Chapter four
Results and discussions
The result and discussion of this tropics are describe under two section named Species composition and Quantitative structure that will give tree diversity of the area.
For this tropic, all the data are secondary which we collected from the seminar library.
4.1 Tree composition of Tilagarh Eco-park, Sylhet:
Total 504 individual tree stems of 18 families were identified.
TABLE. 4.1 Tree composition of Tilagarh Eco-park, Sylhet
| Family | Scientific name | Local name |
| 1. Anacardiaceae | Mangifera indica Linn | Am |
| 2. Apocynaceae | Alstonia scholaris R. Br. | Satim |
| 3. Averrhoaceae | Averrhoa carambola Linn | Kamranga |
| 4. Casuarinaceae | Casuarina lattorea Linn | Jhau |
| 5. Combretaceae | Terminalia arjuna W&A Terminalia belerica Terminalia chebula Retz | Arjun Bohera Hortoki |
| 6. Dipterocarpaceae | Dipterocarpus turbinatus Gaertn Shorea rabusta Gaertn | Garjan Sal |
| 7. Euphorbiaceae | Phyllanthus emblica Linn | Amloki |
| 8. Guttiferae | Mesua ferrea | Nageshar |
| 9. Leguminosae | Cassia siamea Lamk Acacia auricoliformis Willd Samania saman | Minjiri Akash moni Rain tree |
| 10. Lythraceae | Lagerstroemia speciosa | Jarul |
| 11. Magnoliaceae | Michelia champaca Linn | Champa |
| 12. Meliaceae | Swietenia mahagoni (L.) Jacq Meliaceae sempervirens linn All | Mhagoni Bokhin |
| 13. Moraceae | Artocarpus chaplasha Roxb Artocarpus heterophyllus Lamk Ficus roxburghii | Chapalish Kanthal Dumur |
| 14. Myrtaceae
| Syzygium grande (Wt) Walop Eucalyptus camaldulensis Dihn | Dhakijum Eucalyptus |
| 15. Palmae | Cocos nucifera Linn | Narikal |
| 16. Sapotaceae | Mimusops elengi Linn | Bokul |
| 17. Thymeleaceae | Aquilaria agalocha Robx | Agor |
| 18. Verbenaceae | Tectona grandis | Teak |
The family Combretaceae Leguminosae Moraceae are dominant containing three species followed by Dipterocarpaceae Meliaceae Myrtaceae (two species). The remaining families contained only one species each (Table 4.1). Similar study was done by Nath (1995), in the Sitapahar natural forest of Bangladesh, were found 86 tree species of 36 families. Another study also done by Hossain (1994) in the Bamu natural forest, Bangladesh was found 89 tree species of 31 families. Alamgir and Al-amin (2005) was found 32 tree species of 15 families at Bamer chara and Daner chara under Banskhali upazila, Chittagong. Compare with both it can say Tilagarh Eco-park is a good composition of trees.
4.2 Present tree stock of Tilagarh Eco-Park:
To understand the present stock of the study area, number of stems per hectare, Basal area per hectare, height and diameter classes was measured.
4.2.1 Number of stems per hectares : The number of stems per hectare was found 1678. Considering number of stems per hectare the dominant five species are
1. Shorea rabusta Gaertn (653)
2. Dipterocarpus turbinatus Gaertn (490)
3 Michelia champaca Linn (143)
4. Artocarpus chaplasha Roxb (97)
5. Lagerstroemia speciosa (83)
Rahman et al. (2000) estimated that 1678 stems/ha with dbh ≥5cm in Chunati Wildlife Sanctuary of Chittagong forest division. Alamgir and Al-amin (2005) was found 590 stems/ha at Bamer chara and Daner chara under Banskhali upazila, Chittagong,(Alamgir and siful, 2007) was found 524 stems/ha in Khadimnagor National Park,Sylhet.Comparing with those research findings, Tilaghor Eco-Park is well diverse and better stocked forest.
Table 4.2 Tree stems/ha and basal area/ha of tree species in Tilagarh Eco-Park
| Sl no | S Name | L N | Stem/ha | B A /ha (m²) |
| 1. | Acacia auricoliformis Willd | Akash moni | 17 | 0.269 |
| 3. | Alstonia scholaris R. Br. | Satim | 3 | 0.052 |
| 4. | Aquilaria agalocha Robx | Agor | 30 | 1.175 |
| 5. | Artocarpus chaplasha Roxb | Chapalish | 97 | 14.03 |
| 6. | Artocarpus heterophyllus Lamk | Kanthal | 13 | 0.194 |
| 7. | Averrhoa carambola Linn | Kamranga | 3 | 0.025 |
| 8. | Cassia siamea Lamk | Minjiri | 57 | 1.168 |
| 9. | Casuarina lattorea Linn | Jhau | 3 | 0.028 |
| 10. | Cocos nucifera Linn | Narikal | 3 | 0.075 |
| 11. | Dipterocarpus turbinatus Gaertn | Garjan | 490 | 47.96 |
| 13. | Eucalyptus camaldulensis Dihn | Eucalyptus | 7 | 0.065 |
| 14. | Ficus roxburghii | Dumur | 7 | 0.043 |
| 15. | Lagerstroemia speciosa | Jarul | 83 | 2.507 |
| 16. | Mangifera indica Linn | Am | 7 | 0.162 |
| 17. | Meliaceae sempervirens linn All | Bokhin | 3 | 0.013 |
| 18. | Mesua ferrea | Nageshar | 7 | 0.047 |
| 19. | Michelia champaca Linn | Champa | 143 | 12.28 |
| 20. | Mimusops elengi Linn | Bokul | 3 | 0.014 |
| 12. | Phyllanthus emblica Linn | Amloki | 3 | 0.038 |
| 2. | Samania saman | Rain tree | 10 | 0.251 |
| 21. | Shorea rabusta Gaertn | Sal | 653 | 48.08 |
| 22. | Swietenia mahagoni (L.) Jacq | Mhagoni | 7 | 0.091 |
| 23. | Syzygium grande (Wt) Walop | Dhakijum | 3 | 0.018 |
| 24. | Tectona grandis | Teak | 13 | 0.286 |
| 25. | Terminalia arjuna W&A | Arjun | 7 | 0.083 |
| 26. | Terminalia belerica | Bohera | 3 | 0.095 |
| 27. | Terminalia chebula Retz | Hortoki | 3 | 0.018 |
| Total |
|
| 1678
| 129.1
|
4.2.2 Basal area per hectare:
Total basal area per hectare of trees was 129.1 m² .From the basal area point of view’ the five dominant species were Shorea rabusta Gaertn (48.08 m²/ha), Dipterocarpus turbinatus Gaertn (47.96m²/ha), Artocarpus chaplasha Roxb (14.03m²/ha) Michelica champaca(12.28m²/ha)& Lagerstroemia speciosa (2.507m²/ha) . Though the number of stems of Artocarpus chaplasha Roxb (29) is lower then Michelia champaca Linn (43) but the basal area is higher than Michelia champaca Linn due to trees of Artocarpus chaplasha Roxb are greater in dbh than those .Nath (1995) and Hossain (1994) were estimated 55.22 m2/ha in the Sitapahar natural forest and 41.81m2/ha at Bamu reserve forest with dbh greater than 10cm respectively. Another study also done by Alamgir (2003) was found 1.415 m2 at Bamer chara and Daner chara under Banskhali upazila, Chittagong., the basal area/ha of trees of Khadimnagor National Park is 60.144m².,(Alamgir and siful, 2007) Comparing to the above findings it must be said that Tilagarh is good enough.
Fig: Stems/ha and Basal area/ha of five dominant tree species of Tilaghor Eco-Park
NB: Series 1 stem/ha and Series 2 Basal area/ha
4.2.3 Distribution of individuals in different diameter (cm) classes in number:
Most of the trees 291 out of 504 belong to the diameter class of ≥29cm and the least number of trees 4 were present in the diameter class of 5-8.99cm. The distributions of dominated species in different diameter classes were different except 5-8.99cm 9-12.99 and 13-16.99 cm diameter classes where Shorea rabusta Gaertn is dominant table 4.3
Distribution of individual species using diameter classes in number:
| S N | Diameter class (cm) | ||||||||
| 5-8.99 | 9-12.99 | 13-16.99 | 17-20.99 | 21-24.99 | 25-28.99 | ≥29 | Total no stem | ||
| Acacia auricoliformis Willd | 1 | 4 |
|
|
|
| 5 | ||
| Alstonia scholaris R. Br. |
|
|
| 3 |
|
|
| 3 | |
| Aquilaria agalocha Robx |
|
| 1 |
|
|
|
| 1 | |
| Artocarpus chaplasha Roxb |
|
|
| 4 | 3 | 1 | 1 | 9 | |
| Artocarpus heterophyllus Lamk |
|
|
|
|
| 8 | 21 | 29 | |
| Averrhoa carambola Linn |
|
| 4 |
|
|
|
| 4 | |
| Cassia siamea Lamk |
| 1 | 11 | 4 | 1 |
|
| 17 | |
| Casuarina lattorea Linn |
| 1 |
|
|
|
|
| 1 | |
| Cocos nucifera Linn |
|
| 1 |
|
|
|
| 1 | |
| Dipterocarpus turbinatus Gaertn |
|
|
| 8 |
| 18 | 121 | 147 | |
| Eucalyptus camaldulensis Dihn |
| 1 |
|
|
|
|
| 1 | |
| Ficus roxburghii | 2 |
|
|
|
|
| 2 | ||
| Lagerstroemia speciosa | 1 | 1 |
|
|
|
|
| 2 | |
| Mangifera indica Linn | 1 |
|
|
|
|
|
| 1 | |
| Meliaceae sempervirens linn All |
|
| 1 |
|
|
|
| 1 | |
| Mesua ferrea |
| 1 | 9 | 6 | 5 | 4 |
| 25 | |
| Michelia champaca Linn |
|
| 1 | 1 |
|
|
| 2 | |
| Mimusops elengi Linn |
| 1 | 1 |
|
|
|
| 2 | |
| Phyllanthus emblica Linn |
|
|
| 4 | 8 | 4 | 27 | 43 | |
| Samania saman | 1 |
|
|
|
|
|
| 1 | |
| Shorea rabusta Gaertn |
|
|
| 37 | 16 | 22 | 121 | 196 | |
| Swietenia mahagoni (L.) Jacq |
| 1 | 1 |
|
|
|
| 2 | |
| Syzygium grande (Wt) Walop |
|
| 1 |
|
|
|
| 1 | |
| Tectona grandis |
| 1 | 2 | 1 |
|
|
| 4 | |
| Terminalia arjuna W&A |
| 2 |
|
|
|
|
| 2 | |
| Terminalia belerica |
|
|
| 1 |
|
|
| 1 | |
| Terminalia chebula Retz | 1 |
|
|
|
|
|
| 1 | |
| Total | 4 | 13 | 37 | 69 | 33 | 57 | 291 | 504 | |
Table 4.3 also shows that 4 trees possess in class 5- 8.99, 13 trees possess in class 9- 12.99, 37 trees possess in class 13- 16.99, 69 trees possess in class 17- 20.99, 33 trees possess in class 21- 24.99, 57 trees possess in class 25- 28.99 and 291 trees possess in class ≥29
Fig Distribution of the number of individuals and species in diameter classes.
Figure illustrates the species distribution in different diameter classes. Highest species numbers were present in the diameter class ≥29cm. 12 species present in the diameter class 13-16.99cm.
4.2.4 Distribution of individuals in different height (m) classes in number
Most of the trees 120 out of 504 belong to the height class of 13-16.99m and the least number of trees 35 were present in the height class of ≥29m The distributions of dominated species in different eight classes were different except 21-24.99,25-28.99,and ≥29m.here Shorea rabusta Gaertn is dominant
Table 4.4 Number of stem distribution of individual species using height (m) classes.
| Scientific Name | Height class (m) | ||||||||
| 5-8.99 | 9-12.99 | 13-16.99 | 17-20.99 | 21-24.99 | 25-28.99 | ≥29 | Total | ||
| Acacia auricoliformis Willd | 5 |
|
|
|
|
|
| 5 | |
| Alstonia scholaris R. Br. | 1 |
|
|
|
|
|
| 1 | |
| Aquilaria agalocha Robx | 3 | 5 | 1 |
|
|
|
| 9 | |
| Artocarpus chaplasha Roxb |
| 9 | 19 | 1 |
|
|
| 29 | |
| Artocarpus heterophyllus Lamk |
| 4 |
|
|
|
|
| 4 | |
| Averrhoa carambola Linn | 1 |
|
|
|
|
|
| 1 | |
| Cassia siamea Lamk | 11 | 6 |
|
|
|
|
| 17 | |
| Casuarina lattorea Linn | 1 |
|
|
|
|
|
| 1 | |
| Cocos nucifera Linn |
| 1 |
|
|
|
|
| 1 | |
| Dipterocarpus turbinatus Gaertn |
|
| 5 | 29 | 37 | 41 | 35 | 147 | |
| Eucalyptus camaldulensis Dihn | 1 |
|
|
|
|
|
| 1 | |
| Ficus roxburghii | 1 | 1 |
|
|
|
|
| 2 | |
| Lagerstroemia speciosa |
| 2 |
|
|
|
|
| 2 | |
| Mangifera indica Linn | 14 | 10 | 1 |
|
|
|
| 25 | |
| Meliaceae sempervirens linn All | 1 | 1 |
|
|
|
|
| 2 | |
| Mesua ferrea | 1 |
|
|
|
|
|
| 1 | |
| Michelia champaca Linn | 2 |
|
|
|
|
|
| 2 | |
| Mimusops elengi Linn | 2 | 6 | 6 | 13 | 16 |
|
| 43 | |
| Phyllanthus emblica Linn | 1 |
|
|
|
|
|
| 1 | |
| Samania saman | 3 |
|
|
|
|
|
| 3 | |
| Shorea rabusta Gaertn | 26 | 70 | 98 | 2 |
|
|
| 196 | |
| Swietenia mahagoni (L.) Jacq | 2 |
|
|
|
|
|
| 2 | |
| Syzygium grande (Wt) Walop | 1 |
|
|
|
|
|
| 1 | |
| Tectona grandis | 3 | 1 |
|
|
|
|
| 4 | |
| Terminalia arjuna W&A | 2 |
|
|
|
|
|
| 2 | |
| Terminalia belerica |
| 1 |
|
|
|
|
| 1 | |
| Terminalia chebula Retz | 1 |
|
|
|
|
|
| 1 | |
| Total | 83 | 108 | 120 | 63 | 54 | 41 | 35 | 504 | |
Table 4.4 also shows that 83 trees possess in class 5- 8.99, 108 trees possess in class 9- 12.99, 120 trees possess in class 13- 16.99, 63 trees possess in class 17- 20.99, 54 trees possess in class 21- 24.99, 41 trees possess in class 25- 28.99 and 35 trees possess in class ≥29
Fig Distribution of number of individuals and species in different height classes.
Figure also shows that the height number of stem presents in classe 13-16.99. Species with highest of individuals (120) were present in height class 13-16.99m and the least number of individuals were present in the height class ≥29.
4.3 Quantitative structure of tree species of the study area
The quantitative structures of trees vegetation of the study area were based on the
1. Number of stems
2. Basal area
3 Density
4. Frequency
5. Abundance
6. Relative density
7. Relative frequency
8. Relative abundance
9. Relative dominance and
10. Importance Value Index.
The result was revealed that the 504 number of stems and 38.72m2 basal areas was found in sampling areas (3000m2). The highest number of stems was found in
1. Shorea rabusta Gaertn (196)
2 Dipterocarpus turbinatus Gaertn (147)
3 Michelia champaca Linn (43)
4 Artocarpus chaplasha Roxb (29)
5. Lagerstroemia speciosa (25)
Minimum basal area was found in Meliaceae sempervirens linn All (.0039m2) followed by Mimusops elengi Linn (.0043m2), Terminalia chebula Retz (.0054m2), Syzygium grande (Wt) Walop (.0054m2), Averrhoa carambola Linn (.007m2) and Casuarina lattorea Linn (.008m2). The five species with highest density (tree/100m2) were Shorea rabusta Gaertn (6.53)(Figure 4.4), Dipterocarpus turbinatus Gaertn (4.90), Michelia champaca Linn (1.43) Artocarpus chaplasha Roxb (.967) Lagerstroemia speciosa (.83). The highest frequency was found in Dipterocarpus turbinatus Gaertn (70) followed by Shorea rabusta(66.67), Michelia champaca Linn (33.33) Artocarpus chaplasha Roxb (26.67 Lagerstroemia speciosa (23.33). The five species with highest abundance were Shorea rabusta Gaertn (9.8), Dipterocarpus turbinatus(7) Michelia champaca 4.3) Artocarpus chaplasha (3.57)Lagerstroemia speciosa (23.33)
Table also shows that the five species with highest relative abundance were Shorea rabusta Gaertn (15.9), Dipterocarpus turbinatus Gaertn (11.35) Michelia champaca Linn (6.97) Artocarpus chaplasha Roxb (5.88) Lagerstroemia speciosa (5.79) Maximum relative frequencies was found in Dipterocarpus turbinatus Gaertn (20.19) followed by Shorea rabusta Gaertn (19.23), Michelia champaca Linn (9.61.) Artocarpus chaplasha Roxb (7.695) Lagerstroemia speciosa (6.73). The five species with highest relative dominance were Shorea rabusta Gaertn (37.25), Dipterocarpus turbinatus Gaertn (37.15) Michelia champaca Linn (10.87) Artocarpus chaplasha Roxb (9.51)Lagerstroemia speciosa (1.94)
Table4.5:Quantitative structures of trees vegetation of the Tilagarh Eco-park
| S Name | No of stem | stem/ha | B.A area | Density/ 100m² | R D% | Frequency | R.F% | Abundant | R.A% | R Dom % | IVM |
| Acacia auricoliformis | 5 | 17 | 0.080 | 0.1666 | 0.992 | 3.3333 | 0.961 | 5 | 8.112 | 0.208 | 2.162 |
| Alstonia scholaris | 1 | 3 | 0.015 | 0.0333 | 0.198 | 3.3333 | 0.961 | 1 | 1.622 | 0.040 | 1.20 |
| Aquilaria agalocha | 9 | 30 | 0.352 | 0.3 | 1.785 | 10 | 2.884 | 3 | 4.867 | 0.910 | 5.581 |
| Artocarpus chaplasha | 29 | 97 | 4.209 | 0.9667 | 5.753 | 26.667 | 7.692 | 3.625 | 5.881 | 10.87 | 24.31 |
| Artocarpus heterophyllus | 4 | 13 | 0.058 | 0.1333 | 0.793 | 13.333 | 3.846 | 1 | 1.622 | 0.150 | 4.790 |
| Averrhoa carambola | 1 | 3 | 0.007 | 0.0333 | 0.198 | 3.3333 | 0.961 | 1 | 1.622 | 0.019 | 1.179 |
| Cassia siamea La | 17 | 57 | 0.350 | 0.5666 | 3.373 | 20 | 5.769 | 2.833 | 4.597 | 0.904 | 10.04 |
| Casuarina lattorea | 1 | 3 | 0.008 | 0.0333 | 0.198 | 3.3333 | 0.961 | 1 | 1.622 | 0.021 | 1.181 |
| Cocos nucifera | 1 | 3 | 0.022 | 0.0333 | 0.198 | 3.3333 | 0.961 | 1 | 1.622 | 0.057 | 1.217 |
| Dipterocarpus turbinatus | 147 | 490 | 14.38 | 4.9 | 29.16 | 70 | 20.19 | 7 | 11.35 | 37.15 | 86.51 |
| Eucalyptus camaldulensis | 2 | 7 | 0.019 | 0.0667 | 0.396 | 6.6667 | 1.923 | 1 | 1.622 | 0.049 | 2.369 |
| Ficus roxburghii | 2 | 7 | 0.012 | 0.0667 | 0.396 | 3.3333 | 0.961 | 2 | 3.245 | 0.032 | 1.391 |
| Lagerstroemia speciosa | 25 | 83 | 0.752 | 0.8333 | 4.960 | 23.333 | 6.730 | 3.571 | 5.794 | 1.942 | 13.63 |
| Mangifera indica | 2 | 7 | 0.048 | 0.0666 | 0.396 | 6.667 | 1.92 | 1 | 1.622 | 0.125 | 2.445 |
| Meliaceae sempervirens | 1 | 3 | 0.003 | 0.0333 | 0.198 | 3.3333 | 0.961 | 1 | 1.622 | 0.010 | 1.170 |
| Mesua ferrea | 2 | 7 | 0.014 | 0.0666 | 0.396 | 6.6667 | 1.923 | 1 | 1.622 | 0.036 | 2.356 |
| Michelia champaca | 43 | 143 | 3.684 | 1.4333 | 8.531 | 33.333 | 9.615 | 4.3 | 6.977 | 9.515 | 27.66 |
| Mimusops elengi | 1 | 3 | 0.004 | 0.0333 | 0.198 | 3.3333 | 0.961 | 1 | 1.622 | 0.011 | 1.171 |
| Phyllanthus emblica | 1 | 3 | 0.011 | 0.0333 | 0.198 | 3.3333 | 0.961 | 1 | 1.622 | 0.029 | 1.189 |
| Samania saman | 3 | 10 | 0.075 | 0.1 | 0.595 | 6.6667 | 1.923 | 1.5 | 2.433 | 0.194 | 2.712 |
| Shorea rabusta | 196 | 653 | 14.42 | 6.5333 | 38.88 | 66.667 | 19.23 | 9.8 | 15.90 | 37.25 | 95.37 |
| Swietenia mahagoni | 2 | 7 | 0.027 | 0.0667 | 0.396 | 3.3333 | 0.961 | 2 | 3.24 | 0.07 | 1.42 |
| Syzygium grande | 1 | 3 | 0.00 | 0.033 | 0.19 | 3.333 | 0.96 | 1 | 1.62 | 0.01 | 1.17 |
| Tectona grandis | 4 | 13 | 0.08 | 0.133 | 0.79 | 6.666 | 1.92 | 2 | 3.24 | 0.22 | 2.93 |
| Terminalia arjuna | 2 | 7 | 0.02 | 0.066 | 0.39 | 6.666 | 1.92 | 1 | 1.62 | 0.06 | 2.38 |
| Terminalia belerica | 1 | 3 | 0.02 | 0.033 | 0.19 | 3.333 | 0.96 | 1 | 1.62 | 0.07 | 1.23 |
| Terminalia chebula | 1 | 3 | 0.00 | 0.033 | 0.19 | 3.333 | 0.96 | 1 | 1.62 | 0.01 | 1.17 |
| Total
| 504 | 1678 | 38.72 | 16.8 | 100 | 346.66 | 100 | 61.62 | 100 | 100 | 300 |
Figure Distribution of RD, RF, R. dominance and IVI of five dominant tree species.
Figure shows five dominant tree species in the forest with their individual and combined positions. The result depicted that Shorea rabusta Gaertn (95.37), was found in highest Importance Value Index followed by Dipterocarpus turbinatus Gaertn (86.51), Michelia champaca Linn (27.66.) Artocarpus chaplasha Roxb (24.31) Lagerstroemia speciosa (13.63).
4.4 Tree diversity
Table 4.6 shows the different diversity index for trees. Shanon-winner index is 1.8 for trees. The shanon-winner index for Sitapahar natural forest for tree species with dbh >10cm was 2.98 (Nath et. al., 2000). Present study considers only the tree species having ≥5cm diameter at dbh (1.3m) taking into account.
The diversity index for trees is 0.06. Diversity index for trees with dbh >10cm of Sitapahar natural forest of Chittagong (North) forest division was 3.395 (Nath, 1995), diversity index of Bamu reserve forest of Cox’sbazar forest division was 3.11 and diversity index of Bamer chara and daner chara under Banskhali upazila, Chittagong was 2.07 (Alamgir and Al-amin, 2005).
As species richness index is 9.62 and species evenness index is 1.25 for trees. The species richness index and species evenness index for trees with dbh >10cm of Sitapahar natural forest of Chittagong (north) forest division was 16.92 and 1.84 respectively (Nath et al., 2000). Another study was done by Alamgir and Al-amin (2005), the species richness index and species evenness index for trees of Bamer chara and daner chara under Banskhali upazila, Chittagong was 13.03 and 1.84. Higher the value of diversity, greater will be the stability of community (Rahman et al., 2000). Comparing to the above research findings, the species richness and species evenness index of Tilagarh Eco-park indicates that it can be converted into a diversity rich forest through protection (Figure 4.6).
Table 4.6 Different diversity index for trees
| Species | Categories | ||||
| Shanon-winner index | Species diversity index | Index of dominance | Species richness index | Species evenness index | |
| Tree | 1.8 | 0.053 | 0.10 | 9.62 | 1.25 |
