Forest Carbon Cycles

Research on forest methane cycling has historically only considered soil emissions and uptake. However, plants also play an important role in routing methane to the atmosphere.  I am exploring the causes, quantities, and consequences of plant-mediated methane emission in upland and wetland forests and their role in greenhouse gas budgets. I am also interested in developing tools for improving spatial and temporal resolution in measuring methane and carbon fluxes.

Mangrove methane emissions: the NASA Blueflux campaign

Mangroves provide numerous ecosystem services including blue carbon storage, but it is poorly understood how methane emissions may offset carbon uptake in these systems, and how the systems may respond to disturbance from hurricanes and development pressures. In the Blueflux mission, I am leading the field survey team to map methane emissions from mangrove forest sediments, plants, and surface waters, as part of a larger NASA mission mapping vegetation structure and greenhouse gas fluxes through towers, aircraft, and satellites. We are working across a gradient of disturbance classes, from "ghost forest" dead zones to regenerating stands in the wilderness of the Everglades National Park.

Tree-mediated methane emissions in temperate forests

In the global methane budget, the largest source of uncertainty is from natural emissions such as those from tree stems. Tree stems have recently been recognized as methane sources, but the extent, variability, and drivers are unclear, particularly in upland forests, where stem emissions may partially offset soil methane uptake. We are working at Yale-Myers Forest and Harvard Forest to quantify methane fluxes across the landscape from different ecosystem components across a range of temporal and spatial scales.

Tree species effects on soil greenhouse gas fluxes

In addition to directly sequestering and releasing carbon, trees can modulate ecosystem greenhouse gas cycling through the effects of individuals and communities on soil processes and gas exchange. In this project, led by Fiona Jevon, we asked how soil respiration and methane oxidation varied beneath different tree species and tree species mixtures, finding different flux rates in soils associated with different species and non-linear responses of soil methane uptake to species assemblages.

Paper available here: Tree Species Effects on Soil CO2 and CH4 Fluxes in a Mixed Temperate Forest


Low-cost automated chambers for distributed sensing

Measuring carbon fluxes generally involves a trade-off between targeting temporal resolution and spatial resolution, and equipment costs limit where these measurements are made and by whom. Low-cost, autonomous sensing tools can increase the accessibility and coverage of these measurements and enable advances in ecological and carbon inventory research. With colleagues Elizabeth Forbes and the GRAB Lab at Yale's Mechanical Enegineering department, we are developing a system of "Fluxbots" for distributed, continuous, and autonomous sensing of gas exchange.

Large herbivore impacts on boreal forest regeneration and carbon sequestration

Using the automated flux chambers described above, we are exploring the interacting effects of forest canopy disturbances (timber extraction, insect outbreaks) and increasing moose population density and herbivory on boreal forest carbon storage and emissions in Newfoundland, Canada. We are monitoring soil carbon fluxes as well as stocks, across land cover and disturbance classes, in order to understand impacts of both changing ecology and forest management decisions on the carbon source/sink strength in this boreal forest.