The effect of grazing on biodiversity in coastal dune heathlands

The effect of sheep grazing on species richness, higher order diversity measures, inequality, species composition, functional diversity and allometric relationships at a coastal dune heathland site was investigated. After a prescribed fire in 2002, the site was divided into two parts, where one of the parts was unmanaged and the other part was fenced and grazed by sheep. Sheep grazing had a positive effect on species richness as well as a significant positive effect on the functional diversity at the coastal dune heathland site. Generally, the cover of dwarf shrubs was negatively affected by grazing, whereas the cover of sedges and grasses was positively affected by grazing. There is a need for comparative investigations of the effect of different management methods not only on floristic biodiversity, but on all relevant kinds of biodiversity as well as on soil structure, soil chemistry and habitat micro- and macrostructure. Consequently, we advocate the initiation of an international systematic investigation of the effect of different management methods.     

Major osmolyte changes during oocyte hydration of a clupeocephalan marine benthophil: Atlantic herring (<Emphasis Type="Italic">Clupea harengus</Emphasis>)

The major inorganic and organic osmolytes responsible for hydrating the oocytes during pre-ovulatory meiotic maturation in autumn- and spring-spawning stocks of Atlantic herring are examined. Despite the ovulated eggs of spring-spawning herring being 1.6- to 2-fold larger than the autumn-spawning stock, the GSI (27 ± 3%) and degree of oocyte hydration (70–72% water) were similar. Normalising the data with respect to dry mass revealed that the physiological mechanisms underlying the maturational influx of water were the same for both classes of egg. Cl⁻, K⁺ and P_i together with a small pool of free amino acids (FAA) represented the driving forces for oocyte hydration. K⁺ (autumn and spring) and P_i (spring) maintained their concentrations in the ovulated eggs, while all other ions, including Cl⁻, Na⁺, NH₄ ⁺ and Mg²⁺ were significantly diluted. In contrast the FAA concentration increased during the hydration process. Amongst the inorganic ions, Cl⁻ showed the greatest increase in the ovulated eggs. The FAA content doubled from 1.5 to 3.3% of dry mass during oocyte hydration and accounted for 29% of the calculated ovoplasmic osmolality in the ovulated eggs from both autumn- and spring-spawners. This significant osmotic effect of the small pool of FAA was due to the low water content of the benthic eggs. The differential movement of the inorganic and organic osmolytes that underly oocyte hydration in Atlantic herring are discussed in relation to current models of transmembrane ion flux.     

Windblown Dust Contributes to High PM25 Concentrations

ABSTRACT

The revised National Ambient Air Quality Standards for PM include fine particulate standards based upon mass measurements of PM₂₅. It is possible in arid and semi-arid regions to observe significant coarse mode intrusion in the PM_2.5 measurement. In this work, continuous PM₁₀, PM_2.5, and PM_1.0 were measured during several windblown dust events in Spokane, WA. PM_{2 5} constituted ~30% of the PM₁₀ during the dust event days, compared with ~48% on the non-dusty days preceding the dust events. Both PM₁₀ and PM_2.5 were enhanced during the dust events. However, PM_1.0 was not enhanced during dust storms that originated within the state of Washington. During a dust storm that originated in Asia and impacted Spokane, PM_1.0 was also enhanced, although the Asian dust reached Washington during a period of stagnation and poor dispersion, so that local sources were also contributing to high particulate levels. The “intermodal” region of PM, defined as particles ranging in aerodynamic size from 1.0 to 2.5 um, was found to represent a significant fraction of PM₂₅ (~51%) during windblown dust events, compared with 28% during the non-dusty days before the dust events.