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Environ Pollut ; 148(1): 191-200, 2007 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-17182158


On an upland moor dominated by pioneer Calluna vulgaris and with an understorey of mosses and lichens, experimental plots were treated with factorial combinations of nitrogen (N) at +0 and +20kg Nha(-1)yr(-1), and phosphorus (P) at +0 and +5kg Pha(-1)yr(-1). Over the 4-year duration of the experiment, the cover of the Calluna canopy increased in density over time as part of normal phenological development. Moss cover increased initially in response to N addition but then remained static; increases in cover in response to P addition became stronger over time, eventually causing reductions in the cover of the dominant Calluna canopy. Lichen cover virtually disappeared within 4 years in plots receiving +20kg Nha(-1)yr(-1) and also in separate plots receiving +10kg Nha(-1)yr(-1), but this effect was reversed by the addition of P.

Contaminantes Atmosféricos , Calluna/crecimiento & desarrollo , Ecosistema , Fertilizantes , Nitrógeno , Fósforo , Briófitas/crecimiento & desarrollo , Ecología/métodos , Monitoreo del Ambiente/métodos , Geografía , Líquenes/crecimiento & desarrollo , Tiempo , Reino Unido
Environ Pollut ; 138(3): 473-84, 2005 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-15950340


This study was designed to investigate the effect of long-term (11 years) ammonium nitrate additions on standing mass, nutrient content (% and kg ha(-1)), and the proportion of the added N retained within the different compartments of the system. The results showed that more than 90% of all N in the system was found in the soil, particularly in the organic (Oh) horizon. Added N increased the standing mass of vegetation and litter and the N content (kg N ha(-1)) of almost all measured plant, litter and soil compartments. Green tissue P and K content (kg ha(-1)) were increased, and N:P ratios were increased to levels indicative of P limitation. At the lowest treatment, most of the additional N was found in plant/litter compartments, but at higher treatments, there were steep increases in the amount of additional N in the underlying organic and mineral (Eag) horizons. The budget revealed that the proportion of added N found in the system as a whole increased from 60%, 80% and up to 90% in response to the 40, 80 and 120 kg N ha(-1) year(-1) treatments, respectively.

Contaminantes Atmosféricos/toxicidad , Atmósfera/química , Nitrógeno/toxicidad , Contaminantes Atmosféricos/análisis , Contaminantes Atmosféricos/metabolismo , Biomasa , Ecosistema , Monitoreo del Ambiente/métodos , Nitrógeno/análisis , Nitrógeno/metabolismo , Fósforo/análisis , Plantas/efectos de los fármacos , Potasio/análisis , Contaminantes del Suelo/análisis , Contaminantes del Suelo/metabolismo , Contaminantes del Suelo/toxicidad
Environ Pollut ; 135(3): 469-80, 2005 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-15749544


This study determined the effects of increased N deposition on rates of N and P transformations in an upland moor. The litter layer and the surface of the organic Oh horizon were taken from plots that had received long-term additions of ammonium nitrate at rates of 40, 80 and 120 kg N ha(-1) yr(-1). Net mineralisation processes were measured in both field and laboratory incubations. Soil phosphomonoesterase (PME) activity and rates of N(2)O release were measured in laboratory incubations and root-surface PME activity measured in laboratory microcosms using Calluna vulgaris bioassay seedlings. Net mineralisation rates were relatively slow, with net ammonification consistently stimulated by N addition. Net nitrification was marginally stimulated by N addition in the laboratory incubation. N additions also increased soil and root-surface (PME) activity and rates of N(2)O release. Linear correlations were found between litter C:N ratio and all the above processes except net nitrification in field incubations. When compared with data from a survey of European forest sites, values of litter C:N ratio were greater than a threshold below which substantial, N input-related increases in net nitrification rates occurred. The maintenance of high C:N ratios with negligible rates of net nitrification was associated with the common presence of ericaceous litter and a mor humus layer in both this moorland as well as the forest sites.

Contaminantes Atmosféricos/análisis , Atmósfera , Calluna/química , Nitrógeno/química , Fósforo/química , Clima , Ecosistema , Monitoreo del Ambiente/métodos , Minerales , Nitrógeno/análisis , Óxido Nitroso/química , Monoéster Fosfórico Hidrolasas/química , Suelo , Contaminantes del Suelo/análisis , Gales