Dynamics of Tree and Shrub Vegetation in the Eastern Sayan Mountain Tundra

Russian Journal of Ecology - Climate change entails shifts in the ranges of woody plants along both latitudinal and altitudinal gradients in the boreal forest biome. In this study,...     

Cross-sectional mortality studies and air pollution risk assessment

The use of coefficients, derived from cross-sectional mortality studies, for air pollution risk assessment is quite controversial. In this study, the major limitations of cross-sectional studies are reviewed. The consistency of results from the major recent cross-sectional studies is examined, and the sensitivity of results to model specification is analyzed. Finally, the implications for risk assessment of our inquiries are discussed.     

Counter-disaster training in developing countries

This paper discusses both the need for training within a wider context of community disaster preparedness and the major alternatives in methods of training. Emphasis is placed on the importance of compatibility between the resources within a given country and appropriate training programmes.     

Second derivative spectroscopy for the determination of volatilized ammonia from urea-amended soil

A second derivative spectrometer custom fitted with a 1 m stainless steel White cell and maintained at 105°C is used to make real-time measurements of volatilized NH₃ from urea-amended soil. Comparison of the technique to impinger data shows a 5–16% discrepancy between the two techniques; however, other experiments presented suggests that this is not real. Sulfur dioxide and nitrous oxide interferences are discussed, though they were not found to be present in this study. Instrument response time is shown to be fast if 67% of the total response is achieved in less than 5 min. Fast response is achieved for ammonia if wall-adsorption effects are minimal and if ammonia mass flow is maintained at 0.2 μg min^-1.     

Spatial and temporal patterns of predation on seeds of the surfgrass Phyllospadix torreyi

Spatial and temporal patterns of predation on seeds of the seagrass Phyllospadix torreyi S. Watson were quantified at four sites near Santa Barbara, California, USA. Over a period of four flowering seasons during 1995 to 1998, monthly patterns of seed fall and intensity of seed predation were similar among sites, but were temporally quite variable. Abundance of dispersed seeds varied greatly both among seasons and years. Within any one year, seeds were present in the environment every month, but they peaked in abundance during the fall months following the annual flowering period. Seeds were more abundant during the earlier years of the study. The intensity of predation steadily increased throughout the study period, from a low of ≤10% seeds consumed during 1995 to ∼50% consumption by 1997, and it was not correlated with abundance of seeds in the environment. Pre-dispersal seed loss also was estimated in two flowering seasons by counting the numbers of seeds consumed prior to release from the plant, and was relatively low (<15%). No differences were detected among the four study sites in patterns of pre-dispersal loss. Field surveys were done at two sites to identify potential seed predators. Three of the most abundant species identified in these surveys were tested in the laboratory to determine size-specific patterns of feeding activity and to assess which early life stages of P. torreyi (fruits within spadices, dehisced fruits, seedlings) were most vulnerable to predation. All three of the early life stages were consumed. The crabs Pugettiaproducta (Randall) and Pachygrapsus crassipes Randall were much more voracious predators than the isopod Idotea resecata Stimpson. Received: 8 June 1999 / Accepted: 2 February 2000