Organic carbon fluxes by precipitation, throughfall and stemflow in an olive orchard in Southern Spain

Abstract

In forests and grasslands, canopy-derived carbon fluxes have been shown to be an important part of the carbon cycle, yet very few data are available for permanent agricultural crops. Concentration of total (TOC), dissolved (DOC) and particulate organic carbon (POC) was measured during an entire hydrological year in direct rainfall throughfall and stemflow in a mature olive orchard. Throughfall accounted for 68% of incoming rainfall, but TOC concentration was on average 14 times higher than in rainfall (7.63 vs. 106.12 mg/L). Stemflow on the other hand represented only a small fraction of gross precipitation, on average less than 1%, while its TOC concentration was on average 10-fold higher than in rainfall (74.13 mg/L). Dynamics of OC enrichment were mainly driven by precipitation patterns, as well as plant phenology, whereas a dramatic increase happened during flowering. Stemflow and throughfall were proven to be important sources of organic carbon supplying 13.5 g C/m²/year beneath the canopy of each tree, while 2.41 g C/m²/year reached the soil through gross precipitation. This large fraction of carbon is a mean of recirculating important carbon compounds that may help mobilize soil nutrients and maintain water holding capacity in the circumscribed area below olive canopies.

Keywords:

• Olea europaea L
• throughfall
• stemflow
• organic carbon

Acknowledgements

The support of Projects P08-AGR-03643 (Andalusian Government) and FEDER funds is gratefully acknowledged. Tom Vanwalleghem gratefully acknowledges funding by the Ramón y Cajal Fellowship Programme by the Spanish Ministry of Economy and Competitiveness.