Chemical fertility of forest ecosystems. Part 2: Towards redefining the concept by untangling the role of the different components of biogeochemical cycling

Legout Arnaud, Hansson Karna, Van Der Heijden Geertje, Laclau Jean-Paul, Mareschal Louis, Nys Claude, Nicolas Manuel, Saint-André Laurent, Ranger Jacques. 2020. Chemical fertility of forest ecosystems. Part 2: Towards redefining the concept by untangling the role of the different components of biogeochemical cycling. Forest Ecology and Management, 461:117844, 16 p.

https://doi.org/10.1016/j.foreco.2019.117844

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Quartile : Q1, Sujet : FORESTRY

Résumé : Many forest ecosystems are developed on acidic and nutrient-poor soils and it is not yet clearly understood how forests sustain their growth with low nutrient resources. In forestry, the soil chemical fertility is commonly defined, following concepts inherited from agronomy, as the pool of plant-available nutrients in the soil at a given time compared to the nutritional requirement of the tree species. In this two-part study, Part 1 (Hansson et al., 2020) showed, through the compiled dataset of 49 forest ecosystems in France, Brazil and Republic of Congo, the limits of this definition of soil chemical fertility in forest ecosystem contexts. In this study (Part 2), we investigated the nutrient pools and fluxes between the different ecosystem compartments at 11 of the 49 sites in order to better characterize the role of the biogeochemical cycling of nutrients in the chemical fertility of forest ecosystems, and in particular the roles of the biological and geochemical components of biogeochemical cycling. The analysis of our dataset shows different types of biogeochemical functioning. When the geochemical component (inputs through mineral weathering and/or atmospheric inputs, capillary rise) is predominant, sufficient nutrients are provided to the plant-soil system to ensure tree nutrition and growth. Conversely, when the geochemical component of the cycle brings too few nutrients to the plant-soil system, the biological component (litterfall, plant internal cycling) becomes predominant in tree nutrition and growth. In the latter case, forest production may be high even when pools of nutrients in the soil reservoir are low because small but active nutrient fluxes may continuously replenish the soil reservoir or may directly ensure tree nutrition by bypassing the soil reservoir. This study highlights the necessity to include biogeochemical cycling and recycling fluxes in the definition and diagnosis methods of soil chemical fertility in forest ecosystems. We show that the chemical fertility is not only supported by the soil in forest ecosystem but by the sum of all the ecosystem's compartments and fluxes between these pools.

Mots-clés Agrovoc : écosystème forestier, forêt, cycle dans les écosystèmes, fertilité du sol, transport des substances nutritives, propriété physicochimique du sol

Mots-clés géographiques Agrovoc : France, Brésil, Congo

Mots-clés libres : Chemical fertility, Biological cycling, Nutrition, Forest, Soil

Classification Agris : K01 - Foresterie - Considérations générales
P35 - Fertilité du sol
F40 - Écologie végétale

Champ stratégique Cirad : CTS 1 (2019-) - Biodiversité

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