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Biomass and energy production in coppice stands of Vitex negundo L. in high density plantations on marginal lands
Biomass 19 (1989) 189-194
Biomass and Energy Production in Coppice Stands of Vitex negundo L. in High Density Plantations on Marginal Lands S. C. V e r m a & P. N. M i s r a National Botanical Research Institute, Lucknow 226 001, India (Received 27 September 1988; revised version received 30 January 1989; accepted 3 February 1989) ABSTRACT Productive potential of coppice stands of Vitex negundo L. have been evaluated under high density plantation on marginal lands of 25000 (density class A), 50000 (density class B) and 75 000 (density class C) plants ha-i. Better sprouting, increase in height, greater canopy spread and larger diameter of the main stem were observed to be mainly responsible for greater energy fixation at the level of 25 000 (density class A) plants ha - i Key words: Vitex negundo L., biomass, productivity, coppice, firewood, marginal lands, planting density, shrub.
INTRODUCTION Firewood crises have become a matter of great concern in the developing countries including the Indian subcontinent. This situation has arisen due to the indiscriminate cutting of forests. In order to overcome this problem, short rotation coppice forestry shows promise. Fastgrowing shrubs on wastelands may provide supplies of firewood at short intervals. V. negundo, commonly known as 'Nisinda' or 'Shambalu', is one such fast-growing shrub species which possesses tolerance to a wide range of soil conditions. The efficiency of solar energy conversion into chemical energy for net primary production ultimately governs the productive potential of any species. The evaluation of organic matter production is done in terms of energy production rather than dry matter determination. 189 Biomass 0144-4565/89/S03.50 -- © 1989 Elsevier Science Publishers Ltd, England. Printed in Great Britain
190
S. C Verma, P. N. Misra
In the present investigations, an attempt has been made to: (a) determine the calorific values of different plant components both as dry weight and on ash-free, dry weight basis, (b) estimate total energy fixation, and (c) calculate the energy conserving efficiency of coppice stands of V. negundo planted in high density plantations of 25 000, 50 000 and 75 000 plants ha -l. The results concerning biomass and energy production enable V. negundo to be evaluated as a fuelwood crop. MATERIAL AND METHODS Trials with certain promising shrubs have been underway at Banthra Research Station, situated at 26°52'N and 80°56'E, 161.5 m above sea level in a region where the monsoon is experienced. The climate during the study period was good. The present study is based on the growth behaviour of coppice stand of V. negundo and its effect on biomass and energy production under varying plant population per unit area, i.e. 25 000 (density class A) plants ha- 1, 50 000 (density class B) plants haand 75 000 (density class C) plants ha -~. These were adjusted by uniform inter- and intra-row distances of 63.2, 45.0 and 36.5 cm, respectively. Observations were recorded on emergence and survival of sprout from both the cut and left over stumps (15 cm high) of a one-yearold stand. Height and diameter of individual sprouts on each plant were recorded along with canopy spread. Sample plants were selected from among the total plant population in respective density classes on the basis of average values of height and stem diameter, canopy spread and number of sprouts per plant. Only aerial biomass was estimated by felling the sample plant, 1 the below-ground biomass was not estimated. Different plant components were separated for estimation of dry matter accumulation. Samples were oven dried at 80°C for 48 h and the biomass calculated. These samples were used to determine the calorific values using an oxygen bomb calorimeter. The total energy values per plant are expressed as kJ tree-~ for all three density classes. The energy retention, energy conserving efficiency (ECE) and the energy of the standing crop were also calculated. Solar energy was measured using a solarimeter for calculating energy conserving efficiency. Litter was collected by the litter trap method. RESULTS AND DISCUSSION The influence of spacing on growth behaviour is shown in Table 1; this indicates that sprout height, canopy spread and diameter of the main
No. of sprouts
B
C
50 000
75 000
Mean SE
A
25 000
36"5
45.0
63"2
(em)
7"3 + 0-9
9-0 •+0"7 7"0 _+0"7 6"0 _+0-0 6-3 -+ 0'9
8"0 -+0"4 6'0 +0'5 5-0 -+ 0"0
Class Grid Emerged Survived No. of plants ha- i spacing
Density
112"9 _+7.7
128"3 _+ 12'7 106'9 + 10-7 103-6 _+6"8
(cm)
96"6 _+4"3
0"9 _+0-04
97"0 1"0 _+4-6 _+0"07 104"0 0-9 _+8-1 -+0"06 89'0 0"8 -+ 5'3 -+ 0'03
(cm)
Height of Canopy Diameter sprouts spread (cm) Twig Leaves
Total
142'2 •+ 1 3 ' 6
53'1 -+4.3
68-5 263'7 _+7-9 -+18-5
167"9 59"0 59'6 286"5 •+10"9 _+14-6 _ + 7 " 3 -+9"0 137"6 55"8 84.3 277'7 •+16"1 +15"6 -+12"5 -+20'1 121"1 44"6 61-7 227"4 _+7"7 _+4"4 _ + 7 - 1 +9-4
Stem
Standing biomass (g/tree - ~)
95"2 _+10"0
111"2 _+9"1 97"6 -+8"3 76"7 -+6"6
358-9 _+28"3
397"7 + 10"5 375"3 + 17"2 303-8 + 12"9
Litter Total production accumulated (g) biomass (g)
TABLE 1 Growth Behaviour and Standing Biomass Production in V. negundo in High Density Plantations
<
O
e,.
Ash (%)
3"0
2-6
9.4
7.5
6"9
---
Plant components
Stem
Twig
Leaves
Fruit
Litter
Mean SE
20-0 _+0"5
21.6 +_0.4 20"9 +0.5 19-4 _+0.1 21"6 +_0.1 16-4 +_0.2
Dry weight basis
21-2 _+0"5
22.2 +_0.4 21.5 _+0-5 21-4 _+0.1 23"3 -+0-1 17-6 _+0.2
Ash-free dry weight basis
Energy value (kJ g i)
Density class A
---
6.9
7.2
9.0
2.2
2.5
Ash (%)
19-1 +_0"5
20.4 _+0.1 19.5 _+0-1 10.0 _+0.1 20"9 +_0-1 15"9 _+0.1
Dry weight basis
20.3 _+0-5
21'1 +_0.1 20.0 _+0.1 20-9 _+0.1 22"5 _+0.1 17"0 _+0.1
Ash-free dry weight basis
Energy value (kJ g- i)
Density class B
---
6.8
7"0
8.8
2-2
2.4
Ash (%)
18.1 _+0"6
19-6 +_0.1 18"3 +_0.2 18-7 _+0-1 19.7 +0.1 13.9 -+0-1
Dry weight basis
19.1 _+0"6
20-1 +_0.1 18.7 _+0.2 20-5 _+0"1 21-3 _+0-1 14.9 _+0.1
Ash-free dry weight basis
Energy value (kJ g- i)
Density class C
TABLE 2 Energy Content of Different Plant Components of V. negundo in High Density Plantation (kJ g ~dry wt and kJ g t ash-free dry wt)
~O t,o
Class
A B C
A B C
No. of plants ha- I
25 000 50 000 75 000
25 000 50 000 75 000
Density
63'2 45"0 36"5
63'2 45"0 36-5
Grid spacing (cm)
0"9 1"5 1-8
3"7 2"9 2'4
Stem
Leaves
Total
1"3 1-8 1"3
6-3 5"8 4"5
0"3 0"5 0"6
0"3 0"9 1"0
1"5 2"9 3"4
Energyfixation (105 MJ ha- i)
1"3 1'1 0'8
Energyfixation (105 MJ tree i)
Twig
0'5 0-8 0"8
2"0 1"7 1"1
Litter
2'0 3"7 4"2
8"3 7"5 5-6
Total accumulation
m
5 342 6 054 4 487
Total solar energy per tree canopy (MJ)
m
B
0"31 0"25 0"25
Energy conserving efficiency (%)
TABLE 3 Energy Fixation and Energy Conserving Efficiency (ECE) in V. negundo in High Density Plantations (energy values on the basis of ashfree dry weight; annual basis)
~J
¢)
2"
e~ 0
Uo
<
194
S. C. Verma, P. N. Misra
stem were maximum in density class A, where the spacing was 63.2 cm both for inter- and intra-row distances. Better performance has contributed to a greater quantity of organic matter in 25 000 (density class A) plants ha- t as compared to that of density classes B and C. Among different plant components, the highest calorific values were recorded in fruit, followed by stem, twigs, leaves and litter. This trend was common in all the density classes. Calorific values on the basis of ash-free dry weight were higher than the dry weight as the ash contents (incombustible foreign material) bias the data towards a lower value (Table 2). These values are comparable to those found for Moringa oleifera and Moringa concanensis. 2 As a result of greater biomass production and energy reserves in plants under density class A, maximum energy fixation was recorded as compared to classes B and C (Table 3). The E C E of plants belonging to density class A was 1.24 times higher than density classes B and C because of sufficient availability of nutrients, light and water. The prolific regeneration capacity of this shrub after coppicing can be utilized even under high density populations of 50 000 plants ha- ~. At greater densities, productivity tends to fall sharply at the level of 75 000 plants ha- ~ as a result of the failure of sprouts to grow after emergence due to lack of solar radiation and nutrients. This results in reduced height and girth of sprouts and ultimately of biomass in higher density class C of 75 000 plants haVitex negundo, being a fast-growing shrub, finds its use is as a potential firewood crop among the vast rural population which depends upon the twigs and shrubs to meet domestic requirements of energy. This shrub after coppicing can be utilized at high densities of 50 000 plants ha- i. However, closer spacing does not seem to be conducive to greater biomass production.
ACKNOWLEDGEMENT The authors are grateful to Director Dr P. V. Sane for providing the facilities. REFERENCES 1. Baskerville, G. L., Dry matter production in immature fir stands. Forest Sci. Monogr., 9 (1965) 1-42. 2. Verma, S. C., Ecological studies of Moringa oleifera Lamk. and M. concanensis Nimmo, with special emphasis on organic production and mineral status. PhD thesis, Gorakhpur University, Gorakhpur, India, 1977.
Biomass and Energy Production in Coppice Stands of Vitex negundo L. in High Density Plantations on Marginal Lands S. C. V e r m a & P. N. M i s r a National Botanical Research Institute, Lucknow 226 001, India (Received 27 September 1988; revised version received 30 January 1989; accepted 3 February 1989) ABSTRACT Productive potential of coppice stands of Vitex negundo L. have been evaluated under high density plantation on marginal lands of 25000 (density class A), 50000 (density class B) and 75 000 (density class C) plants ha-i. Better sprouting, increase in height, greater canopy spread and larger diameter of the main stem were observed to be mainly responsible for greater energy fixation at the level of 25 000 (density class A) plants ha - i Key words: Vitex negundo L., biomass, productivity, coppice, firewood, marginal lands, planting density, shrub.
INTRODUCTION Firewood crises have become a matter of great concern in the developing countries including the Indian subcontinent. This situation has arisen due to the indiscriminate cutting of forests. In order to overcome this problem, short rotation coppice forestry shows promise. Fastgrowing shrubs on wastelands may provide supplies of firewood at short intervals. V. negundo, commonly known as 'Nisinda' or 'Shambalu', is one such fast-growing shrub species which possesses tolerance to a wide range of soil conditions. The efficiency of solar energy conversion into chemical energy for net primary production ultimately governs the productive potential of any species. The evaluation of organic matter production is done in terms of energy production rather than dry matter determination. 189 Biomass 0144-4565/89/S03.50 -- © 1989 Elsevier Science Publishers Ltd, England. Printed in Great Britain
190
S. C Verma, P. N. Misra
In the present investigations, an attempt has been made to: (a) determine the calorific values of different plant components both as dry weight and on ash-free, dry weight basis, (b) estimate total energy fixation, and (c) calculate the energy conserving efficiency of coppice stands of V. negundo planted in high density plantations of 25 000, 50 000 and 75 000 plants ha -l. The results concerning biomass and energy production enable V. negundo to be evaluated as a fuelwood crop. MATERIAL AND METHODS Trials with certain promising shrubs have been underway at Banthra Research Station, situated at 26°52'N and 80°56'E, 161.5 m above sea level in a region where the monsoon is experienced. The climate during the study period was good. The present study is based on the growth behaviour of coppice stand of V. negundo and its effect on biomass and energy production under varying plant population per unit area, i.e. 25 000 (density class A) plants ha- 1, 50 000 (density class B) plants haand 75 000 (density class C) plants ha -~. These were adjusted by uniform inter- and intra-row distances of 63.2, 45.0 and 36.5 cm, respectively. Observations were recorded on emergence and survival of sprout from both the cut and left over stumps (15 cm high) of a one-yearold stand. Height and diameter of individual sprouts on each plant were recorded along with canopy spread. Sample plants were selected from among the total plant population in respective density classes on the basis of average values of height and stem diameter, canopy spread and number of sprouts per plant. Only aerial biomass was estimated by felling the sample plant, 1 the below-ground biomass was not estimated. Different plant components were separated for estimation of dry matter accumulation. Samples were oven dried at 80°C for 48 h and the biomass calculated. These samples were used to determine the calorific values using an oxygen bomb calorimeter. The total energy values per plant are expressed as kJ tree-~ for all three density classes. The energy retention, energy conserving efficiency (ECE) and the energy of the standing crop were also calculated. Solar energy was measured using a solarimeter for calculating energy conserving efficiency. Litter was collected by the litter trap method. RESULTS AND DISCUSSION The influence of spacing on growth behaviour is shown in Table 1; this indicates that sprout height, canopy spread and diameter of the main
No. of sprouts
B
C
50 000
75 000
Mean SE
A
25 000
36"5
45.0
63"2
(em)
7"3 + 0-9
9-0 •+0"7 7"0 _+0"7 6"0 _+0-0 6-3 -+ 0'9
8"0 -+0"4 6'0 +0'5 5-0 -+ 0"0
Class Grid Emerged Survived No. of plants ha- i spacing
Density
112"9 _+7.7
128"3 _+ 12'7 106'9 + 10-7 103-6 _+6"8
(cm)
96"6 _+4"3
0"9 _+0-04
97"0 1"0 _+4-6 _+0"07 104"0 0-9 _+8-1 -+0"06 89'0 0"8 -+ 5'3 -+ 0'03
(cm)
Height of Canopy Diameter sprouts spread (cm) Twig Leaves
Total
142'2 •+ 1 3 ' 6
53'1 -+4.3
68-5 263'7 _+7-9 -+18-5
167"9 59"0 59'6 286"5 •+10"9 _+14-6 _ + 7 " 3 -+9"0 137"6 55"8 84.3 277'7 •+16"1 +15"6 -+12"5 -+20'1 121"1 44"6 61-7 227"4 _+7"7 _+4"4 _ + 7 - 1 +9-4
Stem
Standing biomass (g/tree - ~)
95"2 _+10"0
111"2 _+9"1 97"6 -+8"3 76"7 -+6"6
358-9 _+28"3
397"7 + 10"5 375"3 + 17"2 303-8 + 12"9
Litter Total production accumulated (g) biomass (g)
TABLE 1 Growth Behaviour and Standing Biomass Production in V. negundo in High Density Plantations
<
O
e,.
Ash (%)
3"0
2-6
9.4
7.5
6"9
---
Plant components
Stem
Twig
Leaves
Fruit
Litter
Mean SE
20-0 _+0"5
21.6 +_0.4 20"9 +0.5 19-4 _+0.1 21"6 +_0.1 16-4 +_0.2
Dry weight basis
21-2 _+0"5
22.2 +_0.4 21.5 _+0-5 21-4 _+0.1 23"3 -+0-1 17-6 _+0.2
Ash-free dry weight basis
Energy value (kJ g i)
Density class A
---
6.9
7.2
9.0
2.2
2.5
Ash (%)
19-1 +_0"5
20.4 _+0.1 19.5 _+0-1 10.0 _+0.1 20"9 +_0-1 15"9 _+0.1
Dry weight basis
20.3 _+0-5
21'1 +_0.1 20.0 _+0.1 20-9 _+0.1 22"5 _+0.1 17"0 _+0.1
Ash-free dry weight basis
Energy value (kJ g- i)
Density class B
---
6.8
7"0
8.8
2-2
2.4
Ash (%)
18.1 _+0"6
19-6 +_0.1 18"3 +_0.2 18-7 _+0-1 19.7 +0.1 13.9 -+0-1
Dry weight basis
19.1 _+0"6
20-1 +_0.1 18.7 _+0.2 20-5 _+0"1 21-3 _+0-1 14.9 _+0.1
Ash-free dry weight basis
Energy value (kJ g- i)
Density class C
TABLE 2 Energy Content of Different Plant Components of V. negundo in High Density Plantation (kJ g ~dry wt and kJ g t ash-free dry wt)
~O t,o
Class
A B C
A B C
No. of plants ha- I
25 000 50 000 75 000
25 000 50 000 75 000
Density
63'2 45"0 36"5
63'2 45"0 36-5
Grid spacing (cm)
0"9 1"5 1-8
3"7 2"9 2'4
Stem
Leaves
Total
1"3 1-8 1"3
6-3 5"8 4"5
0"3 0"5 0"6
0"3 0"9 1"0
1"5 2"9 3"4
Energyfixation (105 MJ ha- i)
1"3 1'1 0'8
Energyfixation (105 MJ tree i)
Twig
0'5 0-8 0"8
2"0 1"7 1"1
Litter
2'0 3"7 4"2
8"3 7"5 5-6
Total accumulation
m
5 342 6 054 4 487
Total solar energy per tree canopy (MJ)
m
B
0"31 0"25 0"25
Energy conserving efficiency (%)
TABLE 3 Energy Fixation and Energy Conserving Efficiency (ECE) in V. negundo in High Density Plantations (energy values on the basis of ashfree dry weight; annual basis)
~J
¢)
2"
e~ 0
Uo
<
194
S. C. Verma, P. N. Misra
stem were maximum in density class A, where the spacing was 63.2 cm both for inter- and intra-row distances. Better performance has contributed to a greater quantity of organic matter in 25 000 (density class A) plants ha- t as compared to that of density classes B and C. Among different plant components, the highest calorific values were recorded in fruit, followed by stem, twigs, leaves and litter. This trend was common in all the density classes. Calorific values on the basis of ash-free dry weight were higher than the dry weight as the ash contents (incombustible foreign material) bias the data towards a lower value (Table 2). These values are comparable to those found for Moringa oleifera and Moringa concanensis. 2 As a result of greater biomass production and energy reserves in plants under density class A, maximum energy fixation was recorded as compared to classes B and C (Table 3). The E C E of plants belonging to density class A was 1.24 times higher than density classes B and C because of sufficient availability of nutrients, light and water. The prolific regeneration capacity of this shrub after coppicing can be utilized even under high density populations of 50 000 plants ha- ~. At greater densities, productivity tends to fall sharply at the level of 75 000 plants ha- ~ as a result of the failure of sprouts to grow after emergence due to lack of solar radiation and nutrients. This results in reduced height and girth of sprouts and ultimately of biomass in higher density class C of 75 000 plants haVitex negundo, being a fast-growing shrub, finds its use is as a potential firewood crop among the vast rural population which depends upon the twigs and shrubs to meet domestic requirements of energy. This shrub after coppicing can be utilized at high densities of 50 000 plants ha- i. However, closer spacing does not seem to be conducive to greater biomass production.
ACKNOWLEDGEMENT The authors are grateful to Director Dr P. V. Sane for providing the facilities. REFERENCES 1. Baskerville, G. L., Dry matter production in immature fir stands. Forest Sci. Monogr., 9 (1965) 1-42. 2. Verma, S. C., Ecological studies of Moringa oleifera Lamk. and M. concanensis Nimmo, with special emphasis on organic production and mineral status. PhD thesis, Gorakhpur University, Gorakhpur, India, 1977.