Forest and Disturbance Ecology
Pests, pathogens, disease and decay in natural and managed forestsÂ
Beech leaf disease (BLD) is an emergent and rapidly spreading disease, spread by an introduced nematode and expected to cause widespread mortality of a foundational forest species. In a collaboration with the Connecticut Agricultural Experiment Station, the Brodersen Physiological Plant Ecology Lab, and the Poulos Forests & Global Change Lab at Wesleyan, we are investigating the forest dynamics and ecophysiological impacts of beech leaf disease as it progresses through New England. I am co-leading work to investigate whether carbon starvation through exhaustion of non-structural carbohydrate stores may be responsible for BLD-induced mortality.
The hemlock woolly adelgid (HWA) is another introduced forest pest, which causes decline or death in Eastern hemlocks by feeding on sap from their needles. Decisions on forest management, and consequences for forest composition and carbon storage in forest ecosystems and harvested wood products, depend on knowledge of how HWA affects the structural properties of wood in the trees it infests. In a collaboration with researchers from UMass Amherst Department of Environmental Conservation, I am comparing and employing non-destructive methods to assess wood structural losses and decay status. Specifically, I am using sonic and electrical resistance tomography to image the condition inside living trees.
I am further leveraging this tomography technology to explore whether tree internal decay may be a cryptic driver of carbon losses and greenhouse gas emissions in forests. In our work on tree methane emissions at Harvard Forest, I am investigating whether incipient decay in living trees is responsible for stem methane emissions due to internal moisture accumulation, anoxia, and structural or non-structural carbohydrate consumption.
Large herbivore impacts on boreal forest regeneration and carbon sequestration
In the boreal forests of Newfoundland, Canada, the interacting effects of forest canopy disturbances (timber extraction, insect outbreaks) and increasing moose population density and herbivory play a major role in shaping forest structure, dynamics, and carbon sequestration. In a collaborative project between Memorial University of Newfoundland, Yale, and Parks Canada, we are monitoring vegetation community composition and structure and soil carbon fluxes and 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 across the lansdcape mosaic.
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Exploring ecosystem surface areas with terrestrial laser scanning
While decades of research have informed our understanding of tree volume and biomass dynamics across forest types and successional stages, comparatively minimal effort has gone into describing the surface area characteristics in forested ecosystems. Surface area is a potentially functionally important ecological property (as habitat for epiphytes, animals, and microbes, and as interface for biological interaction and resource exchange), and an instrumentally useful property for the scaling of surface-atmosphere biogeochemical fluxes (such as tree-mediated methane emission). The advent of terrestrial-based LIDAR enables the exploration and quantifcation of ecosystem surface area. With colleagues at Southern Cross University of Australia, NASA Goddard Space Flight Center, and the Coastal Studies Institute, I am exploring the measurement of forest surface areas using LIDAR.