The Concept of Site and The Growing Stock

THE CONCEPT OF SITE (THE GROWING STOCK)

·       Site has been defined as:
     “An area considered in terms of its environment, particularly as this determines the type and quality of the vegetation the area can carry”.
·       In the works SITE is the resultant of the interaction of such factors as Rainfall, Temperature physical and chemical characteristics of the soil and the incidence of biotic factors affecting growth as fiber, grazing, and lopping.
·       Sites are classified as either qualifiedly is their climate, soil, and vegetation into “SITE TYPES” OR quantitatively potential wood production into “SITE CLASSES”.
·       The productive machinery of the forest comprises two major components.
     1.       The site.
     2.       The growing stock
·       The site supplies Raw materials necessary for the growth of tree i.e. solar radiation, carbon dioxide, soil waste, soil oxygen (aeration) and several macro and micronutrients.
·       The growing stock constitutes the factory, which produces wood by the process of photosynthesis.
·       The amount of wood product depends upon the quality of the site and the attribute of the growing stock.

SIGNIFICANCE OF SITE QUALITY IN MANAGEMENT

·       Site quality has important implication for management.
·       A lesser area of a high site quality has the same potential wood production as a much larger area of lower site quality.
·       Moreover exploitable sizes are attained much sooner on higher than on lower site qualities, enabling shorter rotation to be practiced.
E.G. (A)
TOTAL YIELD OF CFT PER AREA IS 100EARS
Site quality
Species
1. Deodar
17,790 cft
1. Chir
19,430 cft
2. –do-
14,760 cft
2. –do-
12,870 cft
3. –do-
10,150 cft
3. –do-
8938 cft
Srisram-age 20 years
1. Kail
22,715 cft
1. 3348 cft
2. –do-
17,835 cft
2. 2568 cft
3. –do-
13,185 cft
3. 1642 cft.
E.G. (B)
Sie Quality
Species
Age
Dia (dbR).
1.
Deodar
90
18
2.
-do-
130
18
3.
-do-
140
14
1.
Kail
70
18
2.
-do-
90
18
3.
-do-
130
18
1.
Chir
70
18
2.
-do-
90
18
3.
-do-
105
18
Species
Quality class
Rotation
(years)
Final yield/Acre
(cft)
Kail
1
70
12,340 cft
-do-
2
90
12,250 cft
-do-
3
130
12,800 cft
·       To sum up, site quality profoundly influence the economics of forestry through both its effect on volume yield per unit area and on the length of time it takes the trees to reach an exploitable size, e.g.
     In a plantation, the same volume of wood can be produced from half the area if it is site quality 1 rather than 2.
·       The forestry would be more profitable because the OUTPUT per unit area would be greatly increased without any change in the level of INPUTS.
·       Forests on better sites can be worked out on shorter rotations thirdly producing earlier returns on the capital invested

IDENTIFICATION OF SITE QUALITY

·       To distinguish the various sites qualities the following major approaches in use for this purpose.
1)  Volume per acre at rotation age.
2)  Physiography and soil.
3)  Ground vegetation
4)  The height of dominant and co-dominant.
·       Height and diameter are the two major determinants of tree volume. It is therefore universally used for site quality determination in forestry practices.

SITE QUALITIES RECOGNIZED IN PAKISTAN

·       Site in our forestry practice is determined from the Age/height curve of the yield table e.g. site qualities.
S. No
Species
Age (Years)
QUALITIES (TOP HEIGHT IN FEET)
I
II
III
1.
Pinus roxburgiii
100
138-114
114-91
91-72
2.
P. wallichina
90
140-120
120-100
100-80
3.
Exdrus deodara
120
140-120
120-100
100-80
4.
Dalbergia sissoo
20
75-65
65-55
55-45

MODIFICATION OF SITE QUALITY (IMPROVEMENT)

·       Site productivity or quality can be modified improved by several practices e.g.
1)  Irrigation/soil moisture.
2)  Chemical fertilizers/farm yard manure
3)  Drainage.
4)  Soil aeration.

CONCEPT OF SITE

·       The site quality is the measure of the Relative productive capacity of a site for particular species.
·       It is the capacity of the area to produce forests or other vegetation.
·       The site quality is also called.
     QUALITY CLASS, OR
     QUALITY OF LOCALITY, OR
     SITE CLASS, OR
     LOCALITY CLASS.
·       Although it is the cumulative effect of various locality and biological factors e.g. Soil, Temperature, precipitation biotic interference, Erosion, Aspect, Soil moisture etc. But the basis of Top Height of the crop.
·    The top height which varies with age of the crop is generally the basis for classification of site quality

MAINTENANCE AND IMPROVEMENT OF SITE

·       The site quality of an area can be improved by improving various factors such as.
     Moisture Regime, Nutrient status, Soil depth, Soil aeration, Soil porosity and drainage.

DETERMINATION OF SITE QUALITY EVALUATION

·       The site quality is written by Roman Numeral e.g.
     I, II, III, IV, V, etc.
·       In order to determine/evaluate the site quality the crop is grouped into various height or diameter-age classes.
·       The following table gives the measure of different site quality 2, 3 for chir and deodar species.

(A) CHIR:-

S. NO.
AGE (YEARS)
HEIGHT (METER) FOR SITE QUALITY
1
10
4.47
3.2
2.4
2
20
9
6
5
3
30
14
10
7
4
40
19
14
10
5
50
24
21
13
6
80
34
27
21

(B)     DEODAR:

S. NO.
AGE (YEARS)
HEIGHT (METER) FOR SITE QUALITY
1
10
3
2.1
0.5
2
20
8
6
4
3
30
14
10
7
4
40
20
14
10
5
50
24
18
13
6
80
31
26
30
·       Top height for Pinus roxburgi                 100 Years
               For Cedrus deodara                    120 Years
     Is reached at ages of 100 and 120 years respectively.
·       Improvement in site quality is achieved by adopting various silvicultural operations.
·       The various practices that improve the site quality include improvement of.
     Light condition, Soil Moisture, Soil cover, Water-table, Rae of decomposition of organic matter and control of several biotic factor (fire, grazing and browsing etc.).
·       With the improvement of in site quality the conditions are created for better growth of trees, watershed improvement, develop of wildlife, recreation facilities and other aspects of management.
·       The site quality varies with a number of tree/ hectare or the intensity of thinning as example field in the following table.
TABLE: Age, Quality and crop height of Deodar.
Species
Crop age in years
Site quality
Crop height in meters
E-grade
D-grade
C-grade
Deodar
140
1
45.16
43.9
42.7
2
39.3
37.8
36.3
·       The purpose of site Quality is to predict the timber yield of a given species, which is growing on the site.
     Height or rate of growth is the only known parameter of the site index.
·       The average height of the tallest trees of an avenged stand at the age of 50 years in taken as the standard for this purpose.
·       Index age is 50 years.
·       This position is found by Extrapolating age Vs Height curve.
·       This site Quality class, not more than five or six are detonated by roman numerals.
·       It is hard to predict the site quality where there is no forest of vegetation on the site. In such situation quality class is determined by measuring various soil properties and other site factors such as aspect or Degree of the slope.
·       The physical and chemical properties of soil, the depth and nature of depth and nature of hardpan etc are necessary to know for measuring site quality.
·       The determination of site quality helps in deciding which species or provenances should be planted on the given area.

DALBERGIA SISSOO (SHISHAM)

·       Age 50 year (rotation)
·       Density of 200 stems per hectare
·       Sites 3 site qualities
SITE QUALITY
AVERAGE CROP DIA (CM)
TOP HEIGHT(M) MAX-MIN
BASAL AREA (M2/Ha)
1
35.0
28 – 24.3
19.289
2
30.1
24.3 – 17.0
14.222
3
16.7
20.7 – 17.0
4.403

EUCALYPTUS TERETICORNIS

1
3
5
AGE
AV.HT
AV.DIA
AV.HT
A.DIA
AV.H
A.DIA
5
15.2
11.5
10.5
8.0
6.1
4.7
6
16.5
12.5
11.6
8.8
6.8
5.2
7
17.2
13.0
12.2
9.3
7.5
5.54
8
17.6
13.5
12.7
9.6
7.7
5.8
9
18.3
13.8
13.1
9.9
8.0
6.0
10
18.6
14.0
13.4
10.2
8.3
6.3
12
19.0
14.4
13.9
1.5
8.7
6.6
15
19.5
14.7
14.3
10.8
9.2
6.9

 

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