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Communication Dans Un Congrès Année : 2018

A study of the main factors influencing soil organic carbon stock distribution in urban soils, at French scale.

Résumé

Soils are the largest pool of terrestrial organic carbon. They can behave as a sink or a source of atmospheric CO2 (Jacobson et al., 2000). To mitigate climate change, soil organic carbon (SOC) maintenance is an important issue; moreover, SOC is a key property related to soil chemical, biological and physical fertility. Artificialized areas represent nearly 3% of the World territory (9.3% in France), and by 2050 the proportion of the urban population is expected to reach 66% worldwide. However, available data to assess whether urbanization, including land conversion to collective gardens, leads to an increase or decrease of SOC are extremely scarce; the observation is the same for the main factors explaining the SOC distribution in these very heterogeneous soils. However, it is clear that the fertility of urban land for the development of an urban local agriculture is vitally dependent on the carbon content of the soil. Our hypothesis is then that the anthropic factors (i.e. land use types and management) and vegetation cover mostly explain SOC distribution in urban soils, at a territorial scale (Joimel et al., 2016). The first objective is to link the urban soil use, management and vegetation cover to their soil organic carbon stock (SSOC), at French territorial scale. The second objective is to determine whether these factors explain the most SSOC distribution in French urban soils, compared to extrinsic natural factors and soil characteristics (e.g., climate, nitrogen content, carbonate content, clay content). The third objective is to propose a mapping of urban SOC in order to better guide land use planning and to preserve the most suitable soils for urban agriculture. This work is based on a systematic data collection from different organizations (e.g., research institutes and associated project leaders, cities and urban agglomerations), over France, which have accepted to share their data for this study. More than 10,000 data, displaying environmental characteristics, SOC contents and other soil properties (e.g., cation exchange capacity, pH, nitrogen and carbonate contents and soil texture), were collected. After SSOC estimation, a statistical treatment was conducted to characterize the different types of urban soils, according to their SSOC and the main factors explaining SSOC distribution. We have tested the effect of extrinsic parameters such as climate, urban land use (a classification of 14 types of uses, including collective gardens, adapted from Micand and Larramendy, 2014), vegetation cover (herbaceous, horticultural massive, tree or vegetation mix covers), management frequency and age of the site. The effects of the available intrinsic soil properties were also tested. The effects of the anthropic factors (land use, age of site, and type of vegetation) on SSOC were the most significant and allowed to regroup the urban soils in three different categories, according to their SSOC: i) sealed soils; ii) open vegetated and strongly managed soils, such as soils used for urban agriculture; iii) open vegetated and near-natural soils. The climate had also a significant effect on SSOC distribution as well as the following soil properties: nitrogen and clay contents. According to these results, it will be necessary to focus on the three urban soil categories in different French cities, under contrasted climatic conditions, in order to understand the SOC dynamics, at the soil profile scale. Thus, the need for exogenous organic carbon in soils likely to be suitable for urban agriculture projects can be assessed.
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Dates et versions

hal-02511892 , version 1 (19-03-2020)

Identifiants

  • HAL Id : hal-02511892 , version 1

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Aurélie Cambou, Laure Vidal Beaudet, Patrice Cannavo, Christophe Schwartz. A study of the main factors influencing soil organic carbon stock distribution in urban soils, at French scale.. International congress Sustainable Urban Agricultures: Vector for the Ecological Transition, Jun 2017, Toulouse, France. pp.Session 1 : Urban Agronomy. ⟨hal-02511892⟩
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