Drivers of postfire soil organic carbon accumulation in the boreal forest.

The accumulation of soil carbon (C) is regulated by a complex interplay between abiotic and biotic factors. Our study aimed to identify the main drivers of soil C accumulation in the boreal forest of eastern North America. Ecosystem C pools were measured in 72 sites of fire origin that burned 2-314 years ago over a vast region with a range of ∆ mean annual temperature of 3°C and one of ∆ 500 mm total precipitation.

Natural and estrogen-induced sexual dimorphisms in the pituitary of the newt Pleurodeles waltlii Michah and of the common frog Rana temporaria L.

In the female newt, Pleurodeles waltlii, the somatotropic cells of the adenohypophysis are characterized by large, electron-dense inclusions (1-6 micron). Inclusions were also found in adult male newts after treatment with 17-beta-estradiol (5 mg/liter of aquarium water, for 10 days to 4 months). The ultrastructural genesis of these inclusions is described for treated males and for females during sexual maturation.

[Effect of estradiol-17 beta on the somatrotroph cells of the adenohypophysis in the newt (author's transl)].

The somatotroph cells of the female newt's adenohypophysis are characterized by PAS positive, acidophils, electron dense large inclusions (4-6 micrometer). The apparition of these inclusions has been studied in females during the puberty. A correlation between the ovary stages and apparition, number and ultrastructural aspects (paracrystalline arrangement) of the inclusions is established.