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Forest Mensuration IIForest Mensuration II

Lecture 8: Inventories with Sample Strips or PlotsLecture 8: Inventories with Sample Strips or Plots

Avery and Burkhart,Avery and Burkhart,Chapter 10Chapter 10

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Strip cruising Plot cruising

Sample areaSample area

X

Fixed-area sampling

Selecting sample trees with probability proportional to frequency

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Strip System of Cruising

Sampling Sampling intensity intensity

Orientation of Orientation of stripsstrips

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Strip System of Cruising

Nominal cruise intensity (I)

Actual cruise intensity

Expansion factor (EF)

100DW

I

Strip width

Distance between strips

100areatracttotal

sampleinareaa

I

I

100EF

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Strip System of Cruising

Advantages– Less time wasted in traveling between

strips than for a plot cruise of equal intensity.

– Fewer borderline trees, because the total perimeter of the sample area is smaller

– Less risk to personnel in remote areas: two people generally work together

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Strip System of Cruising

Disadvantages– Errors are easily incurred through

inaccurate estimation of strip width– Brush and windfall are more of a

hindrance in this system– Spot-checking the cruise is difficult

because strip centerline is rarely marked

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Line-Plot System Cruising

100drepresente area

plots of number *size plot

As with the strip method, line-plot inventories are often planned on a percent cruise basis

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Line-Plot System Cruisingplanning

ProblemProblem– Develop a plan of Develop a plan of

line-plot cruising with line-plot cruising with a given sampling a given sampling intensity, plot size, intensity, plot size, and line distanceand line distance

Example:Example:– A stand of 10 ha (A stand of 10 ha (AA))– Sampling intensity = Sampling intensity =

10% (10% (PP))– Plot size = 0.04 ha (Plot size = 0.04 ha (aa))– Line distance = 100 m Line distance = 100 m

((LL)) What we need to knowWhat we need to know

– How many plots (How many plots (nn))– How to space the plots How to space the plots

((BB))

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Line-Plot System Cruisingplanning

2504.0

1.010

aAPn

1.0100400

LPaB

Area of all plots = Ap

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Line-Plot System Cruising Advantages

– Suitable for one-person cruising– Cruisers do not have to tally trees while

following a compass line– Cruisers pause at plot centers, allowing

more time to check measurements– Tree tally is separated by plots, permitting

quick summary of timber types, species composition, etc.

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Permanent Sample Plots

Purpose: To measure changes in forest conditions

Standard procedures for measurements

Remeasured at periodic intervals

Can determine causes of change

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Ontario Permanent Sample Plots Networks

Provincial growth and yield PSPs Provincial wildlife sample plot

network National Forest Plot Network Forest company PSPs

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Regeneration survey with Sample Plots

Purposes – To evaluate regeneration status– To determine effectiveness of regeneration

treatment– To identify additional treatments needed– To collect data to predict growth and yield– To demonstrate compliance with laws

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Regeneration Survey with Sample Plots

Methods– Stocked-quadrat method (proportion of

land utilized)– Plot-count method (number of trees per

acre)– Staked-point method (like permanent

plots)