Bilan de l'azote ; Cycle de l'azote ; Ecologie quantitative ; Ecosystème ; Géographie physique ; Littoral ; Wadden
Salt marshes reduces oxidised nitrogenous compounds to ammonium and particulate nitrogen and export these reduced forms to coastal waters. The internal demands exceed the net imputs of nitrogen by rain, groundwater flow and fixation, suggesting very
active uptake conversion, release and recycling of nitrogen within a marsh ecosystem. Nitrogen losses are mainly through tidal exchanges and denitrification, and these two outputs balance the gains. The chemical exchanges among uplands, marshes
Past and current trends in environmental change are examined in terms of their impact on biogeochemical cycles of carbon, nitrogen and sulphur at scales from the local to the global. The major issues concern fossil fuel consumption which influences
all three cycles, and agriculture which affects the carbon and nitrogencycles in particular. Anthropogenic pertubations of these cycles has given rise to some of the most important environmental issues of the 1990s, notably global climatic change
Asian part of USSR ; Biogeochemical cycle ; Carbon cycle ; Ecosystem ; Grassland ; Kazakhstan ; Nitrogencycle ; Quantitative ecology ; Siberia
Cycle biogéochimique ; Cycle de l'azote ; Cycle du carbone ; Ecologie quantitative ; Ecosystème ; Formation herbacée ; Kazahskaja SSR ; Kazahstan ; Sibir' ; URSS d'Asie
Caractéristiques de la dynamique du cycle biologique du carbone dans les écosystèmes herbacés en régime stationnel, périodique, transitoire et mixte. Les AA. étudient les causes des variations des régimes, la relation entre les processus saisonniers
de production et de destruction et entre les cycles du carbone, de l'azote et du phosphore. - (VVA)
Soil nitrogen transformations associated with small patterned-ground features along a North American Arctic transect
Alaska ; Arctic Region ; Biogeochemical cycle ; Canada ; Cold area ; Geochemistry ; Latitude ; Nitrogen ; Patterned ground ; Spatial analysis ; Tundra
Alaska ; Analyse spatiale ; Arctique ; Azote ; Canada ; Cycle biogéochimique ; Géochimie ; Latitude ; Sol figuré ; Toundra ; Zone froide
Small patterned-ground features (PGFs) in the Arctic have unique soil properties that vary with latitude and may greatly affect tundra biogeochemistry. Because nitrogen availability can strongly limit arctic vegetation growth, the AA. examined how
soil nitrogen transformations differ between PGFs and the surrounding inter-PGF tundra along an arctic latitudinal gradient. The 8 study sites are located from the Alaskan Low Arctic to the Canadian High Arctic. The soils were incubated for 21 days at 9
°c and 15°c and analysed for changes in total inorganic nitrogen, nitrate and extractable organic nitrogen (EON). The results show that spatial heterogeneity at several scales can influence soil nitrogen dynamics, and is therefore an important
Cinq années d'effort d'un groupe US-IBP Desert Biome se sont traduites par une compréhension globale du cycle de l'azote dans les écosystèmes à arbustes dominants des déserts salés dans la partie Nord-Est du Désert du Great Basin des Etats-Unis
Adaptation ; Biogeochemical cycle ; Carbon cycle ; China ; Climatic change ; Eastern China ; Ecosystem ; Forest ; Nitrogen ; Nitrogencycle ; Water cycle ; Water use
Adaptation ; Azote ; Changement climatique ; Chine ; Chine de l'Est ; Cycle biogéochimique ; Cycle de l'azote ; Cycle de l'eau ; Cycle du carbone ; Date 2008 ; Ecosystème ; Forêt ; Utilisation de l'eau
. studied the geographical distribution patterns of vegetable water use efficiency (WUE) and nitrogen use efficiency (NUE), and analyzed their relationship with environmental factors. The results suggest that global change would impact the resource use
efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade
-off mechanism and give a dramatic disturbance to the ecosystem biogeochemical cycle.
Nitrogen economy of reed vegetation in the Zuidelijk Flevoland polder. I. Distribution of nitrogen among shoots and rhizomes during the growing season and loss of nïtrogen due to fire management