Testing for criticality in ecosystem dynamics: the case of Amazonian rainforest and savanna fire

• Published in: Ecology letters Vol. 13; no. 7; pp. 793 - 802
• Main Authors: Pueyo, Salvador, de Alencastro Graça, Paulo Maurício Lima, Barbosa, Reinaldo Imbrozio, Cots, Ricard, Cardona, Eva, Fearnside, Philip M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.07.2010; Blackwell Publishing Ltd; Blackwell
• Subjects: Abrupt shift; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Climate change; Climatology. Bioclimatology. Climate change; Drought; Earth, ocean, space; Ecology; Ecosystem; Ecosystem dynamics; Exact sciences and technology; External geophysics; Extreme drought; Fires; Forest & brush fires; fractal; Fundamental and applied biological sciences. Psychology; global warming; Grasslands; macroecology; Meteorology; Models, Theoretical; percolation; power-law distribution; rain forests; Rainforests; Savannahs; savannas; self-organized criticality; South America; Synecology; Terrestrial ecosystems; Tropical Climate; tropical rain forests; tropical rainforest; tropical savanna; wildfire; wildfires; South America; Amazon Basin; power-law distribution; tropical zone; Tropical rain forest; self-organized criticality; dynamics; environment impact; tropical rainforest; fires; percolation; Abrupt shift; global warming; global change; wildfire; ecosystems; savanna; Macroecology; warming; fractal; Vegetation fire; tropical savanna; Power law; climate change
• ISSN: 1461-023X; 1461-0248; 1461-0248
• DOI: 10.1111/j.1461-0248.2010.01497.x

Ecology Letters (2010) 13: 793-802 We test for two critical phenomena in Amazonian ecosystems: self-organized criticality (SOC) and critical transitions. SOC is often presented in the complex systems literature as a general explanation for scale invariance in nature. In particular, this mechanism is claimed to underlie the macroscopic structure and dynamics of terrestrial ecosystems. These would be inextricably linked to the action of fire, which is conceived as an endogenous ecological process. We show that Amazonian savanna fires display the scale-invariant features characteristic of SOC but do not display SOC. The same is true in Amazonian rainforests subject to moderate drought. These findings prove that there are other causes of scale invariance in ecosystems. In contrast, we do find evidence of a critical transition to a megafire regime under extreme drought in rainforests; this phenomenon is likely to determine the time scale of a possible loss of Amazonian rainforest caused by climate change.