Environmental filters and functional adjustments of species to local conditions are major determinants of plant communities in stressing habitats. We set out to understand the role of different substrates in functional trait variation in wood plants by investigating key functional traits at the community and intraspecific levels in different types of Brazilian savanna: two sites of alluvial savannas (lowland savannas that occur in old alluvial deposits in riverbeds with sandy soils and low water-holding capacity), and two sites of typical savannas (upland savannas that occur in interfluvial zones, far from the influence of rivers, in which clay soils with higher fertility and water-holding capacity predominate). We conducted this study in four sites with savanna vegetation in the northeast region of the Cerrado Biome, nearby the transition with the Amazon. In each site we sampled six functional traits for each tree species: leaf area, leaf thickness, specific leaf area (SLA), stem-specific density, relative bark thickness and maximum plant height. We sampled 101 wood species, ranging from 26 to 62 species within each site. In both community and intraspecific levels, alluvial savanna plants showed higher SLA and specific-stem density, and lower leaf area, leaf thickness, bark thickness, and plant height compared with the typical savanna. We also found that, at a given leaf thickness, species from typical savanna exhibited ∼20% higher SLA. In addition, at a given plant height, typical species showed ∼56% higher bark thickness and ∼20% lower specific-stem density. Our findings suggest that savanna tree species growing on alluvial savannas tend to adopt strategies related to water acquisition while species growing on typical savannas invest in both water conservation strategies and protection against high-intensity fires. We conclude that water deficit and fire, both related to substrate properties, play a key role in determining the woody plant communities functioning in savannas.

环境过滤器和物种对当地条件的功能调整是植物群落压力栖息地的主要决定因素。我们开始通过调查不同类型巴西稀树草原的群落和种内水平的关键功能特征来了解不同基质在木植物功能特征变异中的作用：两个冲积稀树草原（发生在沙质土壤和低持水能力的河床），以及两个典型热带稀树草原（发生在河流间地带的高地稀树草原，远离河流的影响，其中具有较高肥力和保水能力的粘土占主导地位）。我们在塞拉多生物群系东北部的四个稀树草原植被地点进行了这项研究，附近与亚马逊的过渡。在每个地点，我们为每个树种采样了六个功能性状：叶面积、叶厚度、比叶面积 (SLA)、茎比密度、相对树皮厚度和最大植物高度。我们对 101 种木材进行了采样，每个地点的木材种类从 26 到 62 种不等。在群落和种内水平上，与典型稀树草原相比，冲积稀树草原植物表现出更高的 SLA 和特定茎密度，以及更低的叶面积、叶厚、树皮厚度和植物高度。我们还发现，在给定的叶片厚度下，来自典型稀树草原的物种表现出高约 20% 的 SLA。此外，在给定的植物高度下，典型物种的树皮厚度增加了约 56%，茎干密度降低了约 20%。我们的研究结果表明，生长在冲积稀树草原上的稀树草原树种倾向于采取与水获取相关的策略，而生长在典型稀树草原上的物种则在节水策略和防止高强度火灾方面进行投资。我们得出结论，缺水和火，两者都与基质特性有关，在确定热带稀树草原中木本植物群落的功能方面起着关键作用。