Invasion through quantitative effects: intense shade drives native decline and invasive success.

The effects of invasive nonnative species on community composition are well documented. However, few studies have determined the mechanisms by which invaders drive these changes. The literature indicates that many nonnative plant species alter light availability differently than natives in a given community, suggesting that shading may be such a mechanism. We compared light quantity (photosynthetically active radiation, PAR) and quality (red: far-red ratio, R:Fr) in riparian reaches heavily invaded by a nonnative tree (Acer platanoides) to that in an uninvaded forest and experimentally tested the effects of our measured differences in PAR and R:Fr on the survival, growth, and biomass allocation of seedlings of the dominant native species and Acer platanoides. Light conditions representative of the understory of Acer platanoides-invaded forest decreased survival of the native maple Acer glabrum by 28%; Amelanchier alnifolia by 32%; Betula occidentalis by 55%; Elymus glaucus by 46%; and Sorbus aucuparia by 52%, relative to seedlings growing in PAR similar to that of native understories. In contrast, Acer platanoides and the native shrub Symphoricarpos albus were not affected by reductions in PAR. Acer platanoides seedlings and saplings are uniquely adapted to shade relative to native species. Acer platanoides was the only species tested that decreased allocation to roots relative to shoots in the invaded forest vs. the native forest light conditions. Therefore it was the only species to demonstrate an adaptive response to the particular light environment associated with Acer platanoides invasion as predicted by optimal partitioning theory. The profound change in light quantity associated with Acer platanoides canopies appears to act as an important driver of native suppression and conspecific success in invaded riparian communities. Further research is necessary to determine whether the effect of nonnative plant-driven changes on light quantity and quality is a widespread mechanism negatively affecting resident species and facilitating invasion by nonnatives.     

A new towed underwater camera system for wide-range benthic surveys

Following a short review of previous underwater camera systems, a new combined underwater camera system, consisting of a remote controlled TV- and photocamera mounted on a ship-towed steel-tubing sled, is described. The method of using this apparatus for wide-range surveys of the marine littoral benthos, and the techniques used to evaluate and quantify the observations are presented. On the basis of first results obtained in the North Adriatic Sea, the efficiency of the new system is compared with various other instruments and techniques. Advantages and disadvantages, possible improvements, and future prospects are discussed.     

Detection and Classification of Motor Vehicle Noise in a Forested Landscape

Noise emanating from human activity has become a common addition to natural soundscapes and has the potential to harm wildlife and erode human enjoyment of nature. In particular, motor vehicles traveling along roads and trails produce high levels of both chronic and intermittent noise, eliciting varied responses from a wide range of animal species. Anthropogenic noise is especially conspicuous in natural areas where ambient background sound levels are low. In this article, we present an acoustic method to detect and analyze motor vehicle noise. Our approach uses inexpensive consumer products to record sound, sound analysis software to automatically detect sound events within continuous recordings and measure their acoustic properties, and statistical classification methods to categorize sound events. We describe an application of this approach to detect motor vehicle noise on paved, gravel, and natural-surface roads, and off-road vehicle trails in 36 sites distributed throughout a national forest in the Sierra Nevada, CA, USA. These low-cost, unobtrusive methods can be used by scientists and managers to detect anthropogenic noise events for many potential applications, including ecological research, transportation and recreation planning, and natural resource management.     

Achieving Nutrient Water Quality Goals: Bringing Market‐Like Principles to Water Quality Management*1

Abstract: Market‐like trading programs for water quality management begin with enforceable limits on the amount of the pollutant allowed in a watershed. Properly designed market‐like trading programs then create incentives for dischargers to reduce nutrient control costs over time by making pollution prevention innovations. However, the structure of the Clean Water Act can be a barrier to establishing market‐like trading programs. First, we describe the general features and advantages of market‐like trading programs. Then we offer practical suggestions for bringing market‐like design concepts to nutrient trading programs within the existing legal and regulatory setting.     

Conservation‐Induced Wastewater Flow Reductions Improve Nitrogen Removal: Evidence from New York City1

Abstract: Water resources are under increasing pressure to meet potable supply needs while sustaining aquatic ecosystems and fisheries. Growing populations and enforcement of the Total Maximum Daily Load provisions of the Clean Water Act present public water and wastewater utilities with costly options to meet potable water demands and reduce pollutant discharges into receiving waters. This paper documents that New York City’s comprehensive water conservation program – designed to extend the city’s safe yield of potable water—has also resulted in reduced nitrogen discharges from the city’s water pollution control plants during a period of population increases. This paper demonstrates and quantifies the effects that wastewater inflow volume reductions have on increased nitrogen removal, controlling for plant process changes. Conservation programs have saved the city billions of dollars in delayed or avoided capital improvements to both water and wastewater treatment plants, and have enabled the city to meet interim effluent discharge standards.     

A self-contained underwater time-lapse camera for in situ long-term observations

A self-contained underwater time-lapse camera system, based on a standard 16 mm movie camera, is introduced. The camera is capable of autonomous underwater operation up to 1 week — limited by the energy supply — and uses standard 30 m rolls of film with 4000 exposures. The system is equipped with two adjustable computer flashes, powered by a simple 12 V car battery. The camera is triggered electromagnetically, controlled by an electronic timer. The unit, with a total mass of about 25 kg, can be operated and positioned by a single diver even from very small boats. A maximum working depth of 50 m can be reached. First results and experiences with the time-lapse camera, based on almost 1000 h of operation in the North Adriatic Sea, are described and discussed.