Trees

Trees (and other plants) form the base of the Amazon rainforest ecosystem by providing biomass that can be consumed by other organisms and complex multi-dimensional habitat that can be exploited by other organisms. The vertical structure of the rainforest consists of the ground layer, shrub layer, understory, canopy and overstory, oftentimes extending 40m (130 ft) or higher [1]. In undisturbed areas, leaves densely pack the canopy, allowing little sunlight to reach the forest floor. Within a single hectare of rainforest in Manu, Peru, more than 220 species of trees may be present, whereas in Europe and North America, a hectare of temperate woodland there may only be 20 species of trees present [2]. Though the Amazon rainforest contains roughly 16,000 tree species, it is generally dominated by far fewer species.

The Brazil nut tree (Bertholletia excelsa) is a dominant species found throughout the Amazon rainforest lowlands. These trees grow to the top of the canopy layer, sometimes growing nearly 50m (160ft) tall [3]. The Brazil nut tree flowers and produces nuts contained within a solid pod that only a small mammal, the agouti, is able to open. The nuts are commercially harvested, supporting a lucrative industry. The Brazil nut tree illustrates the connectedness of organisms in the Amazon – it depends on bees for pollination (which depend on orchids) and the agouti for seed dispersal. Losing a single species in the Amazon could have reverberating effects throughout the entire ecosystem.

The roughly three billion trees in the Amazon photosynthesize using water (H2O) and carbon dioxide (CO2) in the presence of sunlight to maintain and increase biomass. The resulting carbon compounds are then stored in their leaves, trunks, roots, and soil in the form of dead and decomposing material. The trees in the Amazon sequester or store 25% of the total CO2 stored in the terrestrial environment [4]. Per a recent study, however, it appears that the carbon storage in the Amazon has declined by 30% since the 1990’s due to higher tree mortality [5].

Photo by Artist for the Amazon Adrian Tejedor.

Looking forward, rising temperatures due to climate change could cause moisture levels in the Amazon to decline, increasing the prevalence of drought and forest fires, ultimately leading to dieback on a massive scale. To prevent such an ecological catastrophe, actions need to be taken to limit further deforestation and habitat degradation, and measures to mitigate the impacts of climate change need to be delineated and enforced.

The biggest tree of the Amazon rainforest is the Kapok Tree. It can grow to 200 feet tall and the trunk can be 10 or 11 feet in diameter.

There are more trees in the Amazon than stars in the Milky Way galaxy.

References
  1.    http://rainforests.mongabay.com/amazon/rainforest_ecology.html
  2.     World Wildlife Fund. (2010). Amazon Alive: A Decade of Discovery 1999-2009.
  3.    http://www.rainforest-alliance.org/kids/species-profiles/brazil-nut-tree
  4.     Pan, Y. et al. (2011). A large and persistent carbon sink in the world’s forests. Science333 (6045), 988-993.
  5.     Brienen, R. J. W. et al. (2015). Long-term decline of the Amazon carbon sink. Nature, 519, 344-348.

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