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Is there a niche complementarity for nitrate uptake among savannah shrub and tree species in a very deep Brazilian soil?

Pinheiro R., Laclau J.P., Guerrini I.A., Alo L., Bouillet J.P.. 2019. Pesquisa Florestal Brasileira, 39 : p. 644-644. IUFRO World Congress 2019 "Forest Research and Cooperation for Sustainable Development". 25, 2019-09-29/2019-10-05, Curitiba (Brésil).

Belowground niche complementarity between deep-rooted and shallow-rooted species in mixed forests may result in a more complete exploitation of soil resources than in monocultures. Our study aimed to assess 1) the maximum distance (horizontally and vertically) where the fine roots from common Cerrado species take up mobile nutrients in deep Ferralsols. and 2) whether there is a niche complementarity in nitrate uptake between some Cerrado species. Our study was carried out in a closed-canopy forest with dense woody understory (cerradão) at Bauru (Sao Paulo State); 15N-NO,- was injected at the onset of dry and rainy seasons at 6 depths (0.1. 1.5, 3. 6. 9 and 12 m) with 3 plots per depth and a distance> 50 m between each injection depth Leaves were sampled 4 months after tracer injection in 3 frequent species in each plot located at 4 intervals of distance from the tracer injection point (0-2 m; 3-6 m; 7-10 m; >12 m) and 15N atom% was determined. Great differences in 15N tracer uptake between the studied species showed a niche complementarity in this native savannah. Xylopia aromatica exhibited a strong 15N uptake at 6 m of depth, irrespective of the season. This species seems to exploit a much larger soil volume than the others, both vertically and horizontally (15N taken up at 5 m from the injection point). Miconia albicans and Coussarea hydrangeifolia showed similar behaviours, with a strong 15N uptake in the topsoil and down to 1.5 m depth. within 2 m from the injection point.

Mots-clés : forêt mélangée; arbuste; savane; nitrate; ressource minérale; système racinaire; brésil; cerrado; xylopia aromatica; miconia albicans; coussarea hydrangeifolia

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