Las turberas de montaña de Galicia como sumideros de carbono

Abstract

Mountain peat bogs of Galicia (NW Spain) as carbon sinksDue to its ability to accumlate atmospheric carbon and to the proportion of the Earth surface they occupy,a 3% of continental lands, peatlands are an important carbon reservoir and thus have a high potential to in-fluence the greenhouse effect and the global climate. In Galicia (NW Spain) there are some 10,000 ha ofmountain peatlands in which we estimate there are accumulated 10-16 106 t C. This represents a 4.7-7.5%of the carbon stored in forests biomass in Spain, and a 24-38% of the carbon stored in forests biomass andup to 6% of the carbon stored in the soils of Galicia. This numbers give a good insight into the importanceof peat forming ecosystems on the C cycle in the region.Within the peat deposits, C shows a rapid increase in the superficial layers (25-60 cm) and a slow increasedownwards. Nitrogen shows an opposite trend, thus C/N ratios increase with the depth/age of the peat, incontrast with the usual decrease that occurs in well aerated, mineral soils. The intensity in the change of theC/N ratio seems to be related with local factors, as for example the climatic conditions and their effect onpeatland hydrology. Peatlands located at lower altitude have higher C/N ratios than those located at higheraltitude. Carbon concentrations follow the opposite trend of peat bulk density, supporting the conclusion thatmass loss due to the decompostion of the organic matter is implied in the relative enrichment in carbon.CPMAS 13C-NMR analysis of the peat revealed the presence of aliphatic, methoxylic, hydroxylic, acetalic,aromatic and carboxilic C functional groups. Carbohydrates (hydroxylic and acetalic groups) and aliphaticsare the main components, with average proportions of 36.6% and 29.5% respectively. With increasingdepth/age the proportion of carbohydrates decreases while aliphatic and aromatic carbon increase. As a re-sult, the proportion of carbohydrate-C is negatively correlated to C concentration (r= -0.86), but aromatic-C and aliphatic-C show a positive correlation (r= 0.78 and 0.63, respectively). It seems though that theincrease in C concentration during peat decomposition occurs by the selective preservation and/or diagene-sis of consituents enriched in carbon.