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

cycles from water availability, leading phylogenetically related species to exhibit similar pheno- logical periods, irrespective of moisture conditions or seasonal changes [118]. These fruiting patterns reveal a nuanced strategy mediated by dispersal syndromes and phylogenetic signals in plant phenology [22,119]. While abiotically dispersed species (mostly wind-dispersed) release seeds mainly in the dry season, the wet-season peak is driven almost entirely by biotically dispersed species [22,120]. For example, T. catigua and A. discolor tend to grow in alluvial forests and flood-prone areas [75] during the wettest months (December-Jan- uary; ~24% soil moisture). On the other hand, fructification of species found in CS, such as A. fraxinifolium and A. colubrina, occurred during the driest months (August-September; < 14% soil moisture). The relationships between plant communities and seed dispersers, which include mammals (e.g., bats and primates), birds, and fishes, underscore the critical role of flood pulses in shap- ing patterns of seed deposition. The intricate balance required for ecosystem health and regen- eration and the role of dispersal strategies within each community assembly [108] provide valuable insights into why the onset and end of the reproductive period may not fully coincide across communities. Frugivory by fish and hydrochory are relevant mechanisms for determin- ing lateral dispersal and seed deposition patterns across floodplain communities [121,122]. For example, M. guianensis and O. suaveolens, which undergo fruiting during the rainy season in

the MF and ASDF, serve as examples of species dispersed by fish [96]. Their involvement plays a vital role in the regeneration of forest ecosystems [114]. Concluding remarks: Informing conservation and management initiatives The unique hydrological response of the Pantanal to the climatic cycle sets it apart from other nonflooded savanna vegetation [17,123]. This response involves the intricate interplay between phenological dynamism and alternating drought and wet phases [11,25]. This study revealed the existence of interspecific synchrony in vegetative and reproductive phenology within savanna and forest communities. Differences in seasonal phenological patterns among com- munities were predominantly observed in flowering, with communities with intensities con- centrated from the very end of the wet season (when flooding is receding) to the dry season, differing from those with flowering events more scattered throughout the year (Figs 5A and S1). Interspecific synchronism and seasonal responses in leaf fall were triggered by climate sea- sonality in terms of rainfall, temperature, and evapotranspiration, while the climate signals for flowering and fruiting events were predominantly detected for communities with high domi- nance for few species. The difference in assemblage activity times observed in other Pantanal regions [108] might result from the complex interplay between plant evolution and the current selective habitat fil- ters [51,124,125], resulting in unique strategies for coping with periods of soil or atmospheric

water stress concomitant with high air temperatures [126,127]. The broad array of phenologi- cal responses, which might confer stability to interannual climate fluctuations at the commu- nity level, is further supported by the ability of some species to acclimate to increasing drought or wet conditions [128] and occupy distinct zones of the soil hydrological gradient in the Pan- tanal [17]. Nevertheless, in the context of climate change, the northern Pantanal has experi- enced a shift toward aridity, marked by a 13% increase in the number of days without rain compared with that in the last 60 years. Additionally, there was a 16% reduction in water mass during the drought season compared with that observed a decade ago [129]. This approach tests tolerance limits and alters the dynamics of competitive strategies among shrubs, palms, lianas, and trees while vying for resources in challenging environments. PLOS ONE Phenological cycles in the Pantanal woody communities PLOS ONE | https://doi.org/10.1371/journal.pone.0316011 February 7, 2025 21 / 30