Litter stock, litterfall and nutrients in the Amazonia: defining patterns from last 40 years of scientific research

Nutrient cycling, guaranteed by the decomposition of litter, stands out as an essential process for maintaining Amazonian ecosystems. Studies on the litter layer on the soil surface are indispensable, primarily because they help provide information about functional and structural aspects of the ecosystem. Therefore, to define parameters related to the storage and production of litter and nutrients in Amazonia, we conducted a qualitative and quantitative analysis of articles in academic publications developed in Amazonia in the last 40 years (1980- 2019). We identified 83 articles, with the majority (85.39%) developed in Brazil. We found that 67% of these studies were related to the litterfall method and only 11.24% were related to both collection methods (litter stock and litterfall). The litter stock ranged from 4.94 ± 2.07 Mg ha-1 to 11.05 ± 4.67 Mg ha-1 for Agroforestry Systems (AFS) and Mixed Plantation (MIP), respectively. While litterfall ranged from 2.09 ± 1.14 Mg ha-1 year-1 to 9.01 ± 6.09 Mg ha-1 year-1 for pasture ecosystems (PAS) and AFS. The litter nutrients in Amazonia follow the following decreasing order: N>Ca>K>Mg>P. Our results indicate the need for more attention and investment in Amazonian forest research, so that more studies on the subject may be developed, especially those focusing on ecological restoration.