Book reviews

Sustainable Cities and Sustainable Development Sustainable Cities. G. Haughton & C. Hunter, 1994, Jessica Kingsley/Regional Studies Association, London

Sustainable Cities in Europe. P. Nijkamp & A. Perrels, 1994, Earthscan, London ISBN 185383, £12.95

Toward Sustainable Development Concepts, Methods and Policy. J. C. J. M. van den Bergh & J. van der Straaten, 1994, Island Press, Washington, DC, ISBN 1 55963 3492, £30.00

Just Environments: intergenerational, international and interspecies issues. David E. Cooper & Joy A. Palmer (Eds), 1995, London, Routledge, ISBN 0 415-10336-3, pp. 199, index, £11.99

First Steps: Local Agenda 21 in practice. Stella Whittaker (Ed.), 1995, London, HMSO, 251 pp. ISBN 0 11 701871 6, £29.95

Beyond the Car: essays on the auto culture. Sue Zielinski & Gordon Laird (Eds), 1995, Toronto, Steel Rail Publishing/Transportation Options, 191 pp. ISBN 0 88791 042 4, pbk, C$ 19.95, US$15.95     

Application of Biochemical and Physiological Indicators for Assessing Recovery of Fish Populations in a Disturbed Stream

Recovery dynamics in a previously disturbed stream were investigated to determine the influence of a series of remedial actions on stream recovery and to evaluate the potential application of bioindicators as an environmental management tool. A suite of bioindicators, representing five different functional response groups, were measured annually for a sentinel fish species over a 15 year period during which a variety of remedial and pollution abatement actions were implemented. Trends in biochemical, physiological, condition, growth, bioenergetic, and nutritional responses demonstrated that the health status of a sentinel fish species in the disturbed stream approached that of fish in the reference stream by the end of the study. Two major remedial actions, dechlorination and water flow management, had large effects on stream recovery resulting in an improvement in the bioenergetic, disease, nutritional, and organ condition status of the sentinel fish species. A subset of bioindicators responded rather dramatically to temporal trends affecting all sites, but some indicators showed little response to disturbance or to restoration activities. In assessing recovery of aquatic systems, application of appropriate integrative structural indices along with a variety of sensitive functional bioindicators should be used to understand the mechanistic basis of stress and recovery and to reduce the risk of false positives. Understanding the mechanistic processes involved between stressors, stress responses of biota, and the recovery dynamics of aquatic systems reduces the uncertainty involved in environmental management and regulatory decisions resulting in an increased ability to predict the consequences of restoration and remedial actions for aquatic systems.     

Comparative mobility of sulfonamides and bromide tracer in three soils

In animal agriculture, sulfonamides are one of the routinely used groups of antimicrobials for therapeutic and sub-therapeutic purposes. It is observed that, the animals when administered the antimicrobials, often do not completely metabolize them; and excrete the partially metabolized forms into the environment. Due to the continued use of antimicrobials and disposal of untreated waste, widespread occurrence of partially metabolized antimicrobials in aquatic and terrestrial environments has been reported in various scientific journals. In this research, the mobility of two sulfonamides - sulfamethazine (SMN), sulfathiazole (STZ) and a conservative bromide tracer was investigated in three soils collected from regions in the United States with large number of concentrated animal-feed operations. Results of a series of column studies indicate that the mobility of these two sulfonamides was dependent on pH, soil charge density, and contact time. At low pH and high charge density, substantial retention of sulfonamides was observed in all three soils investigated, due to the increased fraction of cationic and neutral forms of the sulfonamides. Conversely, enhanced mobility was observed at high pH, where the sulfonamides are predominantly in the anionic form. The results indicate that when both SMN and STZ are predominantly in anionic forms, their mobility approximates the mobility of a conservative bromide tracer. This observation is consistent for the mobility of both SMN and STZ individually, and also in the presence of several other antimicrobials in all three soils investigated. Higher contact time indicates lower mobility due to increased interaction with soil material.     

Principles for retrofitting coal burners for oxy-combustion

Experiments were performed in a 1.5 MW pilot-scale furnace to investigate the differences between air- and oxy-fired flame behavior from a pulverized coal oxy-research burner designed for flexible operating conditions. The flame behavior was characterized by recording video images of the flames and by measuring radiation intensity along the flame length. Various strategies relating air- and oxy-fired operation of the burner primary register were investigated where the oxy-fired burner primary mass, momentum and velocity were matched to the air-fired conditions. Matching either burner primary mass or momentum under oxy-fired conditions with air-fired conditions resulted in a flame stabilized within the quarl. Matching primary velocity with air-fired conditions resulted in a detached flame indicating a delay in flame ignition for the oxyfired conditions. A decrease in primary velocity of 13% was necessary in order to stabilize a flame within the quarl similar to the air-fired case. Additional experiments also showed a flame could be stabilized with no oxygen enrichment of the primary (～3 vol.%, dry O₂ in the primary). Experiments where oxygen was injected at the burner face indicated injection at the boundary of the primary and secondary flow paths strongly attach a flame and injection at the coal rich primary flow path increased the radiative intensity of the flame.     

Using multilevel spatial models to understand salamander site occupancy patterns after wildfire

Studies of the distribution of elusive forest wildlife have suffered from the confounding of true presence with the uncertainty of detection. Occupancy modeling, which incorporates probabilities of species detection conditional on presence, is an emerging approach for reducing observation bias. However, the current likelihood modeling framework is restrictive for handling unexplained sources of variation in the response that may occur when there are dependence structures such as smaller sampling units that are nested within larger sampling units. We used multilevel Bayesian occupancy modeling to handle dependence structures and to partition sources of variation in occupancy of sites by terrestrial salamanders (family Plethodontidae) within and surrounding an earlier wildfire in western Oregon, USA. Comparison of model fit favored a spatial N-mixture model that accounted for variation in salamander abundance over models that were based on binary detection/non-detection data. Though catch per unit effort was higher in burned areas than unburned, there was strong support that this pattern was due to a higher probability of capture for individuals in burned plots. Within the burn, the odds of capturing an individual given it was present were 2.06 times the odds outside the burn, reflecting reduced complexity of ground cover in the burn. Ther was weak support that true occupancy was lower within the burned area. While the odds of occupancy in the burn were 0.49 times the odds outside the burn among the five species, the magnitude of variation attributed to the burn was small in comparison to variation attributed to other landscape variables and to unexplained, spatially autocorrelated random variation. While ordinary occupancy models may separate the biological pattern of interest from variation in detection probability when all sources of variation are known, the addition of random effects structures for unexplained sources of variation in occupancy and detection probability may often more appropriately represent levels of uncertainty.     

Large-eddy simulation of starting buoyant jets

A series of Large Eddy Simulations (LES) are performed to investigate the penetration of starting buoyant jets. The LES code is first validated by comparing simulation results with existing experimental data for both steady and starting pure jets and lazy plumes. The centerline decay and the growth rate of the velocity and concentration fields for steady jets and plumes, as well as the simulated transient penetration rate of a starting pure jet and a starting lazy plume, are found to compare well with the experiments. After validation, the LES code is used to study the penetration of starting buoyant jets with three different Reynolds numbers from 2000 to 3000, and with a wide range of buoyancy fluxes from pure jets to lazy plumes. The penetration rate is found to increase with an increasing buoyancy flux. It is also observed that, in the initial Period of Flow Development, the two penetrative mechanisms driven by the initial buoyancy and momentum fluxes are uncoupled; therefore the total penetration rate can be resolved as the linear addition of these two effects. A fitting equation is proposed to predict the penetration rate by combining the two independent mechanisms.     

Homeostatic maintenance of ponderosa pine gas exchange in response to stand density changes.

Homeostatic maintenance of gas exchange optimizes carbon gain per water loss. Homeostasis is regulated by short-term physiological and long-term structural mechanisms, both of which may respond to changes in resource availability associated with competition. Therefore, stand density regulation via silvicultural manipulations may facilitate growth and survival through mechanisms operating at both short and long timescales. We investigated the responses of ponderosa pine (Pinus ponderosa) to stand basal area manipulations in Arizona, USA. Stand basal area was manipulated to seven replicated levels in 1962 and was maintained for four decades by decadal thinning. We measured basal area increment (BAI) to assess the response and sustainability of wood growth, carbon isotope discrimination (A) inferred from annual rings to assess the response of crown gas exchange, and ratios of leaf area to sapwood area (A(l):A(s)) to assess longer term structural acclimation. Basal area treatments increased soil water potential (r2 = 0.99) but did not affect photosynthetic capacity. BAI increased within two years of thinning, and the 40-year mean BAI was negatively correlated with stand basal area (r2 = 0.98). delta was negatively correlated with stand basal area for years 5 through 12 after thinning (r2 = 0.90). However, delta was relatively invariant with basal area for the period 13-40 years after initial thinning despite maintenance of treatment basal areas via repeated decadal thinnings. Independent gas exchange measurements verified that the ratio of photosynthesis to stomatal conductance was invariant with basal area, but absolute values of both were elevated at lower basal areas. A(l):A(s) was negatively correlated with basal area (r2 = 0.93). We hypothesize that increased A(l):A(s) is a homeostatic response to increased water availability that maximizes water-use efficiency and whole-tree carbon uptake. Elevated A(l):A(s) of trees at low basal areas was associated with greater resilience to climate, i.e., greater absolute BAI during drought; however, trees with high A(l):A(s) in low basal area stands also exhibited the greatest sensitivity to drought, i.e., greater relative decline in BAI.     

Crayfish Use of Trash Versus Natural Cover in Incised, Sand-Bed Streams

Historic land use changes and subsequent river channelization created deeply incised, unstable stream channels largely devoid of natural cover throughout the Yazoo River basin, Mississippi, USA. Large trash (e.g., televisions, toilets, car parts) dumped in streams provided shelter for some aquatic fauna. To determine whether trash served as a surrogate for natural cover, I examined crayfish use of both cover types. I sampled crayfishes by kick-seining 2 × 1-m plots in three cover classes: trash, natural cover, and no cover. I captured 415 crayfishes from 136 of the 294 plots. Most crayfishes were in natural cover (253), followed by trash (154), and no-cover (8) plots. Trash use varied by crayfish genus and size. Frequencies of all size classes of Procambarus and of the smallest Cambarus were higher in natural cover than trash. Many of the smallest individuals were found in live root mats. As Cambarus and Orconectes grew, they shifted more toward trash, and the largest Orconectes size class was significantly more abundant than expected in trash. Trash served as “artificial reefs,” providing cover for crayfishes and other fauna, but functioned differently than the remaining natural cover. The results confirmed that stream substrate did not provide adequate instream cover for crayfishes in the study area and suggested that high-quality natural cover for large crayfishes was in short supply, at least for some species. Land management that provides for abundant, ongoing input and retention of complex cover, such as trees and live roots, to stream channels should be beneficial for crayfish assemblages.