SWAT Literature Database for Peer-Reviewed Journal Articles

Title:A comparison of simulated and field-derived Leaf Area Index (LAI) and canopy height values from four forest complexes in the southeastern USA 
Authors:Iiames, J.S., E. Cooter, D. Schwede and J. Williams 
Volume (Issue):9(1) 
Article ID:26 
URL (non-DOI journals): 
Broad Application Category:crop/plant/tree growth or production 
Primary Application Category:crop, forest and/or vegetation growth/yield and/or parameters 
Secondary Application Category:calibration, sensitivity, and/or uncertainty analysis 
Watershed Description:Four sites in North Carolina and Virginia in the southeast U.S. 
Calibration Summary: 
Validation Summary: 
General Comments:This study was performed with the EPIC model. However, the authors state in Section 2.4 that the simulations performed in EPIC were heavily influenced by previous ALMANAC and ALMANACBF studies, and that an overall goal of the research was to help improve representation of agro-forests in SWAT. 
Abstract:Vegetative leaf area is a critical input to models that simulate human and ecosystem exposure to atmospheric pollutants. Leaf area index (LAI) can be measured in the field or numerically simulated, but all contain some inherent uncertainty that is passed to the exposure assessments that use them. LAI estimates for minimally managed or natural forest stands can be particularly difficult to develop as a result of interspecies competition, age and spatial distribution. Satellite-based LAI estimates hold promise for retrospective analyses, but we must continue to rely on numerical models for alternative management analysis. Our objective for this study is to calculate and validate LAI estimates generated from the USDA Environmental Policy Impact Climate (EPIC) model (a widely used, field-scale, biogeochemical model) on four forest complexes spanning three physiographic provinces in Virginia and North Carolina. Measurements of forest composition (species and number), LAI, tree diameter, basal area, and canopy height were recorded at each site during the 2002 field season. Calibrated EPIC results show stand-level temporally resolved LAI estimates with R2 values ranging from 0.69 to 0.96, and stand maximum height estimates within 20% of observation. This relatively high level of performance is attributable to EPIC’s approach to the characterization of forest stand biogeochemical budgets, stand history, interspecies competition and species-specific response to local weather conditions. We close by illustrating the extension of this site-level approach to scales that could support regional air quality model simulations. 
Keywords:LAI; leaf area index; EPIC; simulation; satellite; MODIS; biomass; evaluation; southern U.S. forests