Flora

FLORA (terrestrial)

The forests of tripura are varied. On the basis of large-scale studies in other North-Eastern States, Deb(1981) considered the classification of forest types suggested by Champion and Seth (1968) as better suited for describing and correlating the forest types in India. Deb’s description of the flora of tripura has been followed here. 

Based on climate (also altitude and longitude), the forests of tripura are treated under tropical forest types. They are grouped and described as follows:

image

  1. Climate Types
    1. Evergreen forest
    2. Moist deciduous
      1. Sal forest
      2. Moist deciduous mixed forest
  2. Seral types
  3. Subsidiary edaphic types

General Floristics: I. Dipterocarpus turbinatus Gaertn., Artocarpus Roxb., A. heterophyllus Lamk., Cinnamomum glanduliferum (Wall.) Nees C. bejolghota Sw. Cryptocarya amygadalina Nees, Magnifera sylvatica Roxb., Aphanamixis polystachya (Wall.) Parker, Aglaia spectabilis Miq.,Schima Wallichii (DC) Korth., Actinodaphne angustifolia Nees, A. obvata B1.., Beildschmiedia assamica Meissn., Castanopsis indica ADC are common on the top canopy. In the more exposed drier regions and in areas where the forest has been subjected to shifting cultivation, deciduous or semi-deciduous plants like Bombax ceiba L., Terminalia bellirica(Castertn.) Roxb., T. myriocarpa Heu rck ex Muell., - Arg., Albizia procera (Roxb). Benth, Lagerstroemia speciosa (L)Pers., L. parviflora Roxb., IIex umbrella (wall) loses are common. 

II. Dysoxylum binectarderum Hook f.et. Bedd., Michelia champaca L., Mesua ferra I., Cinnamomum bejolghota Sw. Litsea glutinosa (Lour) C.B. Robinson, L. laeta (Wall. Ex. Nees) Hook. F.L.Panamouja (F.- Ham) Hook. F. persea villosa (Roxb), Kosterm., Phoebe attenuatta Nees, Pterospermum lanceaewfolium Roxb., Aquilaria malacensis Lamk, Toona cilita M. Roem., Hydnocarpus kurzil (King) Warb., Gynocardia odorata R. Br. Sterculia indica Merr., K.angustifolia (Roxb) Warb., K. malayana Warb., Ardisia colorata Roxb. A. paniculata Roxb. A neriiifolia Wall. Ex. ADC., Holigarna caustica Roxb. Ex. Gresh., Stereospewrmum personatum (Hassk) Chatterjee. Vitex penduncularis Wall. Ex. Schauer. Turpina pomifera DC., Alstonia scholaris (L) R. Br. Etc. along with smaller trees of the upper canopy are found in the second storey. 

II.a. Litsea cubeba (Lour) Pers., L. lancifolia Roxb. Ex.Nees., Neolitsea zeylancia (Nees) Merr., Phoebe lanceolata (Nees) Nees, Bambusa tulda Roxb., Dendrocalamus hamiltoniii Nees & Arn., 

Oxytenanthera albociliata Munro, Bambusa pallida Munr. Livistona chinensis R. Br. Syzygium cumini (l) Skeels. S. cerasoides (Roxb) Chatterjee et Kangi. F. Palaquium polyanthum Engl., Casearia kurzii C.B. Clerke etc. form this storey in places. 

III. Shrubby layer comprises Meliosma simplicifolia (Roxb.) Walp., Litsea meissneri Hook.F.L. salicifolia (Roxb. Ex. Wall). Hook.F. Maesa ramentocea (Roxb) A.D.C. Micromelum integerrimum ( F.-Ham. Ex DC) Wt. & Arn., Phlogacanthus thrsiflorus Nees. Strobilananthes capitatus T. Anders., S. scaber Nees Clausena heterophylla (roxb) Wt. & Arn., tree ferns and a very large number of other plants. 

IV. Curculigo latifolia Dryand, C. Orchides Gaeertn., Phrynium capitatum Wild Begonia roxburghi A.D.C. B. Barbata Wall Ex. A.D.C. Alpinia allughas Rose., A bracteata Roxb., Wt. E. platyphyllum Wedd., E. rupstre Wedd. Hedyotis coronata Wall. Ex. Hook.f. Amaryllidaceae, Scitamineae, Commelinaceae, Rubiaceae., Araceae and many othersa form the ground layer. Aeiginetia indica L. a. saprophyte is very common. 

V. Dense masses of evergreen climbers like Entada phaseolodes (L). Merr., Bauhinia anguina Roxb. (fig.5) Acacia pruinescens Kurz, Beaumontia grandiflora (Roxb). Wall., Tetracera scandens (L) Merr., Rhaphidophra eximia Schott., R. decursiva (Roxb) Schott. Tetrastigma bracteolatum (Wall) Planch., Vitis tuberculata (BI) Laws, Calamus leptospadix Griff., Pothos scandens L.,P. cathcartii Schott., etc. are very common. 

Orchids are common in the evergreen forest, Phajus tankervilliae (Alit.) BI., Apostasia wallichii R.Br. Hetaeria rubens Benth., tropidia angulosa BI. And Zeuxine strateumatica (L) Schltr. are scattered in the ground layer. Epiphytic orchids are more numerous than the terrestrial ones. 

Frequency, dominance and association of species very often vary from one forest to another. In Damcherra Diperocarpus turbinatus Gaertn. F., Mesua ferra L., ilex godajum Colebr., Dysoxylem binectariferum Hook. f.et Bedd, Artocarpus chaplasha Roxb. Form consociations., whereas in the Jampui and Sakhan Ranges Schima wallichii Choisy, Gynocardia odorata R. Br., Hydnocarpus kurziii (King) Warb., Beilschmedia media assamica Meissn. Cryptocarya amygdalina Nees and others form associations.

1. Moist Deciduous Forest : The moist deciduous forests are characterized by the presence or absense of Sal and accordingly they may be acalled (a) Sal forest or (b) Moist deciduous mixed forest as the case may be .

a. Sal Forest : This occurs in southern region of the wstern low hill extending to the border of Bangladesh. It is found locally in Belonia, Udaipur, Sonamura and Sadar Sub-Divisions. Local variations occur in flouristic composition and aboundance of different species and in the storeyed arrangement in different areas. A general outline of the flouristic composition is given below. Shorea robusta Gaertn.f. is the ecologically characterestic and economically inportant species that dominates over 60 per caent of the top canopy. Dipterocarpus turbinatus Gaertn., Lagerstroemia parviflora Roxb., Gmelina arborea Roxb., Careya arborea Roxb. also occur.

Schima Wallichii (DC) Korth, Terminalia belliricia (Gaertn). Roxb., T. Chebula Retx, Stereospermum personatum (Hassak) Chatterjee, Vitex Peduncularis Wall. Ex. Schauer, Pterospermum semi sagittatum F. Ham, Ex. Roxb., P acerifolium Wild, Dilleia pentagyan Roxb., Syzygium cerasoides (Roxb) hatterjee et Kanji.f.Lagerstroemia parviflora Roxb., Garuga pinnata Roxb., Albizia chiensis (Osbeck) merr. A procera(Roxb.) Benth Lannea coromamdelica (Houtt) merr. Chukrasis tabularis. A Juss, Tonna ciliate M. Roem Sapium baccatum Roxb., Oroxylum(L) Vent., Protium serratum (Wall. Ex.Coleb) Engl. Etc. from the next canopy.

Phyllanthus emblica L., Mallotus phillippensis (lamk) Muel.,-Arg., Aporusa blonga (Wall) mule Arg.,Maesa rameentacea (Roxb) A.d.C., Cordia fragrantissina Kuez, Semecarpus anacardium L.f. Streblus as per Lour., Bridellia retusa Spreng. Antidesma bunius (L) Spreng., Macaranga denticulate (Bl.), Muel.Arg Bauhinia purpurpa L;B.Variegata L, Dsosylui binectariferun Hook. F. et. Bedd, Callicarpa arborea Roxb. Litsea monopetala (Roxb) Pers., Melliosma simpliciflora (Roxb) Walp., Microcos paniculata L. Syzygium Fruitcosum DC., Premna coriacea C,B Clarke, Zanthoxylum limonella (Dennst) Alst., Dalbergia stipulacea Roxb. D lanceobaria L. Millettia auriculata Baker ex Brandis. Dendrocalamus hamiltonii Nees & Arn. Bambusa pallida Munro, Oxytenanthera albociliata Murno etc., also occur in the second storey.

Butea parviflora Roxb. Dlahousiea bracteata (Roxb) R. grah byttneria pilosa Roxb. Stephania glandulifera Miers Combbretuym roxburghi spreng., Pueraria phaseoloides (Roxb) Benth, Mucuna nigricans (Lour) Steud., M.Pruita Hook., Smilax zeylanica L. Dioescorea bulbifera L.D. glabra Roxb., D. hamiltonii Hook.f. Cayratia japonica (Thumb) Gangnep., C. repanda Vahl., Vitis tuberculata (BI) Laws are the common climbers.

Meleastoma malbathricum L, Osbeckia chinesis L., O.nepalensis Hook., Clerodendrum viscosum Vent, Desnodium heterocarpon (L.) Dc. ,D. Caudatum (Thumb) DC., D, gangeticum (L) DC., Maughania stronbiliferum (L.) St. Hill ex Jackes, M. stricta(Roxb), O. Kuntze etc., from the shrubby layer.

Ground cover is formed of a large number of grasses and hedges. In rainy seasons herbs belonging to the families Commmelinaceae,Zingiberaaceae,Dioscoreaceae and a host of others grow.

Due to local edaphic factoes and biotic influences on certain localities particularly in Sonamura, tha Sal forest has been reduced to a secondary savannah, where much of the area has been brought under paddy cultivation by feeling the trees. Trees are stunted and crooked in form. Most of the plants appear to have come up from stumps. The forests are separated into northern and southern parts by about 6.4 km. of paddy land. The quality of wood appears to be slightli inferior in the northern part, probably due to difference in soil, Regeneration is good, but the seeding are mostly burnt away by annual fire. 

b.Moist Deciduous Mixed Forest: Moist deciduous mixed forest covers a large area of the forest in Amarpur, Sonamura, Udaipur and Sadar-Divisions and occurs in patches in Dharmanagar, Kailasahar and Kamalpur Sub-Divisions. This differs mailnly from the preceding one in the absence of Sal or in its scarcity. Dominants are mailnly deciduous, but sub-dominants and lower storeys are largely evergreen. Top canopy is not dense and even. It is about 18-25m. high. Differentiation in canopy layer, is not conspicuous.

I. Schima wallichi (DC) Korth, Dilenia pentogyna Roxb, Terminalia bellirica (Gaertn) Roxb., Garuga pinnata Roxb., Lannea coromondelica(Houtt.) Merr. Buccania lanzan Spreng., Stereospermum personatum (Hassk.) Chatterjee. Pterospermumacerifolium Wild. P . semisagittatum F. Ham. Ex. Roxb., Laggerstroemia parviflora Roxb., Churaisa tabularis A. Juss Bombex ceiba L. Vitexpeduncularis Wall. Ex.Sachauer Hymenodictyon excelsum(Roxb.) Wall., Mitrangya rotandifolia (Roxb) O. Kuntze. Nauclea Sessilifolia Roxb. Dubanga grandiflora (Roxb) Walp. Gmelina arborea Roxb. Albizia (Roxb) Bnth, Elaecarpus prunifolia Wass ex. Mart., Sterculia villosa Roxb., Gardenia resinifera Roth, Erythrina arborescene Roxb, Sapium baccatum Roxb., Syzygium syzygiodes (Miq.) Merr. et. Perry. S. Cerasoides (Roxb) chatterjee et Kanj. F. Eugenia praecox Roxb. Constitute the top canopy.

II. The second story is made up of the smallest trees of the first storey together with the following: Holarhen antidysenterica G.Don ex. A.DC Micros paniculata L., phyllanthus emblica L., Litsea cubea (Lour) Pers L, Iancifolia Roxb., Aesculus assamica Griff., xeromphis spinsa (Thumb) Keay, melocanna bambusoides trin, Stre blus asper Lour macaranga denticulate (BI) Muell-Arg., Mallotus aiba Muell-Arg., M. Phillipensis (Lamk) muel-Arg. Ardisia colorata Roxb., A. paniculata Roxb., Flacourtia indica (Burm.f.) Merr., Clerodendrum viscosum vent., maesa chista F. Ham- M.indica (Roxb.) A.Dc., Pogostemon parviflorus Benth.

At the exposed regions of the forest Phyllanthus emblica., Croton ablongifolius Roxb., Pandanus foetidus Roxb., Pandanus foetidus Roxb., P.furcutus Roxb., Aesculus assamica Griff., Mallotus philippensis (Lamk) Muell.- Arg., Clerodendrum viscosum Vent., Holarrhena antidysenterica G.Don ex A.Dc, Microcos paniculata L. Macarange denticulate (BI) Muell-Arg and others form associates. 

Butea parviflora Roxb., Byttneria pilosa Roxb., Combreutum roxburghii Spreng., Pueraria phaseoloides (Roxb) Benth., Mucuna DC., M.nigricans(Lour) Steud., Elaeagnus conferta Roxb. Dioscorea bulbifera L.D. glabra Roxb., smilax zeylanica L. Argyreia cupitata (Vahi) Choisy, Coccinia cordifolia (L) Coga., Melothria heterophylla cogn., Thladiantha calcarata C.B. Clarke, Cissampelos pareira L. Stephania japonica (Thunb). Miers var. discolor(Miq.) Forman, Thunbergia grandiflora Roxb., Pothos scandens D.Don, Rhaphidophora eximia Schott R. lancifolia Schott., are very common.

Geound cover is formed of Desmodium triquetrum (L) DC., D. Caudatum (Thumb) DC. D. heterphyllum (Willd). Dc. Maughania strobilifera (L) St. Hill. Ex. Jacjes, M.stricta (Roxb) Kuntze, Costus speciosus (Koenig) Smith, Curcuma zedoaria Rose., and other Zinmgiberaceous plants and many others.

Mikania cordata (Burm. F.) Robins, an exotic climber is common in this forest. Eupatorium odoratum L. and E. cannabinum L, are fairly common. Towards the middle of the hot season, the deciduous trees shed leaves but they are not completely leafless and they are again in leaf before the monsoon. Mostly the trees and other woody species flower in the hot season. Rhizomatous and bulbous families like Liliaceae, Amaryllidaceae, Zingiberaceae send up their scapes and produce beautiful flowers in the rainy season. These form a characteristic undergrowth in the monsoon period.

 

Swamp Vegetation:
Swamp locally called 'Lunga' occupy a very large area all over the State. Formation of these Lungas has (Deb, 1975) been discussed in connection with geology and soils.

It comprises mostly herbaceous species, some woody shrubs and a few scattered trees, Barringtonia acutangula (L) Gaertn. lagerstroemia pariviflora Roxb., Mallotus philipinesis (Lamk.) Muel- Arg., are the common trees. Phragmities karka (Retz) Trin., Alpinia aalughas Rosc., Saccharum spontaneum L., Erianthus arundinaceus (Retz.) Jeswiet Eleocharis plantaginea R. Br. E. ramulosa C.B. Clarke, Scripus supinus L. Cyperus compactus Retz., C. difformis L., Fimbristylis dichotoma (I.) Vahl., F. glomer ata kunth etc. are the common herbs. 

In marshy or low lying places with shallow water table are very commonly found, sometimes in vast areas, Alppinia allughas Rose., A. bracteata Roxb., A galangal (L) Wild., A. malcaensis Rose, Imperata Cylindrica (L) P. Beauv., phragmites karka (retz) Trin. Ex. Steud., Erianthus arundinaceus (Retz.) Jesweit, E.Procerus (Roxb) Raizada and Saccharum spontaneum L. They form socies and grow in associes in various proportionsa probably depending on the condition of the soil and depth of water. Accordingly to the percentage of area covered by the individual species, they appear to form phragmites- Alpinia- Phragmitiers- Saccharum associates.

All the edges, rooted in the mud or floating or submerged in water are found, Melastoma malabathricum L. Osbeckia chinensis L. Ludwigia actovalvis sussp. Sessilliflora (Micheli) Ravan, L. prostrate Roxb., L. Clavellina Gomez et molionet, Euryale ferox Salisb., Nymphodes cristata (Roxb) O. KunzeTrapa natans L. Var. bispinosa (Roxb) Makin., Ottelia alismoides Lemma purpusilla Torr., Wolffia arrhiza (L) Wimm. Spirodela Polyrhyiza (I) Schleid, Vallisneria sprialis L., Hydrilla verticillata (I.f) Royle, Sagittaria sagtittifiolia L. Utricularia flexuosa Vahl, Eriocaulon cineremum R. Br. Polycarpon indicum (Retz) merr., Rotala indica (Wild) Koelme, Sphenoclea zeylanica Gaertn., Smithia sen sitiva Ait., Hydrolea zeylanica (L) Vahl. Limnophila sessilis (Benth) Fischer, Leersia hexandra Sw. Floscopa Lour Monochoria hastate (I) Solms and Polygonum hydropiper L.

Bamboo Forest:

Bamboo brakes widely in character and aspect cover very large areas in Tripura as in Burma and Chittagong. Continuous bamboo forests are interrupted with scattered evergreen treesor deciduous secondary stands. Sheltered hollows and other favourable sites are dominated by bamboo. The vast preponderance of bamboo forest may be the result of activity of man in his practice of shifting favourable for bamboo growth. It is also possible that bamboo holds the ground as a primary edaphic sub-climax.

About 1927 sq.km. of area is covered with 'Muli' Melocanna bambusoides Trin. In the valleys of Deo-Manu major rivers. Of the large numbers of bamboos occurring there only 19 species have so far been identified. Some of them are name below with the local names in the parenthesis: (I) Bambusa balcooa Roxb('Barak'), (2) B. nutans Wall. Ex munro('Kali') (3) B.pallida Menro('Makal') (4) B.polymorpha Munro ('Barua') (5) B. teres Ham. Ex Wall ('Parua') (6)B. tulda Roxb. ('Mirtinga') (7) Dendro calamus hamiltonii Nees & Arn. Ex Munro ('Pecha') (8) D.longispathus kurz ('Rupal') (9) Melocanna bambusoides Trim ('Muli') (10) Oxytenanthera nigrociliata Munro ('Kayal') and (11) Neohouzeaua dullloa, A. Camus('Dalu')

 

       

  • -- Growing stock of Bamboos in the state

       

  • -- The Yield of Bamboos in the state

 

Table: 4.1. Growing stock of bamboo in the state - (all strata included)

 

 

Clump Forming Bamboo

Non-Clump Forming Bamboo

 

Nos

Weight

Nos

Weight

Average per hactare

58.954

94.931 kg

1058.36

1255.08 kg

Total for the State

37,093 million

59415.985 M.T

665.920 million

789695.77 M.T

 

  • Source FSI report, 1993

 

Table: 4.2. The Yield Of Bamboos in the State (taking a rotation of 5 years)

 

Category

Yield in Weight(metric ton)

Yield in Number(million)

Clump forming

14853

9.27

Non-clump forming

197424

166.05

Total

212277

175.32

 

  • Source FSI report, 1993

Cane Brakes: Impenetrable thorny thickets are seen in the evergreen semi evergreen and most deciduous forests. They occur in wet hollows extending outwards to various distances andappear to be conspicuous with heavier and well distributed rainfall where the soil is finely clayed and brakes have been destroyed. Calamus floribundas grif, C. guruba F. Ham, and C. lepetopadix Griff , C. floribundus , C. tenuis , C. leptospadix, C.erectus are the common canes. No rsttimate for existing growing stock of aforesaid species of cane available. 
 

Garjan Forest : The area occupied by the Garjan Forest at present is small but there are indications that Garjan used to occur in a far larger area all over the state in small or larger groups .Stumps are found here and there near Khowai , Champaknagar Betaga –Ludhua , Muhuri , , Trishna ,Tulatalikona,Chailengta, Deo ,Juri Ujan Machmara ,Damchara , Unakoti, Dharmanagar, Sonamura and Jalaya.
It occurs in groups and strip in scattered block s on ferruginuous red soiled elevated tills . It also occurs in sal forest. It froms a close canopy while growing in groups. All The areas appear to have been gratly influenced by man.
Similar Garjan forest in Chittagong hills is considered to have originated through human influences on the climax evergreen or semi –evergreen type. The Persistence of old Garjan and their continued regeneration on inventively affected village lands is most striking and it is evident that the are hardier that in their associates.

Savannah: This is caused by fresh deposit of silts or destruction of the forest. In high land Syzygium cerasoides (Roxb) Chatterjee, Ziziphus Mauritiana Lamk. Z. Rugosus Lamk . Garuga pinnata Roxb , Lannea coromandelica (Hutt) Merr , Glochidion Multiculare Vogit ex Muell Arg ,vitex negundo L. Meyna spinosa Roxb Ex link, Flacourita indica (Buarm.F) Merr Leea crispa L. Desmodium triquetrum (L) Dc.Maughania strobilifera(I)St. Hill Ex. Jacks,clerodendrum viscosum vent,pletranthus ternfolius D.Don,chrysopogoa aciculatus(Retz.)Trin., Curcuma zedoaria rose., are common . In low land erianthus procaerus (Roxb) Raizada, Malaccesias Rosc, Hedychium ellipticum F. –Ham grow in communities. Triumfetta rhomboidea jacq,urena lobata L, Euphorbai hirita L. Phyyllanthus simplex Retz., P.niruri L.P, emblica L.,Vernonia cinerea(I) hedyotis scandens Roxb., crotalaria mucronata desv, c. ferruginea Grah.,
c. prostrate Rottlr ex. Wild., Ageratum leucocephala (Lamk) de witGlinus lotides L. calotropis gigantean (L) Dryand, solanum achranthes aspera L., polygonum glabrum willd p.plebejum L. Mimosa pudica L. scopartia dulcis L., cyperus cyperoides (L.) O. kuntze, Desmodium triflorum(L.) DC., D. Heterrophyllum(Wild) DC, Rungia Parviflora Nees. In the monsoon climbers of Dioscoreaceae, smilacaceae,Menispermaceae,convovlulaceae ans vitaceae grow rapidly around trees and shrubs of sometimes they trail on the ground or over the herbaceous undergrowth.

Grass Land Vegetation: A Large area of the state is covered with vast expanses of grasses. This grass land community is a biotic sub-climax. The vegetarian is held here in a condition of equilibrium by biotic influence.
The grazing ground is dominated by the following species: Imperata cylindrical(L.) P. Beauv., Paspalium orbiculare Forst. Cynodon dactylon (L.,) pers., chrysopogon aciculotus (Retz) Trin., Bothriochola intermedia (R. Br.) A. camus, centotheca lappacea (L.)Desv., oplismenus compositus (L.) p.beaiv., sacciolepis interupta (willd.) stapf., cyperus sp. And fimbristylis sp. of other herbs occurring in the grass land. The following are common: Desmodium heterophyllum (willd.) DC., centella asiatica (L.) urban, leucas aspera spreang. Rungia parviflora Nees, Euphorbia thymifolia L., oxalis corniculata L., sida acuta Burm. F., urema lobata L. Mimosa Pudica L., solanum sp. Polygonum sp., etc. General statistics: Deb(1981) gives an account of 1573 taxa comprising 1545 species and 28 extratypical varieties in 862 genera and 192 families of vascular plants, representing about 12.86% of the Flora of India.
 

  • • Groups of Vascular plants and species

 

  • • Composition of Monocot and Dicol species

 

  • • Composition of plants species in Tripura and adjoining areas

 

  • • Families of plants having equal or more than 20 species

 

  • • Families having 10 or more genera

 

  • • Growing stock of Tripura

 

  • • MAI/Mean Annual Increment of commercially important trees.

 

 

Table:8.1 Groups of vascular plants and species

Name of the group

No. of families

No. of genera

No. of species

Pteridophyta

18

38

70+ 1 var

Gymnosperms

6

8

13

Dicotyledons

139

637

1159+23"

Monocotyledons

29

179

303+4"

The proportion of the Monocot and Dicot species in the world is 1:4.35, in India 1:2.3 while in Tripura it is 1:3.82. These ratios are compared for several nearby areas.
 

Table:8.2 Composition of monocot and dicot species

Propotion of Texa

India

Tripura

Mizoram

Manipur

Akha Hills

Proportion of Monocot and Dicot species

1:2.3

1:3.82

1:2.91

1:3.64

1:4.30

Proportion of Monocot and Dicot genera

 

1:3.56

1:3.17

1:3.40

1:4.84

Proportion of genera and species in Dicot

 

1:1.81

1:1.95

1:2.11

1:1.88

Proportion of genera and species in Monocot

 

1:1.69

1:2.13

1:1.99

1:2.12

Proportion of genera and species in Angiosperms

1:7

1:1.79

1:2.00

1:2.08

1:1.93

The numbers of genera and species in Tripura are tabulated and compared below with those of similar small areas of the region.
 

Table:8.3 Composition of plants species in tripura and adjoining areas

number of genera

number of species

Name of the group

Tripura

Manipur

Mizoram

Akha Hills

Tripura

Manipur

Mizoram

Aka-Hills

Dicotyledons

637

730

457

664

1159

1542

892

1252

Monocotyledons

179

218

144

137

303

435

307

292

Angiosperms

816

948

601

801

1462

1977

1199

1544

Gymnosperms

8

12

6

6

13

15

6

9

Pteridophyta

38

60

47

31

70

200

134

58

Total number

864

1020

561

838

1545

2192

1360

1611

Table:8.4 Families of plants having equal or more than 20 species

Sl. No.

Name of the family

No. of Genera

No. of Species

1.

Papilionaceaae

44

96+3 var

2.

Gramineae

49

79+1 var

3.

Rubiaceae

37

76

4.

Euphorbiaceae

31

67

5.

Compositae

39

54

6.

Labiatae

23

34

7.

Cyperaceae

10

33

8.

Orchidaceae

23

33

9.

verbenaceae

13

30+1 var

10.

Moraceae

5

29+1 var

11.

Acanthaceae

19

28 var

12.

Scrophulariacea

11

28 var

13.

Scrophulariacea

11

28 var

14.

Cucurbitaceae

16

26 var

15.

Malvaceae

10

25+1 var

16.

Araceae

15

25+1 var

17.

Mimosaceae

12

24+1 var

18.

Zingiberaceae

9

24

19.

Caesalpiniaceae

8

24

20.

Apocynaceae

20

24

21.

Convolvulaceae

9

22

22.

Lauraceae

8

21+1 var

23.

Urticaceae

10

20

It is evident from the foregoing table that Flora of Tripura has a larger number of genera and species than those of Mizoram whereas Aka Hills has a slightly larger number. Manipur being about double in area and havingmuch varied climatic conditions, is obviously having a much larger number of genera and species. There are 23 families which contain 20 or more species in each, 5 representing monocot and 54.82% of species and remaining species are shared by 171 families. families containing 10 or more genra each are tabulated in order of abundance in genera.
 

Table: 8.5 families having 10 or more genera

Sl. No.

Name of the family

No. of species

No. of Genera

1.

Gramineae

79+1 var

49

2.

Papilionaceae

96+3 var

44

3.

Compositae

54

39

4.

Rubiaceae

76

37

5.

Euphorbiaceae

67

31

6.

Orchidaceae

33

23

7.

Labiatae

34

23

8.

Apocynaceae

22+1

20

9.

Acanthaceae

28

19

10.

Cucurbitaceae

26

16

11.

Araceae

25+1 var

15

12.

Verbenaceae

30+1 var

13

13.

Arceaceae

19

12

14.

Mimosaceae

24+1 var

12

15.

Commelinaceae

14

11

16.

Scrophulariaceae

28

11

17.

Sterculiaceae

16

11

18.

Bignoniaceae

11

11

19.

Solanaceae

26+1 var

11

20.

Cyperaceae

33

10

21.

Meliaceae

13

10

22.

Malvaceae

25+1 var

10

23.

Urticaceae

20

10

The table above shows that there are 23 families containing 10 or more genera each. 6 of these are Monocot while others are Dicot. The hihest number is represented by Gramineae with 49 genera, which holds the second position in aboundance of species. On the other hand papilionaceae heading the list in number of species holds the second position in number of genera. 5 families nameky, Arecaceae,Commelinaceae, Meliaceae, Sterculiaceae and Bignoniaceae having less than 20 psecies are represented by more than 10 genera each.
Inventory survey carried out by the Forest Survey of India in the year 1991 (Report on Forest Resources of Tripura) gives average number of stems and volume per hectare (in all atrata i.e miscellaneous, miscellaneous with bamboo, plantation, and shifting cultivation). The situation has slightly changed now due to increase in plantation area but volume per ha in different strata remains more or less the same. The growing stock is has has been given in table 8.6
 

table: 8.6. Growing stock of Tripura

Stratum

Area in km sq.

Forest area(% of volume Geo.area)

(m3)/ha(weighted average)

Total volume (million m^3)

1.Hardwood (misc) forests

1829

17.43

26.178

4.788

2.Hardwood (misc) mixed with bamboo

484

4.61

29.839

1.444

3.Bamboo forests

938

8.94

9.0733

0.851

4.Plantations

2221

21.17

20.69

4.275

5.Shifting cultivation

840

7.81

5.339

0.521

Grand Total

6292

59.98

 

11.879

Eesearch statistics corroborate the fact and following table shows that MAI of commerciall important trees in plantations in quite high.

Species

Age in years

volume(m3/ha)

MAI(m3/h)

1.Treak (Tectona grandis) exotic

20

248

12.40

2.Sal(Shorea robusta)

20

181

9.05

3.Gamar(Gmelina arborea)

20

335

16.75

4.Chamal(Artocarpus chaplasa)

20

235

11.75

On the basis of Inventories of FSI in 1974 and again in 1989 and other related information, the Mean Annual Increment (MAI) of natural forestshas been calculated as 3.61m3/ha/year. The allowable cut of wood/annum from forests has been assesed as 1.526 million m3(0.041 million m3 timber plus 1.485 million m3 fuelwood).
Thus there is a large gap between potential and actual productivity, and generally poor actual productivity in natural forests is due to anthropogenic stress and this ia a matter of concern because,rising demand and poor prductivity lead to the vicious cycle of low productivity to resource degradation.

Growth potential of plantations

Blessed with high rainfall, humidity and nutrient rich soils, the forests of the State are in very high productivity zones. Execellent silvicultural conditions prevail for forest production. According to patterson's CVP (climate, vegetation and precipitation) index (1000-5000) the potential productivity is estimated to be 9-12 m3/ha/year.

Endemism
It is estimated that about 86% of species occuring in Tripura are widely distributed in India and adjoining countries. The remaining 145 of species are comparatively restricted in distribution. Phytogeographical trend of these species is indicated below.

Some of these are collected for the first time outside the type locality.

(A) New records for India

(1). Begonia surculigera kurz (Begoniaceae) ; Deb in bull.Occurance : Unakoti.
Distribution : Akyab in Burma

(2). Colona flagrocaropa (C.B Clarke ex Brandis). Craib Occurance : Jampui Ranges
Distribution : Chittagong (Bangladesh)

(3). Debregeasia dentata Hook. f. (Urticaceae) occurance : Jampui Ranges
Distribution : Chittagong (Bangladesh)

(4). Holigarna caustica Roxb. ex Gresh (Anacardiaceae) occurance : Ompi, Teliamura, Shilachari, Jampui Ranges 
Distribution : Chittagong (Bangladesh) and Burma

(5). Ophiorrhiza villosa Roxb. (Rubiaceae). occurance : Sepahijala and kumarghat 
Distribution : Chittagong Hills (Bangladesh)

(6). Torenia mucronulata Benth. (Scrophulariaceae) occurance : Ghorakappa 
Distribution : Burma

(7). Wallichia caryotodies Roxb. (Arecaceae) occurance : Barmura ana Atharamura Ranges 
Distribution : Chittagong (Bangladesh) and Burma

The flora of Tripura includes a large number of exotic species which have been introduced in Tripura over a long period. Many of them have established so well that they can be considered as indigenous.