The Amazon Basin is the largest hydrographic basin in the world, also featuring one of
the largest flooded areas in the globe. Floodplain forests comprise a specific type of
floodplain within the Amazon, characterized by being areas of forests periodically
flooded by whitewater rivers. In these ecosystems, studies of biomass deposition
dynamics are extremely important, as it defines the future trajectory of the net carbon
balance of the ecosystem and is also the main route of nutrient transfer from vegetation
to soil. The present study aims to quantify biomass production via litter, investigating
patterns of seasonal occurrence, as well as its nutritional composition. For this, 12
collectors were installed in 4 plains of floodplain forests and monthly litter collections
were carried out over 19 months in a floodplain forest in Arapixuna District, located in
the municipality of Santarém-PA. The results showed a high litter production in these
forests, with a monthly average of 1,357.8 kg ha -1 and a total production of 1,4487.7 kg
ha -1 for the year 2018. A higher production pattern was observed in the flood and lower
in the dry season, with the leaves being the most produced fraction, with 57% of the litter
biomass composition. Biomass production was positively correlated with some physical
factors such as Amazon River flow and water level. There was no seasonal pattern of
nutrient concentration in litter, however nutrient analysis showed that calcium (Ca) is the
highest concentration in litter with an average of 426 kg ha -1, while phosphorus (P ) has
the lowest concentration, with an average of 55 kg ha -1. As for micronutrients, Fe was
the most outstanding element (18.47 kg ha -1), while the lowest micronutrient was Zn
with an average of 6.69 kg ha -1. These results indicate that environmental factors
influence the dynamics of litter production in floodplain areas, and it plays a crucial role
in nutrient cycling within this medium. The deposition of material via litter, combined
with the flood pulse, brings with it a very important nutrient load for the maintenance of
local soils.
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