Element redistribution along hydraulic and redox gradients of low-centered polygons, Lena Delta, northern Siberia

Wetland soils affected by permafrost are extensive in subarctic and arctic tundra. However, this fact does not imply these soils have been sufficiently investigated. In particular, studies of element translocation processes are scarce. This study was conducted (i) to determine the relationship between water and redox regimes in wetland soils in the Siberian tundra, and (ii) to investigate their influence on the distribution of redox sensitive and associate elements (Mn, Fe, P). Major geomorphic units were chosen (microhigh, polygon rim and slope; microlow, polygon center) from two low-centered polygons in the Lena Delta. Within polygons, redox potential, permafrost, and water level were measured during summer in 1999 and 2000 and (related) compared with element distribution. Manganese, Fe, and P accumulations were preferentially observed in aerobic microhighs. Anaerobic conditions in the microlows lead to a mobilization of Mn, Fe, and P. The elements migrate via water and are immobilized at the microhigh, which acts as an oxidative barrier. The element pattern, indicating an upward flux via water along redox gradients, is explained by higher evapotranspiration from soils and vegetation of the microhighs (Typic Aquiturbel) compared with soils and vegetation of the microlows (Typic Historthel). However, in further research this upward transport should be validated using labeled elements

Evaluation of phosphorus in forest soils: Comparison of phosphorus uptake, extraction method and soil properties

Phosphorus in soils from plantation of red pine ( Pinus resinosa Ait.) was determined using six extractants: 0.002 N H 2 SO 4 (pH 3.0); 0.025 N HCl+ +0.03 N NH 4 F; 0.5 N NaHCO 3 (pH 8.5); N NH 4 OAc (pH 4.8); anion exchange resin (Dower −2, Cl-form); H 2 O. Correlations of extractable P with Al- and Al-+Fe-P indicated that these fractions are the dominant forms of inorganic P in most of the soils.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43473/1/11104_2005_Article_BF02149737.pd

A behavioural treatment of blepharospasm: two case reports

Blepharospasm is a distressing condition, characterized by a repetitive and spasmodic closing of the eyes, and/or an inability to open the eyes after blinking. The aetiology of the disorder remains obscure. The available literature tends towards viewing the condition as arising from or associated with neuropathological processes. Two cases of blepharospasm are presented here. Both were managed along purely behavioural lines, using massed practice and relaxation techniques. The results obtained strongly suggest a learning model, rather than a neuropathological model may best explain the condition. Possible mechanisms for the development and maintenance of blepharospasm are discussed.link_to_subscribed_fulltex