Tropical Rain Forest

Current Experiment: Trees as conduits for connecting below ground microbial processes to above ground methane emissions at the Terrestrial Aquatic Interface 

 The global methane budget is still poorly understood and the emissions from one of the largest natural sources, the Amazon basin, we only know very small bits of. The recent discovery that tree stems can contribute 50% of the total methane ecosystem flux, while nobody has measured tree stems for methane emissions until 5 years ago (Dr. Joost van Haren, Interim Director of Rain Forest Research, was one of the first to start this in the Amazon basin).

The proposal sets out to understand the contribution of tree methane emissions in both a flooded forest and an upland forest. We already have an eddy covariance tower in the upland forest and we are going to add methane emissions to that and we plan to construct a varzea tower in the next year (the current Brazil trip was to find a suitable location for that tower). 

At Biosphere 2, Dr. van Haren will work with students to test out the automated stem and soil/water surface measurement system. These systems are complicated, because the forest floods with at least 5 feet of water every wet season and the measurement system cannot allow any water to enter into the tubing and machines. The automated stem and soil/water surface measurements have to float up and down with the water level, but still create a secure seal with the surface they are measuring from. The Biosphere 2 varzea area, which can be flooded, is the ideal place to test these systems out before they are brought to Brazil, where technical modification are much harder to do.

2019 Rain Forest Water, Air, and Life Dynamics (WALD) Experiment

The Biosphere 2 Water, Atmosphere, and Life Dynamics (B2 WALD, Wald = forest in German) campaign will leverage Biosphere 2 Tropical Rain Forest (B2 TRF) experimental capabilities to investigate mechanisms that underlie plant-soil-microbe relationships using whole ecosystem stable carbon and water isotope labelling across drought and rewet conditions. The overarching aim of B2 WALD is to fully track, from molecules to the ecosystem, mechanisms driving the fate of carbon and water in forest systems under drought. We will place particular focus on diverse volatile and nonvolatile carbon metabolites, their role in plant and microbial C allocation, and potential to reveal underlying mechanisms. Extensive instrumentation is needed to monitor all ecosystem components (atmosphere, soil, leaves) including multiple gas analyzers for key species (e.g., 13C-CO2 and VOCs). To achieve our scientific aim, we have engaged an international team of scientists with enthusiasm for integrated, transdisciplinary research.

This campaign is centered on Prof. Dr. Christiane Werner’s EUR 1.9M European Research Council (ERC) Consolidator Grant entitled “Biochemical link between plant volatile organic compound (VOC) emissions and CO2 metabolism - from sub-molecular to ecosystem scales”. It is co-led with Biosphere 2 Tropical Rain Forest Director Prof. Dr. Laura Meredith (Assistant Professor, University of Arizona, Tucson). The overall goal of the grant is to develop a novel technological and theoretical basis to couple CO2 fluxes with VOC emissions that will establish mechanistic links between primary and secondary carbon metabolism in plants.

The Werner Group has demonstrated the application of cutting-edge technology (δ13CO2 laser spectroscopy, high sensitivity PTR-TOF-MS and quantitative isotopic NMR spectroscopy) to characterize real-time carbon allocation into VOCs and CO2 using plant position-specific 13C-pyruvate labelling (labelled at the C1 or C2-carbon position) at the branch scale (Fasbender et al. 2018) and, more recently using entire plants.  The final stage of the ERC grant proposed to demonstrate the world-wide first canopy positional labelling in the unique facilities of the tropical rainforest in the Biosphere 2, Arizona, the world’s largest controlled growth facility: the Biosphere 2 Tropical Rain Forest. The B2 TRF is the ideal location for this project because whole-ecosystem fluxes can be measured within the enclosed system, the environment is controlled, and the canopy can be accessed, which enables real-time monitoring of ecosystem and branch-level fluxes. This whole ecosystem labelling experiment is a unique opportunity to assess ecosystem processes – from the atmosphere, biosphere, soil and hydrology. Our methodological approach enables novel insights into all these different ecosystem components. Moreover, the biosphere is the world-wide sole system, where full ecosystem manipulation experiments are possible. 

Soil Pit

Rain Forest at Night

An unprecedented 4-month labelling experiment will be conducted by 1) simulating an ecosystem drought and recovery and 2) bringing in experts and equipment to enable simultaneous measurements of pools and fluxes at the atmosphere, vegetation (phyllosphere, stems), rhizosphere, microbiome and deep water soil processes.

Figure 1. Schematic of B2 Rain Forest Stable Isotope Labelling Experiment timeline including general plans for timing and expectations.

The B2-WALD campaign will be ground-breaking in:

  • Tracing pools and fluxes at all levels throughout the ecosystems, disentangling ecosystem processes, interactions and feedbacks to an important climate change driver (drought) from the atmosphere, biosphere (including phyllosphere, rizosphere) and hydrology
  • Closing carbon and water budget at an ecosystem scales (in a unique closed facility)
  • Partitioning carbon allocation from the molecular to the ecosystems scale
  • Integrating metabolomics, genomics, volatilomics into ecosystem fluxes approaches in a truly interdisciplinary manner
  • Deconvoluting of the role of deep water reserves, quantifying the role of hydraulic lift by deep rooted trees to ecosystem water budgets by groundwater labelling

The Rain Forest campaign will produce massive amounts of diverse, but integrated, data to paint an exceptional picture of the movement of carbon and water through an ecosystem before, during, and after drought, as a function of diverse biological and abiotic drivers. The stable isotope label applied to ecosystem can be studied in the years to come, asking how long carbon will remain stabilized in the soil for example. Finally, we expect that the high rigor and ambitious scope of this campaign will highlight the unique ability to study the mechanisms underlying emergent ecosystem processes, and one outcome will be to embed this perspective in the minds of scientists and the public.

Person in Rain Forest canopy

Processing samples

Organization and Management

The campaign is co-led by Christiane Werner (Full Professor, University of Freiburg) and Laura Meredith (B2 Rain Forest Science Director and Assistant Professor, SNRE, UA), with leadership and organization also by Nemiah Ladd (Research Associate and Lecturer, University of Freiburg).  The B2 Rain Forest team is led by Laura Meredith and includes John Adams (Deputy Director), Joost van Haren (Asst. Research Professor), and Jason Deleeuw (Research Specialist), with participation from additional B2 staff based on topic.

Committed Participation and Contributions


This will be a large-scale, international research campaign, led by the ERC-team based at the UA Biosphere 2 that will bring in external contributions including personnel, equipment, and research capabilities.

The number of partners currently committed to the campaign, in addition to Biosphere 2 team members (6-8), is approximately 50 participants (MS Students to Professors) from 20 research groups and 13 institutions located both US (3 US universities including UA/B2) and EU (10 EU from Germany, Switzerland, Austria, and Scotland).

Our partners have committed instrumentation to enable measurements of fluxes and isotopic signatures of carbon and water cycling across ecosystem scales on a continuous, high frequency basis. This includes major equipment valued at approximately $3.2M ($0.9M from UA$2.3M external equipment) that will be brought to B2 for the campaign, running 4PTR-TOF-MS and six 13CO2 and 2H2O-lasers in parallel and major equipment valued at approximately $3.1M ($1.6M from UA$1.5M external equipment) that will be used remotely to analyze samples collected at B2 Collectively, our colleagues and partners have committed around $5M in instrumentation to provide an unparalleled picture of ecosystem C and H2O cycling through the rain forest soil, plants, microbes, and atmosphere during this campaign.

For more information about the WALD project email Dr. Laura Meredith

For more information about the Tropical Rain Forest's research endeavors email Dr. Joost van Haren

Rain Forest Research Team