Predicting the growth of deciduous tree species in response to water stress: FVS-BGC model parameterization, application, and evaluation

An individual-tree, distance-independent forest stand projection model (FVS-BGC) was applied to study deciduous species response to water stress. FVS-BGC couples the process model STAND-BGC to the empirically based forest vegetation simulator (FVS). We sought to determine whether the hybrid model could be expanded to simulate deciduous trees and their response to water stress, where to date the model has not been used beyond coniferous trees. FVS-BGC was parameterized with comprehensive ecophysiological, site, and silvicultural data collected on Acer rubrum L. (A. rubrum), Paulownia elongata (P. elongata), Quercus nuttallii (Q. nuttallii), and Quercus phellos (Q. phellos). Species-specific carbon gain and growth were simulated under well-watered and water-stressed conditions. Simulations on species-specific bases allowed assessment of drought effects on stand production and the ability to test FVS-BGC's capability to predict the water stress responses of deciduous species. Under well-watered conditions, FVS-BGC height and caliper predictions were not statistically different from measured values for P. elongata, Q. nuttallii and Q. phellos. Under water stress, FVS-BGC accurately predicted height and caliper in Q. nuttallii and Q. phellos. For carbon sequestration, FVS-BGC predictions agreed with measured values on all study species under well-watered and water-stressed conditions. In general, the simulations showed that modelled height, caliper, and carbon sequestration were consistent with observed data. This study establishes the potential for FVS-BGC applications to include deciduous species-specific simulations and their respective water stress responses.