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This article throws light upon the six main types of formations found in the Indian Desert. The types are: 1. Mixed Xeromorphic Thorn Forest 2. Mixed Xeromorphic Woodlands 3. Psammophytic Scrub Desert 4. Lithophytic Scrub Desert 5. Mixed Xeromorphic Riverine Thorn Forest 6. Halophytic Scrub Desert.
Type # 1. Mixed Xeromorphic Thorn Forest:
The plants growing on Aravallis and rugged hills are grouped under the ‘mixed xeromorphic thorn forest’ because the communities are largely dominated by thorny and spiny species, and some evergreen non-thorny species as well.
The principal plant communities are:
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(1) Anogeissus pendula – Acacia Senegal,
(2) Acacia Senegal – A. pendula,
(3) Anogeissus pendula,
(4) Acacia Senegal.
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A. pendula – A. Senegal is supposed to be the climax community of the hills. Besides these the degraded communities which are met on several types of rocks are (1) FMphorbia caducifolia – Acacia Senegal, (2) E. caducifolia – Grewia tenax, (3) Euphorbia caducifolia (4) E. caducifolia – Capparis decidua, (5) Capparis decidua, (6) Cassia auriculata and (7) Maytenus emarginatus – E. caducifolia.
The associated trees and shrubs are Anogeissus rotundilfolia, Cordia gharaf, Moringa coccanensis, A. Senegal, Anogeissus pendula, Salvadora oleoides, Wrightia tinctoria, Azadirachta indica, Maytenus emarginatus, Solanum albucaule, Grewia tenax, Capparis decidua, Euphorbia caducifolia and Cassia auriculata.
The ground flora includes a few species of grasses and forbs, such as Cymbopogon jwarancusa, Aristida funiculata, Eleusine compressa, A. hirtigluma, Tragus biflorus, Oropetium thotnaeum, Indigofera cordifolia, I. linnei, Lepidagathis trinervis, Blepharis sindica, Tephorsia purpurea, Tridcix procumbens, Cleorne viscosa, Tribulus terrestris, Peristrophe bicalyculata, Rarleria acanthoides.
Type # 2. Mixed Xeromorphic Woodlands:
It is largely constituted by spiny species mixed with non-spiny and evergreen species or with those species having stems and branches or both green.
The main plant communities are:
(1) Salvadora oleoides – Prosopis cineraria,
(2) Prosopis cineraria- Zizyphus nummulria – Capparis decidua,
(3) Salvadora oleoides – Capparis decidua – P. cineraria,
(4) Salvadora oleoides,
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(5) Capparis decidua – S. oleoides, P. cineraria,
(6) S. oleoides – C. decidua,
(7) P. cineraria – S. oleoides-Z. nummularia,
(8)S. oleoides-Cassiaauriculata,
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(9) P. cineraria C. decidua,
(10) P. cineraria – Z. nummularia,
(11) C. decidua,
(12) Zizyphys nummularia,
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(13) S. oleoides-P. cineraria-Z. nummularia,
(14) P. cineraria – Acacia nilotica.
The common shrub associates include Calotropis procera, Balanites aegyptiaca and Acacia jacquemontii. The forbs and grasses are A erva persica, Tephrosia purpurea, Crotalaria burhia, Convolvulus microphyllus, Heliotropium subulatum, Pulicaria wightiana, Celosia argentea ; Eleusine compressa, Dactyloctenium sindicum, Desmostachya bipinnata, Cenchrus ciliaris, C. sentigerus.
Type # 3. Psammophytic Scrub Desert:
This is mostly localised on Aeolian deposits i.e., on stabilized sand-dunes, undulating hummocky older alluvial plains, interdunal hummocky plains and free and obstacle dunes. The vegetation is well colonized by typical psammophillous species, namely Aerva persica, A. pseudotomentosa, Crotalaria burhia, Panicum turgidum, Cyperus leavigatus, Calligonum polygonoides, Clerodendron phlomoides, Cenchrus biflorus, Aristida funiculata.
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The moderate sand dunes are found with following communities:
(1) Calligonum polygonoides – Clerodendron phlomoides,
(2) C. polygonoides-Panicum turgidum,
(3) Acacia jacquemontii-Acacia Senegal,
(4) Maytenus emarginatus – Calotropis procera,
(5) M. emarginatus – A. Senegal,
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(6) A.senegal – Calligonum polygonoides,
(7) Crotalaria burhia- Aerva pseudotomentosa,
(8) C. burhia – Sericostemma pauciflorum – Lep- tadenia pyrotechnica.
The stabilized dunes bear small trees and a few shrub species, such as Prosopis cineraria, Salvadora oleoides, Balanites aegyptiaca. Tecomella undulata, Maytenus emarginatus, LyciumbarbarumandAcacia jacquemontii.
The interdunal spaces are occupied by Aerva pseudotomentosa, In- digofera argentea, Crotalaria burhia, Dipterygium sp. Panicum turgidum, Cenchrus biflorus, Aristida funiculata, Eragrostis sp., Tephrosia falciformis, Rhynchosia minima var. memnonia and stray shrubs of Calligonum polygonoides, Calotropis procera, Haloxylon salicornicum and Acacia jacquemontii. Sand dunes with their active crest and leeward end have the following communities, (a) Calligonum polygonoides – Panicum turgidum, (b) Acacia jacquemontii – Calligonum polygonoides, (c) Calligonum polygonoides – Halaxylon salicornicum – P. turgidum.
Type # 4. Lithophytic Scrub Desert:
The scrub desert vegetation is found on eroded rocky surfaces, pediment (boulders and rock fragments deposited at foothills) plains, limestone, slate, quartzite, granite etc.
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The common plant communities are:
(1) Capparis decidua
(2) Zizyphus nummularia – Capparis decidua
The associated plants in these communities are:
Shrubs: Leptadenia pyrotechnica, Calotropis procera. Zizyphus nummularia.
Undershrub: Aerva persica, Tephrosia purpurea, Sericostemma pauciflorum, Crotalaria burhia, Tribulus terrestris, Orygia decumbens.
Forbs: Cleomepapillosa, C. brachycarpa, Boerhaviadijfusa, B. elegans, Indigofera cordifolia, Mollugo cerviana, Salvia aegyptiaca.
Grasses: Aristida hirtigluma, Eragrostis sp., Eleusine compressa, Dac- tyloctenium sindicum, Oropetium thomaeum.
Type # 5. Mixed Xeromorphic Riverine Thorn Forest:
The beds of rivers-the Jawai, the Luni, the Sukri, and the Mitri and their tributaries form a narrow belt of younger alluvium. The lands are almost flat. Numerous wells are dug. Around the wells a few trees e.g., Azadirachta indica, Tamarindus indica, Albizzia lebbek, AilanthuS ex- celsa, Ficus religiosa, F. bengalensis, Moringa oleifera and Zizyphus mauritiana are maintained by farmers.
The terraces of the river banks are occupied by:
(i) Acacia jacquemontii- Cassia auriculata,
(ii) A. jacquemontii – Aerva pseudotomentosa, both on hummocky terraces,
(iii) Salvadora persica – Tamarix articulata,
(iv) Sal- vadora oleoides – C. decidua. Under these plant communities the grasses and forbs are Cenchrus ciliaris, C. setigerus, Aristida adscensionis, Digitaria adscendens, Dactylocteniumaegyptium, Chlorisvirgata, Cynodon, Tephrosia purpurea, Solanum surattense, Vernonia cinerascens, Heliotropium sub- ulatum, Crotalaria burhia, Boerhavia diffusa, Digera muricata, Pulicaria wightiana, Voluterella divaricata, Xanthium strumarium, Kylinga sp., Launea sp. and Indigofera cordifolia.
Type # 6. Halophytic Scrub Desert:
It is localized in low-lying saline basin and depressional areas. In these the soils are deep and highly saline. Saline flat areas are locally called “Rann” (playa). The surface layer of rann on drying is covered with a white crust of salt in the form of patches, which remain almost devoid of vegetation.
Some of the ranns in western Indian arid zone are Thob, Pokaran, Pachpadra, Lawana, Loonkaransar, Kharia, Malhar, Sonwarla and Uterlai. In these tracts the plants of Chenopodiaceae, Portulacaceae, Zygophyllaceae and Azoaceae families are prevalent.
The halophytic scrub communities recorded on various ranns (Playas) are:
1. Haloxylon salicornicum-Salsola baryosoma-Sporobolus marginatus,
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2. Suada fructicosa-Aeluropus lagopoides
3. Sporobolus helvolus-Cyperus rotundus.
4. Peganum harmala-Eleusine compressa-Sporobolus rnarginatus.
5. Demostachya bipinnata-Eleusine compressa.
Other common halophytic species of these communities are:
(1) Haloxylon recurveum, Atriplex sp.
(2) Zygophyllum simplex, Cressa cretica, Portulaca oleracea, Trian- thema portulacastrum, T. pentrandra, Mollugo loloides, Fagonia cretica, Euphorbia granulata and Sensuvium portulacastrum.
(3) Aeluropus lagopoides, Echinochloa colonum, Chloris virgata and Dichanthium, Dactyloctenium aegyptium and Schoenfeldia gracilis.
In some of the ranns sand deposition in the form of sand sheet have species of higher successional status, e.g., Lycium barbarum, Salvadora, oleoides, Acacia jacquemontii, Zizyphus nummularia and Tamarix aphylla.
Aquatic Habitat:
Reservoir retaining water throughout the year support good hydrophytic vegetation. The hydrophytes which are recorded from the lakes and reservoirs are Chara, Potamogeton, Najas, Vallisneria, Nymphea, Limnanthium, Lemna, Wolfia and Hydrilla etc.
The aquatic communities recorded are:
(1) Eic-chornia- Potamogeton
(2) Ceratophyllum – Vallisneria,
(3) Hydrilla-Vallisneria. In most of the lakes Trapa bispinosa is cultivated.
