Induced effects of hedgerow networks on soil organic carbon storage within an agricultural landscape

Hedgerow network landscapes or "bocages" are present throughout a large part of Western Europe [Baudry, J., Bunce, R.G.H. et al., 2000. Hedgerows: an international perspective on their origin, function and management. Journal of Environmental Management 60 (1), 7-22.]. These manmade landscapes are typically comprised of fields separated by boundaries, often marked by perennial vegetation (hedges or shelterbelts), yet little is known about the effect of these field margins on soil organic carbon (SOC) stocks and their dynamics, which offer large carbon sequestration potential [Walter, C., M rot, P., Layer, B., Dutin, G., 2003. The effect of hedgerows on soil organic carbon storage in hillslopes. Soil Use and Management 19, 20 1 207.; Falloon. P., Powlson, D., Smith, P., 2004. Managing field margins for biodiversity and carbon sequestration: a Great Britain case study. Soil Use and Management 20, 240-247.]. In hedged landscapes, hedges induce a modification to the soil A-horizon geometry at the slope scale, as attributed to an anti-erosive effect, along,with a local modification of the associated SOC stocks. Most studies undertaken within this context have been performed in two dimensions and under favourable conditions for soil accumulation with the hedges lying perpendicular to the steepest slope direction. Consequently, an extrapolation of these findings to the entire landscape can lead to overestimating SOC stocks at the landscape scale. The aims of this paper were to: quantify, SOC stocks, describe their spatial variability in three dimensions, and identify the main determinants behind this variability within an agricultural hedgerow network landscape. To achieve these aims, we conducted a detailed field survey that took into account all three dimensions of the soil coverand anthropogenic structures. We then analysed the spatial distribution of SOC contents and stocks with respect to pedological and landscape parameters. Results show that SOC stocks may be locally significant in the vicinity of hedges with a median stock value of 16.6 kg cm(-2), in comparison with stock at the landscape scale (13.3 kg C m(-2)). This study has highlighted the need to incorporate the three dimensions of soil cover at the landscape scale in order to characterise SOC storage. This step will prevent the generalisation of local stocks at a landscape scale given the high variability of SOC stocks (1st quartile = 10.5 kg C m(-2); 3rd quartile- 18.5 kg C m(-2)) induced by hedge structures. (C) 2007 Elsevier B.V. All rights reserved.