Search Results - (Author, Cooperation:E. Chauvet)

2012-06-16

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Biodiversity ; Biomass ; *Ecosystem ; Europe ; Eutrophication ; Ilex ; Invertebrates/*metabolism ; *Plant Leaves ; Quercus ; *Rivers/microbiology ; *Water Pollution, Chemical

2014-05-09

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Arctic Regions ; *Biodiversity ; Carbon/metabolism ; *Carbon Cycle ; *Ecosystem ; Nitrogen/metabolism ; Nitrogen Cycle ; Plants/metabolism ; Tropical Climate

1573-5117

Afforestation ; eucalyptus ; stream ; litter breakdown ; fungi ; macroinvertebrates ; nutrients

Springer Online Journal Archives 1860-2000

Biology

Abstract To test the hypothesis that decomposition of leaf species in streams is influenced by afforestation with Eucalyptus globules, we compared decay rates, nutrient levels, fungal biomass and macroinvertebrate assemblages on alder and eucalyptus leaf litter in three streams (two headwaters under different forests, and a mid reach) of the Agüera catchment (northern Spain). Whatever the reach, alder always decomposed significantly faster than eucalyptus. Litter contents in nitrogen and phosphorus rose during breakdown at the mid reach, but not at the headwaters. No differences in fungal biomass were found between alder and eucalyptus leaves at the headwater reaches; however, at the mid reach, eucalyptus showed the highest values. Alder litter, a high quality substratum, was readily colonized by shredders, and decayed rapidly at all sites. Eucalyptus, a low quality species, had lower nutrient contents and was less favoured by shredders. Under high nutrient levels (particularly phosphorus), however, it was readily colonized by fungi, thus shifting from medium to high breakdown rates. The potentially negative impact of afforestation with eucalyptus on streams can thus be reduced in situations of high concentrations of dissolved nutrients.

Electronic Resource

1573-5117

seston ; particulate organic carbon ; particulate phosphorus ; algal pigments ; river

Springer Online Journal Archives 1860-2000

Biology

Abstract Water contents of suspended matter, algal pigments, particulate organic carbon and particulate phosphorus were measured in the rivers Garonne (2 sites) and Ariège (1 site) throughout an annual cycle. The general trend of the parameters was similar at the three sites. Depending on the sites, the period of algal growth (chlorophyll a + phaeopigments 〉 25 µg l−1), lasted from two to six weeks in August–September. The algal peaks reached 50 to 90 µg 1−1 of total pigments. High contents of particulate organic carbon (〉 2 mg 1−1) occurred at the end of summer (coinciding with algal growth), and during the November and May floods. In summer 50–75 % of the suspended matter was organic, in spring this was 10 times less. The high linear correlation between particulate organic carbon and pigment contents (r = 0.87; P = 0.0001) suggested an algal origin of at least part of the particulate carbon. Algal carbon was minor in the annual fluxes of particulate carbon (25 to 39% depending on the sites), but relatively high in comparison with other rivers. The mean particulate phosphorus content calculated over the year was 24 µg l−1 ; it varied from 15 µg l−1 during the high water period to 28 µg 1−1 during the low water period. Likewise the percentage of particulate phosphorus in the suspended matter varied from 0.17 to 0.40. A negative linear correlation existed between particulate phosphorus content and specific discharge (r = − 0.46; P = 0.0001). The very marked seasonal trend of the parameters and the interactions led us to differentiate two modes of the rivers' functioning: a ‘hydrologic’ phase and a ‘biological’ phase. The hydrologic phase (high water) was dominated by the processes of erosion and transfer over the whole catchment area and the flood plain, while the biological phase was characterized by a high primary production in the river bed.

Electronic Resource