Comparison between intensity based inventory and sampling based inventory Bogdan Strimbu Louisiana Tech University
Apr 01, 2015
Comparison between intensity based inventory and sampling based inventory
Bogdan StrimbuLouisiana Tech University
Issue
• Inventory of the forest resources
• Practical applications: preset intensity
• Alternative: sampling design
• Legal constraints
2
Objective
• Questions to answer:
1. Is preset-intensity inventory legally defendable?
2. Are there significant differences between preset-
intensity inventories and sampling based
inventories?
3
Approach
• USFS and Florida Assessor guidelines
• Sampling error standards dependent on the
estimated value of the sale
• alpha=5%
4
Sampling error standardsUSFS Alpha=5%
Value SE
<15000 20%
<35000 19%
<55000 16%
<75000 14%
<95000 12%
>95000 10%
Florida merchantable planted pine alpha=5% SE=10%
merchantable natural timber alpha=10% SE=10%
pre-merchantable pine alpha=32% SE=10%
5
Settings• Preset - intensity inventories: 5% and 10%
• Alpha=5%→Approximate t=2
• Plot size: 0.1. ac
• Simple Random Sampling without replacement
• Homogeneous stand → No stratification
• The population has a mean
6
Formulae
222
1
1
1
1
1
1
:
:
tCVAE
NtCVAE
NN
N
ni
tCVAE
N
n
SRSdesignSampling
N
niNi
plotArea
Areain
Intensity
7
Sample size vs. CV• Area=10 ac
8
Sample size vs. CV• Area=20 ac
9
Sample size vs. CV• Area=50 ac
10
Sample size vs. CV• Area=100 ac
11
Sample size vs. Sample error• Area= 10 ac
12
Sample size vs. Sample error• Area= 20 ac
13
Sample size vs. Sample error• Area= 50 ac
14
Sample size vs. Sample error• Area= 100 ac
15
Intensity – CV for a=10%
16
0 5 10 15 20 25 30 35 40 45 500%
1%
2%
3%
4%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
20 ac @SE=10% 20 ac @SE=20% 50 ac @SE=10% 50 ac @SE=20%
100 ac @SE=10% 100 ac @SE=20% 200 ac @SE=10% 200 ac @SE=20%
10 ac @SE=10% 10 ac @SE=20%CV [%]
Inte
nsit
y fo
r sta
nd a
rea>
20 a
c
Inte
nsit
y fo
r sta
nd a
rea
= 10
ac
Intensity – CV for a=5%
17
0 10 20 30 40 50 600%
1%
2%
3%
4%
5%
0%
10%
20%
30%
40%
50%
60%
20 ac @SE=10% 20 ac @SE=20% 50 ac @SE=10% 50 ac @SE=20%100 ac @SE=10% 100 ac @SE=20% 200 ac @SE=10% 200 ac @SE=20%10 ac @SE=10% 10 ac @SE=20%
CV [%]
Inte
nsit
y fo
r sta
nd a
rea>
20 a
c
Inte
nsit
y fo
r sta
nd a
rea=
10
ac
Summary• USFS guidelines more strict then state guidelines• Intensity based inventory – legally defendable
using USFS or state guidelines (Florida) most of the cases
• Stratification recommended for high variable stands
• Intensity based inventory for stands>20 ac at least double the cruising effort
• For stands larger than 50 ac the cruising effort is almost comparing with the sampling based inventory 18
Cauchy distribution
19
2
0
0
1
1),;(
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