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

Abstract

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.

The Role of Small Woody Landscape Features and Agroforestry Systems for National Carbon Budgeting in Germany

“…The literature search was limited to central Europe, with focus on Germany. The hedgerow biomass was adapted from Drexler et al (2021) [37] as a proxy for all linear SWFs, values for orchards were adapted from Strohbach and Haase, (2012) [38] and values for vineyards were adapted from the IPCC report (2019) [27]. The steps taken to estimate total biomass carbon (TBC) in non-linear (patchy and additional) SWF structures in cropland and grassland landscape matrices were as follows: Prior to the analysis, all datasets were reprojected to EPSG 25832 and resampled to a 5 m resolution.…”

“…The SOC (soil depth of 0-30 cm) for linear SWFs was adopted from Drexler et al (2021) [37], based on findings by Axe et al (2017) [43]. The SOC (0-30 cm) for patchy and additional SWFs on cropland was estimated by applying the same TBC-to-SOC (21:4) ratio established by Drexler et al (2021) [37]. The empirically derived SOC data (0-30 cm) for cropland, grassland, orchard, and vineyard systems were adapted from the Thünen Report 64 [8].…”

“…The SWF SOC stocks were assumed to be 17 ± 12 Mg C ha −1 (linear SWFs) [24] and 10 ± 8 Mg C ha −1 (patchy and additional SWFs) higher relative to the SOC stocks established for cropland, orchard, and vineyard systems. No change in SOC for SWFs on grassland was assumed based on findings by Drexler et al (2021) [37] and Cardinael et al (2018) [26]. For a detailed breakdown of values, see Appendix A (Table A1).…”

“…• Calculate carbon in below-ground (BLG) biomass as a fraction (0.23 ± 75%) of the mean ABG carbon [37].…”

“…Sum up ABG C stock and BLG C stock to obtain TBC stock [37]. 1 For linear features, the mean ABG and BLG were available from literature, with an expected 50% loss of biomass applied in accordance with the IPCC Tier 1 assumption for the agroforestry systems [27].…”