Altered ecohydrologic response drives native shrub loss under conditions of elevated nitrogen deposition

Many regions of southern California's coastal sage scrub (CSS) are rapidly declining as exotic annual plants replace native shrubs. During this conversion, the subsurface hydrology of the semiarid hillslopes that support CSS may be altered. This could chronically suppress the ability of native shrubland to revegetate the landscape since ecosystem processes of nutrient availability and of seedling establishment rely on spatial patterns of available soil water. In this work, soil water and nutrient N regimes were compared over a 2-yr period between a southern California site where CSS has declined (approximately 5% shrub cover) with high additions of anthropogenic N, and one where CSS remains dominant (over 50% shrub cover) with predominantly background atmospheric additions of N. These two sites have similar climate, bedrock lithology, soils, and topography, and had the same vegetation type (Riversidean CSS) 30 years ago. We found that the depth and rate of rainwater percolation into wildland hillslope soils in response to early-season storm events has been greatly reduced after loss of CSS shrubs and vegetation type conversion to invasive grassland. With decreased rainwater redistribution to soil depths of 100 to 150 cm, the predominant zone of soil water has become the upper 25 cm. This shift exacerbates vegetation type conversion by (i) concentrating smog-produced nitrogenous (N) chemicals in the uppermost soil, where they become readily available, along with high soil water, to shallow-rooted exotic grasses early in the growing season and (ii) depriving adult and juvenile shrubs of deeper regolith water.     

Voluntary recycling despite disincentives

This paper assesses the determinants of take-up of a voluntary waste separation scheme, in a scenario where residents sorted, stored and paid for collection of recycling waste even though mixed waste was collected at the kerbside more conveniently, free of charge and without any quantity limits. Uptake of the scheme was positive, persistent and diverse across localities, offering an opportunity to assess the factors determining voluntary participation in the presence of disincentives. We employ a unique panel data-set (n = 4,644) from Malta, including data on recyclable waste kilogrammes collected over the first 86 weeks of the scheme's operation. Drawing on insights from environmental economics and psychology, a model is empirically estimated. Results indicate that uptake is suppressed by the initial constraints households may face and stimulated by collection frequency. Political vote is an important determinant of participation and this interacts with scheme promotion to create diverse uptake rates.     

A plankton study in the eastern Mediterranean Sea

A synoptic study of the phytoplankton and zooplankton distribution in the eastern Mediterranean Sea was carried out in the summer of 1965 during a cruise of R.V. “Pillsbury”. The phytoplankton maximum was normally found at 100 m, below the 1% level of surface light, with a frequent smaller peak at 40 m. In shallower waters, the main peak was at 80 m. The greatest number of phytophagous crustaceans was recorded at, or close to, the phytoplankton maximum. Depth relationships of phytoplankton and functionally phytoplanktonic species are discussed. Zooplankton was collected from depths down to 4,400 m, the deepest cast being in the Rhodes Deep. The most common species and genera of some selected groups of zooplankton were identified and their distribution considered in the light of some previous cruises in part of the area. The presence of Acantharia containing zooxanthellae with chlorophyll at, and below, 4,000 m was recorded for the first time. Potentially photosynthetic Ceratium vultur and C. carriense (Dinophyceae), both species in active division, were also found at these depths, as well as Halosphaera viridis (Prasinophyceae), which was recorded down to a depth of 1,000 m.     

四种藻类植物对镍的耐受性及其中毒的变化

四种纯种培养的藻类植物对镍离子的耐受性不同。衣藻属(Chlamydomonas sp.)可耐受10ppm的镍;栅列藻属(Scenedesmus sp.)5ppm;颤藻属(Oscillatoria sp.)1ppm;聚球藻属(Synechococcus sp.)0.02ppm。受试的两种绿藻比蓝纯菌(蓝藻类,Cyanobacteria)对镍离子毒性的抗性大得多。本文还报道了影响这些藻类对镍的敏感性和抗性的某些环境因素,并阐明了一些抗性的机制。     

Zoning and the Tasmanian commercial rock lobster fishery

In this paper, the island of Tasmania is considered as a government jurisdiction. Management at this scale can conflict with sustainability in local environments. The case used to make this argument is the Tasmanian commercial rock lobster fishery. Within this fishery, Tasmania-wide management paradoxically intensifies differences at the same time as it effaces them. These differences contrast with Tasmania-wide management claims regarding sustainability. Actor–network theory is used to help approach these tensions. Zoning the fishery is put forward as a way to take into account differences to produce sustainable local outcomes.     

Hazardous Pollutants in Class II Landfills

Class II landfills accept nontoxic municipal trash. Their gaseous emissions were originally assumed to be relatively free of hazardous substances. However, one Class II site in Southern California was found to be emitting enough vinyl chloride to exceed the California Air Quality Standard of 10 ppb for a 24-hour average in surrounding neighborhood. This paper presents a summary of the results of the analysis of landfill gas from over 20 additional Class II landfills. Ambient air surveys were conducted around five of the landfills. About 90 percent of the landfills contained measurable amounts of vinyl chloride and/or benzene. The concentrations exceeded 1 ppm in about half of the sites studied. Vinyl chloride is produced in situ by the action of bacteria on chlorinated solvents, and can be found in landfills that have been closed for over 30 years. The relative amounts of methane and vinyl chloride vary so much within a single landfill that methane measurements cannot be used as a surrogate for vinyl chloride     

Complex habitat boosts scallop recruitment in a fully protected marine reserve

This study investigated the effects of a fully protected marine reserve on commercially valuable scallops and benthic habitats in Lamlash Bay, Isle of Arran, United Kingdom. Dive surveys found the abundance of juvenile scallops to be greater within the marine reserve than outside. A novel multivariate approach, based upon neural networks and generalised linear models, revealed the greater abundance of juveniles to be related to the greater presence of macroalgae and maerl within the reserve boundaries. This complex habitat appeared to have positively encouraged spat settlement. In contrast, the density of adult scallops did not differ between the two treatments, possibly due to the short duration of protection. However, the age, size and biomass of adult scallops were significantly greater within the reserve. Overall, this study suggests that the newly created marine reserve is already providing benefits which are flowing back to species targeted by fisheries, emphasising the importance of marine reserves in ecosystem-based management of fisheries.     

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