D3DC

Studying the 3D dynamic evolution of soil organic carbon driven by erosion and land use changes at the landscape scale

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 Obiettivo del progetto (Objective)

'Soil respiration is expected to make a major contribution to C cycle feedbacks in a changing climate, but the magnitude of these feedbacks are highly uncertain. One of the most important shortcomings is that soils must be viewed as spatially heterogeneous and dynamic systems at the landscape scale if we are to understand soil biogeochemistry and soil carbon cycling in particular. Consequently, improving our understanding of (i) the vertical and lateral translocation of SOC by erosion as well as its stability and (ii) the coupled effects of land use change on SOC 3 dimensional distribution becomes an important issue. In this study, we aim to couple soil respiration experiments at depth and empirical and process-based spatial models to meet these objectives. This must allow us to predict the temporal evolution of SOC at the landscape scale within a 3 dimensional context. First, parameters of the SOC depth distribution model of Meersmans et al. (2009) will be modeled as function of time, slope position variables and land use change type. The results of these empirical modeling will be compared with dynamical process-based models results, such as SPEROS-C. In order to separate the effects of erosion and land use change on SOC, we intend to study the later on profiles in equilibrium (i.e. non eroded and constant land use) and on sites characterized by changed land use and/or erosion. Secondly, the stability of organic matter at different depths in soil profiles from both eroded and depositional areas will be investigated by measuring CO2 production in incubation experiments. To refine the 3 dimensional estimation of SOC dynamics at the landscape scale the output of these first two work packages will be incorporated in existing process based C profile models (i.e. Roth C based) and spatially explicit models (i.e. SPEROS-C). In addition we aim to upscale the land surface scheme JULES by developing methods to integrate the outcomes of our study in this large scale ES model.'

Introduzione (Teaser)

Soil organic carbon (SOC) plays an important role in soil quality and is a crucial and active component of the global carbon cycle. An EU-funded consortium studied the effect of soil erosion on SOC distribution.

Descrizione progetto (Article)

The advent of intensive agriculture in the second half of the 20th century significantly increased soil erosion. One consequence was changes to the distribution of SOC, especially within croplands under conventional tillage.

Although attempts have been made to map SOC at national scale based on land use, soil type and climate, detailed predictions of SOC were lacking. The EU-funded D3DC project addressed this situation, studying SOC at smaller scales in complex terrains and influenced by water and tillage erosion.

The project aimed to improve understanding of the vertical and horizontal movement of SOC caused by erosion, as well as its stability. This was achieved by coupling soil respiration experiments at depth with empirical and process-based spatial models.

Project partners studied the variation in quantity and quality of SOC depth distribution along typical hillside transects under cropland in Devon, United Kingdom. The results were related to soil redistribution rates and variations in carbon input (below- and above-ground biomass productivity).

Measurements of carbon dioxide (CO2) production in long-term incubation experiments were used to study stability of organic matter at different depths in soil profiles from both eroded and depositional areas. Results showed contrasting vertical patterns in SOC stock and stability depending on the rate and type of erosion.

Results from D3DC will help to improve long-term soil fertility and carbon storage management in eroding landscapes. This is an important step in the evolution of 3D spatial models of SOC dynamics and their implementation in land surface exchange schemes of Earth System models.

Researchers also predicted how the distribution of SOC in France will evolve as a result of climate and land-use changes until the year 2100. This will enable scientists to identify those regions most likely to experience a significant gain or loss of SOC. It will also reveal the extent to which land-use decisions and outcomes control the scale of SOC gain or loss.

The methodology developed by D3DC and the resulting maps will act as powerful tools for supporting decision making regarding appropriate soil management. This may involve increased SOC storage, thereby reducing soil-related CO2.