Methods
Authored By: J. Pontius, R. Hallett, M. Martin, L. Plourde
Plots in mature hemlock (where hemlock occupies >50 percent of the canopy) were established across a wide range of hemlock health, HWA infestation levels, site characteristics, and stand demographics. This included 48 sites characterizing the extremes of hemlock resistance and vulnerability to HWA from Pennsylvania to Maine (see figure at right). At each plot, a minimum of 5 hemlocks was sampled yearly between 2001 and 2005. Whereas statistical models were based on plot-level data, development of a landscape-scale GIS risk coverage was limited to the Catskills region of New York where hyperspectral imagery was available.
Subsections found in Methods
- Field and Laboratory Methods : Each plot was sampled and evaluated yearly for a suite of decline symptoms, foliar chemistry, and HWA infestation levels.
- Predictive Model Calibration : Data from plots that are known to have been infested for at least 4 years were used to calibrate a linear, mixed stepwise model of average decline since infestation. In a mixed platform, forward and backward steps are enlisted.
- GIS Data Layers Used for Mapping Risk in the Catskills : Hemlock vulnerability to HWA is complex and linked to multiple site, climatic, stand, and chemical factors.
- Risk Coverage for the Catskills : The results of this model highlight which environmental variables are significant in determining hemlock decline rates and the nature of those relationships.
Encyclopedia ID: p3546
