Produção de Serapilheira e Retranslocação de Nutrientes Foliares em Grupos Funcionais Arbóreos em Floresta de Terra Firme na Amazônia Central

Abstract

The deposition of litter is crucial for forest maintenance, as it represents the primary mechanism for nutrient return to the soil. This process plays a fundamental role in nutrient cycling in tropical forests, especially in the Central Amazon, where soils are nutritionally poor. As tree species in these forests strive to adapt and conserve scarce resources, the retranslocation of foliar nutrients emerges as an essential conservation mechanism. However, little is known about the factors influencing these processes and how trees in tropical forests respond to anthropogenic interventions or climate change. The objective of this dissertation was to quantify the seasonal production of leaf litter and the retranslocation of foliar nutrients in pioneer and non-pioneer tree species in an experimentally managed forest in the Central Amazon. The study was conducted in one of the BIONTE treatments from May 2022 to April 2023. Bi-weekly data on leaf litter deposition were collected from nine pioneer trees and nine non-pioneer trees. Samples of fresh (green) and senescent leaves from the same trees were analyzed for nutrient content, and the nutrient retranslocation efficiency of these functional groups was calculated. The most retranslocated nutrients were phosphorus (P) and potassium (K). The efficiency of P was 71.08 ± 2.75% for pioneers and 63.24 ± 7.32% for non-pioneers (95% CI). For K, pioneers showed 69.31 ± 5.66%, while non-pioneers registered 62.22 ± 8.33%. Depending on the nutrient, some processes may affect retranslocation more than others. The average annual production of total litter for this period was 8.6 ± 0.5 Mg ha-1 year-1. The monthly deposition for pioneers was 0.45 ± 0.07 g m-2 day-1, and for non-pioneers, it was 0.08 ± 0.03 g m-2 day-1 (95% CI). Nutrient flows were higher in pioneers for all elements, with nitrogen (N) standing out at 121.49 ± 32.09 kg/month. These results highlight that, amid interventions, pioneer species significantly contribute to restoring forest productivity, whether through litter deposition, nutrient flux, or foliar nutrient retranslocation.