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Consequence of clear-cutting and drought on deep soil CO2 and N2O profile concentrations and surface fluxes in Brazilian eucalypt plantations

Germon A., Jourdan C., Chapuis-Lardy L., Robin A., Antonio Rosolem C., De Moraes Gonçalves J.L., Amaral Guerrini I., Laclau J.P.. 2017. In : Book of Abstracts IUFRO 125th Anniversary Congress 2017. Baden-Württemberg : Forstliche Versuchs- und Forschungsanstalt (FVA); IUFRO, p. 385-385. 125th IUFRO Anniversary Congress, 2017-09-18/2017-09-22, Freiburg (Allemagne).

The major factors driving greenhouse gas effluxes from forest soils (substrate supply, temperature, water content) vary with soil depth. Our study aimed to assess the consequences of drought on the temporal variability of CO2 and N2O fluxes throughout very deep soil profiles in Eucalyptus grandis plantations at the end of the rotation and the first 16 months after clear-cut, in coppice. Two treatments were compared: one with 37% of throughfall excluded by plastic sheets (TE), and one without rain exclusion (WE). Every two weeks for 19 months, soil CO2 and N2O surface fluxes were measured using the closed-chamber method and the profile concentrations were measured at 7 depths in the soil down to 15.5m from in each treatment. CO2 and N2O concentrations measured in treatment TE were on average 17.3 and 5.8% lower than in treatment WE, respectively, throughout the soil profile. Across the two treatments, CO2 concentrations increased from 4102 ±2310 ppm at 10cm deep to 14480±2854 ppm at 15.5m and N2O concentrations remained roughly constant down to 15.5m. Improving our understanding of the spatiotemporal dynamics of gas concentrations in deep soil layers is an important issue for the management of tropical planted forests in the context of climate change.

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