OOS 45-1 - Contrasting Plant function across different tropical environments - rainforest to savannah

Plants in the Brazilian savannas, known as Cerrado, must cope with high radiation, nutrient-impoverished soils, seasonal droughts, and fires. In contrast, tropical forests are usually associated with a more resource rich environment. Given this, we expect both biomes to have plants with different life-history strategies, with the Cerrado having a more conservative strategy to cope with more stressful environmental conditions. Although both biomes are likely to maintain a relatively large diversity of traits, driven by trade-offs between water-use, nutrient acquisition, carbon assimilation and fire protection, in the case if savannas, we hypothesise the trait space occupied it likely to be greater in tropical rainforests, where resource availability is greater.
We measured key functional traits across savannah trees and shrubs to investigate this variability and traits co-variance. We compared this data with tropical forests global databases and contextualize the data collected in savannas. We found the range of some traits (i.e. P50, Ks, Huber Value, wood density, Asat) for the Cerrado to almost cover the entire range occupied by all other biomes, including tropical forest. However, for other traits, such as LMA and nutrients, the Cerrado was distinctly different in the trait space it occupied, most likely due to special adaptations to deal with particularly nutrient impoverished soils. Despite savannas and tropical forests having contrasting environmental characteristics, which would normally be associated opposite ends of the fast-slow continuum of life-history strategies, they both occupy a very wide and overlapping trait space. Despite the large functional trait space Cerrado species occupy, we did find some well-established traits co-variances. For example, traits related to hydraulic resistance correlated with woody nutrition and leaf structural traits, while the wood density had a trade-off with many other traits reinforcing its nature as a multifunctional characteristic. However, our results show leaf and woody traits may not coordinate in the same way as found in other biomes. Species that were very conservative at the leaf-level, did not necessarily have woody tissue that was highly resistant embolism, for example. It is possible these species can access deep water or have other strategies to protect their xylem, but not their leaves.
Our results show a clear need to look at plant functional strategies using a multidimensional approach. Using such an approach has enabled us to shine a new light on species functionality within the Cerrado, challenging the usual functional group associations defined by phenology and life form.