Measurement, Analysis & Decision Support Systems Flashcards

What is the primary limitation of using USDA Forest Service FIADB data for a county-level timber inventory at a specific point in time?

Answer: Plots are on a rotating panel schedule so not all plots within a county are measured in the same year

FIA's rolling annual panel design means county-level estimates pool data from multiple measurement years, introducing temporal variance that limits single-point-in-time precision.

The net present value (NPV) of a timber investment is most sensitive to which factor over a 50-year rotation?

Answer: The discount rate used to compound future revenues

Over a 50-year horizon, small changes in the discount rate exponentially shift the present value of revenues; this dominates sensitivity compared to measurement or rule-conversion errors.

A forester applies logistic regression to predict the probability of pine bark beetle infestation based on stand density and drought index. The model output is interpreted as:

Answer: The log-odds of infestation, which must be transformed via the logistic function to obtain probability

Logistic regression models log-odds = β₀ + β₁X₁ + …; applying the logistic function P = 1/(1+e^{−log-odds}) converts the linear predictor to a probability between 0 and 1.

In photogrammetric stem mapping using UAS imagery, which processing workflow correctly produces individual tree crown polygons from an RGB orthomosaic?

Answer: Structure from Motion → Dense point cloud → Canopy Height Model → Local maxima detection → Watershed segmentation

SfM generates a point cloud from overlapping photos; after ground normalization to produce a CHM, local maxima mark treetops and watershed segmentation delineates crown boundaries.

Which of the following describes 'model-based' inference in forest inventory, as opposed to 'design-based' inference?

Answer: Model-based inference assumes a superpopulation model for tree attributes, allowing auxiliary data to improve estimates even without probability samples

Model-based inference treats the population as a realization of a stochastic process (superpopulation) and uses covariate relationships (e.g., LiDAR predictors) to improve estimates, not just sampling randomness.

A forester wants to estimate the number of snags per acre in a stand using line-intercept sampling. The correct estimator for density (N/acre) of snags crossing transects is:

Answer: Count of intersected snags × (π/2) / total transect length × mean snag length factor

For line-intercept sampling of objects, density is estimated using the formula accounting for transect length and the projected width of objects; for standing dead wood the factor involves π/2 and mean diameter.

When a silvicultural prescription model predicts stand development using a matrix model (Usher/Leslie matrix), what do the matrix elements represent?

Answer: Transition probabilities or growth rates between size classes over a fixed time step

In a Usher-type matrix model, off-diagonal elements represent the probability of a tree transitioning from one diameter class to the next, and diagonal elements represent the probability of remaining in the same class during one time step.