Tropical savannas and grasslands were long regarded as convenient "empty" territories: it is easier to plough them up or graze them than to understand how they are put together. A thematic collection of articles in Annals of Botany calls this view into question. It is titled "Advances in Cerrado and tropical grassland plant biology – diversity, functioning, resilience and conservation" and is devoted to the diversity, functioning, resilience and protection of these ecosystems. Together the articles show that behind the apparent simplicity of open landscapes lies a complex system of survival that science is only beginning to truly decipher.
The cerrado, or Brazilian savanna, is the second-largest biogeographic domain of South America, consisting almost entirely of open ecosystems. In terms of plant diversity it is the richest tropical savanna in the world, but also one of the most vulnerable: over the past forty years about 40 % of its territory has burned at least once, and almost half of its original vegetation has already been lost. Plants here have developed strategies for living under conditions of fire, nutrient-poor soils and seasonal drought. A characteristic example is the ratio of belowground to aboveground biomass: in grasslands and savannas there is relatively more root than shoot, and this is an adaptation to a shortage of water and nutrients. That is why the cerrado is sometimes called an "inverted forest".
New experiments help to understand when plants begin to survive fires. For herbaceous cerrado species, survival after fire already exceeds 50 % by the third month of life, rises above 70 % at later stages, and in plants older than a year approaches 100 %. At the same time, a fire before the start of the dry season noticeably slows recovery. In other words, resilience forms gradually, and the timing of burning matters.
Underground organs play a key role. A review of fire adaptations in cerrado plants shows that meristems, that is, growth tissues, in many species are protected precisely underground, while above ground they are covered by thick bark. After a fire the herbaceous layer quickly flowers and produces seeds that enter the soil seed bank and then return to the community. Picture an old oak in a park: its crown may be damaged by a storm, but the roots and dormant buds remain alive and produce new shoots. The surface vegetation in the cerrado can likewise disappear, for example when land is ploughed, but underground reserves allow the community to recover.
The practical value of this knowledge lies in the fact that it points to where to look for footholds for restoration. Where traditional conservation methods work poorly, underground mechanisms of regeneration can become the basis for rehabilitation measures: for example, choosing the timing of burning and selecting species for planting. However, it is important to remember that information on underground plant traits is still insufficient: according to the database, most records relate to leaves and the general appearance of the plant, while root and reproductive traits are represented more weakly.
The Cerrado Plant Traits (CPT) database is intended to address this problem. It is an open project that consolidates and standardises data on the functional traits of plants of the Brazilian cerrado. It currently contains 113 859 records on the traits of 2134 taxonomically verified species from 150 families, collected from 148 datasets. The records cover both conserved, degraded and restored territories. Thanks to this, scientists can test how plant traits change along gradients of fire, soils and climate, and compare communities at the boundary between forest and savanna. Such a tool does not predict the future by itself, but it provides a basis for testing hypotheses about which communities will prove more resilient, and for conservation and restoration plans.
To better protect these ecosystems, it is worth supporting research on the underground organs of plants and adding to trait databases, especially with regard to roots and seeds, and sharing these data with restoration practitioners.
