Do past fires explain current carbon dynamics of Amazonian forests?

Lead Research Organisation: University of Exeter
Department Name: Geography

Abstract

Amazon forests process and store large quantities of carbon in vegetation and soils. These forests, assumed to be mostly 'old-growth' and fire-free are exhibiting a remarkable feature-they are gaining the equivalent mass of a small car every year in aboveground biomass per hectare of forest (0.89 Mg/ha/yr). These gains are attributed to increasing atmospheric CO2, which has a fertilization effect on tree growth. However, fire in these 'old-growth' forests may be more recent than expected (in the last few centuries), and regrowth from fire together with soil charcoal-which has a fertility effect-may be contributing together with CO2 fertilisation to the observed increases in biomass in these apparently mature forests. Current understanding of drivers of these increases is limited by, (i) an unknown fire history of plots used to monitor change, and (ii) lack of information of how resource change affects these forests. The effects of pre-modern fire on forest regrowth and the gain have not been evaluated.

Our pilot analysis of radiocarbon dated fire from soil charcoal indicates that even the wettest Amazon rainforest has burned, with forests considered to be 'old-growth' having burned within the last few centuries, and 70% of plots (n=70) containing visible soil charcoal fragments. Periodic drier climate and fire use by Native Americans before their populations collapsed ~450 years ago following Europeans colonisation may have resulted in a higher fire frequency than currently observed. Forest regrowth from these and more recent fires may still be occurring in forests considered to be 'undisturbed', e.g., some trees may grow to be 980 years old in central Amazonia, so that forest considered 'old-growth' may still be approaching equilibrium as long-lived trees mature following fire.

Fire also produces soil pyrogenic carbon (PyC) as charcoal that is found in archaeological sites in terra preta soils and in upland soils across Amazonia far from evidence of human settlement. Soil PyC increases soil fertility on otherwise nutrient poor soils, and being resistant to decomposition, may have increased soil fertility across the Amazon. Pre-modern fire and soil PyC are therefore two important ingredients in understanding how Amazonian forests currently function.

We will determine whether regrowth following past fire and soil PyC fertility effects in 'old-growth' permanent forest plots across Amazonia contributes to the observed carbon sink. We have developed a basin-wide network of on-the-ground sample plots, and because methods of measuring the forest with these are fully standardised even across nations they represent an excellent opportunity to measure the response of Amazon forest to historic fire and soil PyC.

In permanent forest plots across the Amazon Basin our Objectives are:
1) determine spatial patterns in 'time since last fire';
2) determine soil PyC stocks, and how these are affected by climatic, edaphic conditions, and fire intensity;
3) using results from (1) and (2), determine whether spatial patterns of productivity and carbon gains in aboveground tropical forest trees in Amazonia are consistent with regrowth from historical fire disturbance and by soil PyC acting as a soil fertility enhancer

Our research will improve understanding of fire patterns across the Amazon for long-term forest plots (the same plots used to estimate the current carbon sink). We will provide a first quantification of: soil PyC stocks, basin-wide environmental drivers of soil PyC stocks, and whether soil fertility is greater where soil PyC levels are higher. This will be a first large-scale test of whether forest productivity, structure, and increases in carbon can be attributed to regrowth from historic fire and soil PyC fertility effects. The results are vital for conservation planning, to estimate the longevity of the carbon sink, and for policy such as Reducing Emissions from Deforestation and Degradation (REDD+).

Planned Impact

The main beneficiaries of this research include:
* Policy-makers, because there is special concern about the loss of forest and climate change risks to the Amazon region. Better understanding of the threats to potentially one of the most important 'hot spots' in the earth system will benefit public and policy-makers alike. For example, these include organisations such as the UN Development program, the IPCC, and local conservation managers.
*NGOs such as the Forest Stewardship Council, and agribusiness in transitional forest areas.
* Climate modellers working at the Met Office.
* The general public, in the UK, in South America, and worldwide, because the historic, contemporary and future response of forests to fire has important implications for soil-vegetation-climate interactions. Changing climate, its impacts on nature, and devising effective mitigation and adaptation is at the forefront of public consciousness as one of the defining challenges of the century.
* School children and university students in South America, who will be most affected by climate change and will benefit from additional awareness and training to help them to contribute to how their communities adapt to, and mitigate against, changing climate.

How?
* The project team has a strong record with demonstrated public, private sector, and governmental impact. For example, governmental agencies in Latin America and the UN Development Program in Brasilia will benefit by learning more about the impacts of fire and long-term change of Amazonian forests, building on previous presentations by the PI to these organisations. Project collaborators interact with the Brazilian 'King of Soya', the largest soya farmer in the world, where we have long-term forest plots located for this study. We will continue with these avenues and with others such as through colleagues of the team at Conservation International and the World Bank, to facilitate application of our results to conservation management plans, REDD+, and national-level policy decisions.
* To further reach the public and private sectors, and the wider scientific community we will use the well-visited websites to which we currently contribute for disseminating outputs, protocols & metadata (www.rainfor.org) and the data (www.forestplots.net) where visitors also access data management and analysis tools. We will also develop multilingual material to be hosted on South American collaborator's websites. We will develop multilingual press releases of research findings through the University of Exeter news office, and request that collaborators publicise the material through local university networks.
* Key messages will be disseminated via scientific briefs made available through the RAINFOR and Exeter websites, especially targeting decision-makers who rely on estimates of forest response to fire and long-term estimates of above-ground biomass gain. We have also hosted Earth Day projects for local school children and will construct interactive displays to use as educational tools during school visits about forest conservation and the effects of climate change on tropical forests.
* In addition to supervising UK and South American PhD students for the project, we will run an analysis workshop in Brazil to train students and facilitate interaction with international researchers from diverse fields. Based on past experience, we will invite local TV stations to the final talks in order to convey our results to the Latin American public.
* We will work with Brazilian PhD students to pursue Brazilian funding through the "Science without Borders" program, allowing the students to spend one year working with the project team at the Univ of Exeter and Leeds.
*We propose constructing a user-friendly Amazon fire web portal to make data easily available to a wider public, as well as public engagement events through public lectures as we have done in Brazil in the past.
 
Description Our preliminary work has resulted in the first Amazon-wide estimate of soil pyrogenic carbon storage in soils. Pyrogenic carbon (macro- and microscopic charcoal) is a component of soil organic carbon formed by the incomplete combustion of biomass and is highly resistant to decomposition. It can act as a long-term soil carbon storage pool and also indicates past fire activity. For many years, Amazon forests were considered fire-free systems. However, our work has shown that past fires left a legacy effect on soils through the presence of greater than expected concentrations of pyrogenic carbon in soils across the whole of Amazonia, including even the wettest regions considered fire resistant. We tested whether forests that had accumulated more pyrogenic carbon and which potentially had more fire in that past, also had trees with different traits such as wind-dispersed seeds, having species that were on average taller, or denser wood that would be associated with a strategy to survive or recover from fire. We found no effect, however, suggesting past fire had little impact on modern forests tree traits; alternatively, past fires may have occurred too long ago to still have an impact on the tree traits found in forests today. We are investigating the chronology of past fires across Amazonia by radiocarbon dating charcoal found in soil. Our preliminary radiocarbon dating of charcoal from evergreen Amazon forests indicate that even the wettest regions of Amazonia have burned within the past ~800 years. We continue to build on these results with our pan-Amazon analysis of charcoal radiocarbon dates through our project partner radiocarbon carbon laboratory in Brazil (Prof. K. Macario) and the NERC Radiocarbon Facility. With these new pyrogenic carbon and radiocarbon data in hand, we are now beginning the remote sensing component of the study to evaluate whether variation in forest structure, biomass, and composition across Amazonia relate to pyrogenic carbon storage and fire history.
Exploitation Route We will continue our soil sampling work across Amazonia and analysis to pursue our project goals. We are exploring opportunities to build on this work through the analysis of soil phytoliths to understand the long-term change (hundreds of years) in vegetation across Amazonia.
Sectors Agriculture, Food and Drink,Education,Environment,Leisure Activities, including Sports, Recreation and Tourism,Culture, Heritage, Museums and Collections

 
Description To extend our work to the public, we worked with the Eden Project to develop interactive scientific displays about the effect of fire, drought, and land-use on tropical forests. We also conducted research training in methods in forest inventory, soil sampling, and laboratory preparation with locals and students at our field sites in four regional locations in Peru, Guyana, Colombia, and Nova Xavantina, Brazil.
First Year Of Impact 2017
Sector Communities and Social Services/Policy,Education,Environment,Leisure Activities, including Sports, Recreation and Tourism
Impact Types Societal

 
Description New PhD programme in Brazil
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
Impact I am an affiliated professor at Universidade do Estado de Mato Grosso (UNEMAT) and the National Institute for Research in Amazonia (INPA). At UNEMAT, I assisted in developing a new PhD programme.
 
Description Training in fire management in Mato Grosso, Amazonia, Brazil
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
Impact I worked with a local NGO Alianca da Terra-Brazil who trains local farmers to reduce and manage fire in Amazonia. With one of the local firefighters from the NGO, I visited farms across the municipality of Feliz Natal, Mato Grosso, Brazil and discussed the impact of fire on their farms. Following this work, we set up plots to study how vegetation in their forest reserves changed following the fires.
 
Description NERC Oversees Develop Assistance (ODA)
Amount £20,000 (GBP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 07/2017 
End 11/2019
 
Description Santander Ayudar Colombia
Amount £1,680 (GBP)
Organisation Santander Universities 
Sector Private
Country United Kingdom
Start 07/2017 
End 09/2017
 
Title contribute data to the database www.forestplots.net 
Description All field data from Amazonia collected through our project is stored on the international database www.forestplots.net. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact Use of data from the database has directly led to the development of publications, including key papers in Nature and Science on topics related to the research project. 
 
Description Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus-AM, Brazil 
Organisation National Institute of Amazonian Research
Country Brazil 
Sector Public 
PI Contribution I co-supervise post-graduate students from the laboratory.
Collaborator Contribution Co-supervise post-graduate students and analyse soil samples collected through this project
Impact The collaboration resulted in two publications by post-docs from the project and one publication from an MSc student on the project.
Start Year 2016
 
Description James Cook University, Australia - Prof Michael Bird 
Organisation James Cook University
Country Australia 
Sector Academic/University 
PI Contribution Co-supervision of post-doc. Payment for sample analysis. Manuscript development.
Collaborator Contribution Analysis of pyrogenic carbon samples from soils from old-growth forests across Amazonia. Co-supervision of post-doc. Manuscript development.
Impact Two papers developed by post-docs.
Start Year 2016
 
Description Universidade Federal Fluminense, Brazil - AMS Radiocarbon Laboratory - Prof Kita Macário 
Organisation Fluminense Federal University
PI Contribution Co-supervision of post-graduate students. Support of the laboratory for sample analysis. Manuscript development.
Collaborator Contribution Radiocarbon dating of charcoal sampled from soil from old-growth forest plots across Amazonia. Co-supervision of post-graduate students. Manuscript development.
Impact Publication by MSc student from Brazil.
Start Year 2016
 
Description University of Queensland - Brisbane, Australia 
Organisation University of Queensland
Country Australia 
Sector Academic/University 
PI Contribution We bring our expertise from Amazonia forest ecology and fire to the work they are doing with atmospheric circulation, palaeo vegetation and fire analysis, and peat.
Collaborator Contribution They bring to our project expertise on atmospheric circulation, palaeo vegetation and fire analysis, and peat.
Impact We had a research meeting at UQ Brisbane to discuss results, draft a PhD advert, and draft a grant proposal.
Start Year 2018
 
Description Carbono pirogénico: un component poco conocido de los suelos forestales tropicales. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Talk in the "Foro Adapatacion al cambio climático em Colombia: El papel de los bosques nativos".
Universidad Nacional Abierta y a Distancia,
Bogota - Colombia
Year(s) Of Engagement Activity 2017
 
Description Historical climatic, vegetational and human controls on Pyrogenic Carbon in Amazonia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Public talk at Instituto Nacional de Pesquisas Espaciais, São José dos Campos/SP - Brazil
Year(s) Of Engagement Activity 2018
 
Description Public evening lecture at Universidade do Estado de Mato Grosso, Brazil 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Evening public talk in Portuguese at the Universidade do Estado de Mato Grosso, Brazil, a small rural university in Amazonia. Following the event I gave an interview with the local TV station (in Portuguese).
Year(s) Of Engagement Activity 2016,2017
 
Description Talk at British Ecology Society conference - 2018 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Oral presentation "The soil pyrogenic carbon stock in the northern of Amazon forest depends on ignition source distance and hydro-edaphic conditions" at BES, Birmingham 2019.
Year(s) Of Engagement Activity 2018
 
Description Teaching at Universidade Federal de Roraima - Brazil 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Teaching R introduction to statistics and Experimental statistics to postgraduate students at Program in Natural Resources, Universidade Federal de Roraima, Brazil.
Year(s) Of Engagement Activity 2017
 
Description Teaching at Universidade do Estado de Mato Grosso, Brazil 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Teaching a post-graduate course on tropical forest ecology to Brazilian students at the Universidade do Estado de Mato Grosso.
Year(s) Of Engagement Activity 2016,2017
 
Description Training of Brazilian post-graduate students in field and lab methods - UNEMAT - Nova Xavantina, Brazil 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Trained Brazilian post-graduate students in soil sampling and laboratory processing - UNEMAT - Nova Xavantina, Brazil, which led to them taking on leadership of the work, with one MSc and one PhD student developing independent research projects based on the training.
Year(s) Of Engagement Activity 2018
 
Description University of Queensland, James Cook University, Univ of Exeter research workshop - Univ of Queensland, Brisbane, Australia 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact We had a research workshop at UQ Brisbane to give talks to post-graduate students in the School of the Environment, discuss results, draft a PhD advert for future work, and draft a grant proposal. The topics focused on understanding the variation in historical fire in Amazonia, changing vegetation, and the role of atmospheric transport in carrying pyrogenic carbon into the wet interior of Amazonia.
Year(s) Of Engagement Activity 2018
 
Description leading training to collect soil and charcoal in Peru, Guyana and Colombia 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Training for a group of researchers and students to teach the method to sample charcoal and soil for pyrogenic carbon analysis. This training was offered during the fieldwork campaign in Peru, Colombia, and Guyana.
Year(s) Of Engagement Activity 2017
 
Description ¿Los Fuegos Pasados Explican la Dinámica de Carbono Actual de Los Bosques Amazónicos? 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Public talk at Universidad Autónoma Gabriel René Moreno, Santa Cruz de la Sierra - Bolivia
Year(s) Of Engagement Activity 2018
 
Description ¿Que nos revela los carbones de los bosque Amazonicos? 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Public talk at Universidad Nacional de San Antonio Abad del Cusco,
Cusco - Peru
Year(s) Of Engagement Activity 2017