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

aurea, a typical Cerrado species, tolerate flood stress by preventing root system death and leaf abscission [86]. Total or partial deciduousness, combined with strong stomatal regulation, appears to be a common water regulation strategy for both dry and flood season species in the Cerrado and flooded forests [23,81]. L. parvifolius, commonly found in MF, efficiently main- tains water use during the dry season but exhibits stomatal limitations in response to seasonal flooding [81], with more than 50% of its leaves lost during this period. The two peaks in leaf fall intensity during both dry and wet periods have significant implications for carbon cycle dynamics within these communities, as the decomposition of senescing leaves contributes to the release of carbon from the soil back into the atmosphere [87]. Many species identified in the studied floodplain were found across multiple communities, exhibiting intraspecific variation in vegetative activity. This variation is attributed to distinct ontogenetic stages within populations, small-scale environmental heterogeneity, and genetic structure [73,88,89]. Water table depth and fluctuations are considered to modulate plasticity in maximum root depth among species occurring in both the Cerrado and Pantanal. For example, the root depth of T. aurea and C. americana in the Pantanal was found to be half that of their counterparts in the Cerrado [73]. Shallow root systems during waterlogging may lead to reduced transpiration and tree growth, triggering additional leaf-shedding events, a phe-

nomenon also observed in Amazon floodplain trees. Some individuals of A. discolor were observed to partially and shortly shed leaves during the flood season, reinforcing the idea that leaf shedding can occur in evergreen species in the aquatic phase [11,83]. Phenotypic plasticity allows species populations to adapt to various positions along the soil hydrological gradient, facilitating their persistence in savannas and forests [90]. Even without clear evidence that surface soil moisture seasonality affects leaf shedding, water table dynamics may influence the ability of leaf fall to adjust during periods of low atmo- spheric and soil moisture. We speculate that the lack of a significant correlation between soil moisture and leaf shedding intensity may stem from habitat-specific interactions among soil physical attributes, rainfall, and flood dynamics that disrupt the alignment between rainfall timing and soil moisture seasonality [13,91]. These dynamics can lead to prolonged water shortages, reducing the seasonality of leaf shedding, as observed in Lowland Seasonally Dry Forests (LSDF). In these seasonal forests, which are typically found in areas of high soil fertility along flood-free riverbanks and relict dunes [91], the relatively high number of evergreen spe- cies suggests that some trees are buffered against seasonal drought due to access to deep soil layers (2–6 m) or storage in succulent tree trunks [92,93]. In contrast, the floristically similar ASDF may experience significant leaf fall seasonality due to stronger connections between

rainfall, soil surface moisture, and groundwater fluctuations at lower elevations near the river’s watercourse [91]. Access to groundwater reserves is thus a critical factor for the resilience of both forest and savanna ecosystems [73,94]. Reproductive phenology cycle The intricate interaction between climate signals and the reproductive patterns of plant com- munities in diverse ecosystems, particularly in the Pantanal region, highlights the critical role of phenological events in shaping ecological dynamics [22,95–98]. The studied communities exhibited significant seasonal flowering, with notable exceptions in the ASDF. In essence, these results from the Pantanal underscore the crucial role of lower minimum and maximum temperatures, rainfall, and evapotranspiration in triggering flowering events, highlighting dry- ing and cooler conditions as a period of peak flower production [99]. Climatic antecedence emerges as a key determinant of the rhythms of the phenophase and is influenced by the feed- back between hydroclimatic conditions and energy flux with land cover type [100]. PLOS ONE Phenological cycles in the Pantanal woody communities PLOS ONE | https://doi.org/10.1371/journal.pone.0316011 February 7, 2025 19 / 30