Most of the physiognomies of the Brazilian Cerrado fall within the definition of tropical savanna. However, patches of seasonal forest are interspersed within the Cerrado. The occurrence of savannas in areas whose climate allows forests may be related to the nutrient-poor soil, especially nitrogen (N) and phosphorus (P). We analysed the initial development of a congeneric pair, Handroanthus aureus, a savanna species, and H. impetiginosus, a seasonal forest species, to test whether these nutrients shape their functional traits differently. We used a hydroponic system with four treatments: (1) complete Hoagland solution containing N, P, K, Ca, Mg, S, O, H, Cl, B, Mn, Zn, Cu, Mo and Fe (2) Hoagland solution without P, (3) Hoagland solution without N, and (4) Hoagland solution without both nutrients. We followed the plants for three months and measured total biomass, aboveground biomass, root-to-shoot ratio, height, cotyledon persistence, appearance of the first pair of leaves, and leaf area. Growth of both species was sensitive to nitrogen availability. Supplemental phosphorus increased values of all traits in forest species but decreased some trait values in the savanna species. Except for root-to-shoot ratio and height which were higher in H. impetiginosus, the values for the other traits were consistently higher in H. aureus. The savanna species was more efficient overcoming N and P deficiencies. The two species were already ecologically distinct at early stages of development, which may be related to their evolutionary history regarding nutrients availability.

中文翻译：

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在不同氮和磷利用率下，同属热带稀树草原和季节性林木的早期生长

巴西塞拉多的大多数地貌都属于热带稀树草原的定义。但是，塞拉多境内散布着季节性的森林。稀树草原在气候允许森林的地区的发生可能与营养不良的土壤有关，尤其是氮（N）和磷（P）。我们分析了一个同类对的初步发展，Handroanthus aureus，一种热带稀树草原和H. impetiginosus，一种季节性的森林物种，以测试这些养分是否对它们的功能特征产生不同的影响。我们使用了水培系统，并进行了四种处理：（1）包含N，P，K，Ca，Mg，S，O，H，Cl，B，Mn，Zn，Cu，Mo和Fe的完整Hoagland溶液（2）Hoagland溶液没有磷，（3）没有N的Hoagland溶液，和（4）没有两种营养素的Hoagland溶液。我们跟踪了植物三个月，并测量了总生物量，地上生物量，根茎比，高度，子叶持久性，第一对叶片的外观以及叶片面积。两种物种的生长都对氮的有效性敏感。补充磷增加了森林物种所有性状的值，但降低了热带稀树草原物种的某些性状值。黑斑病菌根茎比和高度均较高在金黄色葡萄球菌中其他性状的值始终较高。稀树草原物种更有效地克服了氮磷缺乏症。这两个物种在发展的早期阶段就已经在生态上有所不同，这可能与其在养分供应方面的进化史有关。