Search

Soil organic carbon (SOC) sequestration is a key function of natural and semi-natural ecosystems. Restoring this property in terrestrial ecosystems has become central to the EU's climate change mitigation and adaptation strategies. However, SOC sequestration is a widely misunderstood concept. The different methodological approaches used to investigate and compare SOC stock under sustainable agricultural practices play a key role in reinforcing misconceptions about this complex process. This commentary paper aimed not only to provide a clear definition of SOC sequestration, but also to interpret the results that can be obtained for SOC stock change estimation using the SOC stock difference and the paired comparison methods, as well as to identify the soil carbon-related processes that achieve climate mitigation. SOC sequestration can be defined as the progressive increase in a site's SOC stock compared with pre-intervention via a net depletion and transfer of atmospheric CO2 into the soil, where it is retained as soil organic matter (SOM), by plants, plant residues, or other organic solids such as the material derived from the organic fraction of farming solid waste, which can be used as a fertilizer (e.g., manure, compost, biochar, and digestate), and that is produced or derived from that land unit. To date, the most appropriate way to determine whether a land unit's soil is a sink or rather a source of atmospheric CO2 is to implement the SOC stock difference method, provided the non-occurrence of carbon exchange between ecosystems. [ABSTRACT FROM AUTHOR]

In terrestrial biosphere, soil represents the largest organic carbon pool, and a small change of soil organic carbon (SOC) can significantly affect the global carbon cycle and climate. Land use change (LUC) and soil management practices coupled with climate variables can significantly influence the soil organic carbon stocks (SOC–S) and its dynamics; however, our understanding about the responses of SOC in different LUC's (e.g., cropland, grassland and forest land) to mitigate climate change is quite limited at country level like Italy. Thus, the aims of this study were which factors are affecting SOC dynamics in three LUC's over time across Italy; and their relevance in terms of SOC–S in the superficial layer of soil that significantly contributes to the climate change mitigation, using LUCAS soil database. To calculate the SOC–S, it is necessary to have soil bulk density (BD) which is not present in the LUCAS database. Thus, we estimate the soil BD using the pedotransfer function (PTFs); and results shows that the soil BD obtained from fitting of the PTFs were reasonable to estimate the SOC–S for different land use types (R2 ≥ 0.75). Overall, results showed that LUC's and soil management practices can significantly (p < 0.001) influences SOC dynamics and SOC storage from the soil and varied among LUC's but not for over time except grassland. Spatially, the mean SOC–S storage of the different LUC's was in the following order: forest land > grassland > cropland for both years 2009 and 2015. On the other hand, the SOC–S storage increased by 8.33% for cropland, 13.56% for forest land, and 29.79% for grassland during the year of 2009–2015, while SOC–S storage increased significantly (p < 0.001) in grassland over time but not for cropland and forest land which also follow the increasing trend but insignificantly. Our results also reveal that the SOC dynamics negatively correlated with MAT, and positively correlated with MAP for all land uses except forest land. Thus, this research indicates that LUC's and soil management practices coupled with climate variables can significantly influence SOC storage and its dynamics in the superficial layer of soil which have the potential capacity to mitigate climate change. [Display omitted] • Using PTFs for obtaining soil BD was reasonable to estimate the SOC–S for different LUTs. • SOC negatively correlated with MAT and positively correlated with MAP for all LUT except forest land. • Among LUTs, forest land could store highest SOC in both years compared to grassland and cropland. • Over time, SOC–S increased significantly (p < 0.001) in grassland but not for forest land and cropland. [ABSTRACT FROM AUTHOR]

Background and Objectives: Over the last few decades, the European mountain environment has been characterized by the progressive abandonment of agro-pastoral activities and consequent forest expansion due to secondary succession. While woody encroachment is commonly considered as a climate change mitigation measure, studies suggest a still uncertain role of the soil organic carbon (SOC) pool in contributing to climate change mitigation during this process. Therefore, the objective of the study is to investigate the possible SOC variations occurring as a consequence of the secondary succession process at the provincial level in an Alpine area in Italy. Materials and Methods: A chronosequence approach was applied to identify, in five different study areas of the Belluno province, the land use/land cover change over four different stages of natural succession, from managed grazing land to secondary forest developed on abandoned grazing land. In each chronosequence stage, soil samples were collected down to the bedrock (0–60 cm depth) to determine the changes in the SOC stock due to the woody encroachment process. Results: In all areas, small or no significant (p < 0.05) SOC stock changes were observed during the secondary succession in the upper 30 cm of mineral soil, while significant changes were evident in the 30–60 cm compartment, with the SOC stock significantly decreasing from 30% to 60% in the final stage of the succession. This fact indicates the great importance of considering also the subsoil when dealing with land use/land cover change dynamics. Conclusions: The recorded trend in SOC has been proved to be the opposite in other Italian regions, so our results indicate the importance of local observation and data collection to correctly evaluate the soil contribution to climate change mitigation during woody encroachment. [ABSTRACT FROM AUTHOR]

Sustainable agricultural and food processing practices are often proposed as attractive strategies enabling food systems to respond to the challenges posed by climate change in terms of adaptation and mitigation. However, information on the actual contribution to climate change provided by sustainable food production systems is lacking in literature. With the intention to contribute to a more informed debate, this study aims at quantify the actual impact on climate of sustainable practices applied to a grape-to-wine system in Italy. The overall budget of greenhouse gas (GHG) fluxes is assessed at wine farm level, from the vineyard to the final bottle of wine, through an integration of methods, including the eddy covariance technique, the life cycle assessment (LCA) and the IPCC guidelines. All the components of the GHG budget have been considered: the (a) biogenic GHG fluxes and the (b) anthropogenic GHG emissions generated for the grape production as well as the (c) carbon stock change due to the vineyard management and the (d) anthropogenic GHG emissions generated by the transformation of grape into wine. At the vineyard level, the overall GHG budget resulted to be close to zero, showing a potential carbon neutrality of sustainable viticulture: the sum of biogenic GHG fluxes (a) and the carbon stock change (c) resulted in a net carbon sink with a potential contribution to climate change mitigation of −0,27 ± 1,11 Mg CO 2 eq year−1 per hectare; while the anthropogenic GHG emissions (b) for the sustainable vineyard management accounted for 0,24 ± 0,05 Mg CO 2 eq ha−1 year−1. The total carbon footprint (b + d) of sustainable wine is 0,79 ± 0,14 kg CO 2 eq per bottle, with 15% attributable to the agricultural phase and 85% to the transformation of grape into wine. These findings indicate that sustainable wine production has in general a lower contribution to climate change. In particular, sustainable practices applied to viticulture can turn the system into a net carbon sink able to totally compensate the anthropogenic emissions for the vineyard management. Therefore, sustainable viticulture allows food production with a potential carbon neutrality without exacerbating climate change. • Sustainable viticulture allows food production with a potential carbon neutrality without exacerbating climate change. • Sustainable viticulture generates biogenic GHG fluxes that turn the agrosystem into a net carbon sink. • Anthropogenic GHG emissions in sustainable vineyard are low and can be totally compensate by the net carbon sink. • The carbon footprint (CF) of sustainable wine is 0,79 ± 0,14 kg CO 2 eq per bottle. • Sustainable wine production has in general a lower contribution to climate change. [ABSTRACT FROM AUTHOR]

Carbon farming has been recently proposed as an effective measure for climate change mitigation through carbon (C) sequestration or C emissions reduction. In order to identify and estimate the climate change mitigation potential of carbon farming practices on European croplands we conduct a systematic review on both relative and absolute annual soil organic carbon (SOC) stock change (ΔSOC REL; ΔSOC ABS) related to single and combined agroecological practices tested on mineral soils at a minimum of 0–30 cm and up to 150 cm soil depth whenever data were available. We used the term ΔSOC REL for SOC stock changes determined by the paired comparison method and the term ΔSOC ABS for those calculated using the SOC stock difference method. We compiled a dataset with more than 700 records on SOC change rates representing 12 carbon farming practices. Mean ΔSOC REL in Mg C ha−1 yr−1 at 0–30 cm soil depth were collected for cover crops (0.40 ± 0.32), organic amendments (0.52 ± 0.47 and 0.38 ± 0.37 when the control is respectively unfertilized or liquid organic amendment), crop residue maintenance (0.14 ± 0.06), improved rotations (0.21 ± 0.16), reduced soil disturbance (0.24 ± 0.34), silvoarable systems (0.21 ± 0.08), organic (0.9 Mg ± 0.25) and conservation management (0.78 ± 0.62), set-aside (0.75 ± 0.68 and −0.39 ± 0.50 when the control is respectively cropland or pasture/grassland), cropland conversion into permanent grassland (0.79 ± 0.47), poplar plantations (0.25 ± 0.68 and −0.85 ± 0.53 when established on cropland or pasture/grassland). SOC sequestration was detected only for organic amendments, cover crops, poplar plantations, conservation management, organic management, and combined carbon farming practices for which we estimated a median ΔSOC ABS ranging between 0.32 and 0.96 Mg C ha−1 yr−1 at 0–30 cm. The ΔSOC ABS observed at 0–30 cm soil depth from cropland conversion into short rotation forestry resulted in an increase of C, while negative values were observed when the control was grassland. Cropland conversion into permanent grassland or pasture showed positive ΔSOC REL at 0–30 and 0–90 and 0–100 cm soil depth. Reduced soil disturbance full soil profile assessment at 0–50 cm soil depth completely counterweighted any SOC stock increase found in topsoil at 0–30 and 0–40 cm soil depth, therefore resulting in no net climate benefit. Conservation management, organic management, and combining cover crops with organic amendments are the most effective strategies shifting arable land from C source to net sink, with median ΔSOC ABS at 0–30 cm soil depth of 0.63, 0.91 and 0.96 Mg C ha−1 yr−1, respectively. Permanent grasslands and pastures were negatively affected by any type of land-use change, at least in topsoil. Natural ecological successions after cropland abandonment (20-year set-aside), or arable land conversion into poplar plantations and grassland promote relative SOC stock annual increase by 1.08, 0.77 and 0.33 at 0–30 cm respectively, while the net climate benefit remains unclear when subsoils are assessed. • Carbon farming practices are effective for climate change mitigation. • A dataset of annual SOC stock changes from carbon farming practices is presented. • Organic farming and cover crops with organic amendments thrive in climate mitigation. [ABSTRACT FROM AUTHOR]