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Pellegrini Group: The effect of the interaction between climate change and fire on ecosystem health and productivity in tropical and temperate forests

NERC / GFC / OTHER

Supervisor: Adam Pellegrini (Plant Sciences)

Importance of work

Climate change is causing fires to become more frequent and intense in many ecosystems across the globe, generating 'novel' fire regimes that stress an ecosystem. These rapid changes are concentrated in particular ecosystems such as tropical forests and high-alpine and latitude coniferous forest ecosystems, which coincidentally also are critical reservoirs for carbon. One hypothesis is that intensifying fire regimes in these ecosystems will produce large losses of carbon, but if it only occurs from vegetation, the ecosystem can rapidly recover when fire is excluded; an alternative hypothesis is that losses of carbon from soil places a longer-term constraint on the capacity of the ecosystems to recover carbon. This project will involve research in two ecosystems, tropical forests in central Brazil and coniferous forests in the Sierra Nevada of California, which contain sites that have been burned at different fire frequencies for the past 40 years. A combination of field measurements and laboratory analyses will characterize key uncertain carbon fluxes from soils and vegetation to test the alternative hypotheses about carbon cycle resilience.

Project summary

The project will take place in two main sites with fire manipulation experiments (Aguas de Santa Barbara in Brazil and Sequoia National Park in California, USA). Sampling of plant growth and carbon storage in a gradient of plots exposed to different burning frequencies will be used to quantify the regrowth and resilience of vegetation to fire. Analyses of soil carbon cycling using in situ measures of microbial activity and laboratory measurements of specific microbial enzymes, and δ14C will be used to quantify carbon turnover, while measurements of microbial community composition, organic matter chemistry, and charcoal content will be used to determine the mechanisms controlling the carbon turnover.

What the student will do

The project will combine both field and lab work.

  1. Fieldwork: Fieldwork will be carried out in field sites in Sequoia National Park (California, USA) and Aguas de Santa Barbara (São Paulo state, Brazil). Time will be spent conducting vegetation and microbial respiration measurements during the growing seasons in the field and collecting soil samples for future analyses in the lab.
  2. Labwork: Analyses of the amount and form of carbon and nutrients in the soil will be carried out in the lab using combustion and gas chromatography. Microbial activity assays will include multi-month jar incubations to measure CO2 respiration, microbial biomass, and extracellular enzyme activities.

Training to be provided

The student will be trained in field survey and sampling techniques, biogeochemistry (carbon and nutrient measurements in soils, organic matter chemistry, and mineral-carbon interactions), and microbiology (microbial biomass, respiration assays, extracellular enzyme assays). Moreover, the broad geographical scope will give them exposure to working in international collaborations and allow them to create a strong research network.

References

  • Pellegrini, A. F. A. A. F. A., W. R. L. W. R. L. Anderegg, C. E. T. E. T. Paine, W. A. W. A. Hoffmann, T. Kartzinel, S. S. Rabin, D. Sheil, A. C. A. C. Franco, and S. W. S.W. Pacala. 2017. Convergence of bark investment according to fire and climate structures ecosystem vulnerability to future change. Ecology Letters 20:307–316.
  • Pellegrini, A. F. A., A. Ahlström, S. E. Hobbie, P. B. Reich, L. P. Nieradzik, A. C. Staver, B. C. Scharenbroch, A. Jumpponen, W. R. L. Anderegg, J. T. Randerson, and R. B. Jackson. 2018. Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity. Nature 553:194–198.

 

 

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