Entwicklung von Fichtenverjüngung im Lehrwald Sedrun der ETH Zürich (nördliche Zwischenalpen) | Development of Norway-Spruce Regeneration in the Training Forest of ETH Zurich in Sedrun, Canton of Grisons, Switzerland (Northern Intermediate Alps)
The development of planted Norway-spruce trees as well as the germination and self-seeding of natural regeneration were investigated on various forest locations on the north and south slopes between 1470 and 1800 m above sea level in the training forest of ETH Zurich in Sedrun, canton of Grisons, Switzerland.
Early seedling establishment of Picea abies in small forest gaps in the Swiss Alps
Early seedling establishment of Picea abies (L.) Karst. in small forest gaps was studied in drier, subalpine P. abies ecosystems in the Swiss Alps. Study sites were on steep south and north slopes. Average gap size was 15 m x 20 m on the south slope and 15 m x 70 m on the north slope. Sowing trials established on different microsites were observed for 2 or 3 years. Direct sunlight was assessed with hemispherical photography. Emergence was better on the north slope than on the south slope. On the south slope, emergence was higher on the mineral soil than on the organic layer and was negatively associated with direct sunlight, especially during the noon period. On both slopes, drought due to rainfall interception at the gap edge negatively affected emergence. The limiting factor for survival and growth on the south slope was drought (on the organic layer), whereas on the north slope lack of direct radiation and pathogenic fungi developing in the snowpack were limiting. The early regeneration niche on the so...
Human exposure to methylmercury from crayfish (Procambarus clarkii) in China
Methylmercury (MeHg) accumulation in aquatic food raises global concerns about human exposure to MeHg. Crayfish is the world’s third largest farmed crustacean species and a favorite aquatic food in many countries. However, human health hazard due to MeHg exposure via crayfish consumption is unclear, partly because appropriate survey data are lacking. We report on mercury concentrations and speciation in edible tail muscle of crayfish collected from restaurants in 23 Chinese cities. On average, MeHg constituted 99.1 % of mercury in tail muscle, and MeHg concentrations were comparable with those reported for fish in China. Variation in MeHg concentrations was not attributable to broad geographic region (i.e., provinces) or tail length. For different populations, potential health risk (characterized by hazard quotient or HQ) of MeHg exposure through crayfish consumption depended largely on crayfish consumption rates. In particular, a health hazard (HQ > 1) was found for high-rate consumers (i.e., 95 %ile or higher) in some cities in the middle and lower reaches of the Yangtze River (MLYR), during the peak consumption season. Our results suggest that more attention should be paid to dietary MeHg intake via crayfish consumption in China, particularly for communities with high consumption in MLYR.