Monoterpene Emission from Soils in Orange Plantations of the Valencian Citrus Belt, Spain

During the mesoscalic experiment performed in June 1997 within the framework of the BEMA-project on Biogenic Emissions in the Mediterranean Area, two test sites with orange and mandarin fields were equipped with soil enclosures to analyse type and amount of terpenoid emissions from soils. Relevant emissions were found at both sites to mainly consist of limonene, but a couple of other mono- and sesquiterpenes could also be observed. For both sites and Citrus species, the terpenoid emissions were in the range of 1500-3000 pmol m(exp -2) sec(exp -1) from soils under the trees covered with litter, and of 10-100 pmol m(exp -2) sec(exp -1) from bare soils between rows. The origin of emissions from leaf and fruit litter was experimentally confirmed by removal of the uppermost soil layers.