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

were fruiting, and the other during the period of increasing soil moisture in January (9.7%), with fruits observed in E. florida and G. americana. In the flood-free LSDF, the Rayleigh test (rc = 0.36, p<0.001) indicated that the mean date of the fruiting phenophase was in January (Fig 5A), which coincided with the rainy season and the period was the highest soil moisture in this community (49%, Fig 2). The slight difference between the two peaks of Fournier intensity during rainy January (1.7%) and dry September (1.4%) (Fig 5B) did not reflect the increased proportion of active species and individuals. In contrast, the frequencies of active species (20%) (Fig 5A) and individuals (5%) in January were nearly double those reported in September (9.8% and 2.8%, respectively). Anadenanthera colu- brina, Attalea phalerata, Myrcia tomentosa, and Tabebuia roseoalba were among the fruiting species. The weak seasonality in fruiting patterns in the ASDF and PS groups suggests that fruiting events were not significantly concentrated at any particular time of the year (Fig 5A). However, in the ASDF, December was the month with the highest relative activity among the species (11%) and individuals (9%) (Fig 5B). Additionally, with the highest fruiting intensity occurring in December (9%), the importance of the rainy season for fruiting in this alluvial forest is evi- dent. The species that entered the phenophase in December were D. duckei, E. anguifugum, E. florida, M. guianensis, O. suaveolens, and V. cymosa. A unique feature of the fruiting cycle in

PS is the relatively high concentration of species’ fruiting activity during April and May (Fig 5A), marking the abrupt transition from a phase with soil moisture below 20% (March) to an inundated phase (April) (Fig 2). During these months, M. hirtum and Byrsonima cydoniifolia were observed fruiting. Many species populations in this community, including M. hirtum and H. heptaphyllus, begin fruiting during the low precipitation season from July to September and continue throughout the rainy season. Influence of climate and soil moisture on Fournier’s percent index of intensity Leaf fall. The intensity of leaf fall events was correlated with the meteorological variables in all the communities except LSDF (Fig 6). Among all the variables, evapotranspiration had the strongest correlation with leaf fall. The trends of decreasing evapotranspiration, precipita- tion, and temperatures, coupled with increasing insolation toward the austral dry winter, trig- gered leaf fall in most of the observed communities. A decrease in the mean (ranging from 25˚C to 23˚C) and minimum (ranging from 20˚C to 17˚C) temperatures was associated with increasing Fournier intensity of leaf shedding for most communities (Fig 6B). The negative influence of temperature on leaf drop occurred within two months before the date of maxi- mum leaf fall, indicating that cold fronts enter the region during austral winter. The decrease in minimum temperature from April (23˚C) to July (17˚C), during the period when rainfall is

decreasing and flooding is receding, was correlated with an increase in leaf fall in the PS (r0 = -0.85, p = 0.0002), IS (r0 = -0.81, p = 0.001), MF (r0 = - 0.73, p = 0.005), and ASDF (r0 = -0.71, p = 0.01). Even for other communities with weak species synchrony in terms of leaf activity, such as the CS communities, decreasing trends in minimum temperature were related to increased intensity of leaf fall (r0 = -0.80, p = 0.001). The IS (r1 = -0.60, p = 0.03) and PS (r1 = -0.60, p = 0.03) were also influenced by lower minimum temperatures one month before the phenological event. The mean (r0 = 0.62, p = 0.02) and maximum (r0 = 0.75, p = 0.003) tem- peratures were the only climatic variables influencing the intensity of leaf fall in SHB. The months with maximum temperatures from August to October (36 − 38˚C) corresponded with the maximum leaf fall intensity (43 − 50%). PLOS ONE Phenological cycles in the Pantanal woody communities PLOS ONE | https://doi.org/10.1371/journal.pone.0316011 February 7, 2025 15 / 30