The savannas (called Cerrado) are the second-largest vegetation formation in Brazil after the Amazon rainforest, with about 2 million km². Roots have been found in very deep soil layers in Cerrado ecosystems, which suggests a crucial role of deep rooting in the supply of water and nutrients over dry periods. The aim of our study was to gain insight into the complementarity of common Cerrado woody species in taking up mobile nutrients throughout deep soil profiles. In a closed-canopy savanna with dense woody understory, labeled nitrate was injected into the soil at six soil depths (0.1, 1.5, 3.0, 6.0, 9.0, or 12.0 m) with three plots per depth, at two dates (in rainy and dry seasons). Five months after labeled nitrate injection, young leaves were sampled and foliar δ¹⁵N was determined in each plot in the three most common woody species (Coussarea hydrangeifolia, Miconia albicans and Xylopia aromatica). The maximum depth of ¹⁵N uptake was dependent on the species. X. aromatica trees took up ¹⁵N from a maximum depth of 9 m and exploited a much larger soil volume than the two other species, with the uptake of ¹⁵N at a horizontal distance of up to 5 m between the trunk and the injection site. The behavior of M. albicans and C. hydrangeifolia was similar, with a strong uptake of ¹⁵N only in the 0-1.5 m soil layer, within 2 m horizontally from the injection site. The depth of ¹⁵N uptake over the dry season was not related to the diameter at breast height of the woody plants sampled. We show that roots can take up labeled nitrogen from a depth of 9 m in tropical wooded savannas, which suggests an important role of deep-rooted species in closing biogeochemical cycles on highly weathered tropical soils.

稀树草原（称为Cerrado）是仅次于亚马逊雨林的巴西第二大植被地带，约有200万平方公里²。在塞拉多生态系统的非常深的土壤层中发现了根，这表明深生根在干旱时期的水和养分供应中起着至关重要的作用。我们的研究目的是深入了解常见的塞拉多木本植物在深层土壤剖面中吸收流动性养分时的互补性。在具有茂密的木质林下的封闭林冠稀树草原中，将标记的硝酸盐以六个深度（0.1、1.5、3.0、6.0、9.0或12.0 m）注入土壤，每个深度三个地块，在两个日期（雨天和雨天）。旱季）。标记硝酸盐注射后五个月，幼叶取样和叶面δ ¹⁵n为在三种最常见的木本物种每个小区（确定Coussarea hydrangeifolia，Miconia白色念珠菌和Xylopia郁金）。¹⁵ N吸收的最大深度取决于物种。X.郁金树木拿起¹⁵从9米的最大深度N和利用大得多的土壤体积比两个其它物种，与摄取¹⁵ Ñ在高达的水平距离至5μm躯干和注射部位之间。白色念珠菌和绣球梭菌的行为相似，被¹⁵的强烈吸收仅在距注入点水平2 m以内的0-1.5 m土层中存在N。干旱季节吸收¹⁵ N的深度与取样的木本植物的胸高直径无关。我们表明，在热带树木繁茂的稀树草原中，根部可以吸收9 m深度的标记氮，这表明深根物种在封闭高度风化的热带土壤中的生物地球化学循环中具有重要作用。