Carbon sequestration in hedgerow biomass and soil in the temperate climate zone

Hedgerows are a traditional form of agroforestry in the temperate climate zone. The establishment of hedgerows may be a promising strategy to promote carbon (C) sinks for climate change mitigation. We therefore conducted a meta-analysis compiling data from 83 sites on soil organic carbon (SOC) stocks beneath hedgerows in comparison with adjacent croplands and grasslands, plus biomass data from 64 hedgerows. On average (+/- SD), the establishment of hedgerows on cropland increased SOC stocks by 32 +/- 23 %. No significant differences were found between the SOC stocks of hedgerows and those of grassland. The average above-ground biomass stock was 47 +/- 29 Mg C ha(-1). Only one study reported measurements of below-ground biomass stocks and root/shoot ratios. Based on these measurements, an average below-ground biomass stock of 44 +/- 28 Mg C ha(-1) was estimated, but with high uncertainty. In total, hedgerows were estimated to store 104 +/- 42 Mg ha(-1) more C than croplands, with biomass contributing 84 % (87 +/- 40 Mg C ha(-1)) and soil 16 % (17 +/- 12 Mg C ha(-1)) to this amount. Total C sequestration with the establishment of hedgerows on cropland could be between 2.1 and 5.2 Mg ha(-1) year(-1) for a period of 50 and 20 years, respectively. Our results indicate that C stocks in hedgerows are on average comparable to estimates for forests. The establishment of hedgerows, especially on cropland, can therefore be an effective option for C sequestration in agricultural landscapes while enhancing biodiversity and soil protection.