CF Data Analysis & Reporting 3 — Questions and Answers
Question 1: Which growth model type assumes that a tree's growth rate decreases as it approaches a maximum size, forming an S-shaped curve?
- Linear model
- Exponential model
- Sigmoidal (logistic) model (Correct answer)
- Power model
Correct answer: Sigmoidal (logistic) model
Sigmoidal models like the Chapman-Richards or logistic curve describe slow early growth, rapid middle growth, and slowing near maximum size.
Question 2: A forester wants to estimate timber volume for an entire watershed from a sample of plots. After calculating the mean volume per hectare, she multiplies by total watershed area. This is an example of:
- Ratio estimation
- Expansion by area (Correct answer)
- Regression estimation
- Double sampling
Correct answer: Expansion by area
Expansion by area multiplies the per-unit-area estimate by the total area to obtain a population total.
Question 3: In a Geographic Information System (GIS) analysis, which data type is best suited for representing continuous forest canopy cover across a landscape?
- Vector point data
- Vector polygon data
- Raster data (Correct answer)
- Attribute table data
Correct answer: Raster data
Raster data represents continuous spatial variables like canopy cover as a grid of cells, each with a value.
Question 4: A site index curve for a forest stand is used primarily to:
- Estimate current standing timber volume
- Predict future tree diameters
- Evaluate site productivity based on height-age relationships (Correct answer)
- Determine basal area growth rates
Correct answer: Evaluate site productivity based on height-age relationships
Site index uses dominant tree height at a base age (commonly 25 or 50 years) to index the productive potential of a site.
Question 5: When reporting forest inventory results, the 95% confidence interval means that:
- 95% of trees fall within this range
- There is a 95% probability the true population mean falls within this interval (Correct answer)
- The sample mean is 95% accurate
- 95% of the data is normally distributed
Correct answer: There is a 95% probability the true population mean falls within this interval
A 95% confidence interval implies that if sampling were repeated many times, 95% of such intervals would contain the true population parameter.
Question 6: A forester records the number of dead trees per plot across 30 plots. Which chart type best visualizes the frequency distribution of these counts?
- Pie chart
- Scatter plot
- Histogram (Correct answer)
- Line graph
Correct answer: Histogram
A histogram displays the frequency distribution of a single continuous or count variable, making it ideal for showing how plot-level dead tree counts are distributed.
Question 7: In LiDAR-based forest inventory, which metric is most directly used to estimate canopy height?
- Point density
- Return intensity
- Normalized height of returns above ground (Correct answer)
- Scan angle
Correct answer: Normalized height of returns above ground
Normalized height (above-ground elevation of LiDAR returns after subtracting the ground surface) directly represents canopy structural height.
CF Data Analysis & Reporting 3
Which growth model type assumes that a tree's growth rate decreases as it approaches a maximum size, forming an S-shaped curve?