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Grasses fuel most fires on Earth and strongly influence local fire behaviour through traits that determine how flammable they are. Therefore, grass communities that differ in their species and trait compositions give rise to significant spatial variation in savanna fire regimes across the world, which cannot be otherwise explained. Likewise, fire regimes are continuously modified by alterations to savanna grass community traits, through species introductions and climatic changes. However, current representation of grassy fuels in global fire models misses important variation and therefore limits predictive power. The inclusion of grass trait diversity in models, using remotely sensed trait proxies, for example, will greatly improve our ability to understand and project savanna fires and their roles in the Earth system. Most fires on Earth occur in savannas, but vary considerably in their extent, frequency, and intensity. These patterns cannot fully be explained by climate or land management. An important 'missing-piece' in explaining the variation in savanna fire regimes is the diversity of grasses that fuel fires and whose traits strongly influence fire behaviour. The major differences in savanna fire behaviour across continents may lie in the contrasting species and trait assemblages in savanna grass communities. Fire regimes change significantly when savanna grass communities or traits are altered by the introduction of invasive species and climatic changes. Improved representation of grass trait diversity in fire models will be essential for reliable forecasts of the behaviour and impacts of the majority of fires on Earth. [ABSTRACT FROM AUTHOR]

The aim of this study was to understand how communities of adult and juvenile (seedlings and saplings) woody plants were impacted by fire and the 2014–2016 El Niño drought in Kruger National Park, South Africa. We used a landscape‐scale fire experiment spanning 2013–2019 in a semi‐arid savanna in the central west of Kruger National Park (mean annual precipitation, 543 mm). Adult and juvenile woody species composition were recorded during and after the drought in 40 plots that experienced a mix of no fire, moderate fire, and frequent fire treatments. Using multivariate modeling, we related community composition in juvenile and adult woody plants to year of sampling and the experimental fire treatments. Post‐drought, there was significant adult woody plant top‐kill, especially in dominant species Dichrostachys cinerea (81% reduction in abundance), Acacia nigrescens (30%), and Combretum apiculatum (19%), but there was no significant change in adult species richness. Two years post‐drought, abundance of all juveniles decreased by 35%, and species richness increased in juveniles in both the frequent fire (7%) and no fire treatments (32%). Counter‐intuitively, the El Niño drought increased species richness of the woody plant community due to the recruitment of new species as juveniles, a potential lasting impact on diversity, and where different fire regimes were associated with differences in community composition. Drought events in semi‐arid savannas could drive temporal dynamics in species richness and composition in previously unrecognized ways. [ABSTRACT FROM AUTHOR]

Hydraulic failure caused by severe drought contributes to aboveground dieback and whole‐plant death. The extent to which dieback or whole‐plant death can be predicted by plant hydraulic traits has rarely been tested among species with different leaf habits and/or growth forms. We investigated 19 hydraulic traits in 40 woody species in a tropical savanna and their potential correlations with drought response during an extreme drought event during the El Niño–Southern Oscillation in 2015. Plant hydraulic trait variation was partitioned substantially by leaf habit but not growth form along a trade‐off axis between traits that support drought tolerance versus avoidance. Semi‐deciduous species and shrubs had the highest branch dieback and top‐kill (complete aboveground death) among the leaf habits or growth forms. Dieback and top‐kill were well explained by combining hydraulic traits with leaf habit and growth form, suggesting integrating life history traits with hydraulic traits will yield better predictions. [ABSTRACT FROM AUTHOR]

Newly germinated seedlings are vulnerable to biomass removal but usually have at least 6 months to grow before they are exposed to dry‐season fires, a major disturbance in savannas. In contrast, plants are exposed to browsers from the time they germinate, making browsing potentially a very powerful bottleneck for establishing seedlings.Here we assess the resilience of seedlings of 10 savanna tree species to topkill during the first 6 months of growth. Newly germinated seeds from four dominant African genera from across the rainfall gradient were planted in a common garden experiment at the Wits Rural Facility and clipped at 1 cm when they were ~2, 3, 4 and 5 months old. Survival, growth and key plant traits were monitored for the following 2.5 years.Seedlings from environments with high herbivory pressure survived topkill at a younger age than those from low‐herbivore environments, and more palatable genera had higher herbivore tolerance. Most individuals that survived were able to recover lost biomass within 12 months, but the clipping treatment affected root mass fraction and branching patterns.Synthesis. The impact of early browsing as a demographic bottleneck can be predicted by integrating information on the probability of being browsed and the probability of surviving a browse event. Establishment limitation through early browsing is an under‐recognized constraint on savanna tree species distributions. [ABSTRACT FROM AUTHOR]

The article asserts that the plan of 130 nations at the 2021 United Nations Climate Change Conference (COP26) to halt global deforestation by 2030 needs to be expanded to include savannas, which cover an area of 20 million square kilometers and are regarded as more important carbon sinks than forests.