||Disturbance events directly affect carbon (C) uptake through loss of leaves and needles, and indirectly by altering detrital pools, nutrient dynamics, and nutrient availability, which in turn can affect leaf biochemical function. An increase in temperature and changes in precipitation regimes are expected with global climate change. Hurricanes and droughts, which increase tree falls and forest fires, may also increase in the future. In temperate regions, higher temperatures are also likely to increase the frequency and severity of insect outbreaks. Epidemic insect outbreaks have been recently shown to reduce C-uptake by forests significantly, and will affect long-term C storage.
We study of two contrasting disturbances - gypsy moth outbreak and prescribed forest fire and their effects on the structure, dynamics, microclimate and resulting carbon budget of an east-coast oak/pine forest, in the New Jersey Pine Barrens. Eddy-covariance measurements are used to determine the carbon budget, evapotranspiration, and canopy microclimate before and after the disturbances. Sap-flow measurements will be used to determine tree-level transpiration and hydrodynamic stresses. Remote sensing of the canopy will be used to measure the extent and pattern of reduction in leaf area and change of vertical and horizontal structure following each disturbance type. These measurements will be used to parameterize and validate tree-scale large-eddy simulations and tree-crown hydrodynamic modeling of the canopy and the processes that drive changes to C budget and ecosystem dynamics after the disturbances.
Canopy net assimilation will be simulated with the Canopy Conductance Constrained Carbon Assimilation model (4C-A). The 4C-A model will be modified to allow modeling future disturbance effects in the NJ Pine Barrens by linking it to a high-resolution 3D explicit canopy domains, and the Finite-Elements Tree-Crown Hydrodynamics (FETCH) model, which resolves branch-level water flow within the tree system, and hydrodynamic limitations to transpiration. The results of these models will be dynamically linked to the Ecosystem Demography model (ED2) which is a plot-scale ecosystem land-surface model that is driven by above canopy meteorological measurements, or by a large-scale meteorological models.
The Pine Barrens contain the largest area of forest in New Jersey and, as such, contain the largest C sink in NJ as well. However, disturbances such as fire, insect outbreak, and windfall hamper C uptake and storage. The coupled model that will be developed here will help to further account for effects of climate change-induced disturbances such as fire and herbivory in order to improve the predictability of regional forest C balance . Model development and evaluation will be done at the Silas Little Experimental Forest, which is a part of the Ameriflux network.