Laboratory of Conservation and Dynamics of Volcanic Soils

FONDECYT PROJECT

This study seeks to understand the nitrogen (N) cycle and its transformation steps in the soils of temperate rainforests (Valdivian forest). in temperate rainforests (Valdivian rainforest), since these forests (native to southern Chile) show low available N concentration and greenhouse gas and greenhouse gas losses in these forests (native to southern Chile), unlike similar forests in the northern hemisphere. similar forests in the northern hemisphere. This is partly explained by: i) the biological reduction of nitrate to ammonium under anaerobic conditions. ammonium under anaerobic conditions and ii) by the Ferrous Wheel (FW) hypothesis. This hypothesis was recently tested for the first time in a laboratory experiment with Valdivian forest soils. Valdivian forest. FW indicates that soluble iron, which is high in these soils, is capable of acting on the mineral N-mineral nitrogen, fixing it as organic nitrogen and preventing this N from concentrating in the soil and being lost to water currents. water currents and being lost as greenhouse gases. This has important ecological implications from the point of view that native forests present a very closed N cycle in the face of global warming. global warming. In the present study, FW will be evaluated in field conditions under the influence of soils derived from various parent materials. of soils derived from various parent materials (e.g., recent volcanic ashes) with different iron and N contents along the iron and N contents along the foothills of the Chilean Andes and the Coastal Cordillera. The abiotic FW mechanism (chemical process) will be tested and linked to other biotic mechanisms (presence of microorganisms). (presence of microorganisms), which would largely explain the absence of N-mineral loss in the native forest estuaries and the and its scarce losses as gaseous N. This study will be carried out on several types of soils of soils originating from different geological materials in order to cover the whole range of soil properties, the results of which can be whose results can be extrapolated to similar sites elsewhere in the world. The following will be applied N stable isotopes will be applied as natural tracers to see at what rate and how much N accumulates in the different soil organic N different soil organic N pools. It is expected to find a large fixation of N in organic forms which would contribute to the drying of the soil. which would contribute to carbon and N sequestration with important implications for this type of ecosystems.

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