Written and Developed by Aaron Weiskittel (uredo@excite.com)
INTRODUCTION
DF.HGS is a suite of tools for simulating Douglas-fir individual tree growth and yield in Pacific Northwest plantations that was developed during my dissertation. The tools include a traditional empirical model (GOAB), a crown reconstruction algorithm (BCACS), a stand-level process-based model (NPP), and a hybrid model (HYBRID). These tools are packaged as a R library.
MODEL REQUIREMENTS
To use these tools, the latest version of R (www.r-project.org) and several libraries (nlme, RODBC, Hmisc) are required. Input files can be prepared in Excel and read from anywhere on the computer. BCACS and GOAB require an individual tree list (DBH, HT, HCB, EXPF), stand age, foliage retention, and site index. NPP and the hybrid model require additional information: daily climate records (easily obtained from www.daymet.org for years 1980-2003); site physiographic features (slope, aspect, elevation); soil characteristics (depth, texture, rock content); and an estimate of foliar nitrogen.
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ACKNOWLEDGEMENTS
Thanks to Sean Garber, Greg Johnson, Doug Maguire, and Robert Monserud for assistance during model development. Data and plot access was provided by the Swiss Needle Cast Cooperative, the Stand Management Cooperative, and the Vegetation Management Research Cooperative. The project was funded by the USDA Forest Service.