We measured the terpene concentration in pentane and water extracts from soilhorizons (litter, organic, top and low mineral) and from roots growing in top and low mineral horizons on a distance gradient from Pinushalepensis L. trees growing alone on a grassland. Terpene concentrations in pentane were higher than in water extracts, although β-caryophyllene showed relatively high solubility in water. The litter and roots were important sources of terpenes in soil. Alpha-pinene dominated in roots growing in both “top” (A1) and “low” (B) mineral horizons (123 ± 36 μg g−1 or 14 ± 5 mg m−2) and roots in low mineral horizon (270 ± 91 μg g−1 or 7 ± 2 mg m−2). Beta-caryophyllene dominated in litter (1469 ± 331 μg g−1 or 2004 ± 481 mg m−2). Terpene concentration in soil decreased with increasing distance to the trunk. This is likely to be related to changes in litter and roots type on the distance gradient from pine to grass and herbs. The relative contributions of all compounds, except α-pinene, were similar in the mineral soils and litter. This suggests that litter of P. halepensis is probably the main source of major terpene compounds. However, long-term emissions of α-pinene from P. halepensis roots might also contribute to α-pinene concentrations in rhizosphere soils.

This research was supported by a Fundació Abertis 2007 grant and Spanish MEC grants CGL2004-01402/BOS and CGL2006-04025/BOS. We also gratefully acknowledge partial funding by the ISONET European Commission contract MC-RTN-CT-2003-504720, the European Commission contract ALARM 506675, the European project NITROEUROPE GOCE017841 and a Fundación BBVA 2004 and a Catalan Government SGR2005-003/12 grants.

11 páginas, 4 figuras, 5 tablas.

Peer reviewed