EGU22-10939, updated on 28 Mar 2022
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effects of soil fertilization on aboveground biomass in an old-growth forest in Central Amazon

Bárbara Brum1, Carlos A. Quesada1, Rafael Assis3, Juliana Schietti1,5, Izabela Aleixo1, Raffaello di Ponzio1,6, Iain Hartley4, Kelly Andersen4,7,8, Hellen F. Cunha1, Laynara Lugli1,4, Nathielly Martins1, Renata Almeida2, Maria Pires1, Nívia Pinheiro2, Anna C. Moraes1, José L. Camargo2, Gyovanni Ribeiro1, Bruno Takeshi1, Lara Siebert1, and Felipe Andrade1
Bárbara Brum et al.
  • 1Coordination of Environmental Dynamics, National Institute of Amazonian Research, Manaus-AM, Brazil
  • 2Biological Dynamics of Forest Fragment Project, National Institute of Amazonian Research, Manaus-AM, Brazil
  • 3Natural History Museum, University of Oslo, Norway
  • 4Geography, College of Life and Environmental Sciences, University of Exeter,United Kingdom
  • 5Institute of Biological Sciences , Federal University of Amazonas, Manaus-AM, Brazil
  • 6Federal University of Minas Gerais, Belo Horizonte-MG, Brazil
  • 7Asian School of the Environment, Nanyang Technological University, Singapore
  • 8School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom

The Amazon covers an extensive area of tropical rainforest that directly affects global water and Carbon cycles. The biomass stored in this forest is a result of the dynamic balance between rates of mass gain due to productivity, and losses due to respiration and mortality. In general, these forests concentrate about 70-80% of biomass in the aboveground part, and the regional variation of AGB (aboveground biomass) can be explained by the compositional, structural, climatic and by differences in soil propriety and fertility between East-West gradient in the Amazon basin. This gradient drives a large set of variations in tree growth and mortality, resulting in differences on the forest structure and dynamics. In this context, direct manipulation of nutrients in soils is a powerful tool to investigate which elements limit tree growth and forest productivity. While nitrogen (N) is accumulated along soil development and age, the availability of rock-derived phosphorus (P) and cations may limit the ecosystems' functioning, including the potential increase in the productivity in response to elevation on CO2 concentrations in the atmosphere. To understand these patterns, a long-term, large-scale soil fertilization experiment in Amazonian forests (AFEX) was implemented in the Central Amazon. In 2017, 32 permanent plots were installed in areas of old-growth continuous forest belonging to the Biological Dynamics of Forest Fragments Project (PDBFF), in a full factorial design, with four blocks chosen at random, where 8 plots (each with a size of 50x50 m) were installed with different fertilization treatments for each block. The treatments are: P, N, cations, Control (no fertilization), N+P, N+cations, P+cations and N+P+cations. To estimate the effects of soil fertilization on AGB, we calculated the difference between biomass before and after four years of fertilization (2017 to 2021), using allometric equations performed data from diameter about 5,000 individuals (DAB ≥ 10 cm) measured annually and wood density. We analyzed the data with two different approaches, at the community and at genus level, considering three most abundant genera: Eschweilera, Pouteria and Protium. At community level, our results showed only non-significant trends between AGB in plots where N, P and cations were added. At genus level, we observed that Eschweilera and Protium had a negative relationship to N and Pouteria had a positive trend.  Conversely, only Protium increased AGB with P addition.  Pouteria and Protium was negatively affected by cations, while Eschweilera showed no response. These results indicate that, although overall positive or negative trends in biomass increment appear at the community level, the highly diverse forest studied does not have a homogeneous response to nutrient addition, and that each taxonomic group could potentially be limited by different nutrients. In the long term, we expect that these patterns may change the forest structure, dynamics and composition and, consequently, the stocks of biomass, impacting the functionality of these forests. These results improve our understanding of the role of nutrients affecting forest biomass, and may reduce uncertainties in vegetation dynamics models and predictions on environmental changes.

How to cite: Brum, B., Quesada, C. A., Assis, R., Schietti, J., Aleixo, I., di Ponzio, R., Hartley, I., Andersen, K., Cunha, H. F., Lugli, L., Martins, N., Almeida, R., Pires, M., Pinheiro, N., Moraes, A. C., Camargo, J. L., Ribeiro, G., Takeshi, B., Siebert, L., and Andrade, F.: Effects of soil fertilization on aboveground biomass in an old-growth forest in Central Amazon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10939,, 2022.