Exchanges of CO2 trhrough the soil-atmosphere interphase in broadleaf autochthonous forests fron the NW of Spain (Quercus robur L. or Betula alba L.): Intra-annual variations

Abstract

It is widely accepted that increasing concentrations of ¿greenhouse gases¿ will raise the temperatures of the Earth¿s atmosphere and oceans. By acting as carbon sinks, forest ecosystems can store significant amounts of CO2. There is, therefore, a growing need to inventory and monitor carbon sequestration in forest ecosystems. Evaluation of the carbon stored in forests, both in plants and soils (global balance between CO2 fixation and CO2 emission), and the knowledge of the main factors affecting net carbon fluxes in these ecosystems are basic and essential tools to control this environmental problem. This research work encompasses the study of the seasonal variations of the CO2 emissions from soils of two different types of deciduous forests of the temperate-humid zone (Quercus robur L. or Betula alba L.) located in Galicia (northwestern Spain). With this objective, permanent forest plots (500 m2 to 1000 m2) were established and in all plots selected in situ determinations of soil C effluxes were assessed using a portable infrared gas analyser. The determinations of the CO2 exchanges through the soil-atmosphere interphase were periodically carried out during a whole year (winter, spring, summer and autumn) in order to quantify the seasonal variations of the soil emissions of this gas to the atmosphere. The significance of the seasonal variations observed for both types of forests and the implications of the results obtained in the global warming mitigation strategies, as well as the relation of these CO2 effluxes with soil temperature, are discussed.