Title: Post-Disturbance Dynamics of Carbon, Water and Energy Fluxes Between Land and Atmosphere to Assess Full Climate Impacts
Project Description: Ecological disturbances such as the clear cutting of forests are known to perturb ecosystem-atmosphere exchanges of water, carbon and energy in profound ways. However, the degree, character, and persistence of such perturbations are largely unknown. Nonetheless, they have important long term implications for a host of ecosystem services such as carbon sequestration, wildlife habitat, and climate regulation. This project’s main objective is to quantify the full climate impacts of forest disturbances including the net ecosystem carbon balance, and energy and water forcings on atmospheric warming.
We are addressing the following broad questions:
- How rapidly is post-disturbance slash decomposed and emitted to the atmosphere?
- How long does it take for plant productivity to recover so that a disturbed site crosses over from being a net source of CO2 to the atmosphere to a net sink of CO2?
- How do disturbance-induced changes in albedo, surface temperature, and evapotranspiration combine to influence surface and atmospheric warming/cooling?
- How do these rates of exchange compare to those for other neighboring land covers, such as mature mixed-deciduous and hemlock forests?
Methods: In spring 2009, an eddy covariance tower and associated peripheral sensors were deployed at the clear-cut site. Since 2010, basic site characteristics have been collected annually by summer REUs, including surveys of vegetation composition, height, leaf area, and dead biomass. We have also monitored leaf-scale gas exchange rates with a chamber-based, portable infra-red gas analyzer, and soil respiration rates in trenched and untrenched plots. New work is focusing on extending to neighboring sites to study how post-clearing dynamics vary in the region and with age using a chronosequence approach and remote sensing plus ground based inventory sampling. We are also deploying a 40 m tram suspended above the forest to semi-continuously monitor the surface radiation balance, light and temperature environment, and hyperspectral reflectance as an indicator of vegetation structure and function.
Products:
Khomik M, Williams CA, Vanderhoof MK, MacLean R, Dillen SY (2014) “On the causes of rising gross ecosystem productivity in a regenerating clearcut environment: leaf area, species composition, or environmental conditions“, Tree Physiology, doi:10.1093/treephys/tpu-049 (pdf copy).
Williams CA,Vanderhoof M, Khomik M, Ghimire B (2013) “Post-clearcut dynamics of carbon, water and energy exchanges in a mid-latitude temperate, deciduous broadleaf forest environment“, Global Change Biology, Online October 18, 2013, DOI: 10.1111/gcb.12388 (pdf copy).
Vanderhoof M, Williams CA, Pasay M, Ghimire B (2013) “Controls on the rate of CO2 emission from woody debris in clearcut and coniferous forest environments of central Massachusetts“, Biogeochemistry, 114:299-311, DOI: 10.1007/s10533-012-9810-4. (pdf copy)