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Environ Sci Process Impacts ; 16(9): 2156-64, 2014 Sep 20.
Artículo en Inglés | MEDLINE | ID: mdl-25008033


Plant production is a key process in semi-natural ecosystems, affecting resource provision, carbon storage, and habitat suitability for species of conservation concern. There is debate over whether nitrogen (N) or phosphorus (P) limits productivity more widely, and whether the pattern of limitation has been affected by widespread atmospheric N pollution. In a national-scale survey, floristic composition was used to derive mean Ellenberg N score (EN) for use as an independent metric of productivity. Much of the variation in EN within extensively-managed habitats could be explained by bulk-soil properties such as total C and moisture contents, reflecting the axis from wet, organic, infertile soils to drier, mineral, fertile soils. However, this main axis of variation was also explained well by bicarbonate-extractable P stock, and P stock was included in the best 88 of 255 possible models for all habitats, or the best 55 of 255 models for extensively-managed habitats. The stock of mineralisable N was much less well able to explain variation in the productivity metric, particularly in extensively-managed habitats. This suggests that P availability is a more widespread constraint to the productivity of semi-natural ecosystems in the UK than is N availability.

Fósforo/análisis , Desarrollo de la Planta , Carbono/análisis , Ecosistema , Nitrógeno/análisis , Suelo/química , Reino Unido
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