491

ID:

Background:

Compounding disturbances events associated with drought, fire, windstorms, and forest fragmentation have interacted to degrade tropical forests. As climate and land-use change, these events are expected to become more frequent, widespread, and intense. An important scientific practical question is whether tropical forests' recovery will outpace forest degradation associated with novel disturbance regimes. Despite a high resilience, tropical forests may not recover when disturbances are too intense and severe.



Objective:

To provide a synthesis of multi‐year measurements of vegetation dynamics and function (fluxes of CO2 and H2O) in forests recovering from 12 years of controlled burns, followed by two wind disturbance events. The study’s hypothesis was that the experimentally burned areas could differences in forest structure and functioning to decrease over time between burned and unburned areas, although slower along the forest edges and in the treatment burned every three years, where fire and wind damage were more severe.



Methods:

The experimental study area was in Mato Grosso state, 30 km north of the southern boundary of the Amazon rainforest in Brazil and consisted of three 50‐ha plots burned annually, triennially, or not at all from 2004 to 2010 (with exception of 2008). In burned plots areas, fire lines were ignited using drip torches along transects spaced 50 m apart during the peak of dry season, in between July and early September. To evaluate post-fire forest recovery of CO2 and H2O fluxes, we used tow eddy covariance systems, one located in an unburned forest and another in the burned plots. We also conducted pre‐ and post-fire inventories across the three treatment plots, and measured canopy dynamics different methods.



Results:

During the first seven years of post-fire recovery, tree survivorship and biomass continued to decline and species composition to change, especially along forest edges, where the disturbances were more severe. However, more recent vegetation regrowth triggered partial recovery of vegetation structure and fluxes due to higher light-use efficiency and water by plants growing in the burned plots, compared to the control.



Implications/Conclusions

While the effects of interacting compounding disturbances events on biomass and species composition can persist over many years, a rapid recovery of carbon and water fluxes can help stabilize some local climatic conditions.

Keywords:

Amazonia, wildfires, forest, tree mortality, carbon emissions, forest edge, disturbance

Paulo Brando, Divino Vicente Silvério, Susan Trumbore, Leonardo Maracahipes-Santos, Leandro Maracahipes, Marcia Macedo, Maria Uribe, Lucas Paolucci

Presentation within symposium:

S-14 Seeing Through the Smoke – fire as a catalyst of Amazonian tipping points

Ecological Insights from a 12-year Burn Experiment in a Transitional Amazonian Forest

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