2.3 Sampling Designs for Continuous Forest Inventory
A simple pattern distribution of permanent plots in large areas Arianna Sorrentino
Summary
A permanent sampling design is described for continuous forest inventory, growth and yield evaluation of commercial forests in Uruguay. A simple plot pattern is used for large areas forested with commercial multipurpose Pinus and Eucalyptus species, as a timber resource for different aims: energetic sawing, pulp and paper, and other specific products.
A periodic field work is carried out, to collect a very detailed dendrometric and stands information, to estimate and predict different products in the same trees and forested areas.
Results of the continuous inventory are the basis to take technical and commercial decisions during the biological cycle of the stands. Forest inventory design is very simple:
two types of circular Bitterlich plots, distributed in a systematic reticular pattern. General plots to calculate mean stands and tree parameters, and commercial volume variance, for different evenaged stands in various strata of age. Permanent plots for a complete quantitative evaluation with diameter and height classes and all the traditional dendrometric and stand parameters for sylvicultural management purposes. Method is very simple, rapid and efficient: with periodical cuts and direct volume mensuration, predicted and obtained values are compared. Errors of estimation are continuously updated for different kinds of products, and correction coefficients are included in the geographic information processing software.
2.3.1 Introduction
A permanent research sampling design is described for continuous forest inventory, growth and yield evaluation in several regions of Uruguay, forested with Pinus and Eucalyptus, both exotic species in the country. The information needs for these multi
purpose commercial mixed forests are varied and continuous, because their biological cycle is relatively short (8 to 18 years), and offer a wide range of possibilities in the timber products to obtain. Continuous forest survey in these cases, must consider processing information with a very detailed data collection system, which must be simple but efficient, to take the correct decision in management and final planning.
2.3.2 Information Needs
The first stage in the forest inventory design is to establish the levels of information according to the needs of the International Geographic Information Systems (GIS) developped at present.
A multistage level information is defined, which generally starts on the specie, classified into strata of ages, distributed in different geographic locations, and the minimum unit mapping area is the stand (Fig. 1 to 4).
I. Levels information
Specie
□
Age stratum0 Oo
First
Fig. 1. Information levels
Geo�raphic location
Oo
Sampling unitLast
. .
II. Level identification
Specie First level
Stratum of age Second level
�--s_p_ec_ie_A __ �l - 1�--sp _e
_c _ie
_z __ � First level
Fig. 2. Identification levels. First level.
Stratum of age I
Fig. 3. Identification levels. Second level.
Second level
Stratum of age II Stratum of age III
Geographic sector Third level Stand Fourth level Sampling units Fifth level
Third level Fourth level
D ���� � --- D
�-���-�---
__ __
(:)(:)
Geographic location
Stand Nr. 1
Stand Nr. n
Fig. 4. Identification levels. Third and fourth levels
2.3.3 Forest Inventory Sampling Design
A useful forest sampling design is based on the Bitterlich method, with circular plots distributed in a systematic reticular pattern, to collect data simply and rapidly. Two kinds of circular plots are commonly defined, according to the size of the forested areas: general plots, to calculate the mean stands and tree parameters, and variance of the estimations.
These general plot results are the basis to install the permanent plots, used to determine a complete quantitative evaluation into diameter and height classes, and all the stand parameters for sylvicultural management purposes (Fig. 5 to 7).
III. Forest inventory sampling design
Bitterlich circular plots
Sampling design:
Circular plots center located in a reticular sistematic pattern
General sampling units
Objectives:
To determine Average and standard deviation for main stand variables and establish distribution and location for the permanent sampling units
Permanent sampling units
Objectives:
To determine stand variables in diameter and commercial heights classes
Stand variables
Stand Nr. i
Fig. 6. General sampling units definition.
Stand variables
Stand Nr. i
Parameters
Vt: Total volume per hectare Vw: Wood volume per hectare Vp: Pulp volume per hectare Vs: Sawing volume per hectare
Vo: Other commercial volume per hectare
Parameters
Vt: Total volume per hectare into classes Vw: Wood volume per hectare into classes Vp: Pulp volume per hectare into classes Vs: Sawing volume per hectare into classes
Vo: Other commercial volume per hectare into classes Hi: Commercial heights (wood, pulp, sawing, others) FFi: Commercial form factors into classes
Fig. 7. Permanent sampling units definition.
2.3.4 Forest Inventory in Permanent Plots and Tree Measurements
Permanent circular plots located in a selective design, are identified by their center, and according to the Bitterlich principles method, increase their size in each consecutive measurement, simultaneously with tree diameter growth. Periodical measurements are given in these permanent plots, which frequency varies according to the age strata and precision information needs. Stand volume local tables for felled trees are prepared in a smaller sample into the circular permanent plot distribution, according to the variability condition of the geographic locations, soil characteristics and site index. The main variable tree models are developped from felled trees measurements, and related with the stand tree parameter estimations (Fig. 8 to 10).
IV. Forest inventory in permanent plots
/
Periodical measurements
�
Slond volume 1,ble,
m
Celled l,ees Variable trees modelsFig. 8. Purposes of forest Inventory in permanent units.
V. Tree measurements
Stand trees Ht: Total height Hw: Wood height Hp: Pulp height Hs: Sawing height Restrictions:
Hw, Hp: critical diameters Hs: critical diameters and form
Diameters measuwments reith Bitterlich Relaskop D.b.h. measurements: with calipers
Ht Hw
Hp Hs 1.30m
D.b.h.: diameter breast height Fig. 9. Measurements in standing trees.
Felled trees
Commercial portion
Crown
Commercial lengths
:A
Stump �
� ���1;�::o �o-=�03-0 ,.,. � -
-· ·,•·· - • Perpendicular diameters each meter ----.
Fig. 10. Measurements in felled trees.
2.3.5 Models for Stand Volume Tables
The four principal models are based on prediction of total and commercial height, form commercial factors (coefficients), commercial stand tree volume and conversion coefficients to correct stand up prediction with actual products results (Fig. 11 to 12).
VI. Models for stand volume tables
Heights Fonn factors
_,,,,,,,.. Stand trees Commercial volume ...__ Felled trees Conversion factors _,,,,,,,.. Stand trees ...__ Felled trees
Height models Heights (m) 45 42
39 36 33 30 27 24 21 18 15 12 9 6 3
Commercial volume for stand and felled trees Commercial volume (cubic meters)
3 2.5
2 1.5 -
1
0.5
o----�--�---�---�--� o----�--�---�---�--�
0 10 20 30
D.B.H of trees ( cm) 40 -- Total height -+- Commercial height
Factors form models Commercial factors form 0.95 1
0.85 0.9 0.75 0.8 0.65 0.7 0.55 0.6 0.45 0.5 0.35 0.4
50 0 10 20 30
D.B.H of trees (cm)
-+- Stand trees -- Felled trees
40
Conversion factors for different commercial volumes Conversion factors
* * * * * * * * **** *
50
0.3 -1--�-�-�-�-�-�--��
o----�--�---�---�--�
10 15 20 25 30 35 40 45 50 0 10
D.B.H of trees (cm) 20 30
D.B.H of trees (cm) 40 50 -- FF wood □ FF puls + FF sawing -- Commercial vol. 1
*
Commercial vol. 3 I I I Commercial vol. 2 Fig. 12. Tree models.Total Height:
Commercial Height:
Form Factors:
Commercial Volumes:
Conversion Factors:
Ht = e [a + b/(D.b.h.)) He = a + b -./ (D.b.h.) He = Commercial Heights FFc = a + b (D.b.h.) FFc = e [a + b/(D.b.h.))
FFc = Commercial Form Factors Ve = e [a + b/(D.b.h.)]
Ve = Commercial Volumes Vcs = e [a + b/(Vca)]
Vcs = a + b -./ (Vea)
Vcs = Commercial Stand volume Vcs = Commercial actual volume
2.3.6 Conclusions
Method is very simple and rapid and errors of estimation are corrected by coefficients calculated from periodical cuts, comparing predicted and obtained values. Errors of estimation are continuously updated for different kinds of products, and correction coefficients are included in the geographic processing software.
2.3. 7 References
COCHRAN, W.G., 1977: Sampling Techniques 3rd ed. New York. John Wiley and Sons. 428 pp.
FREESE, F., 1970: Metodos estadisticos elementales para tecnicos forestales. Mexico, CRAT.
SORRENTINO, A., 1983: Tablas locales de volumen comercial para las especies de pinos maritimo (Pinus pinaster Ait.), elliottii (Pinus elliottii Engelm. var. elliottii) y taeda (Pinus taeda L.). Boletin 108, Facultad de Agronomia. Universidad de la Republica, Montevideo. 37 pp.
SORRENTINO, A., 1984: Tecnicas e instrumentos de medicion forestal. 2 vol. Universidad de la Republica, Montevideo. 312 pp.
SORRENTINO, A., 1990: Rendimiento de especies forestales exoticas en el Uruguay. Boletin de Investigacion 27. Universidad de la Republica, Montevideo. 40 pp.
SO RR ENTINO, A., 1991: Indices de sitio preliminares para Ias principales especies forestales cultivadas en el Uruguay. Boletin de Investigacion 33. Universidad de la Republica, Montevideo.
30 pp.
SORRENTINO, A., 1992: Indices de Sitio, Volumetria y Crecimiento de Pinos y Eucaliptos en el Uruguay. Proyecto de Desarrollo Forestal Nacional. Contrato 14. Ministerio de Ganaderia, Agricultura y Pesca., Montevideo. 300 pp.
SORRENTINO, A., 1992: Un metodo rapido para estimaciones volumetricas en pie. Universidad de la Republica, Montevideo. Nota Tecnica 12. 20 pp.
SORRENTINO, A., 1994: Manual para Diseno y ejecucion de lnventarios Forestales. la ed.
Hemisferio Sur S.R.L. Montevideo, 500 pp.
