ICAR AICE-JRF/SRF Growth & Yield Modelling: practice questions

1 · Growth curves and growth functions · medium

A Chapman-Richards height model is H = 30(1 − e^(−0.05t))^1.5. What height does it predict at age 20?

1. 19.0 m
2. 15.1 m
3. 6.7 m
4. 30.0 m

2 · Growth curves and growth functions · medium

The Gompertz function Y = A exp(−b e^(−kt)) has its inflection point at:

1. A/2, exactly half of the asymptote
2. A/e, or roughly 37% of the asymptote
3. A, the asymptote itself, reached at infinite age
4. A/4, a quarter of the asymptote at all parameter values

3 · Growth curves and growth functions · hard

Why are polynomial equations poor choices for projecting stand yield beyond the ages in the data?

1. They can turn downward or rise without limit outside the data range
2. They cannot be fitted by least squares to forest growth data of any kind
3. They always pass exactly through every data point, leaving no residuals
4. They require site index as a variable, which is rarely measured

4 · Growth curves and growth functions · hard

For a Chapman-Richards curve with c = 3, the inflection lies at A(1 − 1/c)^c. What fraction of the asymptote is this?

1. 0.50
2. 0.37
3. 0.67
4. 0.30

5 · Self-thinning rule and density management diagrams · medium

Along Reineke's self-thinning line, if quadratic mean diameter doubles, stems per hectare fall by a factor of about:

1. 2.0
2. 3.0
3. 1.6
4. 4.0

6 · Diameter-distribution models · medium

A three-parameter Weibull with a = 5 cm, b = 15 cm and c = 2 describes a stand's diameters. What proportion of trees is smaller than 20 cm?

1. 36.8%
2. 83.1%
3. 50.0%
4. 63.2%

7 · Diameter-distribution models · medium

A Weibull shape parameter c less than 1 produces a diameter distribution that is:

1. Nearly symmetric, as in even-aged stands
2. Nearly symmetric, as in even-aged stands of one species
3. Reverse-J shaped, as in uneven-aged stands
4. Bimodal with two distinct peaks

8 · Diameter-distribution models · easy

In the three-parameter Weibull, the location parameter a represents:

1. The most common (modal) diameter class in the stand
2. The quadratic mean diameter of the stand
3. The smallest possible diameter in the distribution
4. The largest diameter in the stand

9 · Individual-tree distance-independent and distance-dependent models · hard

A common finding when distance-dependent and distance-independent models are compared for stand totals is that:

1. Spatial models are only slightly more accurate, despite costly stem maps
2. Spatial models are always several times more accurate for stand totals
3. Distance-independent models cannot predict stand totals at all
4. Spatial models cannot be used in any planted forest

10 · Individual-tree distance-independent and distance-dependent models · hard

Errors in which component of individual-tree simulators most often accumulate over long projections?

1. Conversion of diameters from inches to centimetres
2. Calculation of basal area from diameter
3. The species codes in the input tree list
4. Mortality and ingrowth predictions