 m from the stream. High denitrification rates observed in hydric soils, down to 3 m within 10 m of the stream in both alluvial and glacial outwash settings, argue for the importance of both settings in evaluating the significance of riparian wetlands in catchment-scale N dynamics.     

Atrazine sorption-desorption hysteresis by sugarcane mulch residue

Sorption and desorption kinetics are essential components for modeling the movement and retention of applied agricultural chemicals in soils and the fraction of chemicals susceptible to runoff. In this study, we investigated the retention characteristics of sugarcane (Saccharum spp. hybrid) mulch residue for atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) based on studies of sorption-desorption kinetics. A sorption kinetic batch method was used to quantify retention of the mulch residue for a wide range of atrazine concentrations and reaction times. Desorption was performed following 504 h of sorption using successive dilutions, followed by methanol extraction. Atrazine retention by the mulch residue was well described using a linear model where the partitioning coefficient (K(d)) increased with reaction time from 10.40 to 23.4 cm3 g(-1) after 2 and 504 h, respectively. Values for mulch residue K(d) were an order of magnitude higher than those found for Commerce silt loam (fine-silty, mixed, superactive, nonacid, thermic Fluvaquentic Endoaquepts) where the sugarcane crop was grown. A kinetic multireaction model was successful in describing sorption behavior with reaction time. The model was equally successful in describing observed hysteretic atrazine behavior during desorption for all input concentrations. The model was concentration independent where one set of model parameters, which was derived from all batch results, was valid for the entire atrazine concentration range. Average atrazine recovery following six successive desorption steps were 63.67 +/- 4.38% of the amount adsorbed. Moreover, a hysteresis coefficient based on the difference in the area between sorption and desorption isotherms was capable of quantifying hysteresis of desorption isotherms.     

Sustainable land application: an overview

Man has land-applied societal nonhazardous wastes for centuries as a means of disposal and to improve the soil via the recycling of nutrients and the addition of organic matter. Nonhazardous wastes include a vast array of materials, including manures, biosolids, composts, wastewater effluents, food-processing wastes, industrial by-products; these are collectively referred to herein as residuals. Because of economic restraints and environmental concerns about land-filling and incineration, interest in land application continues to grow. A major lesson that has been learned, however, is that the traditional definition of land application that emphasizes applying residuals to land in a manner that protects human and animal health, safeguards soil and water resources, and maintains long-term ecosystem quality is incomplete unless the earning of public trust in the practices is included. This overview provides an introduction to a subset of papers and posters presented at the conference, "Sustainable Land Application," held in Orlando, FL, in January 2004. The USEPA, USDA, and multiple national and state organizations with interest in, and/or responsibilities for, ensuring the sustainability of the practice sponsored the conference. The overriding conference objectives were to highlight significant developments in land treatment theory and practice, and to identify future research needs to address critical gaps in the knowledge base that must be addressed to ensure sustainable land application of residuals.     

Explaining the Performance of Mature Municipal Solid Waste Recycling Programs

This paper assesses the contextual, programmatic and decision-making factors that affect the performance of mature municipal solid waste recycling programs. Tobit models were prepared for cities with populations of less than or more than 25?000 to facilitate analysis of recycling performance. Recycling participation rates were found to be higher among cities in both groups that offered more convenient recycling programs and whose residents had a higher mean household income. The larger cities that achieved higher participation rates employed a decision-making process known as ‘collaborative learning’, imposed sanctions on improper sorting recyclable materials, and had a larger non-minority population. Among smaller cities, higher participation was attained by using variable fee pricing for solid waste collection and by mandating household participation. The study findings suggest that future research should focus on improved ways to characterize and measure the decision-making processes used to make policy changes in order to facilitate analysis of the causal and temporal relationships between decision-making processes and program performance.     

Prescribed burning effects on summer elk forage availability in the subalpine zone, Banff National Park, Canada

The effects of prescribed burning on forage abundance and suitability for elk (Cervus elaphus) during the snow-free season was evaluated in east-central Banff National Park, Canada. Six coniferous forest and mixed shrub-herb plant communities (n=144 plots), and 5223ha of burned (n=131) vegetation <12 years old were sampled using a stratified semi-random design. Sampling units represented various combinations of vegetation, terrain conditions, and stand ages that were derived from digital biophysical data, with plant communities the basic unit of analysis. Burning coniferous forest stands reduced woody biomass, and increased herbaceous forage from 146 to 790 kg/ha. Increases commonly occurred in the percent cover of hairy wild rye (Leymus innovatus (Beal) Pigler) and fireweed (Chamerion angustifolium (L.) Holub.). The herbaceous components of mixed shrub-herb communities increased from 336-747 kg/ha to 517-1104 kg/ha in response to burning (P<0.025, Mann-Whitney U-test). Browse biomass (mostly Salix spp. and Betula nana L.) increased >or=220% (P相似文献   

Botswana's environmental policy on recycling

Recycling operations have become one of the primary strategies for waste management, worldwide. Especially, recycling operations are viewed as among the most effective techniques for reducing the amount of municipal solid waste disposed at landfill sites. Botswana's environmental policy on recycling stipulates, among others, that all waste management authorities should provide information on the classification and quantities of controlled waste targeted for recycling. This paper, therefore, examines the extent to which recycling operations in Botswana have either been conducted in compliance with or in violation of some major environmental requirements as enunciated on statutory guidelines. Compatibility between environmental policies on recycling and actual practice is evaluated focusing on two companies (Dumatau trading and Botswana Tissue) involved in recycling operation. Data from the two companies is complemented by one collected from the Gaborone landfill site. Finally, this study discusses on the role played by various stakeholders in policy formulation and implementation with particular emphasis being placed on a select number of non-governmental organisations (NGO).     

Quantifying the impact of regular cutting on vegetative buffer efficacy for nitrogen-15 sequestration

This study used the stable 15N isotope to quantitatively examine the effects of cutting on vegetative buffer uptake of NO3(-)-N based on the theory that regular cutting would increase N demand and sequestration by encouraging new plant growth. During the summer of 2002, 10 buffer plots were established within a flood-irrigated pasture. In 2003, 15N-labeled KNO3 was applied to the pasture area at a rate of 5 kg N ha(-1) and 99.7 atom % 15N. One-half of the buffer plots were trimmed monthly. In the buffers, the cutting effect was not significant in the first few weeks following 15N application, with both the cut and uncut buffers sequestering 15N. Over the irrigation season, however, cut buffers sequestered 2.3 times the 15N of uncut buffers, corresponding to an increase in aboveground biomass following cutting. Cutting and removing vegetation allowed the standing biomass to take advantage of soil 15N as it was released by microbial mineralization. In contrast, the uncut buffers showed very little change in 15N sequestration or biomass, suggesting senescence and a corresponding decrease in N demand. Overall, cutting significantly improved 15N attenuation from both surface and subsurface water. However, the effect was temporally related, and only became significant 21 to 42 d after 15N application. The dominant influence on runoff water quality from irrigated pasture remains irrigation rate, as reducing the rate by 75% relative to the typical rate resulted in a 50% decrease in total runoff losses and a sevenfold decrease in 15N concentration.