Phenological cycles in the Pantanal woody communities: Responses to climate and soil moisture seasonality

The distinct synchronies and varied functions of plant species assemblies have led to some communities exhibiting peak flowering activity during both the dry season and wet phase, which is related to the presence of species with multiple reproductive strategies within the same community. Species associated with ASDF, such as T. catigua and A. cuspa, have individ- uals who flower in opposite hydrological phases in the rainy and dry seasons, respectively, which could be influenced by their distinct floristic affinities with neighboring ecosystems (e.g., Atlantic forest, Seasonal forest, and Cerrado) [75]. In general, the studied species popula- tions exhibited low-intensity and brief-to-intermediate flowering events [101], which aligns with the findings of other studies [22,99,102,103]. Damasceno-Junior (2020) noted that the flowering phenophase in the Pantanal is generally weakly seasonal (111), gaining significance in certain species groups associated with dispersal strategies [104]. The communities with greater synchronisms were those dominated by a few species (SHB, IS, and MF) or that occurred on flood-free ground on ridges or ancient levees (i.e., LSDF) [46]. Species employing seed or fruit dispersal during periods of high river levels, such as V. divergens and M. guianen- sis, presented peak flowering activity at the very end of the wet season (June), when flooding receded, resulting in fruiting in January. T. aurea and H. heptaphyllus, known for their massive and synchronized flowering, produce numerous anemochoric seeds that respond clearly to

variations in climate [51] The flowering phenophase in SHB occurs simultaneously with fruit- ing during the dry season. Synchronized reproductive behavior is influenced by high tempera- tures and consecutive months of exposure to solar radiation, indicating the high tolerance of savanna shrub species to extreme heat and drought [105]. In addition to climatic influence, endogenous forces play a role in explaining low and asyn- chronous flowering within species populations [106,107], as observed in both CS and ASDF, respectively. Endogenous factors, which are crucial for flower production, can manifest through spatial variations in the chemical attributes of the soil [106] and as a life strategy to avoid competition for visitors and pollinators [107]. Notably, the physicochemical aspects of the soil, such as the phosphorus content [108], vary among the distinct vegetation types in the Pantanal [109]. In general, the seasonal synchrony of fruiting among the different species was weak (con- centration coefficient, rc < 0.50) across the various vegetation communities. This phenome- non may arise when coexisting plant species exhibit diverse life cycle modes, resulting in the decoupling of phenophases from climatic seasonality [69,108,110]. At the individual level, the presence of fruits at reduced frequency and intensity (Fournier intensity < 6%) underscores the potential influence of environmentally heterogeneous ecosystems and resource availability on heightened species competition and reduced energy investment in reproduction [111,112].

This divergence in reproductive schedules establishes a resource availability timetable for fauna, promoting complementarity and potentially sustaining biodiversity throughout a longer part of the year [113]. In most of the monitored communities, species populations consistently produce fruits year- round, although at low frequency and intensity, which can be advantageous for frugivorous ani- mals (e.g., Tapirus terrestris and Ramphastos toco), allowing them to align their fruit consump- tion with the phenology of various fruiting species [114–116]. Conversely, communities characterized by a strong dominance of a few species, notably SHB and MF, presented pro- nounced seasonality in terms of fruit production influenced by increasing temperatures during the austral wetter summer. This finding underscores the significant influence of the flowering season on subsequent fruit dispersal in these environments [104,117]. While leaf development is typically more responsive to changes in water availability than flowering or fruit production is [83], access to groundwater may allow fruiting to occur independently of the usual moisture fluctuations [118]. Additionally, species’ phylogenetic signals can further decouple reproductive PLOS ONE Phenological cycles in the Pantanal woody communities PLOS ONE | https://doi.org/10.1371/journal.pone.0316011 February 7, 2025 20 / 30